content: package com.topjohnwu.magisk.signing;
  
  import org.bouncycastle.asn1.ASN1Encoding;
  import org.bouncycastle.asn1.ASN1InputStream;
  import org.bouncycastle.asn1.ASN1OutputStream;
  import org.bouncycastle.cert.jcajce.JcaCertStore;
  import org.bouncycastle.cms.CMSException;
  import org.bouncycastle.cms.CMSProcessableByteArray;
  import org.bouncycastle.cms.CMSSignedData;
  import org.bouncycastle.cms.CMSSignedDataGenerator;
  import org.bouncycastle.cms.CMSTypedData;
  import org.bouncycastle.cms.jcajce.JcaSignerInfoGeneratorBuilder;
  import org.bouncycastle.operator.ContentSigner;
  import org.bouncycastle.operator.OperatorCreationException;
  import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
  import org.bouncycastle.operator.jcajce.JcaDigestCalculatorProviderBuilder;
  import org.bouncycastle.util.encoders.Base64;
  
  import java.io.ByteArrayOutputStream;
  import java.io.FilterOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.PrintStream;
  import java.nio.ByteBuffer;
  import java.security.DigestOutputStream;
  import java.security.GeneralSecurityException;
  import java.security.InvalidKeyException;
  import java.security.MessageDigest;
  import java.security.PrivateKey;
  import java.security.PublicKey;
  import java.security.cert.CertificateEncodingException;
  import java.security.cert.X509Certificate;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.TimeZone;
  import java.util.TreeMap;
  import java.util.jar.Attributes;
  import java.util.jar.JarEntry;
  import java.util.jar.JarFile;
  import java.util.jar.JarOutputStream;
  import java.util.jar.Manifest;
  import java.util.regex.Pattern;
  
  /*
   * Modified from from AOSP
   * https://android.googlesource.com/platform/build/+/refs/tags/android-7.1.2_r39/tools/signapk/src/com/android/signapk/SignApk.java
   * */
  
  public class SignApk {
      private static final String CERT_SF_NAME = "META-INF/CERT.SF";
      private static final String CERT_SIG_NAME = "META-INF/CERT.%s";
      private static final String CERT_SF_MULTI_NAME = "META-INF/CERT%d.SF";
      private static final String CERT_SIG_MULTI_NAME = "META-INF/CERT%d.%s";
  
      // bitmasks for which hash algorithms we need the manifest to include.
      private static final int USE_SHA1 = 1;
      private static final int USE_SHA256 = 2;
  
      /**
       * Digest algorithm used when signing the APK using APK Signature Scheme v2.
       */
      private static final String APK_SIG_SCHEME_V2_DIGEST_ALGORITHM = "SHA-256";
      // Files matching this pattern are not copied to the output.
      private static final Pattern stripPattern =
              Pattern.compile("^(META-INF/((.*)[.](SF|RSA|DSA|EC)|com/android/otacert))|(" +
                      Pattern.quote(JarFile.MANIFEST_NAME) + ")$");
  
      /**
       * Return one of USE_SHA1 or USE_SHA256 according to the signature
       * algorithm specified in the cert.
       */
      private static int getDigestAlgorithm(X509Certificate cert) {
          String sigAlg = cert.getSigAlgName().toUpperCase(Locale.US);
          if ("SHA1WITHRSA".equals(sigAlg) || "MD5WITHRSA".equals(sigAlg)) {
              return USE_SHA1;
          } else if (sigAlg.startsWith("SHA256WITH")) {
              return USE_SHA256;
          } else {
              throw new IllegalArgumentException("unsupported signature algorithm \"" + sigAlg +
                      "\" in cert [" + cert.getSubjectDN());
          }
      }
  
