CVE-2022-38023 docs-xml/smbdotconf: add "server schannel require seal[:COMPUTERACCOUN...

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>

diff --git a/docs-xml/smbdotconf/security/serverschannel.xml b/docs-xml/smbdotconf/security/serverschannel.xml
index 394ffdc36fbd86abd3f4a0d103376345e09eebd2..5c69f0f64dfbcd64d996bc0256e7a080c1abe2d3 100644 (file)
--- a/docs-xml/smbdotconf/security/serverschannel.xml
+++ b/docs-xml/smbdotconf/security/serverschannel.xml
@@ -12,19 +12,37 @@
        the hardcoded behavior in future).
     </para>
 
-    <para>
-       Samba will complain in the log files at log level 0,
-       about the security problem if the option is not set to "yes".
+    <para><emphasis>Avoid using this option!</emphasis> Use explicit '<smbconfoption name="server require schannel:COMPUTERACCOUNT">no</smbconfoption>' instead!
     </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="server require schannel:COMPUTERACCOUNT">no</smbconfoption>' option
+       for the client. The message will indicate
+       the explicit '<smbconfoption name="server require schannel:COMPUTERACCOUNT">no</smbconfoption>'
+       line to be added, if the legacy client software requires it. (The log level can be adjusted with
+       '<smbconfoption name="CVE_2020_1472:error_debug_level">1</smbconfoption>'
+       in order to complain only at a higher log level).
+       </para>
+
     <para>
-       See CVE-2020-1472(ZeroLogon) https://bugzilla.samba.org/show_bug.cgi?id=14497
+       This allows admins to use "auto" only for a short grace period,
+       in order to collect the explicit
+       '<smbconfoption name="server require schannel:COMPUTERACCOUNT">no</smbconfoption>' options.
     </para>
 
-    <para>If you still have legacy domain members use the <smbconfoption name="server require schannel:COMPUTERACCOUNT"/> option.
+    <para>
+       See <ulink url="https://www.samba.org/samba/security/CVE-2020-1472.html">CVE-2020-1472(ZeroLogon)</ulink>,
+       <ulink url="https://bugzilla.samba.org/show_bug.cgi?id=14497">https://bugzilla.samba.org/show_bug.cgi?id=14497</ulink>.
     </para>
 
     <para>This option is over-ridden by the <smbconfoption name="server require schannel:COMPUTERACCOUNT"/> option.</para>
 
+    <para>This option is over-ridden by the effective value of 'yes' from
+    the '<smbconfoption name="server schannel require seal:COMPUTERACCOUNT"/>'
+    and/or '<smbconfoption name="server schannel require seal"/>' options.</para>
+
 </description>
 
 <value type="default">yes</value>
@@ -48,6 +66,9 @@
        about the security problem if the option is not set to "no",
        but the related computer is actually using the netlogon
        secure channel (schannel) feature.
+       (The log level can be adjusted with
+       '<smbconfoption name="CVE_2020_1472:warn_about_unused_debug_level">1</smbconfoption>'
+       in order to complain only at a higher log level).
     </para>
 
     <para>
@@ -56,15 +77,25 @@
     </para>
 
     <para>
-       See CVE-2020-1472(ZeroLogon) https://bugzilla.samba.org/show_bug.cgi?id=14497
+       See <ulink url="https://www.samba.org/samba/security/CVE-2020-1472.html">CVE-2020-1472(ZeroLogon)</ulink>,
+       <ulink url="https://bugzilla.samba.org/show_bug.cgi?id=14497">https://bugzilla.samba.org/show_bug.cgi?id=14497</ulink>.
     </para>
 
     <para>This option overrides the <smbconfoption name="server schannel"/> option.</para>
 
+    <para>This option is over-ridden by the effective value of 'yes' from
+    the '<smbconfoption name="server schannel require seal:COMPUTERACCOUNT"/>'
+    and/or '<smbconfoption name="server schannel require seal"/>' options.</para>
+    <para>Which means '<smbconfoption name="server require schannel:COMPUTERACCOUNT">no</smbconfoption>'
+    is only useful in combination with '<smbconfoption name="server schannel require seal:COMPUTERACCOUNT">no</smbconfoption>'</para>
+
     <programlisting>
        server require schannel:LEGACYCOMPUTER1$ = no
+       server require schannel seal:LEGACYCOMPUTER1$ = no
        server require schannel:NASBOX$ = no
+       server require schannel seal:NASBOX$ = no
        server require schannel:LEGACYCOMPUTER2$ = no
+       server require schannel seal:LEGACYCOMPUTER2$ = no
     </programlisting>
 </description>
 

