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<h1>Source code for M2Crypto.Rand</h1><div class="highlight"><pre>
<span></span><span class="sd">"""M2Crypto wrapper for OpenSSL PRNG. Requires OpenSSL 0.9.5 and above.</span>
<span class="sd">Copyright (c) 1999-2003 Ng Pheng Siong. All rights reserved.</span>
<span class="sd">Copyright (c) 2014-2017 Matej Cepl. All rights reserved.</span>
<span class="sd">See LICENCE for the license information.</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">__future__</span> <span class="k">import</span> <span class="n">absolute_import</span>
<span class="kn">from</span> <span class="nn">M2Crypto</span> <span class="k">import</span> <span class="n">m2</span><span class="p">,</span> <span class="n">py27plus</span><span class="p">,</span> <span class="n">six</span>
<span class="k">if</span> <span class="n">py27plus</span><span class="p">:</span>
<span class="kn">from</span> <span class="nn">typing</span> <span class="k">import</span> <span class="n">AnyStr</span><span class="p">,</span> <span class="n">Tuple</span> <span class="c1"># noqa</span>
<span class="n">__all__</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'rand_seed'</span><span class="p">,</span> <span class="s1">'rand_add'</span><span class="p">,</span> <span class="s1">'load_file'</span><span class="p">,</span> <span class="s1">'save_file'</span><span class="p">,</span> <span class="s1">'rand_bytes'</span><span class="p">,</span>
<span class="s1">'rand_pseudo_bytes'</span><span class="p">,</span> <span class="s1">'rand_file_name'</span><span class="p">,</span> <span class="s1">'rand_status'</span><span class="p">]</span>
<span class="k">class</span> <span class="nc">RandError</span><span class="p">(</span><span class="ne">ValueError</span><span class="p">):</span>
<span class="k">pass</span>
<span class="n">m2</span><span class="o">.</span><span class="n">rand_init</span><span class="p">(</span><span class="n">RandError</span><span class="p">)</span>
<div class="viewcode-block" id="rand_add"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.rand_add">[docs]</a><span class="k">def</span> <span class="nf">rand_add</span><span class="p">(</span><span class="n">blob</span><span class="p">,</span> <span class="n">entropy</span><span class="p">):</span>
<span class="c1"># type: (bytes, float) -> None</span>
<span class="sd">"""</span>
<span class="sd"> Mixes blob into the PRNG state.</span>
<span class="sd"> :param blob: added data</span>
<span class="sd"> :param entropy: (the lower bound of) an estimate of how much randomness</span>
<span class="sd"> is contained in blob, measured in bytes.</span>
<span class="sd"> Thus, if the data at buf are unpredictable to an adversary, this</span>
<span class="sd"> increases the uncertainty about the state and makes the PRNG output less</span>
<span class="sd"> predictable. Suitable input comes from user interaction (random key</span>
<span class="sd"> presses, mouse movements) and certain hardware events.</span>
<span class="sd"> Details about sources of randomness and how to estimate their entropy</span>
<span class="sd"> can be found in the literature, e.g. RFC 1750.</span>
<span class="sd"> """</span>
<span class="n">m2</span><span class="o">.</span><span class="n">rand_add</span><span class="p">(</span><span class="n">blob</span><span class="p">,</span> <span class="n">entropy</span><span class="p">)</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="rand_seed"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.rand_seed">[docs]</a><span class="k">def</span> <span class="nf">rand_seed</span><span class="p">(</span><span class="n">seed</span><span class="p">):</span>
<span class="c1"># type: (bytes) -> None</span>
<span class="sd">"""</span>
<span class="sd"> Equivalent to rand_add() when len(seed) == entropy.</span>
<span class="sd"> :param seed: added data (see description at rand_add)</span>
<span class="sd"> """</span>
<span class="n">m2</span><span class="o">.</span><span class="n">rand_seed</span><span class="p">(</span><span class="n">seed</span><span class="p">)</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="rand_status"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.rand_status">[docs]</a><span class="k">def</span> <span class="nf">rand_status</span><span class="p">():</span>
<span class="c1"># type: () -> int</span>
<span class="sd">"""</span>
<span class="sd"> Check whether there is enough entropy in PRNG.</span>
<span class="sd"> :return: 1 if the PRNG has been seeded with enough</span>
<span class="sd"> data, 0 otherwise.</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">m2</span><span class="o">.</span><span class="n">rand_status</span><span class="p">()</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="rand_file_name"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.rand_file_name">[docs]</a><span class="k">def</span> <span class="nf">rand_file_name</span><span class="p">():</span>
<span class="c1"># type: () -> str</span>
<span class="sd">"""</span>
<span class="sd"> Generate a default path for the random seed file.</span>
<span class="sd"> :return: string with the filename.</span>
<span class="sd"> The seed file is $RANDFILE if that environment variable</span>
<span class="sd"> is set, $HOME/.rnd otherwise. If $HOME is not set either,</span>
