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snap.core.hook.configure.src
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# snap-seccomp version information: # 2f005e87ff7609f68f65819191a6958c287e2983 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