Sendmail milters in Fedora 8
Daniel J Walsh
dwalsh at redhat.com
Tue Jan 15 19:53:18 UTC 2008
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Paul Howarth wrote:
> Daniel J Walsh wrote:
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>> Paul Howarth wrote:
>>> Daniel J Walsh wrote:
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>>>> Paul Howarth wrote:
>>>>> Hi Dan,
>>>>>
>>>>> Daniel J Walsh wrote:
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>>>>>> Paul Howarth wrote:
>>>>>>> Paul Howarth wrote:
>>>>>>>> Since upgrading my mail server from Fedora 7 to Fedora 8, I've come
>>>>>>>> across some problems with the sockets used for communication
>>>>>>>> between
>>>>>>>> sendmail and two of the "milter" plugins I'm using with it, namely
>>>>>>>> milter-regex and spamass-milter. It's very likely that other
>>>>>>>> milters
>>>>>>>> will have similar issues.
>>>>>>>>
>>>>>>>> The sockets used are created when the milter starts, as follows:
>>>>>>>>
>>>>>>>> milter-regex:
>>>>>>>> /var/spool/milter-regex/sock (var_spool_t, inherited from parent
>>>>>>>> directory)
>>>>>>>>
>>>>>>>> spamass-milter:
>>>>>>>> /var/run/spamass-milter/spamass-milter.sock (spamd_var_run_t, in
>>>>>>>> policy)
>>>>>>>>
>>>>>>>> These are pretty well the upstream locations, though I'm open to
>>>>>>>> moving the milter-regex socket from /var/spool to /var/run or
>>>>>>>> elsewhere for consistency.
>>>>>>>>
>>>>>>>> Since moving to Fedora 8, I've had to add the following to local
>>>>>>>> policy to get these milters working:
>>>>>>>>
>>>>>>>> allow sendmail_t spamd_var_run_t:dir { search getattr };
>>>>>>>> allow sendmail_t spamd_var_run_t:sock_file { getattr write };
>>>>>>>> allow sendmail_t var_spool_t:sock_file { getattr write };
>>>>>>>> allow sendmail_t initrc_t:unix_stream_socket { read write
>>>>>>>> connectto };
>>>>>>>>
>>>>>>>> The last of these is the strangest, and relates to Bug #425958
>>>>>>>> (https://bugzilla.redhat.com/show_bug.cgi?id=425958). Whilst the
>>>>>>>> socket file itself has the context listed above, the unix domain
>>>>>>>> socket that sendmail connects to is still initrc_t, as can be seen
>>>>>>>> from the output of "netstat -lpZ":
>>>>>>>>
>>>>>>>> ...
>>>>>>>> unix 2 [ ACC ] STREAM LISTENING 14142
>>>>>>>> 5853/spamass-milter system_u:system_r:initrc_t:s0
>>>>>>>> /var/run/spamass-milter/spamass-milter.sock
>>>>>>>> unix 2 [ ACC ] STREAM LISTENING 13794
>>>>>>>> 5779/milter-regex system_u:system_r:initrc_t:s0
>>>>>>>> /var/spool/milter-regex/sock
>>>>>>>> ...
>>>>>>>>
>>>>>>>> So, my questions are:
>>>>>>>>
>>>>>>>> 1. Why are the sockets still initrc_t?
>>>>>>>> 2. Is this a kernel issue or a userspace issue that should be
>>>>>>>> fixed in
>>>>>>>> the milters?
>>>>>>>> 3. Should there be a standard place for milter sockets to live,
>>>>>>>> and if
>>>>>>>> so, where?
>>>>>>>> 4. How come this worked OK in Fedora 7 and previous releases?
>>>>>>> Looking at the source code for these applications, I see that
>>>>>>> both of
>>>>>>> them use the smfi_setconn() function in the sendmail milter
>>>>>>> library to
>>>>>>> set up the sockets. It's therefore likely that this problem is
>>>>>>> common to
>>>>>>> all milter applications that use unix domain sockets.
>>>>>>>
>>>>>>> I'm now of the opinion that moving the directory locations for these
>>>>>>> sockets is a bad idea - it would need corresponding changes in
>>>>>>> people's
>>>>>>> sendmail configuration files, which would lead to problems for
>>>>>>> people
>>>>>>> doing package updates, or installing from upstream sources. Setting
>>>>>>> different context types for the directories (e.g. make
>>>>>>> /var/spool/milter-regex spamd_var_run_t) would seem a better option,
>>>>>>> along with policy tweaks to allow sendmail to do the permissions
>>>>>>> checks
>>>>>>> and write to the sockets).
>>>>>>>
>>>>>>> I'm still confused about the initrc_t sockets though.
>>>>>>>
>>>>>>> Paul.
