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Bug 2133221 - SELINUX policy denies net-snmp's bind to TLS/DTLS port 10161
Summary: SELINUX policy denies net-snmp's bind to TLS/DTLS port 10161
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: selinux-policy
Version: 9.2
Hardware: All
OS: Linux
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Nikola Knazekova
QA Contact: Milos Malik
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-10-08 21:35 UTC by Graham Leggett
Modified: 2023-05-09 10:20 UTC (History)
3 users (show)

Fixed In Version: selinux-policy-34.1.44-1.el9
Doc Type: Bug Fix
Doc Text:
Cause: Simple Network Management Protocol over TLS and DTLS uses 10161-10162 ports. Consequence: SELinux denied snmpd name connect to unreserved_port_t Fix: Label ports 10161-10162 tcp/udp with snmp and allow name_connect to these ports Result: No denials
Clone Of:
Environment:
Last Closed: 2023-05-09 08:16:52 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Github fedora-selinux selinux-policy pull 1439 0 None Merged Label ports 10161-10162 tcp/udp with snmp 2022-10-12 09:06:34 UTC
Red Hat Issue Tracker RHELPLAN-135985 0 None None None 2022-10-08 21:36:10 UTC
Red Hat Product Errata RHBA-2023:2483 0 None None None 2023-05-09 08:17:08 UTC

Description Graham Leggett 2022-10-08 21:35:29 UTC 
Description of problem:

net-snmp cannot enable TLS, SELINUX forbids it.

Version-Release number of selected component (if applicable):

net-snmp-5.9.1-7.el9_0.1.x86_64

How reproducible:

Always

Steps to Reproduce:
1. Enable TLS in /etc/snmpd.conf as follows:

agentaddress dtlsudp:10161,dtlsudp:[::]:10161
[snmp] localCert snmpd
[snmp] trustCert ssl-cacert

Actual results:

net-snmp fails to start:

Oct 08 23:19:58 seawitch snmpd[9384]: Cannot bind for clientaddr: Permission denied
Oct 08 23:19:58 seawitch snmpd[9384]: Error opening specified endpoint "dtlsudp:10161"
Oct 08 23:19:58 seawitch snmpd[9384]: Server Exiting with code 1
Oct 08 23:19:58 seawitch systemd[1]: snmpd.service: Main process exited, code=exited, status=1/FAILURE

Reason, selinux denied:

type=AVC msg=audit(1665263998.057:1053): avc:  denied  { name_bind } for  pid=9384 comm="snmpd" src=10161 scontext=system_u:system_r:snmpd_t:s0 tcontext=system_u:object_r:unreserved_port_t:s0 tclass=udp_socket permissive=0

Expected results:

snmpd starts normally.

Additional info:

Workaround: disable selinux (yuck)
Comment 1 Josef Ridky 2022-10-11 07:54:55 UTC 
Hi Graham,

have you tried to use semanage command to open that port for net-snmp?
By default, net-snmp is allowed to bind to ports 161-162 (udp) and 199, 1161, 161-162 (tcp).

To add new port use semanage command (as root/sudo user) as follows:

# semanage port -a -t snmp_port_t -p udp 10161

Let me know, if it resolves your issue.

Josef
Comment 2 Graham Leggett 2022-10-11 09:34:11 UTC 
Ports 10161 and 10162 are IANA assigned ports for secure SNMP.

https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=53&page=4

Manually fiddling with semanage should not be necessary, and secure operation should be default behaviour.

