diff options
Diffstat (limited to 'test/syscalls/linux/setgid.cc')
| -rw-r--r-- | test/syscalls/linux/setgid.cc | 370 |
1 files changed, 370 insertions, 0 deletions
diff --git a/test/syscalls/linux/setgid.cc b/test/syscalls/linux/setgid.cc new file mode 100644 index 000000000..bfd91ba4f --- /dev/null +++ b/test/syscalls/linux/setgid.cc @@ -0,0 +1,370 @@ +// Copyright 2020 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 <limits.h> +#include <sys/types.h> +#include <unistd.h> + +#include "gtest/gtest.h" +#include "test/util/capability_util.h" +#include "test/util/cleanup.h" +#include "test/util/fs_util.h" +#include "test/util/posix_error.h" +#include "test/util/temp_path.h" +#include "test/util/test_util.h" + +namespace gvisor { +namespace testing { + +namespace { + +constexpr int kDirmodeMask = 07777; +constexpr int kDirmodeSgid = S_ISGID | 0777; +constexpr int kDirmodeNoExec = S_ISGID | 0767; +constexpr int kDirmodeNoSgid = 0777; + +// Sets effective GID and returns a Cleanup that restores the original. +PosixErrorOr<Cleanup> Setegid(gid_t egid) { + gid_t old_gid = getegid(); + if (setegid(egid) < 0) { + return PosixError(errno, absl::StrFormat("setegid(%d)", egid)); + } + return Cleanup( + [old_gid]() { EXPECT_THAT(setegid(old_gid), SyscallSucceeds()); }); +} + +// Returns a pair of groups that the user is a member of. +PosixErrorOr<std::pair<gid_t, gid_t>> Groups() { + // See whether the user is a member of at least 2 groups. + std::vector<gid_t> groups(64); + for (; groups.size() <= NGROUPS_MAX; groups.resize(groups.size() * 2)) { + int ngroups = getgroups(groups.size(), groups.data()); + if (ngroups < 0 && errno == EINVAL) { + // Need a larger list. + continue; + } + if (ngroups < 0) { + return PosixError(errno, absl::StrFormat("getgroups(%d, %p)", + groups.size(), groups.data())); + } + if (ngroups >= 2) { + return std::pair<gid_t, gid_t>(groups[0], groups[1]); + } + // There aren't enough groups. + break; + } + + // If we're root in the root user namespace, we can set our GID to whatever we + // want. Try that before giving up. + constexpr gid_t kGID1 = 1111; + constexpr gid_t kGID2 = 2222; + auto cleanup1 = Setegid(kGID1); + if (!cleanup1.ok()) { + return cleanup1.error(); + } + auto cleanup2 = Setegid(kGID2); + if (!cleanup2.ok()) { + return cleanup2.error(); + } + return std::pair<gid_t, gid_t>(kGID1, kGID2); +} + +class SetgidDirTest : public ::testing::Test { + protected: + void SetUp() override { + original_gid_ = getegid(); + + // TODO(b/175325250): Enable when setgid directories are supported. + SKIP_IF(IsRunningOnGvisor()); + SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SETGID))); + + temp_dir_ = ASSERT_NO_ERRNO_AND_VALUE( + TempPath::CreateDirWith(GetAbsoluteTestTmpdir(), 0777 /* mode */)); + groups_ = ASSERT_NO_ERRNO_AND_VALUE(Groups()); + } + + void TearDown() override { + ASSERT_THAT(setegid(original_gid_), SyscallSucceeds()); + } + + void MkdirAsGid(gid_t gid, const std::string& path, mode_t mode) { + auto cleanup = ASSERT_NO_ERRNO_AND_VALUE(Setegid(gid)); + ASSERT_THAT(mkdir(path.c_str(), mode), SyscallSucceeds()); + } + + PosixErrorOr<struct stat> Stat(const std::string& path) { + struct stat stats; + if (stat(path.c_str(), &stats) < 0) { + return PosixError(errno, absl::StrFormat("stat(%s, _)", path)); + } + return stats; + } + + PosixErrorOr<struct stat> Stat(const FileDescriptor& fd) { + struct stat stats; + if (fstat(fd.get(), &stats) < 0) { + return PosixError(errno, "fstat(_, _)"); + } + return stats; + } + + TempPath temp_dir_; + std::pair<gid_t, gid_t> groups_; + gid_t original_gid_; +}; + +// The control test. Files created with a given GID are owned by that group. +TEST_F(SetgidDirTest, Control) { + // Set group to G1 and create a directory. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, 0777)); + + // Set group to G2, create a file in g1owned, and confirm that G2 owns it. + ASSERT_THAT(setegid(groups_.second), SyscallSucceeds()); + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE( + Open(JoinPath(g1owned, "g2owned").c_str(), O_CREAT | O_RDWR, 0777)); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.second); +} + +// Setgid directories cause created files to inherit GID. +TEST_F(SetgidDirTest, CreateFile) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeSgid)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeSgid), SyscallSucceeds()); + + // Set group to G2, create a file, and confirm that G1 owns it. + ASSERT_THAT(setegid(groups_.second), SyscallSucceeds()); + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE( + Open(JoinPath(g1owned, "g2created").c_str(), O_CREAT | O_RDWR, 0666)); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.first); +} + +// Setgid directories cause created directories to inherit GID. +TEST_F(SetgidDirTest, CreateDir) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeSgid)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeSgid), SyscallSucceeds()); + + // Set group to G2, create a directory, confirm that G1 owns it, and that the + // setgid bit is enabled. + auto g2created = JoinPath(g1owned, "g2created"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.second, g2created, 0666)); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(g2created)); + EXPECT_EQ(stats.st_gid, groups_.first); + EXPECT_EQ(stats.st_mode & S_ISGID, S_ISGID); +} + +// Setgid directories with group execution disabled still cause GID inheritance. +TEST_F(SetgidDirTest, NoGroupExec) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeNoExec)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeNoExec), SyscallSucceeds()); + + // Set group to G2, create a directory, confirm that G2 owns it, and that the + // setgid bit is enabled. + auto g2created = JoinPath(g1owned, "g2created"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.second, g2created, 0666)); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(g2created)); + EXPECT_EQ(stats.st_gid, groups_.first); + EXPECT_EQ(stats.st_mode & S_ISGID, S_ISGID); +} + +// Setting the setgid bit on directories with an existing file does not change +// the file's group. +TEST_F(SetgidDirTest, OldFile) { + // Set group to G1 and create a directory. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeNoSgid)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeNoSgid), SyscallSucceeds()); + + // Set group to G2, create a file, confirm that G2 owns it. + ASSERT_THAT(setegid(groups_.second), SyscallSucceeds()); + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE( + Open(JoinPath(g1owned, "g2created").c_str(), O_CREAT | O_RDWR, 0666)); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.second); + + // Enable setgid. + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeSgid), SyscallSucceeds()); + + // Confirm that the file's group is still G2. + stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.second); +} + +// Setting the setgid bit on directories with an existing subdirectory does not +// change the subdirectory's group. +TEST_F(SetgidDirTest, OldDir) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeNoSgid)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeNoSgid), SyscallSucceeds()); + + // Set group to G2, create a directory, confirm that G2 owns it. + ASSERT_THAT(setegid(groups_.second), SyscallSucceeds()); + auto g2created = JoinPath(g1owned, "g2created"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.second, g2created, 0666)); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(g2created)); + EXPECT_EQ(stats.st_gid, groups_.second); + + // Enable setgid. + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeSgid), SyscallSucceeds()); + + // Confirm that the file's group is still G2. + stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(g2created)); + EXPECT_EQ(stats.st_gid, groups_.second); +} + +// Chowning a file clears the setgid and setuid bits. +TEST_F(SetgidDirTest, ChownFileClears) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeMask)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeMask), SyscallSucceeds()); + + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE( + Open(JoinPath(g1owned, "newfile").c_str(), O_CREAT | O_RDWR, 0666)); + ASSERT_THAT(fchmod(fd.get(), 0777 | S_ISUID | S_ISGID), SyscallSucceeds()); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.first); + EXPECT_EQ(stats.st_mode & (S_ISUID | S_ISGID), S_ISUID | S_ISGID); + + // Change the owning group. + ASSERT_THAT(fchown(fd.get(), -1, groups_.second), SyscallSucceeds()); + + // The setgid and setuid bits should be cleared. + stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.second); + EXPECT_EQ(stats.st_mode & (S_ISUID | S_ISGID), 0); +} + +// Chowning a file with setgid enabled, but not the group exec bit, does not +// clear the setgid bit. Such files are mandatory