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<div class="section" id="howto-programming-s-mime-in-python-with-m2crypto">
<span id="howto-smime"></span><h1>HOWTO: Programming S/MIME in Python with M2Crypto<a class="headerlink" href="#howto-programming-s-mime-in-python-with-m2crypto" title="Permalink to this headline">¶</a></h1>
<dl class="field-list simple">
<dt class="field-odd">author</dt>
<dd class="field-odd"><p>Pheng Siong Ng <<a class="reference external" href="mailto:ngps%40post1.com">ngps<span>@</span>post1<span>.</span>com</a>></p>
</dd>
<dt class="field-even">copyright</dt>
<dd class="field-even"><p>© 2000, 2001 by Ng Pheng Siong.</p>
</dd>
</dl>
</div>
<div class="section" id="introduction">
<h1>Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline">¶</a></h1>
<p><a class="reference external" href="https://gitlab.com/m2crypto/m2crypto/">M2Crypto</a> is a
<a class="reference external" href="http://www.python.org">Python</a> interface to
<a class="reference external" href="http://www.openssl.org">OpenSSL</a>. It makes available to the Python
programmer SSL functionality to implement clients and servers, S/MIME
v2, RSA, DSA, DH, symmetric ciphers, message digests and HMACs.</p>
<p>This document demonstrates programming S/MIME with M2Crypto.</p>
</div>
<div class="section" id="s-mime">
<h1>S/MIME<a class="headerlink" href="#s-mime" title="Permalink to this headline">¶</a></h1>
<p>S/MIME - Secure Multipurpose Internet Mail Extensions [RFC 2311, RFC
2312] - provides a consistent way to send and receive secure MIME data.
Based on the popular Internet MIME standard, S/MIME provides the
following cryptographic security services for electronic messaging
applications - <em>authentication</em>, <em>message integrity</em> and
<em>non-repudiation of origin</em> (using <em>digital signatures</em>), and <em>privacy</em>
and <em>data security</em> (using <em>encryption</em>).</p>
</div>
<div class="section" id="keys-and-certificates">
<h1>Keys and Certificates<a class="headerlink" href="#keys-and-certificates" title="Permalink to this headline">¶</a></h1>
<p>To create an S/MIME-signed message, you need an RSA key pair (this
consists of a public key and a private key) and an X.509 certificate of
said public key.</p>
<p>To create an S/MIME-encrypted message, you need an X.509 certificate for
each recipient.</p>
<p>To create an S/MIME-signed <em>and</em> -encrypted message, first create a
signed message, then encrypt the signed message with the recipients’
certificates.</p>
<p>You may generate key pairs and obtain certificates by using a commercial
<em>certification authority</em> service.</p>
<p>You can also do so using freely-available software. For many purposes,
e.g., automated S/MIME messaging by system administration processes,
this approach is cheap and effective.</p>
<p>We now work through using OpenSSL to generate key pairs and
certificates. This assumes you have OpenSSL installed properly on your
system.</p>
<p>First, we generate an X.509 certificate to be used for signing:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">openssl</span> <span class="n">req</span> <span class="o">-</span><span class="n">newkey</span> <span class="n">rsa</span><span class="p">:</span><span class="mi">1024</span> <span class="o">-</span><span class="n">nodes</span> <span class="o">-</span><span class="n">x509</span> <span class="o">-</span><span class="n">days</span> <span class="mi">365</span> <span class="o">-</span><span class="n">out</span> <span class="n">signer</span><span class="o">.</span><span class="n">pem</span>
<span class="n">Using</span> <span class="n">configuration</span> <span class="kn">from</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">pkg</span><span class="o">/</span><span class="n">openssl</span><span class="o">/</span><span class="n">openssl</span><span class="o">.</span><span class="n">cnf</span>
<span class="n">Generating</span> <span class="n">a</span> <span class="mi">1024</span> <span class="n">bit</span> <span class="n">RSA</span> <span class="n">private</span> <span class="n">key</span>
<span class="o">..++++++</span>
<span class="o">....................++++++</span>
<span class="n">writing</span> <span class="n">new</span> <span class="n">private</span> <span class="n">key</span> <span class="n">to</span> <span class="s1">'privkey.pem'</span>
<span class="o">-----</span>
<span class="n">You</span> <span class="n">are</span> <span class="n">about</span> <span class="n">to</span> <span class="n">be</span> <span class="n">asked</span> <span class="n">to</span> <span class="n">enter</span> <span class="n">information</span> <span class="n">that</span> <span class="n">will</span> <span class="n">be</span> <span class="n">incorporated</span>
<span class="n">into</span> <span class="n">your</span> <span class="n">certificate</span> <span class="n">request</span><span class="o">.</span>
<span class="n">What</span> <span class="n">you</span> <span class="n">are</span> <span class="n">about</span> <span class="n">to</span> <span class="n">enter</span> <span class="ow">is</span> <span class="n">what</span> <span class="ow">is</span> <span class="n">called</span> <span class="n">a</span> <span class="n">Distinguished</span> <span class="n">Name</span> <span class="ow">or</span> <span class="n">a</span> <span class="n">DN</span><span class="o">.</span>
<span class="n">There</span> <span class="n">are</span> <span class="n">quite</span> <span class="n">a</span> <span class="n">few</span> <span class="n">fields</span> <span class="n">but</span> <span class="n">you</span> <span class="n">can</span> <span class="n">leave</span> <span class="n">some</span> <span class="n">blank</span>
<span class="n">For</span> <span class="n">some</span> <span class="n">fields</span> <span class="n">there</span> <span class="n">will</span> <span class="n">be</span> <span class="n">a</span> <span class="n">default</span> <span class="n">value</span><span class="p">,</span>
<span class="n">If</span> <span class="n">you</span> <span class="n">enter</span> <span class="s1">'.'</span><span class="p">,</span> <span class="n">the</span> <span class="n">field</span> <span class="n">will</span> <span class="n">be</span> <span class="n">left</span> <span class="n">blank</span><span class="o">.</span>
<span class="o">-----</span>
<span class="n">Country</span> <span class="n">Name</span> <span class="p">(</span><span class="mi">2</span> <span class="n">letter</span> <span class="n">code</span><span class="p">)</span> <span class="p">[</span><span class="n">AU</span><span class="p">]:</span><span class="n">SG</span>
<span class="n">State</span> <span class="ow">or</span> <span class="n">Province</span> <span class="n">Name</span> <span class="p">(</span><span class="n">full</span> <span class="n">name</span><span class="p">)</span> <span class="p">[</span><span class="n">Some</span><span class="o">-</span><span class="n">State</span><span class="p">]:</span><span class="o">.</span>
<span class="n">Locality</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">city</span><span class="p">)</span> <span class="p">[]:</span><span class="o">.</span>
<span class="n">Organization</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">company</span><span class="p">)</span> <span class="p">[</span><span class="n">Internet</span> <span class="n">Widgits</span> <span class="n">Pty</span> <span class="n">Ltd</span><span class="p">]:</span><span class="n">M2Crypto</span>
<span class="n">Organizational</span> <span class="n">Unit</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">section</span><span class="p">)</span> <span class="p">[]:</span><span class="o">.</span>
<span class="n">Common</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">YOUR</span> <span class="n">name</span><span class="p">)</span> <span class="p">[]:</span><span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">Sender</span>
<span class="n">Email</span> <span class="n">Address</span> <span class="p">[]:</span><span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
</pre></div>
</div>
<p>This generates a 1024-bit RSA key pair, unencrypted, into
<code class="docutils literal notranslate"><span class="pre">privkey.pem</span></code>; it also generates a self-signed X.509 certificate for
the public key into <code class="docutils literal notranslate"><span class="pre">signer.pem</span></code>. The certificate is valid for 365
days, i.e., a year.</p>
<p>Let’s rename <code class="docutils literal notranslate"><span class="pre">privkey.pem</span></code> so that we know it is a companion of
<code class="docutils literal notranslate"><span class="pre">signer.pem</span></code>’s:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">mv</span> <span class="n">privkey</span><span class="o">.</span><span class="n">pem</span> <span class="n">signer_key</span><span class="o">.</span><span class="n">pem</span>
</pre></div>
</div>
<p>To verify the content of <code class="docutils literal notranslate"><span class="pre">signer.pem</span></code>, execute the following:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">openssl</span> <span class="n">x509</span> <span class="o">-</span><span class="n">noout</span> <span class="o">-</span><span class="n">text</span> <span class="o">-</span><span class="ow">in</span> <span class="n">signer</span><span class="o">.</span><span class="n">pem</span>
<span class="n">Certificate</span><span class="p">:</span>
<span class="n">Data</span><span class="p">:</span>
<span class="n">Version</span><span class="p">:</span> <span class="mi">3</span> <span class="p">(</span><span class="mh">0x2</span><span class="p">)</span>
<span class="n">Serial</span> <span class="n">Number</span><span class="p">:</span> <span class="mi">0</span> <span class="p">(</span><span class="mh">0x0</span><span class="p">)</span>
<span class="n">Signature</span> <span class="n">Algorithm</span><span class="p">:</span> <span class="n">md5WithRSAEncryption</span>
<span class="n">Issuer</span><span class="p">:</span> <span class="n">C</span><span class="o">=</span><span class="n">SG</span><span class="p">,</span> <span class="n">O</span><span class="o">=</span><span class="n">M2Crypto</span><span class="p">,</span> <span class="n">CN</span><span class="o">=</span><span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">Sender</span><span class="o">/</span><span class="n">Email</span><span class="o">=</span><span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">Validity</span>
<span class="n">Not</span> <span class="n">Before</span><span class="p">:</span> <span class="n">Mar</span> <span class="mi">24</span> <span class="mi">12</span><span class="p">:</span><span class="mi">56</span><span class="p">:</span><span class="mi">16</span> <span class="mi">2001</span> <span class="n">GMT</span>
<span class="n">Not</span> <span class="n">After</span> <span class="p">:</span> <span class="n">Mar</span> <span class="mi">24</span> <span class="mi">12</span><span class="p">:</span><span class="mi">56</span><span class="p">:</span><span class="mi">16</span> <span class="mi">2002</span> <span class="n">GMT</span>
<span class="n">Subject</span><span class="p">:</span> <span class="n">C</span><span class="o">=</span><span class="n">SG</span><span class="p">,</span> <span class="n">O</span><span class="o">=</span><span class="n">M2Crypto</span><span class="p">,</span> <span class="n">CN</span><span class="o">=</span><span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">Sender</span><span class="o">/</span><span class="n">Email</span><span class="o">=</span><span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">Subject</span> <span class="n">Public</span> <span class="n">Key</span> <span class="n">Info</span><span class="p">:</span>
