/*
 * Copyright (C) 2013 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.jar;

import android.system.ErrnoException;
import android.system.Os;
import android.system.OsConstants;

import dalvik.system.CloseGuard;
import java.io.FileDescriptor;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.cert.Certificate;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
import java.util.jar.JarFile;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import java.util.zip.ZipEntry;
import libcore.io.IoBridge;
import libcore.io.IoUtils;
import libcore.io.Streams;

/**
 * A subset of the JarFile API implemented as a thin wrapper over
 * system/core/libziparchive.
 *
 * @hide for internal use only. Not API compatible (or as forgiving) as
 *        {@link java.util.jar.JarFile}
 */
public final class StrictJarFile {

    private final long nativeHandle;

    // NOTE: It's possible to share a file descriptor with the native
    // code, at the cost of some additional complexity.
    private final FileDescriptor fd;

    private final StrictJarManifest manifest;
    private final StrictJarVerifier verifier;

    private final boolean isSigned;

    private final CloseGuard guard = CloseGuard.get();
    private boolean closed;

    public StrictJarFile(String fileName)
            throws IOException, SecurityException {
        this(fileName, true, true);
    }

    public StrictJarFile(FileDescriptor fd)
            throws IOException, SecurityException {
        this(fd, true, true);
    }

    public StrictJarFile(FileDescriptor fd,
            boolean verify,
            boolean signatureSchemeRollbackProtectionsEnforced)
                    throws IOException, SecurityException {
        this("[fd:" + fd.getInt$() + "]", fd, verify,
                signatureSchemeRollbackProtectionsEnforced);
    }

    public StrictJarFile(String fileName,
            boolean verify,
            boolean signatureSchemeRollbackProtectionsEnforced)
                    throws IOException, SecurityException {
        this(fileName, IoBridge.open(fileName, OsConstants.O_RDONLY),
                verify, signatureSchemeRollbackProtectionsEnforced);
    }

    /**
     * @param name of the archive (not necessarily a path).
     * @param fd seekable file descriptor for the JAR file.
     * @param verify whether to verify the file's JAR signatures and collect the corresponding
     *        signer certificates.
     * @param signatureSchemeRollbackProtectionsEnforced {@code true} to enforce protections against
     *        stripping newer signature schemes (e.g., APK Signature Scheme v2) from the file, or
     *        {@code false} to ignore any such protections. This parameter is ignored when
     *        {@code verify} is {@code false}.
     */
    private StrictJarFile(String name,
            FileDescriptor fd,
            boolean verify,
            boolean signatureSchemeRollbackProtectionsEnforced)
                    throws IOException, SecurityException {
        this.nativeHandle = nativeOpenJarFile(name, fd.getInt$());
        this.fd = fd;

        try {
            // Read the MANIFEST and signature files up front and try to
            // parse them. We never want to accept a JAR File with broken signatures
            // or manifests, so it's best to throw as early as possible.
            if (verify) {
                HashMap<String, byte[]> metaEntries = getMetaEntries();
                this.manifest = new StrictJarManifest(metaEntries.get(JarFile.MANIFEST_NAME), true);
                this.verifier =
                        new StrictJarVerifier(
                                name,
                                manifest,
                                metaEntries,
                                signatureSchemeRollbackProtectionsEnforced);
                Set<String> files = manifest.getEntries().keySet();
                for (String file : files) {
                    if (findEntry(file) == null) {
                        throw new SecurityException("File " + file + " in manifest does not exist");
                    }
                }

                isSigned = verifier.readCertificates() && verifier.isSignedJar();
            } else {
                isSigned = false;
                this.manifest = null;
                this.verifier = null;
            }
        } catch (IOException | SecurityException e) {
            nativeClose(this.nativeHandle);
            IoUtils.closeQuietly(fd);
            closed = true;
            throw e;
        }

        guard.open("close");
    }

    public StrictJarManifest getManifest() {
        return manifest;
    }

    public Iterator<ZipEntry> iterator() throws IOException {
        return new EntryIterator(nativeHandle, "");
    }

    public ZipEntry findEntry(String name) {
        return nativeFindEntry(nativeHandle, name);
    }

