/*
 * Copyright (C) 2017 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 android.util.apk;

import static android.content.pm.PackageManager.INSTALL_PARSE_FAILED_BAD_MANIFEST;
import static android.content.pm.PackageManager.INSTALL_PARSE_FAILED_CERTIFICATE_ENCODING;
import static android.content.pm.PackageManager.INSTALL_PARSE_FAILED_INCONSISTENT_CERTIFICATES;
import static android.content.pm.PackageManager.INSTALL_PARSE_FAILED_NO_CERTIFICATES;
import static android.content.pm.PackageManager.INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION;
import static android.os.Trace.TRACE_TAG_PACKAGE_MANAGER;

import android.content.pm.PackageParser;
import android.content.pm.PackageParser.PackageParserException;
import android.content.pm.PackageParser.SigningDetails.SignatureSchemeVersion;
import android.content.pm.Signature;
import android.os.Trace;
import android.util.jar.StrictJarFile;

import com.android.internal.util.ArrayUtils;

import libcore.io.IoUtils;

import java.io.IOException;
import java.io.InputStream;
import java.security.DigestException;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.security.cert.CertificateEncodingException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;
import java.util.zip.ZipEntry;

Facade class that takes care of the details of APK verification on
behalf of PackageParser.
@hide
for internal use only./**
 * Facade class that takes care of the details of APK verification on
 * behalf of PackageParser.
 *
 * @hide for internal use only.
 */
public class ApkSignatureVerifier {

    private static final AtomicReference<byte[]> sBuffer = new AtomicReference<>();

    
Verifies the provided APK and returns the certificates associated with each signer.
Throws:
PackageParserException – if the APK's signature failed to verify./**
     * Verifies the provided APK and returns the certificates associated with each signer.
     *
     * @throws PackageParserException if the APK's signature failed to verify.
     */
    public static PackageParser.SigningDetails verify(String apkPath,
            @SignatureSchemeVersion int minSignatureSchemeVersion)
            throws PackageParserException {

        if (minSignatureSchemeVersion > SignatureSchemeVersion.SIGNING_BLOCK_V3) {
            // V3 and before are older than the requested minimum signing version
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "No signature found in package of version " + minSignatureSchemeVersion
            + " or newer for package " + apkPath);
        }

        // first try v3
        Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "verifyV3");
        try {
            ApkSignatureSchemeV3Verifier.VerifiedSigner vSigner =
                    ApkSignatureSchemeV3Verifier.verify(apkPath);
            Certificate[][] signerCerts = new Certificate[][] { vSigner.certs };
            Signature[] signerSigs = convertToSignatures(signerCerts);
            Signature[] pastSignerSigs = null;
            int[] pastSignerSigsFlags = null;
            if (vSigner.por != null) {
                // populate proof-of-rotation information
                pastSignerSigs = new Signature[vSigner.por.certs.size()];
                pastSignerSigsFlags = new int[vSigner.por.flagsList.size()];
                for (int i = 0; i < pastSignerSigs.length; i++) {
                    pastSignerSigs[i] = new Signature(vSigner.por.certs.get(i).getEncoded());
                    pastSignerSigsFlags[i] = vSigner.por.flagsList.get(i);
                }
            }
            return new PackageParser.SigningDetails(
                    signerSigs, SignatureSchemeVersion.SIGNING_BLOCK_V3,
                    pastSignerSigs, pastSignerSigsFlags);
        } catch (SignatureNotFoundException e) {
            // not signed with v3, try older if allowed
            if (minSignatureSchemeVersion >= SignatureSchemeVersion.SIGNING_BLOCK_V3) {
                throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                        "No APK Signature Scheme v3 signature in package " + apkPath, e);
            }
        } catch (Exception e) {
            // APK Signature Scheme v2 signature found but did not verify
            throw new  PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "Failed to collect certificates from " + apkPath
                            + " using APK Signature Scheme v3", e);
        } finally {
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
        }

        // redundant, protective version check
        if (minSignatureSchemeVersion > SignatureSchemeVersion.SIGNING_BLOCK_V2) {
            // V2 and before are older than the requested minimum signing version
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "No signature found in package of version " + minSignatureSchemeVersion
                            + " or newer for package " + apkPath);
        }

