Line data    Source code

       1             : /*
       2             :  * Copyright (c) 2016 - 2017 Kungliga Tekniska Högskolan
       3             :  * (Royal Institute of Technology, Stockholm, Sweden).
       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             :  *
      10             :  * 1. Redistributions of source code must retain the above copyright
      11             :  *    notice, this list of conditions and the following disclaimer.
      12             :  *
      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             :  *
      17             :  * 3. Neither the name of the Institute nor the names of its contributors
      18             :  *    may be used to endorse or promote products derived from this software
      19             :  *    without specific prior written permission.
      20             :  *
      21             :  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
      22             :  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
      23             :  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
      24             :  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
      25             :  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
      26             :  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
      27             :  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
      28             :  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
      29             :  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
      30             :  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
      31             :  * SUCH DAMAGE.
      32             :  */
      33             : 
      34             : #include <config.h>
      35             : 
      36             : #ifdef HAVE_SYS_AUXV_H
      37             : #include <sys/auxv.h>
      38             : #endif
      39             : 
      40             : #if defined(ENABLE_PTHREAD_SUPPORT) && defined(HAVE_PTHREAD_H)
      41             : #include <pthread.h>
      42             : #endif
      43             : 
      44             : #include <errno.h>
      45             : 
      46             : #include "roken.h"
      47             : #include "getauxval.h"
      48             : 
      49             : int rk_injected_auxv = 0; /* shared with issuid() for testing */
      50             : static int has_proc_auxv = 1;
      51             : static int proc_auxv_ret = 0;
      52             : 
      53             : #if defined(ENABLE_PTHREAD_SUPPORT) && defined(HAVE_PTHREAD_H)
      54             : pthread_once_t readprocauxv_once = PTHREAD_ONCE_INIT;
      55             : #endif
      56             : 
      57             : /*
      58             :  * There's no standard maximum.
      59             :  *
      60             :  * At the time of this writing we observe some 20 or so auxv entries.
      61             :  * If eventually that grows much larger then rk_getprocaux*() will see a
      62             :  * truncated auxv.
      63             :  */
      64             : #define MAX_AUXV_COUNT 128
      65             : static auxv_t auxv[MAX_AUXV_COUNT];
      66             : 
      67             : static void
      68           0 : do_readprocauxv(void)
      69             : {
      70           0 :     char *p = (void *)auxv;
      71           0 :     ssize_t bytes = 0;
      72           0 :     size_t sz = sizeof(auxv) - sizeof(auxv[0]); /* leave terminator */
      73           0 :     int save_errno = errno;
      74           0 :     int fd;
      75             : 
      76           0 :     errno = 0;
      77           0 :     memset(auxv, 0, sizeof(auxv)); /* terminates our copy */
      78           0 :     if ((fd = open("/proc/self/auxv", O_RDONLY)) == -1) {
      79           0 :         if (errno == ENOENT)
      80           0 :             has_proc_auxv = 0;
      81           0 :         goto out;
      82             :     }
      83             : 
      84           0 :     do {
      85           0 :         if ((bytes = read(fd, p, sz)) > 0) {
      86           0 :             sz -= bytes;
      87           0 :             p += bytes;
      88             :         }
      89           0 :     } while (sz && ((bytes == -1 && errno == EINTR) || bytes > 0));
      90             : 
      91           0 : out:
      92           0 :     proc_auxv_ret = errno;
      93           0 :     if (fd != -1)
      94           0 :         (void) close(fd);
      95           0 :     if (sz == 0 && bytes > 0)
      96           0 :         warnx("/proc/self/auxv has more entries than expected");
      97           0 :     errno = save_errno;
      98           0 :     return;
      99             : }
     100             : 
     101             : static int
     102           0 : readprocauxv(void)
     103             : {
     104             : #if defined(ENABLE_PTHREAD_SUPPORT) && defined(HAVE_PTHREAD_H)
     105             :     pthread_once(&readprocauxv_once, do_readprocauxv);
     106             : #else
     107           0 :     do_readprocauxv();
     108             : #endif
     109           0 :     return proc_auxv_ret;
     110             : }
     111             : 
     112             : /**
     113             :  * Looks up an auxv entry in /proc/self/auxv.  Preserves errno.
     114             :  *
     115             :  * @return a pointer to an auxv_t if found, else NULL.
     116             :  */
     117             : ROKEN_LIB_FUNCTION const auxv_t * ROKEN_LIB_CALL
     118           0 : rk_getauxv(unsigned long type)
     119             : {
     120           0 :     auxv_t *a;
     121             : 
     122           0 :     if (!has_proc_auxv || type > INT_MAX)
     123           0 :         return NULL;
     124             : 
     125           0 :     if (readprocauxv() != 0)
     126           0 :         return NULL;
     127             : 
     128           0 :     for (a = auxv; a - auxv < MAX_AUXV_COUNT; a++) {
     129           0 :         if ((int)a->a_type == (int)type)
     130           0 :             return a;
     131           0 :         if (a->a_type == 0 && a->a_un.a_val == 0)
     132           0 :             break;
     133             :     }
     134           0 :     return NULL;
     135             : }
     136             : 
     137             : #ifdef HAVE_GETAUXVAL
     138             : static unsigned long
     139           0 : rk_getprocauxval(unsigned long type)
     140             : {
     141           0 :     const auxv_t *a = rk_getauxv(type);
     142             : 
     143           0 :     if (a == NULL) {
     144           0 :         errno = ENOENT;
     145           0 :         return 0;
     146             :     }
     147           0 :     return a->a_un.a_val;
     148             : }
     149             : #endif
     150             : 
     151             : /**
     152             :  * Like the nearly-standard getauxval().  If the auxval is not found
     153             :  * returns zero and always sets errno to ENOENT.  Otherwise if auxval is
     154             :  * found it leaves errno as it was, even if the value is zero.
