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/*
* Check verbose decoding of seccomp SECCOMP_SET_MODE_FILTER.
*
* Copyright (c) 2015-2016 Dmitry V. Levin <ldv@strace.io>
* Copyright (c) 2016-2024 The strace developers.
* All rights reserved.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "tests.h"
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/prctl.h>
#include <linux/seccomp.h>
#include <linux/filter.h>
#include "scno.h"
#if defined PR_SET_NO_NEW_PRIVS \
&& defined BPF_JUMP \
&& defined BPF_STMT
# define SOCK_FILTER_ALLOW_SYSCALL(nr) \
BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, __NR_ ## nr, 0, 1), \
BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW)
# define SOCK_FILTER_DENY_SYSCALL(nr, err) \
BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, __NR_ ## nr, 0, 1), \
BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO|(SECCOMP_RET_DATA & (err)))
# define SOCK_FILTER_KILL_PROCESS \
BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL)
# define PRINT_ALLOW_SYSCALL(nr) \
tprintf("BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, %#lx, 0, 0x1), " \
"BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), ", \
(long) __NR_ ## nr)
# define PRINT_DENY_SYSCALL(nr, err) \
tprintf("BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, %#lx, 0, 0x1), " \
"BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO|%#x), ", \
(long) __NR_ ## nr, err)
static const struct sock_filter filter_c[] = {
/* load syscall number */
BPF_STMT(BPF_LD|BPF_W|BPF_ABS, offsetof(struct seccomp_data, nr)),
/* allow syscalls */
SOCK_FILTER_ALLOW_SYSCALL(close),
SOCK_FILTER_ALLOW_SYSCALL(exit),
SOCK_FILTER_ALLOW_SYSCALL(exit_group),
/* deny syscalls */
SOCK_FILTER_DENY_SYSCALL(sync, EBUSY),
SOCK_FILTER_DENY_SYSCALL(setsid, EPERM),
/* kill process */
SOCK_FILTER_KILL_PROCESS
};
int
main(void)
{
tprintf("%s", "");
static const char kill_stmt_txt[] =
"BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL_THREAD)";
struct sock_filter *const filter =
tail_memdup(filter_c, sizeof(filter_c));
TAIL_ALLOC_OBJECT_CONST_ARR(struct sock_filter, big_filter, (BPF_MAXINSNS + 1));
TAIL_ALLOC_OBJECT_CONST_PTR(struct sock_fprog, prog);
int fds[2];
if (pipe(fds))
perror_msg_and_fail("pipe");
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0))
perror_msg_and_skip("PR_SET_NO_NEW_PRIVS");
prog->filter = filter + ARRAY_SIZE(filter_c);
prog->len = 1;
syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=1, filter=%p})"
RVAL_EFAULT, prog->filter);
prog->filter = filter + ARRAY_SIZE(filter_c) - 1;
prog->len = 3;
syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=%u"
", filter=[%s, ... /* %p */]})" RVAL_EFAULT,
prog->len, kill_stmt_txt, filter + ARRAY_SIZE(filter_c));
prog->len = 0;
syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=0, filter=[]})"
RVAL_EINVAL);
for (unsigned int i = 0; i <= BPF_MAXINSNS; ++i) {
const struct sock_filter stmt =
BPF_STMT(BPF_CLASS(i), i << 16);
big_filter[i] = stmt;
}
prog->filter = big_filter;
prog->len = BPF_MAXINSNS + 1;
tprintf("seccomp(SECCOMP_SET_MODE_FILTER, %s, {len=%u, filter=[",
"SECCOMP_FILTER_FLAG_TSYNC|SECCOMP_FILTER_FLAG_LOG|"
"SECCOMP_FILTER_FLAG_SPEC_ALLOW|"
"SECCOMP_FILTER_FLAG_NEW_LISTENER|"
"SECCOMP_FILTER_FLAG_TSYNC_ESRCH|"
"SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV|"
"0xffffffc0",
prog->len);
for (unsigned int i = 0; i < BPF_MAXINSNS; ++i) {
if (i)
tprintf(", ");
switch (BPF_CLASS(i)) {
case BPF_LD:
tprintf("BPF_STMT(BPF_LD|BPF_W|BPF_IMM, %#x)", i << 16);
break;
case BPF_LDX:
tprintf("BPF_STMT(BPF_LDX|BPF_W|BPF_IMM, %#x)", i << 16);
break;
case BPF_ST:
tprintf("BPF_STMT(BPF_ST, %#x)", i << 16);
break;
case BPF_STX:
tprintf("BPF_STMT(BPF_STX, %#x)", i << 16);
break;
case BPF_ALU:
tprintf("BPF_STMT(BPF_ALU|BPF_K|BPF_ADD, %#x)", i << 16);
break;
case BPF_JMP:
tprintf("BPF_STMT(BPF_JMP|BPF_K|BPF_JA, %#x)", i << 16);
break;
case BPF_RET:
tprintf("BPF_STMT(BPF_RET|BPF_K, %#x"
" /* SECCOMP_RET_??? */)", i << 16);
break;
case BPF_MISC:
tprintf("BPF_STMT(BPF_MISC|BPF_TAX, %#x)", i << 16);
break;
}
}
tprintf(", ...]})");
syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, -1, prog);
tprintf(RVAL_EINVAL);
prog->filter = filter;
prog->len = ARRAY_SIZE(filter_c);
tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=%u, filter=[",
prog->len);
tprintf("BPF_STMT(BPF_LD|BPF_W|BPF_ABS, %#x), ",
(unsigned) offsetof(struct seccomp_data, nr));
PRINT_ALLOW_SYSCALL(close);
PRINT_ALLOW_SYSCALL(exit);
PRINT_ALLOW_SYSCALL(exit_group);
PRINT_DENY_SYSCALL(sync, EBUSY),
PRINT_DENY_SYSCALL(setsid, EPERM),
tprintf("%s]}) = 0\n+++ exited with 0 +++\n", kill_stmt_txt);
if (syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog))
perror_msg_and_skip("SECCOMP_SET_MODE_FILTER");
if (close(0) || close(1))
_exit(77);
_exit(0);
}
#else
SKIP_MAIN_UNDEFINED("PR_SET_NO_NEW_PRIVS && BPF_JUMP && BPF_STMT")
#endif
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