# snap-seccomp version information:
# ec5d332734e9444e45df5495ed3822e79ee24a6d 2.5.3 e96c43fe76b249e99e02e7ee97d074f17ed464207a45d0472d26d15138a88d7d bpf-actlog

# Description: Allows access to app-specific directories and basic runtime
#
# The default seccomp policy is default deny with an allowlist of allowed
# syscalls. The default policy is intended to be safe for any application to
# use and should be evaluated in conjunction with other security backends (eg
# AppArmor). For example, a few particularly problematic syscalls that are left
# out of the default policy are (non-exhaustive):
# - kexec_load
# - create_module, init_module, finit_module, delete_module (kernel modules)
# - name_to_handle_at (history of vulnerabilities)
# - open_by_handle_at (history of vulnerabilities)
# - ptrace (can be used to break out of sandbox with <4.8 kernels)
# - add_key, keyctl, request_key (kernel keyring)

#
# Allowed accesses
#

access
faccessat
faccessat2

alarm
brk

# ARM private syscalls
breakpoint
cacheflush
get_tls
set_tls
usr26
usr32

# Requires input fd and so should not pose more security 
# issues than access to the file in the first place
# Flags are currently unused and should be 0
cachestat - - - 0

# Flags are currently unused and should be 0
mseal - - 0
map_shadow_stack

capget
# AppArmor mediates capabilities, so allow capset (useful for apps that for
# example want to drop capabilities)
capset

chdir
fchdir

# We can't effectively block file perms due to open() with O_CREAT, so allow
# chmod until we have syscall arg filtering (LP: #1446748)
chmod
fchmod
fchmodat
fchmodat2

# Daemons typically run as 'root' so allow chown to 'root'. DAC will prevent
# non-root from chowning to root.
# (chown root:root)
chown - u:root g:root
chown32 - u:root g:root
fchown - u:root g:root
fchown32 - u:root g:root
fchownat - - u:root g:root
lchown - u:root g:root
lchown32 - u:root g:root
# (chown root)
chown - u:root -1
chown32 - u:root -1
fchown - u:root -1
fchown32 - u:root -1
fchownat - - u:root -1
lchown - u:root -1
lchown32 - u:root -1
# (chgrp root)
chown - -1 g:root
chown32 - -1 g:root
fchown - -1 g:root
fchown32 - -1 g:root
fchownat - - -1 g:root
lchown - -1 g:root
lchown32 - -1 g:root

clock_getres
clock_getres_time64
clock_gettime
clock_gettime64
clock_nanosleep
clock_nanosleep_time64
clone
clone3
close
close_range

# needed by ls -l
connect

# the file descriptors used here will already be mediated by apparmor,
# the 6th argument is flags, which currently is always 0
copy_file_range - - - - - 0

chroot

creat
dup
dup2
dup3
epoll_create
epoll_create1
epoll_ctl
epoll_ctl_old
epoll_pwait
epoll_pwait2
epoll_wait
epoll_wait_old
eventfd
eventfd2
execve
execveat
_exit
exit
exit_group
fallocate

# requires CAP_SYS_ADMIN
#fanotify_init
#fanotify_mark

fcntl
fcntl64
flock
fork
ftime
futex
futex_requeue
futex_time64
futex_wait
futex_waitv
futex_wake
get_mempolicy
get_robust_list
get_thread_area
getcpu
getcwd
getdents
getdents64
getegid
getegid32
geteuid
geteuid32
getgid
getgid32
getgroups
getgroups32
getitimer
getpgid
getpgrp
getpid
getppid
# Note that pidfd_open semantics differs from the traditional pid handling.
# Any process can open the pid of any other process in its pid namespace. What
# is further controlled depends on the relationship between the two processes
# and the capabilities of the calling process. Because of this, we allow
# pidfd_open unconditionally here and rely on the kernel to enforce proper
# access control.
pidfd_open
getpriority
getrandom
getresgid
getresgid32
getresuid
getresuid32