      /**
       * Returns the expected signature algorithm for this key type.
       */
      private static String getSignatureAlgorithm(X509Certificate cert) {
          String keyType = cert.getPublicKey().getAlgorithm().toUpperCase(Locale.US);
          if ("RSA".equalsIgnoreCase(keyType)) {
              if (getDigestAlgorithm(cert) == USE_SHA256) {
                  return "SHA256withRSA";
              } else {
                  return "SHA1withRSA";
              }
          } else if ("EC".equalsIgnoreCase(keyType)) {
              return "SHA256withECDSA";
          } else {
              throw new IllegalArgumentException("unsupported key type: " + keyType);
          }
      }
  
      /**
       * Add the hash(es) of every file to the manifest, creating it if
       * necessary.
       */
      private static Manifest addDigestsToManifest(JarMap jar, int hashes)
              throws IOException, GeneralSecurityException {
          Manifest input = jar.getManifest();
          Manifest output = new Manifest();
          Attributes main = output.getMainAttributes();
          if (input != null) {
              main.putAll(input.getMainAttributes());
          } else {
              main.putValue("Manifest-Version", "1.0");
              main.putValue("Created-By", "1.0 (Android SignApk)");
          }
  
          MessageDigest md_sha1 = null;
          MessageDigest md_sha256 = null;
          if ((hashes & USE_SHA1) != 0) {
              md_sha1 = MessageDigest.getInstance("SHA1");
          }
          if ((hashes & USE_SHA256) != 0) {
              md_sha256 = MessageDigest.getInstance("SHA256");
          }
  
          byte[] buffer = new byte[4096];
          int num;
  
          // We sort the input entries by name, and add them to the
          // output manifest in sorted order.  We expect that the output
          // map will be deterministic.
  
          TreeMap<String, JarEntry> byName = new TreeMap<>();
  
          for (Enumeration<JarEntry> e = jar.entries(); e.hasMoreElements(); ) {
              JarEntry entry = e.nextElement();
              byName.put(entry.getName(), entry);
          }
  
          for (JarEntry entry : byName.values()) {
              String name = entry.getName();
              if (!entry.isDirectory() && !stripPattern.matcher(name).matches()) {
                  InputStream data = jar.getInputStream(entry);
                  while ((num = data.read(buffer)) > 0) {
                      if (md_sha1 != null) md_sha1.update(buffer, 0, num);
                      if (md_sha256 != null) md_sha256.update(buffer, 0, num);
                  }
  
                  Attributes attr = null;
                  if (input != null) attr = input.getAttributes(name);
                  attr = attr != null ? new Attributes(attr) : new Attributes();
                  // Remove any previously computed digests from this entry's attributes.
                  for (Iterator<Object> i = attr.keySet().iterator(); i.hasNext(); ) {
                      Object key = i.next();
                      if (!(key instanceof Attributes.Name)) {
                          continue;
                      }
                      String attributeNameLowerCase =
                              key.toString().toLowerCase(Locale.US);
                      if (attributeNameLowerCase.endsWith("-digest")) {
                          i.remove();
                      }
                  }
                  // Add SHA-1 digest if requested
                  if (md_sha1 != null) {
                      attr.putValue("SHA1-Digest",
                              new String(Base64.encode(md_sha1.digest()), "ASCII"));
                  }
                  // Add SHA-256 digest if requested
                  if (md_sha256 != null) {
                      attr.putValue("SHA-256-Digest",
                              new String(Base64.encode(md_sha256.digest()), "ASCII"));
                  }
                  output.getEntries().put(name, attr);
              }
          }
  
          return output;
      }
  
      /**
       * Write a .SF file with a digest of the specified manifest.
       */
      private static void writeSignatureFile(Manifest manifest, OutputStream out,
                                             int hash)
              throws IOException, GeneralSecurityException {
          Manifest sf = new Manifest();
          Attributes main = sf.getMainAttributes();
          main.putValue("Signature-Version", "1.0");
          main.putValue("Created-By", "1.0 (Android SignApk)");
          // Add APK Signature Scheme v2 signature stripping protection.
          // This attribute indicates that this APK is supposed to have been signed using one or
          // more APK-specific signature schemes in addition to the standard JAR signature scheme
          // used by this code. APK signature verifier should reject the APK if it does not
          // contain a signature for the signature scheme the verifier prefers out of this set.
          main.putValue(
                  ApkSignerV2.SF_ATTRIBUTE_ANDROID_APK_SIGNED_NAME,
                  ApkSignerV2.SF_ATTRIBUTE_ANDROID_APK_SIGNED_VALUE);
  
