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Description of problem:
There are multiple issues happening when a confined user to "staff_u" tries to edit the cron of another user through some sudo rule.
1. "sudo -u USER crontab -l" fails
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
$ id -Z
staff_u:staff_r:staff_t:s0-s0:c0.c1023
$ sudo -u <USER> crontab -l
'/var/spool/cron' is not a directory, bailing out.
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
This happens because /var/spool/cron is not readable by staff_sudo_t, the context used when executing "crontab -l" because of the absence of transition to "crontab_t" due to using "sudo crontab" command.
Strace shows:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
4434 [staff_u:staff_r:staff_sudo_t:s0-s0:c0.c1023] 10:30:21.103895 execve("/bin/crontab" [system_u:object_r:crontab_exec_t:s0], ["crontab", "-l"] ...
[...]
4434 [staff_u:staff_r:staff_sudo_t:s0-s0:c0.c1023] 10:30:21.134230 stat("/var/spool/cron" [system_u:object_r:user_cron_spool_t:s0], 0x7ffc16aac270) = -1 EACCES (Permission denied)
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
This is a bug, IMHO there should be the transition to crontab_t when executing the command, it should not execute as "staff_sudo_t" at all.
2. "sudo -u USER -i crontab -l" fails silently and produces AVCs
This happens when `Defaults use_pty` is used in the sudo configuration.
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
$ id -Z
staff_u:staff_r:staff_t:s0-s0:c0.c1023
$ sudo -u <USER> -i crontab -l
$
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
AVC:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
type=PROCTITLE msg=audit(07/17/2023 10:38:01.277:528) : proctitle=crontab -l
type=EXECVE msg=audit(07/17/2023 10:38:01.277:528) : argc=2 a0=crontab a1=-l
type=SYSCALL msg=audit(07/17/2023 10:38:01.277:528) : arch=x86_64 syscall=execve success=yes exit=0 a0=0x561829ebdd40 a1=0x561829ea0cd0 a2=0x561829ebf400 a3=0x8 items=0 ppid=4553 pid=4554 auid=staff uid=USER gid=USER euid=root suid=root fsuid=root egid=USER sgid=USER fsgid=USER tty=(none) ses=13 comm=crontab exe=/usr/bin/crontab subj=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0
type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0
type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0
type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
Due to using "sudo -i", the transition to "crontab_t" happens when executing the command.
Unfortunately "crontab_t" cannot read/write on the pseudo tty allocated by sudo.
3. "sudo -u <USER> -i" then "crontab -e" fails silently after some timeout and produces AVCs
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
$ id -Z
staff_u:staff_r:staff_t:s0-s0:c0.c1023
$ sudo -u USER -i
$ crontab -e
<long delay then exits silently>
$
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
AVC:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
type=PROCTITLE msg=audit(07/17/2023 10:42:32.287:551) : proctitle=vim /tmp/crontab.wTBQAP
type=SYSCALL msg=audit(07/17/2023 10:42:32.287:551) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=AT_FDCWD a1=0x55a601568060 a2=O_WRONLY|O_CREAT|O_EXCL|O_NOFOLLOW a3=0x180 items=0 ppid=4805 pid=4807 auid=staff uid=USER gid=USER euid=USER suid=USER fsuid=USER egid=USER sgid=USER fsgid=USER tty=(none) ses=13 comm=vim exe=/usr/bin/vim subj=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(07/17/2023 10:42:32.287:551) : avc: denied { write } for pid=4807 comm=vim name=USER dev="dm-0" ino=16967532 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_dir_t:s0 tclass=dir permissive=0
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
This happens when vim, executing as "crontab_t" and used as default editor for "crontab -e" tries to write its /home/USER/.viminfo file.
Due to not being able to read the user's home directory. This is NOT related to "use_pty".
Version-Release number of selected component (if applicable):
selinux-policy-3.14.3-117.el8_8.2.noarch
How reproducible:
Always
Steps to Reproduce:
1. Add "Defaults use_pty" to /etc/sudoers
2. Let a user mapped to "staff_u" sudo to the target user "USER"
# cat /etc/sudoers.d/staff
staff ALL = (USER) NOPASSWD: ALL
3. Execute various scenarios above
Actual results:
Failures
Expected results:
No failures
Comment 2RHEL Program Management
2023-09-01 22:40:04 UTC
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.
Comment 3RHEL Program Management
2023-09-01 22:45:04 UTC
This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there.