>>>>>>>
>>>>>>> --
>>>>>>> fedora-selinux-list mailing list
>>>>>>> fedora-selinux-list at redhat.com
>>>>>>> https://www.redhat.com/mailman/listinfo/fedora-selinux-list
>>>>>> Ok I will add this to the next update.
>>>>> What exactly is "this"? The 4 "allow" rules mentioned above, the
>>>>> context
>>>>> type change for /var/spool/milter-regex mentioned later, both?
>>>>>
>>>>> Cheers, Paul.
>>>>>
>>>> Context change for /var/spool/milter-regex to spamd_var_run_t.
>>>> sendmail
>>>> can already use sockets in this directory.
>>> So that includes the:
>>>
>>> allow sendmail_t initrc_t:unix_stream_socket { read write connectto }
>>>
>>> ?
>>>
>>> Cheers, Paul.
>>>
>> Nope. I don't know what is running as initrc_t and I would bet this is
>> a leaked file descriptor. Or at least a redirectiron of stdin/stdout.
>
> I don't think it's a leaked file descriptor - that would be
> dontaudit-able, right? By not allowing communications with the
> initrc_t:unix_stream_socket, the milter fails to work:
>
> ==> /var/log/audit/audit.log <==
> type=AVC msg=audit(1200408212.783:142453): avc: denied { connectto }
> for pid=7805 comm="sendmail" path="/var/spool/milter-regex/sock"
> scontext=system_u:system_r:sendmail_t:s0
> tcontext=system_u:system_r:initrc_t:s0 tclass=unix_stream_socket
> type=SYSCALL msg=audit(1200408212.783:142453): arch=40000003 syscall=102
> success=no exit=-13 a0=3 a1=bfd9f600 a2=b7f79bd4 a3=0 items=0 ppid=7764
> pid=7805 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=51 sgid=51
> fsgid=51 tty=(none) comm="sendmail" exe="/usr/sbin/sendmail.sendmail"
> subj=system_u:system_r:sendmail_t:s0 key=(null)
>
> ==> /var/log/maillog <==
> Jan 15 14:43:32 goalkeeper sendmail[7805]: NOQUEUE: connect from
> ard120.neoplus.adsl.tpnet.pl [83.26.189.120]
> Jan 15 14:43:32 goalkeeper sendmail[7805]: AUTH: available mech=CRAM-MD5
> DIGEST-MD5, allowed mech=CRAM-MD5 DIGEST-MD5 LOGIN PLAIN
> Jan 15 14:43:32 goalkeeper sendmail[7805]: m0FEhW21007805: Milter
> (milter-regex): error connecting to filter: Permission denied
> Jan 15 14:43:32 goalkeeper sendmail[7805]: m0FEhW21007805: Milter
> (milter-regex): to error state
> Jan 15 14:43:32 goalkeeper sendmail[7805]: m0FEhW21007805: Milter:
> initialization failed, temp failing commands
> Jan 15 14:43:32 goalkeeper sendmail[7805]: m0FEhW21007805: SMTP MAIL
> command (<pathrusim at zombanewmedia.com>) from
> ard120.neoplus.adsl.tpnet.pl [83.26.189.120] tempfailed (due to previous
> checks)
>
>
> The initrc_t type shows up in netstat but not in ls:
> # netstat -aZp | grep initrc
> tcp 0 0 goalkeeper.intra.:bacula-fd *:* LISTEN
> 5864/bacula-fd system_u:system_r:initrc_t:s0
> udp 0 0 rbldns.intra.cit:domain *:*
> 5885/rbldnsd system_u:system_r:initrc_t:s0
> unix 2 [ ACC ] STREAM LISTENING 14142
> 5853/spamass-milter system_u:system_r:initrc_t:s0
> /var/run/spamass-milter/spamass-milter.sock
> unix 2 [ ACC ] STREAM LISTENING 13794
> 5779/milter-regex system_u:system_r:initrc_t:s0
> /var/spool/milter-regex/sock
> unix 2 [ ] DGRAM 2150436
> 5779/milter-regex system_u:system_r:initrc_t:s0
> unix 2 [ ] DGRAM 14141
> 5853/spamass-milter system_u:system_r:initrc_t:s0
> # ls -lZ /var/run/spamass-milter/spamass-milter.sock
> /var/spool/milter-regex/sock
> srwxr-xr-x sa-milt sa-milt system_u:object_r:spamd_var_run_t:s0
> /var/run/spamass-milter/spamass-milter.sock
> srw------- mregex mregex system_u:object_r:spamd_var_run_t:s0
> /var/spool/milter-regex/sock
>
>
> Paul.
>
>
Ok then I guess we need to label
chcon -t spamd_exec_t /usr/sbin/spamass-milter
And then build policy off of that.
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