Bug 1781696

This is most likely related to rebase of fprintd - see rhbz#1740752

Can you tell me more about the situation which lead to the SELinux denial? What commands did you run?

(In reply to Milos Malik from comment #2)
> Can you tell me more about the situation which lead to the SELinux denial?
> What commands did you run?

I haven't run any commands, this happens on my laptop right after I login to the GNOME session.

The fprintd is dbus service and actually failed to start because of this selinux denial. 
It starts fine with disabled selinux.

$ sudo ausearch -m AVC -ts recent
----
time->Tue Dec 10 17:28:56 2019
type=PROCTITLE msg=audit(1575995336.675:301): proctitle="(fprintd)"
type=SYSCALL msg=audit(1575995336.675:301): arch=c000003e syscall=90 success=no exit=-13 a0=564a3969ae40 a1=1ed a2=ffffffff a3=0 items=0 ppid=1 pid=15931 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="(fprintd)" exe="/usr/lib/systemd/systemd" subj=system_u:system_r:init_t:s0 key=(null)
type=AVC msg=audit(1575995336.675:301): avc:  denied  { setattr } for  pid=15931 comm="(fprintd)" name="fprint" dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=0
----
time->Tue Dec 10 17:31:49 2019
type=PROCTITLE msg=audit(1575995509.295:303): proctitle="(fprintd)"
type=SYSCALL msg=audit(1575995509.295:303): arch=c000003e syscall=90 success=no exit=-13 a0=564a396b24b0 a1=1ed a2=ffffffff a3=0 items=0 ppid=1 pid=17937 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="(fprintd)" exe="/usr/lib/systemd/systemd" subj=system_u:system_r:init_t:s0 key=(null)
type=AVC msg=audit(1575995509.295:303): avc:  denied  { setattr } for  pid=17937 comm="(fprintd)" name="fprint" dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=0
----
time->Tue Dec 10 17:35:22 2019
type=PROCTITLE msg=audit(1575995722.868:316): proctitle="(fprintd)"
type=SYSCALL msg=audit(1575995722.868:316): arch=c000003e syscall=90 success=no exit=-13 a0=564a396b7ba0 a1=1ed a2=ffffffff a3=0 items=0 ppid=1 pid=20677 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="(fprintd)" exe="/usr/lib/systemd/systemd" subj=system_u:system_r:init_t:s0 key=(null)
type=AVC msg=audit(1575995722.868:316): avc:  denied  { setattr } for  pid=20677 comm="(fprintd)" name="fprint" dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=0
----
time->Tue Dec 10 17:35:39 2019
type=PROCTITLE msg=audit(1575995739.042:332): proctitle="(fprintd)"
type=SYSCALL msg=audit(1575995739.042:332): arch=c000003e syscall=90 success=yes exit=0 a0=564a395d2050 a1=1ed a2=ffffffff a3=0 items=0 ppid=1 pid=20870 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="(fprintd)" exe="/usr/lib/systemd/systemd" subj=system_u:system_r:init_t:s0 key=(null)
type=AVC msg=audit(1575995739.042:332): avc:  denied  { setattr } for  pid=20870 comm="(fprintd)" name="fprint" dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=1
----
time->Tue Dec 10 17:35:39 2019
type=PROCTITLE msg=audit(1575995739.042:333): proctitle="(fprintd)"
type=SYSCALL msg=audit(1575995739.042:333): arch=c000003e syscall=257 success=yes exit=3 a0=ffffff9c a1=564a395d2050 a2=f0000 a3=0 items=0 ppid=1 pid=20870 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="(fprintd)" exe="/usr/lib/systemd/systemd" subj=system_u:system_r:init_t:s0 key=(null)
type=AVC msg=audit(1575995739.042:333): avc:  denied  { read } for  pid=20870 comm="(fprintd)" name="fprint" dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=1

Also it seems to freeze my lock screen as a result of that. The fprintd daemon is responsible for fingerprint reader which I have on my laptop.

Jiri,

Would you be able to help with isolating the issue? For some reason, "chmod 755" is executed and denied, but it is not clear for which file.

