elf/dl-audit.c

   1 /* Audit common functions.
   2    Copyright (C) 2021-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <link.h>
  21 #include <ldsodefs.h>
  22 #include <dl-machine.h>
  23 #include <dl-runtime.h>
  24 #include <dl-fixup-attribute.h>
  25 #include <sys/param.h>
  26
  27 void
  28 _dl_audit_activity_map (struct link_map *l, int action)
  29 {
  30   struct audit_ifaces *afct = GLRO(dl_audit);
  31   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
  32     {
  33       if (afct->activity != NULL)
  34         afct->activity (&link_map_audit_state (l, cnt)->cookie, action);
  35       afct = afct->next;
  36     }
  37 }
  38
  39 void
  40 _dl_audit_activity_nsid (Lmid_t nsid, int action)
  41 {
  42   /* If head is NULL, the namespace has become empty, and the audit interface
  43      does not give us a way to signal LA_ACT_CONSISTENT for it because the
  44      first loaded module is used to identify the namespace.  */
  45   struct link_map *head = GL(dl_ns)[nsid]._ns_loaded;
  46   if (__glibc_likely (GLRO(dl_naudit) == 0)
  47       || head == NULL || head->l_auditing)
  48     return;
  49
  50   _dl_audit_activity_map (head, action);
  51 }
  52
  53 const char *
  54 _dl_audit_objsearch (const char *name, struct link_map *l, unsigned int code)
  55 {
  56   if (l == NULL || l->l_auditing || code == 0)
  57     return name;
  58
  59   struct audit_ifaces *afct = GLRO(dl_audit);
  60   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
  61     {
  62       if (afct->objsearch != NULL)
  63         {
  64           struct auditstate *state = link_map_audit_state (l, cnt);
  65           name = afct->objsearch (name, &state->cookie, code);
  66           if (name == NULL)
  67             return NULL;
  68         }
  69       afct = afct->next;
  70    }
  71
  72   return name;
  73 }
  74
  75 void
  76 _dl_audit_objopen (struct link_map *l, Lmid_t nsid)
  77 {
  78   if (__glibc_likely (GLRO(dl_naudit) == 0))
  79     return;
  80
  81   struct audit_ifaces *afct = GLRO(dl_audit);
  82   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
  83     {
  84       if (afct->objopen != NULL)
  85         {
  86           struct auditstate *state = link_map_audit_state (l, cnt);
  87           state->bindflags = afct->objopen (l, nsid, &state->cookie);
  88           l->l_audit_any_plt |= state->bindflags != 0;
  89         }
  90
  91       afct = afct->next;
  92    }
  93 }
  94
  95 void
  96 _dl_audit_objclose (struct link_map *l)
  97 {
  98   if (__glibc_likely (GLRO(dl_naudit) == 0)
  99       || GL(dl_ns)[l->l_ns]._ns_loaded->l_auditing)
 100     return;
 101
 102   struct audit_ifaces *afct = GLRO(dl_audit);
 103   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 104     {
 105       if (afct->objclose != NULL)
 106         {
 107           struct auditstate *state= link_map_audit_state (l, cnt);
 108           /* Return value is ignored.  */
 109           afct->objclose (&state->cookie);
 110         }
 111
 112       afct = afct->next;
 113     }
 114 }
 115
 116 void
 117 _dl_audit_preinit (struct link_map *l)
 118 {
 119   if (__glibc_likely (GLRO(dl_naudit) == 0))
 120     return;
 121
 122   struct audit_ifaces *afct = GLRO(dl_audit);
 123   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 124     {
 125       if (afct->preinit != NULL)
 126         afct->preinit (&link_map_audit_state (l, cnt)->cookie);
 127       afct = afct->next;
 128     }
 129 }
 130
 131 void
 132 _dl_audit_symbind_alt (struct link_map *l, const ElfW(Sym) *ref, void **value,
 133                        lookup_t result)
 134 {
 135   if ((l->l_audit_any_plt | result->l_audit_any_plt) == 0)
 136     return;
 137
 138   const char *strtab = (const char *) D_PTR (result, l_info[DT_STRTAB]);
 139   /* Compute index of the symbol entry in the symbol table of the DSO with
 140      the definition.  */
 141   unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result, l_info[DT_SYMTAB]));
 142
 143   unsigned int altvalue = 0;
 144   /* Synthesize a symbol record where the st_value field is the result.  */
 145   ElfW(Sym) sym = *ref;
 146   sym.st_value = (ElfW(Addr)) *value;
 147
 148   struct audit_ifaces *afct = GLRO(dl_audit);
 149   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 150     {
 151       struct auditstate *match_audit = link_map_audit_state (l, cnt);
 152       struct auditstate *result_audit = link_map_audit_state (result, cnt);
 153       if (afct->symbind != NULL
 154           && ((match_audit->bindflags & LA_FLG_BINDFROM) != 0
 155               || ((result_audit->bindflags & LA_FLG_BINDTO)
 156                   != 0)))
 157         {
 158           unsigned int flags = altvalue | LA_SYMB_DLSYM;
 159           uintptr_t new_value = afct->symbind (&sym, ndx,
 160                                                &match_audit->cookie,
