include: ssp: fortify <stdlib.h>

The immediately obvious and attractive targets from <stdlib.h> are
arc4random_buf(3) and realpath(3) -- scraping the header didn't reveal
much else of interest.

Reviewed by:	markj
Sponsored by:	Klara, Inc.
Sponsored by:	Stormshield
Differential Revision:	https://reviews.freebsd.org/D45681

include/ssp/Makefile

@@ -1,4 +1,4 @@
-INCS=	poll.h ssp.h stdio.h string.h strings.h unistd.h
+INCS=	poll.h ssp.h stdio.h stdlib.h string.h strings.h unistd.h
 INCSDIR=	${INCLUDEDIR}/ssp
 
 .include <bsd.prog.mk>

include/ssp/stdlib.h

@@ -0,0 +1,53 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024, Klara, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef _SSP_STDLIB_H_
+#define _SSP_STDLIB_H_
+
+#include <ssp/ssp.h>
+
+#if __SSP_FORTIFY_LEVEL > 0
+
+#include <limits.h>
+
+__BEGIN_DECLS
+
+__ssp_redirect(void, arc4random_buf, (void *__buf, size_t __len),
+    (__buf, __len));
+
+__ssp_redirect_raw_impl(char *, realpath, realpath,
+    (const char *__restrict path, char *__restrict buf))
+{
+	if (__ssp_bos(buf) < PATH_MAX)
+		__chk_fail();
+
+	return (__ssp_real(realpath)(path, buf));
+}
+
+__END_DECLS
+
+#endif /* __SSP_FORTIFY_LEVEL > 0 */
+#endif /* _SSP_STDLIB_H_ */

include/stdlib.h

@@ -69,6 +69,10 @@ typedef struct {
  */
 #define	RAND_MAX	0x7fffffff
 
+#if !defined(_STANDALONE) && defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0
+#include <ssp/stdlib.h>
+#endif
+
 __BEGIN_DECLS
 #ifdef _XLOCALE_H_
 #include <xlocale/_stdlib.h>

lib/libc/gen/arc4random.c

@@ -35,6 +35,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <ssp/ssp.h>
 #include <sys/types.h>
 #include <sys/time.h>
  
@@ -243,7 +244,7 @@ arc4random(void)
 }
 
 void
-arc4random_buf(void *buf, size_t n)
+__ssp_real(arc4random_buf)(void *buf, size_t n)
 {
 	_ARC4_LOCK();
 	_rs_random_buf(buf, n);

lib/libc/stdlib/realpath.c

@@ -37,6 +37,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <ssp/ssp.h>
 #include "un-namespace.h"
 #include "libc_private.h"
 
@@ -203,7 +204,7 @@ realpath1(const char *path, char *resolved)
 }
 
 char *
-realpath(const char * __restrict path, char * __restrict resolved)
+__ssp_real(realpath)(const char * __restrict path, char * __restrict resolved)
 {
 	char *m, *res;
 

lib/libc/tests/secure/Makefile

@@ -3,6 +3,7 @@
 TESTSDIR:=	${TESTSBASE}/${RELDIR:C/libc\/tests/libc/}
 
 FORTIFY_TCATS+=	poll
+FORTIFY_TCATS+=	stdlib
 FORTIFY_TCATS+=	stdio
 FORTIFY_TCATS+=	string
 FORTIFY_TCATS+=	strings

