| /* |
| * Copyright (C) 2016 The Android Open Source Project |
| * |
| * 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. |
| */ |
| |
| package com.android.apksig.internal.apk.v2; |
| |
| import com.android.apksig.ApkVerifier.Issue; |
| import com.android.apksig.apk.ApkFormatException; |
| import com.android.apksig.apk.ApkUtils; |
| import com.android.apksig.internal.apk.ApkSigningBlockUtils; |
| import com.android.apksig.internal.apk.ContentDigestAlgorithm; |
| import com.android.apksig.internal.apk.SignatureAlgorithm; |
| import com.android.apksig.internal.apk.SignatureInfo; |
| import com.android.apksig.internal.util.ByteBufferUtils; |
| import com.android.apksig.internal.util.X509CertificateUtils; |
| import com.android.apksig.internal.util.GuaranteedEncodedFormX509Certificate; |
| import com.android.apksig.util.DataSource; |
| import com.android.apksig.util.RunnablesExecutor; |
| import java.io.IOException; |
| import java.nio.BufferUnderflowException; |
| import java.nio.ByteBuffer; |
| import java.nio.ByteOrder; |
| import java.security.InvalidAlgorithmParameterException; |
| import java.security.InvalidKeyException; |
| import java.security.KeyFactory; |
| import java.security.NoSuchAlgorithmException; |
| import java.security.PublicKey; |
| import java.security.Signature; |
| import java.security.SignatureException; |
| import java.security.cert.CertificateException; |
| import java.security.cert.CertificateFactory; |
| import java.security.cert.X509Certificate; |
| import java.security.spec.AlgorithmParameterSpec; |
| import java.security.spec.X509EncodedKeySpec; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * APK Signature Scheme v2 verifier. |
| * |
| * <p>APK Signature Scheme v2 is a whole-file signature scheme which aims to protect every single |
| * bit of the APK, as opposed to the JAR Signature Scheme which protects only the names and |
| * uncompressed contents of ZIP entries. |
| * |
| * @see <a href="https://source.android.com/security/apksigning/v2.html">APK Signature Scheme v2</a> |
| */ |
| public abstract class V2SchemeVerifier { |
| |
| private static final int APK_SIGNATURE_SCHEME_V2_BLOCK_ID = 0x7109871a; |
| |
| /** Hidden constructor to prevent instantiation. */ |
| private V2SchemeVerifier() {} |
| |
| /** |
| * Verifies the provided APK's APK Signature Scheme v2 signatures and returns the result of |
| * verification. The APK must be considered verified only if |
| * {@link ApkSigningBlockUtils.Result#verified} is |
| * {@code true}. If verification fails, the result will contain errors -- see |
| * {@link ApkSigningBlockUtils.Result#getErrors()}. |
| * |
| * <p>Verification succeeds iff the APK's APK Signature Scheme v2 signatures are expected to |
| * verify on all Android platform versions in the {@code [minSdkVersion, maxSdkVersion]} range. |
| * If the APK's signature is expected to not verify on any of the specified platform versions, |
| * this method returns a result with one or more errors and whose |
| * {@code Result.verified == false}, or this method throws an exception. |
| * |
| * @throws ApkFormatException if the APK is malformed |
| * @throws NoSuchAlgorithmException if the APK's signatures cannot be verified because a |
| * required cryptographic algorithm implementation is missing |
| * @throws ApkSigningBlockUtils.SignatureNotFoundException if no APK Signature Scheme v2 |
| * signatures are found |
| * @throws IOException if an I/O error occurs when reading the APK |
| */ |
| public static ApkSigningBlockUtils.Result verify( |
| RunnablesExecutor executor, |
| DataSource apk, |