          MessageDigest md = MessageDigest.getInstance(hash == USE_SHA256 ? "SHA256" : "SHA1");
          PrintStream print = new PrintStream(new DigestOutputStream(new ByteArrayOutputStream(), md),
                  true, "UTF-8");
  
          // Digest of the entire manifest
          manifest.write(print);
          print.flush();
          main.putValue(hash == USE_SHA256 ? "SHA-256-Digest-Manifest" : "SHA1-Digest-Manifest",
                  new String(Base64.encode(md.digest()), "ASCII"));
  
          Map<String, Attributes> entries = manifest.getEntries();
          for (Map.Entry<String, Attributes> entry : entries.entrySet()) {
              // Digest of the manifest stanza for this entry.
              print.print("Name: " + entry.getKey() + "\r\n");
              for (Map.Entry<Object, Object> att : entry.getValue().entrySet()) {
                  print.print(att.getKey() + ": " + att.getValue() + "\r\n");
              }
              print.print("\r\n");
              print.flush();
  
              Attributes sfAttr = new Attributes();
              sfAttr.putValue(hash == USE_SHA256 ? "SHA-256-Digest" : "SHA1-Digest",
                      new String(Base64.encode(md.digest()), "ASCII"));
              sf.getEntries().put(entry.getKey(), sfAttr);
          }
  
          CountOutputStream cout = new CountOutputStream(out);
          sf.write(cout);
  
          // A bug in the java.util.jar implementation of Android platforms
          // up to version 1.6 will cause a spurious IOException to be thrown
          // if the length of the signature file is a multiple of 1024 bytes.
          // As a workaround, add an extra CRLF in this case.
          if ((cout.size() % 1024) == 0) {
              cout.write('\r');
              cout.write('\n');
          }
      }
  
      /**
       * Sign data and write the digital signature to 'out'.
       */
      private static void writeSignatureBlock(
              CMSTypedData data, X509Certificate publicKey, PrivateKey privateKey, OutputStream out)
              throws IOException,
              CertificateEncodingException,
              OperatorCreationException,
              CMSException {
          ArrayList<X509Certificate> certList = new ArrayList<>(1);
          certList.add(publicKey);
          JcaCertStore certs = new JcaCertStore(certList);
  
          CMSSignedDataGenerator gen = new CMSSignedDataGenerator();
          ContentSigner signer = new JcaContentSignerBuilder(getSignatureAlgorithm(publicKey))
                  .build(privateKey);
          gen.addSignerInfoGenerator(
                  new JcaSignerInfoGeneratorBuilder(new JcaDigestCalculatorProviderBuilder().build())
                          .setDirectSignature(true)
                          .build(signer, publicKey)
          );
          gen.addCertificates(certs);
          CMSSignedData sigData = gen.generate(data, false);
  
          try (ASN1InputStream asn1 = new ASN1InputStream(sigData.getEncoded())) {
              ASN1OutputStream dos = ASN1OutputStream.create(out, ASN1Encoding.DER);
              dos.writeObject(asn1.readObject());
          }
      }
  
      /**
       * Copy all the files in a manifest from input to output.  We set
       * the modification times in the output to a fixed time, so as to
       * reduce variation in the output file and make incremental OTAs
       * more efficient.
       */
      private static void copyFiles(Manifest manifest, JarMap in, JarOutputStream out,
                                    long timestamp, int defaultAlignment) throws IOException {
          byte[] buffer = new byte[4096];
          int num;
  
          Map<String, Attributes> entries = manifest.getEntries();
          ArrayList<String> names = new ArrayList<>(entries.keySet());
          Collections.sort(names);
  
          boolean firstEntry = true;
          long offset = 0L;
  
