granicus.if.org Git - strace/blob - seccomp.c

   1 /*
   2  * Copyright (c) 2015 Dmitry V. Levin <ldv@altlinux.org>
   3  * Copyright (c) 2015-2017 The strace developers.
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. The name of the author may not be used to endorse or promote products
  15  *    derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include "defs.h"
  30
  31 #ifdef HAVE_LINUX_SECCOMP_H
  32 # include <linux/seccomp.h>
  33 #endif
  34 #include "xlat/seccomp_ops.h"
  35 #include "xlat/seccomp_filter_flags.h"
  36
  37 #ifdef HAVE_LINUX_FILTER_H
  38 # include <linux/filter.h>
  39 # include "xlat/bpf_class.h"
  40 # include "xlat/bpf_miscop.h"
  41 # include "xlat/bpf_mode.h"
  42 # include "xlat/bpf_op_alu.h"
  43 # include "xlat/bpf_op_jmp.h"
  44 # include "xlat/bpf_rval.h"
  45 # include "xlat/bpf_size.h"
  46 # include "xlat/bpf_src.h"
  47
  48 # ifndef SECCOMP_RET_ACTION
  49 #  define SECCOMP_RET_ACTION 0x7fff0000U
  50 # endif
  51 # include "xlat/seccomp_ret_action.h"
  52 #endif
  53
  54 struct bpf_filter {
  55         uint16_t code;
  56         uint8_t jt;
  57         uint8_t jf;
  58         uint32_t k;
  59 };
  60
  61 #ifdef HAVE_LINUX_FILTER_H
  62
  63 static void
  64 decode_bpf_code(uint16_t code)
  65 {
  66         uint16_t i = code & ~BPF_CLASS(code);
  67
  68         printxval(bpf_class, BPF_CLASS(code), "BPF_???");
  69         switch (BPF_CLASS(code)) {
  70                 case BPF_LD:
  71                 case BPF_LDX:
  72                         tprints("|");
  73                         printxval(bpf_size, BPF_SIZE(code), "BPF_???");
  74                         tprints("|");
  75                         printxval(bpf_mode, BPF_MODE(code), "BPF_???");
  76                         break;
  77                 case BPF_ST:
  78                 case BPF_STX:
  79                         if (i) {
  80                                 tprintf("|%#x", i);
  81                                 tprints_comment("BPF_???");
  82                         }
  83                         break;
  84                 case BPF_ALU:
  85                         tprints("|");
  86                         printxval(bpf_src, BPF_SRC(code), "BPF_???");
  87                         tprints("|");
  88                         printxval(bpf_op_alu, BPF_OP(code), "BPF_???");
  89                         break;
  90                 case BPF_JMP:
  91                         tprints("|");
  92                         printxval(bpf_src, BPF_SRC(code), "BPF_???");
  93                         tprints("|");
  94                         printxval(bpf_op_jmp, BPF_OP(code), "BPF_???");
  95                         break;
  96                 case BPF_RET:
  97                         tprints("|");
  98                         printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
  99                         i &= ~BPF_RVAL(code);
 100                         if (i) {
 101                                 tprintf("|%#x", i);
 102                                 tprints_comment("BPF_???");
 103                         }
 104                         break;
 105                 case BPF_MISC:
 106                         tprints("|");
 107                         printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
 108                         i &= ~BPF_MISCOP(code);
 109                         if (i) {
 110                                 tprintf("|%#x", i);
 111                                 tprints_comment("BPF_???");
 112                         }
 113                         break;
 114         }
 115
 116 }
 117
 118 #endif /* HAVE_LINUX_FILTER_H */
 119
 120 static void
 121 decode_bpf_stmt(const struct bpf_filter *filter)
