PLEDGE(2) | System Calls Manual | PLEDGE(2) |
pledge
— restrict
system operations
#include
<unistd.h>
int
pledge
(const
char *promises, const
char *execpromises);
The
pledge
()
system call forces the current process into a restricted-service operating
mode. A few subsets are available, roughly described as computation, memory
management, read-write operations on file descriptors, opening of files, and
networking. In general, these modes were selected by studying the operation
of many programs using libc and other such interfaces, and setting
promises or execpromises.
Use of
pledge
()
in an application will require at least some study and understanding of the
interfaces called. Subsequent calls to pledge
() can
reduce the abilities further, but abilities can never be regained.
A process which attempts a restricted operation is killed with an
uncatchable SIGABRT
, delivering a core file if
possible. A process currently running with pledge has state
‘p’ in ps(1)
output; a process that was terminated due to a pledge violation is accounted
by lastcomm(1) with the
‘P’ flag.
A promises value of "" restricts the process to the _exit(2) system call. This can be used for pure computation operating on memory shared with another process.
Passing NULL
to
promises or execpromises
specifies to not change the current value.
Some system calls, when allowed, have restrictions applied to them:
FIONREAD
,
FIONBIO
, FIOCLEX
, and
FIONCLEX
operations are allowed by default.
Various ioctl requests are allowed against specific file descriptors based
upon the requests audio, bpf,
disklabel, drm,
inet, pf,
route, wroute,
tape, tty,
video, and vmm.PROT_EXEC
isn't allowed.pledge
():The promises argument is specified as a string, with space separated keywords:
NULL
. As a
result, all the expected functionalities of libc stdio work.
clock_getres(2), clock_gettime(2), close(2), closefrom(2), dup(2), dup2(2), dup3(2), fchdir(2), fcntl(2), fstat(2), fsync(2), ftruncate(2), getdents(2), getdtablecount(2), getegid(2), getentropy(2), geteuid(2), getgid(2), getgroups(2), getitimer(2), getlogin(2), getpgid(2), getpgrp(2), getpid(2), getppid(2), getresgid(2), getresuid(2), getrlimit(2), getrtable(2), getsid(2), getthrid(2), gettimeofday(2), getuid(2), issetugid(2), kevent(2), kqueue(2), lseek(2), madvise(2), minherit(2), mmap(2), mprotect(2), mquery(2), munmap(2), nanosleep(2), pipe(2), pipe2(2), poll(2), pread(2), preadv(2), pwrite(2), pwritev(2), read(2), readv(2), recvfrom(2), recvmsg(2), select(2), sendmsg(2), sendsyslog(2), sendto(2), setitimer(2), shutdown(2), sigaction(2), sigprocmask(2), sigreturn(2), socketpair(2), umask(2), wait4(2), write(2), writev(2)
chdir(2), getcwd(3), openat(2), fstatat(2), faccessat(2), readlinkat(2), lstat(2), chmod(2), fchmod(2), fchmodat(2), chflags(2), chflagsat(2), chown(2), fchown(2), fchownat(2), fstat(2), getfsstat(2)
getcwd(3), openat(2), fstatat(2), faccessat(2), readlinkat(2), lstat(2), chmod(2), fchmod(2), fchmodat(2), chflags(2), chflagsat(2), chown(2), fchown(2), fchownat(2), fstat(2)
rename(2), renameat(2), link(2), linkat(2), symlink(2), symlinkat(2), unlink(2), unlinkat(2), mkdir(2), mkdirat(2), rmdir(2)
lstat(2), chmod(2), chflags(2), chown(2), unlink(2), fstat(2)
AF_INET
and AF_INET6
domains (though
setsockopt(2) has been
substantially reduced in functionality):
socket(2), listen(2), bind(2), connect(2), accept4(2), accept(2), getpeername(2), getsockname(2), setsockopt(2), getsockopt(2)
utimes(2), futimes(2), utimensat(2), futimens(2), chmod(2), fchmod(2), fchmodat(2), chflags(2), chflagsat(2), chown(2), fchownat(2), lchown(2), fchown(2), utimes(2)
AF_UNIX
domain:
socket(2), listen(2), bind(2), connect(2), accept4(2), accept(2), getpeername(2), getsockname(2), setsockopt(2), getsockopt(2)
MTIOCGET
and
MTIOCTOP
operations against tape drives.TIOCSPGRP
,
TIOCGETA
, TIOCGPGRP
,
TIOCGWINSZ
, TIOCSWINSZ
,
TIOCSBRK
, TIOCCDTR
,
TIOCSETA
, TIOCSETAW
,
TIOCSETAF
, TIOCUCNTL
fork(2), vfork(2), kill(2), getpriority(2), setpriority(2), setrlimit(2), setpgid(2), setsid(2)
EACCES
. Otherwise the new program starts running
without pledge active, and hopefully makes a new pledge soon.PROT_EXEC
with
mmap(2) and
mprotect(2).setuid(2), seteuid(2), setreuid(2), setresuid(2), setgid(2), setegid(2), setregid(2), setresgid(2), setgroups(2), setlogin(2), setrlimit(2), getpriority(2), setpriority(2)
DIOCADDRULE
,
DIOCGETSTATUS
,
DIOCNATLOOK
,
DIOCRADDTABLES
,
DIOCRCLRADDRS
,
DIOCRCLRTABLES
,
DIOCRCLRTSTATS
,
DIOCRGETTSTATS
,
DIOCRSETADDRS
,
DIOCXBEGIN
,
DIOCXCOMMIT
AUDIO_GETPOS
,
AUDIO_GETPAR
,
AUDIO_SETPAR
,
AUDIO_START
, AUDIO_STOP
,
AUDIO_MIXER_DEVINFO
,
AUDIO_MIXER_READ
,
AUDIO_MIXER_WRITE
VIDIOC_DQBUF
,
VIDIOC_ENUM_FMT
,
VIDIOC_ENUM_FRAMEINTERVALS
,
VIDIOC_ENUM_FRAMESIZES
,
VIDIOC_G_CTRL
,
VIDIOC_G_PARM
,
VIDIOC_QBUF
,
VIDIOC_QUERYBUF
,
VIDIOC_QUERYCAP
,
VIDIOC_QUERYCTRL
,
VIDIOC_S_CTRL
,
VIDIOC_S_FMT
,
VIDIOC_S_PARM
,
VIDIOC_STREAMOFF
,
VIDIOC_STREAMON
,
VIDIOC_TRY_FMT
,
VIDIOC_REQBUFS
BIOCGSTATS
operation for statistics
collection from a bpf(4)
device.ENOSYS
.
Also when
pledge
()
is called with higher promises or
execpromises, those changes will be ignored and
return success. This is useful when a parent enforces
execpromises but an execve'd child has a different
idea.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
pledge
() will fail if:
The pledge
() system call first appeared in
OpenBSD 5.9.
July 17, 2020 | OpenBSD-6.8 |