        // try v2
        Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "verifyV2");
        try {
            Certificate[][] signerCerts = ApkSignatureSchemeV2Verifier.verify(apkPath);
            Signature[] signerSigs = convertToSignatures(signerCerts);

            return new PackageParser.SigningDetails(
                    signerSigs, SignatureSchemeVersion.SIGNING_BLOCK_V2);
        } catch (SignatureNotFoundException e) {
            // not signed with v2, try older if allowed
            if (minSignatureSchemeVersion >= SignatureSchemeVersion.SIGNING_BLOCK_V2) {
                throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                        "No APK Signature Scheme v2 signature in package " + apkPath, e);
            }
        } catch (Exception e) {
            // APK Signature Scheme v2 signature found but did not verify
            throw new  PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "Failed to collect certificates from " + apkPath
                            + " using APK Signature Scheme v2", e);
        } finally {
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
        }

        // redundant, protective version check
        if (minSignatureSchemeVersion > SignatureSchemeVersion.JAR) {
            // V1 and is older than the requested minimum signing version
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "No signature found in package of version " + minSignatureSchemeVersion
                            + " or newer for package " + apkPath);
        }

        // v2 didn't work, try jarsigner
        return verifyV1Signature(apkPath, true);
    }

    
Verifies the provided APK and returns the certificates associated with each signer.
Params:
verifyFull – whether to verify all contents of this APK or just collect certificates.
Throws:
PackageParserException – if there was a problem collecting certificates/**
     * Verifies the provided APK and returns the certificates associated with each signer.
     *
     * @param verifyFull whether to verify all contents of this APK or just collect certificates.
     *
     * @throws PackageParserException if there was a problem collecting certificates
     */
    private static PackageParser.SigningDetails verifyV1Signature(
            String apkPath, boolean verifyFull)
            throws PackageParserException {
        StrictJarFile jarFile = null;

        try {
            final Certificate[][] lastCerts;
            final Signature[] lastSigs;

            Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "strictJarFileCtor");

            // we still pass verify = true to ctor to collect certs, even though we're not checking
            // the whole jar.
            jarFile = new StrictJarFile(
                    apkPath,
                    true, // collect certs
                    verifyFull); // whether to reject APK with stripped v2 signatures (b/27887819)
            final List<ZipEntry> toVerify = new ArrayList<>();

            // Gather certs from AndroidManifest.xml, which every APK must have, as an optimization
            // to not need to verify the whole APK when verifyFUll == false.
            final ZipEntry manifestEntry = jarFile.findEntry(
                    PackageParser.ANDROID_MANIFEST_FILENAME);
            if (manifestEntry == null) {
                throw new PackageParserException(INSTALL_PARSE_FAILED_BAD_MANIFEST,
                        "Package " + apkPath + " has no manifest");
            }
            lastCerts = loadCertificates(jarFile, manifestEntry);
            if (ArrayUtils.isEmpty(lastCerts)) {
                throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES, "Package "
                        + apkPath + " has no certificates at entry "
                        + PackageParser.ANDROID_MANIFEST_FILENAME);
            }
            lastSigs = convertToSignatures(lastCerts);

            // fully verify all contents, except for AndroidManifest.xml  and the META-INF/ files.
            if (verifyFull) {
                final Iterator<ZipEntry> i = jarFile.iterator();
                while (i.hasNext()) {
                    final ZipEntry entry = i.next();
                    if (entry.isDirectory()) continue;

                    final String entryName = entry.getName();
                    if (entryName.startsWith("META-INF/")) continue;
                    if (entryName.equals(PackageParser.ANDROID_MANIFEST_FILENAME)) continue;

                    toVerify.add(entry);
                }

                for (ZipEntry entry : toVerify) {
                    final Certificate[][] entryCerts = loadCertificates(jarFile, entry);
                    if (ArrayUtils.isEmpty(entryCerts)) {
                        throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                                "Package " + apkPath + " has no certificates at entry "
                                        + entry.getName());
                    }

                    // make sure all entries use the same signing certs
                    final Signature[] entrySigs = convertToSignatures(entryCerts);
                    if (!Signature.areExactMatch(lastSigs, entrySigs)) {
                        throw new PackageParserException(
                                INSTALL_PARSE_FAILED_INCONSISTENT_CERTIFICATES,
                                "Package " + apkPath + " has mismatched certificates at entry "
                                        + entry.getName());
                    }
                }
            }
            return new PackageParser.SigningDetails(lastSigs, SignatureSchemeVersion.JAR);
        } catch (GeneralSecurityException e) {
            throw new PackageParserException(INSTALL_PARSE_FAILED_CERTIFICATE_ENCODING,
                    "Failed to collect certificates from " + apkPath, e);
        } catch (IOException | RuntimeException e) {
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "Failed to collect certificates from " + apkPath, e);
        } finally {
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
            closeQuietly(jarFile);
        }
    }