 122 {
 123 #ifdef HAVE_LINUX_FILTER_H
 124         tprints("BPF_STMT(");
 125         decode_bpf_code(filter->code);
 126         tprints(", ");
 127         if (BPF_CLASS(filter->code) == BPF_RET) {
 128                 unsigned int action = SECCOMP_RET_ACTION & filter->k;
 129                 unsigned int data = filter->k & ~action;
 130
 131                 printxval(seccomp_ret_action, action, "SECCOMP_RET_???");
 132                 if (data)
 133                         tprintf("|%#x)", data);
 134                 else
 135                         tprints(")");
 136         } else {
 137                 tprintf("%#x)", filter->k);
 138         }
 139 #else
 140         tprintf("BPF_STMT(%#x, %#x)", filter->code, filter->k);
 141 #endif /* HAVE_LINUX_FILTER_H */
 142 }
 143
 144 static void
 145 decode_bpf_jump(const struct bpf_filter *filter)
 146 {
 147 #ifdef HAVE_LINUX_FILTER_H
 148         tprints("BPF_JUMP(");
 149         decode_bpf_code(filter->code);
 150         tprintf(", %#x, %#x, %#x)",
 151                 filter->k, filter->jt, filter->jf);
 152 #else
 153         tprintf("BPF_JUMP(%#x, %#x, %#x, %#x)",
 154                 filter->code, filter->k, filter->jt, filter->jf);
 155 #endif /* HAVE_LINUX_FILTER_H */
 156 }
 157
 158 #ifndef BPF_MAXINSNS
 159 # define BPF_MAXINSNS 4096
 160 #endif
 161
 162 static bool
 163 print_bpf_filter(struct tcb *tcp, void *elem_buf, size_t elem_size, void *data)
 164 {
 165         const struct bpf_filter *filter = elem_buf;
 166         unsigned int *pn = data;
 167
 168         if ((*pn)++ >= BPF_MAXINSNS) {
 169                 tprints("...");
 170                 return false;
 171         }
 172
 173         if (filter->jt || filter->jf)
 174                 decode_bpf_jump(filter);
 175         else
 176                 decode_bpf_stmt(filter);
 177
 178         return true;
 179 }
 180
 181 void
 182 print_seccomp_fprog(struct tcb *const tcp, const kernel_ulong_t addr,
 183                     const unsigned short len)
 184 {
 185         if (abbrev(tcp)) {
 186                 printaddr(addr);
 187         } else {
 188                 unsigned int insns = 0;
 189                 struct bpf_filter filter;
 190
 191                 print_array(tcp, addr, len, &filter, sizeof(filter),
 192                             umoven_or_printaddr, print_bpf_filter, &insns);
 193         }
 194 }
 195
 196 #include "seccomp_fprog.h"
 197
 198 void
 199 print_seccomp_filter(struct tcb *const tcp, const kernel_ulong_t addr)
 200 {
 201         struct seccomp_fprog fprog;
 202
 203         if (fetch_seccomp_fprog(tcp, addr, &fprog)) {
 204                 tprintf("{len=%hu, filter=", fprog.len);
 205                 print_seccomp_fprog(tcp, fprog.filter, fprog.len);
 206                 tprints("}");
 207         }
 208 }
 209
 210 static void
 211 decode_seccomp_set_mode_strict(const unsigned int flags,
 212                                const kernel_ulong_t addr)
 213 {
 214         tprintf("%u, ", flags);
 215         printaddr(addr);
 216 }
 217
 218 SYS_FUNC(seccomp)
 219 {
 220         unsigned int op = tcp->u_arg[0];
 221
 222         printxval(seccomp_ops, op, "SECCOMP_SET_MODE_???");
 223         tprints(", ");
 224
 225         if (op == SECCOMP_SET_MODE_FILTER) {
 226                 printflags(seccomp_filter_flags, tcp->u_arg[1],
 227                            "SECCOMP_FILTER_FLAG_???");
 228                 tprints(", ");
 229                 print_seccomp_filter(tcp, tcp->u_arg[2]);
 230         } else {
 231                 decode_seccomp_set_mode_strict(tcp->u_arg[1],
 232                                                tcp->u_arg[2]);
 233         }
 234
 235         return RVAL_DECODED;
 236 }