lib/libc/tests/secure/fortify_stdlib_test.c

@@ -0,0 +1,383 @@
+/* @generated by `generate-fortify-tests.lua "stdlib"` */
+
+#define	_FORTIFY_SOURCE	2
+#define	TMPFILE_SIZE	(1024 * 32)
+
+#include <sys/param.h>
+#include <sys/resource.h>
+#include <sys/time.h>
+#include <sys/wait.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <sysexits.h>
+#include <unistd.h>
+#include <atf-c.h>
+
+static FILE * __unused
+new_fp(size_t __len)
+{
+	static char fpbuf[LINE_MAX];
+	FILE *fp;
+
+	ATF_REQUIRE(__len <= sizeof(fpbuf));
+
+	memset(fpbuf, 'A', sizeof(fpbuf) - 1);
+	fpbuf[sizeof(fpbuf) - 1] = '\0';
+
+	fp = fmemopen(fpbuf, sizeof(fpbuf), "rb");
+	ATF_REQUIRE(fp != NULL);
+
+	return (fp);
+}
+
+/*
+ * Create a new symlink to use for readlink(2) style tests, we'll just use a
+ * random target name to have something interesting to look at.
+ */
+static const char * __unused
+new_symlink(size_t __len)
+{
+	static const char linkname[] = "link";
+	char target[MAXNAMLEN];
+	int error;
+
+	ATF_REQUIRE(__len <= sizeof(target));
+
+	arc4random_buf(target, sizeof(target));
+
+	error = unlink(linkname);
+	ATF_REQUIRE(error == 0 || errno == ENOENT);
+
+	error = symlink(target, linkname);
+	ATF_REQUIRE(error == 0);
+
+	return (linkname);
+}
+
+/*
+ * Constructs a tmpfile that we can use for testing read(2) and friends.
+ */
+static int __unused
+new_tmpfile(void)
+{
+	char buf[1024];
+	ssize_t rv;
+	size_t written;
+	int fd;
+
+	fd = open("tmpfile", O_RDWR | O_CREAT | O_TRUNC, 0644);
+	ATF_REQUIRE(fd >= 0);
+
+	written = 0;
+	while (written < TMPFILE_SIZE) {
+		rv = write(fd, buf, sizeof(buf));
+		ATF_REQUIRE(rv > 0);
+
+		written += rv;
+	}
+
+	ATF_REQUIRE_EQ(0, lseek(fd, 0, SEEK_SET));
+	return (fd);
+}
+
+static void
+disable_coredumps(void)
+{
+	struct rlimit rl = { 0 };
+
+	if (setrlimit(RLIMIT_CORE, &rl) == -1)
+		_exit(EX_OSERR);
+}
+
+/*
+ * Replaces stdin with a file that we can actually read from, for tests where
+ * we want a FILE * or fd that we can get data from.
+ */
+static void __unused
+replace_stdin(void)
+{
+	int fd;
+
+	fd = new_tmpfile();
+
+	(void)dup2(fd, STDIN_FILENO);
+	if (fd != STDIN_FILENO)
+		close(fd);
+}
+
+ATF_TC_WITHOUT_HEAD(arc4random_buf_before_end);
+ATF_TC_BODY(arc4random_buf_before_end, tc)
+{
+#define BUF &__stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char __buf[42];
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(__stack.__buf);
+	const size_t __len = 42 - 1;
+	const size_t __idx __unused = __len - 1;
+
+	arc4random_buf(__stack.__buf, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(arc4random_buf_end);
+ATF_TC_BODY(arc4random_buf_end, tc)
+{
+#define BUF &__stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char __buf[42];
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(__stack.__buf);
+	const size_t __len = 42;
+	const size_t __idx __unused = __len - 1;
+
+	arc4random_buf(__stack.__buf, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(arc4random_buf_heap_before_end);
+ATF_TC_BODY(arc4random_buf_heap_before_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (42);
+	const size_t __len = 42 - 1;
+	const size_t __idx __unused = __len - 1;
+
+	__stack.__buf = malloc(__bufsz);
+
+	arc4random_buf(__stack.__buf, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(arc4random_buf_heap_end);
+ATF_TC_BODY(arc4random_buf_heap_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (42);
+	const size_t __len = 42;
+	const size_t __idx __unused = __len - 1;
+
+	__stack.__buf = malloc(__bufsz);
+
+	arc4random_buf(__stack.__buf, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(arc4random_buf_heap_after_end);
+ATF_TC_BODY(arc4random_buf_heap_after_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (42);
+	const size_t __len = 42 + 1;
+	const size_t __idx __unused = __len - 1;
+	pid_t __child;
+	int __status;
+
+	__child = fork();
+	ATF_REQUIRE(__child >= 0);
+	if (__child > 0)
+		goto monitor;
+
+	/* Child */
+	disable_coredumps();
+	__stack.__buf = malloc(__bufsz);
+
