Initial implementation of WKD address generation

settings.gradle

@@ -6,5 +6,6 @@ rootProject.name = 'PGPainless'
 
 include 'pgpainless-core',
         'pgpainless-sop',
-        'pgpainless-cli'
+        'pgpainless-cli',
+        'wkd-java'
 

wkd-java/build.gradle

@@ -0,0 +1,28 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+plugins {
+    id 'java-library'
+}
+
+group 'org.pgpainless'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation "org.junit.jupiter:junit-jupiter-api:$junitVersion"
+    testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junitVersion"
+
+    // Logging
+    testImplementation "ch.qos.logback:logback-classic:$logbackVersion"
+
+    // Z-Base32
+    implementation 'com.sandinh:zbase32-commons-codec:1.0.0'
+}
+
+test {
+    useJUnitPlatform()
+}

wkd-java/src/main/java/pgp/wkd/UserIdToWKDAddress.java

@@ -0,0 +1,75 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.wkd;
+
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.apache.commons.codec.binary.ZBase32;
+
+public class UserIdToWKDAddress {
+
+    // RegEx for Email Addresses
+    // https://www.baeldung.com/java-email-validation-regex#regular-expression-by-rfc-5322-for-email-validation
+    // Modified by adding capture groups '()' for local and domain part
+    private static final Pattern PATTERN_EMAIL = Pattern.compile("^([a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+)@([a-zA-Z0-9.-]+)$");
+    private static final Pattern PATTERN_USER_ID = Pattern.compile("^.*\\<([a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+@[a-zA-Z0-9.-]+)\\>.*");
+
+    /**
+     * Extract the email address from a user-id.
+     * The user-id is expected to correspond to a RFC2822 name-addr.
+     * The email address is expected to be framed by angle brackets.
+     *
+     * @see <a href="https://datatracker.ietf.org/doc/html/rfc2822#section-3.4">RFC2822 - Internet Message Format §3.4: Address Specification</a>
+     * @param userId user-id name-addr
+     * @return WKD URI
+     *
+     * @throws IllegalArgumentException in case the user-id does not match the expected format
+     */
+    public URI userIdToUri(String userId) {
+        String lowerCase = userId.toLowerCase();
+        Matcher matcher = PATTERN_USER_ID.matcher(lowerCase);
+        if (!matcher.matches()) {
+            throw new IllegalArgumentException("User-ID does not follow excepted pattern \"Firstname Lastname <email.address> [Optional Comment]\"");
+        }
+        String email = matcher.group(1);
+        return mailToUri(email);
+    }
+
+    /**
+     * Translate an email address (localpart@domainpart) to a WKD URI.
+     *
+     * @param email email address
+     * @return WKD URI
+     * @throws IllegalArgumentException in case of a malformed email address
+     */
+    public URI mailToUri(String email) {
+        String lowerCase = email.toLowerCase();
+        Matcher matcher = PATTERN_EMAIL.matcher(lowerCase);
+        if (!matcher.matches()) {
+            throw new IllegalArgumentException("Invalid email address.");
+        }
+
+        String localPart = matcher.group(1);
+        String domainPart = matcher.group(2);
+
+        MessageDigest sha1;
+        try {
+            sha1 = MessageDigest.getInstance("SHA1");
+        } catch (NoSuchAlgorithmException e) {
+            throw new AssertionError("SHA-1 is available on all JVMs.", e);
+        }
+        sha1.update(localPart.getBytes(StandardCharsets.UTF_8));
+        byte[] digest = sha1.digest();
+
+        String base32KeyHandle = new ZBase32().encodeAsString(digest);
+
+        return URI.create("https://" + domainPart + "/.well-known/openpgpkey/hu/" + base32KeyHandle);
+    }
+}

wkd-java/src/test/java/pgp/wkd/WKDResolverTest.java

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pgp.wkd;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.net.URI;
+
+import org.junit.jupiter.api.Test;
+
+public class WKDResolverTest {
+
+    @Test
+    public void testUserIdToUri() {
+        String userId = "Joe Doe <joe.doe@example.org> [Work Address]";
+        URI expectedURI = URI.create("https://example.org/.well-known/openpgpkey/hu/iy9q119eutrkn8s1mk4r39qejnbu3n5q");
+
+        URI actual = new UserIdToWKDAddress().userIdToUri(userId);
+        assertEquals(expectedURI, actual);
+    }
+
+    @Test
+    public void testMailToUri() {
+        String mailAddress = "Joe.Doe@Example.ORG";
+        URI expectedURI = URI.create("https://example.org/.well-known/openpgpkey/hu/iy9q119eutrkn8s1mk4r39qejnbu3n5q");
+
+        URI actual = new UserIdToWKDAddress().mailToUri(mailAddress);
+        assertEquals(expectedURI, actual);
+    }
+
+    @Test
+    public void testInvalidEmailToUri() {
+        UserIdToWKDAddress uid2wkd = new UserIdToWKDAddress();
+        assertThrows(IllegalArgumentException.class, () -> uid2wkd.mailToUri("john.doe"));
+        assertThrows(IllegalArgumentException.class, () -> uid2wkd.mailToUri("@example.org"));
+        assertThrows(IllegalArgumentException.class, () -> uid2wkd.mailToUri("john doe@example.org"));
+        assertThrows(IllegalArgumentException.class, () -> uid2wkd.mailToUri("john.doe@example org"));
+    }
+}