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# snap-seccomp version information: # 6d2d80316934aab51f6ee08e50fc064be78c32c3 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 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 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 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 # Description: Can access all syscalls of the system so LXD may manage what to # give to its containers, giving device ownership to connected snaps. @unrestricted # Description: Can query system status information. This is restricted because # it gives privileged read access to all processes on the system and should # only be used with trusted apps. # ptrace can be used to break out of the seccomp sandbox, but ps requests # 'ptrace (trace)' from apparmor. 'ps' does not need the ptrace syscall though, # so we deny the ptrace here to make sure we are always safe. Note: may # uncomment once snap-confine understands @deny rules and if/when we # conditionally deny this in the future. #@deny ptrace # 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

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