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/*
* Copyright (c) 2009-2016 Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
#include <config.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_STRING_H
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#include <unistd.h>
#ifdef HAVE_PRIV_SET
# include <priv.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include "sudo.h"
#include "sudo_exec.h"
#ifdef RTLD_PRELOAD_VAR
/*
* Add a DSO file to LD_PRELOAD or the system equivalent.
*/
static char **
preload_dso(char *envp[], const char *dso_file)
{
char *preload = NULL;
int env_len;
int preload_idx = -1;
bool present = false;
# ifdef RTLD_PRELOAD_ENABLE_VAR
bool enabled = false;
# else
const bool enabled = true;
# endif
debug_decl(preload_dso, SUDO_DEBUG_UTIL)
/*
* Preload a DSO file. For a list of LD_PRELOAD-alikes, see
* http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html
* XXX - need to support 32-bit and 64-bit variants
*/
/* Count entries in envp, looking for LD_PRELOAD as we go. */
for (env_len = 0; envp[env_len] != NULL; env_len++) {
if (preload_idx == -1 && strncmp(envp[env_len], RTLD_PRELOAD_VAR "=",
sizeof(RTLD_PRELOAD_VAR)) == 0) {
const char *cp = envp[env_len] + sizeof(RTLD_PRELOAD_VAR);
const char *end = cp + strlen(cp);
const char *ep;
const size_t dso_len = strlen(dso_file);
/* Check to see if dso_file is already present. */
for (cp = sudo_strsplit(cp, end, RTLD_PRELOAD_DELIM, &ep);
cp != NULL; cp = sudo_strsplit(NULL, end, RTLD_PRELOAD_DELIM,
&ep)) {
if ((size_t)(ep - cp) == dso_len) {
if (memcmp(cp, dso_file, dso_len) == 0) {
/* already present */
present = true;
break;
}
}
}
/* Save index of existing LD_PRELOAD variable. */
preload_idx = env_len;
continue;
}
# ifdef RTLD_PRELOAD_ENABLE_VAR
if (strncmp(envp[env_len], RTLD_PRELOAD_ENABLE_VAR "=", sizeof(RTLD_PRELOAD_ENABLE_VAR)) == 0) {
enabled = true;
continue;
}
# endif
}
/*
* Make a new copy of envp as needed.
* It would be nice to realloc the old envp[] but we don't know
* whether it was dynamically allocated. [TODO: plugin API]
*/
if (preload_idx == -1 || !enabled) {
const int env_size = env_len + 1 + (preload_idx == -1) + enabled;
char **nenvp = reallocarray(NULL, env_size, sizeof(*envp));
if (nenvp == NULL)
sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
memcpy(nenvp, envp, env_len * sizeof(*envp));
nenvp[env_len] = NULL;
envp = nenvp;
}
/* Prepend our LD_PRELOAD to existing value or add new entry at the end. */
if (!present) {
if (preload_idx == -1) {
# ifdef RTLD_PRELOAD_DEFAULT
asprintf(&preload, "%s=%s%s%s", RTLD_PRELOAD_VAR, dso_file,
RTLD_PRELOAD_DELIM, RTLD_PRELOAD_DEFAULT);
# else
preload = sudo_new_key_val(RTLD_PRELOAD_VAR, dso_file);
# endif
if (preload == NULL) {
sudo_fatalx(U_("%s: %s"), __func__,
U_("unable to allocate memory"));
}
envp[env_len++] = preload;
envp[env_len] = NULL;
} else {
int len = asprintf(&preload, "%s=%s%s%s", RTLD_PRELOAD_VAR,
dso_file, RTLD_PRELOAD_DELIM, envp[preload_idx]);
if (len == -1) {
sudo_fatalx(U_("%s: %s"), __func__,
U_("unable to allocate memory"));
}
envp[preload_idx] = preload;
}
}
# ifdef RTLD_PRELOAD_ENABLE_VAR
if (!enabled) {
envp[env_len++] = RTLD_PRELOAD_ENABLE_VAR "=";
envp[env_len] = NULL;
}
# endif
debug_return_ptr(envp);
}
#endif /* RTLD_PRELOAD_VAR */
/*
* Disable execution of child processes in the command we are about
* to run. On systems with privilege sets, we can remove the exec
* privilege. On other systems we use LD_PRELOAD and the like.
*/
char **
disable_execute(char *envp[], const char *dso)
{
debug_decl(disable_execute, SUDO_DEBUG_UTIL)
#ifdef HAVE_PRIV_SET
/* Solaris privileges, remove PRIV_PROC_EXEC post-execve. */
(void)priv_set(PRIV_ON, PRIV_INHERITABLE, "PRIV_FILE_DAC_READ", NULL);
(void)priv_set(PRIV_ON, PRIV_INHERITABLE, "PRIV_FILE_DAC_WRITE", NULL);
(void)priv_set(PRIV_ON, PRIV_INHERITABLE, "PRIV_FILE_DAC_SEARCH", NULL);
if (priv_set(PRIV_OFF, PRIV_LIMIT, "PRIV_PROC_EXEC", NULL) == 0)
debug_return_ptr(envp);
sudo_warn(U_("unable to remove PRIV_PROC_EXEC from PRIV_LIMIT"));
#endif /* HAVE_PRIV_SET */
#ifdef RTLD_PRELOAD_VAR
if (dso != NULL)
envp = preload_dso(envp, dso);
#endif /* RTLD_PRELOAD_VAR */
debug_return_ptr(envp);
}
/*
* Like execve(2) but falls back to running through /bin/sh
* ala execvp(3) if we get ENOEXEC.
*/
int
sudo_execve(int fd, const char *path, char *const argv[], char *envp[], bool noexec)
{
debug_decl(sudo_execve, SUDO_DEBUG_UTIL)
sudo_debug_execve(SUDO_DEBUG_INFO, path, argv, envp);
/* Modify the environment as needed to disable further execve(). */
if (noexec)
envp = disable_execute(envp, sudo_conf_noexec_path());
#ifdef HAVE_FEXECVE
if (fd != -1)
fexecve(fd, argv, envp);
else
#endif
execve(path, argv, envp);
if (fd == -1 && errno == ENOEXEC) {
int argc;
char **nargv;
for (argc = 0; argv[argc] != NULL; argc++)
continue;
nargv = reallocarray(NULL, argc + 2, sizeof(char *));
if (nargv != NULL) {
nargv[0] = "sh";
nargv[1] = (char *)path;
memcpy(nargv + 2, argv + 1, argc * sizeof(char *));
execve(_PATH_SUDO_BSHELL, nargv, envp);
free(nargv);
}
}
debug_return_int(-1);
}
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