Examples with SignerInfo com.android.apksig.internal.pkcs7.SignerInfo used on opensource projects

Example 1 with SignerInfo

use of com.android.apksig.internal.pkcs7.SignerInfo in project apksig by venshine.

the class ApkSigningBlockUtils method verifyIntegrity.

/**
 * Verifies integrity of the APK outside of the APK Signing Block by computing digests of the
 * APK and comparing them against the digests listed in APK Signing Block. The expected digests
 * are taken from {@code SignerInfos} of the provided {@code result}.
 *
 * <p>This method adds one or more errors to the {@code result} if a verification error is
 * expected to be encountered on Android. No errors are added to the {@code result} if the APK's
 * integrity is expected to verify on Android for each algorithm in
 * {@code contentDigestAlgorithms}.
 *
 * <p>The reason this method is currently not parameterized by a
 * {@code [minSdkVersion, maxSdkVersion]} range is that up until now content digest algorithms
 * exhibit the same behavior on all Android platform versions.
 */
public static void verifyIntegrity(RunnablesExecutor executor, DataSource beforeApkSigningBlock, DataSource centralDir, ByteBuffer eocd, Set<ContentDigestAlgorithm> contentDigestAlgorithms, Result result) throws IOException, NoSuchAlgorithmException {
    if (contentDigestAlgorithms.isEmpty()) {
        // is verified, meaning at least one content digest is known.
        throw new RuntimeException("No content digests found");
    }
    // For the purposes of verifying integrity, ZIP End of Central Directory (EoCD) must be
    // treated as though its Central Directory offset points to the start of APK Signing Block.
    // We thus modify the EoCD accordingly.
    ByteBuffer modifiedEocd = ByteBuffer.allocate(eocd.remaining());
    int eocdSavedPos = eocd.position();
    modifiedEocd.order(ByteOrder.LITTLE_ENDIAN);
    modifiedEocd.put(eocd);
    modifiedEocd.flip();
    // restore eocd to position prior to modification in case it is to be used elsewhere
    eocd.position(eocdSavedPos);
    ZipUtils.setZipEocdCentralDirectoryOffset(modifiedEocd, beforeApkSigningBlock.size());
    Map<ContentDigestAlgorithm, byte[]> actualContentDigests;
    try {
        actualContentDigests = computeContentDigests(executor, contentDigestAlgorithms, beforeApkSigningBlock, centralDir, new ByteBufferDataSource(modifiedEocd));
        // Special checks for the verity algorithm requirements.
        if (actualContentDigests.containsKey(VERITY_CHUNKED_SHA256)) {
            if ((beforeApkSigningBlock.size() % ANDROID_COMMON_PAGE_ALIGNMENT_BYTES != 0)) {
                throw new RuntimeException("APK Signing Block is not aligned on 4k boundary: " + beforeApkSigningBlock.size());
            }
            long centralDirOffset = ZipUtils.getZipEocdCentralDirectoryOffset(eocd);
            long signingBlockSize = centralDirOffset - beforeApkSigningBlock.size();
            if (signingBlockSize % ANDROID_COMMON_PAGE_ALIGNMENT_BYTES != 0) {
                throw new RuntimeException("APK Signing Block size is not multiple of page size: " + signingBlockSize);
            }
        }
    } catch (DigestException e) {
        throw new RuntimeException("Failed to compute content digests", e);
    }
    if (!contentDigestAlgorithms.equals(actualContentDigests.keySet())) {
        throw new RuntimeException("Mismatch between sets of requested and computed content digests" + " . Requested: " + contentDigestAlgorithms + ", computed: " + actualContentDigests.keySet());
    }
    // in signer blocks.
    for (Result.SignerInfo signerInfo : result.signers) {
        for (Result.SignerInfo.ContentDigest expected : signerInfo.contentDigests) {
            SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.findById(expected.getSignatureAlgorithmId());
            if (signatureAlgorithm == null) {
                continue;
            }
            ContentDigestAlgorithm contentDigestAlgorithm = signatureAlgorithm.getContentDigestAlgorithm();
            // range.
            if (!contentDigestAlgorithms.contains(contentDigestAlgorithm)) {
                continue;
            }
            byte[] expectedDigest = expected.getValue();
            byte[] actualDigest = actualContentDigests.get(contentDigestAlgorithm);
            if (!Arrays.equals(expectedDigest, actualDigest)) {
                if (result.signatureSchemeVersion == VERSION_APK_SIGNATURE_SCHEME_V2) {
                    signerInfo.addError(ApkVerifier.Issue.V2_SIG_APK_DIGEST_DID_NOT_VERIFY, contentDigestAlgorithm, toHex(expectedDigest), toHex(actualDigest));
                } else if (result.signatureSchemeVersion == VERSION_APK_SIGNATURE_SCHEME_V3) {
                    signerInfo.addError(ApkVerifier.Issue.V3_SIG_APK_DIGEST_DID_NOT_VERIFY, contentDigestAlgorithm, toHex(expectedDigest), toHex(actualDigest));
                }
                continue;
            }
            signerInfo.verifiedContentDigests.put(contentDigestAlgorithm, actualDigest);
        }
    }
}

