1 /* 2 * Copyright (C) 2023 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.adservices.service.adselection.signature; 18 19 import android.annotation.NonNull; 20 21 import com.android.adservices.LoggerFactory; 22 import com.android.adservices.service.stats.SignatureVerificationLogger; 23 24 import com.google.common.annotations.VisibleForTesting; 25 26 import java.security.InvalidKeyException; 27 import java.security.KeyFactory; 28 import java.security.PublicKey; 29 import java.security.Signature; 30 import java.security.SignatureException; 31 import java.security.spec.InvalidKeySpecException; 32 import java.security.spec.X509EncodedKeySpec; 33 import java.util.Objects; 34 35 /** Verifies signatures using ECDSA algorithm (aka. ECDSAwithSHA256). */ 36 public class ECDSASignatureVerifier implements SignatureVerifier { 37 private static final LoggerFactory.Logger sLogger = LoggerFactory.getFledgeLogger(); 38 39 @VisibleForTesting 40 protected static final String UNKNOWN_ERROR = 41 "An unknown error occurred during signature verification"; 42 43 @VisibleForTesting 44 protected static final String INVALID_KEY_ERROR = 45 "Given key is either null or not suitable with the specified algorithm: ECDSA"; 46 47 @VisibleForTesting 48 protected static final String SIGNATURE_VALIDATION_ERROR = 49 "Encounter error during signature verification"; 50 51 @VisibleForTesting protected static final String EC_KEY_ALGORITHM = "EC"; 52 53 @VisibleForTesting 54 protected static final String ECDSA_WITH_SHA256_SIGNING_ALGORITHM = "SHA256withECDSA"; 55 56 @NonNull private final SignatureVerificationLogger mSignatureVerificationLogger; 57 ECDSASignatureVerifier( @onNull SignatureVerificationLogger signatureVerificationLogger)58 public ECDSASignatureVerifier( 59 @NonNull SignatureVerificationLogger signatureVerificationLogger) { 60 Objects.requireNonNull(signatureVerificationLogger); 61 62 mSignatureVerificationLogger = signatureVerificationLogger; 63 } 64 65 /** 66 * Verifies a given signature against the given public key and the serialized data. 67 * 68 * <p>Verifies the signature created by ECDSAwithSHA256 algorithm 69 * 70 * @param publicKey public key paired with the private key used to sign the data 71 * @param data serialized representation of the data 72 * @param signature signature to verify 73 */ 74 @Override verify(byte[] publicKey, byte[] data, byte[] signature)75 public boolean verify(byte[] publicKey, byte[] data, byte[] signature) { 76 try { 77 KeyFactory keyFactory = KeyFactory.getInstance(EC_KEY_ALGORITHM); 78 X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKey); 79 PublicKey aPublicKey = keyFactory.generatePublic(keySpec); 80 // TODO(b/311368820): Make this singleton to avoid initializing it every time 81 Signature ecdsa = Signature.getInstance(ECDSA_WITH_SHA256_SIGNING_ALGORITHM); 82 ecdsa.initVerify(aPublicKey); 83 ecdsa.update(data); 84 return ecdsa.verify(signature); 85 } catch (InvalidKeySpecException | InvalidKeyException | NullPointerException error) { 86 sLogger.e(error, INVALID_KEY_ERROR); 87 logWrongKeyFormatError(); 88 return false; 89 } catch (SignatureException error) { 90 sLogger.e(error, SIGNATURE_VALIDATION_ERROR); 91 logSignatureFormatError(); 92 return false; 93 } catch (Exception error) { 94 sLogger.e(error, UNKNOWN_ERROR); 95 logUnknownError(); 96 return false; 97 } 98 } 99 logWrongKeyFormatError()100 private void logWrongKeyFormatError() { 101 mSignatureVerificationLogger.addFailureDetailCountOfKeysWithWrongFormat(); 102 } 103 logSignatureFormatError()104 private void logSignatureFormatError() { 105 mSignatureVerificationLogger.setFailureDetailWrongSignatureFormat(); 106 } 107 logUnknownError()108 private void logUnknownError() { 109 mSignatureVerificationLogger.setFailureDetailUnknownError(); 110 } 111 } 112