<span class="n">Public</span> <span class="n">Key</span> <span class="n">Algorithm</span><span class="p">:</span> <span class="n">rsaEncryption</span>
<span class="n">RSA</span> <span class="n">Public</span> <span class="n">Key</span><span class="p">:</span> <span class="p">(</span><span class="mi">1024</span> <span class="n">bit</span><span class="p">)</span>
<span class="n">Modulus</span> <span class="p">(</span><span class="mi">1024</span> <span class="n">bit</span><span class="p">):</span>
<span class="mi">00</span><span class="p">:</span><span class="n">a9</span><span class="p">:</span><span class="n">d6</span><span class="p">:</span><span class="n">e2</span><span class="p">:</span><span class="n">b5</span><span class="p">:</span><span class="mi">11</span><span class="p">:</span><span class="mi">3</span><span class="n">b</span><span class="p">:</span><span class="n">ae</span><span class="p">:</span><span class="mi">3</span><span class="n">c</span><span class="p">:</span><span class="n">e2</span><span class="p">:</span><span class="mi">17</span><span class="p">:</span><span class="mi">31</span><span class="p">:</span><span class="mi">70</span><span class="p">:</span><span class="n">e1</span><span class="p">:</span><span class="mi">6</span><span class="n">e</span><span class="p">:</span>
<span class="mi">01</span><span class="p">:</span><span class="n">f4</span><span class="p">:</span><span class="mi">19</span><span class="p">:</span><span class="mi">6</span><span class="n">d</span><span class="p">:</span><span class="n">bd</span><span class="p">:</span><span class="mi">2</span><span class="n">a</span><span class="p">:</span><span class="mi">42</span><span class="p">:</span><span class="mi">36</span><span class="p">:</span><span class="mi">2</span><span class="n">b</span><span class="p">:</span><span class="mi">37</span><span class="p">:</span><span class="mi">34</span><span class="p">:</span><span class="n">e2</span><span class="p">:</span><span class="mi">83</span><span class="p">:</span><span class="mi">1</span><span class="n">d</span><span class="p">:</span><span class="mi">0</span><span class="n">d</span><span class="p">:</span>
<span class="mi">11</span><span class="p">:</span><span class="mi">2</span><span class="n">e</span><span class="p">:</span><span class="n">b4</span><span class="p">:</span><span class="mi">99</span><span class="p">:</span><span class="mi">44</span><span class="p">:</span><span class="n">db</span><span class="p">:</span><span class="mi">10</span><span class="p">:</span><span class="mi">67</span><span class="p">:</span><span class="n">be</span><span class="p">:</span><span class="mi">97</span><span class="p">:</span><span class="mi">5</span><span class="n">f</span><span class="p">:</span><span class="mi">5</span><span class="n">b</span><span class="p">:</span><span class="mi">1</span><span class="n">a</span><span class="p">:</span><span class="mi">26</span><span class="p">:</span><span class="mi">33</span><span class="p">:</span>
<span class="mi">46</span><span class="p">:</span><span class="mi">23</span><span class="p">:</span><span class="mi">2</span><span class="n">f</span><span class="p">:</span><span class="mi">95</span><span class="p">:</span><span class="mi">04</span><span class="p">:</span><span class="mi">7</span><span class="n">a</span><span class="p">:</span><span class="mi">35</span><span class="p">:</span><span class="n">da</span><span class="p">:</span><span class="mi">9</span><span class="n">d</span><span class="p">:</span><span class="n">f9</span><span class="p">:</span><span class="mi">26</span><span class="p">:</span><span class="mi">88</span><span class="p">:</span><span class="mi">39</span><span class="p">:</span><span class="mi">9</span><span class="n">e</span><span class="p">:</span><span class="mi">17</span><span class="p">:</span>
<span class="n">cd</span><span class="p">:</span><span class="mi">3</span><span class="n">e</span><span class="p">:</span><span class="n">eb</span><span class="p">:</span><span class="n">a8</span><span class="p">:</span><span class="mi">19</span><span class="p">:</span><span class="mi">8</span><span class="n">d</span><span class="p">:</span><span class="n">a8</span><span class="p">:</span><span class="mi">2</span><span class="n">a</span><span class="p">:</span><span class="n">f1</span><span class="p">:</span><span class="mi">43</span><span class="p">:</span><span class="n">da</span><span class="p">:</span><span class="mi">55</span><span class="p">:</span><span class="n">a9</span><span class="p">:</span><span class="mi">2</span><span class="n">e</span><span class="p">:</span><span class="mi">2</span><span class="n">c</span><span class="p">:</span>
<span class="mi">65</span><span class="p">:</span><span class="n">ed</span><span class="p">:</span><span class="mi">04</span><span class="p">:</span><span class="mi">71</span><span class="p">:</span><span class="mi">42</span><span class="p">:</span><span class="n">ce</span><span class="p">:</span><span class="mi">73</span><span class="p">:</span><span class="mi">53</span><span class="p">:</span><span class="n">b8</span><span class="p">:</span><span class="n">ea</span><span class="p">:</span><span class="mi">7</span><span class="n">e</span><span class="p">:</span><span class="n">c7</span><span class="p">:</span><span class="n">f0</span><span class="p">:</span><span class="mi">23</span><span class="p">:</span><span class="n">c6</span><span class="p">:</span>
<span class="mi">63</span><span class="p">:</span><span class="n">c5</span><span class="p">:</span><span class="mi">5</span><span class="n">e</span><span class="p">:</span><span class="mi">68</span><span class="p">:</span><span class="mi">96</span><span class="p">:</span><span class="mi">64</span><span class="p">:</span><span class="n">a7</span><span class="p">:</span><span class="n">b4</span><span class="p">:</span><span class="mi">2</span><span class="n">a</span><span class="p">:</span><span class="mi">94</span><span class="p">:</span><span class="mi">26</span><span class="p">:</span><span class="mi">76</span><span class="p">:</span><span class="n">eb</span><span class="p">:</span><span class="mi">79</span><span class="p">:</span><span class="n">ea</span><span class="p">:</span>
<span class="n">e3</span><span class="p">:</span><span class="mi">4</span><span class="n">e</span><span class="p">:</span><span class="n">aa</span><span class="p">:</span><span class="mi">82</span><span class="p">:</span><span class="mi">09</span><span class="p">:</span><span class="mi">4</span><span class="n">f</span><span class="p">:</span><span class="mi">44</span><span class="p">:</span><span class="mi">87</span><span class="p">:</span><span class="mi">4</span><span class="n">a</span><span class="p">:</span><span class="mi">12</span><span class="p">:</span><span class="mi">62</span><span class="p">:</span><span class="n">b5</span><span class="p">:</span><span class="n">d7</span><span class="p">:</span><span class="mi">1</span><span class="n">f</span><span class="p">:</span><span class="n">ca</span><span class="p">:</span>
<span class="n">f2</span><span class="p">:</span><span class="n">ce</span><span class="p">:</span><span class="n">d5</span><span class="p">:</span><span class="n">ba</span><span class="p">:</span><span class="mi">7</span><span class="n">e</span><span class="p">:</span><span class="mi">1</span><span class="n">f</span><span class="p">:</span><span class="mi">48</span><span class="p">:</span><span class="n">fd</span><span class="p">:</span><span class="n">b9</span>
<span class="n">Exponent</span><span class="p">:</span> <span class="mi">65537</span> <span class="p">(</span><span class="mh">0x10001</span><span class="p">)</span>
<span class="n">X509v3</span> <span class="n">extensions</span><span class="p">:</span>
<span class="n">X509v3</span> <span class="n">Subject</span> <span class="n">Key</span> <span class="n">Identifier</span><span class="p">:</span>
<span class="mi">29</span><span class="p">:</span><span class="n">FB</span><span class="p">:</span><span class="mi">38</span><span class="p">:</span><span class="n">B6</span><span class="p">:</span><span class="n">BF</span><span class="p">:</span><span class="n">E2</span><span class="p">:</span><span class="mi">40</span><span class="p">:</span><span class="n">BB</span><span class="p">:</span><span class="n">FF</span><span class="p">:</span><span class="n">D5</span><span class="p">:</span><span class="mi">71</span><span class="p">:</span><span class="n">D7</span><span class="p">:</span><span class="n">D5</span><span class="p">:</span><span class="n">C4</span><span class="p">:</span><span class="n">F0</span><span class="p">:</span><span class="mi">83</span><span class="p">:</span><span class="mi">1</span><span class="n">A</span><span class="p">:</span><span class="mi">2</span><span class="n">B</span><span class="p">:</span><span class="n">C7</span><span class="p">:</span><span class="mi">99</span>
<span class="n">X509v3</span> <span class="n">Authority</span> <span class="n">Key</span> <span class="n">Identifier</span><span class="p">:</span>
<span class="n">keyid</span><span class="p">:</span><span class="mi">29</span><span class="p">:</span><span class="n">FB</span><span class="p">:</span><span class="mi">38</span><span class="p">:</span><span class="n">B6</span><span class="p">:</span><span class="n">BF</span><span class="p">:</span><span class="n">E2</span><span class="p">:</span><span class="mi">40</span><span class="p">:</span><span class="n">BB</span><span class="p">:</span><span class="n">FF</span><span class="p">:</span><span class="n">D5</span><span class="p">:</span><span class="mi">71</span><span class="p">:</span><span class="n">D7</span><span class="p">:</span><span class="n">D5</span><span class="p">:</span><span class="n">C4</span><span class="p">:</span><span class="n">F0</span><span class="p">:</span><span class="mi">83</span><span class="p">:</span><span class="mi">1</span><span class="n">A</span><span class="p">:</span><span class="mi">2</span><span class="n">B</span><span class="p">:</span><span class="n">C7</span><span class="p">:</span><span class="mi">99</span>
<span class="n">DirName</span><span class="p">:</span><span class="o">/</span><span class="n">C</span><span class="o">=</span><span class="n">SG</span><span class="o">/</span><span class="n">O</span><span class="o">=</span><span class="n">M2Crypto</span><span class="o">/</span><span class="n">CN</span><span class="o">=</span><span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">Sender</span><span class="o">/</span><span class="n">Email</span><span class="o">=</span><span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">serial</span><span class="p">:</span><span class="mi">00</span>
<span class="n">X509v3</span> <span class="n">Basic</span> <span class="n">Constraints</span><span class="p">:</span>
<span class="n">CA</span><span class="p">:</span><span class="n">TRUE</span>
<span class="n">Signature</span> <span class="n">Algorithm</span><span class="p">:</span> <span class="n">md5WithRSAEncryption</span>
