xref: /freebsd/tests/sys/fs/fusefs/allow_other.cc (revision f8d4af104b7da1f8ed939b93552c84bac967cbae)

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2019 The FreeBSD Foundation
 *
 * This software was developed by BFF Storage Systems, LLC under sponsorship
 * from the FreeBSD Foundation.
 *
 * 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.
 */

/*
 * Tests for the "allow_other" mount option.  They must be in their own
 * file so they can be run as root
 */

extern "C" {
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
}

#include "mockfs.hh"
#include "utils.hh"

using namespace testing;

const static char FULLPATH[] = "mountpoint/some_file.txt";
const static char RELPATH[] = "some_file.txt";

class NoAllowOther: public FuseTest {

public:
/* Unprivileged user id */
int m_uid;

virtual void SetUp() {
	if (geteuid() != 0) {
		GTEST_SKIP() << "This test must be run as root";
	}

	FuseTest::SetUp();
}
};

class AllowOther: public NoAllowOther {

public:
virtual void SetUp() {
	m_allow_other = true;
	NoAllowOther::SetUp();
}
};

TEST_F(AllowOther, allowed)
{
	fork(true, [&] {
			uint64_t ino = 42;

			expect_lookup(RELPATH, ino, S_IFREG | 0644, 0, 1);
			expect_open(ino, 0, 1);
			expect_release(ino, FH);
			expect_getattr(ino, 0);
		}, []() {
			int fd;

			fd = open(FULLPATH, O_RDONLY);
			if (fd < 0) {
				perror("open");
				return(1);
			}
			return 0;
		}
	);
}

/*
 * A variation of the Open.multiple_creds test showing how the bug can lead to a
 * privilege elevation.  The first process is privileged and opens a file only
 * visible to root.  The second process is unprivileged and shouldn't be able
 * to open the file, but does thanks to the bug
 */
TEST_F(AllowOther, privilege_escalation)
{
	const static char FULLPATH[] = "mountpoint/some_file.txt";
	const static char RELPATH[] = "some_file.txt";
	int fd1;
	const static uint64_t ino = 42;
	const static uint64_t fh = 100;

	/* Fork a child to open the file with different credentials */
	fork(true, [&] {

		expect_lookup(RELPATH, ino, S_IFREG | 0600, 0, 2);
		EXPECT_CALL(*m_mock, process(
			ResultOf([=](auto in) {
				return (in->header.opcode == FUSE_OPEN &&
					in->header.pid == (uint32_t)getpid() &&
					in->header.uid == (uint32_t)geteuid() &&
					in->header.nodeid == ino);
			}, Eq(true)),
			_)
		).WillOnce(Invoke(
			ReturnImmediate([](auto in __unused, auto out) {
			out->body.open.fh = fh;
			out->header.len = sizeof(out->header);
			SET_OUT_HEADER_LEN(out, open);
		})));

		EXPECT_CALL(*m_mock, process(
			ResultOf([=](auto in) {
				return (in->header.opcode == FUSE_OPEN &&
					in->header.pid != (uint32_t)getpid() &&
					in->header.uid != (uint32_t)geteuid() &&
					in->header.nodeid == ino);
			}, Eq(true)),
			_)
		).Times(AnyNumber())
		.WillRepeatedly(Invoke(ReturnErrno(EPERM)));
		expect_getattr(ino, 0);

		fd1 = open(FULLPATH, O_RDONLY);
		EXPECT_LE(0, fd1) << strerror(errno);
	}, [] {
		int fd0;

		fd0 = open(FULLPATH, O_RDONLY);
		if (fd0 >= 0) {
			fprintf(stderr, "Privilege escalation!\n");
			return 1;
		}
		if (errno != EPERM) {
			fprintf(stderr, "Unexpected error %s\n",
				strerror(errno));
			return 1;
		}
		return 0;
	}
	);
	/* Deliberately leak fd1.  close(2) will be tested in release.cc */
}

TEST_F(NoAllowOther, disallowed)
{
	fork(true, [] {
		}, []() {
			int fd;

			fd = open(FULLPATH, O_RDONLY);
			if (fd >= 0) {
				fprintf(stderr, "open should've failed\n");
				return(1);
			} else if (errno != EPERM) {
				fprintf(stderr, "Unexpected error: %s\n",
					strerror(errno));
				return(1);
			}
			return 0;
		}
	);
}