1 files changed, 136 insertions, 0 deletions
diff --git a/src/exec_common.c b/src/exec_common.c
new file mode 100644
index 0000000..9e2d954
--- /dev/null
+++ b/src/exec_common.c
@@ -0,0 +1,136 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2009-2022 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 <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#ifdef HAVE_PRIV_SET
+# include <priv.h>
+#endif
+#include <errno.h>
+
+#include <sudo.h>
+#include <sudo_exec.h>
+
+/*
+ * 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("%s", U_("unable to remove PRIV_PROC_EXEC from PRIV_LIMIT"));
+#endif /* HAVE_PRIV_SET */
+
+#ifdef RTLD_PRELOAD_VAR
+    if (dso != NULL)
+	envp = sudo_preload_dso(envp, dso, -1);
+#endif /* RTLD_PRELOAD_VAR */
+
+    debug_return_ptr(envp);
+}
+
+/*
+ * Trap execution of child processes in the command we are about to run.
+ * Uses LD_PRELOAD and the like to perform a policy check on child commands.
+ */
+static char **
+enable_intercept(char *envp[], const char *dso, int intercept_fd)
+{
+    debug_decl(enable_intercept, SUDO_DEBUG_UTIL);
+
+    if (dso != NULL) {
+#ifdef RTLD_PRELOAD_VAR
+	if (intercept_fd == -1)
+	    sudo_fatalx("%s: no intercept fd", __func__);
+
+	envp = sudo_preload_dso(envp, dso, intercept_fd);
+#else
+	/* Intercept not supported, envp unchanged. */
+	if (intercept_fd != -1)
+	    close(intercept_fd);
+#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[],
+    int intercept_fd, unsigned int flags)
+{
+    debug_decl(sudo_execve, SUDO_DEBUG_UTIL);
+
+    sudo_debug_execve(SUDO_DEBUG_INFO, path, argv, envp);
+
+    /* Modify the environment as needed to trap execve(). */
+    if (ISSET(flags, CD_NOEXEC))
+	envp = disable_execute(envp, sudo_conf_noexec_path());
+    if (ISSET(flags, CD_INTERCEPT|CD_LOG_SUBCMDS)) {
+	if (!ISSET(flags, CD_USE_PTRACE)) {
+	    envp = enable_intercept(envp, sudo_conf_intercept_path(),
+		intercept_fd);
+	}
+    }
+
+#ifdef HAVE_FEXECVE
+    if (fd != -1)
+	    fexecve(fd, argv, envp);
+    else
+#endif
+	    execve(path, argv, envp);
+    if (fd == -1 && errno == ENOEXEC) {
+	int argc;
+	const char **nargv;
+
+	for (argc = 0; argv[argc] != NULL; argc++)
+	    continue;
+	nargv = reallocarray(NULL, (size_t)argc + 2, sizeof(char *));
+	if (nargv != NULL) {
+	    nargv[0] = "sh";
+	    nargv[1] = path;
+	    memcpy(nargv + 2, argv + 1, (size_t)argc * sizeof(char *));
+	    execve(_PATH_SUDO_BSHELL, (char **)nargv, envp);
+	    free(nargv);
+	}
+    }
+    debug_return_int(-1);
+}