    private static Certificate[][] loadCertificates(StrictJarFile jarFile, ZipEntry entry)
            throws PackageParserException {
        InputStream is = null;
        try {
            // We must read the stream for the JarEntry to retrieve
            // its certificates.
            is = jarFile.getInputStream(entry);
            readFullyIgnoringContents(is);
            return jarFile.getCertificateChains(entry);
        } catch (IOException | RuntimeException e) {
            throw new PackageParserException(INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION,
                    "Failed reading " + entry.getName() + " in " + jarFile, e);
        } finally {
            IoUtils.closeQuietly(is);
        }
    }

    private static void readFullyIgnoringContents(InputStream in) throws IOException {
        byte[] buffer = sBuffer.getAndSet(null);
        if (buffer == null) {
            buffer = new byte[4096];
        }

        int n = 0;
        int count = 0;
        while ((n = in.read(buffer, 0, buffer.length)) != -1) {
            count += n;
        }

        sBuffer.set(buffer);
        return;
    }

    
Converts an array of certificate chains into the Signature equivalent used by the PackageManager. 
Throws:
CertificateEncodingException – if it is unable to create a Signature object./**
     * Converts an array of certificate chains into the {@code Signature} equivalent used by the
     * PackageManager.
     *
     * @throws CertificateEncodingException if it is unable to create a Signature object.
     */
    public static Signature[] convertToSignatures(Certificate[][] certs)
            throws CertificateEncodingException {
        final Signature[] res = new Signature[certs.length];
        for (int i = 0; i < certs.length; i++) {
            res[i] = new Signature(certs[i]);
        }
        return res;
    }

    private static void closeQuietly(StrictJarFile jarFile) {
        if (jarFile != null) {
            try {
                jarFile.close();
            } catch (Exception ignored) {
            }
        }
    }

    
Returns the certificates associated with each signer for the given APK without verification.
This method is dangerous and should not be used, unless the caller is absolutely certain the
APK is trusted.
Throws:
PackageParserException – if the APK's signature failed to verify.
or greater is not found, except in the case of no JAR signature./**
     * Returns the certificates associated with each signer for the given APK without verification.
     * This method is dangerous and should not be used, unless the caller is absolutely certain the
     * APK is trusted.
     *
     * @throws PackageParserException if the APK's signature failed to verify.
     * or greater is not found, except in the case of no JAR signature.
     */
    public static PackageParser.SigningDetails plsCertsNoVerifyOnlyCerts(
            String apkPath, int minSignatureSchemeVersion)
            throws PackageParserException {

        if (minSignatureSchemeVersion > SignatureSchemeVersion.SIGNING_BLOCK_V3) {
            // V3 and before are older than the requested minimum signing version
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "No signature found in package of version " + minSignatureSchemeVersion
                            + " or newer for package " + apkPath);
        }

        // first try v3
        Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "certsOnlyV3");
        try {
            ApkSignatureSchemeV3Verifier.VerifiedSigner vSigner =
                    ApkSignatureSchemeV3Verifier.plsCertsNoVerifyOnlyCerts(apkPath);
            Certificate[][] signerCerts = new Certificate[][] { vSigner.certs };
            Signature[] signerSigs = convertToSignatures(signerCerts);
            Signature[] pastSignerSigs = null;
            int[] pastSignerSigsFlags = null;
            if (vSigner.por != null) {
                // populate proof-of-rotation information
                pastSignerSigs = new Signature[vSigner.por.certs.size()];
                pastSignerSigsFlags = new int[vSigner.por.flagsList.size()];
                for (int i = 0; i < pastSignerSigs.length; i++) {
                    pastSignerSigs[i] = new Signature(vSigner.por.certs.get(i).getEncoded());
                    pastSignerSigsFlags[i] = vSigner.por.flagsList.get(i);
                }
            }
            return new PackageParser.SigningDetails(
                    signerSigs, SignatureSchemeVersion.SIGNING_BLOCK_V3,
                    pastSignerSigs, pastSignerSigsFlags);
        } catch (SignatureNotFoundException e) {
            // not signed with v3, try older if allowed
            if (minSignatureSchemeVersion >= SignatureSchemeVersion.SIGNING_BLOCK_V3) {
                throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                        "No APK Signature Scheme v3 signature in package " + apkPath, e);
            }
        } catch (Exception e) {
            // APK Signature Scheme v3 signature found but did not verify
            throw new  PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "Failed to collect certificates from " + apkPath
                            + " using APK Signature Scheme v3", e);
        } finally {
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
        }