Example 2 with SignerInfo

use of com.android.apksig.internal.pkcs7.SignerInfo in project android_frameworks_base by ParanoidAndroid.

the class RecoverySystem method verifyPackage.

/**
     * Verify the cryptographic signature of a system update package
     * before installing it.  Note that the package is also verified
     * separately by the installer once the device is rebooted into
     * the recovery system.  This function will return only if the
     * package was successfully verified; otherwise it will throw an
     * exception.
     *
     * Verification of a package can take significant time, so this
     * function should not be called from a UI thread.  Interrupting
     * the thread while this function is in progress will result in a
     * SecurityException being thrown (and the thread's interrupt flag
     * will be cleared).
     *
     * @param packageFile  the package to be verified
     * @param listener     an object to receive periodic progress
     * updates as verification proceeds.  May be null.
     * @param deviceCertsZipFile  the zip file of certificates whose
     * public keys we will accept.  Verification succeeds if the
     * package is signed by the private key corresponding to any
     * public key in this file.  May be null to use the system default
     * file (currently "/system/etc/security/otacerts.zip").
     *
     * @throws IOException if there were any errors reading the
     * package or certs files.
     * @throws GeneralSecurityException if verification failed
     */
public static void verifyPackage(File packageFile, ProgressListener listener, File deviceCertsZipFile) throws IOException, GeneralSecurityException {
    long fileLen = packageFile.length();
    RandomAccessFile raf = new RandomAccessFile(packageFile, "r");
    try {
        int lastPercent = 0;
        long lastPublishTime = System.currentTimeMillis();
        if (listener != null) {
            listener.onProgress(lastPercent);
        }
        raf.seek(fileLen - 6);
        byte[] footer = new byte[6];
        raf.readFully(footer);
        if (footer[2] != (byte) 0xff || footer[3] != (byte) 0xff) {
            throw new SignatureException("no signature in file (no footer)");
        }
        int commentSize = (footer[4] & 0xff) | ((footer[5] & 0xff) << 8);
        int signatureStart = (footer[0] & 0xff) | ((footer[1] & 0xff) << 8);
        byte[] eocd = new byte[commentSize + 22];
        raf.seek(fileLen - (commentSize + 22));
        raf.readFully(eocd);
        // end-of-central-directory record.
        if (eocd[0] != (byte) 0x50 || eocd[1] != (byte) 0x4b || eocd[2] != (byte) 0x05 || eocd[3] != (byte) 0x06) {
            throw new SignatureException("no signature in file (bad footer)");
        }
        for (int i = 4; i < eocd.length - 3; ++i) {
            if (eocd[i] == (byte) 0x50 && eocd[i + 1] == (byte) 0x4b && eocd[i + 2] == (byte) 0x05 && eocd[i + 3] == (byte) 0x06) {
                throw new SignatureException("EOCD marker found after start of EOCD");
            }
        }
        // The following code is largely copied from
        // JarUtils.verifySignature().  We could just *call* that
        // method here if that function didn't read the entire
        // input (ie, the whole OTA package) into memory just to
        // compute its message digest.
        BerInputStream bis = new BerInputStream(new ByteArrayInputStream(eocd, commentSize + 22 - signatureStart, signatureStart));
        ContentInfo info = (ContentInfo) ContentInfo.ASN1.decode(bis);
        SignedData signedData = info.getSignedData();
        if (signedData == null) {
            throw new IOException("signedData is null");
        }
        Collection encCerts = signedData.getCertificates();
        if (encCerts.isEmpty()) {
