1 files changed, 251 insertions, 0 deletions
diff --git a/src/sudo_noexec.c b/src/sudo_noexec.c
new file mode 100644
index 0000000..71a36d6
--- /dev/null
+++ b/src/sudo_noexec.c
@@ -0,0 +1,251 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2004-2005, 2010-2018 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>
+
+#if defined(HAVE_DECL_SECCOMP_MODE_FILTER) && HAVE_DECL_SECCOMP_MODE_FILTER
+# include <sys/prctl.h>
+# include <asm/unistd.h>
+# include <linux/filter.h>
+# include <linux/seccomp.h>
+#endif
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#ifdef HAVE_SPAWN_H
+#include <spawn.h>
+#endif
+#include <string.h>
+#ifdef HAVE_WORDEXP_H
+#include <wordexp.h>
+#endif
+#if defined(HAVE_SHL_LOAD)
+# include <dl.h>
+#elif defined(HAVE_DLOPEN)
+# include <dlfcn.h>
+#endif
+
+#include "sudo_compat.h"
+#include "pathnames.h"
+
+#ifdef HAVE___INTERPOSE
+/*
+ * Mac OS X 10.4 and above has support for library symbol interposition.
+ * There is a good explanation of this in the Mac OS X Internals book.
+ */
+typedef struct interpose_s {
+    void *new_func;
+    void *orig_func;
+} interpose_t;
+
+# define FN_NAME(fn)	fake_ ## fn
+# define INTERPOSE(fn) \
+    __attribute__((__used__)) static const interpose_t interpose_ ## fn \
+    __attribute__((__section__("__DATA,__interpose"))) = \
+	{ (void *)fake_ ## fn, (void *)fn };
+#else
+# define FN_NAME(fn)	fn
+# define INTERPOSE(fn)
+#endif
+
+/*
+ * Replacements for the exec(3) family of syscalls.  It is not enough to
+ * just replace execve(2) since many C libraries do not call the public
+ * execve(2) interface.  Note that it is still possible to access the real
+ * syscalls via the syscall(2) interface, but that is rarely done.
+ */
+
+#define EXEC_REPL_BODY				\
+{						\
+    errno = EACCES;				\
+    return -1;					\
+}
+
+#define EXEC_REPL1(fn, t1)			\
+sudo_dso_public int FN_NAME(fn)(t1 a1);		\
+int FN_NAME(fn)(t1 a1)				\
+EXEC_REPL_BODY					\
+INTERPOSE(fn)
+
+#define EXEC_REPL2(fn, t1, t2)			\
+sudo_dso_public int FN_NAME(fn)(t1 a1, t2 a2);	\
+int FN_NAME(fn)(t1 a1, t2 a2)			\
+EXEC_REPL_BODY					\
+INTERPOSE(fn)
+
+#define EXEC_REPL3(fn, t1, t2, t3)		\
+sudo_dso_public int FN_NAME(fn)(t1 a1, t2 a2, t3 a3); \
+int FN_NAME(fn)(t1 a1, t2 a2, t3 a3)		\
+EXEC_REPL_BODY					\
+INTERPOSE(fn)
+
+#define EXEC_REPL6(fn, t1, t2, t3, t4, t5, t6)	\
+sudo_dso_public int FN_NAME(fn)(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5, t6 a6); \
+int FN_NAME(fn)(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5, t6 a6) \
+EXEC_REPL_BODY					\
+INTERPOSE(fn)
+
+#define EXEC_REPL_VA(fn, t1, t2)		\
+sudo_dso_public int FN_NAME(fn)(t1 a1, t2 a2, ...); \
+int FN_NAME(fn)(t1 a1, t2 a2, ...)		\
+EXEC_REPL_BODY					\
+INTERPOSE(fn)
+
+/*
+ * Standard exec(3) family of functions.
+ */
+EXEC_REPL_VA(execl, const char *, const char *)
+EXEC_REPL_VA(execle, const char *, const char *)
+EXEC_REPL_VA(execlp, const char *, const char *)
+EXEC_REPL2(execv, const char *, char * const *)
+EXEC_REPL2(execvp, const char *, char * const *)
+EXEC_REPL3(execve, const char *, char * const *, char * const *)
+
+/*
+ * Non-standard exec(3) functions and corresponding private versions.
+ */
+#ifdef HAVE_EXECVP
+EXEC_REPL3(execvP, const char *, const char *, char * const *)
+#endif
+#ifdef HAVE_EXECVPE
+EXEC_REPL3(execvpe, const char *, char * const *, char * const *)
+#endif
+#ifdef HAVE_EXECT
+EXEC_REPL3(exect, const char *, char * const *, char * const *)
+#endif
+
+/*
+ * Not all systems support fexecve(2), posix_spawn(2) and posix_spawnp(2).
