289 lines
10 KiB
C++
289 lines
10 KiB
C++
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#include <string>
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#include "gtest/gtest.h"
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#include "test/util/capability_util.h"
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#include "test/util/file_descriptor.h"
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#include "test/util/fs_util.h"
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#include "test/util/temp_path.h"
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#include "test/util/test_util.h"
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namespace gvisor {
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namespace testing {
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namespace {
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mode_t FilePermission(const std::string& path) {
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struct stat buf = {0};
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TEST_CHECK(lstat(path.c_str(), &buf) == 0);
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return buf.st_mode & 0777;
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}
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// Test that name collisions are checked on the new link path, not the source
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// path.
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TEST(SymlinkTest, CanCreateSymlinkWithCachedSourceDirent) {
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const std::string srcname = NewTempAbsPath();
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const std::string newname = NewTempAbsPath();
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const std::string basedir = std::string(Dirname(srcname));
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ASSERT_EQ(basedir, Dirname(newname));
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ASSERT_THAT(chdir(basedir.c_str()), SyscallSucceeds());
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// Open the source node to cause the underlying dirent to be cached. It will
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// remain cached while we have the file open.
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int fd;
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ASSERT_THAT(fd = open(srcname.c_str(), O_CREAT | O_RDWR, 0666),
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SyscallSucceeds());
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FileDescriptor fd_closer(fd);
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// Attempt to create a symlink. If the bug exists, this will fail since the
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// dirent link creation code will check for a name collision on the source
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// link name.
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EXPECT_THAT(symlink(std::string(Basename(srcname)).c_str(),
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std::string(Basename(newname)).c_str()),
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SyscallSucceeds());
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}
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TEST(SymlinkTest, CanCreateSymlinkFile) {
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const std::string oldname = NewTempAbsPath();
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const std::string newname = NewTempAbsPath();
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int fd;
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ASSERT_THAT(fd = open(oldname.c_str(), O_CREAT | O_RDWR, 0666),
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SyscallSucceeds());
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EXPECT_THAT(close(fd), SyscallSucceeds());
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EXPECT_THAT(symlink(oldname.c_str(), newname.c_str()), SyscallSucceeds());
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EXPECT_EQ(FilePermission(newname), 0777);
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auto link = ASSERT_NO_ERRNO_AND_VALUE(ReadLink(newname));
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EXPECT_EQ(oldname, link);
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EXPECT_THAT(unlink(newname.c_str()), SyscallSucceeds());
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EXPECT_THAT(unlink(oldname.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, CanCreateSymlinkDir) {
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const std::string olddir = NewTempAbsPath();
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const std::string newdir = NewTempAbsPath();
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EXPECT_THAT(mkdir(olddir.c_str(), 0777), SyscallSucceeds());
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EXPECT_THAT(symlink(olddir.c_str(), newdir.c_str()), SyscallSucceeds());
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EXPECT_EQ(FilePermission(newdir), 0777);
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auto link = ASSERT_NO_ERRNO_AND_VALUE(ReadLink(newdir));
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EXPECT_EQ(olddir, link);
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EXPECT_THAT(unlink(newdir.c_str()), SyscallSucceeds());
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ASSERT_THAT(rmdir(olddir.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, CannotCreateSymlinkInReadOnlyDir) {
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// Drop capabilities that allow us to override file and directory permissions.
