CVE-2022-38023 docs-xml/smbdotconf: document "allow nt4 crypto:COMPUTERACCOUNT = no"

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15240

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
(cherry picked from commit bd429d025981b445bf63935063e8e302bfab3f9b)

1 files changed, 74 insertions, 2 deletions

diff --git a/docs-xml/smbdotconf/logon/allownt4crypto.xml b/docs-xml/smbdotconf/logon/allownt4crypto.xml
index 06afcef73b1..bbd03a42db7 100644
--- a/docs-xml/smbdotconf/logon/allownt4crypto.xml
+++ b/docs-xml/smbdotconf/logon/allownt4crypto.xml
@@ -1,11 +1,18 @@
 <samba:parameter name="allow nt4 crypto"
                  context="G"
                  type="boolean"
+                 deprecated="1"
                  xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
 <description>
+	<para>
+	This option is deprecated and will be removed in future,
+	as it is a security problem if not set to "no" (which will be
+	the hardcoded behavior in future).
+	</para>
+
 	<para>This option controls whether the netlogon server (currently
 	only in 'active directory domain controller' mode), will
-	reject clients which does not support NETLOGON_NEG_STRONG_KEYS
+	reject clients which do not support NETLOGON_NEG_STRONG_KEYS
 	nor NETLOGON_NEG_SUPPORTS_AES.</para>
 
 	<para>This option was added with Samba 4.2.0. It may lock out clients
@@ -18,8 +25,73 @@
 
 	<para>"allow nt4 crypto = yes" allows weak crypto to be negotiated, maybe via downgrade attacks.</para>
 
-	<para>This option is over-ridden by the 'reject md5 clients' option.</para>
+	<para><emphasis>Avoid using this option!</emphasis> Use explicit '<smbconfoption name="allow nt4 crypto:COMPUTERACCOUNT">yes</smbconfoption>' instead!
+	Which is available with the patches for
+	<ulink url="https://www.samba.org/samba/security/CVE-2022-38023.html">CVE-2022-38023</ulink>
+	see <ulink url="https://bugzilla.samba.org/show_bug.cgi?id=15240">https://bugzilla.samba.org/show_bug.cgi?id=15240</ulink></para>
+
+	<para>
+	Samba will log an error in the log files at log level 0
+	if legacy a client is rejected or allowed without an explicit,
+	'<smbconfoption name="allow nt4 crypto:COMPUTERACCOUNT">yes</smbconfoption>' option
+	for the client. The message will indicate
+	the explicit '<smbconfoption name="allow nt4 crypto:COMPUTERACCOUNT">yes</smbconfoption>'
+	line to be added, if the legacy client software requires it. (The log level can be adjusted with
+	'<smbconfoption name="CVE_2022_38023:error_debug_level">1</smbconfoption>'
+	in order to complain only at a higher log level).
+	</para>
+
+	<para>This allows admins to use "yes" only for a short grace period,
+	in order to collect the explicit
+	'<smbconfoption name="allow nt4 crypto:COMPUTERACCOUNT">yes</smbconfoption>' options.</para>
+
+	<para>This option is over-ridden by the '<smbconfoption name="reject md5 clients">yes</smbconfoption>' option.</para>
 </description>
 
 <value type="default">no</value>
 </samba:parameter>
+
+<samba:parameter name="allow nt4 crypto:COMPUTERACCOUNT"
+                 context="G"
+                 type="string"
+                 xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
+<description>
+
+    <para>If you still have legacy domain members which required 'allow nt4 crypto = yes',
+	it is possible to specify an explicit exception per computer account
+	by using 'allow nt4 crypto:COMPUTERACCOUNT = yes' as option.
+	Note that COMPUTERACCOUNT has to be the sAMAccountName value of
+	the computer account (including the trailing '$' sign).
+    </para>
+
+    <para>
+	Samba will log a complaint in the log files at log level 0
+	about the security problem if the option is set to "yes",
+	but the related computer does not require it.
+	(The log level can be adjusted with
+	'<smbconfoption name="CVE_2022_38023:warn_about_unused_debug_level">1</smbconfoption>'
+	in order to complain only at a higher log level).
+    </para>
+
+    <para>
+	Samba will log a warning in the log files at log level 5,
+	if a setting is still needed for the specified computer account.
+    </para>
+
+    <para>
+	See <ulink url="https://www.samba.org/samba/security/CVE-2022-38023.html">CVE-2022-38023</ulink>,
+	<ulink url="https://bugzilla.samba.org/show_bug.cgi?id=15240">https://bugzilla.samba.org/show_bug.cgi?id=15240</ulink>.
+    </para>
+
+    <para>This option overrides the <smbconfoption name="allow nt4 crypto"/> option.</para>
+
+    <para>This option is over-ridden by the '<smbconfoption name="reject md5 clients">yes</smbconfoption>' option.</para>
+
+    <programlisting>
+	allow nt4 crypto:LEGACYCOMPUTER1$ = yes
+	allow nt4 crypto:NASBOX$ = yes
+	allow nt4 crypto:LEGACYCOMPUTER2$ = yes
+    </programlisting>
+</description>
+
+</samba:parameter>