| ApkUtils.ZipSections zipSections, |
| Map<Integer, String> supportedApkSigSchemeNames, |
| Set<Integer> foundSigSchemeIds, |
| int minSdkVersion, |
| int maxSdkVersion) |
| throws IOException, ApkFormatException, NoSuchAlgorithmException, |
| ApkSigningBlockUtils.SignatureNotFoundException { |
| ApkSigningBlockUtils.Result result = new ApkSigningBlockUtils.Result( |
| ApkSigningBlockUtils.VERSION_APK_SIGNATURE_SCHEME_V2); |
| SignatureInfo signatureInfo = |
| ApkSigningBlockUtils.findSignature(apk, zipSections, |
| APK_SIGNATURE_SCHEME_V2_BLOCK_ID , result); |
| |
| DataSource beforeApkSigningBlock = apk.slice(0, signatureInfo.apkSigningBlockOffset); |
| DataSource centralDir = |
| apk.slice( |
| signatureInfo.centralDirOffset, |
| signatureInfo.eocdOffset - signatureInfo.centralDirOffset); |
| ByteBuffer eocd = signatureInfo.eocd; |
| |
| verify(executor, |
| beforeApkSigningBlock, |
| signatureInfo.signatureBlock, |
| centralDir, |
| eocd, |
| supportedApkSigSchemeNames, |
| foundSigSchemeIds, |
| minSdkVersion, |
| maxSdkVersion, |
| result); |
| return result; |
| } |
| |
| /** |
| * Verifies the provided APK's v2 signatures and outputs the results into the provided |
| * {@code result}. APK is considered verified only if there are no errors reported in the |
| * {@code result}. See {@link #verify(RunnablesExecutor, DataSource, ApkUtils.ZipSections, Map, |
| * Set, int, int)} for more information about the contract of this method. |
| * |
| * @param result result populated by this method with interesting information about the APK, |
| * such as information about signers, and verification errors and warnings. |
| */ |
| private static void verify( |
| RunnablesExecutor executor, |
| DataSource beforeApkSigningBlock, |
| ByteBuffer apkSignatureSchemeV2Block, |
| DataSource centralDir, |
| ByteBuffer eocd, |
| Map<Integer, String> supportedApkSigSchemeNames, |
| Set<Integer> foundSigSchemeIds, |
| int minSdkVersion, |
| int maxSdkVersion, |
| ApkSigningBlockUtils.Result result) |
| throws IOException, NoSuchAlgorithmException { |
| Set<ContentDigestAlgorithm> contentDigestsToVerify = new HashSet<>(1); |
| parseSigners( |
| apkSignatureSchemeV2Block, |
| contentDigestsToVerify, |
| supportedApkSigSchemeNames, |
| foundSigSchemeIds, |
| minSdkVersion, |
| maxSdkVersion, |
| result); |
| if (result.containsErrors()) { |
| return; |
| } |
| ApkSigningBlockUtils.verifyIntegrity( |
| executor, beforeApkSigningBlock, centralDir, eocd, contentDigestsToVerify, result); |
| if (!result.containsErrors()) { |
| result.verified = true; |
| } |
| } |
| |
| /** |
| * Parses each signer in the provided APK Signature Scheme v2 block and populates corresponding |
| * {@code signerInfos} of the provided {@code result}. |
| * |
| * <p>This verifies signatures over {@code signed-data} block contained in each signer block. |
| * However, this does not verify the integrity of the rest of the APK but rather simply reports |
| * the expected digests of the rest of the APK (see {@code contentDigestsToVerify}). |
| * |
| * <p>This method adds one or more errors to the {@code result} if a verification error is |
| * expected to be encountered on an Android platform version in the |
| * {@code [minSdkVersion, maxSdkVersion]} range. |
| */ |
| private static void parseSigners( |
| ByteBuffer apkSignatureSchemeV2Block, |
| Set<ContentDigestAlgorithm> contentDigestsToVerify, |
| Map<Integer, String> supportedApkSigSchemeNames, |
| Set<Integer> foundApkSigSchemeIds, |
| int minSdkVersion, |
| int maxSdkVersion, |
| ApkSigningBlockUtils.Result result) throws NoSuchAlgorithmException { |
