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sudo 1.8.5p1

    1: /*
    2:  * Copyright (c) 2009-2012 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 <sys/param.h>
   21: #include <stdio.h>
   22: #ifdef STDC_HEADERS
   23: # include <stdlib.h>
   24: # include <stddef.h>
   25: #else
   26: # ifdef HAVE_STDLIB_H
   27: #  include <stdlib.h>
   28: # endif
   29: #endif /* STDC_HEADERS */
   30: #ifdef HAVE_STRING_H
   31: # include <string.h>
   32: #endif /* HAVE_STRING_H */
   33: #ifdef HAVE_STRINGS_H
   34: # include <strings.h>
   35: #endif /* HAVE_STRINGS_H */
   36: #ifdef HAVE_UNISTD_H
   37: # include <unistd.h>
   38: #endif /* HAVE_UNISTD_H */
   39: #ifdef HAVE_PRIV_SET
   40: # include <priv.h>
   41: #endif
   42: #include <errno.h>
   43: 
   44: #include "sudo.h"
   45: #include "sudo_exec.h"
   46: 
   47: /*
   48:  * Disable execution of child processes in the command we are about
   49:  * to run.  On systems with privilege sets, we can remove the exec
   50:  * privilege.  On other systems we use LD_PRELOAD and the like.
   51:  */
   52: static char * const *
   53: disable_execute(char *const envp[])
   54: {
   55: #ifdef _PATH_SUDO_NOEXEC
   56:     char *preload, **nenvp = NULL;
   57:     int env_len, env_size;
   58:     int preload_idx = -1;
   59: # ifdef RTLD_PRELOAD_ENABLE_VAR
   60:     bool enabled = false;
   61: # endif
   62: #endif /* _PATH_SUDO_NOEXEC */
   63:     debug_decl(disable_execute, SUDO_DEBUG_UTIL)
   64: 
   65: #ifdef HAVE_PRIV_SET
   66:     /* Solaris privileges, remove PRIV_PROC_EXEC post-execve. */
   67:     if (priv_set(PRIV_OFF, PRIV_LIMIT, "PRIV_PROC_EXEC", NULL) == 0)
   68: 	debug_return_ptr(envp);
   69:     warning(_("unable to remove PRIV_PROC_EXEC from PRIV_LIMIT"));
   70: #endif /* HAVE_PRIV_SET */
   71: 
   72: #ifdef _PATH_SUDO_NOEXEC
   73:     /*
   74:      * Preload a noexec file.  For a list of LD_PRELOAD-alikes, see
   75:      * http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html
   76:      * XXX - need to support 32-bit and 64-bit variants
   77:      */
   78: 
   79:     /* Count entries in envp, looking for LD_PRELOAD as we go. */
   80:     for (env_len = 0; envp[env_len] != NULL; env_len++) {
   81: 	if (strncmp(envp[env_len], RTLD_PRELOAD_VAR "=", sizeof(RTLD_PRELOAD_VAR)) == 0) {
   82: 	    preload_idx = env_len;
   83: 	    continue;
   84: 	}
   85: #ifdef RTLD_PRELOAD_ENABLE_VAR
   86: 	if (strncmp(envp[env_len], RTLD_PRELOAD_ENABLE_VAR "=", sizeof(RTLD_PRELOAD_ENABLE_VAR)) == 0) {
   87: 	    enabled = true;
   88: 	    continue;
   89: 	}
   90: #endif
   91:     }
   92: 
   93:     /* Make a new copy of envp as needed. */
   94:     env_size = env_len + 1 + (preload_idx == -1);
   95: #ifdef RTLD_PRELOAD_ENABLE_VAR
   96:     if (!enabled)
   97: 	env_size++;
   98: #endif
   99:     nenvp = emalloc2(env_size, sizeof(*envp));
  100:     memcpy(nenvp, envp, env_len * sizeof(*envp));
  101:     nenvp[env_len] = NULL;
  102: 
  103:     /* Prepend our LD_PRELOAD to existing value or add new entry at the end. */
  104:     if (preload_idx == -1) {
  105: # ifdef RTLD_PRELOAD_DEFAULT
  106: 	easprintf(&preload, "%s=%s%s%s", RTLD_PRELOAD_VAR, sudo_conf_noexec_path(), RTLD_PRELOAD_DELIM, RTLD_PRELOAD_DEFAULT);
  107: # else
  108: 	preload = fmt_string(RTLD_PRELOAD_VAR, sudo_conf_noexec_path());
  109: # endif
  110: 	if (preload == NULL)
  111: 	    errorx(1, _("unable to allocate memory"));
  112: 	nenvp[env_len++] = preload;
  113: 	nenvp[env_len] = NULL;
  114:     } else {
  115: 	easprintf(&preload, "%s=%s%s%s", RTLD_PRELOAD_VAR, sudo_conf_noexec_path(), RTLD_PRELOAD_DELIM, nenvp[preload_idx]);
  116: 	nenvp[preload_idx] = preload;
  117:     }
  118: # ifdef RTLD_PRELOAD_ENABLE_VAR
  119:     if (!enabled) {
  120: 	nenvp[env_len++] = RTLD_PRELOAD_ENABLE_VAR "=";
  121: 	nenvp[env_len] = NULL;
  122:     }
  123: # endif
  124: 
  125:     /* Install new env pointer. */
  126:     envp = nenvp;
  127: #endif /* _PATH_SUDO_NOEXEC */
  128: 
  129:     debug_return_ptr(envp);
  130: }
  131: 
  132: /*
  133:  * Like execve(2) but falls back to running through /bin/sh
  134:  * ala execvp(3) if we get ENOEXEC.
  135:  */
  136: int
  137: sudo_execve(const char *path, char *const argv[], char *const envp[], int noexec)
  138: {
  139:     /* Modify the environment as needed to disable further execve(). */
  140:     if (noexec)
  141: 	envp = disable_execute(envp);
  142: 
  143:     execve(path, argv, envp);
  144:     if (errno == ENOEXEC) {
  145: 	int argc;
  146: 	char **nargv;
  147: 
  148: 	for (argc = 0; argv[argc] != NULL; argc++)
  149: 	    continue;
  150: 	nargv = emalloc2(argc + 2, sizeof(char *));
  151: 	nargv[0] = "sh";
  152: 	nargv[1] = (char *)path;
  153: 	memcpy(nargv + 2, argv + 1, argc * sizeof(char *));
  154: 	execve(_PATH_BSHELL, nargv, envp);
  155: 	efree(nargv);
  156:     }
  157:     return -1;
  158: }