/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.content.pm;

import static android.content.pm.SigningDetails.SignatureSchemeVersion;

import android.annotation.FlaggedApi;
import android.annotation.IntDef;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.SystemApi;
import android.content.pm.SigningDetails.SignatureSchemeVersion;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.ArraySet;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.security.PublicKey;
import java.util.Collection;

/**
 * Information pertaining to the signing certificates used to sign a package.
 */
public final class SigningInfo implements Parcelable {
    /**
     * JAR signing (v1 scheme).
     * See https://source.android.com/docs/security/features/apksigning#v1.
     *
     * @hide
     */
    @FlaggedApi(Flags.FLAG_CLOUD_COMPILATION_PM)
    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
    public static final int VERSION_JAR = SignatureSchemeVersion.JAR;

    /**
     * APK signature scheme v2.
     * See https://source.android.com/docs/security/features/apksigning/v2.
     *
     * @hide
     */
    @FlaggedApi(Flags.FLAG_CLOUD_COMPILATION_PM)
    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
    public static final int VERSION_SIGNING_BLOCK_V2 = SignatureSchemeVersion.SIGNING_BLOCK_V2;

    /**
     * APK signature scheme v3.
     * See https://source.android.com/docs/security/features/apksigning/v3.
     *
     * @hide
     */
    @FlaggedApi(Flags.FLAG_CLOUD_COMPILATION_PM)
    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
    public static final int VERSION_SIGNING_BLOCK_V3 = SignatureSchemeVersion.SIGNING_BLOCK_V3;

    /**
     * APK signature scheme v4.
     * See https://source.android.com/docs/security/features/apksigning/v4.
     *
     * @hide
     */
    @FlaggedApi(Flags.FLAG_CLOUD_COMPILATION_PM)
    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
    public static final int VERSION_SIGNING_BLOCK_V4 = SignatureSchemeVersion.SIGNING_BLOCK_V4;

    /** @hide */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef(prefix = {"VERSION_"}, value = {
            VERSION_JAR,
            VERSION_SIGNING_BLOCK_V2,
            VERSION_SIGNING_BLOCK_V3,
            VERSION_SIGNING_BLOCK_V4,
    })
    public @interface AppSigningSchemeVersion {}

    @NonNull
    private final SigningDetails mSigningDetails;

    public SigningInfo() {
        mSigningDetails = SigningDetails.UNKNOWN;
    }

    /**
     * Creates a new instance of information used to sign the APK.
     *
     * @param schemeVersion version of signing schema.
     * @param apkContentsSigners signing certificates.
     * @param publicKeys for the signing certificates.
     * @param signingCertificateHistory All signing certificates the package has proven it is
     *                                  authorized to use.
     *
     * @see
     * <a href="https://source.android.com/docs/security/features/apksigning#schemes">APK signing
     * schemas</a>
     */
    @FlaggedApi(Flags.FLAG_ARCHIVING)
    public SigningInfo(@SignatureSchemeVersion int schemeVersion,
            @Nullable Collection<Signature> apkContentsSigners,
            @Nullable Collection<PublicKey> publicKeys,
            @Nullable Collection<Signature> signingCertificateHistory) {
        if (schemeVersion <= 0 || apkContentsSigners == null) {
            mSigningDetails = SigningDetails.UNKNOWN;
            return;
        }
        Signature[] signatures = apkContentsSigners != null && !apkContentsSigners.isEmpty()
                ? apkContentsSigners.toArray(new Signature[apkContentsSigners.size()])
                : null;
        Signature[] pastSignatures =
                signingCertificateHistory != null && !signingCertificateHistory.isEmpty()
                ? signingCertificateHistory.toArray(new Signature[signingCertificateHistory.size()])
                : null;
        if (Signature.areExactArraysMatch(signatures, pastSignatures)) {
            pastSignatures = null;
        }
        ArraySet<PublicKey> keys =
                publicKeys != null && !publicKeys.isEmpty() ? new ArraySet<>(publicKeys) : null;
        mSigningDetails = new SigningDetails(signatures, schemeVersion, keys, pastSignatures);
    }

    /**
     * @hide only packagemanager should be populating this
     */
    public SigningInfo(SigningDetails signingDetails) {
        mSigningDetails = new SigningDetails(signingDetails);
    }

    public SigningInfo(SigningInfo orig) {
        mSigningDetails = new SigningDetails(orig.mSigningDetails);
    }

    private SigningInfo(Parcel source) {
        mSigningDetails = SigningDetails.CREATOR.createFromParcel(source);
    }