    /**
     * Return all certificate chains for a given {@link ZipEntry} belonging to this jar.
     * This method MUST be called only after fully exhausting the InputStream belonging
     * to this entry.
     *
     * Returns {@code null} if this jar file isn't signed or if this method is
     * called before the stream is processed.
     */
    public Certificate[][] getCertificateChains(ZipEntry ze) {
        if (isSigned) {
            return verifier.getCertificateChains(ze.getName());
        }

        return null;
    }

    /**
     * Return all certificates for a given {@link ZipEntry} belonging to this jar.
     * This method MUST be called only after fully exhausting the InputStream belonging
     * to this entry.
     *
     * Returns {@code null} if this jar file isn't signed or if this method is
     * called before the stream is processed.
     *
     * @deprecated Switch callers to use getCertificateChains instead
     */
    @Deprecated
    public Certificate[] getCertificates(ZipEntry ze) {
        if (isSigned) {
            Certificate[][] certChains = verifier.getCertificateChains(ze.getName());

            // Measure number of certs.
            int count = 0;
            for (Certificate[] chain : certChains) {
                count += chain.length;
            }

            // Create new array and copy all the certs into it.
            Certificate[] certs = new Certificate[count];
            int i = 0;
            for (Certificate[] chain : certChains) {
                System.arraycopy(chain, 0, certs, i, chain.length);
                i += chain.length;
            }

            return certs;
        }

        return null;
    }

    public InputStream getInputStream(ZipEntry ze) {
        final InputStream is = getZipInputStream(ze);

        if (isSigned) {
            StrictJarVerifier.VerifierEntry entry = verifier.initEntry(ze.getName());
            if (entry == null) {
                return is;
            }

            return new JarFileInputStream(is, ze.getSize(), entry);
        }

        return is;
    }

    public void close() throws IOException {
        if (!closed) {
            if (guard != null) {
                guard.close();
            }

            nativeClose(nativeHandle);
            IoUtils.closeQuietly(fd);
            closed = true;
        }
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            if (guard != null) {
                guard.warnIfOpen();
            }
            close();
        } finally {
            super.finalize();
        }
    }

    private InputStream getZipInputStream(ZipEntry ze) {
        if (ze.getMethod() == ZipEntry.STORED) {
            return new FDStream(fd, ze.getDataOffset(),
                    ze.getDataOffset() + ze.getSize());
        } else {
            final FDStream wrapped = new FDStream(
                    fd, ze.getDataOffset(), ze.getDataOffset() + ze.getCompressedSize());

            int bufSize = Math.max(1024, (int) Math.min(ze.getSize(), 65535L));
            return new ZipInflaterInputStream(wrapped, new Inflater(true), bufSize, ze);
        }
    }

    static final class EntryIterator implements Iterator<ZipEntry> {
        private final long iterationHandle;
        private ZipEntry nextEntry;

        EntryIterator(long nativeHandle, String prefix) throws IOException {
            iterationHandle = nativeStartIteration(nativeHandle, prefix);
        }

        public ZipEntry next() {
            if (nextEntry != null) {
                final ZipEntry ze = nextEntry;
                nextEntry = null;
                return ze;
            }

            return nativeNextEntry(iterationHandle);
        }

        public boolean hasNext() {
            if (nextEntry != null) {
                return true;
            }

            final ZipEntry ze = nativeNextEntry(iterationHandle);
            if (ze == null) {
                return false;
            }

            nextEntry = ze;
            return true;
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    private HashMap<String, byte[]> getMetaEntries() throws IOException {
        HashMap<String, byte[]> metaEntries = new HashMap<String, byte[]>();

        Iterator<ZipEntry> entryIterator = new EntryIterator(nativeHandle, "META-INF/");
        while (entryIterator.hasNext()) {
            final ZipEntry entry = entryIterator.next();
            metaEntries.put(entry.getName(), Streams.readFully(getInputStream(entry)));
        }

        return metaEntries;
    }

    static final class JarFileInputStream extends FilterInputStream {
        private final StrictJarVerifier.VerifierEntry entry;

        private long count;
        private boolean done = false;