     155             :  *
     156             :  * @return The value of the ELF auxiliary value for the given type, or
     157             :  * zero and sets errno to ENOENT.
     158             :  */
     159             : ROKEN_LIB_FUNCTION unsigned long ROKEN_LIB_CALL
     160       33408 : rk_getauxval(unsigned long type)
     161             : {
     162             : #ifdef HAVE_GETAUXVAL
     163             : #ifdef GETAUXVAL_SETS_ERRNO
     164       33408 :     if (rk_injected_auxv)
     165           0 :         return rk_getprocauxval(type);
     166       33408 :     return getauxval(type);
     167             : #else
     168             :     unsigned long ret;
     169             :     unsigned long ret2;
     170             :     static int getauxval_sets_errno = -1;
     171             :     const auxv_t *a;
     172             :     int save_errno = errno;
     173             : 
     174             :     if (rk_injected_auxv)
     175             :         return rk_getprocauxval(type);
     176             : 
     177             :     errno = 0;
     178             :     ret = getauxval(type);
     179             :     if (ret != 0 || errno == ENOENT || getauxval_sets_errno == 1) {
     180             :         if (ret != 0)
     181             :             errno = save_errno;
     182             :         else if (getauxval_sets_errno > 0 && errno == 0)
     183             :             errno = save_errno;
     184             :         return ret;
     185             :     }
     186             : 
     187             :     if (getauxval_sets_errno == 0) {
     188             :         errno = save_errno;
     189             :         a = rk_getauxv(type);
     190             :         if (a == NULL) {
     191             :             errno = ENOENT;
     192             :             return 0;
     193             :         }
     194             :         return a->a_un.a_val;
     195             :     }
     196             : 
     197             :     /*
     198             :      * We've called getauxval() and it returned 0, but we don't know if
     199             :      * getauxval() sets errno = ENOENT when entries are not found.
     200             :      *
     201             :      * Attempt to detect whether getauxval() sets errno = ENOENT by
     202             :      * calling it with what should be a bogus type.
     203             :      */
     204             : 
     205             :     errno = 0;
     206             :     ret2 = getauxval(~type);
     207             :     if (ret2 == 0 && errno == ENOENT) {
     208             :         getauxval_sets_errno = 1;
     209             :         errno = save_errno;
     210             :         return ret;
     211             :     }
     212             : 
     213             :     getauxval_sets_errno = 0;
     214             :     errno = save_errno;
     215             :     if ((a = rk_getauxv(type)) == NULL) {
     216             :         errno = ENOENT;
     217             :         return 0;
     218             :     }
     219             :     return a->a_un.a_val;
     220             : #endif
     221             : #else
     222             :     const auxv_t *a;
     223             : 
     224             :     if ((a = rk_getauxv(type)) == NULL) {
     225             :         errno = ENOENT;
     226             :         return 0;
     227             :     }
     228             :     return a->a_un.a_val;
     229             : #endif
     230             : }
     231             : 
     232             : /**
     233             :  * *Internal* function for testing by injecting or overwriting an ELF
     234             :  * auxiliary vector entry.
     235             :  *
     236             :  * @return zero on success or ENOSPC if there are too many ELF auxiliary
     237             :  * entries.
     238             :  */
     239             : ROKEN_LIB_FUNCTION int ROKEN_LIB_CALL
     240           0 : rk_injectauxv(auxv_t *e)
     241             : {
     242           0 :     size_t i;
     243           0 :     int ret;
     244             : 
     245             :     /*
     246             :      * This function is racy, but as an internal function never meant to
     247             :      * be called in a threaded program, we don't care.
     248             :      */
     249             : 
     250           0 :     if ((ret = readprocauxv()) != 0)
     251           0 :         return ret;
     252             : 
     253           0 :     rk_injected_auxv = 1;
     254           0 :     for (i = 0; i < MAX_AUXV_COUNT - 1 && auxv[i].a_type != 0; i++) {
     255             :         /* e->a_type == 0 -> truncate auxv, delete all entries */
     256           0 :         if (auxv[i].a_type == e->a_type || e->a_type == 0)
     257             :             break;
     258             :     }
     259           0 :     if (i == MAX_AUXV_COUNT - 1)
     260           0 :         return ENOSPC;
     261           0 :     auxv[i] = e[0];
     262           0 :     return 0;
     263             : }