            throw new IOException("encCerts is empty");
        }
        // Take the first certificate from the signature (packages
        // should contain only one).
        Iterator it = encCerts.iterator();
        X509Certificate cert = null;
        if (it.hasNext()) {
            cert = new X509CertImpl((org.apache.harmony.security.x509.Certificate) it.next());
        } else {
            throw new SignatureException("signature contains no certificates");
        }
        List sigInfos = signedData.getSignerInfos();
        SignerInfo sigInfo;
        if (!sigInfos.isEmpty()) {
            sigInfo = (SignerInfo) sigInfos.get(0);
        } else {
            throw new IOException("no signer infos!");
        }
        // Check that the public key of the certificate contained
        // in the package equals one of our trusted public keys.
        HashSet<Certificate> trusted = getTrustedCerts(deviceCertsZipFile == null ? DEFAULT_KEYSTORE : deviceCertsZipFile);
        PublicKey signatureKey = cert.getPublicKey();
        boolean verified = false;
        for (Certificate c : trusted) {
            if (c.getPublicKey().equals(signatureKey)) {
                verified = true;
                break;
            }
        }
        if (!verified) {
            throw new SignatureException("signature doesn't match any trusted key");
        }
        // The signature cert matches a trusted key.  Now verify that
        // the digest in the cert matches the actual file data.
        // The verifier in recovery *only* handles SHA1withRSA
        // signatures.  SignApk.java always uses SHA1withRSA, no
        // matter what the cert says to use.  Ignore
        // cert.getSigAlgName(), and instead use whatever
        // algorithm is used by the signature (which should be
        // SHA1withRSA).
        String da = sigInfo.getDigestAlgorithm();
        String dea = sigInfo.getDigestEncryptionAlgorithm();
        String alg = null;
        if (da == null || dea == null) {
            // fall back to the cert algorithm if the sig one
            // doesn't look right.
            alg = cert.getSigAlgName();
        } else {
            alg = da + "with" + dea;
        }
        Signature sig = Signature.getInstance(alg);
        sig.initVerify(cert);
        // The signature covers all of the OTA package except the
        // archive comment and its 2-byte length.
        long toRead = fileLen - commentSize - 2;
        long soFar = 0;
        raf.seek(0);
        byte[] buffer = new byte[4096];
        boolean interrupted = false;
        while (soFar < toRead) {
            interrupted = Thread.interrupted();
            if (interrupted)
                break;
            int size = buffer.length;
            if (soFar + size > toRead) {
                size = (int) (toRead - soFar);
            }
            int read = raf.read(buffer, 0, size);
            sig.update(buffer, 0, read);
            soFar += read;
            if (listener != null) {
                long now = System.currentTimeMillis();
                int p = (int) (soFar * 100 / toRead);
                if (p > lastPercent && now - lastPublishTime > PUBLISH_PROGRESS_INTERVAL_MS) {
                    lastPercent = p;
                    lastPublishTime = now;
                    listener.onProgress(lastPercent);
                }
            }
        }
        if (listener != null) {
            listener.onProgress(100);
        }
        if (interrupted) {
            throw new SignatureException("verification was interrupted");
        }
        if (!sig.verify(sigInfo.getEncryptedDigest())) {
            throw new SignatureException("signature digest verification failed");
        }
    } finally {
        raf.close();
    }
}

