Selinux denial on clamd

[Watts M.R.]

I'm currently trying to integrate Squid, c-icap and clamd together to get A/V scanning of objects through squid on a CentOS 6.5 server.

I have things working but every time I try and download the eicar.com test virus, I see the following in the logs:

type=AVC msg=audit(1410534437.751:227204): avc:  denied  { write } for  pid=22480 comm="clamd" path="/var/tmp/CI_TMP_DaewkQ" dev=dm-1 ino=182 scontext=unconfined_u:system_r:antivirus_t:s0 tcontext=unconfined_u:object_r:initrc_tmp_t:s0 tclass=file

For the record, this server has been hardened according to the CIS CentOS 6.5 benchmark document.

/tmp and /var/tmp are mounted as so, if this matters:

/dev/mapper/VolGroup00-tmp on /tmp type ext4 (rw,noexec,nosuid,nodev)
/tmp on /var/tmp type none (rw,noexec,nosuid,nodev,bind)

If I set "semanage permissive -a clamd_t" then everything works.

Audit2allow suggests I need the following, but I'm not really understanding why:

allow antivirus_t initrc_tmp_t:file write;

Any guidance?

Mark.

--
Mark Watts
Infrastructure Engineer, iSolutions
University of Southampton
Tel: [phone] Int: 25788

[Daniel J Walsh]

Does it not work without permissive mode?

Looks like a stdout redirection or leaked file descriptor.

Do you have something like

script << _EOF
command
command
comand
_EOF

Where clamd is running as one of the commands?

Or some other tmp file being created in /var/tmp/CI_TMP

Which is being passed on to clamd

On 09/12/2014 11:11 AM, Watts M.R. wrote:
> I’m currently trying to integrate Squid, c-icap and clamd together to
> get A/V scanning of objects through squid on a CentOS 6.5 server.
>
> I have things working but every time I try and download the eicar.com
> test virus, I see the following in the logs:
>
> type=AVC msg=audit(1410534437.751:227204): avc:  denied  { write }
> for  pid=22480 comm="clamd" path="/var/tmp/CI_TMP_DaewkQ" dev=dm-1
> ino=182 scontext=unconfined_u:system_r:antivirus_t:s0
> tcontext=unconfined_u:object_r:initrc_tmp_t:s0 tclass=file
>
> For the record, this server has been hardened according to the CIS
> CentOS 6.5 benchmark document.
>
> /tmp and /var/tmp are mounted as so, if this matters:
>
> /dev/mapper/VolGroup00-tmp on /tmp type ext4 (rw,noexec,nosuid,nodev)
>
> /tmp on /var/tmp type none (rw,noexec,nosuid,nodev,bind)
>
> If I set “semanage permissive -a clamd_t” then everything works.
>
> Audit2allow suggests I need the following, but I’m not really
> understanding why:
>
> allow antivirus_t initrc_tmp_t:file write;
>
> Any guidance?
>
> Mark.
>
> --
>
> Mark Watts
>
> Infrastructure Engineer, iSolutions
>
> University of Southampton
>
> Tel: [phone] Int: 25788
>
> --
> selinux mailing list
> [e-mail]
> https://admin.fedoraproject.org/mailman/listinfo/selinux

[Watts M.R.]

Data flow is:  Squid -> c-icap (via TCP) -> c-icap virus_scan module -> c-icap clamd_mod module

c-icap's TmpDir is set to /var/tmp so my guess is that its c-icap which is writing the object to scan to the CI_TMP file which it then passes to its virus_scan module which ultimately gets passed to clamd through the clamd_mod c-icap module. I can't tell this explicitly from the documentation at [1] though so this is just an educated guess.

Mark.

[1] http://c-icap.sourceforge.net/c-icap-modules.conf-0.3.x.html

--
Mark Watts
Infrastructure Engineer, iSolutions
University of Southampton
Tel: [phone] Int: 25788
________________________________
From: Daniel J Walsh [[e-mail]]
Sent: 13 September 2014 11:07
To: Watts M.R.; [e-mail]
Subject: Re: Selinux denial on clamd

Does it not work without permissive mode?

Looks like a stdout redirection or leaked file descriptor.

Do you have something like

script << _EOF
command
command
comand
_EOF

Where clamd is running as one of the commands?

Or some other tmp file being created in /var/tmp/CI_TMP

Which is being passed on to clamd

On 09/12/2014 11:11 AM, Watts M.R. wrote:
I’m currently trying to integrate Squid, c-icap and clamd together to get A/V scanning of objects through squid on a CentOS 6.5 server.

