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-rw-r--r--src/exec_common.c219
1 files changed, 219 insertions, 0 deletions
diff --git a/src/exec_common.c b/src/exec_common.c
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+++ b/src/exec_common.c
@@ -0,0 +1,219 @@
+/*
+ * 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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