2 * Naive system call dropper built on seccomp_filter.
4 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
5 * Author: Will Drewry <wad@chromium.org>
7 * The code may be used by anyone for any purpose,
8 * and can serve as a starting point for developing
9 * applications using prctl(PR_SET_SECCOMP, 2, ...).
11 * When run, returns the specified errno for the specified
12 * system call number against the given architecture.
14 * Run this one as root as PR_SET_NO_NEW_PRIVS is not called.
18 #include <linux/audit.h>
19 #include <linux/filter.h>
20 #include <linux/seccomp.h>
21 #include <linux/unistd.h>
25 #include <sys/prctl.h>
28 static int install_filter(int nr, int arch, int error)
30 struct sock_filter filter[] = {
31 BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
32 (offsetof(struct seccomp_data, arch))),
33 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, arch, 0, 3),
34 BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
35 (offsetof(struct seccomp_data, nr))),
36 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1),
37 BPF_STMT(BPF_RET+BPF_K,
38 SECCOMP_RET_ERRNO|(error & SECCOMP_RET_DATA)),
39 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
41 struct sock_fprog prog = {
42 .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
45 if (prctl(PR_SET_SECCOMP, 2, &prog)) {
52 int main(int argc, char **argv)
55 fprintf(stderr, "Usage:\n"
56 "dropper <syscall_nr> <arch> <errno> <prog> [<args>]\n"
57 "Hint: AUDIT_ARCH_I386: 0x%X\n"
58 " AUDIT_ARCH_X86_64: 0x%X\n"
59 "\n", AUDIT_ARCH_I386, AUDIT_ARCH_X86_64);
62 if (install_filter(strtol(argv[1], NULL, 0), strtol(argv[2], NULL, 0),
63 strtol(argv[3], NULL, 0)))
65 execv(argv[4], &argv[4]);
66 printf("Failed to execv\n");