HPI-22073 IAM-10197 IAM-10215 Update here-aaa-java-sdk to support jwt assertions

Author: spaltis

.github/workflows/test.yml

@@ -23,4 +23,14 @@ jobs:
       - name: Verify Maven installation
         run: mvn -v
       - name: Run AAA SDK tests
-        run: mvn -Dhere.token.endpoint.url=https://stg.account.api.here.com/oauth2/token -Dhere.access.key.id=${{ secrets.ACCESS_KEY_ID }} -Dhere.access.key.secret=${{ secrets.ACCESS_KEY_SECRET }} clean install
+        run: mvn -Dhere.token.endpoint.url=https://stg.account.api.here.com/oauth2/token -Dhere.access.key.id=${{ secrets.ACCESS_KEY_ID }} -Dhere.access.key.secret=${{ secrets.ACCESS_KEY_SECRET }} clean install
+      - name: Run JWT client assertion integration test
+        if: ${{ secrets.JWT_PRIVATE_KEY != '' }}
+        run: |
+          mvn test -pl here-oauth-client -Dtest=JwtClientAssertionIT \
+            -Dhere.token.endpoint.url=https://stg.account.api.here.com/oauth2/token \
+            -Dhere.jwt.client.id=${{ secrets.JWT_CLIENT_ID }} \
+            -Dhere.jwt.private.key="${{ secrets.JWT_PRIVATE_KEY }}" \
+            -Dhere.jwt.key.id=${{ secrets.JWT_KEY_ID }} \
+            -Dhere.jwt.token.scope=${{ secrets.JWT_TOKEN_SCOPE }}
+

.gitignore

@@ -10,3 +10,10 @@ target
 /bin/
 pom.xml.versionsBackup
 examples/here-oauth-client-example/dependency-reduced-pom.xml
+
+# Credentials / secrets — never commit
+*.credentials.properties
+credentials.properties
+credentials.ini
+*.pem
+*.key

README.md

@@ -192,6 +192,49 @@ You can also use one of the proxy options to getAccessToken
 
 If you want move advanced options, you can provide your own HttpProvider `HereAccessTokenProvider.builder().setHttpProvider(<httpProvider>).build();`
 
+OAuth 2.1 private_key_jwt Authentication
+----------------------------------------
+
+A fourth option uses OAuth 2.1 JWT client assertions (`private_key_jwt` per RFC 7523 §2.2) instead of OAuth 1.0 signatures.
+The client authenticates by signing a short-lived JWT with its RSA private key. The corresponding public key must be
+registered on the HERE Account server as a JWK.
+
+Credentials file (`~/.here/credentials.properties` or `~/.here/credentials.ini`):
+```properties
+here.token.endpoint.url=https://account.api.here.com/oauth2/token
+here.auth.method=private_key_jwt
+here.client.id=<your_client_id>
+here.private.key=/path/to/private-key.pem
+here.key.id=<optional_kid>
+```
+
+Usage (same API as OAuth 1.0 — auto-detected by the provider chain):
+```java
+try (HereAccessTokenProvider accessTokens = HereAccessTokenProvider.builder().build()) {
+    String accessToken = accessTokens.getAccessToken();
+}
+```
+
+Or construct the provider explicitly:
+```java
+JwtClientAssertionProvider provider = new JwtClientAssertionProvider(
+    new SettableSystemClock(),
+    "https://account.api.here.com/oauth2/token",
+    "<your_client_id>",
+    JwtClientAssertionProvider.loadPrivateKey("/path/to/private-key.pem"),
+    null,  // scope (optional)
+    "<kid>"  // key ID (optional)
+);
+try (HereAccessTokenProvider accessTokens = HereAccessTokenProvider.builder()
+        .setClientAuthorizationRequestProvider(provider)
+        .build()) {
+    String accessToken = accessTokens.getAccessToken();
+}
+```
+
+The private key must be a PKCS#8 PEM-encoded RSA key. The `here.private.key` value can be either
+a file path or the inline PEM content itself (useful for environment variables in CI).
+
 # License
 
