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fix(gcpkms): verify ciphertext_crc32c and AAD_crc32c on Decrypt response #5

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fix(gcpkms): verify ciphertext_crc32c and AAD_crc32c on Decrypt response #5

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24 changes: 24 additions & 0 deletions src/main/java/com/google/crypto/tink/integration/gcpkms/GcpKmsAead.java
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,19 @@ public byte[] decrypt(final byte[] ciphertext, final byte[] associatedData)
.decrypt(this.keyName, request)
.execute();

// Verify the server confirmed it received the request CRCs intact;
// see https://cloud.google.com/kms/docs/data-integrity-guidelines.
if (response.getVerifiedCiphertextCrc32c() == null
|| !response.getVerifiedCiphertextCrc32c()) {
throw new GeneralSecurityException(
"Verifying the provided ciphertext checksum failed.");
}
if (response.getVerifiedAdditionalAuthenticatedDataCrc32c() == null
|| !response.getVerifiedAdditionalAuthenticatedDataCrc32c()) {
throw new GeneralSecurityException(
"Verifying the provided associated data checksum failed.");
}

byte[] plaintext = toNonNullableByteArray(response.decodePlaintext());
long plaintextCrc32c = Hashing.crc32c().hashBytes(plaintext).padToLong();
if (response.getPlaintextCrc32c() != plaintextCrc32c) {
Expand Down Expand Up @@ -248,6 +261,17 @@ public byte[] decrypt(final byte[] ciphertext, final byte[] associatedData)

com.google.cloud.kms.v1.DecryptResponse decResponse = kmsClient.decrypt(decryptRequest);

// Verify the server confirmed it received the request CRCs intact;
// see https://cloud.google.com/kms/docs/data-integrity-guidelines.
if (!decResponse.getVerifiedCiphertextCrc32C()) {
throw new GeneralSecurityException(
"Verifying the provided ciphertext checksum failed.");
}
if (!decResponse.getVerifiedAdditionalAuthenticatedDataCrc32C()) {
throw new GeneralSecurityException(
"Verifying the provided associated data checksum failed.");
}

byte[] plaintext = decResponse.getPlaintext().toByteArray();

long plaintextCrc = Hashing.crc32c().hashBytes(plaintext).padToLong();
Expand Down