diff --git a/docs-xml/smbdotconf/security/serverschannelrequireseal.xml b/docs-xml/smbdotconf/security/serverschannelrequireseal.xml
new file mode 100644 (file)
index 0000000..d4620d1
--- /dev/null
+++ b/docs-xml/smbdotconf/security/serverschannelrequireseal.xml
@@ -0,0 +1,118 @@
+<samba:parameter name="server schannel require seal"
+                 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 "yes" (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 the usage of netlogon secure channel without privacy/enryption.
+       </para>
+
+       <para>
+       The option is modelled after the registry key available on Windows.
+       </para>
+
+       <programlisting>
+       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\RequireSeal=2
+       </programlisting>
+
+       <para>
+       <emphasis>Avoid using this option!</emphasis> Use the per computer account specific option
+       '<smbconfoption name="server schannel require seal:COMPUTERACCOUNT"/>' 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="server schannel require seal:COMPUTERACCOUNT">no</smbconfoption>' option
+       for the client. The message will indicate
+       the explicit '<smbconfoption name="server schannel require seal:COMPUTERACCOUNT">no</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 "no" only for a short grace period,
+       in order to collect the explicit
+       '<smbconfoption name="server schannel require seal:COMPUTERACCOUNT">no</smbconfoption>' options.</para>
+
+       <para>
+       When set to 'yes' this option overrides the
+       '<smbconfoption name="server require schannel:COMPUTERACCOUNT"/>' and
+       '<smbconfoption name="server schannel"/>' options and implies
+       '<smbconfoption name="server require schannel:COMPUTERACCOUNT">yes</smbconfoption>'.
+       </para>
+
+       <para>
+       This option is over-ridden by the <smbconfoption name="server schannel require seal:COMPUTERACCOUNT"/> option.
+       </para>
+
+</description>
+
+<value type="default">yes</value>
+</samba:parameter>
+
+<samba:parameter name="server schannel require seal: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 "server schannel require seal = no" before,
+       it is possible to specify explicit exception per computer account
+       by using 'server schannel require seal:COMPUTERACCOUNT = no' as option.
+       Note that COMPUTERACCOUNT has to be the sAMAccountName value of
+       the computer account (including the trailing '$' sign).
+       </para>
+
+       <para>
+       Samba will log a complaint in the log files at log level 0
+       about the security problem if the option is set to "no",
+       but the related computer does not require it.
+       (The log level can be adjusted with
+       '<smbconfoption name="CVE_2022_38023:warn_about_unused_debug_level">1</smbconfoption>'
+       in order to complain only at a higher log level).
+       </para>
+
+       <para>
+       Samba will warn in the log files at log level 5,
+       if a setting is still needed for the specified computer account.
+       </para>
+
+       <para>
+       See <ulink url="https://www.samba.org/samba/security/CVE-2022-38023.html">CVE-2022-38023</ulink>,
+       <ulink url="https://bugzilla.samba.org/show_bug.cgi?id=15240">https://bugzilla.samba.org/show_bug.cgi?id=15240</ulink>.
+       </para>
+
+       <para>
+       This option overrides the '<smbconfoption name="server schannel require seal"/>' option.
+       </para>
+
+       <para>
+       When set to 'yes' this option overrides the
+       '<smbconfoption name="server require schannel:COMPUTERACCOUNT"/>' and
+       '<smbconfoption name="server schannel"/>' options and implies
+       '<smbconfoption name="server require schannel:COMPUTERACCOUNT">yes</smbconfoption>'.
+       </para>
+
+       <programlisting>
+       server require schannel seal:LEGACYCOMPUTER1$ = no
+       server require schannel seal:NASBOX$ = no
+       server require schannel seal:LEGACYCOMPUTER2$ = no
+       </programlisting>
+</description>
+
+</samba:parameter>

diff --git a/lib/param/loadparm.c b/lib/param/loadparm.c
index e509cf85bb89716865ec44f76da51f5a606dd9e7..1dcc8061fa2198e7c834d16e38af6dd066887514 100644 (file)
--- a/lib/param/loadparm.c
+++ b/lib/param/loadparm.c
@@ -2729,6 +2729,7 @@ struct loadparm_context *loadparm_init(TALLOC_CTX *mem_ctx)
        lpcfg_do_global_parameter(lp_ctx, "winbind nss info", "template");
 
        lpcfg_do_global_parameter(lp_ctx, "server schannel", "True");
+       lpcfg_do_global_parameter(lp_ctx, "server schannel require seal", "True");
        lpcfg_do_global_parameter(lp_ctx, "reject md5 clients", "True");
 
        lpcfg_do_global_parameter(lp_ctx, "short preserve case", "True");

diff --git a/source3/param/loadparm.c b/source3/param/loadparm.c
index 336852b927cbe9f43bdf86764dbc74236581355a..a0c9249b77704bd11f96f396be7a3db329a9cf0e 100644 (file)
--- a/source3/param/loadparm.c
+++ b/source3/param/loadparm.c
@@ -666,6 +666,7 @@ static void init_globals(struct loadparm_context *lp_ctx, bool reinit_globals)
        Globals.require_strong_key = true;
        Globals.reject_md5_servers = true;
        Globals.server_schannel = true;
+       Globals.server_schannel_require_seal = true;
        Globals.reject_md5_clients = true;
        Globals.read_raw = true;
        Globals.write_raw = true;