Example 3 with SignerInfo

use of com.android.apksig.internal.pkcs7.SignerInfo in project XobotOS by xamarin.

the class RecoverySystem method verifyPackage.

/**
     * Verify the cryptographic signature of a system update package
     * before installing it.  Note that the package is also verified
     * separately by the installer once the device is rebooted into
     * the recovery system.  This function will return only if the
     * package was successfully verified; otherwise it will throw an
     * exception.
     *
     * Verification of a package can take significant time, so this
     * function should not be called from a UI thread.  Interrupting
     * the thread while this function is in progress will result in a
     * SecurityException being thrown (and the thread's interrupt flag
     * will be cleared).
     *
     * @param packageFile  the package to be verified
     * @param listener     an object to receive periodic progress
     * updates as verification proceeds.  May be null.
     * @param deviceCertsZipFile  the zip file of certificates whose
     * public keys we will accept.  Verification succeeds if the
     * package is signed by the private key corresponding to any
     * public key in this file.  May be null to use the system default
     * file (currently "/system/etc/security/otacerts.zip").
     *
     * @throws IOException if there were any errors reading the
     * package or certs files.
     * @throws GeneralSecurityException if verification failed
     */
public static void verifyPackage(File packageFile, ProgressListener listener, File deviceCertsZipFile) throws IOException, GeneralSecurityException {
    long fileLen = packageFile.length();
    RandomAccessFile raf = new RandomAccessFile(packageFile, "r");
    try {
        int lastPercent = 0;
        long lastPublishTime = System.currentTimeMillis();
        if (listener != null) {
            listener.onProgress(lastPercent);
        }
        raf.seek(fileLen - 6);
        byte[] footer = new byte[6];
        raf.readFully(footer);
        if (footer[2] != (byte) 0xff || footer[3] != (byte) 0xff) {
            throw new SignatureException("no signature in file (no footer)");
        }
        int commentSize = (footer[4] & 0xff) | ((footer[5] & 0xff) << 8);
        int signatureStart = (footer[0] & 0xff) | ((footer[1] & 0xff) << 8);
        Log.v(TAG, String.format("comment size %d; signature start %d", commentSize, signatureStart));
        byte[] eocd = new byte[commentSize + 22];
        raf.seek(fileLen - (commentSize + 22));
        raf.readFully(eocd);
        // end-of-central-directory record.
        if (eocd[0] != (byte) 0x50 || eocd[1] != (byte) 0x4b || eocd[2] != (byte) 0x05 || eocd[3] != (byte) 0x06) {
            throw new SignatureException("no signature in file (bad footer)");
        }
        for (int i = 4; i < eocd.length - 3; ++i) {
            if (eocd[i] == (byte) 0x50 && eocd[i + 1] == (byte) 0x4b && eocd[i + 2] == (byte) 0x05 && eocd[i + 3] == (byte) 0x06) {
                throw new SignatureException("EOCD marker found after start of EOCD");
            }
        }
        // The following code is largely copied from
        // JarUtils.verifySignature().  We could just *call* that
        // method here if that function didn't read the entire
        // input (ie, the whole OTA package) into memory just to
        // compute its message digest.
        BerInputStream bis = new BerInputStream(new ByteArrayInputStream(eocd, commentSize + 22 - signatureStart, signatureStart));
        ContentInfo info = (ContentInfo) ContentInfo.ASN1.decode(bis);
        SignedData signedData = info.getSignedData();
        if (signedData == null) {
            throw new IOException("signedData is null");
        }
        Collection encCerts = signedData.getCertificates();