    /**
     * Although relatively uncommon, packages may be signed by more than one signer, in which case
     * their identity is viewed as being the set of all signers, not just any one.
     */
    public boolean hasMultipleSigners() {
        return mSigningDetails.getSignatures() != null
                && mSigningDetails.getSignatures().length > 1;
    }

    /**
     * APK Signature Scheme v3 enables packages to provide a proof-of-rotation record that the
     * platform verifies, and uses, to allow the use of new signing certificates.  This is only
     * available to packages that are not signed by multiple signers.  In the event of a change to a
     * new signing certificate, the package's past signing certificates are presented as well.  Any
     * check of a package's signing certificate should also include a search through its entire
     * signing history, since it could change to a new signing certificate at any time.
     */
    public boolean hasPastSigningCertificates() {
        return mSigningDetails.getPastSigningCertificates() != null
                && mSigningDetails.getPastSigningCertificates().length > 0;
    }

    /**
     * Returns the signing certificates this package has proven it is authorized to use. This
     * includes both the signing certificate associated with the signer of the package and the past
     * signing certificates it included as its proof of signing certificate rotation.  Signing
     * certificates are returned in the order of rotation with the original signing certificate at
     * index 0, and the current signing certificate at the last index. This method is the preferred
     * replacement for the {@code GET_SIGNATURES} flag used with {@link
     * PackageManager#getPackageInfo(String, int)}. When determining if a package is signed by a
     * desired certificate, the returned array should be checked to determine if it is one of the
     * entries.
     *
     * <note>
     *     This method returns null if the package is signed by multiple signing certificates, as
     *     opposed to being signed by one current signer and also providing the history of past
     *     signing certificates.  {@link #hasMultipleSigners()} may be used to determine if this
     *     package is signed by multiple signers.  Packages which are signed by multiple signers
     *     cannot change their signing certificates and their {@code Signature} array should be
     *     checked to make sure that every entry matches the looked-for signing certificates.
     * </note>
     */
    public Signature[] getSigningCertificateHistory() {
        if (hasMultipleSigners()) {
            return null;
        } else if (!hasPastSigningCertificates()) {

            // this package is only signed by one signer with no history, return it
            return mSigningDetails.getSignatures();
        } else {

            // this package has provided proof of past signing certificates, include them
            return mSigningDetails.getPastSigningCertificates();
        }
    }

    /**
     * Returns the signing certificates used to sign the APK contents of this application.  Not
     * including any past signing certificates the package proved it is authorized to use.
     * <note>
     *     This method should not be used unless {@link #hasMultipleSigners()} returns true,
     *     indicating that {@link #getSigningCertificateHistory()} cannot be used, otherwise {@link
     *     #getSigningCertificateHistory()} should be preferred.
     * </note>
     */
    public Signature[] getApkContentsSigners() {
        return mSigningDetails.getSignatures();
    }

    /**
     * Returns the version of signing schema used to sign the APK.
     *
     * @see
     * <a href="https://source.android.com/docs/security/features/apksigning#schemes">APK signing
     * schemas</a>
     */
    @FlaggedApi(Flags.FLAG_ARCHIVING)
    public @SignatureSchemeVersion int getSchemeVersion() {
        return mSigningDetails.getSignatureSchemeVersion();
    }

    /**
     * Returns the public keys for the signing certificates.
     */
    @FlaggedApi(Flags.FLAG_ARCHIVING)
    public @NonNull Collection<PublicKey> getPublicKeys() {
        return mSigningDetails.getPublicKeys();
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int parcelableFlags) {
        mSigningDetails.writeToParcel(dest, parcelableFlags);
    }

    /**
     *  @hide
     */
    @NonNull
    public SigningDetails getSigningDetails() {
        return mSigningDetails;
    }

    /**
     * Returns true if the signing certificates in this and other match exactly.
     *
     * @hide
     */
    @FlaggedApi(Flags.FLAG_CLOUD_COMPILATION_PM)
    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
    public boolean signersMatchExactly(@NonNull SigningInfo other) {
        return mSigningDetails.signaturesMatchExactly(other.mSigningDetails);
    }

    public static final @android.annotation.NonNull Parcelable.Creator<SigningInfo> CREATOR =
            new Parcelable.Creator<SigningInfo>() {
        @Override
        public SigningInfo createFromParcel(Parcel source) {
            return new SigningInfo(source);
        }

        @Override
        public SigningInfo[] newArray(int size) {
            return new SigningInfo[size];
        }
    };
}