granicus.if.org Git - strace/blob - tests/seccomp-filter-v.c

   1 /*
   2  * Check verbose decoding of seccomp SECCOMP_SET_MODE_FILTER.
   3  *
   4  * Copyright (c) 2015-2016 Dmitry V. Levin <ldv@altlinux.org>
   5  * Copyright (c) 2016-2017 The strace developers.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. The name of the author may not be used to endorse or promote products
  17  *    derived from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include "tests.h"
  32
  33 #include <errno.h>
  34 #include <stddef.h>
  35 #include <stdio.h>
  36 #include <asm/unistd.h>
  37 #include <unistd.h>
  38
  39 #ifdef HAVE_PRCTL
  40 # include <sys/prctl.h>
  41 #endif
  42 #ifdef HAVE_LINUX_SECCOMP_H
  43 # include <linux/seccomp.h>
  44 #endif
  45 #include <linux/filter.h>
  46
  47 #if defined __NR_seccomp \
  48  && defined PR_SET_NO_NEW_PRIVS \
  49  && defined SECCOMP_SET_MODE_FILTER \
  50  && defined SECCOMP_RET_ERRNO \
  51  && defined BPF_JUMP \
  52  && defined BPF_STMT
  53
  54 #define SOCK_FILTER_ALLOW_SYSCALL(nr) \
  55                 BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, __NR_ ## nr, 0, 1), \
  56                 BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW)
  57
  58 #define SOCK_FILTER_DENY_SYSCALL(nr, err) \
  59                 BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, __NR_ ## nr, 0, 1), \
  60                 BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO|(SECCOMP_RET_DATA & (err)))
  61
  62 #define SOCK_FILTER_KILL_PROCESS \
  63                 BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL)
  64
  65 #define PRINT_ALLOW_SYSCALL(nr) \
  66         tprintf("BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, %#x, 0, 0x1), " \
  67                "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), ", \
  68                __NR_ ## nr)
  69
  70 #define PRINT_DENY_SYSCALL(nr, err) \
  71         tprintf("BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, %#x, 0, 0x1), " \
  72                "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO|%#x), ", \
  73                __NR_ ## nr, err)
  74
  75 static const struct sock_filter filter_c[] = {
  76         /* load syscall number */
  77         BPF_STMT(BPF_LD|BPF_W|BPF_ABS, offsetof(struct seccomp_data, nr)),
  78
  79         /* allow syscalls */
  80         SOCK_FILTER_ALLOW_SYSCALL(close),
  81         SOCK_FILTER_ALLOW_SYSCALL(exit),
  82         SOCK_FILTER_ALLOW_SYSCALL(exit_group),
  83
  84         /* deny syscalls */
  85         SOCK_FILTER_DENY_SYSCALL(sync, EBUSY),
  86         SOCK_FILTER_DENY_SYSCALL(setsid, EPERM),
  87
  88         /* kill process */
  89         SOCK_FILTER_KILL_PROCESS
  90 };
  91
  92 int
  93 main(void)
  94 {
  95         tprintf("%s", "");
  96
  97         static const char kill_stmt_txt[] =
  98                 "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL)";
  99         struct sock_filter *const filter =
 100                 tail_memdup(filter_c, sizeof(filter_c));
 101         struct sock_filter *const big_filter =
 102                 tail_alloc(sizeof(*big_filter) * (BPF_MAXINSNS + 1));
 103         TAIL_ALLOC_OBJECT_CONST_PTR(struct sock_fprog, prog);
 104
 105         int fds[2];
 106         if (pipe(fds))
 107                 perror_msg_and_fail("pipe");
 108         if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0))
 109                 perror_msg_and_skip("PR_SET_NO_NEW_PRIVS");
 110
 111         prog->filter = filter +  ARRAY_SIZE(filter_c);
 112         prog->len = 1;
 113         syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
 114         tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=1, filter=%p})"
 115                 " = -1 EFAULT (%m)\n", prog->filter);
 116
 117         prog->filter = filter +  ARRAY_SIZE(filter_c) - 1;
