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Diffstat (limited to 'docs-xml/smbdotconf/logon/allownt4crypto.xml')
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1 files changed, 106 insertions, 0 deletions
diff --git a/docs-xml/smbdotconf/logon/allownt4crypto.xml b/docs-xml/smbdotconf/logon/allownt4crypto.xml new file mode 100644 index 0000000..ee63e6c --- /dev/null +++ b/docs-xml/smbdotconf/logon/allownt4crypto.xml @@ -0,0 +1,106 @@ +<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 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 + which worked fine with Samba versions up to 4.1.x. as the effective default + was "yes" there, while it is "no" now.</para> + + <para>If you have clients without RequireStrongKey = 1 in the registry, + you may need to set "allow nt4 crypto = yes", until you have fixed all clients. + </para> + + <para>"allow nt4 crypto = yes" allows weak crypto to be negotiated, maybe via downgrade attacks.</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 effective value of 'yes' from + the '<smbconfoption name="server reject md5 schannel:COMPUTERACCOUNT"/>' + and/or '<smbconfoption name="reject md5 clients"/>' options.</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 '$' sign). + </para> + + <para> + Samba will log a complaint in the log files at log level 0 + about the security problem if the option is set to "yes", + but the related computer does not require it. + (The log level can be adjusted with + '<smbconfoption name="CVE_2022_38023:warn_about_unused_debug_level">1</smbconfoption>' + in order to complain only at a higher log level). + </para> + + <para> + Samba will log a warning in the log files at log level 5, + if a setting is still needed for the specified computer account. + </para> + + <para> + See <ulink url="https://www.samba.org/samba/security/CVE-2022-38023.html">CVE-2022-38023</ulink>, + <ulink url="https://bugzilla.samba.org/show_bug.cgi?id=15240">https://bugzilla.samba.org/show_bug.cgi?id=15240</ulink>. + </para> + + <para>This option overrides the <smbconfoption name="allow nt4 crypto"/> option.</para> + + <para>This option is over-ridden by the effective value of 'yes' from + the '<smbconfoption name="server reject md5 schannel:COMPUTERACCOUNT"/>' + and/or '<smbconfoption name="reject md5 clients"/>' options.</para> + <para>Which means '<smbconfoption name="allow nt4 crypto:COMPUTERACCOUNT">yes</smbconfoption>' + is only useful in combination with '<smbconfoption name="server reject md5 schannel:COMPUTERACCOUNT">no</smbconfoption>'</para> + + <programlisting> + allow nt4 crypto:LEGACYCOMPUTER1$ = yes + server reject md5 schannel:LEGACYCOMPUTER1$ = no + allow nt4 crypto:NASBOX$ = yes + server reject md5 schannel:NASBOX$ = no + allow nt4 crypto:LEGACYCOMPUTER2$ = yes + server reject md5 schannel:LEGACYCOMPUTER2$ = no + </programlisting> +</description> + +</samba:parameter> |