        JarFileInputStream(InputStream is, long size, StrictJarVerifier.VerifierEntry e) {
            super(is);
            entry = e;

            count = size;
        }

        @Override
        public int read() throws IOException {
            if (done) {
                return -1;
            }
            if (count > 0) {
                int r = super.read();
                if (r != -1) {
                    entry.write(r);
                    count--;
                } else {
                    count = 0;
                }
                if (count == 0) {
                    done = true;
                    entry.verify();
                }
                return r;
            } else {
                done = true;
                entry.verify();
                return -1;
            }
        }

        @Override
        public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
            if (done) {
                return -1;
            }
            if (count > 0) {
                int r = super.read(buffer, byteOffset, byteCount);
                if (r != -1) {
                    int size = r;
                    if (count < size) {
                        size = (int) count;
                    }
                    entry.write(buffer, byteOffset, size);
                    count -= size;
                } else {
                    count = 0;
                }
                if (count == 0) {
                    done = true;
                    entry.verify();
                }
                return r;
            } else {
                done = true;
                entry.verify();
                return -1;
            }
        }

        @Override
        public int available() throws IOException {
            if (done) {
                return 0;
            }
            return super.available();
        }

        @Override
        public long skip(long byteCount) throws IOException {
            return Streams.skipByReading(this, byteCount);
        }
    }

    /** @hide */
    public static class ZipInflaterInputStream extends InflaterInputStream {
        private final ZipEntry entry;
        private long bytesRead = 0;

        public ZipInflaterInputStream(InputStream is, Inflater inf, int bsize, ZipEntry entry) {
            super(is, inf, bsize);
            this.entry = entry;
        }

        @Override public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
            final int i;
            try {
                i = super.read(buffer, byteOffset, byteCount);
            } catch (IOException e) {
                throw new IOException("Error reading data for " + entry.getName() + " near offset "
                        + bytesRead, e);
            }
            if (i == -1) {
                if (entry.getSize() != bytesRead) {
                    throw new IOException("Size mismatch on inflated file: " + bytesRead + " vs "
                            + entry.getSize());
                }
            } else {
                bytesRead += i;
            }
            return i;
        }

        @Override public int available() throws IOException {
            if (closed) {
                // Our superclass will throw an exception, but there's a jtreg test that
                // explicitly checks that the InputStream returned from ZipFile.getInputStream
                // returns 0 even when closed.
                return 0;
            }
            return super.available() == 0 ? 0 : (int) (entry.getSize() - bytesRead);
        }
    }

    /**
     * Wrap a stream around a FileDescriptor.  The file descriptor is shared
     * among all streams returned by getInputStream(), so we have to synchronize
     * access to it.  (We can optimize this by adding buffering here to reduce
     * collisions.)
     *
     * <p>We could support mark/reset, but we don't currently need them.
     *
     * @hide
     */
    public static class FDStream extends InputStream {
        private final FileDescriptor fd;
        private long endOffset;
        private long offset;

        public FDStream(FileDescriptor fd, long initialOffset, long endOffset) {
            this.fd = fd;
            offset = initialOffset;
            this.endOffset = endOffset;
        }

        @Override public int available() throws IOException {
            return (offset < endOffset ? 1 : 0);
        }

        @Override public int read() throws IOException {
            return Streams.readSingleByte(this);
        }

        @Override public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
            synchronized (this.fd) {
                final long length = endOffset - offset;
                if (byteCount > length) {
                    byteCount = (int) length;
                }
                try {
                    Os.lseek(fd, offset, OsConstants.SEEK_SET);
                } catch (ErrnoException e) {
                    throw new IOException(e);
                }
                int count = IoBridge.read(fd, buffer, byteOffset, byteCount);
                if (count > 0) {
                    offset += count;
                    return count;
                } else {
                    return -1;
                }
            }
        }

        @Override public long skip(long byteCount) throws IOException {
            if (byteCount > endOffset - offset) {
                byteCount = endOffset - offset;
            }
            offset += byteCount;
            return byteCount;
        }
    }

    private static native long nativeOpenJarFile(String name, int fd)
            throws IOException;
    private static native long nativeStartIteration(long nativeHandle, String prefix);
    private static native ZipEntry nativeNextEntry(long iterationHandle);
    private static native ZipEntry nativeFindEntry(long nativeHandle, String entryName);
    private static native void nativeClose(long nativeHandle);
}