Test *at(2) calls with capability-mode lookup.

This commit adds regression testing for openat(), fstatat(), etc. with
capability scoping ("strict relative" lookup), which applies:
 - in capability mode
 - when performing any *at() lookup relative to a capability

These tests will fail until the *at() code is committed; on my local
instance, with the *at() changes, they all pass.

Approved by: re (kib), mentor (rwatson)
Sponsored by: Google Inc

4 files changed, 157 insertions, 3 deletions

diff --git a/tools/regression/security/cap_test/Makefile b/tools/regression/security/cap_test/Makefile
index 49e308e..4bbb548 100644
--- a/tools/regression/security/cap_test/Makefile
+++ b/tools/regression/security/cap_test/Makefile
@@ -5,7 +5,9 @@ SRCS=	cap_test.c \
 	cap_test_capmode.c \
 	cap_test_capabilities.c \
 	cap_test_fcntl.c \
-	cap_test_sysctl.c
+	cap_test_relative.c \
+	cap_test_sysctl.c \
+
 WARNS=	3
 NO_MAN=
 
diff --git a/tools/regression/security/cap_test/cap_test.c b/tools/regression/security/cap_test/cap_test.c
index dfda4d6..c583454 100644
--- a/tools/regression/security/cap_test/cap_test.c
+++ b/tools/regression/security/cap_test/cap_test.c
@@ -49,6 +49,7 @@ struct test all_tests[] = {
 	TEST_INIT(capmode),
 	TEST_INIT(capabilities),
 	TEST_INIT(fcntl),
+	TEST_INIT(relative),
 	TEST_INIT(sysctl),
 };
 int test_count = sizeof(all_tests) / sizeof(struct test);
diff --git a/tools/regression/security/cap_test/cap_test.h b/tools/regression/security/cap_test/cap_test.h
index 1839e01..23435d6 100644
--- a/tools/regression/security/cap_test/cap_test.h
+++ b/tools/regression/security/cap_test/cap_test.h
@@ -148,8 +148,8 @@ int	execute(int id, struct test*);
 
 int	test_capmode(void);
 int	test_capabilities(void);
-int	test_syscalls(void);
-int	test_sysctl(void);
 int	test_fcntl(void);
+int	test_relative(void);
+int	test_sysctl(void);
 
 #endif /* CAP_TEST_H */
diff --git a/tools/regression/security/cap_test/cap_test_relative.c b/tools/regression/security/cap_test/cap_test_relative.c
new file mode 100644
index 0000000..1f62e84
--- /dev/null
+++ b/tools/regression/security/cap_test/cap_test_relative.c
@@ -0,0 +1,151 @@
+/*-
+ * Copyright (c) 2009-2011 Robert N. M. Watson
+ * Copyright (c) 2011 Jonathan Anderson
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/capability.h>
+#include <sys/errno.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "cap_test.h"
+
+/*
+ * Test openat(2) in a variety of sitations to ensure that it obeys Capsicum
+ * "strict relative" rules:
+ *
+ * 1. Use strict relative lookups in capability mode or when operating
+ *    relative to a capability.
+ * 2. When performing strict relative lookups, absolute paths (including
+ *    symlinks to absolute paths) are not allowed, nor are paths containing
+ *    '..' components.
+ */
+int
+test_relative(void)
+{
+	int success = PASSED;
+	int fd, etc, etc_cap, etc_cap_ro, etc_cap_base, etc_cap_all;
+	cap_rights_t baserights = CAP_READ | CAP_WRITE | CAP_SEEK | CAP_LOOKUP;
+	cap_rights_t rights;
+
+	REQUIRE(etc = open("/etc/", O_RDONLY));
+	CHECK_SYSCALL_FAILS(EINVAL, cap_getrights, etc, &rights);
+
+	MAKE_CAPABILITY(etc_cap, etc, CAP_READ);
+	MAKE_CAPABILITY(etc_cap_ro, etc, CAP_READ | CAP_LOOKUP);
+	MAKE_CAPABILITY(etc_cap_base, etc, baserights);
+	MAKE_CAPABILITY(etc_cap_all, etc, CAP_MASK_VALID);
+
+	/*
+	 * openat(2) with regular file descriptors in non-capability mode
+	 * should Just Work (tm).
+	 */
+	CHECK_SYSCALL_SUCCEEDS(openat, etc, "/etc/passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, AT_FDCWD, "/etc/passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc, "passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc, "../etc/passwd", O_RDONLY);
+
+	/*
+	 * Lookups relative to capabilities should be strictly relative.
+	 *
+	 * When not in capability mode, we don't actually require CAP_LOOKUP.
+	 */
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_ro, "passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_base, "passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_all, "passwd", O_RDONLY);
+
+	CHECK_NOTCAPABLE(openat, etc_cap_ro, "../etc/passwd", O_RDONLY);
+	CHECK_NOTCAPABLE(openat, etc_cap_base, "../etc/passwd", O_RDONLY);
+
+	/*
+	 * This requires discussion: do we treat a capability with
+	 * CAP_MASK_VALID *exactly* like a non-capability file descriptor
+	 * (currently, the implementation says yes)?
+	 */
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_all, "../etc/passwd", O_RDONLY);
+
+	/*
+	 * A file opened relative to a capability should itself be a capability.
+	 */
+	CHECK_SYSCALL_SUCCEEDS(cap_getrights, etc_cap_base, &rights);
+
+	REQUIRE(fd = openat(etc_cap_base, "passwd", O_RDONLY));
+	CHECK_SYSCALL_SUCCEEDS(cap_getrights, fd, &rights);
+	CHECK_RIGHTS(rights, baserights);
+
+	/*
+	 * Enter capability mode; now ALL lookups are strictly relative.
+	 */
+	REQUIRE(cap_enter());
+
+	/*
+	 * Relative lookups on regular files or capabilities with CAP_LOOKUP
+	 * ought to succeed.
+	 */
+	CHECK_SYSCALL_SUCCEEDS(openat, etc, "passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_ro, "passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_base, "passwd", O_RDONLY);
+	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_all, "passwd", O_RDONLY);
+
+	/*
+	 * Lookup relative to capabilities without CAP_LOOKUP should fail.
+	 */
+	CHECK_NOTCAPABLE(openat, etc_cap, "passwd", O_RDONLY);
+
+	/*
+	 * Absolute lookups should fail.
+	 */
+	CHECK_CAPMODE(openat, AT_FDCWD, "/etc/passwd", O_RDONLY);
+	CHECK_NOTCAPABLE(openat, etc, "/etc/passwd", O_RDONLY);
+
+	/*
+	 * Lookups containing '..' should fail in capability mode.
+	 */
+	CHECK_NOTCAPABLE(openat, etc, "../etc/passwd", O_RDONLY);
+	CHECK_NOTCAPABLE(openat, etc_cap_ro, "../etc/passwd", O_RDONLY);
+	CHECK_NOTCAPABLE(openat, etc_cap_base, "../etc/passwd", O_RDONLY);
+
+	REQUIRE(fd = openat(etc, "passwd", O_RDONLY));
+	CHECK_SYSCALL_SUCCEEDS(cap_getrights, fd, &rights);
+
+	/*
+	 * A file opened relative to a capability should itself be a capability.
+	 */
+	REQUIRE(fd = openat(etc_cap_base, "passwd", O_RDONLY));
+	CHECK_SYSCALL_SUCCEEDS(cap_getrights, fd, &rights);
+	CHECK_RIGHTS(rights, baserights);
+
+	return success;
+}