          // We do the copy in two passes -- first copying all the
          // entries that are STORED, then copying all the entries that
          // have any other compression flag (which in practice means
          // DEFLATED).  This groups all the stored entries together at
          // the start of the file and makes it easier to do alignment
          // on them (since only stored entries are aligned).
  
          for (String name : names) {
              JarEntry inEntry = in.getJarEntry(name);
              JarEntry outEntry;
              if (inEntry.getMethod() != JarEntry.STORED) continue;
              // Preserve the STORED method of the input entry.
              outEntry = new JarEntry(inEntry);
              outEntry.setTime(timestamp);
              // Discard comment and extra fields of this entry to
              // simplify alignment logic below and for consistency with
              // how compressed entries are handled later.
              outEntry.setComment(null);
              outEntry.setExtra(null);
  
              // 'offset' is the offset into the file at which we expect
              // the file data to begin.  This is the value we need to
              // make a multiple of 'alignement'.
              offset += JarFile.LOCHDR + outEntry.getName().length();
              if (firstEntry) {
                  // The first entry in a jar file has an extra field of
                  // four bytes that you can't get rid of; any extra
                  // data you specify in the JarEntry is appended to
                  // these forced four bytes.  This is JAR_MAGIC in
                  // JarOutputStream; the bytes are 0xfeca0000.
                  offset += 4;
                  firstEntry = false;
              }
              int alignment = getStoredEntryDataAlignment(name, defaultAlignment);
              if (alignment > 0 && (offset % alignment != 0)) {
                  // Set the "extra data" of the entry to between 1 and
                  // alignment-1 bytes, to make the file data begin at
                  // an aligned offset.
                  int needed = alignment - (int) (offset % alignment);
                  outEntry.setExtra(new byte[needed]);
                  offset += needed;
              }
  
              out.putNextEntry(outEntry);
  
              InputStream data = in.getInputStream(inEntry);
              while ((num = data.read(buffer)) > 0) {
                  out.write(buffer, 0, num);
                  offset += num;
              }
              out.flush();
          }
  
          // Copy all the non-STORED entries.  We don't attempt to
          // maintain the 'offset' variable past this point; we don't do
          // alignment on these entries.
  
          for (String name : names) {
              JarEntry inEntry = in.getJarEntry(name);
              JarEntry outEntry;
              if (inEntry.getMethod() == JarEntry.STORED) continue;
              // Create a new entry so that the compressed len is recomputed.
              outEntry = new JarEntry(name);
              outEntry.setTime(timestamp);
              out.putNextEntry(outEntry);
  
              InputStream data = in.getInputStream(inEntry);
              while ((num = data.read(buffer)) > 0) {
                  out.write(buffer, 0, num);
              }
              out.flush();
          }
      }
  
      /**
       * Returns the multiple (in bytes) at which the provided {@code STORED} entry's data must start
       * relative to start of file or {@code 0} if alignment of this entry's data is not important.
       */
      private static int getStoredEntryDataAlignment(String entryName, int defaultAlignment) {
          if (defaultAlignment <= 0) {
              return 0;
          }
  
          if (entryName.endsWith(".so")) {
              // Align .so contents to memory page boundary to enable memory-mapped
              // execution.
              return 4096;
          } else {
              return defaultAlignment;
          }
      }
  
      private static void signFile(Manifest manifest,
                                   X509Certificate[] publicKey, PrivateKey[] privateKey,
                                   long timestamp, JarOutputStream outputJar) throws Exception {
          // MANIFEST.MF
          JarEntry je = new JarEntry(JarFile.MANIFEST_NAME);
          je.setTime(timestamp);
          outputJar.putNextEntry(je);
          manifest.write(outputJar);
  
          int numKeys = publicKey.length;
          for (int k = 0; k < numKeys; ++k) {
              // CERT.SF / CERT#.SF
              je = new JarEntry(numKeys == 1 ? CERT_SF_NAME :
                      (String.format(Locale.US, CERT_SF_MULTI_NAME, k)));
              je.setTime(timestamp);
              outputJar.putNextEntry(je);
              ByteArrayOutputStream baos = new ByteArrayOutputStream();
              writeSignatureFile(manifest, baos, getDigestAlgorithm(publicKey[k]));
              byte[] signedData = baos.toByteArray();
              outputJar.write(signedData);
  