 Copyright (C) 2016-2019 HERE Europe B.V.

here-oauth-client/src/main/java/com/here/account/auth/JwtClientAssertionBuilder.java

@@ -0,0 +1,209 @@
+/*
+ * Copyright (c) 2025 HERE Europe B.V.
+ *
+ * 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 com.here.account.auth;
+
+import com.here.account.util.Clock;
+import com.here.account.util.OAuthConstants;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.PrivateKey;
+import java.security.Signature;
+import java.security.SignatureException;
+import java.util.Base64;
+import java.util.Objects;
+import java.util.UUID;
+
+/**
+ * Builds and signs JWT client assertions for use with OAuth 2.1 private_key_jwt
+ * authentication per RFC 7523 Section 2.2.
+ *
+ * <p>
+ * The produced JWT has:
+ * <ul>
+ *   <li>Header: {@code {"alg":"RS256","typ":"JWT"}}</li>
+ *   <li>Claims: iss, sub (both = client_id), aud (token endpoint), exp, iat, jti</li>
+ *   <li>Signature: RS256 (RSASSA-PKCS1-v1_5 with SHA-256)</li>
+ * </ul>
+ *
+ * @see <a href="https://www.rfc-editor.org/rfc/rfc7523#section-2.2">RFC 7523 §2.2</a>
+ * @see <a href="https://www.rfc-editor.org/rfc/rfc7519">RFC 7519 (JWT)</a>
+ * @see <a href="https://datatracker.ietf.org/doc/html/draft-ietf-oauth-v2-1-13">OAuth 2.1</a>
+ */
+public class JwtClientAssertionBuilder {
+
+    private static final String SIGNATURE_ALGORITHM = "SHA256withRSA";
+
+    /**
+     * Default token lifetime: 5 minutes (300 seconds).
+     * Per RFC 7523 §3, the assertion SHOULD have a short lifetime.
+     */
+    private static final long DEFAULT_EXPIRY_SECONDS = 300L;
+
+    private final String clientId;
+    private final String tokenEndpointUrl;
+    private final PrivateKey privateKey;
+    private final Clock clock;
+    private long expirySeconds = DEFAULT_EXPIRY_SECONDS;
+    private String kid;
+
+    /**
+     * Construct a new JWT client assertion builder.
+     *
+     * @param clock            the clock for timestamps
+     * @param clientId         the client identifier (becomes iss and sub)
+     * @param tokenEndpointUrl the token endpoint URL (becomes aud)
+     * @param privateKey       the RSA private key for signing
+     */
+    public JwtClientAssertionBuilder(Clock clock, String clientId, String tokenEndpointUrl, PrivateKey privateKey) {
+        Objects.requireNonNull(clock, "clock is required");
+        Objects.requireNonNull(clientId, "clientId is required");
+        Objects.requireNonNull(tokenEndpointUrl, "tokenEndpointUrl is required");
+        Objects.requireNonNull(privateKey, "privateKey is required");
+
+        this.clock = clock;
+        this.clientId = clientId;
+        this.tokenEndpointUrl = tokenEndpointUrl;
+        this.privateKey = privateKey;
+    }
+
+    /**
+     * Set a custom expiry duration for the assertion JWT.
+     *
+     * @param expirySeconds lifetime in seconds (must be positive, max recommended 300s)
+     * @return this builder
+     */
+    public JwtClientAssertionBuilder setExpirySeconds(long expirySeconds) {
+        if (expirySeconds <= 0) {
+            throw new IllegalArgumentException("expirySeconds must be positive");
+        }
+        this.expirySeconds = expirySeconds;
+        return this;
+    }
+
+    /**
+     * Set the Key ID (kid) to include in the JWT header.
+     * When the application has multiple registered JWKs, the kid helps the
+     * authorization server identify which public key to use for verification.
+     *
+     * @param kid the key identifier (matches the kid registered on the app's JWK)
+     * @return this builder
+     */
+    public JwtClientAssertionBuilder setKid(String kid) {
+        this.kid = kid;
+        return this;
+    }
+
+    /**
+     * Build and sign a new JWT client assertion.
+     *
+     * <p>Per RFC 7523 §3, the JWT MUST contain:
+     * <ul>