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Description of problem: There are multiple issues happening when a confined user to "staff_u" tries to edit the cron of another user through some sudo rule. 1. "sudo -u USER crontab -l" fails -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- $ id -Z staff_u:staff_r:staff_t:s0-s0:c0.c1023 $ sudo -u <USER> crontab -l '/var/spool/cron' is not a directory, bailing out. -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- This happens because /var/spool/cron is not readable by staff_sudo_t, the context used when executing "crontab -l" because of the absence of transition to "crontab_t" due to using "sudo crontab" command. Strace shows: -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- 4434 [staff_u:staff_r:staff_sudo_t:s0-s0:c0.c1023] 10:30:21.103895 execve("/bin/crontab" [system_u:object_r:crontab_exec_t:s0], ["crontab", "-l"] ... [...] 4434 [staff_u:staff_r:staff_sudo_t:s0-s0:c0.c1023] 10:30:21.134230 stat("/var/spool/cron" [system_u:object_r:user_cron_spool_t:s0], 0x7ffc16aac270) = -1 EACCES (Permission denied) -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- This is a bug, IMHO there should be the transition to crontab_t when executing the command, it should not execute as "staff_sudo_t" at all. 2. "sudo -u USER -i crontab -l" fails silently and produces AVCs This happens when `Defaults use_pty` is used in the sudo configuration. -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- $ id -Z staff_u:staff_r:staff_t:s0-s0:c0.c1023 $ sudo -u <USER> -i crontab -l $ -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- AVC: -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- type=PROCTITLE msg=audit(07/17/2023 10:38:01.277:528) : proctitle=crontab -l type=EXECVE msg=audit(07/17/2023 10:38:01.277:528) : argc=2 a0=crontab a1=-l type=SYSCALL msg=audit(07/17/2023 10:38:01.277:528) : arch=x86_64 syscall=execve success=yes exit=0 a0=0x561829ebdd40 a1=0x561829ea0cd0 a2=0x561829ebf400 a3=0x8 items=0 ppid=4553 pid=4554 auid=staff uid=USER gid=USER euid=root suid=root fsuid=root egid=USER sgid=USER fsgid=USER tty=(none) ses=13 comm=crontab exe=/usr/bin/crontab subj=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 key=(null) type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0 type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0 type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0 type=AVC msg=audit(07/17/2023 10:38:01.277:528) : avc: denied { read write } for pid=4554 comm=crontab path=/dev/pts/3 dev="devpts" ino=6 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=staff_u:object_r:devpts_t:s0 tclass=chr_file permissive=0 -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- Due to using "sudo -i", the transition to "crontab_t" happens when executing the command. Unfortunately "crontab_t" cannot read/write on the pseudo tty allocated by sudo. 3. "sudo -u <USER> -i" then "crontab -e" fails silently after some timeout and produces AVCs -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- $ id -Z staff_u:staff_r:staff_t:s0-s0:c0.c1023 $ sudo -u USER -i $ crontab -e <long delay then exits silently> $ -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- AVC: -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- type=PROCTITLE msg=audit(07/17/2023 10:42:32.287:551) : proctitle=vim /tmp/crontab.wTBQAP type=SYSCALL msg=audit(07/17/2023 10:42:32.287:551) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=AT_FDCWD a1=0x55a601568060 a2=O_WRONLY|O_CREAT|O_EXCL|O_NOFOLLOW a3=0x180 items=0 ppid=4805 pid=4807 auid=staff uid=USER gid=USER euid=USER suid=USER fsuid=USER egid=USER sgid=USER fsgid=USER tty=(none) ses=13 comm=vim exe=/usr/bin/vim subj=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 key=(null) type=AVC msg=audit(07/17/2023 10:42:32.287:551) : avc: denied { write } for pid=4807 comm=vim name=USER dev="dm-0" ino=16967532 scontext=staff_u:staff_r:crontab_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_dir_t:s0 tclass=dir permissive=0 -------- 8< ---------------- 8< ---------------- 8< ---------------- 8< -------- This happens when vim, executing as "crontab_t" and used as default editor for "crontab -e" tries to write its /home/USER/.viminfo file. Due to not being able to read the user's home directory. This is NOT related to "use_pty". Version-Release number of selected component (if applicable): selinux-policy-3.14.3-117.el8_8.2.noarch How reproducible: Always Steps to Reproduce: 1. Add "Defaults use_pty" to /etc/sudoers 2. Let a user mapped to "staff_u" sudo to the target user "USER" # cat /etc/sudoers.d/staff staff ALL = (USER) NOPASSWD: ALL 3. Execute various scenarios above Actual results: Failures Expected results: No failures