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

   1 /*
   2  * Copyright (c) 2015 Dmitry V. Levin <ldv@altlinux.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. The name of the author may not be used to endorse or promote products
  14  *    derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #include "defs.h"
  29
  30 #ifdef HAVE_LINUX_SECCOMP_H
  31 # include <linux/seccomp.h>
  32 #endif
  33 #include "xlat/seccomp_ops.h"
  34 #include "xlat/seccomp_filter_flags.h"
  35
  36 #ifdef HAVE_LINUX_FILTER_H
  37 # include <linux/filter.h>
  38 # include "xlat/bpf_class.h"
  39 # include "xlat/bpf_miscop.h"
  40 # include "xlat/bpf_mode.h"
  41 # include "xlat/bpf_op_alu.h"
  42 # include "xlat/bpf_op_jmp.h"
  43 # include "xlat/bpf_rval.h"
  44 # include "xlat/bpf_size.h"
  45 # include "xlat/bpf_src.h"
  46
  47 # ifndef SECCOMP_RET_ACTION
  48 #  define SECCOMP_RET_ACTION 0x7fff0000U
  49 # endif
  50 # include "xlat/seccomp_ret_action.h"
  51 #endif
  52
  53 struct bpf_filter {
  54         uint16_t code;
  55         uint8_t jt;
  56         uint8_t jf;
  57         uint32_t k;
  58 };
  59
  60 #ifdef HAVE_LINUX_FILTER_H
  61
  62 static void
  63 decode_bpf_code(uint16_t code)
  64 {
  65         uint16_t i = code & ~BPF_CLASS(code);
  66
  67         printxval(bpf_class, BPF_CLASS(code), "BPF_???");
  68         switch (BPF_CLASS(code)) {
  69                 case BPF_LD:
  70                 case BPF_LDX:
  71                         tprints(" | ");
  72                         printxval(bpf_size, BPF_SIZE(code), "BPF_???");
  73                         tprints(" | ");
  74                         printxval(bpf_mode, BPF_MODE(code), "BPF_???");
  75                         break;
  76                 case BPF_ST:
  77                 case BPF_STX:
  78                         if (i)
  79                                 tprintf(" | %#x /* %s */", i, "BPF_???");
  80                         break;
  81                 case BPF_ALU:
  82                         tprints(" | ");
  83                         printxval(bpf_src, BPF_SRC(code), "BPF_???");
  84                         tprints(" | ");
  85                         printxval(bpf_op_alu, BPF_OP(code), "BPF_???");
  86                         break;
  87                 case BPF_JMP:
  88                         tprints(" | ");
  89                         printxval(bpf_src, BPF_SRC(code), "BPF_???");
  90                         tprints(" | ");
  91                         printxval(bpf_op_jmp, BPF_OP(code), "BPF_???");
  92                         break;
  93                 case BPF_RET:
  94                         tprints(" | ");
  95                         printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
  96                         i &= ~BPF_RVAL(code);
  97                         if (i)
  98                                 tprintf(" | %#x /* %s */", i, "BPF_???");
  99                         break;
 100                 case BPF_MISC:
 101                         tprints(" | ");
 102                         printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
 103                         i &= ~BPF_MISCOP(code);
 104                         if (i)
 105                                 tprintf(" | %#x /* %s */", i, "BPF_???");
 106                         break;
 107         }
 108
 109 }
 110
 111 static void
 112 decode_bpf_stmt(const struct bpf_filter *filter)
 113 {
 114 #ifdef HAVE_LINUX_FILTER_H
 115         tprints("BPF_STMT(");
 116         decode_bpf_code(filter->code);
 117         tprints(", ");
 118         if (BPF_CLASS(filter->code) == BPF_RET) {
 119                 unsigned int action = SECCOMP_RET_ACTION & filter->k;
 120                 unsigned int data = filter->k & ~action;
 121
 122                 printxval(seccomp_ret_action, action, "SECCOMP_RET_???");
 123                 if (data)
 124                         tprintf(" | %#x)", data);
 125                 else
 126                         tprints(")");
 127         } else {
 128                 tprintf("%#x)", filter->k);
 129         }
 130 #else
 131         tprintf("BPF_STMT(%#x, %#x)", filter->code, filter->k);
 132 #endif /* HAVE_LINUX_FILTER_H */
