|PLEDGE(2)||System Calls Manual||PLEDGE(2)|
char *promises, const
pledgesystem 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.
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
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’
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.
promises or execpromises
specifies to not change the current value.
Some system calls, when allowed, have restrictions applied to them:
FIONCLEXoperations are allowed by default. Various ioctl requests are allowed against specific file descriptors based upon the requests audio, bpf, disklabel, drm, inet, pf, route, tape, tty, video, and vmm.
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)
AF_INET6domains (though setsockopt(2) has been substantially reduced in functionality):
MTIOCTOPoperations against tape drives.
EACCESS. Otherwise the new program starts running without pledge active, and hopefully makes a new pledge soon.
PROT_EXECwith mmap(2) and mprotect(2).
BIOCGSTATSoperation for statistics collection from a bpf(4) device.
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.
pledgewill fail if:
pledgesystem call first appeared in OpenBSD 5.9.
|January 21, 2019||OpenBSD-current|