<span class="mi">68</span><span class="p">:</span><span class="n">c8</span><span class="p">:</span><span class="mi">6</span><span class="n">b</span><span class="p">:</span><span class="mi">1</span><span class="n">b</span><span class="p">:</span><span class="n">fa</span><span class="p">:</span><span class="mi">7</span><span class="n">c</span><span class="p">:</span><span class="mi">9</span><span class="n">a</span><span class="p">:</span><span class="mi">39</span><span class="p">:</span><span class="mi">35</span><span class="p">:</span><span class="mi">76</span><span class="p">:</span><span class="mi">18</span><span class="p">:</span><span class="mi">15</span><span class="p">:</span><span class="n">c9</span><span class="p">:</span><span class="n">fd</span><span class="p">:</span><span class="mi">89</span><span class="p">:</span><span class="mi">97</span><span class="p">:</span><span class="mi">62</span><span class="p">:</span><span class="n">db</span><span class="p">:</span>
<span class="mi">7</span><span class="n">a</span><span class="p">:</span><span class="n">b0</span><span class="p">:</span><span class="mi">2</span><span class="n">d</span><span class="p">:</span><span class="mi">13</span><span class="p">:</span><span class="n">dd</span><span class="p">:</span><span class="mi">97</span><span class="p">:</span><span class="n">e8</span><span class="p">:</span><span class="mi">1</span><span class="n">b</span><span class="p">:</span><span class="mi">7</span><span class="n">a</span><span class="p">:</span><span class="mi">9</span><span class="n">f</span><span class="p">:</span><span class="mi">22</span><span class="p">:</span><span class="mi">27</span><span class="p">:</span><span class="mi">83</span><span class="p">:</span><span class="mi">24</span><span class="p">:</span><span class="mi">9</span><span class="n">d</span><span class="p">:</span><span class="mi">2</span><span class="n">e</span><span class="p">:</span><span class="mi">56</span><span class="p">:</span><span class="n">ec</span><span class="p">:</span>
<span class="mi">97</span><span class="p">:</span><span class="mi">89</span><span class="p">:</span><span class="mi">3</span><span class="n">c</span><span class="p">:</span><span class="n">ef</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">55</span><span class="p">:</span><span class="mi">80</span><span class="p">:</span><span class="mi">5</span><span class="n">a</span><span class="p">:</span><span class="mi">18</span><span class="p">:</span><span class="mi">7</span><span class="n">c</span><span class="p">:</span><span class="mi">22</span><span class="p">:</span><span class="n">d0</span><span class="p">:</span><span class="n">f6</span><span class="p">:</span><span class="n">bb</span><span class="p">:</span><span class="n">e3</span><span class="p">:</span><span class="n">a4</span><span class="p">:</span><span class="n">e8</span><span class="p">:</span><span class="mi">59</span><span class="p">:</span>
<span class="mi">30</span><span class="p">:</span><span class="n">ff</span><span class="p">:</span><span class="mi">99</span><span class="p">:</span><span class="mi">5</span><span class="n">a</span><span class="p">:</span><span class="mi">93</span><span class="p">:</span><span class="mi">3</span><span class="n">e</span><span class="p">:</span><span class="n">ea</span><span class="p">:</span><span class="n">bc</span><span class="p">:</span><span class="n">ee</span><span class="p">:</span><span class="mi">7</span><span class="n">f</span><span class="p">:</span><span class="mi">8</span><span class="n">d</span><span class="p">:</span><span class="n">d6</span><span class="p">:</span><span class="mi">7</span><span class="n">d</span><span class="p">:</span><span class="mi">37</span><span class="p">:</span><span class="mi">8</span><span class="n">c</span><span class="p">:</span><span class="n">ac</span><span class="p">:</span><span class="mi">3</span><span class="n">d</span><span class="p">:</span><span class="mi">74</span><span class="p">:</span>
<span class="mi">80</span><span class="p">:</span><span class="n">ce</span><span class="p">:</span><span class="mi">7</span><span class="n">a</span><span class="p">:</span><span class="mi">99</span><span class="p">:</span><span class="n">ba</span><span class="p">:</span><span class="mi">27</span><span class="p">:</span><span class="n">b9</span><span class="p">:</span><span class="mi">2</span><span class="n">a</span><span class="p">:</span><span class="n">a3</span><span class="p">:</span><span class="mi">71</span><span class="p">:</span><span class="n">fa</span><span class="p">:</span><span class="n">a5</span><span class="p">:</span><span class="mi">25</span><span class="p">:</span><span class="n">ba</span><span class="p">:</span><span class="mi">47</span><span class="p">:</span><span class="mi">17</span><span class="p">:</span><span class="n">df</span><span class="p">:</span><span class="mi">07</span><span class="p">:</span>
<span class="mi">56</span><span class="p">:</span><span class="mi">96</span><span class="p">:</span><span class="mi">36</span><span class="p">:</span><span class="n">fd</span><span class="p">:</span><span class="mi">60</span><span class="p">:</span><span class="n">b9</span><span class="p">:</span><span class="mi">6</span><span class="n">c</span><span class="p">:</span><span class="mi">96</span><span class="p">:</span><span class="mi">06</span><span class="p">:</span><span class="n">e8</span><span class="p">:</span><span class="n">e3</span><span class="p">:</span><span class="mi">7</span><span class="n">b</span><span class="p">:</span><span class="mi">9</span><span class="n">f</span><span class="p">:</span><span class="mi">4</span><span class="n">b</span><span class="p">:</span><span class="mi">6</span><span class="n">a</span><span class="p">:</span><span class="mi">95</span><span class="p">:</span><span class="mi">71</span><span class="p">:</span><span class="n">a8</span><span class="p">:</span>
<span class="mi">34</span><span class="p">:</span><span class="n">fc</span><span class="p">:</span><span class="n">fc</span><span class="p">:</span><span class="n">b5</span><span class="p">:</span><span class="mi">88</span><span class="p">:</span><span class="mi">8</span><span class="n">b</span><span class="p">:</span><span class="n">c4</span><span class="p">:</span><span class="mi">3</span><span class="n">f</span><span class="p">:</span><span class="mi">1</span><span class="n">e</span><span class="p">:</span><span class="mi">24</span><span class="p">:</span><span class="n">f6</span><span class="p">:</span><span class="mi">52</span><span class="p">:</span><span class="mi">47</span><span class="p">:</span><span class="n">b2</span><span class="p">:</span><span class="mi">7</span><span class="n">d</span><span class="p">:</span><span class="mi">44</span><span class="p">:</span><span class="mi">67</span><span class="p">:</span><span class="n">d9</span><span class="p">:</span>
<span class="mi">83</span><span class="p">:</span><span class="n">e8</span>
</pre></div>
</div>
<p>Next, we generate a self-signed X.509 certificate for the recipient.
Note that <code class="docutils literal notranslate"><span class="pre">privkey.pem</span></code> will be recreated:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">openssl</span> <span class="n">req</span> <span class="o">-</span><span class="n">newkey</span> <span class="n">rsa</span><span class="p">:</span><span class="mi">1024</span> <span class="o">-</span><span class="n">nodes</span> <span class="o">-</span><span class="n">x509</span> <span class="o">-</span><span class="n">days</span> <span class="mi">365</span> <span class="o">-</span><span class="n">out</span> <span class="n">recipient</span><span class="o">.</span><span class="n">pem</span>
<span class="n">Using</span> <span class="n">configuration</span> <span class="kn">from</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">pkg</span><span class="o">/</span><span class="n">openssl</span><span class="o">/</span><span class="n">openssl</span><span class="o">.</span><span class="n">cnf</span>
<span class="n">Generating</span> <span class="n">a</span> <span class="mi">1024</span> <span class="n">bit</span> <span class="n">RSA</span> <span class="n">private</span> <span class="n">key</span>
<span class="o">.....................................++++++</span>
<span class="o">.................++++++</span>
<span class="n">writing</span> <span class="n">new</span> <span class="n">private</span> <span class="n">key</span> <span class="n">to</span> <span class="s1">'privkey.pem'</span>
<span class="o">-----</span>
<span class="n">You</span> <span class="n">are</span> <span class="n">about</span> <span class="n">to</span> <span class="n">be</span> <span class="n">asked</span> <span class="n">to</span> <span class="n">enter</span> <span class="n">information</span> <span class="n">that</span> <span class="n">will</span> <span class="n">be</span> <span class="n">incorporated</span>
<span class="n">into</span> <span class="n">your</span> <span class="n">certificate</span> <span class="n">request</span><span class="o">.</span>
<span class="n">What</span> <span class="n">you</span> <span class="n">are</span> <span class="n">about</span> <span class="n">to</span> <span class="n">enter</span> <span class="ow">is</span> <span class="n">what</span> <span class="ow">is</span> <span class="n">called</span> <span class="n">a</span> <span class="n">Distinguished</span> <span class="n">Name</span> <span class="ow">or</span> <span class="n">a</span> <span class="n">DN</span><span class="o">.</span>
<span class="n">There</span> <span class="n">are</span> <span class="n">quite</span> <span class="n">a</span> <span class="n">few</span> <span class="n">fields</span> <span class="n">but</span> <span class="n">you</span> <span class="n">can</span> <span class="n">leave</span> <span class="n">some</span> <span class="n">blank</span>
<span class="n">For</span> <span class="n">some</span> <span class="n">fields</span> <span class="n">there</span> <span class="n">will</span> <span class="n">be</span> <span class="n">a</span> <span class="n">default</span> <span class="n">value</span><span class="p">,</span>
<span class="n">If</span> <span class="n">you</span> <span class="n">enter</span> <span class="s1">'.'</span><span class="p">,</span> <span class="n">the</span> <span class="n">field</span> <span class="n">will</span> <span class="n">be</span> <span class="n">left</span> <span class="n">blank</span><span class="o">.</span>
<span class="o">-----</span>
<span class="n">Country</span> <span class="n">Name</span> <span class="p">(</span><span class="mi">2</span> <span class="n">letter</span> <span class="n">code</span><span class="p">)</span> <span class="p">[</span><span class="n">AU</span><span class="p">]:</span><span class="n">SG</span>
<span class="n">State</span> <span class="ow">or</span> <span class="n">Province</span> <span class="n">Name</span> <span class="p">(</span><span class="n">full</span> <span class="n">name</span><span class="p">)</span> <span class="p">[</span><span class="n">Some</span><span class="o">-</span><span class="n">State</span><span class="p">]:</span><span class="o">.</span>
<span class="n">Locality</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">city</span><span class="p">)</span> <span class="p">[]:</span><span class="o">.</span>
<span class="n">Organization</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">company</span><span class="p">)</span> <span class="p">[</span><span class="n">Internet</span> <span class="n">Widgits</span> <span class="n">Pty</span> <span class="n">Ltd</span><span class="p">]:</span><span class="n">M2Crypto</span>
