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Trying to keep SElinux Enforced on CentOS and allowing clamAV to scan files. But it seems that SElinux does not like the following behavior of clamd:

Clamd is listening on a predefined TCP port then use random TCP ports to exchange the files to check with the client

in short... Each file getting scanned open a new port.

Disabling SElinux everything works fine, so definitely is a SElinux policy related issue.

With SElinux enabled and enforced clamd encounter the following issue:

● clamd.service - clamd scanner () daemon
   Loaded: loaded (/usr/lib/systemd/system/clamd.service; static; vendor preset: disabled)
   Active: active (running) since Thu 2017-06-22 15:56:57 CEST; 27min ago
 Main PID: 3671 (clamd)
   CGroup: /system.slice/clamd.service
           └─3671 /usr/sbin/clamd -c /etc/clamd.d/scan.conf --foreground=yes
Jun 22 15:57:06 prd-app-srv clamd[3671]: HWP3 support enabled.
Jun 22 15:57:06 prd-app-srv clamd[3671]: Self checking every 600 seconds.
Jun 22 15:58:05 prd-app-srv clamd[3671]: ScanStream: Can't find any free port.
Jun 22 15:58:05 prd-app-srv clamd[3671]: ERROR: ScanStream: Can't find any free port.
Jun 22 16:08:05 prd-app-srv clamd[3671]: SelfCheck: Database status OK.
Jun 22 16:08:05 prd-app-srv clamd[3671]: SelfCheck: Database status OK.
Jun 22 16:08:24 prd-app-srv clamd[3671]: ERROR: ScanStream: Can't find any free port.
Jun 22 16:08:24 prd-app-srv clamd[3671]: ScanStream: Can't find any free port.
Jun 22 16:18:24 prd-app-srv clamd[3671]: SelfCheck: Database status OK.
Jun 22 16:18:24 prd-app-srv clamd[3671]: SelfCheck: Database status OK.

In /var/log/audit/audit.log I find following logs entries:

type=AVC msg=audit(1498156946.689:4165): avc:  denied  { name_bind } for  pid=4086 comm="clamd" src=30860 scontext=system_u:system_r:antivirus_t:s0 tcontext=system_u:object_r:unreserved_port_t:s0 tclass=tcp_socket
type=SYSCALL msg=audit(1498156946.689:4165): arch=c000003e syscall=49 success=no exit=-13 a0=b a1=7fdc8fc31a90 a2=10 a3=1f items=0 ppid=1 pid=4086 auid=4294967295 uid=995 gid=994 euid=995 suid=995 fsuid=995 egid=994 sgid=994 fsgid=994 tty=(none) ses=4294967295 comm="clamd" exe="/usr/sbin/clamd" subj=system_u:system_r:antivirus_t:s0 key=(null)

this seems to be closely related: https://bugzilla.redhat.com/show_bug.cgi?id=1248785

Anyone knows a selinux policy which will block a service to opens all the ports it wants?

I would like to leave SElinux enabled and enforced, and solve the issue in the less invasive manner

1 Answer 1

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Solved by defining the ports range that clamd use, into /etc/clamd.d/scan.conf

StreamingMinPort 30000
StreamingMaxPort 32000

and by reflecting the same ports range in selinux policy

semanage port -a -t clamd_port_t -p tcp 30000-32000

Anyone knows a cleaner, or less invasive way to manage the issue?

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