        if (encCerts.isEmpty()) {
            throw new IOException("encCerts is empty");
        }
        // Take the first certificate from the signature (packages
        // should contain only one).
        Iterator it = encCerts.iterator();
        X509Certificate cert = null;
        if (it.hasNext()) {
            cert = new X509CertImpl((org.apache.harmony.security.x509.Certificate) it.next());
        } else {
            throw new SignatureException("signature contains no certificates");
        }
        List sigInfos = signedData.getSignerInfos();
        SignerInfo sigInfo;
        if (!sigInfos.isEmpty()) {
            sigInfo = (SignerInfo) sigInfos.get(0);
        } else {
            throw new IOException("no signer infos!");
        }
        // Check that the public key of the certificate contained
        // in the package equals one of our trusted public keys.
        HashSet<Certificate> trusted = getTrustedCerts(deviceCertsZipFile == null ? DEFAULT_KEYSTORE : deviceCertsZipFile);
        PublicKey signatureKey = cert.getPublicKey();
        boolean verified = false;
        for (Certificate c : trusted) {
            if (c.getPublicKey().equals(signatureKey)) {
                verified = true;
                break;
            }
        }
        if (!verified) {
            throw new SignatureException("signature doesn't match any trusted key");
        }
        // The signature cert matches a trusted key.  Now verify that
        // the digest in the cert matches the actual file data.
        // The verifier in recovery *only* handles SHA1withRSA
        // signatures.  SignApk.java always uses SHA1withRSA, no
        // matter what the cert says to use.  Ignore
        // cert.getSigAlgName(), and instead use whatever
        // algorithm is used by the signature (which should be
        // SHA1withRSA).
        String da = sigInfo.getDigestAlgorithm();
        String dea = sigInfo.getDigestEncryptionAlgorithm();
        String alg = null;
        if (da == null || dea == null) {
            // fall back to the cert algorithm if the sig one
            // doesn't look right.
            alg = cert.getSigAlgName();
        } else {
            alg = da + "with" + dea;
        }
        Signature sig = Signature.getInstance(alg);
        sig.initVerify(cert);
        // The signature covers all of the OTA package except the
        // archive comment and its 2-byte length.
        long toRead = fileLen - commentSize - 2;
        long soFar = 0;
        raf.seek(0);
        byte[] buffer = new byte[4096];
        boolean interrupted = false;
        while (soFar < toRead) {
            interrupted = Thread.interrupted();
            if (interrupted)
                break;
            int size = buffer.length;
            if (soFar + size > toRead) {
                size = (int) (toRead - soFar);
            }
            int read = raf.read(buffer, 0, size);
            sig.update(buffer, 0, read);
            soFar += read;
            if (listener != null) {
                long now = System.currentTimeMillis();
                int p = (int) (soFar * 100 / toRead);
                if (p > lastPercent && now - lastPublishTime > PUBLISH_PROGRESS_INTERVAL_MS) {
                    lastPercent = p;
                    lastPublishTime = now;
                    listener.onProgress(lastPercent);
                }
            }
        }
        if (listener != null) {
            listener.onProgress(100);
        }
        if (interrupted) {
            throw new SignatureException("verification was interrupted");
        }
        if (!sig.verify(sigInfo.getEncryptedDigest())) {
            throw new SignatureException("signature digest verification failed");
        }
    } finally {
        raf.close();
    }
}