Please fix this.
Comment 5 Milos Malik 2022-10-11 11:48:46 UTC 
Caught in enforcing mode:
----
type=PROCTITLE msg=audit(10/11/2022 07:45:56.892:319) : proctitle=/usr/sbin/snmpd -LS0-6d -f 
type=SOCKADDR msg=audit(10/11/2022 07:45:56.892:319) : saddr={ saddr_fam=inet laddr=127.0.0.1 lport=10161 } 
type=SYSCALL msg=audit(10/11/2022 07:45:56.892:319) : arch=x86_64 syscall=bind success=no exit=EACCES(Permission denied) a0=0x7 a1=0x7ffd9a31f8d0 a2=0x10 a3=0x7ffd9a31f78c items=0 ppid=1 pid=15568 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=snmpd exe=/usr/sbin/snmpd subj=system_u:system_r:snmpd_t:s0 key=(null) 
type=AVC msg=audit(10/11/2022 07:45:56.892:319) : avc:  denied  { name_bind } for  pid=15568 comm=snmpd src=10161 scontext=system_u:system_r:snmpd_t:s0 tcontext=system_u:object_r:unreserved_port_t:s0 tclass=udp_socket permissive=0 
----
type=PROCTITLE msg=audit(10/11/2022 07:45:56.892:320) : proctitle=/usr/sbin/snmpd -LS0-6d -f 
type=SOCKADDR msg=audit(10/11/2022 07:45:56.892:320) : saddr={ saddr_fam=inet6 laddr=::1 lport=10161 } 
type=SYSCALL msg=audit(10/11/2022 07:45:56.892:320) : arch=x86_64 syscall=bind success=no exit=EACCES(Permission denied) a0=0x7 a1=0x7ffd9a31f8e0 a2=0x1c a3=0x7ffd9a31f7f4 items=0 ppid=1 pid=15568 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=snmpd exe=/usr/sbin/snmpd subj=system_u:system_r:snmpd_t:s0 key=(null) 
type=AVC msg=audit(10/11/2022 07:45:56.892:320) : avc:  denied  { name_bind } for  pid=15568 comm=snmpd src=10161 scontext=system_u:system_r:snmpd_t:s0 tcontext=system_u:object_r:unreserved_port_t:s0 tclass=udp_socket permissive=0 
----

# rpm -qa selinux\* net-snmp\* | sort
net-snmp-5.9.1-7.el9_0.1.x86_64
net-snmp-agent-libs-5.9.1-7.el9_0.1.x86_64
net-snmp-libs-5.9.1-7.el9_0.1.x86_64
selinux-policy-34.1.43-1.el9.noarch
selinux-policy-targeted-34.1.43-1.el9.noarch
# grep agentaddress /etc/snmp/snmpd.conf 
agentaddress localhost:10161,localhost:[::]:10161
#
Comment 6 Milos Malik 2022-10-11 11:51:21 UTC 
Caught in permissive mode:
----
type=PROCTITLE msg=audit(10/11/2022 07:49:39.168:323) : proctitle=/usr/sbin/snmpd -LS0-6d -f 
type=SOCKADDR msg=audit(10/11/2022 07:49:39.168:323) : saddr={ saddr_fam=inet laddr=127.0.0.1 lport=10161 } 
type=SYSCALL msg=audit(10/11/2022 07:49:39.168:323) : arch=x86_64 syscall=bind success=yes exit=0 a0=0x7 a1=0x7ffc8b73f4e0 a2=0x10 a3=0x7ffc8b73f39c items=0 ppid=1 pid=15608 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=snmpd exe=/usr/sbin/snmpd subj=system_u:system_r:snmpd_t:s0 key=(null) 
type=AVC msg=audit(10/11/2022 07:49:39.168:323) : avc:  denied  { name_bind } for  pid=15608 comm=snmpd src=10161 scontext=system_u:system_r:snmpd_t:s0 tcontext=system_u:object_r:unreserved_port_t:s0 tclass=udp_socket permissive=1 
----
Comment 7 Zdenek Pytela 2022-10-12 09:06:35 UTC 
Commit to backport:
commit 1481091ea81cb62ffcfbd6c5eb6b6345d4a70cc0 (HEAD -> rawhide, upstream/rawhide)
Author: Nikola Knazekova <nknazeko>
Date:   Tue Oct 11 14:26:13 2022 +0200

    Label ports 10161-10162 tcp/udp with snmp
Comment 17 errata-xmlrpc 2023-05-09 08:16:52 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (selinux-policy bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2023:2483
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