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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <fcntl.h>
#include <grp.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <unistd.h>
#include <vector>
#include "gtest/gtest.h"
#include "absl/flags/flag.h"
#include "test/util/capability_util.h"
#include "test/util/file_descriptor.h"
#include "test/util/fs_util.h"
#include "test/util/temp_path.h"
#include "test/util/test_util.h"
#include "test/util/thread_util.h"
ABSL_FLAG(int32_t, scratch_uid, 65534, "first scratch UID");
ABSL_FLAG(int32_t, scratch_gid, 65534, "first scratch GID");
namespace gvisor {
namespace testing {
namespace {
TEST(StickyTest, StickyBitPermDenied) {
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SETUID)));
const TempPath parent = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
EXPECT_THAT(chmod(parent.path().c_str(), 0777 | S_ISVTX), SyscallSucceeds());
// After changing credentials below, we need to use an open fd to make
// modifications in the parent dir, because there is no guarantee that we will
// still have the ability to open it.
const FileDescriptor parent_fd =
ASSERT_NO_ERRNO_AND_VALUE(Open(parent.path(), O_DIRECTORY));
ASSERT_THAT(openat(parent_fd.get(), "file", O_CREAT), SyscallSucceeds());
ASSERT_THAT(mkdirat(parent_fd.get(), "dir", 0777), SyscallSucceeds());
ASSERT_THAT(symlinkat("xyz", parent_fd.get(), "link"), SyscallSucceeds());
// Drop privileges and change IDs only in child thread, or else this parent
// thread won't be able to open some log files after the test ends.
ScopedThread([&] {
// Drop privileges.
if (HaveCapability(CAP_FOWNER).ValueOrDie()) {
EXPECT_NO_ERRNO(SetCapability(CAP_FOWNER, false));
}
// Change EUID and EGID.
EXPECT_THAT(
syscall(SYS_setresgid, -1, absl::GetFlag(FLAGS_scratch_gid), -1),
SyscallSucceeds());
EXPECT_THAT(
syscall(SYS_setresuid, -1, absl::GetFlag(FLAGS_scratch_uid), -1),
SyscallSucceeds());
EXPECT_THAT(renameat(parent_fd.get(), "file", parent_fd.get(), "file2"),
SyscallFailsWithErrno(EPERM));
EXPECT_THAT(unlinkat(parent_fd.get(), "file", 0),
SyscallFailsWithErrno(EPERM));
EXPECT_THAT(unlinkat(parent_fd.get(), "dir", AT_REMOVEDIR),
SyscallFailsWithErrno(EPERM));
EXPECT_THAT(unlinkat(parent_fd.get(), "link", 0),
SyscallFailsWithErrno(EPERM));
});
}
TEST(StickyTest, StickyBitSameUID) {
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SETUID)));
const TempPath parent = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
EXPECT_THAT(chmod(parent.path().c_str(), 0777 | S_ISVTX), SyscallSucceeds());
// After changing credentials below, we need to use an open fd to make
// modifications in the parent dir, because there is no guarantee that we will
// still have the ability to open it.
const FileDescriptor parent_fd =
ASSERT_NO_ERRNO_AND_VALUE(Open(parent.path(), O_DIRECTORY));
ASSERT_THAT(openat(parent_fd.get(), "file", O_CREAT), SyscallSucceeds());
ASSERT_THAT(mkdirat(parent_fd.get(), "dir", 0777), SyscallSucceeds());
ASSERT_THAT(symlinkat("xyz", parent_fd.get(), "link"), SyscallSucceeds());
// Drop privileges and change IDs only in child thread, or else this parent
// thread won't be able to open some log files after the test ends.
ScopedThread([&] {
// Drop privileges.
if (HaveCapability(CAP_FOWNER).ValueOrDie()) {
EXPECT_NO_ERRNO(SetCapability(CAP_FOWNER, false));
}
// Change EGID.
EXPECT_THAT(
syscall(SYS_setresgid, -1, absl::GetFlag(FLAGS_scratch_gid), -1),
SyscallSucceeds());
// We still have the same EUID.
EXPECT_THAT(renameat(parent_fd.get(), "file", parent_fd.get(), "file2"),
SyscallSucceeds());
EXPECT_THAT(unlinkat(parent_fd.get(), "file2", 0), SyscallSucceeds());
EXPECT_THAT(unlinkat(parent_fd.get(), "dir", AT_REMOVEDIR),
SyscallSucceeds());
EXPECT_THAT(unlinkat(parent_fd.get(), "link", 0), SyscallSucceeds());
});
}
TEST(StickyTest, StickyBitCapFOWNER) {
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SETUID)));
const TempPath parent = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
EXPECT_THAT(chmod(parent.path().c_str(), 0777 | S_ISVTX), SyscallSucceeds());
// After changing credentials below, we need to use an open fd to make
// modifications in the parent dir, because there is no guarantee that we will
// still have the ability to open it.
const FileDescriptor parent_fd =
ASSERT_NO_ERRNO_AND_VALUE(Open(parent.path(), O_DIRECTORY));
ASSERT_THAT(openat(parent_fd.get(), "file", O_CREAT), SyscallSucceeds());
ASSERT_THAT(mkdirat(parent_fd.get(), "dir", 0777), SyscallSucceeds());
ASSERT_THAT(symlinkat("xyz", parent_fd.get(), "link"), SyscallSucceeds());
// Drop privileges and change IDs only in child thread, or else this parent
// thread won't be able to open some log files after the test ends.
ScopedThread([&] {
// Set PR_SET_KEEPCAPS.
EXPECT_THAT(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0), SyscallSucceeds());
// Change EUID and EGID.
EXPECT_THAT(
syscall(SYS_setresgid, -1, absl::GetFlag(FLAGS_scratch_gid), -1),
SyscallSucceeds());
EXPECT_THAT(
syscall(SYS_setresuid, -1, absl::GetFlag(FLAGS_scratch_uid), -1),
SyscallSucceeds());
EXPECT_NO_ERRNO(SetCapability(CAP_FOWNER, true));
EXPECT_THAT(renameat(parent_fd.get(), "file", parent_fd.get(), "file2"),
SyscallSucceeds());
EXPECT_THAT(unlinkat(parent_fd.get(), "file2", 0), SyscallSucceeds());
EXPECT_THAT(unlinkat(parent_fd.get(), "dir", AT_REMOVEDIR),
SyscallSucceeds());
EXPECT_THAT(unlinkat(parent_fd.get(), "link", 0), SyscallSucceeds());
});
}
} // namespace
} // namespace testing
} // namespace gvisor
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