+	arc4random_buf(__stack.__buf, __len);
+	_exit(EX_SOFTWARE);	/* Should have aborted. */
+
+monitor:
+	while (waitpid(__child, &__status, 0) != __child) {
+		ATF_REQUIRE_EQ(EINTR, errno);
+	}
+
+	if (!WIFSIGNALED(__status)) {
+		switch (WEXITSTATUS(__status)) {
+		case EX_SOFTWARE:
+			atf_tc_fail("FORTIFY_SOURCE failed to abort");
+			break;
+		case EX_OSERR:
+			atf_tc_fail("setrlimit(2) failed");
+			break;
+		default:
+			atf_tc_fail("child exited with status %d",
+			    WEXITSTATUS(__status));
+		}
+	} else {
+		ATF_REQUIRE_EQ(SIGABRT, WTERMSIG(__status));
+	}
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(realpath_before_end);
+ATF_TC_BODY(realpath_before_end, tc)
+{
+#define BUF &__stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char __buf[PATH_MAX + 1];
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(__stack.__buf);
+	const size_t __len = PATH_MAX + 1;
+	const size_t __idx __unused = __len - 1;
+
+	realpath(".", __stack.__buf);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(realpath_end);
+ATF_TC_BODY(realpath_end, tc)
+{
+#define BUF &__stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char __buf[PATH_MAX];
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(__stack.__buf);
+	const size_t __len = PATH_MAX;
+	const size_t __idx __unused = __len - 1;
+
+	realpath(".", __stack.__buf);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(realpath_heap_before_end);
+ATF_TC_BODY(realpath_heap_before_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (PATH_MAX + 1);
+	const size_t __len = PATH_MAX + 1;
+	const size_t __idx __unused = __len - 1;
+
+	__stack.__buf = malloc(__bufsz);
+
+	realpath(".", __stack.__buf);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(realpath_heap_end);
+ATF_TC_BODY(realpath_heap_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (PATH_MAX);
+	const size_t __len = PATH_MAX;
+	const size_t __idx __unused = __len - 1;
+
+	__stack.__buf = malloc(__bufsz);
+
+	realpath(".", __stack.__buf);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(realpath_heap_after_end);
+ATF_TC_BODY(realpath_heap_after_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (PATH_MAX - 1);
+	const size_t __len = PATH_MAX - 1;
+	const size_t __idx __unused = __len - 1;
+	pid_t __child;
+	int __status;
+
+	__child = fork();
+	ATF_REQUIRE(__child >= 0);
+	if (__child > 0)
+		goto monitor;
+
+	/* Child */
+	disable_coredumps();
+	__stack.__buf = malloc(__bufsz);
+
+	realpath(".", __stack.__buf);
+	_exit(EX_SOFTWARE);	/* Should have aborted. */
+
+monitor:
+	while (waitpid(__child, &__status, 0) != __child) {
+		ATF_REQUIRE_EQ(EINTR, errno);
+	}
+
+	if (!WIFSIGNALED(__status)) {
+		switch (WEXITSTATUS(__status)) {
+		case EX_SOFTWARE:
+			atf_tc_fail("FORTIFY_SOURCE failed to abort");
+			break;
+		case EX_OSERR:
+			atf_tc_fail("setrlimit(2) failed");
+			break;
+		default:
+			atf_tc_fail("child exited with status %d",
+			    WEXITSTATUS(__status));
+		}
+	} else {
+		ATF_REQUIRE_EQ(SIGABRT, WTERMSIG(__status));
+	}
+#undef BUF
+
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, arc4random_buf_before_end);
+	ATF_TP_ADD_TC(tp, arc4random_buf_end);
+	ATF_TP_ADD_TC(tp, arc4random_buf_heap_before_end);
+	ATF_TP_ADD_TC(tp, arc4random_buf_heap_end);
+	ATF_TP_ADD_TC(tp, arc4random_buf_heap_after_end);
+	ATF_TP_ADD_TC(tp, realpath_before_end);
+	ATF_TP_ADD_TC(tp, realpath_end);
+	ATF_TP_ADD_TC(tp, realpath_heap_before_end);
+	ATF_TP_ADD_TC(tp, realpath_heap_end);
+	ATF_TP_ADD_TC(tp, realpath_heap_after_end);
+	return (atf_no_error());
+}

lib/libc/tests/secure/generate-fortify-tests.lua

@@ -262,6 +262,26 @@ local all_tests = {
 ]],
 		},
 	},
+	stdlib = {
+		-- <stdlib.h>
+		{
+			func = "arc4random_buf",
+			arguments = {
+				"__buf",
+				"__len",
+			},
+			exclude = excludes_stack_overflow,
+		},
+		{
+			func = "realpath",
+			bufsize = "PATH_MAX",
+			arguments = {
+				"\".\"",
+				"__buf",
+			},
+			exclude = excludes_stack_overflow,
+		},
+	},
 	string = {
 		-- <string.h>
 		{