getrlimit
ugetrlimit

getrusage
getsid
gettid
gettimeofday
getuid
getuid32

getxattr
fgetxattr
lgetxattr
getxattrat

inotify_add_watch
inotify_init
inotify_init1
inotify_rm_watch

# ioctl() mediation currently primarily relies on Linux capabilities as well as
# the initial syscall for the fd to pass to ioctl(). See 'man capabilities'
# and 'man ioctl_list'. TIOCSTI requires CAP_SYS_ADMIN but allows for faking
# input (man tty_ioctl), so we disallow it to prevent snaps plugging interfaces
# with 'capability sys_admin' from interfering with other snaps or the
# unconfined user's terminal.
# similarly, TIOCLINUX allows to fake input as well (man ioctl_console) so
# disallow that too
# TODO: this should be scaled back even more
~ioctl - TIOCSTI
~ioctl - TIOCLINUX
# see CVE-2019-7303
~ioctl - 4294967295|TIOCSTI
~ioctl - 4294967295|TIOCLINUX
ioctl

io_cancel
io_destroy
io_getevents
io_pgetevents
io_pgetevents_time64
io_setup
io_submit
ioprio_get
# affects other processes, requires CAP_SYS_ADMIN. Potentially allow with
# syscall filtering of (at least) IOPRIO_WHO_USER (LP: #1446748)
#ioprio_set

ipc
kill
# kcmp is guarded in the kernel via ptrace with PTRACE_MODE_READ_REALCREDS
# such that the calling process must already be able to ptrace the target
# processes and so this is safe.
kcmp - - KCMP_FILE
link
linkat

listxattr
llistxattr
flistxattr
listxattrat

lseek
llseek
_llseek
lstat
lstat64

madvise
fadvise64
fadvise64_64
arm_fadvise64_64

mbind
membarrier
memfd_create
memfd_secret
mincore
mkdir
mkdirat
mlock
mlock2
mlockall
mmap
mmap2

# Allow mknod for regular files, pipes and sockets (and not block or char
# devices)
mknod - |S_IFREG -
mknodat - - |S_IFREG -
mknod - |S_IFIFO -
mknodat - - |S_IFIFO -
mknod - |S_IFSOCK -
mknodat - - |S_IFSOCK -

modify_ldt
mprotect

mremap
msgctl
msgget
msgrcv
msgsnd
msync
munlock
munlockall
munmap

nanosleep

# Argument filtering with gt/ge/lt/le does not work properly with
# libseccomp < 2.4 or golang-seccomp < 0.9.1. See:
# - https://bugs.launchpad.net/snapd/+bug/1825052/comments/9
# - https://github.com/seccomp/libseccomp/issues/69
# Eventually we want to use >=0, but we need libseccomp and golang-seccomp to
# be updated everywhere first. In the meantime, use <=19 and rely on the fact
# that AppArmor mediates CAP_SYS_NICE (and for systems without AppArmor, we
# ignore this lack of mediation since snaps are not meaningfully confined).
#
# Allow using nice() with default or lower priority
nice <=19
# Allow using setpriority to set the priority of the calling process to default
# or lower priority (eg, 'nice -n 9 <command>')
setpriority PRIO_PROCESS 0 <=19

# LP: #1446748 - support syscall arg filtering for mode_t with O_CREAT
open

openat
pause
personality
pipe
~pipe2 - |O_NOTIFICATION_PIPE
pipe2
poll
ppoll
ppoll_time64

# LP: #1446748 - support syscall arg filtering
prctl
arch_prctl

read
pread
pread64
preadv
readv

readahead
readdir
readlink
readlinkat

# allow reading from sockets
recv
recvfrom
recvmsg
recvmmsg
recvmmsg_time64

remap_file_pages

removexattr
fremovexattr
lremovexattr
removexattrat

rename
renameat
renameat2

# The man page says this shouldn't be needed, but we've seen denials for it
# in the wild
restart_syscall

rmdir

# glibc 2.35 unconditionally calls rseq for all threads
rseq

rt_sigaction
rt_sigpending
rt_sigprocmask
rt_sigqueueinfo
rt_sigreturn
rt_sigsuspend
rt_sigtimedwait
rt_sigtimedwait_time64
rt_tgsigqueueinfo
sched_getaffinity
sched_getattr
sched_getparam
sched_get_priority_max
sched_get_priority_min
sched_getscheduler
sched_rr_get_interval
sched_rr_get_interval_time64
# enforce pid_t is 0 so the app may only change its own scheduler and affinity.
# Use process-control interface for controlling other pids.
sched_setaffinity 0 - -
sched_setparam 0 -

# 'sched_setscheduler' without argument filtering was allowed in 2.21 and
# earlier and 2.22 added 'sched_setscheduler 0 - -', introducing LP: #1661265.
# For now, continue to allow sched_setscheduler unconditionally.
sched_setscheduler

sched_yield

# Allow configuring seccomp filter. This is ok because the kernel enforces that
# the new filter is a subset of the current filter (ie, no widening
# permissions)
seccomp