<span class="n">Organizational</span> <span class="n">Unit</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">section</span><span class="p">)</span> <span class="p">[]:</span><span class="o">.</span>
<span class="n">Common</span> <span class="n">Name</span> <span class="p">(</span><span class="n">eg</span><span class="p">,</span> <span class="n">YOUR</span> <span class="n">name</span><span class="p">)</span> <span class="p">[]:</span><span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">Recipient</span>
<span class="n">Email</span> <span class="n">Address</span> <span class="p">[]:</span><span class="n">recipient</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
</pre></div>
</div>
<p>Again, rename <code class="docutils literal notranslate"><span class="pre">privkey.pem</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">mv</span> <span class="n">privkey</span><span class="o">.</span><span class="n">pem</span> <span class="n">recipient_key</span><span class="o">.</span><span class="n">pem</span>
</pre></div>
</div>
<p>In the examples to follow, S/MIME Sender, <code class="docutils literal notranslate"><span class="pre"><sender@example.dom></span></code>,
shall be the sender of S/MIME messages, while S/MIME Recipient,
<code class="docutils literal notranslate"><span class="pre"><recipient@example.dom></span></code>, shall be the recipient of S/MIME messages.</p>
<p>Armed with the key pairs and certificates, we are now ready to begin
programming S/MIME in Python.</p>
<blockquote>
<div><p><strong>Note:</strong> The private keys generated above are <em>not
passphrase-protected</em>, i.e., they are <em>in the clear</em>. Anyone who has
access to such a key can generate S/MIME-signed messages with it,
and decrypt S/MIME messages encrypted to it’s corresponding public
key.</p>
<p>We may passphrase-protect the keys, if we so choose. M2Crypto will
prompt the user for the passphrase when such a key is being loaded.</p>
</div></blockquote>
</div>
<div class="section" id="m2crypto-smime">
<h1>M2Crypto.SMIME<a class="headerlink" href="#m2crypto-smime" title="Permalink to this headline">¶</a></h1>
<p>The Python programmer accesses M2Crypto’s S/MIME functionality through
class <code class="docutils literal notranslate"><span class="pre">SMIME</span></code> in the module <code class="docutils literal notranslate"><span class="pre">M2Crypto.SMIME</span></code>. Typically, an
<code class="docutils literal notranslate"><span class="pre">SMIME</span></code> object is instantiated; the object is then set up for the
intended operation: sign, encrypt, decrypt or verify; finally, the
operation is invoked on the object.</p>
<p><code class="docutils literal notranslate"><span class="pre">M2Crypto.SMIME</span></code> makes extensive use of <code class="docutils literal notranslate"><span class="pre">M2Crypto.BIO</span></code>:
<code class="docutils literal notranslate"><span class="pre">M2Crypto.BIO</span></code> is a Python abstraction of the <code class="docutils literal notranslate"><span class="pre">BIO</span></code> abstraction in
OpenSSL. A commonly used <code class="docutils literal notranslate"><span class="pre">BIO</span></code> abstraction in M2Crypto is
<code class="docutils literal notranslate"><span class="pre">M2Crypto.BIO.MemoryBuffer</span></code>, which implements a memory-based file-like
object, similar to Python’s own <code class="docutils literal notranslate"><span class="pre">StringIO</span></code>.</p>
</div>
<div class="section" id="sign">
<h1>Sign<a class="headerlink" href="#sign" title="Permalink to this headline">¶</a></h1>
<p>The following code demonstrates how to generate an S/MIME-signed
message. <code class="docutils literal notranslate"><span class="pre">randpool.dat</span></code> contains random data which is used to seed
OpenSSL’s pseudo-random number generator via M2Crypto:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">BIO</span><span class="p">,</span> <span class="n">Rand</span><span class="p">,</span> <span class="n">SMIME</span>
<span class="k">def</span> <span class="nf">makebuf</span><span class="p">(</span><span class="n">text</span><span class="p">):</span>
<span class="k">return</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">(</span><span class="n">text</span><span class="p">)</span>
<span class="c1"># Make a MemoryBuffer of the message.</span>
<span class="n">buf</span> <span class="o">=</span> <span class="n">makebuf</span><span class="p">(</span><span class="s1">'a sign of our times'</span><span class="p">)</span>
<span class="c1"># Seed the PRNG.</span>
<span class="n">Rand</span><span class="o">.</span><span class="n">load_file</span><span class="p">(</span><span class="s1">'randpool.dat'</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">)</span>
<span class="c1"># Instantiate an SMIME object; set it up; sign the buffer.</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="n">s</span><span class="o">.</span><span class="n">load_key</span><span class="p">(</span><span class="s1">'signer_key.pem'</span><span class="p">,</span> <span class="s1">'signer.pem'</span><span class="p">)</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">PKCS7_DETACHED</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">p7</span></code> now contains a <em>PKCS #7 signature blob</em> wrapped in an
<code class="docutils literal notranslate"><span class="pre">M2Crypto.SMIME.PKCS7</span></code> object. Note that <code class="docutils literal notranslate"><span class="pre">buf</span></code> has been consumed by
<code class="docutils literal notranslate"><span class="pre">sign()</span></code> and has to be recreated if it is to be used again.</p>
<p>We may now send the signed message via SMTP. In these examples, we shall
not do so; instead, we’ll render the S/MIME output in mail-friendly
format, and pretend that our messages are sent and received
correctly:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># Recreate buf.</span>
<span class="n">buf</span> <span class="o">=</span> <span class="n">makebuf</span><span class="p">(</span><span class="s1">'a sign of our times'</span><span class="p">)</span>
<span class="c1"># Output p7 in mail-friendly format.</span>
<span class="n">out</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">()</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'From: sender@example.dom</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'To: recipient@example.dom</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'Subject: M2Crypto S/MIME testing</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">out</span><span class="p">,</span> <span class="n">p7</span><span class="p">,</span> <span class="n">buf</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">out</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
<span class="c1"># Save the PRNG's state.</span>
<span class="n">Rand</span><span class="o">.</span><span class="n">save_file</span><span class="p">(</span><span class="s1">'randpool.dat'</span><span class="p">)</span>
</pre></div>
</div>
<p>Here’s the output:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">From</span><span class="p">:</span> <span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">To</span><span class="p">:</span> <span class="n">recipient</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">Subject</span><span class="p">:</span> <span class="n">M2Crypto</span> <span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">testing</span>
<span class="n">MIME</span><span class="o">-</span><span class="n">Version</span><span class="p">:</span> <span class="mf">1.0</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">multipart</span><span class="o">/</span><span class="n">signed</span> <span class="p">;</span> <span class="n">protocol</span><span class="o">=</span><span class="s2">"application/x-pkcs7-signature"</span> <span class="p">;</span> <span class="n">micalg</span><span class="o">=</span><span class="n">sha1</span> <span class="p">;</span> <span class="n">boundary</span><span class="o">=</span><span class="s2">"----3C93156FC7B4EBF49FE9C7DB7F503087"</span>
<span class="n">This</span> <span class="ow">is</span> <span class="n">an</span> <span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">signed</span> <span class="n">message</span>
<span class="o">------</span><span class="mi">3</span><span class="n">C93156FC7B4EBF49FE9C7DB7F503087</span>
<span class="n">a</span> <span class="n">sign</span> <span class="n">of</span> <span class="n">our</span> <span class="n">times</span>
<span class="o">------</span><span class="mi">3</span><span class="n">C93156FC7B4EBF49FE9C7DB7F503087</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">x</span><span class="o">-</span><span class="n">pkcs7</span><span class="o">-</span><span class="n">signature</span><span class="p">;</span> <span class="n">name</span><span class="o">=</span><span class="s2">"smime.p7s"</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Transfer</span><span class="o">-</span><span class="n">Encoding</span><span class="p">:</span> <span class="n">base64</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Disposition</span><span class="p">:</span> <span class="n">attachment</span><span class="p">;</span> <span class="n">filename</span><span class="o">=</span><span class="s2">"smime.p7s"</span>
<span class="n">MIIE8AYJKoZIhvcNAQcCoIIE4TCCBN0CAQExCzAJBgUrDgMCGgUAMCIGCSqGSIb3</span>
<span class="n">DQEHAaAVBBNhIHNpZ24gb2Ygb3VyIHRpbWVzoIIC5zCCAuMwggJMoAMCAQICAQAw</span>
<span class="n">DQYJKoZIhvcNAQEEBQAwWzELMAkGA1UEBhMCU0cxETAPBgNVBAoTCE0yQ3J5cHRv</span>
<span class="n">MRYwFAYDVQQDEw1TL01JTUUgU2VuZGVyMSEwHwYJKoZIhvcNAQkBFhJzZW5kZXJA</span>
<span class="n">ZXhhbXBsZS5kb20wHhcNMDEwMzMxMTE0MDMzWhcNMDIwMzMxMTE0MDMzWjBbMQsw</span>
<span class="n">CQYDVQQGEwJTRzERMA8GA1UEChMITTJDcnlwdG8xFjAUBgNVBAMTDVMvTUlNRSBT</span>
<span class="n">ZW5kZXIxITAfBgkqhkiG9w0BCQEWEnNlbmRlckBleGFtcGxlLmRvbTCBnzANBgkq</span>
<span class="n">hkiG9w0BAQEFAAOBjQAwgYkCgYEA5c5Tj1CHTSOxa1q2q0FYiwMWYHptJpJcvtZm</span>
<span class="n">UwrgU5sHrA8OnCM0cDXEj0KPf3cfNjHffB8HWMzI4UEgNmFXQNsxoGZ</span><span class="o">+</span><span class="n">iqwxLlNj</span>
<span class="n">y9Mh7eFW</span><span class="o">/</span><span class="n">Bjq5hNXbouSlQ0rWBRkoxV64y</span><span class="o">+</span><span class="n">t6lQehb32WfYXQbKFxFJSXzSxOx3R</span>
<span class="mi">8</span><span class="n">YhSPd0CAwEAAaOBtjCBszAdBgNVHQ4EFgQUXOyolL1t4jaBwZFRM7MS8nBLzUow</span>
<span class="n">gYMGA1UdIwR8MHqAFFzsqJS9beI2gcGRUTOzEvJwS81KoV</span><span class="o">+</span><span class="n">kXTBbMQswCQYDVQQG</span>
<span class="n">EwJTRzERMA8GA1UEChMITTJDcnlwdG8xFjAUBgNVBAMTDVMvTUlNRSBTZW5kZXIx</span>
<span class="n">ITAfBgkqhkiG9w0BCQEWEnNlbmRlckBleGFtcGxlLmRvbYIBADAMBgNVHRMEBTAD</span>
<span class="n">AQH</span><span class="o">/</span><span class="n">MA0GCSqGSIb3DQEBBAUAA4GBAHo3DrCHR86fSTVAvfiXdSswWqKtCEhUHRdC</span>
<span class="n">TLFGl4hDk2GyZxaFuqZwiURz</span><span class="o">/</span><span class="n">H7nMicymI2wkz8H</span><span class="o">/</span><span class="n">wyHFg8G3BIehURpj2v</span><span class="o">/</span><span class="n">ZWXY</span>
<span class="n">eovbgS7EZALVVkDj4hNl</span><span class="o">/</span><span class="n">IIHWd6Gtv1UODf7URbxtl3hQ9</span><span class="o">/</span><span class="n">eTWITrefT1heuPnar</span>