 161                                                &result_audit->cookie,
 162                                                &flags, strtab + ref->st_name);
 163           if (new_value != (uintptr_t) sym.st_value)
 164             {
 165               altvalue = LA_SYMB_ALTVALUE;
 166               sym.st_value = new_value;
 167             }
 168
 169           afct = afct->next;
 170         }
 171
 172       *value = (void *) sym.st_value;
 173     }
 174 }
 175 rtld_hidden_def (_dl_audit_symbind_alt)
 176
 177 void
 178 _dl_audit_symbind (struct link_map *l, struct reloc_result *reloc_result,
 179                    const ElfW(Sym) *defsym, DL_FIXUP_VALUE_TYPE *value,
 180                    lookup_t result)
 181 {
 182   bool for_jmp_slot = reloc_result == NULL;
 183
 184   /* Compute index of the symbol entry in the symbol table of the DSO
 185      with the definition.  */
 186   unsigned int boundndx = defsym - (ElfW(Sym) *) D_PTR (result,
 187                                                         l_info[DT_SYMTAB]);
 188   if (!for_jmp_slot)
 189     {
 190       reloc_result->bound = result;
 191       reloc_result->boundndx = boundndx;
 192     }
 193
 194   if ((l->l_audit_any_plt | result->l_audit_any_plt) == 0)
 195     {
 196       /* Set all bits since this symbol binding is not interesting.  */
 197       if (!for_jmp_slot)
 198         reloc_result->enterexit = (1u << DL_NNS) - 1;
 199       return;
 200     }
 201
 202   /* Synthesize a symbol record where the st_value field is the result.  */
 203   ElfW(Sym) sym = *defsym;
 204   sym.st_value = DL_FIXUP_VALUE_ADDR (*value);
 205
 206   /* Keep track whether there is any interest in tracing the call in the lower
 207      two bits.  */
 208   assert (DL_NNS * 2 <= sizeof (reloc_result->flags) * 8);
 209   assert ((LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT) == 3);
 210   uint32_t enterexit = LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT;
 211
 212   const char *strtab2 = (const void *) D_PTR (result, l_info[DT_STRTAB]);
 213
 214   unsigned int flags = 0;
 215   struct audit_ifaces *afct = GLRO(dl_audit);
 216   uintptr_t new_value = (uintptr_t) sym.st_value;
 217   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 218     {
 219       /* XXX Check whether both DSOs must request action or only one */
 220       struct auditstate *l_state = link_map_audit_state (l, cnt);
 221       struct auditstate *result_state = link_map_audit_state (result, cnt);
 222       if ((l_state->bindflags & LA_FLG_BINDFROM) != 0
 223           && (result_state->bindflags & LA_FLG_BINDTO) != 0)
 224         {
 225           if (afct->symbind != NULL)
 226             {
 227               flags |= for_jmp_slot ? LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT
 228                                     : 0;
 229               new_value = afct->symbind (&sym, boundndx,
 230                                          &l_state->cookie,
 231                                          &result_state->cookie, &flags,
 232                                          strtab2 + defsym->st_name);
 233               if (new_value != (uintptr_t) sym.st_value)
 234                 {
 235                   flags |= LA_SYMB_ALTVALUE;
 236                   sym.st_value = for_jmp_slot
 237                     ? DL_FIXUP_BINDNOW_ADDR_VALUE (new_value) : new_value;
 238                 }
 239             }
 240
 241           /* Remember the results for every audit library and store a summary
 242              in the first two bits.  */
 243           enterexit &= flags & (LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT);
 244           enterexit |= ((flags & (LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT))
 245                         << ((cnt + 1) * 2));
 246         }
 247       else
 248         /* If the bind flags say this auditor is not interested, set the bits
 249            manually.  */
 250         enterexit |= ((LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT)
 251                       << ((cnt + 1) * 2));
 252       afct = afct->next;
 253     }
 254
 255   if (!for_jmp_slot)
 256     {
 257       reloc_result->enterexit = enterexit;
 258       reloc_result->flags = flags;
 259     }
 260
 261   if (flags & LA_SYMB_ALTVALUE)
 262     DL_FIXUP_BINDNOW_RELOC (value, new_value, sym.st_value);
 263 }
 264
 265 void
 266 _dl_audit_pltenter (struct link_map *l, struct reloc_result *reloc_result,
 267                     DL_FIXUP_VALUE_TYPE *value, void *regs, long int *framesize)
 268 {
 269   /* Don't do anything if no auditor wants to intercept this call.  */
 270   if (GLRO(dl_naudit) == 0
 271       || (reloc_result->enterexit & LA_SYMB_NOPLTENTER))
 272     return;
 273
 274   /* Sanity check:  DL_FIXUP_VALUE_CODE_ADDR (value) should have been