+     *   <li>iss - the client_id</li>
+     *   <li>sub - the client_id</li>
+     *   <li>aud - the token endpoint URL</li>
+     *   <li>exp - expiration time</li>
+     *   <li>iat - issued at time</li>
+     *   <li>jti - unique token identifier (prevents replay)</li>
+     * </ul>
+     *
+     * @return the compact serialized JWT (header.payload.signature)
+     * @throws ClientAssertionException if signing fails
+     */
+    public String buildAssertion() {
+        long nowSeconds = clock.currentTimeMillis() / 1000L;
+        long exp = nowSeconds + expirySeconds;
+        String jti = UUID.randomUUID().toString();
+
+        String header = buildHeaderJson();
+        String payload = buildPayloadJson(nowSeconds, exp, jti);
+
+        String headerEncoded = base64UrlEncode(header.getBytes(OAuthConstants.UTF_8_CHARSET));
+        String payloadEncoded = base64UrlEncode(payload.getBytes(OAuthConstants.UTF_8_CHARSET));
+
+        String signingInput = headerEncoded + "." + payloadEncoded;
+        String signature = sign(signingInput);
+
+        return signingInput + "." + signature;
+    }
+
+    private String buildHeaderJson() {
+        if (kid != null && !kid.isEmpty()) {
+            return "{\"alg\":\"RS256\",\"typ\":\"JWT\",\"kid\":\"" + escapeJson(kid) + "\"}";
+        }
+        return "{\"alg\":\"RS256\",\"typ\":\"JWT\"}";
+    }
+
+    private String buildPayloadJson(long iat, long exp, String jti) {
+        // Manual JSON construction to avoid dependency on serialization library for this simple case.
+        // All string values are safe (no special chars that need escaping in client_id, URL, UUID).
+        return "{" +
+                "\"iss\":\"" + escapeJson(clientId) + "\"," +
+                "\"sub\":\"" + escapeJson(clientId) + "\"," +
+                "\"aud\":\"" + escapeJson(tokenEndpointUrl) + "\"," +
+                "\"exp\":" + exp + "," +
+                "\"iat\":" + iat + "," +
+                "\"jti\":\"" + escapeJson(jti) + "\"" +
+                "}";
+    }
+
+    private String sign(String signingInput) {
+        try {
+            Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);
+            sig.initSign(privateKey);
+            sig.update(signingInput.getBytes(OAuthConstants.UTF_8_CHARSET));
+            byte[] signatureBytes = sig.sign();
+            return base64UrlEncode(signatureBytes);
+        } catch (NoSuchAlgorithmException | InvalidKeyException | SignatureException e) {
+            throw new ClientAssertionException("Failed to sign JWT client assertion: " + e.getMessage(), e);
+        }
+    }
+
+    private static String base64UrlEncode(byte[] data) {
+        return Base64.getUrlEncoder().withoutPadding().encodeToString(data);
+    }
+
+    /**
+     * Minimal JSON string escaping for known-safe values (client IDs, URLs, UUIDs).
+     */
+    private static String escapeJson(String value) {
+        if (value == null) {
+            return "";
+        }
+        StringBuilder sb = new StringBuilder(value.length());
+        for (int i = 0; i < value.length(); i++) {
+            char c = value.charAt(i);
+            switch (c) {
+                case '"':  sb.append("\\\""); break;
+                case '\\': sb.append("\\\\"); break;
+                case '\n': sb.append("\\n"); break;
+                case '\r': sb.append("\\r"); break;
+                case '\t': sb.append("\\t"); break;
+                default:   sb.append(c);
+            }
+        }
+        return sb.toString();
+    }
+
+    /**
+     * Exception thrown when JWT client assertion building/signing fails.
+     */
+    public static class ClientAssertionException extends RuntimeException {
+        public ClientAssertionException(String message, Throwable cause) {
+            super(message, cause);
+        }
+    }
+}