# Allow restricting access with Landlock. This is OK because the kernel
# enforces that each new restriction only drops accesses for the calling
# process (i.e., no widening permissions).
landlock_create_ruleset
landlock_add_rule
landlock_restrict_self

select
_newselect
pselect
pselect6
pselect6_time64

# Allow use of SysV semaphores. Note that allocated resources are not freed by
# OOM which can lead to global kernel resource leakage.
semctl
semget
semop
semtimedop
semtimedop_time64

# allow sending to sockets
send
sendto
sendmsg
sendmmsg

sendfile
sendfile64

# These break isolation but are common and can't be mediated at the seccomp
# level with arg filtering
setpgid
setpgrp

set_thread_area
setitimer

# apps don't have CAP_SYS_RESOURCE so these can't be abused to raise the hard
# limits
setrlimit
prlimit64

set_mempolicy
set_robust_list
setsid
set_tid_address

setxattr
fsetxattr
lsetxattr
setxattrat

shmat
shmctl
shmdt
shmget
shutdown
signal
sigaction
signalfd
signalfd4
sigaltstack
sigpending
sigprocmask
sigreturn
sigsuspend
sigtimedwait
sigwaitinfo

# AppArmor mediates AF_UNIX/AF_LOCAL via 'unix' rules and all other AF_*
# domains via 'network' rules. We won't allow bare 'network' AppArmor rules, so
# we can allow 'socket' for all domains except AF_NETLINK and let AppArmor
# handle the rest.
socket AF_UNIX
socket AF_LOCAL
socket AF_INET
socket AF_INET6
socket AF_IPX
socket AF_XDP
socket AF_X25
socket AF_AX25
socket AF_ATMPVC
socket AF_APPLETALK
socket AF_PACKET
socket AF_ALG
socket AF_CAN
socket AF_BRIDGE
socket AF_NETROM
socket AF_ROSE
socket AF_NETBEUI
socket AF_SECURITY
socket AF_KEY
socket AF_ASH
socket AF_ECONET
socket AF_SNA
socket AF_IRDA
socket AF_PPPOX
socket AF_WANPIPE
socket AF_BLUETOOTH
socket AF_RDS
socket AF_LLC
socket AF_TIPC
socket AF_IUCV
socket AF_RXRPC
socket AF_ISDN
socket AF_PHONET
socket AF_IEEE802154
socket AF_CAIF
socket AF_NFC
socket AF_VSOCK
socket AF_MPLS
socket AF_IB
socket AF_QIPCRTR

# For usrsctp, AppArmor doesn't support 'network conn,' since AF_CONN is
# userspace and encapsulated in other domains that are mediated. As such, do
# not allow AF_CONN by default here.
# socket AF_CONN

# For AF_NETLINK, we'll use a combination of AppArmor coarse mediation and
# seccomp arg filtering of netlink families.
# socket AF_NETLINK - -

# needed by snapctl
getsockopt
setsockopt
getsockname
getpeername

# Per man page, on Linux this is limited to only AF_UNIX so it is ok to have
# in the default template
socketpair

splice

stat
stat64
fstat
fstat64
fstatat64
lstat
newfstatat
oldfstat
oldlstat
oldstat
statx

statfs
statfs64
fstatfs
fstatfs64
statvfs
fstatvfs
ustat

symlink
symlinkat

sync
sync_file_range
sync_file_range2
arm_sync_file_range
fdatasync
fsync
syncfs
sysinfo
syslog
tee
tgkill
time
timer_create
timer_delete
timer_getoverrun
timer_gettime
timer_gettime64
timer_settime
timer_settime64
timerfd
timerfd_create
timerfd_gettime
timerfd_gettime64
timerfd_settime
timerfd_settime64
times
tkill

truncate
truncate64
ftruncate
ftruncate64

umask

uname
olduname
oldolduname

unlink
unlinkat

utime
utimensat
utimensat_time64
utimes
futimesat

vfork
vmsplice
wait4
oldwait4
waitpid
waitid

write
writev
pwrite
pwrite64
pwritev
pwritev2

# Allow these and rely on AppArmor to mediate CAP_SETUID and CAP_SETGID. When
# dropping to particular UID/GIDs, we'll use a different set of
# argument-filtered syscalls.
setgid
setgid32
setregid
setregid32
setresgid
setresgid32
setresuid
setresuid32
setreuid
setreuid32
setuid
setuid32
