3 files changed, 181 insertions, 0 deletions
diff --git a/test/util/BUILD b/test/util/BUILD
index 8985b54af..cc83221ea 100644
--- a/test/util/BUILD
+++ b/test/util/BUILD
@@ -401,3 +401,16 @@ cc_library(
         "@com_google_absl//absl/strings",
     ],
 )
+
+cc_library(
+    name = "verity_util",
+    testonly = 1,
+    srcs = ["verity_util.cc"],
+    hdrs = ["verity_util.h"],
+    deps = [
+        ":fs_util",
+        ":mount_util",
+        ":posix_error",
+        ":temp_path",
+    ],
+)
diff --git a/test/util/verity_util.cc b/test/util/verity_util.cc
new file mode 100644
index 000000000..f1b4c251b
--- /dev/null
+++ b/test/util/verity_util.cc
@@ -0,0 +1,93 @@
+// Copyright 2021 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 "test/util/verity_util.h"
+
+#include "test/util/fs_util.h"
+#include "test/util/mount_util.h"
+#include "test/util/temp_path.h"
+
+namespace gvisor {
+namespace testing {
+
+std::string BytesToHexString(uint8_t bytes[], int size) {
+  std::stringstream ss;
+  ss << std::hex;
+  for (int i = 0; i < size; ++i) {
+    ss << std::setw(2) << std::setfill('0') << static_cast<int>(bytes[i]);
+  }
+  return ss.str();
+}
+
+std::string MerklePath(absl::string_view path) {
+  return JoinPath(Dirname(path),
+                  std::string(kMerklePrefix) + std::string(Basename(path)));
+}
+
+std::string MerkleRootPath(absl::string_view path) {
+  return JoinPath(Dirname(path),
+                  std::string(kMerkleRootPrefix) + std::string(Basename(path)));
+}
+
+PosixError FlipRandomBit(int fd, int size) {
+  // Generate a random offset in the file.
+  srand(time(nullptr));
+  unsigned int seed = 0;
+  int random_offset = rand_r(&seed) % size;
+
+  // Read a random byte and flip a bit in it.
+  char buf[1];
+  RETURN_ERROR_IF_SYSCALL_FAIL(PreadFd(fd, buf, 1, random_offset));
+  buf[0] ^= 1;
+  RETURN_ERROR_IF_SYSCALL_FAIL(PwriteFd(fd, buf, 1, random_offset));
+  return NoError();
+}
+
+PosixErrorOr<std::string> MountVerity(std::string tmpfs_dir,
+                                      std::string filename) {
+  // Mount a verity fs on the existing tmpfs mount.
+  std::string mount_opts = "lower_path=" + tmpfs_dir;
+  ASSIGN_OR_RETURN_ERRNO(TempPath verity_dir, TempPath::CreateDir());
+  RETURN_ERROR_IF_SYSCALL_FAIL(
+      mount("", verity_dir.path().c_str(), "verity", 0, mount_opts.c_str()));
+
+  // Enable both the file and the directory.
+  ASSIGN_OR_RETURN_ERRNO(
+      auto fd, Open(JoinPath(verity_dir.path(), filename), O_RDONLY, 0777));
+  RETURN_ERROR_IF_SYSCALL_FAIL(ioctl(fd.get(), FS_IOC_ENABLE_VERITY));
+  ASSIGN_OR_RETURN_ERRNO(auto dir_fd, Open(verity_dir.path(), O_RDONLY, 0777));
+  RETURN_ERROR_IF_SYSCALL_FAIL(ioctl(dir_fd.get(), FS_IOC_ENABLE_VERITY));
+
+  // Measure the root hash.
+  uint8_t digest_array[sizeof(struct fsverity_digest) + kMaxDigestSize] = {0};
+  struct fsverity_digest* digest =
+      reinterpret_cast<struct fsverity_digest*>(digest_array);
+  digest->digest_size = kMaxDigestSize;
+  RETURN_ERROR_IF_SYSCALL_FAIL(
+      ioctl(dir_fd.get(), FS_IOC_MEASURE_VERITY, digest));
+
+  // Mount a verity fs with specified root hash.
+  mount_opts +=
+      ",root_hash=" + BytesToHexString(digest->digest, digest->digest_size);
+  ASSIGN_OR_RETURN_ERRNO(TempPath verity_with_hash_dir, TempPath::CreateDir());
+  RETURN_ERROR_IF_SYSCALL_FAIL(mount("", verity_with_hash_dir.path().c_str(),
+                                     "verity", 0, mount_opts.c_str()));
+  // Verity directories should not be deleted. Release the TempPath objects to
+  // prevent those directories from being deleted by the destructor.
+  verity_dir.release();
+  return verity_with_hash_dir.release();
+}
+
+}  // namespace testing
+}  // namespace gvisor
diff --git a/test/util/verity_util.h b/test/util/verity_util.h
new file mode 100644
index 000000000..18743ecd6
--- /dev/null
+++ b/test/util/verity_util.h
@@ -0,0 +1,75 @@
+// Copyright 2021 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.
+
+#ifndef GVISOR_TEST_UTIL_VERITY_UTIL_H_
+#define GVISOR_TEST_UTIL_VERITY_UTIL_H_
+
+#include <stdint.h>
+
+#include "test/util/posix_error.h"
+
+namespace gvisor {
+namespace testing {
+
+#ifndef FS_IOC_ENABLE_VERITY
+#define FS_IOC_ENABLE_VERITY 1082156677
+#endif
+
+#ifndef FS_IOC_MEASURE_VERITY
+#define FS_IOC_MEASURE_VERITY 3221513862
+#endif
+
+#ifndef FS_VERITY_FL
+#define FS_VERITY_FL 1048576
+#endif
+
+#ifndef FS_IOC_GETFLAGS
+#define FS_IOC_GETFLAGS 2148034049
+#endif
+
+struct fsverity_digest {
+  unsigned short digest_algorithm;
+  unsigned short digest_size; /* input/output */
+  unsigned char digest[];
+};
+
+constexpr int kMaxDigestSize = 64;
+constexpr int kDefaultDigestSize = 32;
+constexpr char kContents[] = "foobarbaz";
+constexpr char kMerklePrefix[] = ".merkle.verity.";
+constexpr char kMerkleRootPrefix[] = ".merkleroot.verity.";
+
+// Get the Merkle tree file path for |path|.
+std::string MerklePath(absl::string_view path);
+
+// Get the root Merkle tree file path for |path|.
+std::string MerkleRootPath(absl::string_view path);
+
+// Provide a function to convert bytes to hex string, since
+// absl::BytesToHexString does not seem to be compatible with golang
+// hex.DecodeString used in verity due to zero-padding.
+std::string BytesToHexString(uint8_t bytes[], int size);
+
+// Flip a random bit in the file represented by fd.
+PosixError FlipRandomBit(int fd, int size);
+
+// Mount a verity on the tmpfs and enable both the file and the direcotry. Then
+// mount a new verity with measured root hash.
+PosixErrorOr<std::string> MountVerity(std::string tmpfs_dir,
+                                      std::string filename);
+
+}  // namespace testing
+}  // namespace gvisor
+
+#endif  // GVISOR_TEST_UTIL_VERITY_UTIL_H_