Example 4 with SignerInfo

use of com.android.apksig.internal.pkcs7.SignerInfo in project j2objc by google.

the class JarUtils method verifySignature.

/**
     * This method handle all the work with  PKCS7, ASN1 encoding, signature verifying,
     * and certification path building.
     * See also PKCS #7: Cryptographic Message Syntax Standard:
     * http://www.ietf.org/rfc/rfc2315.txt
     * @param signature - the input stream of signature file to be verified
     * @param signatureBlock - the input stream of corresponding signature block file
     * @return array of certificates used to verify the signature file
     * @throws IOException - if some errors occurs during reading from the stream
     * @throws GeneralSecurityException - if signature verification process fails
     */
public static Certificate[] verifySignature(InputStream signature, InputStream signatureBlock) throws IOException, GeneralSecurityException {
    BerInputStream bis = new BerInputStream(signatureBlock);
    ContentInfo info = (ContentInfo) ContentInfo.ASN1.decode(bis);
    SignedData signedData = info.getSignedData();
    if (signedData == null) {
        throw new IOException("No SignedData found");
    }
    Collection<org.apache.harmony.security.x509.Certificate> encCerts = signedData.getCertificates();
    if (encCerts.isEmpty()) {
        return null;
    }
    X509Certificate[] certs = new X509Certificate[encCerts.size()];
    CertificateFactory cf = CertificateFactory.getInstance("X.509");
    int i = 0;
    for (org.apache.harmony.security.x509.Certificate encCert : encCerts) {
        final byte[] encoded = encCert.getEncoded();
        final InputStream is = new ByteArrayInputStream(encoded);
        certs[i++] = new VerbatimX509Certificate((X509Certificate) cf.generateCertificate(is), encoded);
    }
    List<SignerInfo> sigInfos = signedData.getSignerInfos();
    SignerInfo sigInfo;
    if (!sigInfos.isEmpty()) {
        sigInfo = sigInfos.get(0);
    } else {
        return null;
    }
    // Issuer
    X500Principal issuer = sigInfo.getIssuer();
    // Certificate serial number
    BigInteger snum = sigInfo.getSerialNumber();
    // Locate the certificate
    int issuerSertIndex = 0;
    for (i = 0; i < certs.length; i++) {
        if (issuer.equals(certs[i].getIssuerDN()) && snum.equals(certs[i].getSerialNumber())) {
            issuerSertIndex = i;
            break;
        }
    }
    if (i == certs.length) {
        // No issuer certificate found
        return null;
    }
    if (certs[issuerSertIndex].hasUnsupportedCriticalExtension()) {
        throw new SecurityException("Can not recognize a critical extension");
    }
    // Get Signature instance
    final String daOid = sigInfo.getDigestAlgorithm();
    final String daName = sigInfo.getDigestAlgorithmName();
    final String deaOid = sigInfo.getDigestEncryptionAlgorithm();
    final String deaName = sigInfo.getDigestEncryptionAlgorithmName();
    String alg = null;
    Signature sig = null;
    if (daOid != null && deaOid != null) {
        alg = daOid + "with" + deaOid;
        try {
            sig = Signature.getInstance(alg);
        } catch (NoSuchAlgorithmException e) {
        }
        // Try to convert to names instead of OID.
        if (sig == null && daName != null && deaName != null) {
            alg = daName + "with" + deaName;
            try {
                sig = Signature.getInstance(alg);
            } catch (NoSuchAlgorithmException e) {
            }
        }
    }
    if (sig == null && deaOid != null) {
        alg = deaOid;
        try {
            sig = Signature.getInstance(alg);
        } catch (NoSuchAlgorithmException e) {
        }
        if (sig == null) {
            alg = deaName;
            try {
                sig = Signature.getInstance(alg);
            } catch (NoSuchAlgorithmException e) {
            }
        }
    }
    // We couldn't find a valid Signature type.
    if (sig == null) {
        return null;
    }
    sig.initVerify(certs[issuerSertIndex]);
    // If the authenticatedAttributes field of SignerInfo contains more than zero attributes,
    // compute the message digest on the ASN.1 DER encoding of the Attributes value.
    // Otherwise, compute the message digest on the data.
    List<AttributeTypeAndValue> atr = sigInfo.getAuthenticatedAttributes();
    byte[] sfBytes = new byte[signature.available()];
    signature.read(sfBytes);
    if (atr == null) {
        sig.update(sfBytes);
    } else {
        sig.update(sigInfo.getEncodedAuthenticatedAttributes());
        // If the authenticatedAttributes field contains the message-digest attribute,
        // verify that it equals the computed digest of the signature file
        byte[] existingDigest = null;
        for (AttributeTypeAndValue a : atr) {
            if (Arrays.equals(a.getType().getOid(), MESSAGE_DIGEST_OID)) {
                if (existingDigest != null) {
                    throw new SecurityException("Too many MessageDigest attributes");
                }
                Collection<?> entries = a.getValue().getValues(ASN1OctetString.getInstance());
                if (entries.size() != 1) {
                    throw new SecurityException("Too many values for MessageDigest attribute");
                }
                existingDigest = (byte[]) entries.iterator().next();
            }
        }
        // must have a message-digest attribute.
        if (existingDigest == null) {
            throw new SecurityException("Missing MessageDigest in Authenticated Attributes");
        }
        MessageDigest md = null;
        if (daOid != null) {
            md = MessageDigest.getInstance(daOid);
        }
        if (md == null && daName != null) {
            md = MessageDigest.getInstance(daName);
        }
        if (md == null) {
            return null;
        }
        byte[] computedDigest = md.digest(sfBytes);
        if (!Arrays.equals(existingDigest, computedDigest)) {
            throw new SecurityException("Incorrect MD");
        }
    }
    if (!sig.verify(sigInfo.getEncryptedDigest())) {
        throw new SecurityException("Incorrect signature");
    }
    return createChain(certs[issuerSertIndex], certs);
}

Example 5 with SignerInfo

use of com.android.apksig.internal.pkcs7.SignerInfo in project robovm by robovm.

the class JarUtils method verifySignature.

