Add Ed25519 signature verifier.

Key pair is generated by the test; production server will retrieve
private key from KeyStore, and client will use a hardcoded public key
that matches the Keystore key.

Bug: b:170054326
Change-Id: I676dc48871af75e6a1733ee1d345460e6708d38d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611901
Commit-Queue: Leonid Baraz <lbaraz@chromium.org>
Reviewed-by: Zach Trudo <zatrudo@google.com>
Cr-Commit-Position: refs/heads/master@{#840709}

chrome/browser/BUILD.gn

@@ -1221,6 +1221,8 @@ static_library("browser") {
     "policy/messaging_layer/encryption/encryption.h",
     "policy/messaging_layer/encryption/encryption_module.cc",
     "policy/messaging_layer/encryption/encryption_module.h",
+    "policy/messaging_layer/encryption/verification.cc",
+    "policy/messaging_layer/encryption/verification.h",
     "policy/messaging_layer/public/report_client.cc",
     "policy/messaging_layer/public/report_client.h",
     "policy/messaging_layer/public/report_queue.cc",

chrome/browser/policy/messaging_layer/encryption/verification.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/policy/messaging_layer/encryption/verification.h"
+
+#include "chrome/browser/policy/messaging_layer/util/status.h"
+#include "third_party/boringssl/src/include/openssl/curve25519.h"
+
+namespace reporting {
+
+SignatureVerifier::SignatureVerifier(base::StringPiece verification_public_key)
+    : verification_public_key_(verification_public_key) {}
+
+Status SignatureVerifier::Verify(base::StringPiece message,
+                                 base::StringPiece signature) {
+  if (signature.size() != ED25519_SIGNATURE_LEN) {
+    return Status{error::FAILED_PRECONDITION, "Wrong signature size"};
+  }
+  if (verification_public_key_.size() != ED25519_PUBLIC_KEY_LEN) {
+    return Status{error::FAILED_PRECONDITION, "Wrong public key size"};
+  }
+  const int result = ED25519_verify(
+      reinterpret_cast<const uint8_t*>(message.data()), message.size(),
+      reinterpret_cast<const uint8_t*>(signature.data()),
+      reinterpret_cast<const uint8_t*>(verification_public_key_.data()));
+  if (result != 1) {
+    return Status{error::INVALID_ARGUMENT, "Verification failed"};
+  }
+  return Status::StatusOK();
+}
+
+}  // namespace reporting

chrome/browser/policy/messaging_layer/encryption/verification.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_POLICY_MESSAGING_LAYER_ENCRYPTION_VERIFICATION_H_
+#define CHROME_BROWSER_POLICY_MESSAGING_LAYER_ENCRYPTION_VERIFICATION_H_
+
+#include <string>
+
+#include "base/strings/string_piece.h"
+#include "chrome/browser/policy/messaging_layer/util/status.h"
+
+namespace reporting {
+
+// Helper class that verifies an Ed25519 signed message received from
+// the server. It uses boringssl implementation available on the client.
+class SignatureVerifier {
+ public:
+  // Ed25519 |verification_public_key| must consist of ED25519_PUBLIC_KEY_LEN
+  // bytes.
+  explicit SignatureVerifier(base::StringPiece verification_public_key);
+
+  // Actual verification - returns error status if provided |signature| does not
+  // match |message|. Signature must be ED25519_SIGNATURE_LEN bytes.
+  Status Verify(base::StringPiece message, base::StringPiece signature);
+
+ private:
+  std::string verification_public_key_;
+};
+}  // namespace reporting
+
+#endif  // CHROME_BROWSER_POLICY_MESSAGING_LAYER_ENCRYPTION_VERIFICATION_H_