        // redundant, protective version check
        if (minSignatureSchemeVersion > SignatureSchemeVersion.SIGNING_BLOCK_V2) {
            // V2 and before are older than the requested minimum signing version
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "No signature found in package of version " + minSignatureSchemeVersion
                            + " or newer for package " + apkPath);
        }

        // first try v2
        Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "certsOnlyV2");
        try {
            Certificate[][] signerCerts =
                    ApkSignatureSchemeV2Verifier.plsCertsNoVerifyOnlyCerts(apkPath);
            Signature[] signerSigs = convertToSignatures(signerCerts);
            return new PackageParser.SigningDetails(signerSigs,
                    SignatureSchemeVersion.SIGNING_BLOCK_V2);
        } catch (SignatureNotFoundException e) {
            // not signed with v2, try older if allowed
            if (minSignatureSchemeVersion >= SignatureSchemeVersion.SIGNING_BLOCK_V2) {
                throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                        "No APK Signature Scheme v2 signature in package " + apkPath, e);
            }
        } catch (Exception e) {
            // APK Signature Scheme v2 signature found but did not verify
            throw new  PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "Failed to collect certificates from " + apkPath
                            + " using APK Signature Scheme v2", e);
        } finally {
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
        }

        // redundant, protective version check
        if (minSignatureSchemeVersion > SignatureSchemeVersion.JAR) {
            // V1 and is older than the requested minimum signing version
            throw new PackageParserException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
                    "No signature found in package of version " + minSignatureSchemeVersion
                            + " or newer for package " + apkPath);
        }

        // v2 didn't work, try jarsigner
        return verifyV1Signature(apkPath, false);
    }

    
Returns:
the verity root hash in the Signing Block./**
     * @return the verity root hash in the Signing Block.
     */
    public static byte[] getVerityRootHash(String apkPath)
            throws IOException, SignatureNotFoundException, SecurityException {
        // first try v3
        try {
            return ApkSignatureSchemeV3Verifier.getVerityRootHash(apkPath);
        } catch (SignatureNotFoundException e) {
            // try older version
        }
        return ApkSignatureSchemeV2Verifier.getVerityRootHash(apkPath);
    }

    
Generates the Merkle tree and verity metadata to the buffer allocated by the 
ByteBufferFactory. 
Returns:
the verity root hash of the generated Merkle tree./**
     * Generates the Merkle tree and verity metadata to the buffer allocated by the {@code
     * ByteBufferFactory}.
     *
     * @return the verity root hash of the generated Merkle tree.
     */
    public static byte[] generateApkVerity(String apkPath, ByteBufferFactory bufferFactory)
            throws IOException, SignatureNotFoundException, SecurityException, DigestException,
                   NoSuchAlgorithmException {
        // first try v3
        try {
            return ApkSignatureSchemeV3Verifier.generateApkVerity(apkPath, bufferFactory);
        } catch (SignatureNotFoundException e) {
            // try older version
        }
        return ApkSignatureSchemeV2Verifier.generateApkVerity(apkPath, bufferFactory);
    }

    
Generates the FSVerity root hash from FSVerity header, extensions and Merkle tree root hash
in Signing Block.
Returns:
FSverity root hash/**
     * Generates the FSVerity root hash from FSVerity header, extensions and Merkle tree root hash
     * in Signing Block.
     *
     * @return FSverity root hash
     */
    public static byte[] generateFsverityRootHash(String apkPath)
            throws NoSuchAlgorithmException, DigestException, IOException {
        // first try v3
        try {
            return ApkSignatureSchemeV3Verifier.generateFsverityRootHash(apkPath);
        } catch (SignatureNotFoundException e) {
            // try older version
        }
        try {
            return ApkSignatureSchemeV2Verifier.generateFsverityRootHash(apkPath);
        } catch (SignatureNotFoundException e) {
            return null;
        }
    }

    
Result of a successful APK verification operation.
/**
     * Result of a successful APK verification operation.
     */
    public static class Result {
        public final Certificate[][] certs;
        public final Signature[] sigs;
        public final int signatureSchemeVersion;

        public Result(Certificate[][] certs, Signature[] sigs, int signingVersion) {
            this.certs = certs;
            this.sigs = sigs;
            this.signatureSchemeVersion = signingVersion;
        }
    }
}