/**
     * This method handle all the work with  PKCS7, ASN1 encoding, signature verifying,
     * and certification path building.
     * See also PKCS #7: Cryptographic Message Syntax Standard:
     * http://www.ietf.org/rfc/rfc2315.txt
     * @param signature - the input stream of signature file to be verified
     * @param signatureBlock - the input stream of corresponding signature block file
     * @return array of certificates used to verify the signature file
     * @throws IOException - if some errors occurs during reading from the stream
     * @throws GeneralSecurityException - if signature verification process fails
     */
public static Certificate[] verifySignature(InputStream signature, InputStream signatureBlock) throws IOException, GeneralSecurityException {
    BerInputStream bis = new BerInputStream(signatureBlock);
    ContentInfo info = (ContentInfo) ContentInfo.ASN1.decode(bis);
    SignedData signedData = info.getSignedData();
    if (signedData == null) {
        throw new IOException("No SignedData found");
    }
    Collection<org.apache.harmony.security.x509.Certificate> encCerts = signedData.getCertificates();
    if (encCerts.isEmpty()) {
        return null;
    }
    X509Certificate[] certs = new X509Certificate[encCerts.size()];
    int i = 0;
    for (org.apache.harmony.security.x509.Certificate encCert : encCerts) {
        certs[i++] = new X509CertImpl(encCert);
    }
    List<SignerInfo> sigInfos = signedData.getSignerInfos();
    SignerInfo sigInfo;
    if (!sigInfos.isEmpty()) {
        sigInfo = sigInfos.get(0);
    } else {
        return null;
    }
    // Issuer
    X500Principal issuer = sigInfo.getIssuer();
    // Certificate serial number
    BigInteger snum = sigInfo.getSerialNumber();
    // Locate the certificate
    int issuerSertIndex = 0;
    for (i = 0; i < certs.length; i++) {
        if (issuer.equals(certs[i].getIssuerDN()) && snum.equals(certs[i].getSerialNumber())) {
            issuerSertIndex = i;
            break;
        }
    }
    if (i == certs.length) {
        // No issuer certificate found
        return null;
    }
    if (certs[issuerSertIndex].hasUnsupportedCriticalExtension()) {
        throw new SecurityException("Can not recognize a critical extension");
    }
    // Get Signature instance
    final String daOid = sigInfo.getDigestAlgorithm();
    final String daName = sigInfo.getDigestAlgorithmName();
    final String deaOid = sigInfo.getDigestEncryptionAlgorithm();
    String alg = null;
    Signature sig = null;
    if (daOid != null && deaOid != null) {
        alg = daOid + "with" + deaOid;
        try {
            sig = Signature.getInstance(alg);
        } catch (NoSuchAlgorithmException e) {
        }
        // Try to convert to names instead of OID.
        if (sig == null) {
            final String deaName = sigInfo.getDigestEncryptionAlgorithmName();
            alg = daName + "with" + deaName;
            try {
                sig = Signature.getInstance(alg);
            } catch (NoSuchAlgorithmException e) {
            }
        }
    }
    /*
         * TODO figure out the case in which we'd only use digestAlgorithm and
         * add a test for it.
         */
    if (sig == null && daOid != null) {
        alg = daOid;
        try {
            sig = Signature.getInstance(alg);
        } catch (NoSuchAlgorithmException e) {
        }
        if (sig == null && daName != null) {
            alg = daName;
            try {
                sig = Signature.getInstance(alg);
            } catch (NoSuchAlgorithmException e) {
            }
        }
    }
    // We couldn't find a valid Signature type.
    if (sig == null) {
        return null;
    }
    sig.initVerify(certs[issuerSertIndex]);
    // If the authenticatedAttributes field of SignerInfo contains more than zero attributes,
    // compute the message digest on the ASN.1 DER encoding of the Attributes value.
    // Otherwise, compute the message digest on the data.
    List<AttributeTypeAndValue> atr = sigInfo.getAuthenticatedAttributes();
    byte[] sfBytes = new byte[signature.available()];
    signature.read(sfBytes);
    if (atr == null) {
        sig.update(sfBytes);
    } else {
        sig.update(sigInfo.getEncodedAuthenticatedAttributes());
        // If the authenticatedAttributes field contains the message-digest attribute,
        // verify that it equals the computed digest of the signature file
        byte[] existingDigest = null;
        for (AttributeTypeAndValue a : atr) {
            if (Arrays.equals(a.getType().getOid(), MESSAGE_DIGEST_OID)) {
                if (existingDigest != null) {
                    throw new SecurityException("Too many MessageDigest attributes");
                }
                Collection<?> entries = a.getValue().getValues(ASN1OctetString.getInstance());
                if (entries.size() != 1) {
                    throw new SecurityException("Too many values for MessageDigest attribute");
                }
                existingDigest = (byte[]) entries.iterator().next();
            }
        }
        // message digest entry.
        if (existingDigest == null) {
            throw new SecurityException("Missing MessageDigest in Authenticated Attributes");
        }
        MessageDigest md = null;
        if (daOid != null) {
            md = MessageDigest.getInstance(daOid);
        }
        if (md == null && daName != null) {
            md = MessageDigest.getInstance(daName);
        }
        if (md == null) {
            return null;
        }
        byte[] computedDigest = md.digest(sfBytes);
        if (!Arrays.equals(existingDigest, computedDigest)) {
            throw new SecurityException("Incorrect MD");
        }
    }
    if (!sig.verify(sigInfo.getEncryptedDigest())) {
        throw new SecurityException("Incorrect signature");
    }
    return createChain(certs[issuerSertIndex], certs);
}