| /* |
| * Copyright (C) 2018 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.v3; |
| |
| import static com.android.apksig.internal.apk.ApkSigningBlockUtils.getLengthPrefixedSlice; |
| import static com.android.apksig.internal.apk.ApkSigningBlockUtils.readLengthPrefixedByteArray; |
| |
| import com.android.apksig.ApkVerifier.Issue; |
| import com.android.apksig.SigningCertificateLineage; |
| 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.ApkSigningBlockUtils.SignatureNotFoundException; |
| 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.AndroidSdkVersion; |
| 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.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.Set; |
| import java.util.SortedMap; |
| import java.util.TreeMap; |
| |
| /** |
| * APK Signature Scheme v3 verifier. |
| * |
| * <p>APK Signature Scheme v3, like 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 V3SchemeVerifier { |
| |
| private static final int APK_SIGNATURE_SCHEME_V3_BLOCK_ID = 0xf05368c0; |
| |
| /** Hidden constructor to prevent instantiation. */ |
| private V3SchemeVerifier() {} |
| |
| /** |
| * Verifies the provided APK's APK Signature Scheme v3 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 v3 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 SignatureNotFoundException if no APK Signature Scheme v3 |
| * 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, |
| int minSdkVersion, |
| int maxSdkVersion) |
| throws IOException, NoSuchAlgorithmException, SignatureNotFoundException { |
| ApkSigningBlockUtils.Result result = new ApkSigningBlockUtils.Result( |
| ApkSigningBlockUtils.VERSION_APK_SIGNATURE_SCHEME_V3); |
| SignatureInfo signatureInfo = |
| ApkSigningBlockUtils.findSignature(apk, zipSections, |
| APK_SIGNATURE_SCHEME_V3_BLOCK_ID, result); |
| |
| DataSource beforeApkSigningBlock = apk.slice(0, signatureInfo.apkSigningBlockOffset); |
| DataSource centralDir = |
| apk.slice( |
| signatureInfo.centralDirOffset, |
| signatureInfo.eocdOffset - signatureInfo.centralDirOffset); |
| ByteBuffer eocd = signatureInfo.eocd; |
| |
| // v3 didn't exist prior to P, so make sure that we're only judging v3 on its supported |
| // platforms |
| if (minSdkVersion < AndroidSdkVersion.P) { |
| minSdkVersion = AndroidSdkVersion.P; |
| } |
| |
| verify(executor, |
| beforeApkSigningBlock, |
| signatureInfo.signatureBlock, |
| centralDir, |
| eocd, |
| minSdkVersion, |
| maxSdkVersion, |
| result); |
| return result; |
| } |
| |
| /** |
| * Verifies the provided APK's v3 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, 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 apkSignatureSchemeV3Block, |
| DataSource centralDir, |
| ByteBuffer eocd, |
| int minSdkVersion, |
| int maxSdkVersion, |
| ApkSigningBlockUtils.Result result) |
| throws IOException, NoSuchAlgorithmException { |
| Set<ContentDigestAlgorithm> contentDigestsToVerify = new HashSet<>(1); |
| parseSigners(apkSignatureSchemeV3Block, contentDigestsToVerify, result); |
| |
| if (result.containsErrors()) { |
| return; |
| } |
| ApkSigningBlockUtils.verifyIntegrity( |
| executor, beforeApkSigningBlock, centralDir, eocd, contentDigestsToVerify, result); |
| |
| // make sure that the v3 signers cover the entire targeted sdk version ranges and that the |
| // longest SigningCertificateHistory, if present, corresponds to the newest platform |
| // versions |
| SortedMap<Integer, ApkSigningBlockUtils.Result.SignerInfo> sortedSigners = new TreeMap<>(); |
| for (ApkSigningBlockUtils.Result.SignerInfo signer : result.signers) { |
| sortedSigners.put(signer.minSdkVersion, signer); |
| } |
| |
| // first make sure there is neither overlap nor holes |
| int firstMin = 0; |
| int lastMax = 0; |
| int lastLineageSize = 0; |
| |
| // while we're iterating through the signers, build up the list of lineages |
| List<SigningCertificateLineage> lineages = new ArrayList<>(result.signers.size()); |
| |
| for (ApkSigningBlockUtils.Result.SignerInfo signer : sortedSigners.values()) { |
| int currentMin = signer.minSdkVersion; |
| int currentMax = signer.maxSdkVersion; |
| if (firstMin == 0) { |
| // first round sets up our basis |
| firstMin = currentMin; |
