Reintroduce pgp-certificate-store layer

pgp-certificate-store/README.md

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+<!--
+SPDX-FileCopyrightText: 2022 Paul Schaub <info@pgpainless.org>
+
+SPDX-License-Identifier: Apache-2.0
+-->
+
+# PGP Certificate Store Definitions
+
+[![javadoc](https://javadoc.io/badge2/org.pgpainless/pgp-certificate-store/javadoc.svg)](https://javadoc.io/doc/org.pgpainless/pgp-certificate-store)
+[![Maven Central](https://badgen.net/maven/v/maven-central/org.pgpainless/pgp-certificate-store)](https://search.maven.org/artifact/org.pgpainless/pgp-certificate-store)
+
+This module contains API definitions for an OpenPGP certificate store.
+A certificate store is used to store public key certificates only.

pgp-certificate-store/build.gradle

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+// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+plugins {
+    id 'java-library'
+}
+
+group 'org.pgpainless'
+
+repositories {
+    mavenCentral()
+}
+
+apply plugin: 'ru.vyarus.animalsniffer'
+
+dependencies {
+    // animal sniffer for ensuring Android API compatibility
+    signature "net.sf.androidscents.signature:android-api-level-${minAndroidSdk}:2.3.3_r2@signature"
+
+    // JUnit for testing
+    testImplementation "org.junit.jupiter:junit-jupiter-api:$junitVersion"
+    testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junitVersion"
+
+    // Logging
+    api "org.slf4j:slf4j-api:$slf4jVersion"
+    testImplementation "ch.qos.logback:logback-classic:$logbackVersion"
+}
+
+animalsniffer {
+    sourceSets = [sourceSets.main]
+}
+
+test {
+    useJUnitPlatform()
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/PGPCertificateStore.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store;
+
+import pgp.certificate_store.certificate.Certificate;
+import pgp.certificate_store.certificate.KeyMaterialMerger;
+import pgp.certificate_store.exception.BadDataException;
+import pgp.certificate_store.exception.BadNameException;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Iterator;
+
+/**
+ * Interface for an OpenPGP certificate (public key) store.
+ */
+public interface PGPCertificateStore {
+
+    /**
+     * Return the certificate that matches the given identifier.
+     * If no matching certificate can be found, return null.
+     *
+     * @param identifier identifier for a certificate.
+     * @return certificate or null
+     *
+     * @throws IOException in case of an IO-error
+     * @throws BadNameException if the identifier is invalid
+     * @throws BadDataException if the certificate file contains invalid data
+     */
+    Certificate getCertificate(String identifier)
+            throws IOException, BadNameException, BadDataException;
+
+    /**
+     * Return an {@link Iterator} over all certificates in the store that contain a subkey with the given
+     * subkey id.
+     * @param subkeyId id of the subkey
+     * @return iterator
+     *
+     * @throws IOException in case of an IO error
+     * @throws BadDataException if any of the certificate files contains invalid data
+     */
+    Iterator<Certificate> getCertificatesBySubkeyId(long subkeyId)
+        throws IOException, BadDataException;
+
+    /**
+     * Insert a certificate into the store.
+     * If an instance of the certificate is already present in the store, the given {@link KeyMaterialMerger} will be
+     * used to merge both the existing and the new instance of the {@link Certificate}. The resulting merged certificate
+     * will be stored in the store and returned.
+     *
+     * This method will block until a write-lock on the store can be acquired.
+     *
+     * @param data input stream containing the new certificate instance
+     * @param merge callback for merging with an existing certificate instance
+     * @return merged certificate
+     *
+     * @throws IOException in case of an IO-error
+     * @throws InterruptedException in case the inserting thread gets interrupted
+     * @throws BadDataException if the data stream does not contain valid OpenPGP data
+     */
+    Certificate insertCertificate(InputStream data, KeyMaterialMerger merge)
+            throws IOException, InterruptedException, BadDataException;
+
+    /**
+     * Insert a certificate into the store.
+     * The certificate will be stored under the given special name instead of its fingerprint.
+     *
+     * If an instance of the certificate is already present under the special name in the store, the given {@link KeyMaterialMerger} will be
+     * used to merge both the existing and the new instance of the {@link Certificate}. The resulting merged certificate
+     * will be stored in the store and returned.
+     *
+     * This method will block until a write-lock on the store can be acquired.
+     *
+     * @param specialName special name of the certificate
+     * @param data input stream containing the new certificate instance
+     * @param merge callback for merging with an existing certificate instance
+     * @return merged certificate or null if the store cannot be locked
+     *
+     * @throws IOException in case of an IO-error
+     * @throws InterruptedException if the thread is interrupted
+     * @throws BadDataException if the certificate file does not contain valid OpenPGP data
+     * @throws BadNameException if the special name is unknown
+     */
+    Certificate insertCertificateBySpecialName(String specialName, InputStream data, KeyMaterialMerger merge)
+            throws IOException, InterruptedException, BadDataException, BadNameException;
+
+    /**
+     * Return an {@link Iterator} containing all certificates in the store.
+     * The iterator will contain both certificates addressed by special names and by fingerprints.
+     *
+     * @return certificates
+     */
+    Iterator<Certificate> getCertificates();
+
+    /**
+     * Return an {@link Iterator} containing all certificate fingerprints from the store.
+     * Note that this only includes the fingerprints of certificate primary keys, not those of subkeys.
+     *
+     * @return fingerprints
+     */
+    Iterator<String> getFingerprints();
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/certificate/Certificate.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.certificate;
+
+/**
+ * OpenPGP certificate (public key).
+ */
+public abstract class Certificate implements KeyMaterial {
+
+    @Override
+    public Certificate asCertificate() {
+        return this;
+    }
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/certificate/Key.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.certificate;
+
+/**
+ * OpenPGP key (secret key).
+ */
+public abstract class Key implements KeyMaterial {
+
+    /**
+     * Return the certificate part of this OpenPGP key.
+     *
+     * @return OpenPGP certificate
+     */
+    public abstract Certificate getCertificate();
+
+    @Override
+    public Certificate asCertificate() {
+        return getCertificate();
+    }
+
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/certificate/KeyMaterial.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.certificate;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.List;
+import java.util.Set;
+
+public interface KeyMaterial {
+
+    /**
+     * Return the fingerprint of the certificate as 40 lowercase hex characters.
+     * TODO: Allow OpenPGP V5 fingerprints
+     *
+     * @return fingerprint
+     */
+    String getFingerprint();
+
+    Certificate asCertificate();
+
+    /**
+     * Return an {@link InputStream} of the binary representation of the secret key.
+     *
+     * @return input stream
+     * @throws IOException in case of an IO error
+     */
+    InputStream getInputStream() throws IOException;
+
+    String getTag() throws IOException;
+
+    /**
+     * Return a {@link Set} containing key-ids of subkeys.
+     *
+     * @return subkeys
+     * @throws IOException in case of an IO error
+     */
+    List<Long> getSubkeyIds() throws IOException;
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/certificate/KeyMaterialMerger.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.certificate;
+
+import java.io.IOException;
+
+/**
+ * Merge a given {@link Key} (update) with an existing {@link Key}.
+ */
+public interface KeyMaterialMerger {
+
+    /**
+     * Merge the given key material with an existing copy and return the result.
+     * If no existing {@link KeyMaterial} is found (i.e. if existing is null), this method returns the unmodified data.
+     *
+     * @param data key material
+     * @param existing optional already existing copy of the key material
+     * @return merged key material
+     *
+     * @throws IOException in case of an IO error
+     */
+    KeyMaterial merge(KeyMaterial data, KeyMaterial existing) throws IOException;
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/certificate/KeyMaterialReaderBackend.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.certificate;
+
+import pgp.certificate_store.exception.BadDataException;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public interface KeyMaterialReaderBackend {
+
+    /**
+     * Read a {@link KeyMaterial} (either {@link Key} or {@link Certificate}) from the given {@link InputStream}.
+     *
+     * @param data input stream containing the binary representation of the key.
+     * @return key or certificate object
+     *
+     * @throws IOException in case of an IO error
+     * @throws BadDataException in case that the data stream does not contain a valid OpenPGP key/certificate
+     */
+    KeyMaterial read(InputStream data) throws IOException, BadDataException;
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/certificate/package-info.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * General OpenPGP Certificate Storage related classes.
+ */
+package pgp.certificate_store.certificate;