| ByteBuffer signers; |
| try { |
| signers = ApkSigningBlockUtils.getLengthPrefixedSlice(apkSignatureSchemeV2Block); |
| } catch (ApkFormatException e) { |
| result.addError(Issue.V2_SIG_MALFORMED_SIGNERS); |
| return; |
| } |
| if (!signers.hasRemaining()) { |
| result.addError(Issue.V2_SIG_NO_SIGNERS); |
| return; |
| } |
| |
| CertificateFactory certFactory; |
| try { |
| certFactory = CertificateFactory.getInstance("X.509"); |
| } catch (CertificateException e) { |
| throw new RuntimeException("Failed to obtain X.509 CertificateFactory", e); |
| } |
| int signerCount = 0; |
| while (signers.hasRemaining()) { |
| int signerIndex = signerCount; |
| signerCount++; |
| ApkSigningBlockUtils.Result.SignerInfo signerInfo = |
| new ApkSigningBlockUtils.Result.SignerInfo(); |
| signerInfo.index = signerIndex; |
| result.signers.add(signerInfo); |
| try { |
| ByteBuffer signer = ApkSigningBlockUtils.getLengthPrefixedSlice(signers); |
| parseSigner( |
| signer, |
| certFactory, |
| signerInfo, |
| contentDigestsToVerify, |
| supportedApkSigSchemeNames, |
| foundApkSigSchemeIds, |
| minSdkVersion, |
| maxSdkVersion); |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| signerInfo.addError(Issue.V2_SIG_MALFORMED_SIGNER); |
| return; |
| } |
| } |
| } |
| |
| /** |
| * Parses the provided signer block and populates the {@code result}. |
| * |
| * <p>This verifies signatures over {@code signed-data} contained in this block but does not |
| * verify the integrity of the rest of the APK. To facilitate APK integrity verification, this |
| * method adds the {@code contentDigestsToVerify}. These digests can then be used to verify the |
| * integrity of the APK. |
| * |
| * <p>This method adds one or more errors to the {@code result} if a verification error is |
| * expected to be encountered on an Android platform version in the |
| * {@code [minSdkVersion, maxSdkVersion]} range. |
| */ |
| private static void parseSigner( |
| ByteBuffer signerBlock, |
| CertificateFactory certFactory, |
| ApkSigningBlockUtils.Result.SignerInfo result, |
| Set<ContentDigestAlgorithm> contentDigestsToVerify, |
| Map<Integer, String> supportedApkSigSchemeNames, |
| Set<Integer> foundApkSigSchemeIds, |
| int minSdkVersion, |
| int maxSdkVersion) |
| throws ApkFormatException, NoSuchAlgorithmException { |
| ByteBuffer signedData = ApkSigningBlockUtils.getLengthPrefixedSlice(signerBlock); |
| byte[] signedDataBytes = new byte[signedData.remaining()]; |
| signedData.get(signedDataBytes); |
| signedData.flip(); |
| result.signedData = signedDataBytes; |
| |
| ByteBuffer signatures = ApkSigningBlockUtils.getLengthPrefixedSlice(signerBlock); |
| byte[] publicKeyBytes = ApkSigningBlockUtils.readLengthPrefixedByteArray(signerBlock); |
| |
| // Parse the signatures block and identify supported signatures |
| int signatureCount = 0; |
| List<ApkSigningBlockUtils.SupportedSignature> supportedSignatures = new ArrayList<>(1); |
| while (signatures.hasRemaining()) { |
| signatureCount++; |
| try { |
| ByteBuffer signature = ApkSigningBlockUtils.getLengthPrefixedSlice(signatures); |
| int sigAlgorithmId = signature.getInt(); |
| byte[] sigBytes = ApkSigningBlockUtils.readLengthPrefixedByteArray(signature); |
| result.signatures.add( |
| new ApkSigningBlockUtils.Result.SignerInfo.Signature( |
| sigAlgorithmId, sigBytes)); |
| SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.findById(sigAlgorithmId); |
| if (signatureAlgorithm == null) { |
| result.addWarning(Issue.V2_SIG_UNKNOWN_SIG_ALGORITHM, sigAlgorithmId); |
| continue; |
| } |
| supportedSignatures.add( |