| } else { |
| if (currentMin != lastMax + 1) { |
| result.addError(Issue.V3_INCONSISTENT_SDK_VERSIONS); |
| break; |
| } |
| } |
| lastMax = currentMax; |
| |
| // also, while we're here, make sure that the lineage sizes only increase |
| if (signer.signingCertificateLineage != null) { |
| int currLineageSize = signer.signingCertificateLineage.size(); |
| if (currLineageSize < lastLineageSize) { |
| result.addError(Issue.V3_INCONSISTENT_LINEAGES); |
| break; |
| } |
| lastLineageSize = currLineageSize; |
| lineages.add(signer.signingCertificateLineage); |
| } |
| } |
| |
| // make sure we support our desired sdk ranges |
| if (firstMin > minSdkVersion || lastMax < maxSdkVersion) { |
| result.addError(Issue.V3_MISSING_SDK_VERSIONS, firstMin, lastMax); |
| } |
| |
| try { |
| result.signingCertificateLineage = |
| SigningCertificateLineage.consolidateLineages(lineages); |
| } catch (IllegalArgumentException e) { |
| result.addError(Issue.V3_INCONSISTENT_LINEAGES); |
| } |
| if (!result.containsErrors()) { |
| result.verified = true; |
| } |
| } |
| |
| /** |
| * Parses each signer in the provided APK Signature Scheme v3 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 apkSignatureSchemeV3Block, |
| Set<ContentDigestAlgorithm> contentDigestsToVerify, |
| ApkSigningBlockUtils.Result result) throws NoSuchAlgorithmException { |
| ByteBuffer signers; |
| try { |
| signers = getLengthPrefixedSlice(apkSignatureSchemeV3Block); |
| } catch (ApkFormatException e) { |
| result.addError(Issue.V3_SIG_MALFORMED_SIGNERS); |
| return; |
| } |
| if (!signers.hasRemaining()) { |
| result.addError(Issue.V3_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 = getLengthPrefixedSlice(signers); |
| parseSigner(signer, certFactory, signerInfo, contentDigestsToVerify); |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| signerInfo.addError(Issue.V3_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, as well as |
| * the data contained therein, 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) |
| throws ApkFormatException, NoSuchAlgorithmException { |
| ByteBuffer signedData = getLengthPrefixedSlice(signerBlock); |
| byte[] signedDataBytes = new byte[signedData.remaining()]; |
| signedData.get(signedDataBytes); |
| signedData.flip(); |
| result.signedData = signedDataBytes; |
| |
| int parsedMinSdkVersion = signerBlock.getInt(); |
| int parsedMaxSdkVersion = signerBlock.getInt(); |
| result.minSdkVersion = parsedMinSdkVersion; |
| result.maxSdkVersion = parsedMaxSdkVersion; |
| if (parsedMinSdkVersion < 0 || parsedMinSdkVersion > parsedMaxSdkVersion) { |
| result.addError( |
| Issue.V3_SIG_INVALID_SDK_VERSIONS, parsedMinSdkVersion, parsedMaxSdkVersion); |
| } |
| ByteBuffer signatures = getLengthPrefixedSlice(signerBlock); |
| byte[] publicKeyBytes = 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 = getLengthPrefixedSlice(signatures); |
| int sigAlgorithmId = signature.getInt(); |
| byte[] sigBytes = readLengthPrefixedByteArray(signature); |
| result.signatures.add( |
| new ApkSigningBlockUtils.Result.SignerInfo.Signature( |
| sigAlgorithmId, sigBytes)); |
| SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.findById(sigAlgorithmId); |
| if (signatureAlgorithm == null) { |
| result.addWarning(Issue.V3_SIG_UNKNOWN_SIG_ALGORITHM, sigAlgorithmId); |
| continue; |
| } |
| // TODO consider dropping deprecated signatures for v3 or modifying |
| // getSignaturesToVerify (called below) |
| supportedSignatures.add( |
| new ApkSigningBlockUtils.SupportedSignature(signatureAlgorithm, sigBytes)); |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| result.addError(Issue.V3_SIG_MALFORMED_SIGNATURE, signatureCount); |
| return; |
| } |
| } |
| if (result.signatures.isEmpty()) { |
| result.addError(Issue.V3_SIG_NO_SIGNATURES); |
| return; |
| } |
| |
| // Verify signatures over signed-data block using the public key |
| List<ApkSigningBlockUtils.SupportedSignature> signaturesToVerify = null; |
| try { |
| signaturesToVerify = |
| ApkSigningBlockUtils.getSignaturesToVerify( |
| supportedSignatures, result.minSdkVersion, result.maxSdkVersion); |
| } catch (ApkSigningBlockUtils.NoSupportedSignaturesException e) { |