# make the system permissive
setenforce 0
# save a timestamp
since=$(date +%T)
# enable full path auditing
auditctl -w /etc/shadow -p w

<reproduce the issue>

# list audit records
ausearch -i -m avc,user_avc,selinux_err,user_selinux_err -ts "$since"  > /tmp/audit.out

# unset the changes
setenforce 1
auditctl -W /etc/shadow -p w
unset since

Could you please also verify what is this file SELinux type?

ls -lZ /usr/libexec/fprintd
matchpathcon /usr/libexec/fprintd

Created attachment 1644021 [details]
audi log

# ls -lZ /usr/libexec/fprintd
-rwxr-xr-x. 1 root root system_u:object_r:fprintd_exec_t:s0 63168 Nov 21 16:30 /usr/libexec/fprintd

# matchpathcon /usr/libexec/fprintd
/usr/libexec/fprintd    system_u:object_r:fprintd_exec_t:s0

I also see this on my RHEL-8.2 VM after logging into X session as unconfined user:
----
type=PROCTITLE msg=audit(12/12/2019 09:28:42.212:273) : proctitle=(fprintd) 
type=PATH msg=audit(12/12/2019 09:28:42.212:273) : item=0 name=/var/lib/fprint inode=162775 dev=08:02 mode=dir,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:fprintd_var_lib_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 
type=CWD msg=audit(12/12/2019 09:28:42.212:273) : cwd=/ 
type=SYSCALL msg=audit(12/12/2019 09:28:42.212:273) : arch=x86_64 syscall=chmod success=no exit=EACCES(Permission denied) a0=0x557e7a7dcdd0 a1=0755 a2=0xffffffff a3=0x0 items=1 ppid=1 pid=3887 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=(fprintd) exe=/usr/lib/systemd/systemd subj=system_u:system_r:init_t:s0 key=(null) 
type=AVC msg=audit(12/12/2019 09:28:42.212:273) : avc:  denied  { setattr } for  pid=3887 comm=(fprintd) name=fprint dev="sda2" ino=162775 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=0 
----

# ls -dZ /var/lib/fprint
system_u:object_r:fprintd_var_lib_t:s0 /var/lib/fprint
# ls -ld /var/lib/fprint
drwxr-xr-x. 2 root root 6 Nov 21 16:30 /var/lib/fprint
#

# service fprintd status
Redirecting to /bin/systemctl status fprintd.service
● fprintd.service - Fingerprint Authentication Daemon
   Loaded: loaded (/usr/lib/systemd/system/fprintd.service; static; vendor preset: disabled)
   Active: failed (Result: exit-code) since Thu 2019-12-12 09:28:42 CET; 4min 5s ago
     Docs: man:fprintd(1)
  Process: 3887 ExecStart=/usr/libexec/fprintd (code=exited, status=238/STATE_DIRECTORY)
 Main PID: 3887 (code=exited, status=238/STATE_DIRECTORY)

Dec 12 09:28:42 localhost.localdomain systemd[1]: Starting Fingerprint Authentication Daemon...
Dec 12 09:28:42 localhost.localdomain systemd[1]: fprintd.service: Main process exited, code=exited, status=238/STATE_DIRECTORY
Dec 12 09:28:42 localhost.localdomain systemd[1]: fprintd.service: Failed with result 'exit-code'.
Dec 12 09:28:42 localhost.localdomain systemd[1]: Failed to start Fingerprint Authentication Daemon.
#

# ls -ld /var/lib/fprint
drwxr-xr-x. 2 root root 6 Nov 21 16:30 /var/lib/fprint
# ls -dZ /var/lib/fprint
system_u:object_r:fprintd_var_lib_t:s0 /var/lib/fprint
# service fprintd status
Redirecting to /bin/systemctl status fprintd.service
● fprintd.service - Fingerprint Authentication Daemon
   Loaded: loaded (/usr/lib/systemd/system/fprintd.service; static; vendor preset: disabled)
   Active: failed (Result: exit-code) since Thu 2019-12-12 09:37:11 CET; 12s ago
     Docs: man:fprintd(1)
  Process: 6889 ExecStart=/usr/libexec/fprintd (code=exited, status=238/STATE_DIRECTORY)
 Main PID: 6889 (code=exited, status=238/STATE_DIRECTORY)

