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 #endif /* HAVE_LINUX_FILTER_H */
 112
 113 static void
 114 decode_bpf_stmt(const struct bpf_filter *filter)
 115 {
 116 #ifdef HAVE_LINUX_FILTER_H
 117         tprints("BPF_STMT(");
 118         decode_bpf_code(filter->code);
 119         tprints(", ");
 120         if (BPF_CLASS(filter->code) == BPF_RET) {
 121                 unsigned int action = SECCOMP_RET_ACTION & filter->k;
 122                 unsigned int data = filter->k & ~action;
 123
 124                 printxval(seccomp_ret_action, action, "SECCOMP_RET_???");
 125                 if (data)
 126                         tprintf("|%#x)", data);
 127                 else
 128                         tprints(")");
 129         } else {
 130                 tprintf("%#x)", filter->k);
 131         }
 132 #else
 133         tprintf("BPF_STMT(%#x, %#x)", filter->code, filter->k);
 134 #endif /* HAVE_LINUX_FILTER_H */
 135 }
 136
 137 static void
 138 decode_bpf_jump(const struct bpf_filter *filter)
 139 {
 140 #ifdef HAVE_LINUX_FILTER_H
 141         tprints("BPF_JUMP(");
 142         decode_bpf_code(filter->code);
 143         tprintf(", %#x, %#x, %#x)",
 144                 filter->k, filter->jt, filter->jf);
 145 #else
 146         tprintf("BPF_JUMP(%#x, %#x, %#x, %#x)",
 147                 filter->code, filter->k, filter->jt, filter->jf);
 148 #endif /* HAVE_LINUX_FILTER_H */
 149 }
 150
 151 #ifndef BPF_MAXINSNS
 152 # define BPF_MAXINSNS 4096
 153 #endif
 154
 155 static bool
 156 print_bpf_filter(struct tcb *tcp, void *elem_buf, size_t elem_size, void *data)
 157 {
 158         const struct bpf_filter *filter = elem_buf;
 159         unsigned int *pn = data;
 160
 161         if ((*pn)++ >= BPF_MAXINSNS) {
 162                 tprints("...");
 163                 return false;
 164         }
 165
 166         if (filter->jt || filter->jf)
 167                 decode_bpf_jump(filter);
 168         else
 169                 decode_bpf_stmt(filter);
 170
 171         return true;
 172 }
 173
 174 void
 175 print_seccomp_fprog(struct tcb *const tcp, const kernel_ureg_t addr,
 176                     const unsigned short len)
 177 {
 178         if (abbrev(tcp)) {
 179                 printaddr(addr);
 180         } else {
 181                 unsigned int insns = 0;
 182                 struct bpf_filter filter;
 183
 184                 print_array(tcp, addr, len, &filter, sizeof(filter),
 185                             umoven_or_printaddr, print_bpf_filter, &insns);
 186         }
 187 }
 188
 189 #include "seccomp_fprog.h"
 190
 191 void
 192 print_seccomp_filter(struct tcb *const tcp, const kernel_ureg_t addr)
 193 {
 194         struct seccomp_fprog fprog;
 195
 196         if (fetch_seccomp_fprog(tcp, addr, &fprog)) {
 197                 tprintf("{len=%hu, filter=", fprog.len);
 198                 print_seccomp_fprog(tcp, fprog.filter, fprog.len);
 199                 tprints("}");
 200         }
 201 }
 202
 203 static void
 204 decode_seccomp_set_mode_strict(const unsigned int flags,
 205                                const kernel_ureg_t addr)
 206 {
 207         tprintf("%u, ", flags);
 208         printaddr(addr);
 209 }
 210
 211 SYS_FUNC(seccomp)
 212 {
 213         unsigned int op = tcp->u_arg[0];
 214
 215         printxval(seccomp_ops, op, "SECCOMP_SET_MODE_???");
 216         tprints(", ");
 217
 218         if (op == SECCOMP_SET_MODE_FILTER) {
 219                 printflags(seccomp_filter_flags, tcp->u_arg[1],
 220                            "SECCOMP_FILTER_FLAG_???");
 221                 tprints(", ");
 222                 print_seccomp_filter(tcp, tcp->u_arg[2]);
 223         } else {
 224                 decode_seccomp_set_mode_strict(tcp->u_arg[1],
 225                                                tcp->u_arg[2]);
 226         }
 227
 228         return RVAL_DECODED;
 229 }