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Bug 2043599 - postfix cannot use certs stored in dovecot certs directory
Summary: postfix cannot use certs stored in dovecot certs directory
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: selinux-policy
Version: 8.5
Hardware: All
OS: Linux
medium
medium
Target Milestone: rc
: 8.6
Assignee: Zdenek Pytela
QA Contact: Milos Malik
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-01-21 15:32 UTC by Renaud Métrich
Modified: 2022-05-10 16:25 UTC (History)
4 users (show)

Fixed In Version: selinux-policy-3.14.3-92.el8
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2022-05-10 15:15:49 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker RHELPLAN-109131 0 None None None 2022-01-21 15:35:23 UTC
Red Hat Product Errata RHBA-2022:1995 0 None None None 2022-05-10 15:16:09 UTC

Description Renaud Métrich 2022-01-21 15:32:02 UTC 
Description of problem:

When configuring smtpd to use certs stored in dovecot's certs directory, the following AVCs are seen:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
type=PROCTITLE msg=audit(01/19/2022 17:27:01.181:7173515) : proctitle=smtpd -n smtps -t inet -u -o stress= -o syslog_name=postfix/smtps -o smtpd_tls_wrappermode=yes -o smtpd_sasl_auth_enable=yes -o
type=SYSCALL msg=audit(01/19/2022 17:27:01.181:7173515) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=0xffffff9c a1=0x56000dcbef00 a2=O_RDONLY a3=0x0 items=0 ppid=1870242 pid=1914640 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=smtpd exe=/usr/libexec/postfix/smtpd subj=system_u:system_r:postfix_smtpd_t:s0 key=(null)
type=AVC msg=audit(01/19/2022 17:27:01.181:7173515) : avc:  denied  { search } for  pid=1914640 comm=smtpd name=dovecot dev="dm-0" ino=67970523 scontext=system_u:system_r:postfix_smtpd_t:s0 tcontext=system_u:object_r:dovecot_cert_t:s0 tclass=dir permissive=0
...
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

audit2allow shows:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
#============= postfix_smtpd_t ==============
allow postfix_smtpd_t dovecot_cert_t:dir search;
allow postfix_smtpd_t dovecot_cert_t:file getattr;
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

This happens because postfix policy only have this:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
miscfiles_read_generic_certs(postfix_domain)
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

which ends up reading cert_t stuff only.

I think it's harmless to allow postfix from reading all kind of certs, something like this:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
miscfiles_read_all_certs(postfix_domain)
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------


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

selinux-policy-3.14.3-80.el8_5.2.noarch

How reproducible:

Always


Steps to Reproduce:
1. Configure postfix for TLS usage and store certs in dovecot dir

  /etc/postfix/main.cf:
  -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
  smtpd_tls_cert_file = /etc/pki/dovecot/certs/some.cert
  smtpd_tls_key_file = /etc/pki/dovecot/certs/some.key
  -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Actual results:

AVCs above.

Expected results:

No AVC


Additional info:

If allowing all certs is too much from security perspective, then an attribute for "mailer certs" should be created instead.
For now dovecot_cert_t registered through "miscfiles_cert_type(dovecot_cert_t)"
Comment 1 Zdenek Pytela 2022-01-21 17:02:31 UTC 
We currently have these types or certificates:

# seinfo -xa cert_type

Type Attributes: 1
   attribute cert_type;
        cert_t
        dovecot_cert_t
        fwupd_cert_t
        home_cert_t (not in rhel8)
        ipa_cert_t (in ipa-selinux)
        pki_tomcat_cert_t
        slapd_cert_t
Comment 2 Patrik Koncity 2022-02-02 19:13:09 UTC 
Hi Renaud, 

please can you reproduce the scenario again and attach here full AVC's messages in permissive mode?

Steps to enable full auditing and permissive SELinux mode:

1) Open the /etc/audit/rules.d/audit.rules file in an editor.
2) Remove the following line if it exists:
-a task,never
3) Add the following line to the end of the file:
-w /etc/shadow -p w
4) Restart the audit daemon:
  # service auditd restart
5) Open the /etc/selinux/config file in an editor.
change line
SELINUX=enforcing
to
SELINUX=permissive
6) Re-run your scenario 
7) Collect AVC denials:
# ausearch -i -m avc,user_avc,selinux_err,user_selinux_err -ts today

Thank you,
Patrik
Comment 4 Zdenek Pytela 2022-02-11 16:52:51 UTC 
I've submitted a Fedora PR to address the issue:
https://github.com/fedora-selinux/selinux-policy/pull/1068

Allowing access to dovecot_cert_t only, given the output in #c1 I don't think there is a reason to read other certificates.
Comment 5 Zdenek Pytela 2022-02-14 15:36:34 UTC 
To backport:
commit 03e93e0ddd2b3c41138bd3cbc20ea7bd61f58502 (HEAD -> rawhide, upstream/rawhide)
Author: Zdenek Pytela <zpytela>
Date:   Fri Feb 11 17:48:59 2022 +0100

    Allow postfix_domain read dovecot certificates
Comment 14 errata-xmlrpc 2022-05-10 15:15:49 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-2022:1995
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