pgp-certificate-store/src/main/java/pgp/certificate_store/exception/BadDataException.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.exception;
+
+/**
+ * The data was not a valid OpenPGP cert or key in binary format.
+ */
+public class BadDataException extends Exception {
+
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/exception/BadNameException.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.exception;
+
+/**
+ * Provided name was neither a valid fingerprint, nor a known special name.
+ */
+public class BadNameException extends Exception {
+
+    public BadNameException() {
+        super();
+    }
+
+    public BadNameException(String message) {
+        super(message);
+    }
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/exception/NotAStoreException.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store.exception;
+
+/**
+ * The base dir cannot possibly contain a store.
+ */
+public class NotAStoreException extends Exception {
+
+    public NotAStoreException() {
+        super();
+    }
+
+    public NotAStoreException(String message) {
+        super(message);
+    }
+}

pgp-certificate-store/src/main/java/pgp/certificate_store/exception/package-info.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Exceptions.
+ */
+package pgp.certificate_store.exception;

pgp-certificate-store/src/main/java/pgp/certificate_store/package-info.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Abstract definitions of an OpenPGP certificate store.
+ */
+package pgp.certificate_store;

pgp-certificate-store/src/test/java/pgp/certificate_store/DummyTest.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.certificate_store;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class DummyTest {
+    @Test
+    public void test() {
+        assertTrue(true);
+    }
+}