| result.addError(Issue.V3_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.V3_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.V3_SIG_DID_NOT_VERIFY, signatureAlgorithm); |
| return; |
| } |
| result.verifiedSignatures.put(signatureAlgorithm, sigBytes); |
| contentDigestsToVerify.add(signatureAlgorithm.getContentDigestAlgorithm()); |
| } catch (InvalidKeyException | InvalidAlgorithmParameterException |
| | SignatureException e) { |
| result.addError(Issue.V3_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 = getLengthPrefixedSlice(signedData); |
| ByteBuffer certificates = getLengthPrefixedSlice(signedData); |
| |
| int signedMinSdkVersion = signedData.getInt(); |
| if (signedMinSdkVersion != parsedMinSdkVersion) { |
| result.addError( |
| Issue.V3_MIN_SDK_VERSION_MISMATCH_BETWEEN_SIGNER_AND_SIGNED_DATA_RECORD, |
| parsedMinSdkVersion, |
| signedMinSdkVersion); |
| } |
| int signedMaxSdkVersion = signedData.getInt(); |
| if (signedMaxSdkVersion != parsedMaxSdkVersion) { |
| result.addError( |
| Issue.V3_MAX_SDK_VERSION_MISMATCH_BETWEEN_SIGNER_AND_SIGNED_DATA_RECORD, |
| parsedMaxSdkVersion, |
| signedMaxSdkVersion); |
| } |
| ByteBuffer additionalAttributes = getLengthPrefixedSlice(signedData); |
| |
| // Parse the certificates block |
| int certificateIndex = -1; |
| while (certificates.hasRemaining()) { |
| certificateIndex++; |
| byte[] encodedCert = readLengthPrefixedByteArray(certificates); |
| X509Certificate certificate; |
| try { |
| certificate = X509CertificateUtils.generateCertificate(encodedCert, certFactory); |
| } catch (CertificateException e) { |
| result.addError( |
| Issue.V3_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.V3_SIG_NO_CERTIFICATES); |
| return; |
| } |
| X509Certificate mainCertificate = result.certs.get(0); |
| byte[] certificatePublicKeyBytes = mainCertificate.getPublicKey().getEncoded(); |
| if (!Arrays.equals(publicKeyBytes, certificatePublicKeyBytes)) { |
| result.addError( |
| Issue.V3_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 = getLengthPrefixedSlice(digests); |
| int sigAlgorithmId = digest.getInt(); |
| byte[] digestBytes = readLengthPrefixedByteArray(digest); |
| result.contentDigests.add( |
| new ApkSigningBlockUtils.Result.SignerInfo.ContentDigest( |
| sigAlgorithmId, digestBytes)); |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| result.addError(Issue.V3_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.V3_SIG_SIG_ALG_MISMATCH_BETWEEN_SIGNATURES_AND_DIGESTS_RECORDS, |
| sigAlgsFromSignaturesRecord, |
| sigAlgsFromDigestsRecord); |
| return; |
| } |
| |
| // Parse the additional attributes block. |
| int additionalAttributeCount = 0; |
| while (additionalAttributes.hasRemaining()) { |
| additionalAttributeCount++; |
| try { |
| ByteBuffer attribute = |
| getLengthPrefixedSlice(additionalAttributes); |
| int id = attribute.getInt(); |
| byte[] value = ByteBufferUtils.toByteArray(attribute); |
| result.additionalAttributes.add( |
| new ApkSigningBlockUtils.Result.SignerInfo.AdditionalAttribute(id, value)); |
| if (id == V3SchemeSigner.PROOF_OF_ROTATION_ATTR_ID) { |
| try { |
| // SigningCertificateLineage is verified when built |
| result.signingCertificateLineage = |
| SigningCertificateLineage.readFromV3AttributeValue(value); |
| // make sure that the last cert in the chain matches this signer cert |
| SigningCertificateLineage subLineage = |
| result.signingCertificateLineage.getSubLineage(result.certs.get(0)); |
| if (result.signingCertificateLineage.size() != subLineage.size()) { |
| result.addError(Issue.V3_SIG_POR_CERT_MISMATCH); |
| } |
| } catch (SecurityException e) { |
| result.addError(Issue.V3_SIG_POR_DID_NOT_VERIFY); |
| } catch (IllegalArgumentException e) { |
| result.addError(Issue.V3_SIG_POR_CERT_MISMATCH); |
| } catch (Exception e) { |
| result.addError(Issue.V3_SIG_MALFORMED_LINEAGE); |
| } |
| } else { |
| result.addWarning(Issue.V3_SIG_UNKNOWN_ADDITIONAL_ATTRIBUTE, id); |
| } |
| } catch (ApkFormatException | BufferUnderflowException e) { |
| result.addError( |
| Issue.V3_SIG_MALFORMED_ADDITIONAL_ATTRIBUTE, additionalAttributeCount); |
| return; |
| } |
| } |
| } |
| |
| } |