              // CERT.{EC,RSA} / CERT#.{EC,RSA}
              final String keyType = publicKey[k].getPublicKey().getAlgorithm();
              je = new JarEntry(numKeys == 1 ? (String.format(CERT_SIG_NAME, keyType)) :
                      (String.format(Locale.US, CERT_SIG_MULTI_NAME, k, keyType)));
              je.setTime(timestamp);
              outputJar.putNextEntry(je);
              writeSignatureBlock(new CMSProcessableByteArray(signedData),
                      publicKey[k], privateKey[k], outputJar);
          }
      }
  
      /**
       * Converts the provided lists of private keys, their X.509 certificates, and digest algorithms
       * into a list of APK Signature Scheme v2 {@code SignerConfig} instances.
       */
      private static List<ApkSignerV2.SignerConfig> createV2SignerConfigs(
              PrivateKey[] privateKeys, X509Certificate[] certificates, String[] digestAlgorithms)
              throws InvalidKeyException {
          if (privateKeys.length != certificates.length) {
              throw new IllegalArgumentException(
                      "The number of private keys must match the number of certificates: "
                              + privateKeys.length + " vs" + certificates.length);
          }
          List<ApkSignerV2.SignerConfig> result = new ArrayList<>(privateKeys.length);
          for (int i = 0; i < privateKeys.length; i++) {
              PrivateKey privateKey = privateKeys[i];
              X509Certificate certificate = certificates[i];
              PublicKey publicKey = certificate.getPublicKey();
              String keyAlgorithm = privateKey.getAlgorithm();
              if (!keyAlgorithm.equalsIgnoreCase(publicKey.getAlgorithm())) {
                  throw new InvalidKeyException(
                          "Key algorithm of private key #" + (i + 1) + " does not match key"
                                  + " algorithm of public key #" + (i + 1) + ": " + keyAlgorithm
                                  + " vs " + publicKey.getAlgorithm());
              }
              ApkSignerV2.SignerConfig signerConfig = new ApkSignerV2.SignerConfig();
              signerConfig.privateKey = privateKey;
              signerConfig.certificates = Collections.singletonList(certificate);
              List<Integer> signatureAlgorithms = new ArrayList<>(digestAlgorithms.length);
              for (String digestAlgorithm : digestAlgorithms) {
                  try {
                      signatureAlgorithms.add(getV2SignatureAlgorithm(keyAlgorithm, digestAlgorithm));
                  } catch (IllegalArgumentException e) {
                      throw new InvalidKeyException(
                              "Unsupported key and digest algorithm combination for signer #"
                                      + (i + 1), e);
                  }
              }
              signerConfig.signatureAlgorithms = signatureAlgorithms;
              result.add(signerConfig);
          }
          return result;
      }
  
      private static int getV2SignatureAlgorithm(String keyAlgorithm, String digestAlgorithm) {
          if ("SHA-256".equalsIgnoreCase(digestAlgorithm)) {
              if ("RSA".equalsIgnoreCase(keyAlgorithm)) {
                  // Use RSASSA-PKCS1-v1_5 signature scheme instead of RSASSA-PSS to guarantee
                  // deterministic signatures which make life easier for OTA updates (fewer files
                  // changed when deterministic signature schemes are used).
                  return ApkSignerV2.SIGNATURE_RSA_PKCS1_V1_5_WITH_SHA256;
              } else if ("EC".equalsIgnoreCase(keyAlgorithm)) {
                  return ApkSignerV2.SIGNATURE_ECDSA_WITH_SHA256;
              } else if ("DSA".equalsIgnoreCase(keyAlgorithm)) {
                  return ApkSignerV2.SIGNATURE_DSA_WITH_SHA256;
              } else {
                  throw new IllegalArgumentException("Unsupported key algorithm: " + keyAlgorithm);
              }
          } else if ("SHA-512".equalsIgnoreCase(digestAlgorithm)) {
              if ("RSA".equalsIgnoreCase(keyAlgorithm)) {
                  // Use RSASSA-PKCS1-v1_5 signature scheme instead of RSASSA-PSS to guarantee
                  // deterministic signatures which make life easier for OTA updates (fewer files
                  // changed when deterministic signature schemes are used).
                  return ApkSignerV2.SIGNATURE_RSA_PKCS1_V1_5_WITH_SHA512;
              } else if ("EC".equalsIgnoreCase(keyAlgorithm)) {
                  return ApkSignerV2.SIGNATURE_ECDSA_WITH_SHA512;
              } else if ("DSA".equalsIgnoreCase(keyAlgorithm)) {
                  return ApkSignerV2.SIGNATURE_DSA_WITH_SHA512;
              } else {
                  throw new IllegalArgumentException("Unsupported key algorithm: " + keyAlgorithm);
              }
          } else {
              throw new IllegalArgumentException("Unsupported digest algorithm: " + digestAlgorithm);
          }
      }
  
