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-rw-r--r--src/sudo_noexec.c261
1 files changed, 261 insertions, 0 deletions
diff --git a/src/sudo_noexec.c b/src/sudo_noexec.c
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+++ b/src/sudo_noexec.c
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+/*
+ * 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_SET_MODE_FILTER) && HAVE_DECL_SECCOMP_SET_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
+#ifdef HAVE_STRING_H
+# include <string.h>
+#endif /* HAVE_STRING_H */
+#ifdef HAVE_STRINGS_H
+# include <strings.h>
+#endif /* HAVE_STRINGS_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) dummy_ ## fn
+# define INTERPOSE(fn) \
+ __attribute__((__used__)) static const interpose_t interpose_ ## fn \
+ __attribute__((__section__("__DATA,__interpose"))) = \
+ { (void *)dummy_ ## fn, (void *)fn };
+#else
+# define FN_NAME(fn) fn
+# define INTERPOSE(fn)
+#endif
+
+/*
+ * Dummy versions of the exec(3) family of syscalls. It is not enough to
+ * just dummy out 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 DUMMY_BODY \
+{ \
+ errno = EACCES; \
+ return -1; \
+}
+
+#define DUMMY1(fn, t1) \
+__dso_public int \
+FN_NAME(fn)(t1 a1) \
+DUMMY_BODY \
+INTERPOSE(fn)
+
+#define DUMMY2(fn, t1, t2) \
+__dso_public int \
+FN_NAME(fn)(t1 a1, t2 a2) \
+DUMMY_BODY \
+INTERPOSE(fn)
+
+#define DUMMY3(fn, t1, t2, t3) \
+__dso_public int \
+FN_NAME(fn)(t1 a1, t2 a2, t3 a3) \
+DUMMY_BODY \
+INTERPOSE(fn)
+
+#define DUMMY6(fn, t1, t2, t3, t4, t5, t6) \
+__dso_public int \
+FN_NAME(fn)(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5, t6 a6) \
+DUMMY_BODY \
+INTERPOSE(fn)
+
+#define DUMMY_VA(fn, t1, t2) \
+__dso_public int \
+FN_NAME(fn)(t1 a1, t2 a2, ...) \
+DUMMY_BODY \
+INTERPOSE(fn)
+
+/*
+ * Standard exec(3) family of functions.
+ */
+DUMMY_VA(execl, const char *, const char *)
+DUMMY_VA(execle, const char *, const char *)
+DUMMY_VA(execlp, const char *, const char *)
+DUMMY2(execv, const char *, char * const *)
+DUMMY2(execvp, const char *, char * const *)
+DUMMY3(execve, const char *, char * const *, char * const *)
+
+/*
+ * Non-standard exec(3) functions and corresponding private versions.
+ */
+#ifdef HAVE_EXECVP
+DUMMY3(execvP, const char *, const char *, char * const *)
+#endif
+#ifdef HAVE_EXECVPE
+DUMMY3(execvpe, const char *, char * const *, char * const *)
+#endif
+#ifdef HAVE_EXECT
+DUMMY3(exect, const char *, char * const *, char * const *)
+#endif
+
+/*
+ * Not all systems support fexecve(2), posix_spawn(2) and posix_spawnp(2).
+ */
+#ifdef HAVE_FEXECVE
+DUMMY3(fexecve, int , char * const *, char * const *)
+#endif
+#ifdef HAVE_POSIX_SPAWN
+DUMMY6(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
+DUMMY6(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.
+ */
+DUMMY1(system, const char *)
+
+__dso_public 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);
+
+__dso_public 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;
+
+ name = strrchr(myname, '/');
+ if (name != NULL)
+ myname = name + 1;
+
+ /* Search for wordexp() but skip this shared object. */
+ while (shl_get(idx++, &desc) == 0) {
+ name = strrchr(desc->filename, '/');
+ if (name == NULL)
+ name = desc->filename;
+ else
+ name++;
+ 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_SET_MODE_FILTER) && HAVE_DECL_SECCOMP_SET_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_SET_MODE_FILTER */