 275      initialized earlier in this function or in another thread.  */
 276   assert (DL_FIXUP_VALUE_CODE_ADDR (*value) != 0);
 277   ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
 278                                             l_info[DT_SYMTAB])
 279                        + reloc_result->boundndx);
 280
 281   /* Set up the sym parameter.  */
 282   ElfW(Sym) sym = *defsym;
 283   sym.st_value = DL_FIXUP_VALUE_ADDR (*value);
 284
 285   /* Get the symbol name.  */
 286   const char *strtab = (const void *) D_PTR (reloc_result->bound,
 287                                              l_info[DT_STRTAB]);
 288   const char *symname = strtab + sym.st_name;
 289
 290   /* Keep track of overwritten addresses.  */
 291   unsigned int flags = reloc_result->flags;
 292
 293   struct audit_ifaces *afct = GLRO(dl_audit);
 294   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 295     {
 296       if (afct->ARCH_LA_PLTENTER != NULL
 297           && (reloc_result->enterexit
 298               & (LA_SYMB_NOPLTENTER << (2 * (cnt + 1)))) == 0)
 299         {
 300           long int new_framesize = -1;
 301           struct auditstate *l_state = link_map_audit_state (l, cnt);
 302           struct auditstate *bound_state
 303             = link_map_audit_state (reloc_result->bound, cnt);
 304           uintptr_t new_value
 305             = afct->ARCH_LA_PLTENTER (&sym, reloc_result->boundndx,
 306                                       &l_state->cookie, &bound_state->cookie,
 307                                       regs, &flags, symname, &new_framesize);
 308           if (new_value != (uintptr_t) sym.st_value)
 309             {
 310               flags |= LA_SYMB_ALTVALUE;
 311               sym.st_value = new_value;
 312             }
 313
 314           /* Remember the results for every audit library and store a summary
 315              in the first two bits.  */
 316           reloc_result->enterexit |= ((flags & (LA_SYMB_NOPLTENTER
 317                                                 | LA_SYMB_NOPLTEXIT))
 318                                       << (2 * (cnt + 1)));
 319
 320           if ((reloc_result->enterexit & (LA_SYMB_NOPLTEXIT
 321                                           << (2 * (cnt + 1))))
 322               == 0 && new_framesize != -1 && *framesize != -2)
 323             {
 324               /* If this is the first call providing information, use it.  */
 325               if (*framesize == -1)
 326                 *framesize = new_framesize;
 327               /* If two pltenter calls provide conflicting information, use
 328                  the larger value.  */
 329               else if (new_framesize != *framesize)
 330                 *framesize = MAX (new_framesize, *framesize);
 331             }
 332         }
 333
 334       afct = afct->next;
 335     }
 336
 337   *value = DL_FIXUP_ADDR_VALUE (sym.st_value);
 338 }
 339
 340 void
 341 DL_ARCH_FIXUP_ATTRIBUTE
 342 _dl_audit_pltexit (struct link_map *l, ElfW(Word) reloc_arg,
 343                    const void *inregs, void *outregs)
 344 {
 345   const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
 346
 347   /* This is the address in the array where we store the result of previous
 348      relocations.  */
 349   // XXX Maybe the bound information must be stored on the stack since
 350   // XXX with bind_not a new value could have been stored in the meantime.
 351   struct reloc_result *reloc_result =
 352     &l->l_reloc_result[reloc_index (pltgot, reloc_arg, sizeof (PLTREL))];
 353   ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
 354                                             l_info[DT_SYMTAB])
 355                        + reloc_result->boundndx);
 356
 357   /* Set up the sym parameter.  */
 358   ElfW(Sym) sym = *defsym;
 359   sym.st_value = DL_FIXUP_VALUE_ADDR (reloc_result->addr);
 360
 361   /* Get the symbol name.  */
 362   const char *strtab = (const void *) D_PTR (reloc_result->bound,
 363                                              l_info[DT_STRTAB]);
 364   const char *symname = strtab + sym.st_name;
 365
 366   struct audit_ifaces *afct = GLRO(dl_audit);
 367   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 368     {
 369       if (afct->ARCH_LA_PLTEXIT != NULL
 370           && (reloc_result->enterexit
 371               & (LA_SYMB_NOPLTEXIT >> (2 * cnt))) == 0)
 372         {
 373           struct auditstate *l_state = link_map_audit_state (l, cnt);
 374           struct auditstate *bound_state
 375             = link_map_audit_state (reloc_result->bound, cnt);
 376           afct->ARCH_LA_PLTEXIT (&sym, reloc_result->boundndx,
 377                                  &l_state->cookie, &bound_state->cookie,
 378                                  inregs, outregs, symname);
 379         }
 380
 381       afct = afct->next;
 382     }
 383 }