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/* -*- mode: c; c-file-style: "openbsd" -*- */
/*
* Copyright (c) 2008 Vincent Bernat <bernat@luffy.cx>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "lldpd.h"
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include "syscall-names.h"
#include <seccomp.h>
#ifndef SYS_SECCOMP
# define SYS_SECCOMP 1
#endif
#if defined(__i386__)
# define REG_SYSCALL REG_EAX
# define ARCH_NR AUDIT_ARCH_I386
#elif defined(__x86_64__)
# define REG_SYSCALL REG_RAX
# define ARCH_NR AUDIT_ARCH_X86_64
#else
# error "Platform does not support seccomp filter yet"
# define REG_SYSCALL 0
# define ARCH_NR 0
#endif
/* If there is no privilege separation, seccomp is currently useless */
#ifdef ENABLE_PRIVSEP
static int monitored = -1;
static int trapped = 0;
/**
* SIGSYS signal handler
* @param nr the signal number
* @param info siginfo_t pointer
* @param void_context handler context
*
* Simple signal handler for SIGSYS displaying the error, killing the child and
* exiting.
*
*/
static void
priv_seccomp_trap_handler(int signal, siginfo_t *info, void *vctx)
{
ucontext_t *ctx = (ucontext_t *)(vctx);
unsigned int syscall;
if (trapped) _exit(161); /* Avoid loops */
/* Get details */
if (info->si_code != SYS_SECCOMP) return;
if (!ctx) _exit(161);
syscall = ctx->uc_mcontext.gregs[REG_SYSCALL];
trapped = 1;
/* Log them. Technically, `log_warnx()` is not signal safe, but we are
* unlikely to reenter here. */
log_warnx("seccomp", "invalid syscall attempted: %s(%d)",
(syscall < sizeof(syscall_names)) ? syscall_names[syscall] : "unknown",
syscall);
/* Kill children and exit */
kill(monitored, SIGTERM);
fatalx("seccomp", "invalid syscall not allowed: stop here");
_exit(161);
}
/**
* Install a TRAP action signal handler
*
* This function installs the TRAP action signal handler and is based on
* examples from Will Drewry and Kees Cook. Returns zero on success, negative
* values on failure.
*
*/
static int
priv_seccomp_trap_install()
{
struct sigaction signal_handler = {};
sigset_t signal_mask;
sigemptyset(&signal_mask);
sigaddset(&signal_mask, SIGSYS);
signal_handler.sa_sigaction = &priv_seccomp_trap_handler;
signal_handler.sa_flags = SA_SIGINFO;
if (sigaction(SIGSYS, &signal_handler, NULL) < 0) return -errno;
if (sigprocmask(SIG_UNBLOCK, &signal_mask, NULL)) return -errno;
return 0;
}
/**
* Initialize seccomp.
*
* @param remote file descriptor to talk with the unprivileged process
* @param monitored monitored child
* @return negative on failures or 0 if everything was setup
*/
int
priv_seccomp_init(int remote, int child)
{
int rc = -1;
scmp_filter_ctx ctx = NULL;
log_debug("seccomp", "initialize libseccomp filter");
monitored = child;
if (priv_seccomp_trap_install() < 0) {
log_warn("seccomp", "unable to install SIGSYS handler");
goto failure_scmp;
}
if ((ctx = seccomp_init(SCMP_ACT_TRAP)) == NULL) {
log_warnx("seccomp", "unable to initialize libseccomp subsystem");
goto failure_scmp;
}
if ((rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 1,
SCMP_CMP(0, SCMP_CMP_EQ, remote))) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1,
SCMP_CMP(0, SCMP_CMP_EQ, remote))) < 0) {
errno = -rc;
log_warn("seccomp", "unable to allow read/write on remote socket");
goto failure_scmp;
}
/* We are far more generic from here. */
if ((rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0)) <
0 || /* write needed for */
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(lseek), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(kill), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(bind), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockname), 0)) <
0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(uname), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(unlink), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sendmsg), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sendmmsg), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(wait4), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(stat), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(brk), 0)) <
0 || /* brk needed for newer libc */
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getpid), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigreturn), 0)) <
0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sendto), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(poll), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(recvmsg), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(recvfrom), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(readv), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sendmmsg), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(clock_gettime), 0)) <
0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(gettimeofday), 0)) <
0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(newfstatat), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(pread64), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(access), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), 0)) <
0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ppoll), 0)) < 0 ||
/* The following are for resolving addresses */
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(munmap), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fstat), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(connect), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 0)) < 0 ||
(rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit_group), 0)) < 0) {
errno = -rc;
log_warn("seccomp", "unable to build seccomp rules");
goto failure_scmp;
}
if ((rc = seccomp_load(ctx)) < 0) {
errno = -rc;
log_warn("seccomp", "unable to load libseccomp filter");
goto failure_scmp;
}
failure_scmp:
seccomp_release(ctx);
return rc;
}
#endif
|