<span class="mi">8</span><span class="n">czydsOLMYIBujCCAbYCAQEwYDBbMQswCQYDVQQGEwJTRzERMA8GA1UEChMITTJD</span>
<span class="n">cnlwdG8xFjAUBgNVBAMTDVMvTUlNRSBTZW5kZXIxITAfBgkqhkiG9w0BCQEWEnNl</span>
<span class="n">bmRlckBleGFtcGxlLmRvbQIBADAJBgUrDgMCGgUAoIGxMBgGCSqGSIb3DQEJAzEL</span>
<span class="n">BgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTAxMDMzMTExNDUwMlowIwYJKoZI</span>
<span class="n">hvcNAQkEMRYEFOoeRUd8ExIYXfQq8BTFuKWrSP3iMFIGCSqGSIb3DQEJDzFFMEMw</span>
<span class="n">CgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFAMAcGBSsO</span>
<span class="n">AwIHMA0GCCqGSIb3DQMCAgEoMA0GCSqGSIb3DQEBAQUABIGAQpU8hFUtLCF6hO2t</span>
<span class="n">ec9EYJ</span><span class="o">/</span><span class="n">Imqqiiw</span><span class="o">+</span><span class="n">BxWxkUUVT81Vbjwdn9JST6</span><span class="o">+</span><span class="n">sztM5JRP2ZW</span><span class="o">+</span><span class="n">b4txEjZriYC8f3</span>
<span class="n">kv95YMTGbIsuWkJ93GrbvqoJ</span><span class="o">/</span><span class="n">CxO23r9WWRnZEm</span><span class="o">/</span><span class="mi">1</span><span class="n">EZN9ZmlrYqzBTxnNRmP3Dhj</span>
<span class="n">cW8kzZwH</span><span class="o">+</span><span class="mi">2</span><span class="o">/</span><span class="mi">2</span><span class="n">zz2G7x1HxRWH95A</span><span class="o">=</span>
<span class="o">------</span><span class="mi">3</span><span class="n">C93156FC7B4EBF49FE9C7DB7F503087</span><span class="o">--</span>
</pre></div>
</div>
</div>
<div class="section" id="verify">
<h1>Verify<a class="headerlink" href="#verify" title="Permalink to this headline">¶</a></h1>
<p>Assume the above output has been saved into <code class="docutils literal notranslate"><span class="pre">sign.p7</span></code>. Let’s now
verify the signature:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">SMIME</span><span class="p">,</span> <span class="n">X509</span>
<span class="c1"># Instantiate an SMIME object.</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="c1"># Load the signer's cert.</span>
<span class="n">x509</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">load_cert</span><span class="p">(</span><span class="s1">'signer.pem'</span><span class="p">)</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Stack</span><span class="p">()</span>
<span class="n">sk</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">x509</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_stack</span><span class="p">(</span><span class="n">sk</span><span class="p">)</span>
<span class="c1"># Load the signer's CA cert. In this case, because the signer's</span>
<span class="c1"># cert is self-signed, it is the signer's cert itself.</span>
<span class="n">st</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Store</span><span class="p">()</span>
<span class="n">st</span><span class="o">.</span><span class="n">load_info</span><span class="p">(</span><span class="s1">'signer.pem'</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_store</span><span class="p">(</span><span class="n">st</span><span class="p">)</span>
<span class="c1"># Load the data, verify it.</span>
<span class="n">p7</span><span class="p">,</span> <span class="n">data</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">smime_load_pkcs7</span><span class="p">(</span><span class="s1">'sign.p7'</span><span class="p">)</span>
<span class="n">v</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">verify</span><span class="p">(</span><span class="n">p7</span><span class="p">,</span> <span class="n">data</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">v</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">data</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
</pre></div>
</div>
<p>Here’s the output of the above program:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="n">sign</span> <span class="n">of</span> <span class="n">our</span> <span class="n">times</span>
<span class="o"><</span><span class="n">M2Crypto</span><span class="o">.</span><span class="n">BIO</span><span class="o">.</span><span class="n">BIO</span> <span class="n">instance</span> <span class="n">at</span> <span class="mh">0x822012c</span><span class="o">></span>
<span class="n">a</span> <span class="n">sign</span> <span class="n">of</span> <span class="n">our</span> <span class="n">times</span>
</pre></div>
</div>
<p>Suppose, instead of loading <code class="docutils literal notranslate"><span class="pre">signer.pem</span></code> above, we load
<code class="docutils literal notranslate"><span class="pre">recipient.pem</span></code>. That is, we do a global substitution of
<code class="docutils literal notranslate"><span class="pre">recipient.pem</span></code> for <code class="docutils literal notranslate"><span class="pre">signer.pem</span></code> in the above program. Here’s the
modified program’s output:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>Traceback (most recent call last):
File "./verify.py", line 22, in ?
v = s.verify(p7)
File "/usr/local/home/ngps/prog/m2/M2Crypto/SMIME.py", line 205, in verify
raise SMIME_Error, Err.get_error()
M2Crypto.SMIME.SMIME_Error: 312:error:21075075:PKCS7 routines:PKCS7_verify:certificate verify error:pk7_smime.c:213:Verify error:self signed certificate
</pre></div>
</div>
<p>As displayed, the error is generated by line 213 of OpenSSL’s
<code class="docutils literal notranslate"><span class="pre">pk7_smime.c</span></code> (as of OpenSSL 0.9.6); if you are a C programmer, you
may wish to look up the C source to explore OpenSSL’s S/MIME
implementation and understand why the error message is worded thus.</p>
</div>
<div class="section" id="encrypt">
<h1>Encrypt<a class="headerlink" href="#encrypt" title="Permalink to this headline">¶</a></h1>
<p>We now demonstrate how to generate an S/MIME-encrypted message:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">BIO</span><span class="p">,</span> <span class="n">Rand</span><span class="p">,</span> <span class="n">SMIME</span><span class="p">,</span> <span class="n">X509</span>
<span class="k">def</span> <span class="nf">makebuf</span><span class="p">(</span><span class="n">text</span><span class="p">):</span>
<span class="k">return</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">(</span><span class="n">text</span><span class="p">)</span>
<span class="c1"># Make a MemoryBuffer of the message.</span>
<span class="n">buf</span> <span class="o">=</span> <span class="n">makebuf</span><span class="p">(</span><span class="s1">'a sign of our times'</span><span class="p">)</span>
<span class="c1"># Seed the PRNG.</span>
<span class="n">Rand</span><span class="o">.</span><span class="n">load_file</span><span class="p">(</span><span class="s1">'randpool.dat'</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">)</span>
<span class="c1"># Instantiate an SMIME object.</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="c1"># Load target cert to encrypt to.</span>
<span class="n">x509</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">load_cert</span><span class="p">(</span><span class="s1">'recipient.pem'</span><span class="p">)</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Stack</span><span class="p">()</span>
<span class="n">sk</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">x509</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_stack</span><span class="p">(</span><span class="n">sk</span><span class="p">)</span>
<span class="c1"># Set cipher: 3-key triple-DES in CBC mode.</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_cipher</span><span class="p">(</span><span class="n">SMIME</span><span class="o">.</span><span class="n">Cipher</span><span class="p">(</span><span class="s1">'des_ede3_cbc'</span><span class="p">))</span>
<span class="c1"># Encrypt the buffer.</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">encrypt</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span>
<span class="c1"># Output p7 in mail-friendly format.</span>
<span class="n">out</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">()</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'From: sender@example.dom</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'To: recipient@example.dom</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'Subject: M2Crypto S/MIME testing</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">out</span><span class="p">,</span> <span class="n">p7</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">out</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
<span class="c1"># Save the PRNG's state.</span>
<span class="n">Rand</span><span class="o">.</span><span class="n">save_file</span><span class="p">(</span><span class="s1">'randpool.dat'</span><span class="p">)</span>
</pre></div>
</div>
<p>Here’s the output of the above program:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">From</span><span class="p">:</span> <span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">To</span><span class="p">:</span> <span class="n">recipient</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">Subject</span><span class="p">:</span> <span class="n">M2Crypto</span> <span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">testing</span>
<span class="n">MIME</span><span class="o">-</span><span class="n">Version</span><span class="p">:</span> <span class="mf">1.0</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Disposition</span><span class="p">:</span> <span class="n">attachment</span><span class="p">;</span> <span class="n">filename</span><span class="o">=</span><span class="s2">"smime.p7m"</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">x</span><span class="o">-</span><span class="n">pkcs7</span><span class="o">-</span><span class="n">mime</span><span class="p">;</span> <span class="n">name</span><span class="o">=</span><span class="s2">"smime.p7m"</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Transfer</span><span class="o">-</span><span class="n">Encoding</span><span class="p">:</span> <span class="n">base64</span>
<span class="n">MIIBVwYJKoZIhvcNAQcDoIIBSDCCAUQCAQAxggEAMIH9AgEAMGYwYTELMAkGA1UE</span>
<span class="n">BhMCU0cxETAPBgNVBAoTCE0yQ3J5cHRvMRkwFwYDVQQDExBTL01JTUUgUmVjaXBp</span>
<span class="n">ZW50MSQwIgYJKoZIhvcNAQkBFhVyZWNpcGllbnRAZXhhbXBsZS5kb20CAQAwDQYJ</span>
<span class="n">KoZIhvcNAQEBBQAEgYCBaXZ</span><span class="o">+</span><span class="n">qjpBEZwdP7gjfzfAtQitESyMwo3i</span><span class="o">+</span><span class="n">LBOw6sSDir6</span>
<span class="n">FlNDPCnkrTvqDX3Rt6X6vBtTCYOm</span><span class="o">+</span><span class="n">qiN7ujPkOU61cN7h8dvHR8YW9</span><span class="o">+</span><span class="mi">0</span><span class="n">IPY80</span><span class="o">/</span><span class="n">W0</span>
<span class="n">lZ</span><span class="o">/</span><span class="n">HihSRgwTNd7LnxUUcPx8YV1id0dlmP0Hz</span><span class="o">+</span><span class="n">Lg</span><span class="o">+</span><span class="n">mHf6rqaR</span><span class="o">//</span><span class="n">JcYhX9vW4XvjA7</span>
<span class="n">BgkqhkiG9w0BBwEwFAYIKoZIhvcNAwcECMN</span><span class="o">+</span><span class="n">qya6ADywgBgHr9Jkhwn5Gsdu7BwX</span>
<span class="n">nIQfYTYcdL9I5Sk</span><span class="o">=</span>
</pre></div>
</div>
</div>
<div class="section" id="decrypt">
<h1>Decrypt<a class="headerlink" href="#decrypt" title="Permalink to this headline">¶</a></h1>
<p>Assume the above output has been saved into <code class="docutils literal notranslate"><span class="pre">encrypt.p7</span></code>. Decrypt the