      public static void sign(X509Certificate cert, PrivateKey key,
                              JarMap inputJar, OutputStream outputStream) throws Exception {
          int alignment = 4;
          int hashes = 0;
  
          X509Certificate[] publicKey = new X509Certificate[1];
          publicKey[0] = cert;
          hashes |= getDigestAlgorithm(publicKey[0]);
  
          // Set all ZIP file timestamps to Jan 1 2009 00:00:00.
          long timestamp = 1230768000000L;
          // The Java ZipEntry API we're using converts milliseconds since epoch into MS-DOS
          // timestamp using the current timezone. We thus adjust the milliseconds since epoch
          // value to end up with MS-DOS timestamp of Jan 1 2009 00:00:00.
          timestamp -= TimeZone.getDefault().getOffset(timestamp);
  
          PrivateKey[] privateKey = new PrivateKey[1];
          privateKey[0] = key;
  
          // Generate, in memory, an APK signed using standard JAR Signature Scheme.
          ByteArrayOutputStream v1SignedApkBuf = new ByteArrayOutputStream();
          JarOutputStream outputJar = new JarOutputStream(v1SignedApkBuf);
          // Use maximum compression for compressed entries because the APK lives forever on
          // the system partition.
          outputJar.setLevel(9);
          Manifest manifest = addDigestsToManifest(inputJar, hashes);
          copyFiles(manifest, inputJar, outputJar, timestamp, alignment);
          signFile(manifest, publicKey, privateKey, timestamp, outputJar);
          outputJar.close();
          ByteBuffer v1SignedApk = ByteBuffer.wrap(v1SignedApkBuf.toByteArray());
          v1SignedApkBuf.reset();
  
          ByteBuffer[] outputChunks;
          List<ApkSignerV2.SignerConfig> signerConfigs = createV2SignerConfigs(privateKey, publicKey,
                  new String[]{APK_SIG_SCHEME_V2_DIGEST_ALGORITHM});
          outputChunks = ApkSignerV2.sign(v1SignedApk, signerConfigs);
  
          // This assumes outputChunks are array-backed. To avoid this assumption, the
          // code could be rewritten to use FileChannel.
          for (ByteBuffer outputChunk : outputChunks) {
              outputStream.write(outputChunk.array(),
                      outputChunk.arrayOffset() + outputChunk.position(), outputChunk.remaining());
              outputChunk.position(outputChunk.limit());
          }
      }
  
      /**
       * Write to another stream and track how many bytes have been
       * written.
       */
      private static class CountOutputStream extends FilterOutputStream {
          private int mCount;
  
          public CountOutputStream(OutputStream out) {
              super(out);
              mCount = 0;
          }
  
          @Override
          public void write(int b) throws IOException {
              super.write(b);
              mCount++;
          }
  
          @Override
          public void write(byte[] b, int off, int len) throws IOException {
              super.write(b, off, len);
              mCount += len;
          }
  
          public int size() {
              return mCount;
          }
      }
  }
  