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ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false));
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ASSERT_NO_ERRNO(SetCapability(CAP_DAC_READ_SEARCH, false));
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const std::string olddir = NewTempAbsPath();
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ASSERT_THAT(mkdir(olddir.c_str(), 0444), SyscallSucceeds());
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const std::string newdir = NewTempAbsPathInDir(olddir);
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EXPECT_THAT(symlink(olddir.c_str(), newdir.c_str()),
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SyscallFailsWithErrno(EACCES));
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ASSERT_THAT(rmdir(olddir.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, CannotSymlinkOverExistingFile) {
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const std::string oldname = NewTempAbsPath();
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const std::string newname = NewTempAbsPath();
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int oldfd;
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int newfd;
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ASSERT_THAT(oldfd = open(oldname.c_str(), O_CREAT | O_RDWR, 0666),
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SyscallSucceeds());
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EXPECT_THAT(close(oldfd), SyscallSucceeds());
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ASSERT_THAT(newfd = open(newname.c_str(), O_CREAT | O_RDWR, 0666),
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SyscallSucceeds());
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EXPECT_THAT(close(newfd), SyscallSucceeds());
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EXPECT_THAT(symlink(oldname.c_str(), newname.c_str()),
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SyscallFailsWithErrno(EEXIST));
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EXPECT_THAT(unlink(oldname.c_str()), SyscallSucceeds());
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EXPECT_THAT(unlink(newname.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, OldnameIsEmpty) {
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const std::string newname = NewTempAbsPath();
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EXPECT_THAT(symlink("", newname.c_str()), SyscallFailsWithErrno(ENOENT));
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}
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TEST(SymlinkTest, OldnameIsDangling) {
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const std::string newname = NewTempAbsPath();
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EXPECT_THAT(symlink("/dangling", newname.c_str()), SyscallSucceeds());
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// This is required for S/R random save tests, which pre-run this test
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// in the same TEST_TMPDIR, which means that we need to clean it for any
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// operations exclusively creating files, like symlink above.
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EXPECT_THAT(unlink(newname.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, NewnameCannotExist) {
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const std::string newname =
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JoinPath(GetAbsoluteTestTmpdir(), "thisdoesnotexist", "foo");
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EXPECT_THAT(symlink("/thisdoesnotmatter", newname.c_str()),
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SyscallFailsWithErrno(ENOENT));
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}
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TEST(SymlinkTest, CanEvaluateLink) {
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const std::string oldname = NewTempAbsPath();
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const std::string newname = NewTempAbsPath();
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int fd;
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ASSERT_THAT(fd = open(oldname.c_str(), O_CREAT | O_RDWR, 0666),
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SyscallSucceeds());
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struct stat old;
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EXPECT_THAT(fstat(fd, &old), SyscallSucceeds());
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EXPECT_THAT(close(fd), SyscallSucceeds());
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EXPECT_THAT(symlink(oldname.c_str(), newname.c_str()), SyscallSucceeds());
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EXPECT_EQ(FilePermission(newname), 0777);
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EXPECT_THAT(fd = open(newname.c_str(), O_RDWR, 0666), SyscallSucceeds());
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struct stat old_linked;
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EXPECT_THAT(fstat(fd, &old_linked), SyscallSucceeds());
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EXPECT_THAT(close(fd), SyscallSucceeds());
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// Check that in fact newname points to the file we expect.
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// FIXME: use only inodes here once they are consistent,
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// but this is better than nothing.
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EXPECT_EQ(old.st_dev, old_linked.st_dev);
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EXPECT_EQ(old.st_mode, old_linked.st_mode);
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EXPECT_EQ(old.st_size, old_linked.st_size);
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EXPECT_THAT(unlink(newname.c_str()), SyscallSucceeds());
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EXPECT_THAT(unlink(oldname.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, TargetIsNotMapped) {
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const std::string oldname = NewTempAbsPath();
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const std::string newname = NewTempAbsPath();
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int fd;
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// Create the target so that when we read the link, it exists.
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ASSERT_THAT(fd = open(oldname.c_str(), O_CREAT | O_RDWR, 0666),
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SyscallSucceeds());
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EXPECT_THAT(close(fd), SyscallSucceeds());
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// Create a symlink called newname that points to oldname.
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EXPECT_THAT(symlink(oldname.c_str(), newname.c_str()), SyscallSucceeds());
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std::vector<char> buf(1024);
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int linksize;
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// Read the link and assert that the oldname is still the same.