message thusly:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">BIO</span><span class="p">,</span> <span class="n">SMIME</span><span class="p">,</span> <span class="n">X509</span>
<span class="c1"># Instantiate an SMIME object.</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="c1"># Load private key and cert.</span>
<span class="n">s</span><span class="o">.</span><span class="n">load_key</span><span class="p">(</span><span class="s1">'recipient_key.pem'</span><span class="p">,</span> <span class="s1">'recipient.pem'</span><span class="p">)</span>
<span class="c1"># Load the encrypted data.</span>
<span class="n">p7</span><span class="p">,</span> <span class="n">data</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">smime_load_pkcs7</span><span class="p">(</span><span class="s1">'encrypt.p7'</span><span class="p">)</span>
<span class="c1"># Decrypt p7.</span>
<span class="n">out</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">decrypt</span><span class="p">(</span><span class="n">p7</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">out</span><span class="p">)</span>
</pre></div>
</div>
<p>Here’s the output:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="n">sign</span> <span class="n">of</span> <span class="n">our</span> <span class="n">times</span>
</pre></div>
</div>
</div>
<div class="section" id="sign-and-encrypt">
<h1>Sign and Encrypt<a class="headerlink" href="#sign-and-encrypt" title="Permalink to this headline">¶</a></h1>
<p>Here’s how to generate an S/MIME-signed/encrypted message:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">BIO</span><span class="p">,</span> <span class="n">Rand</span><span class="p">,</span> <span class="n">SMIME</span><span class="p">,</span> <span class="n">X509</span>
<span class="k">def</span> <span class="nf">makebuf</span><span class="p">(</span><span class="n">text</span><span class="p">):</span>
<span class="k">return</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">(</span><span class="n">text</span><span class="p">)</span>
<span class="c1"># Make a MemoryBuffer of the message.</span>
<span class="n">buf</span> <span class="o">=</span> <span class="n">makebuf</span><span class="p">(</span><span class="s1">'a sign of our times'</span><span class="p">)</span>
<span class="c1"># Seed the PRNG.</span>
<span class="n">Rand</span><span class="o">.</span><span class="n">load_file</span><span class="p">(</span><span class="s1">'randpool.dat'</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">)</span>
<span class="c1"># Instantiate an SMIME object.</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="c1"># Load signer's key and cert. Sign the buffer.</span>
<span class="n">s</span><span class="o">.</span><span class="n">load_key</span><span class="p">(</span><span class="s1">'signer_key.pem'</span><span class="p">,</span> <span class="s1">'signer.pem'</span><span class="p">)</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span>
<span class="c1"># Load target cert to encrypt the signed message to.</span>
<span class="n">x509</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">load_cert</span><span class="p">(</span><span class="s1">'recipient.pem'</span><span class="p">)</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Stack</span><span class="p">()</span>
<span class="n">sk</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">x509</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_stack</span><span class="p">(</span><span class="n">sk</span><span class="p">)</span>
<span class="c1"># Set cipher: 3-key triple-DES in CBC mode.</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_cipher</span><span class="p">(</span><span class="n">SMIME</span><span class="o">.</span><span class="n">Cipher</span><span class="p">(</span><span class="s1">'des_ede3_cbc'</span><span class="p">))</span>
<span class="c1"># Create a temporary buffer.</span>
<span class="n">tmp</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">()</span>
<span class="c1"># Write the signed message into the temporary buffer.</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">tmp</span><span class="p">,</span> <span class="n">p7</span><span class="p">)</span>
<span class="c1"># Encrypt the temporary buffer.</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">encrypt</span><span class="p">(</span><span class="n">tmp</span><span class="p">)</span>
<span class="c1"># Output p7 in mail-friendly format.</span>
<span class="n">out</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">()</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'From: sender@example.dom</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'To: recipient@example.dom</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'Subject: M2Crypto S/MIME testing</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">out</span><span class="p">,</span> <span class="n">p7</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">out</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
<span class="c1"># Save the PRNG's state.</span>
<span class="n">Rand</span><span class="o">.</span><span class="n">save_file</span><span class="p">(</span><span class="s1">'randpool.dat'</span><span class="p">)</span>
</pre></div>
</div>
<p>Here’s the output of the above program:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">From</span><span class="p">:</span> <span class="n">sender</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">To</span><span class="p">:</span> <span class="n">recipient</span><span class="nd">@example</span><span class="o">.</span><span class="n">dom</span>
<span class="n">Subject</span><span class="p">:</span> <span class="n">M2Crypto</span> <span class="n">S</span><span class="o">/</span><span class="n">MIME</span> <span class="n">testing</span>
<span class="n">MIME</span><span class="o">-</span><span class="n">Version</span><span class="p">:</span> <span class="mf">1.0</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Disposition</span><span class="p">:</span> <span class="n">attachment</span><span class="p">;</span> <span class="n">filename</span><span class="o">=</span><span class="s2">"smime.p7m"</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Type</span><span class="p">:</span> <span class="n">application</span><span class="o">/</span><span class="n">x</span><span class="o">-</span><span class="n">pkcs7</span><span class="o">-</span><span class="n">mime</span><span class="p">;</span> <span class="n">name</span><span class="o">=</span><span class="s2">"smime.p7m"</span>
<span class="n">Content</span><span class="o">-</span><span class="n">Transfer</span><span class="o">-</span><span class="n">Encoding</span><span class="p">:</span> <span class="n">base64</span>
<span class="n">MIIIwwYJKoZIhvcNAQcDoIIItDCCCLACAQAxggEAMIH9AgEAMGYwYTELMAkGA1UE</span>
<span class="n">BhMCU0cxETAPBgNVBAoTCE0yQ3J5cHRvMRkwFwYDVQQDExBTL01JTUUgUmVjaXBp</span>
<span class="n">ZW50MSQwIgYJKoZIhvcNAQkBFhVyZWNpcGllbnRAZXhhbXBsZS5kb20CAQAwDQYJ</span>
<span class="n">KoZIhvcNAQEBBQAEgYBlZlGupFphwhsGtIAPvDExN61qisz3oem88xoXkUW0SzoR</span>
<span class="n">B9zJFFAuQTWzdNJgrKKYikhWjDojaAc</span><span class="o">/</span><span class="n">PFl1K5dYxRgtZLB36ULJD</span><span class="o">/</span><span class="n">v</span><span class="o">/</span><span class="n">yWmxnjz8</span>
<span class="n">TvtK</span><span class="o">+</span><span class="n">Wbal2P</span><span class="o">/</span><span class="n">MH2pZ4LVERXa</span><span class="o">/</span><span class="n">snTElhCawUlwtiFz</span><span class="o">/</span><span class="n">JvY5CiF</span><span class="o">/</span><span class="n">dcwd</span><span class="o">+</span><span class="n">AwFQq4jCC</span>
<span class="n">B6UGCSqGSIb3DQEHATAUBggqhkiG9w0DBwQIRF525UfwszaAggeA85RmX6AXQMxb</span>
<span class="n">eBDz</span><span class="o">/</span><span class="n">LJeCgc3RqU1UwIsbKMquIs1S46Ebbm5nP75izPnujOkJ2hv</span><span class="o">+</span><span class="n">LNzqOWADmOl</span>
<span class="o">+</span><span class="n">CnGEq1qxTyduIgUDA2nBgCL</span><span class="o">/</span><span class="n">gVyVy</span><span class="o">+/</span><span class="n">XC9dtImUUTxtxLgYtB0ujkBNsOaENOlM</span>
<span class="n">fv4SGM3jkR</span><span class="o">+</span><span class="n">K</span><span class="o">/</span><span class="n">xlYG6HHzZGbfYyNGj2Y7yMZ1rL1m8SnRNmkCysKGTrudeNf6wT9</span>
<span class="n">J6wO9DzLTioz3ZnVr3LjsSKIb4tIp4ugqNJaLuW7m3FtZ3MAgxN68hBbJs8TZ8tL</span>
<span class="n">V</span><span class="o">/</span><span class="mi">0</span><span class="n">jwUqS</span><span class="o">+</span><span class="n">grcgZEb9ymfcedxahtDUfHjRkpDpsxZzVVGkSBNcbQu92oByQVnRQ8m</span>
<span class="n">wrYLp3</span><span class="o">/</span><span class="n">eawM5AvuV7HNpTT5ZR</span><span class="o">+</span><span class="mi">1</span><span class="n">t8luishHN9899IMP2Vyg0Ub67FqFypYmM2cm2</span>
<span class="n">sjAI4KpfvT00XFNvgLuYwYEKs9syGTO7hiHNQKcF44F5LYv6nTFwmFQB11dAtY9V</span>
<span class="n">ull4D2CLDx9OvyNyKwdEZB5dyV0r</span><span class="o">/</span><span class="n">uKIdkhST60V2Q9KegpzgFpoZtSKM</span><span class="o">/</span><span class="n">HPYSVH</span>
<span class="mi">1</span><span class="n">Bc9f3Q</span><span class="o">/</span><span class="n">GqZCvNZZCMx8UvRjQR8dRWDSmPJ0VXG1</span><span class="o">+</span><span class="n">wJ</span><span class="o">+</span><span class="n">fCmSPP3AuQ1</span><span class="o">/</span><span class="n">VsgPRqx2</span>
<span class="mi">56</span><span class="n">VrpGPpGut40hV8xQFbWIZ2whwWLKPFAHj8B79ZtFUzUrU6Z2rNpvv8inHc</span><span class="o">/+</span><span class="n">S</span><span class="o">/</span>
<span class="n">b6GR5s8</span><span class="o">/</span><span class="n">gucRblvd7n3OFNX5UJmPmcw9zWbu</span><span class="o">/</span><span class="mi">1</span><span class="n">Dr9DY8l0nAQh21y5FGSS8B1wdE</span>
<span class="n">oD2M3Lp7JbwjQbRtnDhImqul2S4yu</span><span class="o">+</span><span class="n">m</span><span class="o">+</span><span class="n">wDD1aR2K4k3GAI7KKgOBWT0</span><span class="o">+</span><span class="n">BDClcn8A</span>
<span class="mi">4</span><span class="n">Ju6</span><span class="o">/</span><span class="n">YUbj33YlMPJgnGijLnolFy0hNW7TmWqR</span><span class="o">+</span><span class="mi">8</span><span class="n">tSI3wO5eNKg4qwBnarqc3vgCV</span>
<span class="n">quVxINAXyGQCO9lzdw6hudk8</span><span class="o">/+</span><span class="n">BlweGdqhONaIWbK5z1L</span><span class="o">/</span><span class="n">SfQo6LC9MTsj7FJydq</span>
<span class="n">bc</span><span class="o">+</span><span class="n">kEbfZS8aSq7uc9axW6Ti0eAPJ8EVHtwhSBgZQRweKFBXs6HbbhMIdc4N0M7Oq</span>
<span class="n">UiFXaF6s4n2uihVP6TqXtHEjTpZoC7pC</span><span class="o">+</span><span class="n">HCYiuKXUJtaqtXBOh</span><span class="o">+</span><span class="n">y3KLvHk09YL6D</span>
<span class="n">XmTDg</span><span class="o">+</span><span class="n">UTiFsh4jKKm</span><span class="o">/</span><span class="n">BhdelbR5JbpJcj5AId76Mfr8</span><span class="o">+</span><span class="n">F</span><span class="o">/</span><span class="mi">1</span><span class="n">g9ePOvsWHpQr</span><span class="o">/</span><span class="n">oIQTo</span>
<span class="n">xEkaxCmzEgP0b6caMWfMUQrbVGxBBNcqKc</span><span class="o">/</span><span class="n">ir9fGGOPHATzzq</span><span class="o">/</span><span class="n">xLcQYvK1tZhd</span><span class="o">/</span><span class="n">D</span>
<span class="n">ah</span><span class="o">/</span><span class="n">gpMPndsyvVCEuFPluWyDiM0VkwHgC2</span><span class="o">/</span><span class="mi">3</span><span class="n">pJIYFHaxK64IutmPsy393rHMEB4kN</span>