Dec 12 09:37:11 localhost.localdomain systemd[1]: Starting Fingerprint Authentication Daemon...
Dec 12 09:37:11 localhost.localdomain systemd[1]: fprintd.service: Main process exited, code=exited, status=238/STATE_DIRECTORY
Dec 12 09:37:11 localhost.localdomain systemd[1]: fprintd.service: Failed with result 'exit-code'.
Dec 12 09:37:11 localhost.localdomain systemd[1]: Failed to start Fingerprint Authentication Daemon.
# setenforce 0
# service fprintd start
Redirecting to /bin/systemctl start fprintd.service
# service fprintd status
Redirecting to /bin/systemctl status fprintd.service
● fprintd.service - Fingerprint Authentication Daemon
   Loaded: loaded (/usr/lib/systemd/system/fprintd.service; static; vendor preset: disabled)
   Active: active (running) since Thu 2019-12-12 09:37:35 CET; 1s ago
     Docs: man:fprintd(1)
 Main PID: 6962 (fprintd)
    Tasks: 3
   Memory: 2.3M
   CGroup: /system.slice/fprintd.service
           └─6962 /usr/libexec/fprintd

Dec 12 09:37:35 localhost.localdomain systemd[1]: Starting Fingerprint Authentication Daemon...
Dec 12 09:37:35 localhost.localdomain systemd[1]: Started Fingerprint Authentication Daemon.

# 

----
type=PROCTITLE msg=audit(12/12/2019 09:37:35.606:585) : proctitle=(fprintd) 
type=PATH msg=audit(12/12/2019 09:37:35.606:585) : item=0 name=/var/lib/fprint inode=162775 dev=08:02 mode=dir,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:fprintd_var_lib_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 
type=CWD msg=audit(12/12/2019 09:37:35.606:585) : cwd=/ 
type=SYSCALL msg=audit(12/12/2019 09:37:35.606:585) : arch=x86_64 syscall=chmod success=yes exit=0 a0=0x557e7a7938a0 a1=0755 a2=0xffffffff a3=0x0 items=1 ppid=1 pid=6962 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=(fprintd) exe=/usr/lib/systemd/systemd subj=system_u:system_r:init_t:s0 key=(null) 
type=AVC msg=audit(12/12/2019 09:37:35.606:585) : avc:  denied  { setattr } for  pid=6962 comm=(fprintd) name=fprint dev="sda2" ino=162775 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=1 
----
type=PROCTITLE msg=audit(12/12/2019 09:37:35.606:586) : proctitle=(fprintd) 
type=PATH msg=audit(12/12/2019 09:37:35.606:586) : item=0 name=/var/lib/fprint inode=162775 dev=08:02 mode=dir,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:fprintd_var_lib_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 
type=CWD msg=audit(12/12/2019 09:37:35.606:586) : cwd=/ 
type=SYSCALL msg=audit(12/12/2019 09:37:35.606:586) : arch=x86_64 syscall=openat success=yes exit=3 a0=0xffffff9c a1=0x557e7a7938a0 a2=O_RDONLY|O_DIRECTORY|O_NOFOLLOW|O_NOATIME|O_CLOEXEC a3=0x0 items=1 ppid=1 pid=6962 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=(fprintd) exe=/usr/lib/systemd/systemd subj=system_u:system_r:init_t:s0 key=(null) 
type=AVC msg=audit(12/12/2019 09:37:35.606:586) : avc:  denied  { read } for  pid=6962 comm=(fprintd) name=fprint dev="sda2" ino=162775 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=1 
----

# ls -ld /var/lib/fprint
drwxr-xr-x. 2 root root 6 Nov 21 16:30 /var/lib/fprint
# ls -dZ /var/lib/fprint
system_u:object_r:fprintd_var_lib_t:s0 /var/lib/fprint
#

Unfortunately, I don't know why syscall=chmod is used. Permissions and ownership of /var/lib/fprint look the same way in enforcing and permissive mode (before and after).