 133 }
 134
 135 static void
 136 decode_bpf_jump(const struct bpf_filter *filter)
 137 {
 138 #ifdef HAVE_LINUX_FILTER_H
 139         tprints("BPF_JUMP(");
 140         decode_bpf_code(filter->code);
 141         tprintf(", %#x, %#x, %#x)",
 142                 filter->k, filter->jt, filter->jf);
 143 #else
 144         tprintf("BPF_JUMP(%#x, %#x, %#x, %#x)",
 145                 filter->code, filter->k, filter->jt, filter->jf);
 146 #endif /* HAVE_LINUX_FILTER_H */
 147 }
 148
 149 static void
 150 decode_filter(const struct bpf_filter *filter)
 151 {
 152         if (filter->jt || filter->jf)
 153                 decode_bpf_jump(filter);
 154         else
 155                 decode_bpf_stmt(filter);
 156 }
 157
 158 #endif /* HAVE_LINUX_FILTER_H */
 159
 160 #ifndef BPF_MAXINSNS
 161 # define BPF_MAXINSNS 4096
 162 #endif
 163
 164 static void
 165 decode_fprog(struct tcb *tcp, unsigned short len, unsigned long addr)
 166 {
 167         if (!len || abbrev(tcp)) {
 168                 tprintf("{len = %u, filter = %#lx}", len, addr);
 169         } else {
 170                 unsigned int i = 0;
 171
 172                 tprints("[");
 173                 while (i < len && i < BPF_MAXINSNS) {
 174                         struct bpf_filter filter;
 175
 176                         if (umove(tcp, addr, &filter) < 0)
 177                                 break;
 178                         if (i)
 179                                 tprints(", ");
 180                         decode_filter(&filter);
 181
 182                         addr += sizeof(filter);
 183                         ++i;
 184                 }
 185                 if (i < len)
 186                         tprints("...");
 187                 tprints("]");
 188         }
 189 }
 190
 191 void
 192 print_seccomp_filter(struct tcb *tcp, unsigned long addr)
 193 {
 194         if (addr) {
 195 #if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
 196                 if (current_wordsize == 4) {
 197                         struct {
 198                                 unsigned short len;
 199                                 uint32_t filter;
 200                         } fprog;
 201                         if (umove(tcp, addr, &fprog) < 0)
 202                                 tprintf("%#lx", addr);
 203                         else
 204                                 decode_fprog(tcp, fprog.len, fprog.filter);
 205                 } else {
 206 #endif
 207                         struct {
 208                                 unsigned short len;
 209                                 unsigned long filter;
 210                         } fprog;
 211                         if (umove(tcp, addr, &fprog) < 0)
 212                                 tprintf("%#lx", addr);
 213                         else
 214                                 decode_fprog(tcp, fprog.len, fprog.filter);
 215 #if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
 216                 }
 217 #endif
 218         } else {
 219                 tprints("NULL");
 220         }
 221 }
 222
 223 static void
 224 decode_seccomp_set_mode_strict(unsigned int flags, unsigned long addr)
 225 {
 226         tprintf("%u, ", flags);
 227         if (addr)
 228                 tprintf("%#lx", addr);
 229         else
 230                 tprints("NULL");
 231 }
 232
 233 int
 234 sys_seccomp(struct tcb *tcp)
 235 {
 236         if (entering(tcp)) {
 237                 unsigned int op = tcp->u_arg[0];
 238
 239                 printxval(seccomp_ops, op, "SECCOMP_SET_MODE_???");
 240                 tprints(", ");
 241
 242                 if (op == SECCOMP_SET_MODE_FILTER) {
 243                         printflags(seccomp_filter_flags, tcp->u_arg[1],
 244                                    "SECCOMP_FILTER_FLAG_???");
 245                         tprints(", ");
 246                         print_seccomp_filter(tcp, tcp->u_arg[2]);
 247                 } else {
 248                         decode_seccomp_set_mode_strict(tcp->u_arg[1],
 249                                                        tcp->u_arg[2]);
 250                 }
 251         }
 252         return 0;
 253 }