<span class="n">AHau6kWK</span><span class="o">+</span><span class="n">yL9qEVH1pP2zvswQ12P7gjt3T</span><span class="o">/</span><span class="n">G3bGsmvlXkEfztfjkXo6XnjcBNf5y</span>
<span class="n">G</span><span class="o">+</span><span class="mi">974</span><span class="n">AKLcjnk1gzIgarz</span><span class="o">+</span><span class="n">lAMY57Gkw4oNDMrTqVQ2OJQlvOSbllPXzH</span><span class="o">+</span><span class="n">aAiavB8W</span>
<span class="n">ZPECLLwHxD4B1AuaiAArgKl935u</span><span class="o">/</span><span class="n">TOB</span><span class="o">+</span><span class="n">yQOR8JgGsUzROyJqHJ</span><span class="o">/</span><span class="n">SC51HkebgCkL1</span>
<span class="n">aggtjgPlIBEXLZAlhpWLZ9lAQyrQpvCVJYwaOvfMmvRav4NAFNoZ2</span><span class="o">/</span><span class="n">Q7S4Tn1z</span><span class="o">+</span><span class="n">U</span>
<span class="n">XX</span><span class="o">+</span><span class="n">f</span><span class="o">+</span><span class="n">GD58P4MPMhU5IKnz4yH4nlHnAiTEvcs85TZUAXze9g</span><span class="o">/</span><span class="n">uBOwZITeGtyLi52S</span>
<span class="n">aETIr4v7SgXMepX7ThQ1Pv</span><span class="o">/</span><span class="n">jddsK</span><span class="o">/</span><span class="n">u4j2F34u0XktwCP</span><span class="o">+</span><span class="n">UrbfkE2mocdXvdzxbmd</span>
<span class="n">tZSznK2qwgVSsPOs9MhUaepbnjmNBFFBrULhrUtSglM</span><span class="o">/</span><span class="n">VX</span><span class="o">/</span><span class="n">rWNiyh0aw4XYyHhIt</span>
<span class="mi">9</span><span class="n">ZNlfEjKjJ67VEMBxBJ</span><span class="o">/</span><span class="n">ieUCouRGCxPYD1j65VT7oB3ZiyPu2F2nlUIcYNqPg1Sd</span>
<span class="n">QBCrdaOXdJ0uLwyTAUeVE</span><span class="o">+</span><span class="n">wMbgscLvWsfZcCCJHAvw9NHFMUcnrdWxAYMVETNUOn</span>
<span class="n">uryVAK7VfOldaz6z3NOSOi6nonNeHpR</span><span class="o">/</span><span class="n">sipBa4ik5xCRLT9e0S2QJgRvO9GyfAqz</span>
<span class="mi">3</span><span class="n">DIzHtxIGePFzTiUYUTxS3i2gnMX2PEe3ChTLlYWD3jNeAKz0iOzpDphIF2xHLLQ</span>
<span class="mi">1</span><span class="n">tCAqBmq</span><span class="o">/</span><span class="n">vUzALyDFFdFuTIqQZys4z</span><span class="o">/</span><span class="n">u4Dmyq9uXs421eN3v2hkVHvDy8uT2Ot29</span>
<span class="n">lg4Q5YezR1EjaW</span><span class="o">//</span><span class="mi">9</span><span class="n">guL1BXbcKrTEdtxeNqtem7SpZOMTSwD2lhB8z65GrX90Cyt</span>
<span class="n">EMmaRSGYEdf5h1afL1SmKOMskbqxe1D2jG</span><span class="o">/</span><span class="n">vsXC7XX7xO</span><span class="o">/</span><span class="n">ioy0BdiJcYN1JiMOHJ</span>
<span class="n">EOzFol5I20YkiV6j</span><span class="o">+</span><span class="n">cenfQFwc</span><span class="o">/</span><span class="n">NkaSxEkR8AUHJSbvUmRQRl6r0nnsFpZdR1w7pv</span>
<span class="n">wkaT</span><span class="o">+</span><span class="n">eOpZynO4mY</span><span class="o">/</span><span class="n">ZtF6MpXJsixi6L4ZYXEbS6yHf</span><span class="o">+</span><span class="n">XGFfB0okILylmwv2bf6</span><span class="o">+</span><span class="n">Mq</span>
<span class="n">nqXlmGj3Jwq7X9</span><span class="o">/+</span><span class="mi">2</span><span class="n">BDqvfpFFX5lSmItKZAobLdssjFR6roJxOqRsGia2aZ</span><span class="o">+</span><span class="mi">0</span><span class="o">+</span><span class="n">U5</span>
<span class="n">VhgdITtnElgtHBaeZU5rHDswgdeLVBP</span><span class="o">+</span><span class="n">rGWnKxpJ</span><span class="o">+</span><span class="n">pLtNNi25sPYRcWFL6Erd25u</span>
<span class="n">eXiY8GEIr</span><span class="o">+</span><span class="n">u7rqBWpc9HR34sAPRs3ubbCUleT748keCbx247ImBtiDctZxcc1O86</span>
<span class="o">+</span><span class="mi">0</span><span class="n">QjHP6HUT7FSo</span><span class="o">/</span><span class="n">FmT7a120S3Gd2jixGh06l</span><span class="o">/</span><span class="mi">9</span><span class="n">ij5Z6mJa7Rm7TTbSjup</span><span class="o">/</span><span class="n">XISnOT</span>
<span class="n">MKWcbI1nfVOhCv3xDq2eLae</span><span class="o">+</span><span class="n">s0oVoc041ceRazqFM2TL</span><span class="o">/</span><span class="n">Z6UXRME</span>
</pre></div>
</div>
</div>
<div class="section" id="decrypt-and-verify">
<h1>Decrypt and Verify<a class="headerlink" href="#decrypt-and-verify" title="Permalink to this headline">¶</a></h1>
<p>Suppose the above output has been saved into <code class="docutils literal notranslate"><span class="pre">se.p7</span></code>. The following
demonstrates how to decrypt and verify it:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">BIO</span><span class="p">,</span> <span class="n">SMIME</span><span class="p">,</span> <span class="n">X509</span>
<span class="c1"># Instantiate an SMIME object.</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="c1"># Load private key and cert.</span>
<span class="n">s</span><span class="o">.</span><span class="n">load_key</span><span class="p">(</span><span class="s1">'recipient_key.pem'</span><span class="p">,</span> <span class="s1">'recipient.pem'</span><span class="p">)</span>
<span class="c1"># Load the signed/encrypted data.</span>
<span class="n">p7</span><span class="p">,</span> <span class="n">data</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">smime_load_pkcs7</span><span class="p">(</span><span class="s1">'se.p7'</span><span class="p">)</span>
<span class="c1"># After the above step, 'data' == None.</span>
<span class="c1"># Decrypt p7. 'out' now contains a PKCS #7 signed blob.</span>
<span class="n">out</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">decrypt</span><span class="p">(</span><span class="n">p7</span><span class="p">)</span>
<span class="c1"># Load the signer's cert.</span>
<span class="n">x509</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">load_cert</span><span class="p">(</span><span class="s1">'signer.pem'</span><span class="p">)</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Stack</span><span class="p">()</span>
<span class="n">sk</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">x509</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_stack</span><span class="p">(</span><span class="n">sk</span><span class="p">)</span>
<span class="c1"># Load the signer's CA cert. In this case, because the signer's</span>
<span class="c1"># cert is self-signed, it is the signer's cert itself.</span>
<span class="n">st</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Store</span><span class="p">()</span>
<span class="n">st</span><span class="o">.</span><span class="n">load_info</span><span class="p">(</span><span class="s1">'signer.pem'</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_store</span><span class="p">(</span><span class="n">st</span><span class="p">)</span>
<span class="c1"># Recall 'out' contains a PKCS #7 blob.</span>
<span class="c1"># Transform 'out'; verify the resulting PKCS #7 blob.</span>
<span class="n">p7_bio</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">(</span><span class="n">out</span><span class="p">)</span>
<span class="n">p7</span><span class="p">,</span> <span class="n">data</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">smime_load_pkcs7_bio</span><span class="p">(</span><span class="n">p7_bio</span><span class="p">)</span>
<span class="n">v</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">verify</span><span class="p">(</span><span class="n">p7</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">v</span><span class="p">)</span>
</pre></div>
</div>
<p>The output is as follows:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="n">sign</span> <span class="n">of</span> <span class="n">our</span> <span class="n">times</span>
</pre></div>
</div>
</div>
<div class="section" id="sending-s-mime-messages-via-smtp">
<h1>Sending S/MIME messages via SMTP<a class="headerlink" href="#sending-s-mime-messages-via-smtp" title="Permalink to this headline">¶</a></h1>
<p>In the above examples, we’ve assumed that our S/MIME messages are sent
and received automagically. The following is a Python function that
generates S/MIME-signed/encrypted messages and sends them via
SMTP:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="kn">import</span> <span class="n">BIO</span><span class="p">,</span> <span class="n">SMIME</span><span class="p">,</span> <span class="n">X509</span>
<span class="kn">import</span> <span class="nn">smtplib</span><span class="o">,</span> <span class="nn">string</span><span class="o">,</span> <span class="nn">sys</span>
<span class="k">def</span> <span class="nf">sendsmime</span><span class="p">(</span><span class="n">from_addr</span><span class="p">,</span> <span class="n">to_addrs</span><span class="p">,</span> <span class="n">subject</span><span class="p">,</span> <span class="n">msg</span><span class="p">,</span> <span class="n">from_key</span><span class="p">,</span> <span class="n">from_cert</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">to_certs</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">smtpd</span><span class="o">=</span><span class="s1">'localhost'</span><span class="p">):</span>
<span class="n">msg_bio</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span>
<span class="n">sign</span> <span class="o">=</span> <span class="n">from_key</span>
<span class="n">encrypt</span> <span class="o">=</span> <span class="n">to_certs</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">SMIME</span><span class="p">()</span>
<span class="k">if</span> <span class="n">sign</span><span class="p">:</span>
<span class="n">s</span><span class="o">.</span><span class="n">load_key</span><span class="p">(</span><span class="n">from_key</span><span class="p">,</span> <span class="n">from_cert</span><span class="p">)</span>
<span class="k">if</span> <span class="n">encrypt</span><span class="p">:</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">msg_bio</span><span class="p">,</span> <span class="n">flags</span><span class="o">=</span><span class="n">SMIME</span><span class="o">.</span><span class="n">PKCS7_TEXT</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">msg_bio</span><span class="p">,</span> <span class="n">flags</span><span class="o">=</span><span class="n">SMIME</span><span class="o">.</span><span class="n">PKCS7_TEXT</span><span class="o">|</span><span class="n">SMIME</span><span class="o">.</span><span class="n">PKCS7_DETACHED</span><span class="p">)</span>
<span class="n">msg_bio</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span> <span class="c1"># Recreate coz sign() has consumed it.</span>
<span class="k">if</span> <span class="n">encrypt</span><span class="p">:</span>
<span class="n">sk</span> <span class="o">=</span> <span class="n">X509</span><span class="o">.</span><span class="n">X509_Stack</span><span class="p">()</span>
<span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">to_certs</span><span class="p">:</span>
<span class="n">sk</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">X509</span><span class="o">.</span><span class="n">load_cert</span><span class="p">(</span><span class="n">x</span><span class="p">))</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_x509_stack</span><span class="p">(</span><span class="n">sk</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_cipher</span><span class="p">(</span><span class="n">SMIME</span><span class="o">.</span><span class="n">Cipher</span><span class="p">(</span><span class="s1">'des_ede3_cbc'</span><span class="p">))</span>
<span class="n">tmp_bio</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">()</span>