 118         prog->len = 3;
 119         syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
 120         tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=%u"
 121                 ", filter=[%s, %p]}) = -1 EFAULT (%m)\n",
 122                 prog->len, kill_stmt_txt, filter +  ARRAY_SIZE(filter_c));
 123
 124         prog->len = 0;
 125         syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
 126         tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=0, filter=[]})"
 127                 " = -1 EINVAL (%m)\n");
 128
 129         unsigned int i;
 130         for (i = 0; i <= BPF_MAXINSNS; ++i) {
 131                 const struct sock_filter stmt =
 132                         BPF_STMT(BPF_CLASS(i), i << 16);
 133                 big_filter[i] = stmt;
 134         }
 135
 136         prog->filter = big_filter;
 137         prog->len = BPF_MAXINSNS + 1;
 138         tprintf("seccomp(SECCOMP_SET_MODE_FILTER, %s, {len=%u, filter=[",
 139                 "SECCOMP_FILTER_FLAG_TSYNC|SECCOMP_FILTER_FLAG_LOG|0xfffffffc",
 140                 prog->len);
 141         for (i = 0; i < BPF_MAXINSNS; ++i) {
 142                 if (i)
 143                         tprintf(", ");
 144                 switch (BPF_CLASS(i)) {
 145                 case BPF_LD:
 146                         tprintf("BPF_STMT(BPF_LD|BPF_W|BPF_IMM, %#x)", i << 16);
 147                         break;
 148                 case BPF_LDX:
 149                         tprintf("BPF_STMT(BPF_LDX|BPF_W|BPF_IMM, %#x)", i << 16);
 150                         break;
 151                 case BPF_ST:
 152                         tprintf("BPF_STMT(BPF_ST, %#x)", i << 16);
 153                         break;
 154                 case BPF_STX:
 155                         tprintf("BPF_STMT(BPF_STX, %#x)", i << 16);
 156                         break;
 157                 case BPF_ALU:
 158                         tprintf("BPF_STMT(BPF_ALU|BPF_K|BPF_ADD, %#x)", i << 16);
 159                         break;
 160                 case BPF_JMP:
 161                         tprintf("BPF_STMT(BPF_JMP|BPF_K|BPF_JA, %#x)", i << 16);
 162                         break;
 163                 case BPF_RET:
 164                         tprintf("BPF_STMT(BPF_RET|BPF_K, %#x"
 165                                 " /* SECCOMP_RET_??? */)", i << 16);
 166                         break;
 167                 case BPF_MISC:
 168                         tprintf("BPF_STMT(BPF_MISC|BPF_TAX, %#x)", i << 16);
 169                         break;
 170                 }
 171         }
 172         tprintf(", ...]})");
 173         syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, -1, prog);
 174         tprintf(" = -1 EINVAL (%m)\n");
 175
 176         prog->filter = filter;
 177         prog->len = ARRAY_SIZE(filter_c);
 178
 179         tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=%u, filter=[",
 180                 prog->len);
 181
 182         tprintf("BPF_STMT(BPF_LD|BPF_W|BPF_ABS, %#x), ",
 183                (unsigned) offsetof(struct seccomp_data, nr));
 184
 185         PRINT_ALLOW_SYSCALL(close);
 186         PRINT_ALLOW_SYSCALL(exit);
 187         PRINT_ALLOW_SYSCALL(exit_group);
 188
 189         PRINT_DENY_SYSCALL(sync, EBUSY),
 190         PRINT_DENY_SYSCALL(setsid, EPERM),
 191
 192         tprintf("%s]}) = 0\n+++ exited with 0 +++\n", kill_stmt_txt);
 193
 194         if (syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog))
 195                 perror_msg_and_skip("SECCOMP_SET_MODE_FILTER");
 196
 197         if (close(0) || close(1))
 198                 _exit(77);
 199
 200         _exit(0);
 201 }
 202
 203 #else
 204
 205 SKIP_MAIN_UNDEFINED("__NR_seccomp && PR_SET_NO_NEW_PRIVS"
 206                     " && SECCOMP_SET_MODE_FILTER && SECCOMP_RET_ERRNO"
 207                     " && BPF_JUMP && BPF_STMT")
 208
 209 #endif