| new ApkSigningBlockUtils.SupportedSignature(signatureAlgorithm, sigBytes)); |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| result.addError(Issue.V2_SIG_MALFORMED_SIGNATURE, signatureCount); |
| return; |
| } |
| } |
| if (result.signatures.isEmpty()) { |
| result.addError(Issue.V2_SIG_NO_SIGNATURES); |
| return; |
| } |
| |
| // Verify signatures over signed-data block using the public key |
| List<ApkSigningBlockUtils.SupportedSignature> signaturesToVerify = null; |
| try { |
| signaturesToVerify = |
| ApkSigningBlockUtils.getSignaturesToVerify( |
| supportedSignatures, minSdkVersion, maxSdkVersion); |
| } catch (ApkSigningBlockUtils.NoSupportedSignaturesException e) { |
| result.addError(Issue.V2_SIG_NO_SUPPORTED_SIGNATURES); |
| return; |
| } |
| for (ApkSigningBlockUtils.SupportedSignature signature : signaturesToVerify) { |
| SignatureAlgorithm signatureAlgorithm = signature.algorithm; |
| String jcaSignatureAlgorithm = |
| signatureAlgorithm.getJcaSignatureAlgorithmAndParams().getFirst(); |
| AlgorithmParameterSpec jcaSignatureAlgorithmParams = |
| signatureAlgorithm.getJcaSignatureAlgorithmAndParams().getSecond(); |
| String keyAlgorithm = signatureAlgorithm.getJcaKeyAlgorithm(); |
| PublicKey publicKey; |
| try { |
| publicKey = |
| KeyFactory.getInstance(keyAlgorithm).generatePublic( |
| new X509EncodedKeySpec(publicKeyBytes)); |
| } catch (Exception e) { |
| result.addError(Issue.V2_SIG_MALFORMED_PUBLIC_KEY, e); |
| return; |
| } |
| try { |
| Signature sig = Signature.getInstance(jcaSignatureAlgorithm); |
| sig.initVerify(publicKey); |
| if (jcaSignatureAlgorithmParams != null) { |
| sig.setParameter(jcaSignatureAlgorithmParams); |
| } |
| signedData.position(0); |
| sig.update(signedData); |
| byte[] sigBytes = signature.signature; |
| if (!sig.verify(sigBytes)) { |
| result.addError(Issue.V2_SIG_DID_NOT_VERIFY, signatureAlgorithm); |
| return; |
| } |
| result.verifiedSignatures.put(signatureAlgorithm, sigBytes); |
| contentDigestsToVerify.add(signatureAlgorithm.getContentDigestAlgorithm()); |
| } catch (InvalidKeyException | InvalidAlgorithmParameterException |
| | SignatureException e) { |
| result.addError(Issue.V2_SIG_VERIFY_EXCEPTION, signatureAlgorithm, e); |
| return; |
| } |
| } |
| |
| // At least one signature over signedData has verified. We can now parse signed-data. |
| signedData.position(0); |
| ByteBuffer digests = ApkSigningBlockUtils.getLengthPrefixedSlice(signedData); |
| ByteBuffer certificates = ApkSigningBlockUtils.getLengthPrefixedSlice(signedData); |
| ByteBuffer additionalAttributes = ApkSigningBlockUtils.getLengthPrefixedSlice(signedData); |
| |
| // Parse the certificates block |
| int certificateIndex = -1; |
| while (certificates.hasRemaining()) { |
| certificateIndex++; |
| byte[] encodedCert = ApkSigningBlockUtils.readLengthPrefixedByteArray(certificates); |
| X509Certificate certificate; |
| try { |
| certificate = X509CertificateUtils.generateCertificate(encodedCert, certFactory); |
| } catch (CertificateException e) { |
| result.addError( |
| Issue.V2_SIG_MALFORMED_CERTIFICATE, |
| certificateIndex, |
| certificateIndex + 1, |
| e); |
| return; |
| } |
| // Wrap the cert so that the result's getEncoded returns exactly the original encoded |
| // form. Without this, getEncoded may return a different form from what was stored in |
| // the signature. This is because some X509Certificate(Factory) implementations |
| // re-encode certificates. |
| certificate = new GuaranteedEncodedFormX509Certificate(certificate, encodedCert); |
| result.certs.add(certificate); |
| } |
| |
| if (result.certs.isEmpty()) { |