locked. +TEST_F(SetgidDirTest, ChownNoExecFileDoesNotClear) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeNoExec)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeNoExec), SyscallSucceeds()); + + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE( + Open(JoinPath(g1owned, "newdir").c_str(), O_CREAT | O_RDWR, 0666)); + ASSERT_THAT(fchmod(fd.get(), 0766 | S_ISUID | S_ISGID), SyscallSucceeds()); + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.first); + EXPECT_EQ(stats.st_mode & (S_ISUID | S_ISGID), S_ISUID | S_ISGID); + + // Change the owning group. + ASSERT_THAT(fchown(fd.get(), -1, groups_.second), SyscallSucceeds()); + + // Only the setuid bit is cleared. + stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(fd)); + EXPECT_EQ(stats.st_gid, groups_.second); + EXPECT_EQ(stats.st_mode & (S_ISUID | S_ISGID), S_ISGID); +} + +// Chowning a directory with setgid enabled does not clear the bit. +TEST_F(SetgidDirTest, ChownDirDoesNotClear) { + // Set group to G1, create a directory, and enable setgid. + auto g1owned = JoinPath(temp_dir_.path(), "g1owned/"); + ASSERT_NO_FATAL_FAILURE(MkdirAsGid(groups_.first, g1owned, kDirmodeMask)); + ASSERT_THAT(chmod(g1owned.c_str(), kDirmodeMask), SyscallSucceeds()); + + // Change the owning group. + ASSERT_THAT(chown(g1owned.c_str(), -1, groups_.second), SyscallSucceeds()); + + struct stat stats = ASSERT_NO_ERRNO_AND_VALUE(Stat(g1owned)); + EXPECT_EQ(stats.st_gid, groups_.second); + EXPECT_EQ(stats.st_mode & kDirmodeMask, kDirmodeMask); +} + +struct FileModeTestcase { + std::string name; + mode_t mode; + mode_t result_mode; + + FileModeTestcase(const std::string& name, mode_t mode, mode_t result_mode) + : name(name), mode(mode), result_mode(result_mode) {} +}; + +class FileModeTest : public ::testing::TestWithParam<FileModeTestcase> {}; + +TEST_P(FileModeTest, WriteToFile) { + // TODO(b/175325250): Enable when setgid directories are supported. + SKIP_IF(IsRunningOnGvisor()); + + auto temp_dir = ASSERT_NO_ERRNO_AND_VALUE( + TempPath::CreateDirWith(GetAbsoluteTestTmpdir(), 0777 /* mode */)); + auto path = JoinPath(temp_dir.path(), GetParam().name); + FileDescriptor fd = + ASSERT_NO_ERRNO_AND_VALUE(Open(path.c_str(), O_CREAT | O_RDWR, 0666)); + ASSERT_THAT(fchmod(fd.get(), GetParam().mode), SyscallSucceeds()); + struct stat stats; + ASSERT_THAT(fstat(fd.get(), &stats), SyscallSucceeds()); + EXPECT_EQ(stats.st_mode & kDirmodeMask, GetParam().mode); + + // For security reasons, writing to the file clears the SUID bit, and clears + // the SGID bit when the group executable bit is unset (which is not a true + // SGID binary). + constexpr char kInput = 'M'; + ASSERT_THAT(write(fd.get(), &kInput, sizeof(kInput)), + SyscallSucceedsWithValue(sizeof(kInput))); + + ASSERT_THAT(fstat(fd.get(), &stats), SyscallSucceeds()); + EXPECT_EQ(stats.st_mode & kDirmodeMask, GetParam().result_mode); +} + +TEST_P(FileModeTest, TruncateFile) { + // TODO(b/175325250): Enable when setgid directories are supported. + SKIP_IF(IsRunningOnGvisor()); + + auto temp_dir = ASSERT_NO_ERRNO_AND_VALUE( + TempPath::CreateDirWith(GetAbsoluteTestTmpdir(), 0777 /* mode */)); + auto path = JoinPath(temp_dir.path(), GetParam().name); + FileDescriptor fd = + ASSERT_NO_ERRNO_AND_VALUE(Open(path.c_str(), O_CREAT | O_RDWR, 0666)); + ASSERT_THAT(fchmod(fd.get(), GetParam().mode), SyscallSucceeds()); + struct stat stats; + ASSERT_THAT(fstat(fd.get(), &stats), SyscallSucceeds()); + EXPECT_EQ(stats.st_mode & kDirmodeMask, GetParam().mode); + + // For security reasons, truncating the file clears the SUID bit, and clears + // the SGID bit when the group executable bit is unset (which is not a true + // SGID binary). + ASSERT_THAT(ftruncate(fd.get(), 0), SyscallSucceeds()); + + ASSERT_THAT(fstat(fd.get(), &stats), SyscallSucceeds()); + EXPECT_EQ(stats.st_mode & kDirmodeMask, GetParam().result_mode); +} + +INSTANTIATE_TEST_SUITE_P( + FileModes, FileModeTest, + ::testing::ValuesIn<FileModeTestcase>( + {FileModeTestcase("normal file", 0777, 0777), + FileModeTestcase("setuid", S_ISUID | 0777, 00777), + FileModeTestcase("setgid", S_ISGID | 0777, 00777), + FileModeTestcase("setuid and setgid", S_ISUID | S_ISGID | 0777, 00777), + FileModeTestcase("setgid without exec", S_ISGID | 0767, + S_ISGID | 0767), + FileModeTestcase("setuid and setgid without exec", + S_ISGID | S_ISUID | 0767, S_ISGID | 0767)})); + +} // namespace + +} // namespace testing +} // namespace gvisor |