selinux January 2022

selinux@lists.fedoraproject.org

3 participants
3 discussions

certmonger post-save scripts & certmonger_unconfined_t domain
by Sam Morris 06 Jun '24

06 Jun '24

Certmonger allows for the configuration of a post-save command to be run after it has obtained new certificates. This can be used to copy the key & certificates out of wherever certmonger is allowed to put them, and save them elsewhere with a particular owner/group, combine the certificate & chain into a single file as required by some software, etc. The problem comes with SELinux which prevents my post-save scripts from being able to do all of that. I thought the solution was to give the scripts the context of certmonger_unconfined_exec_t, which would cause a transition to the certmonger_unconfined_t domain which is as its name suggests unconfined; but I can't get this to work. I'm trying to use runcon to simulate certmonger executing a fake script: # cat /tmp/fakescript #!/bin/bash set -eu id -Z # /tmp/fakescript unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 # ls -Z /tmp/fakescript unconfined_u:object_r:certmonger_unconfined_exec_t:s0 /tmp/fakescript # runcon system_u:system_r:certmonger_t:s0 /tmp/fakescript runcon: ‘/tmp/fakescript’: Permission denied Here is the avc denial: ---- type=PROCTITLE msg=audit(27/04/21 16:16:47.156:153492) : proctitle=runcon system_u:system_r:certmonger_t:s0 /tmp/fakescript type=SYSCALL msg=audit(27/04/21 16:16:47.156:153492) : arch=x86_64 syscall=execve success=no exit=EACCES(Permission denied) a0=0x7ffd8aa768ab a1=0x7ffd8aa75888 a2=0x7ffd8aa75898 a3=0x0 items=0 ppid=177795 pid=177796 auid=sam.admin uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=pts5 ses=103 comm=runcon exe=/usr/bin/runcon subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=AVC msg=audit(27/04/21 16:16:47.156:153492) : avc: denied { entrypoint } for pid=177796 comm=runcon path=/tmp/fakescript dev="dm-0" ino=33563064 scontext=system_u:system_r:certmonger_t:s0 tcontext=unconfined_u:object_r:certmonger_unconfined_exec_t:s0 tclass=file permissive=0 Even though: # sepolicy transition -s certmonger_t -t certmonger_unconfined_t certmonger_t @ certmonger_unconfined_exec_t --> certmonger_unconfined_t Diving in a little deeper, I can see that certmonger can execute the file: # sesearch -s certmonger_t -t certmonger_unconfined_exec_t -c file -p execute -A allow certmonger_t certmonger_unconfined_exec_t:file { execute execute_no_trans getattr ioctl map open read }; ... and that the file type is an entrypoint for the certmonger_unconfined_t domain: # sesearch -s certmonger_unconfined_t -t certmonger_unconfined_exec_t -c file -p entrypoint -A allow certmonger_unconfined_t certmonger_unconfined_exec_t:file { entrypoint execute getattr ioctl lock map open read }; ... and that transition is permitted from certmonger_t: # sesearch -s certmonger_t -t certmonger_unconfined_t -c process -p transition -A allow certmonger_t certmonger_unconfined_t:process transition; Which leaves me scratching my head, unsure why it doesn't work in practice... -- Sam Morris <https://robots.org.uk/> PGP: rsa4096/CAAA AA1A CA69 A83A 892B 1855 D20B 4202 5CDA 27B9

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custom selinux
by al so 27 Jan '22

27 Jan '22

On a system where SELinux is enforced, how to selectively disable SELinux on a few custom linux processes without impacting the rest?

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SELinux is preventing mktemp from using the dac_read_search capability.
by Robert Moskowitz 02 Jan '22

02 Jan '22

I keep getting these errors. I got them back with F32 and Xfce, and now with F35 and Xfce. Here is the full detail. What do I do to fix this? =============== SELinux is preventing mktemp from using the dac_read_search capability. ***** Plugin dac_override (91.4 confidence) suggests ********************** If you want to help identify if domain needs this access or you have a file with the wrong permissions on your system Then turn on full auditing to get path information about the offending file and generate the error again. Do Turn on full auditing # auditctl -w /etc/shadow -p w Try to recreate AVC. Then execute # ausearch -m avc -ts recent If you see PATH record check ownership/permissions on file, and fix it, otherwise report as a bugzilla. ***** Plugin catchall (9.59 confidence) suggests ************************** If you believe that mktemp should have the dac_read_search capability by default. Then you should report this as a bug. You can generate a local policy module to allow this access. Do allow this access for now by executing: # ausearch -c 'mktemp' --raw | audit2allow -M my-mktemp # semodule -X 300 -i my-mktemp.pp Additional Information: Source Context system_u:system_r:logwatch_mail_t:s0-s0:c0.c1023 Target Context system_u:system_r:logwatch_mail_t:s0-s0:c0.c1023 Target Objects Unknown [ capability ] Source mktemp Source Path mktemp Port <Unknown> Host lx140e.htt-consult.com Source RPM Packages Target RPM Packages SELinux Policy RPM selinux-policy-targeted-35.7-1.fc35.noarch Local Policy RPM selinux-policy-targeted-35.7-1.fc35.noarch Selinux Enabled True Policy Type targeted Enforcing Mode Enforcing Host Name lx140e.htt-consult.com Platform Linux lx140e.htt-consult.com 5.15.11-200.fc35.x86_64 #1 SMP Wed Dec 22 15:41:11 UTC 2021 x86_64 x86_64 Alert Count 13912 First Seen 2021-11-15 03:27:05 EST Last Seen 2022-01-02 03:09:16 EST Local ID 2ef8a1a9-ddf5-42cc-b5dc-c08354265cc8 Raw Audit Messages type=AVC msg=audit(1641110956.728:1612): avc: denied { dac_read_search } for pid=24078 comm="dotlockfile" capability=2 scontext=system_u:system_r:logwatch_mail_t:s0-s0:c0.c1023 tcontext=system_u:system_r:logwatch_mail_t:s0-s0:c0.c1023 tclass=capability permissive=0 Hash: mktemp,logwatch_mail_t,logwatch_mail_t,capability,dac_read_search

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selinux January 2022