+ */
+#ifdef HAVE_FEXECVE
+EXEC_REPL3(fexecve, int , char * const *, char * const *)
+#endif
+#ifdef HAVE_POSIX_SPAWN
+EXEC_REPL6(posix_spawn, pid_t *, const char *, const posix_spawn_file_actions_t *, const posix_spawnattr_t *, char * const *, char * const *)
+#endif
+#ifdef HAVE_POSIX_SPAWNP
+EXEC_REPL6(posix_spawnp, pid_t *, const char *, const posix_spawn_file_actions_t *, const posix_spawnattr_t *, char * const *, char * const *)
+#endif
+
+/*
+ * system(3) and popen(3).
+ * We can't use a wrapper for popen since it returns FILE *, not int.
+ */
+EXEC_REPL1(system, const char *)
+
+sudo_dso_public FILE *FN_NAME(popen)(const char *c, const char *t);
+FILE *FN_NAME(popen)(const char *c, const char *t)
+{
+    errno = EACCES;
+    return NULL;
+}
+INTERPOSE(popen)
+
+#if defined(HAVE_WORDEXP) && (defined(RTLD_NEXT) || defined(HAVE_SHL_LOAD) || defined(HAVE___INTERPOSE))
+/*
+ * We can't use a wrapper for wordexp(3) since we still want to call
+ * the real wordexp(3) but with WRDE_NOCMD added to the flags argument.
+ */
+typedef int (*sudo_fn_wordexp_t)(const char *, wordexp_t *, int);
+
+sudo_dso_public int FN_NAME(wordexp)(const char *words, wordexp_t *we, int flags);
+int FN_NAME(wordexp)(const char *words, wordexp_t *we, int flags)
+{
+#if defined(HAVE___INTERPOSE)
+    return wordexp(words, we, flags | WRDE_NOCMD);
+#else
+# if defined(HAVE_DLOPEN)
+    void *fn = dlsym(RTLD_NEXT, "wordexp");
+# elif defined(HAVE_SHL_LOAD)
+    const char *name, *myname = _PATH_SUDO_NOEXEC;
+    struct shl_descriptor *desc;
+    void *fn = NULL;
+    int idx = 0;
+
+    /* Search for wordexp() but skip this shared object. */
+    myname = sudo_basename(myname);
+    while (shl_get(idx++, &desc) == 0) {
+	name = sudo_basename(desc->filename);
+	if (strcmp(name, myname) == 0)
+	    continue;
+	if (shl_findsym(&desc->handle, "wordexp", TYPE_PROCEDURE, &fn) == 0)
+	    break;
+    }
+# else
+    void *fn = NULL;
+# endif
+    if (fn == NULL) {
+	errno = EACCES;
+	return -1;
+    }
+    return ((sudo_fn_wordexp_t)fn)(words, we, flags | WRDE_NOCMD);
+#endif /* HAVE___INTERPOSE */
+}
+INTERPOSE(wordexp)
+#endif /* HAVE_WORDEXP && (RTLD_NEXT || HAVE_SHL_LOAD || HAVE___INTERPOSE) */
+
+/*
+ * On Linux we can use a seccomp() filter to disable exec.
+ */
+#if defined(HAVE_DECL_SECCOMP_MODE_FILTER) && HAVE_DECL_SECCOMP_MODE_FILTER
+
+/* Older systems may not support execveat(2). */
+#ifndef __NR_execveat
+# define __NR_execveat -1
+#endif
+
+static void noexec_ctor(void) __attribute__((constructor));
+
+static void
+noexec_ctor(void)
+{
+    struct sock_filter exec_filter[] = {
+	/* Load syscall number into the accumulator */
+	BPF_STMT(BPF_LD | BPF_ABS, offsetof(struct seccomp_data, nr)),
+	/* Jump to deny for execve/execveat */
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execve, 2, 0),
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execveat, 1, 0),
+	/* Allow non-matching syscalls */
+	BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
+	/* Deny execve/execveat syscall */
+	BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | (EACCES & SECCOMP_RET_DATA))
+    };
+    const struct sock_fprog exec_fprog = {
+	nitems(exec_filter),
+	exec_filter
+    };
+
+    /*
+     * SECCOMP_MODE_FILTER will fail unless the process has
+     * CAP_SYS_ADMIN or the no_new_privs bit is set.
+     */
+    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == 0)
+	(void)prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &exec_fprog);
+}
+#endif /* HAVE_DECL_SECCOMP_MODE_FILTER */