LXR linux/samples/seccomp/bpf-fancy.c

   1/*
   2 * Seccomp BPF example using a macro-based generator.
   3 *
   4 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
   5 * Author: Will Drewry <wad@chromium.org>
   6 *
   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_ATTACH_SECCOMP_FILTER).
  10 */
  11
  12#include <linux/filter.h>
  13#include <linux/seccomp.h>
  14#include <linux/unistd.h>
  15#include <stdio.h>
  16#include <string.h>
  17#include <sys/prctl.h>
  18#include <unistd.h>
  19
  20#include "bpf-helper.h"
  21
  22#ifndef PR_SET_NO_NEW_PRIVS
  23#define PR_SET_NO_NEW_PRIVS 38
  24#endif
  25
  26int main(int argc, char **argv)
  27{
  28        struct bpf_labels l = {
  29                .count = 0,
  30        };
  31        static const char msg1[] = "Please type something: ";
  32        static const char msg2[] = "You typed: ";
  33        char buf[256];
  34        struct sock_filter filter[] = {
  35                /* TODO: LOAD_SYSCALL_NR(arch) and enforce an arch */
  36                LOAD_SYSCALL_NR,
  37                SYSCALL(__NR_exit, ALLOW),
  38                SYSCALL(__NR_exit_group, ALLOW),
  39                SYSCALL(__NR_write, JUMP(&l, write_fd)),
  40                SYSCALL(__NR_read, JUMP(&l, read)),
  41                DENY,  /* Don't passthrough into a label */
  42
  43                LABEL(&l, read),
  44                ARG(0),
  45                JNE(STDIN_FILENO, DENY),
  46                ARG(1),
  47                JNE((unsigned long)buf, DENY),
  48                ARG(2),
  49                JGE(sizeof(buf), DENY),
  50                ALLOW,
  51
  52                LABEL(&l, write_fd),
  53                ARG(0),
  54                JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),
  55                JEQ(STDERR_FILENO, JUMP(&l, write_buf)),
  56                DENY,
  57
  58                LABEL(&l, write_buf),
  59                ARG(1),
  60                JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),
  61                JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),
  62                JEQ((unsigned long)buf, JUMP(&l, buf_len)),
  63                DENY,
  64
  65                LABEL(&l, msg1_len),
  66                ARG(2),
  67                JLT(sizeof(msg1), ALLOW),
  68                DENY,
  69
  70                LABEL(&l, msg2_len),
  71                ARG(2),
  72                JLT(sizeof(msg2), ALLOW),
  73                DENY,
  74
  75                LABEL(&l, buf_len),
  76                ARG(2),
  77                JLT(sizeof(buf), ALLOW),
  78                DENY,
  79        };
  80        struct sock_fprog prog = {
  81                .filter = filter,
  82                .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
  83        };
  84        ssize_t bytes;
  85        bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*filter));
  86
  87        if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
  88                perror("prctl(NO_NEW_PRIVS)");
  89                return 1;
  90        }
  91
  92        if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
  93                perror("prctl(SECCOMP)");
  94                return 1;
  95        }
  96        syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));
  97        bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);
  98        bytes = (bytes > 0 ? bytes : 0);
  99        syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));
 100        syscall(__NR_write, STDERR_FILENO, buf, bytes);
 101        /* Now get killed */
 102        syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);
 103        return 0;
 104}
 105