I have things working but every time I try and download the eicar.com test virus, I see the following in the logs:

type=AVC msg=audit(1410534437.751:227204): avc:  denied  { write } for  pid=22480 comm="clamd" path="/var/tmp/CI_TMP_DaewkQ" dev=dm-1 ino=182 scontext=unconfined_u:system_r:antivirus_t:s0 tcontext=unconfined_u:object_r:initrc_tmp_t:s0 tclass=file

For the record, this server has been hardened according to the CIS CentOS 6.5 benchmark document.

/tmp and /var/tmp are mounted as so, if this matters:

/dev/mapper/VolGroup00-tmp on /tmp type ext4 (rw,noexec,nosuid,nodev)
/tmp on /var/tmp type none (rw,noexec,nosuid,nodev,bind)

If I set “semanage permissive -a clamd_t” then everything works.

Audit2allow suggests I need the following, but I’m not really understanding why:

allow antivirus_t initrc_tmp_t:file write;

Any guidance?

Mark.

--
Mark Watts
Infrastructure Engineer, iSolutions
University of Southampton
Tel: [phone] Int: 25788

--
selinux mailing list
[e-mail]
https://admin.fedoraproject.org/mailman/listinfo/selinux

[Daniel J Walsh]

I would just allow the access, using audit2allow -M myclamd
On 09/13/2014 07:57 AM, Watts M.R. wrote:
> Data flow is:  Squid -> c-icap (via TCP) -> c-icap virus_scan module -> c-icap clamd_mod module
>
> c-icap's TmpDir is set to /var/tmp so my guess is that its c-icap which is writing the object to scan to the CI_TMP file which it then passes to its virus_scan module which ultimately gets passed to clamd through the clamd_mod c-icap module. I can't tell this explicitly from the documentation at [1] though so this is just an educated guess.
>
> Mark.
>
> [1] http://c-icap.sourceforge.net/c-icap-modules.conf-0.3.x.html
>
> --
> Mark Watts
> Infrastructure Engineer, iSolutions
> University of Southampton
> Tel: [phone] Int: 25788
> ________________________________
> From: Daniel J Walsh [[e-mail]]
> Sent: 13 September 2014 11:07
> To: Watts M.R.; [e-mail]
> Subject: Re: Selinux denial on clamd
>
> Does it not work without permissive mode?
>
> Looks like a stdout redirection or leaked file descriptor.
>
> Do you have something like
>
> script << _EOF
> command
> command
> comand
> _EOF
>
> Where clamd is running as one of the commands?
>
> Or some other tmp file being created in /var/tmp/CI_TMP
>
> Which is being passed on to clamd
>
> On 09/12/2014 11:11 AM, Watts M.R. wrote:
> I’m currently trying to integrate Squid, c-icap and clamd together to get A/V scanning of objects through squid on a CentOS 6.5 server.
>
> I have things working but every time I try and download the eicar.com test virus, I see the following in the logs:
>
> type=AVC msg=audit(1410534437.751:227204): avc:  denied  { write } for  pid=22480 comm="clamd" path="/var/tmp/CI_TMP_DaewkQ" dev=dm-1 ino=182 scontext=unconfined_u:system_r:antivirus_t:s0 tcontext=unconfined_u:object_r:initrc_tmp_t:s0 tclass=file
>
> For the record, this server has been hardened according to the CIS CentOS 6.5 benchmark document.
>
> /tmp and /var/tmp are mounted as so, if this matters:
>
> /dev/mapper/VolGroup00-tmp on /tmp type ext4 (rw,noexec,nosuid,nodev)
> /tmp on /var/tmp type none (rw,noexec,nosuid,nodev,bind)
>
> If I set “semanage permissive -a clamd_t” then everything works.
>
> Audit2allow suggests I need the following, but I’m not really understanding why:
>
> allow antivirus_t initrc_tmp_t:file write;
>
> Any guidance?
>
> Mark.
>
> --
> Mark Watts
> Infrastructure Engineer, iSolutions
> University of Southampton
> Tel: [phone] Int: 25788
>
> --
> selinux mailing list
> [e-mail]
> https://admin.fedoraproject.org/mailman/listinfo/selinux
>
> --
> selinux mailing list
> [e-mail]
> https://admin.fedoraproject.org/mailman/listinfo/selinux