<span class="k">if</span> <span class="n">sign</span><span class="p">:</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">tmp_bio</span><span class="p">,</span> <span class="n">p7</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">tmp_bio</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span>
<span class="n">p7</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">encrypt</span><span class="p">(</span><span class="n">tmp_bio</span><span class="p">)</span>
<span class="n">out</span> <span class="o">=</span> <span class="n">BIO</span><span class="o">.</span><span class="n">MemoryBuffer</span><span class="p">()</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'From: </span><span class="si">%s</span><span class="se">\r\n</span><span class="s1">'</span> <span class="o">%</span> <span class="n">from_addr</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'To: </span><span class="si">%s</span><span class="se">\r\n</span><span class="s1">'</span> <span class="o">%</span> <span class="n">string</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">to_addrs</span><span class="p">,</span> <span class="s2">", "</span><span class="p">))</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'Subject: </span><span class="si">%s</span><span class="se">\r\n</span><span class="s1">'</span> <span class="o">%</span> <span class="n">subject</span><span class="p">)</span>
<span class="k">if</span> <span class="n">encrypt</span><span class="p">:</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">out</span><span class="p">,</span> <span class="n">p7</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">if</span> <span class="n">sign</span><span class="p">:</span>
<span class="n">s</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">out</span><span class="p">,</span> <span class="n">p7</span><span class="p">,</span> <span class="n">msg_bio</span><span class="p">,</span> <span class="n">SMIME</span><span class="o">.</span><span class="n">PKCS7_TEXT</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'</span><span class="se">\r\n</span><span class="s1">'</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span>
<span class="n">out</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">smtp</span> <span class="o">=</span> <span class="n">smtplib</span><span class="o">.</span><span class="n">SMTP</span><span class="p">()</span>
<span class="n">smtp</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="n">smtpd</span><span class="p">)</span>
<span class="n">smtp</span><span class="o">.</span><span class="n">sendmail</span><span class="p">(</span><span class="n">from_addr</span><span class="p">,</span> <span class="n">to_addrs</span><span class="p">,</span> <span class="n">out</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
<span class="n">smtp</span><span class="o">.</span><span class="n">quit</span><span class="p">()</span>
</pre></div>
</div>
<p>This function sends plain, S/MIME-signed, S/MIME-encrypted, and
S/MIME-signed/encrypted messages, depending on the parameters
<code class="docutils literal notranslate"><span class="pre">from_key</span></code> and <code class="docutils literal notranslate"><span class="pre">to_certs</span></code>. The function’s output interoperates with
Netscape Messenger.</p>
</div>
<div class="section" id="verifying-origin-of-s-mime-messages">
<h1>Verifying origin of S/MIME messages<a class="headerlink" href="#verifying-origin-of-s-mime-messages" title="Permalink to this headline">¶</a></h1>
<p>In our examples above that decrypt or verify messages, we skipped a
step: verifying that the <code class="docutils literal notranslate"><span class="pre">from</span></code> address of the message matches the
<code class="docutils literal notranslate"><span class="pre">email</span> <span class="pre">address</span></code> attribute in the sender’s certificate.</p>
<p>The premise of current X.509 certification practice is that the CA is
supposed to verify your identity, and to issue a certificate with
<code class="docutils literal notranslate"><span class="pre">email</span> <span class="pre">address</span></code> that matches your actual mail address. (Verisign’s
March 2001 failure in identity verification resulting in Microsoft
certificates being issued to spoofers notwithstanding.)</p>
<p>If you run your own CA, your certification practice is up to you, of
course, and it would probably be part of your security policy.</p>
<p>Whether your S/MIME messaging application needs to verify the <code class="docutils literal notranslate"><span class="pre">from</span></code>
addresses of S/MIME messages depends on your security policy and your
system’s threat model, as always.</p>
</div>
<div class="section" id="interoperating-with-netscape-messenger">
<h1>Interoperating with Netscape Messenger<a class="headerlink" href="#interoperating-with-netscape-messenger" title="Permalink to this headline">¶</a></h1>
<p>Suppose S/MIME Recipient uses Netscape Messenger. To enable Messenger to
handle S/MIME messages from S/MIME Sender, S/MIME Recipient needs to
configure Messenger with his private key and certificate, as well as
S/MIME Sender’s certificate.</p>
<blockquote>
<div><p><strong>Note:</strong> Configuring Messenger’s POP or IMAP settings so that it
retrieves mail correctly is beyond the scope of this HOWTO.</p>
</div></blockquote>
<p>The following steps demonstrate how to import S/MIME Recipient’s private
key and certificate for Messenger:</p>
<ol class="arabic">
<li><p>Transform S/MIME Recipient’s private key and certificate into <em>PKCS
#12</em> format:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">openssl</span> <span class="n">pkcs12</span> <span class="o">-</span><span class="n">export</span> <span class="o">-</span><span class="ow">in</span> <span class="n">recipient</span><span class="o">.</span><span class="n">pem</span> <span class="o">-</span><span class="n">inkey</span> <span class="n">recipient_key</span><span class="o">.</span><span class="n">pem</span> \
<span class="o">-</span><span class="n">name</span> <span class="s2">"S/MIME Recipient"</span> <span class="o">-</span><span class="n">out</span> <span class="n">recipient</span><span class="o">.</span><span class="n">p12</span>
<span class="n">Enter</span> <span class="n">Export</span> <span class="n">Password</span><span class="p">:</span><span class="o"><</span><span class="n">enter</span><span class="o">></span>
<span class="n">Verifying</span> <span class="n">password</span> <span class="o">-</span> <span class="n">Enter</span> <span class="n">Export</span> <span class="n">Password</span><span class="p">:</span><span class="o"><</span><span class="n">enter</span><span class="o">></span>
</pre></div>
</div>
</li>
<li><p>Start Messenger.</p></li>
<li><p>Click on the (open) “lock” icon at the bottom left corner of
Messenger’s window. This brings up the “Security Info” dialog box.</p></li>
<li><p>Click on “Yours” under “Certificates”.</p></li>
<li><p>Select “Import a certificate”, then pick <code class="docutils literal notranslate"><span class="pre">recipient.p12</span></code> from the
ensuing file selection dialog box.</p></li>
</ol>
<p>Next, you need to import <code class="docutils literal notranslate"><span class="pre">signer.pem</span></code> as a CA certificate, so that
Messenger will mark messages signed by S/MIME Sender as “trusted”:</p>
<ol class="arabic">
<li><p>Create a DER encoding of <code class="docutils literal notranslate"><span class="pre">signer.pem</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">openssl</span> <span class="n">x509</span> <span class="o">-</span><span class="n">inform</span> <span class="n">pem</span> <span class="o">-</span><span class="n">outform</span> <span class="n">der</span> <span class="o">-</span><span class="ow">in</span> <span class="n">signer</span><span class="o">.</span><span class="n">pem</span> <span class="o">-</span><span class="n">out</span> <span class="n">signer</span><span class="o">.</span><span class="n">der</span>
</pre></div>
</div>
</li>
<li><p>Install <code class="docutils literal notranslate"><span class="pre">signer.der</span></code> into Messenger as MIME type
<code class="docutils literal notranslate"><span class="pre">application/x-x509-ca-cert</span></code>. You do this by downloading
<code class="docutils literal notranslate"><span class="pre">signer.der</span></code> via Navigator from a HTTP or HTTPS server, with the
correct MIME type mapping. (You may use <code class="docutils literal notranslate"><span class="pre">demo/ssl/https_srv.py</span></code>,
bundled with M2Crypto, for this purpose.) Follow the series of dialog
boxes to accept <code class="docutils literal notranslate"><span class="pre">signer.der</span></code> as a CA for certifying email users.</p></li>
</ol>
<p>S/MIME Recipient is now able to decrypt and read S/MIME Sender’s
messages with Messenger. Messenger will indicate that S/MIME Sender’s
messages are signed, encrypted, or encrypted <em>and</em> signed, as the case
may be, via the “stamp” icon on the message window’s top right corner.</p>
<p>Clicking on the “stamp” icon brings you to the Security Info dialog box.
Messenger informs you that the message is, say, encrypted with 168-bit
DES-EDE3-CBC and that it is digitally signed by the private key
corresponding to the public key contained in the certificate
<code class="docutils literal notranslate"><span class="pre">signer.pem</span></code>.</p>
</div>
<div class="section" id="interoperating-with-microsoft-outlook">
<h1>Interoperating with Microsoft Outlook<a class="headerlink" href="#interoperating-with-microsoft-outlook" title="Permalink to this headline">¶</a></h1>
<p>I do not know how to do this, as I do not use Outlook. (Nor do I use
Netscape Messenger, actually. I use Mutt, top dog of MUAs. ;-)
Information on how to configure Outlook with keys and certificates so
that it handles S/MIME mail is gratefully accepted.</p>
</div>
<div class="section" id="zsmime">
<h1>ZSmime<a class="headerlink" href="#zsmime" title="Permalink to this headline">¶</a></h1>
<p>ZSmime is a <a class="reference external" href="http://www.zope.org">Zope</a> <em>product</em> that enables Zope
to generate S/MIME-signed/encrypted messages. ZSmime demonstrates how to
invoke M2Crypto in a web application server extension.</p>
<p>ZSmime has its own
<a class="reference external" href="http://sandbox.rulemaker.net/ngps/zope/zsmime/howto.html">HOWTO</a>
explaining its usage. (That HOWTO has some overlap in content with this
document.)</p>
</div>
<div class="section" id="resources">
<h1>Resources<a class="headerlink" href="#resources" title="Permalink to this headline">¶</a></h1>
<ul class="simple">
<li><p>IETF S/MIME Working Group - <a class="reference external" href="http://www.imc.org/ietf-smime">http://www.imc.org/ietf-smime</a></p></li>
<li><p>S/MIME and OpenPGP - <a class="reference external" href="http://www.imc.org/smime-pgpmime.html">http://www.imc.org/smime-pgpmime.html</a></p></li>
<li><p>S/MIME Freeware Library -
<a class="reference external" href="http://www.getronicsgov.com/hot/sfl_home.htm">http://www.getronicsgov.com/hot/sfl_home.htm</a></p></li>
<li><p>Mozilla Network Security Services -
<a class="reference external" href="http://www.mozilla.org/projects/security/pkg/nss">http://www.mozilla.org/projects/security/pkg/nss</a></p></li>
<li><p>S/MIME Cracking Screen Saver - <a class="reference external" href="http://www.counterpane.com/smime.html">http://www.counterpane.com/smime.html</a></p></li>
</ul>
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