<span class="sd"> an error occurs.</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">six</span><span class="o">.</span><span class="n">ensure_text</span><span class="p">(</span><span class="n">m2</span><span class="o">.</span><span class="n">rand_file_name</span><span class="p">())</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="load_file"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.load_file">[docs]</a><span class="k">def</span> <span class="nf">load_file</span><span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="n">max_bytes</span><span class="p">):</span>
<span class="c1"># type: (AnyStr, int) -> int</span>
<span class="sd">"""</span>
<span class="sd"> Read a number of bytes from file filename and adds them to the PRNG.</span>
<span class="sd"> If max_bytes is non-negative, up to to max_bytes are read; starting with</span>
<span class="sd"> OpenSSL 0.9.5, if max_bytes is -1, the complete file is read.</span>
<span class="sd"> :param filename:</span>
<span class="sd"> :param max_bytes:</span>
<span class="sd"> :return: the number of bytes read.</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">m2</span><span class="o">.</span><span class="n">rand_load_file</span><span class="p">(</span><span class="n">six</span><span class="o">.</span><span class="n">ensure_str</span><span class="p">(</span><span class="n">filename</span><span class="p">),</span> <span class="n">max_bytes</span><span class="p">)</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="save_file"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.save_file">[docs]</a><span class="k">def</span> <span class="nf">save_file</span><span class="p">(</span><span class="n">filename</span><span class="p">):</span>
<span class="c1"># type: (AnyStr) -> int</span>
<span class="sd">"""</span>
<span class="sd"> Write a number of random bytes (currently 1024) to file.</span>
<span class="sd"> The file then can be used to initialize the PRNG by calling load_file() in</span>
<span class="sd"> a later session.</span>
<span class="sd"> :param filename:</span>
<span class="sd"> :return: returns the number of bytes written, and -1 if the bytes</span>
<span class="sd"> written were generated without appropriate seed.</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">m2</span><span class="o">.</span><span class="n">rand_save_file</span><span class="p">(</span><span class="n">filename</span><span class="p">)</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="rand_bytes"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.rand_bytes">[docs]</a><span class="k">def</span> <span class="nf">rand_bytes</span><span class="p">(</span><span class="n">num</span><span class="p">):</span>
<span class="c1"># type: (int) -> bytes</span>
<span class="sd">"""</span>
<span class="sd"> Return n cryptographically strong pseudo-random bytes.</span>
<span class="sd"> An error occurs if the PRNG has not been seeded with enough randomness</span>
<span class="sd"> to ensure an unpredictable byte sequence.</span>
<span class="sd"> :param num: number of bytes to be returned</span>
<span class="sd"> :return: random bytes</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">m2</span><span class="o">.</span><span class="n">rand_bytes</span><span class="p">(</span><span class="n">num</span><span class="p">)</span> <span class="c1"># pylint: disable=no-member</span></div>
<div class="viewcode-block" id="rand_pseudo_bytes"><a class="viewcode-back" href="../../M2Crypto.html#M2Crypto.Rand.rand_pseudo_bytes">[docs]</a><span class="k">def</span> <span class="nf">rand_pseudo_bytes</span><span class="p">(</span><span class="n">num</span><span class="p">):</span>
<span class="c1"># type: (int) -> Tuple[bytes, int]</span>
<span class="sd">"""</span>
<span class="sd"> Return num pseudo-random bytes into buf.</span>
<span class="sd"> Pseudo-random byte sequences generated by this method will be unique</span>
<span class="sd"> if they are of sufficient length, but are not necessarily</span>
<span class="sd"> unpredictable. They can be used for non-cryptographic purposes and for</span>
<span class="sd"> certain purposes in cryptographic protocols, but usually not for key</span>
<span class="sd"> generation etc.</span>
<span class="sd"> Output of the function is mixed into the entropy pool before</span>
<span class="sd"> retrieving the new pseudo-random bytes unless disabled at compile</span>
<span class="sd"> time (see FAQ).</span>
<span class="sd"> :param num: number of bytes to be returned</span>
<span class="sd"> :return: random bytes</span>
<span class="sd"> """</span>
<span class="kn">import</span> <span class="nn">warnings</span>
<span class="k">if</span> <span class="n">m2</span><span class="o">.</span><span class="n">OPENSSL_VERSION_NUMBER</span> <span class="o">>=</span> <span class="mh">0x10100000</span><span class="p">:</span>
<span class="n">warnings</span><span class="o">.</span><span class="n">warn</span><span class="p">(</span><span class="s1">'The underlying OpenSSL method has been '</span> <span class="o">+</span>
<span class="s1">'deprecated. Use Rand.rand_bytes instead.'</span><span class="p">,</span>
<span class="ne">DeprecationWarning</span><span class="p">)</span>
<span class="k">return</span> <span class="n">m2</span><span class="o">.</span><span class="n">rand_pseudo_bytes</span><span class="p">(</span><span class="n">num</span><span class="p">)</span> <span class="c1"># pylint: disable=no-member</span></div>
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