chrome/browser/policy/messaging_layer/encryption/verification_unittest.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/policy/messaging_layer/encryption/verification.h"
+
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/boringssl/src/include/openssl/curve25519.h"
+
+using ::testing::Eq;
+using ::testing::HasSubstr;
+
+namespace reporting {
+namespace {
+
+class VerificationTest : public ::testing::Test {
+ protected:
+  VerificationTest() = default;
+  void SetUp() override {
+    // Generate key pair
+    ED25519_keypair(public_key_, private_key_);
+  }
+
+  uint8_t public_key_[ED25519_PUBLIC_KEY_LEN];
+  uint8_t private_key_[ED25519_PRIVATE_KEY_LEN];
+};
+
+TEST_F(VerificationTest, SignAndVerify) {
+  static constexpr char message[] = "ABCDEF 012345";
+  // Sign a message.
+  uint8_t signature[ED25519_SIGNATURE_LEN];
+  ASSERT_THAT(ED25519_sign(signature, reinterpret_cast<const uint8_t*>(message),
+                           strlen(message), private_key_),
+              Eq(1));
+
+  // Verify the signature.
+  SignatureVerifier verifier(std::string(
+      reinterpret_cast<const char*>(public_key_), ED25519_PUBLIC_KEY_LEN));
+  EXPECT_OK(
+      verifier.Verify(std::string(message, strlen(message)),
+                      std::string(reinterpret_cast<const char*>(signature),
+                                  ED25519_SIGNATURE_LEN)));
+}
+
+TEST_F(VerificationTest, SignAndFailBadSignature) {
+  static constexpr char message[] = "ABCDEF 012345";
+  // Sign a message.
+  uint8_t signature[ED25519_SIGNATURE_LEN];
+  ASSERT_THAT(ED25519_sign(signature, reinterpret_cast<const uint8_t*>(message),
+                           strlen(message), private_key_),
+              Eq(1));
+
+  // Verify the signature - wrong length.
+  SignatureVerifier verifier(std::string(
+      reinterpret_cast<const char*>(public_key_), ED25519_PUBLIC_KEY_LEN));
+  Status status =
+      verifier.Verify(std::string(message, strlen(message)),
+                      std::string(reinterpret_cast<const char*>(signature),
+                                  ED25519_SIGNATURE_LEN - 1));
+  EXPECT_THAT(status.code(), Eq(error::FAILED_PRECONDITION));
+  EXPECT_THAT(status.message(), HasSubstr("Wrong signature size"));
+
+  // Verify the signature - mismatch.
+  signature[0] = ~signature[0];
+  status = verifier.Verify(std::string(message, strlen(message)),
+                           std::string(reinterpret_cast<const char*>(signature),
+                                       ED25519_SIGNATURE_LEN));
+  EXPECT_THAT(status.code(), Eq(error::INVALID_ARGUMENT));
+  EXPECT_THAT(status.message(), HasSubstr("Verification failed"));
+}
+
+TEST_F(VerificationTest, SignAndFailBadPublicKey) {
+  static constexpr char message[] = "ABCDEF 012345";
+  // Sign a message.
+  uint8_t signature[ED25519_SIGNATURE_LEN];
+  ASSERT_THAT(ED25519_sign(signature, reinterpret_cast<const uint8_t*>(message),
+                           strlen(message), private_key_),
+              Eq(1));
+
+  // Verify the public key - wrong length.
+  SignatureVerifier verifier(std::string(
+      reinterpret_cast<const char*>(public_key_), ED25519_PUBLIC_KEY_LEN - 1));
+  Status status =
+      verifier.Verify(std::string(message, strlen(message)),
+                      std::string(reinterpret_cast<const char*>(signature),
+                                  ED25519_SIGNATURE_LEN));
+  EXPECT_THAT(status.code(), Eq(error::FAILED_PRECONDITION));
+  EXPECT_THAT(status.message(), HasSubstr("Wrong public key size"));
+
+  // Verify the public key - mismatch.
+  public_key_[0] = ~public_key_[0];
+  SignatureVerifier verifier2(std::string(
+      reinterpret_cast<const char*>(public_key_), ED25519_PUBLIC_KEY_LEN));
+  status =
+      verifier2.Verify(std::string(message, strlen(message)),
+                       std::string(reinterpret_cast<const char*>(signature),
+                                   ED25519_SIGNATURE_LEN));
+  EXPECT_THAT(status.code(), Eq(error::INVALID_ARGUMENT));
+  EXPECT_THAT(status.message(), HasSubstr("Verification failed"));
+}
+
+}  // namespace
+}  // namespace reporting

chrome/test/BUILD.gn

@@ -3659,6 +3659,7 @@ test("unit_tests") {
     "../browser/policy/messaging_layer/encryption/encryption_unittest.cc",
     "../browser/policy/messaging_layer/encryption/test_encryption_module.cc",
     "../browser/policy/messaging_layer/encryption/test_encryption_module.h",
+    "../browser/policy/messaging_layer/encryption/verification_unittest.cc",
     "../browser/policy/messaging_layer/public/report_client_unittest.cc",
     "../browser/policy/messaging_layer/public/report_queue_configuration_unittest.cc",
     "../browser/policy/messaging_layer/public/report_queue_unittest.cc",