| result.addError(Issue.V2_SIG_NO_CERTIFICATES); |
| return; |
| } |
| X509Certificate mainCertificate = result.certs.get(0); |
| byte[] certificatePublicKeyBytes = mainCertificate.getPublicKey().getEncoded(); |
| if (!Arrays.equals(publicKeyBytes, certificatePublicKeyBytes)) { |
| result.addError( |
| Issue.V2_SIG_PUBLIC_KEY_MISMATCH_BETWEEN_CERTIFICATE_AND_SIGNATURES_RECORD, |
| ApkSigningBlockUtils.toHex(certificatePublicKeyBytes), |
| ApkSigningBlockUtils.toHex(publicKeyBytes)); |
| return; |
| } |
| |
| // Parse the digests block |
| int digestCount = 0; |
| while (digests.hasRemaining()) { |
| digestCount++; |
| try { |
| ByteBuffer digest = ApkSigningBlockUtils.getLengthPrefixedSlice(digests); |
| int sigAlgorithmId = digest.getInt(); |
| byte[] digestBytes = ApkSigningBlockUtils.readLengthPrefixedByteArray(digest); |
| result.contentDigests.add( |
| new ApkSigningBlockUtils.Result.SignerInfo.ContentDigest( |
| sigAlgorithmId, digestBytes)); |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| result.addError(Issue.V2_SIG_MALFORMED_DIGEST, digestCount); |
| return; |
| } |
| } |
| |
| List<Integer> sigAlgsFromSignaturesRecord = new ArrayList<>(result.signatures.size()); |
| for (ApkSigningBlockUtils.Result.SignerInfo.Signature signature : result.signatures) { |
| sigAlgsFromSignaturesRecord.add(signature.getAlgorithmId()); |
| } |
| List<Integer> sigAlgsFromDigestsRecord = new ArrayList<>(result.contentDigests.size()); |
| for (ApkSigningBlockUtils.Result.SignerInfo.ContentDigest digest : result.contentDigests) { |
| sigAlgsFromDigestsRecord.add(digest.getSignatureAlgorithmId()); |
| } |
| |
| if (!sigAlgsFromSignaturesRecord.equals(sigAlgsFromDigestsRecord)) { |
| result.addError( |
| Issue.V2_SIG_SIG_ALG_MISMATCH_BETWEEN_SIGNATURES_AND_DIGESTS_RECORDS, |
| sigAlgsFromSignaturesRecord, |
| sigAlgsFromDigestsRecord); |
| return; |
| } |
| |
| // Parse the additional attributes block. |
| int additionalAttributeCount = 0; |
| Set<Integer> supportedApkSigSchemeIds = supportedApkSigSchemeNames.keySet(); |
| Set<Integer> supportedExpectedApkSigSchemeIds = new HashSet<>(1); |
| while (additionalAttributes.hasRemaining()) { |
| additionalAttributeCount++; |
| try { |
| ByteBuffer attribute = |
| ApkSigningBlockUtils.getLengthPrefixedSlice(additionalAttributes); |
| int id = attribute.getInt(); |
| byte[] value = ByteBufferUtils.toByteArray(attribute); |
| result.additionalAttributes.add( |
| new ApkSigningBlockUtils.Result.SignerInfo.AdditionalAttribute(id, value)); |
| switch (id) { |
| case V2SchemeSigner.STRIPPING_PROTECTION_ATTR_ID: |
| // stripping protection added when signing with a newer scheme |
| int foundId = ByteBuffer.wrap(value).order( |
| ByteOrder.LITTLE_ENDIAN).getInt(); |
| if (supportedApkSigSchemeIds.contains(foundId)) { |
| supportedExpectedApkSigSchemeIds.add(foundId); |
| } else { |
| result.addWarning( |
| Issue.V2_SIG_UNKNOWN_APK_SIG_SCHEME_ID, result.index, foundId); |
| } |
| break; |
| default: |
| result.addWarning(Issue.V2_SIG_UNKNOWN_ADDITIONAL_ATTRIBUTE, id); |
| } |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| result.addError( |
| Issue.V2_SIG_MALFORMED_ADDITIONAL_ATTRIBUTE, additionalAttributeCount); |
| return; |
| } |
| } |
| |
| // make sure that all known IDs indicated in stripping protection have already verified |
| for (int id : supportedExpectedApkSigSchemeIds) { |
| if (!foundApkSigSchemeIds.contains(id)) { |
| String apkSigSchemeName = supportedApkSigSchemeNames.get(id); |
| result.addError( |
| Issue.V2_SIG_MISSING_APK_SIG_REFERENCED, |
| result.index, |
| apkSigSchemeName); |
| } |
| } |
| } |
| } |