# grep -i state /usr/lib/systemd/system/fprintd.service 
StateDirectory=fprint
#

Maybe some systemd magic is involved.

One thing is sure. The fprintd service does not start in enforcing mode if following rule is missing:

allow init_t fprintd_var_lib_t:dir { read setattr };

*** Bug 1782446 has been marked as a duplicate of this bug. ***

I rather suspect this line:

NoNewPrivileges=true

fprintd runs in init_t domain instead of a transition to its own. If the transition gets done, the permissios are granted:

# sesearch -A -s fprintd_t -t fprintd_var_lib_t -c dir -p read,setattr
allow fprintd_t fprintd_var_lib_t:dir { add_name create getattr ioctl link lock open read remove_name rename reparent rmdir search setattr unlink write };

Michale,

It looks like "chmod 755 /var/lib/fprint"-equivalent syscall and subsequent read was executed when starting fprintd service:

----
type=PROCTITLE msg=audit(12/11/2019 16:58:20.123:843) : proctitle=(fprintd) 
type=PATH msg=audit(12/11/2019 16:58:20.123:843) : item=0 name=/var/lib/fprint inode=126129365 dev=fd:03 mode=dir,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:fprintd_var_lib_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 
type=CWD msg=audit(12/11/2019 16:58:20.123:843) : cwd=/ 
type=SYSCALL msg=audit(12/11/2019 16:58:20.123:843) : arch=x86_64 syscall=chmod success=yes exit=0 a0=0x564a3972ad00 a1=0755 a2=0xffffffff a3=0x0 items=1 ppid=1 pid=6906 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=(fprintd) exe=/usr/lib/systemd/systemd subj=system_u:system_r:init_t:s0 key=(null) 
type=AVC msg=audit(12/11/2019 16:58:20.123:843) : avc:  denied  { setattr } for  pid=6906 comm=(fprintd) name=fprint dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=1 
----
type=PROCTITLE msg=audit(12/11/2019 16:58:20.123:844) : proctitle=(fprintd) 
type=PATH msg=audit(12/11/2019 16:58:20.123:844) : item=0 name=/var/lib/fprint inode=126129365 dev=fd:03 mode=dir,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:fprintd_var_lib_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 
type=CWD msg=audit(12/11/2019 16:58:20.123:844) : cwd=/ 
type=SYSCALL msg=audit(12/11/2019 16:58:20.123:844) : arch=x86_64 syscall=openat success=yes exit=3 a0=0xffffff9c a1=0x564a3972ad00 a2=O_RDONLY|O_DIRECTORY|O_NOFOLLOW|O_NOATIME|O_CLOEXEC a3=0x0 items=1 ppid=1 pid=6906 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=(fprintd) exe=/usr/lib/systemd/systemd subj=system_u:system_r:init_t:s0 key=(null) 
type=AVC msg=audit(12/11/2019 16:58:20.123:844) : avc:  denied  { read } for  pid=6906 comm=(fprintd) name=fprint dev="dm-3" ino=126129365 scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:fprintd_var_lib_t:s0 tclass=dir permissive=1
----

still in the systemd's init_t context. The syscall were denied per current policy settings, but chmod actually does not seem to have any effect since the directory mode is 0755 both before and after. Is this a result of some service settings? Is it systemd which calls the syscalls? It started to happen lately, may be a result of the package rebase in RHEL 8.2.

[Service]
Type=dbus
BusName=net.reactivated.Fprint
ExecStart=/usr/libexec/fprintd

# Filesystem lockdown
ProtectSystem=strict
ProtectKernelTunables=true
ProtectControlGroups=true
# This always corresponds to /var/lib/fprint
StateDirectory=fprint
ProtectHome=true
PrivateTmp=true

# Network
PrivateNetwork=true
RestrictAddressFamilies=AF_UNIX AF_LOCAL AF_NETLINK

# Execute Mappings
MemoryDenyWriteExecute=true

# Modules
ProtectKernelModules=true

# Real-time
RestrictRealtime=true

# Privilege escalation
NoNewPrivileges=true

Issue seen under current CentOS 8 Stream including selinux-policy-3.14.3-20.el8.

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, 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-2020:1773