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EXPECT_THAT(linksize = readlink(newname.c_str(), buf.data(), 1024),
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SyscallSucceeds());
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EXPECT_EQ(0, strncmp(oldname.c_str(), buf.data(), linksize));
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EXPECT_THAT(unlink(newname.c_str()), SyscallSucceeds());
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EXPECT_THAT(unlink(oldname.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, PreadFromSymlink) {
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std::string name = NewTempAbsPath();
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int fd;
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ASSERT_THAT(fd = open(name.c_str(), O_CREAT, 0644), SyscallSucceeds());
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ASSERT_THAT(close(fd), SyscallSucceeds());
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std::string linkname = NewTempAbsPath();
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ASSERT_THAT(symlink(name.c_str(), linkname.c_str()), SyscallSucceeds());
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ASSERT_THAT(fd = open(linkname.c_str(), O_RDONLY), SyscallSucceeds());
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char buf[1024];
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EXPECT_THAT(pread64(fd, buf, 1024, 0), SyscallSucceeds());
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EXPECT_THAT(close(fd), SyscallSucceeds());
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EXPECT_THAT(unlink(name.c_str()), SyscallSucceeds());
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EXPECT_THAT(unlink(linkname.c_str()), SyscallSucceeds());
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}
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TEST(SymlinkTest, SymlinkAtDegradedPermissions_NoRandomSave) {
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// Drop capabilities that allow us to override file and directory permissions.
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ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false));
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ASSERT_NO_ERRNO(SetCapability(CAP_DAC_READ_SEARCH, false));
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auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
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auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileIn(dir.path()));
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int dirfd;
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ASSERT_THAT(dirfd = open(dir.path().c_str(), O_DIRECTORY, 0),
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SyscallSucceeds());
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const DisableSave ds; // Permissions are dropped.
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EXPECT_THAT(fchmod(dirfd, 0), SyscallSucceeds());
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std::string basename = std::string(Basename(file.path()));
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EXPECT_THAT(symlinkat("/dangling", dirfd, basename.c_str()),
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SyscallFailsWithErrno(EACCES));
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EXPECT_THAT(close(dirfd), SyscallSucceeds());
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}
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TEST(SymlinkTest, ReadlinkAtDegradedPermissions_NoRandomSave) {
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// Drop capabilities that allow us to override file and directory permissions.
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ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false));
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ASSERT_NO_ERRNO(SetCapability(CAP_DAC_READ_SEARCH, false));
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auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
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const std::string oldpath = NewTempAbsPathInDir(dir.path());
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const std::string oldbase = std::string(Basename(oldpath));
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ASSERT_THAT(symlink("/dangling", oldpath.c_str()), SyscallSucceeds());
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int dirfd;
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EXPECT_THAT(dirfd = open(dir.path().c_str(), O_DIRECTORY, 0),
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SyscallSucceeds());
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const DisableSave ds; // Permissions are dropped.
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EXPECT_THAT(fchmod(dirfd, 0), SyscallSucceeds());
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char buf[1024];
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int linksize;
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EXPECT_THAT(linksize = readlinkat(dirfd, oldbase.c_str(), buf, 1024),
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SyscallFailsWithErrno(EACCES));
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EXPECT_THAT(close(dirfd), SyscallSucceeds());
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}
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TEST(SymlinkTest, ChmodSymlink) {
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auto target = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
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const std::string newpath = NewTempAbsPath();
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ASSERT_THAT(symlink(target.path().c_str(), newpath.c_str()),
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SyscallSucceeds());
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EXPECT_EQ(FilePermission(newpath), 0777);
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EXPECT_THAT(chmod(newpath.c_str(), 0666), SyscallSucceeds());
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EXPECT_EQ(FilePermission(newpath), 0777);
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}
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} // namespace
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} // namespace testing
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} // namespace gvisor
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