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v 1.8.8

    1: /*
    2:  * Copyright (c) 2009-2013 Todd C. Miller <Todd.Miller@courtesan.com>
    3:  *
    4:  * Permission to use, copy, modify, and distribute this software for any
    5:  * purpose with or without fee is hereby granted, provided that the above
    6:  * copyright notice and this permission notice appear in all copies.
    7:  *
    8:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    9:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   10:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   11:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   12:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   13:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   14:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   15:  */
   16: 
   17: #include <config.h>
   18: 
   19: #include <sys/types.h>
   20: #include <stdio.h>
   21: #ifdef STDC_HEADERS
   22: # include <stdlib.h>
   23: # include <stddef.h>
   24: #else
   25: # ifdef HAVE_STDLIB_H
   26: #  include <stdlib.h>
   27: # endif
   28: #endif /* STDC_HEADERS */
   29: #ifdef HAVE_STRING_H
   30: # include <string.h>
   31: #endif /* HAVE_STRING_H */
   32: #ifdef HAVE_STRINGS_H
   33: # include <strings.h>
   34: #endif /* HAVE_STRINGS_H */
   35: #ifdef HAVE_UNISTD_H
   36: # include <unistd.h>
   37: #endif /* HAVE_UNISTD_H */
   38: #ifdef HAVE_PRIV_SET
   39: # include <priv.h>
   40: #endif
   41: #include <errno.h>
   42: #include <fcntl.h>
   43: #include <signal.h>
   44: 
   45: #include "sudo.h"
   46: #include "sudo_exec.h"
   47: 
   48: /*
   49:  * Disable execution of child processes in the command we are about
   50:  * to run.  On systems with privilege sets, we can remove the exec
   51:  * privilege.  On other systems we use LD_PRELOAD and the like.
   52:  */
   53: static char * const *
   54: disable_execute(char *const envp[])
   55: {
   56: #ifdef _PATH_SUDO_NOEXEC
   57:     char *preload, **nenvp = NULL;
   58:     int env_len, env_size;
   59:     int preload_idx = -1;
   60: # ifdef RTLD_PRELOAD_ENABLE_VAR
   61:     bool enabled = false;
   62: # endif
   63: #endif /* _PATH_SUDO_NOEXEC */
   64:     debug_decl(disable_execute, SUDO_DEBUG_UTIL)
   65: 
   66: #ifdef HAVE_PRIV_SET
   67:     /* Solaris privileges, remove PRIV_PROC_EXEC post-execve. */
   68:     if (priv_set(PRIV_OFF, PRIV_LIMIT, "PRIV_PROC_EXEC", NULL) == 0)
   69: 	debug_return_ptr(envp);
   70:     warning(_("unable to remove PRIV_PROC_EXEC from PRIV_LIMIT"));
   71: #endif /* HAVE_PRIV_SET */
   72: 
   73: #ifdef _PATH_SUDO_NOEXEC
   74:     /*
   75:      * Preload a noexec file.  For a list of LD_PRELOAD-alikes, see
   76:      * http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html
   77:      * XXX - need to support 32-bit and 64-bit variants
   78:      */
   79: 
   80:     /* Count entries in envp, looking for LD_PRELOAD as we go. */
   81:     for (env_len = 0; envp[env_len] != NULL; env_len++) {
   82: 	if (strncmp(envp[env_len], RTLD_PRELOAD_VAR "=", sizeof(RTLD_PRELOAD_VAR)) == 0) {
   83: 	    preload_idx = env_len;
   84: 	    continue;
   85: 	}
   86: #ifdef RTLD_PRELOAD_ENABLE_VAR
   87: 	if (strncmp(envp[env_len], RTLD_PRELOAD_ENABLE_VAR "=", sizeof(RTLD_PRELOAD_ENABLE_VAR)) == 0) {
   88: 	    enabled = true;
   89: 	    continue;
   90: 	}
   91: #endif
   92:     }
   93: 
   94:     /* Make a new copy of envp as needed. */
   95:     env_size = env_len + 1 + (preload_idx == -1);
   96: #ifdef RTLD_PRELOAD_ENABLE_VAR
   97:     if (!enabled)
   98: 	env_size++;
   99: #endif
  100:     nenvp = emalloc2(env_size, sizeof(*envp));
  101:     memcpy(nenvp, envp, env_len * sizeof(*envp));
  102:     nenvp[env_len] = NULL;
  103: 
  104:     /* Prepend our LD_PRELOAD to existing value or add new entry at the end. */
  105:     if (preload_idx == -1) {
  106: # ifdef RTLD_PRELOAD_DEFAULT
  107: 	easprintf(&preload, "%s=%s%s%s", RTLD_PRELOAD_VAR, sudo_conf_noexec_path(), RTLD_PRELOAD_DELIM, RTLD_PRELOAD_DEFAULT);
  108: # else
  109: 	preload = fmt_string(RTLD_PRELOAD_VAR, sudo_conf_noexec_path());
  110: # endif
  111: 	if (preload == NULL)
  112: 	    fatal(NULL);
  113: 	nenvp[env_len++] = preload;
  114: 	nenvp[env_len] = NULL;
  115:     } else {
  116: 	easprintf(&preload, "%s=%s%s%s", RTLD_PRELOAD_VAR, sudo_conf_noexec_path(), RTLD_PRELOAD_DELIM, nenvp[preload_idx]);
  117: 	nenvp[preload_idx] = preload;
  118:     }
  119: # ifdef RTLD_PRELOAD_ENABLE_VAR
  120:     if (!enabled) {
  121: 	nenvp[env_len++] = RTLD_PRELOAD_ENABLE_VAR "=";
  122: 	nenvp[env_len] = NULL;
  123:     }
  124: # endif
  125: 
  126:     /* Install new env pointer. */
  127:     envp = nenvp;
  128: #endif /* _PATH_SUDO_NOEXEC */
  129: 
  130:     debug_return_ptr(envp);
  131: }
  132: 
  133: /*
  134:  * Like execve(2) but falls back to running through /bin/sh
  135:  * ala execvp(3) if we get ENOEXEC.
  136:  */
  137: int
  138: sudo_execve(const char *path, char *const argv[], char *const envp[], int noexec)
  139: {
  140:     /* Modify the environment as needed to disable further execve(). */
  141:     if (noexec)
  142: 	envp = disable_execute(envp);
  143: 
  144:     execve(path, argv, envp);
  145:     if (errno == ENOEXEC) {
  146: 	int argc;
  147: 	char **nargv;
  148: 
  149: 	for (argc = 0; argv[argc] != NULL; argc++)
  150: 	    continue;
  151: 	nargv = emalloc2(argc + 2, sizeof(char *));
  152: 	nargv[0] = "sh";
  153: 	nargv[1] = (char *)path;
  154: 	memcpy(nargv + 2, argv + 1, argc * sizeof(char *));
  155: 	execve(_PATH_BSHELL, nargv, envp);
  156: 	efree(nargv);
  157:     }
  158:     return -1;
  159: }