added PKCE support to client

openid-connect-client/src/main/java/org/mitre/openid/connect/client/OIDCAuthenticationFilter.java

@@ -23,6 +23,9 @@ import static org.mitre.oauth2.model.ClientDetailsEntity.AuthMethod.SECRET_JWT;
 import java.io.IOException;
 import java.math.BigInteger;
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
 import java.text.ParseException;
 import java.util.Date;
@@ -40,6 +43,7 @@ import org.apache.http.impl.client.HttpClientBuilder;
 import org.mitre.jwt.signer.service.JWTSigningAndValidationService;
 import org.mitre.jwt.signer.service.impl.JWKSetCacheService;
 import org.mitre.jwt.signer.service.impl.SymmetricKeyJWTValidatorCacheService;
+import org.mitre.oauth2.model.PKCEAlgorithm;
 import org.mitre.oauth2.model.RegisteredClient;
 import org.mitre.openid.connect.client.model.IssuerServiceResponse;
 import org.mitre.openid.connect.client.service.AuthRequestOptionsService;
@@ -75,6 +79,7 @@ import com.nimbusds.jose.Algorithm;
 import com.nimbusds.jose.JWSAlgorithm;
 import com.nimbusds.jose.JWSHeader;
 import com.nimbusds.jose.util.Base64;
+import com.nimbusds.jose.util.Base64URL;
 import com.nimbusds.jwt.JWT;
 import com.nimbusds.jwt.JWTClaimsSet;
 import com.nimbusds.jwt.JWTParser;
@@ -90,10 +95,11 @@ import com.nimbusds.jwt.SignedJWT;
 public class OIDCAuthenticationFilter extends AbstractAuthenticationProcessingFilter {
 
 	protected final static String REDIRECT_URI_SESION_VARIABLE = "redirect_uri";
+	protected final static String CODE_VERIFIER_SESSION_VARIABLE = "code_verifier";
 	protected final static String STATE_SESSION_VARIABLE = "state";
 	protected final static String NONCE_SESSION_VARIABLE = "nonce";
 	protected final static String ISSUER_SESSION_VARIABLE = "issuer";
-	protected static final String TARGET_SESSION_VARIABLE = "target";
+	protected final static String TARGET_SESSION_VARIABLE = "target";
 	protected final static int HTTP_SOCKET_TIMEOUT = 30000;
 
 	public final static String FILTER_PROCESSES_URL = "/openid_connect_login";
@@ -262,6 +268,26 @@ public class OIDCAuthenticationFilter extends AbstractAuthenticationProcessingFi
 			String state = createState(session);
 
 			Map<String, String> options = authOptions.getOptions(serverConfig, clientConfig, request);
+			
+			// if we're using PKCE, handle the challenge here
+			if (clientConfig.getCodeChallengeMethod() != null) {
+				String codeVerifier = createCodeVerifier(session);
+				options.put("code_challenge_method", clientConfig.getCodeChallengeMethod().getName());
+				if (clientConfig.getCodeChallengeMethod().equals(PKCEAlgorithm.plain)) {
+					options.put("code_challenge", codeVerifier);
+				} else if (clientConfig.getCodeChallengeMethod().equals(PKCEAlgorithm.S256)) {
+					try {
+						MessageDigest digest = MessageDigest.getInstance("SHA-256");
+						String hash = Base64URL.encode(digest.digest(codeVerifier.getBytes(StandardCharsets.US_ASCII))).toString();
+						options.put("code_challenge", hash);
+					} catch (NoSuchAlgorithmException e) {
+						// TODO Auto-generated catch block
+						e.printStackTrace();
+					}
+
+					
+				}
+			}
 
 			String authRequest = authRequestBuilder.buildAuthRequestUrl(serverConfig, clientConfig, redirectUri, nonce, state, options, issResp.getLoginHint());
 
@@ -302,6 +328,11 @@ public class OIDCAuthenticationFilter extends AbstractAuthenticationProcessingFi
 		form.add("grant_type", "authorization_code");
 		form.add("code", authorizationCode);
 		form.setAll(authOptions.getTokenOptions(serverConfig, clientConfig, request));
+		
+		String codeVerifier = getStoredCodeVerifier(session);
+		if (codeVerifier != null) {
+			form.add("code_verifier", codeVerifier);
+		}
 
 		String redirectUri = getStoredSessionString(session, REDIRECT_URI_SESION_VARIABLE);
 		if (redirectUri != null) {
@@ -675,6 +706,26 @@ public class OIDCAuthenticationFilter extends AbstractAuthenticationProcessingFi
 	protected static String getStoredState(HttpSession session) {
 		return getStoredSessionString(session, STATE_SESSION_VARIABLE);
 	}
+	
+	/**
+	 * Create a random code challenge and store it in the session
+	 * @param session
+	 * @return
+	 */
+	protected static String createCodeVerifier(HttpSession session) {
+		String challenge = new BigInteger(50, new SecureRandom()).toString(16);
+		session.setAttribute(CODE_VERIFIER_SESSION_VARIABLE, challenge);
+		return challenge;
+	}
+	
+	/**
+	 * Retrieve the stored challenge from our session
+	 * @param session
+	 * @return
+	 */
+	protected static String getStoredCodeVerifier(HttpSession session) {
+		return getStoredSessionString(session, CODE_VERIFIER_SESSION_VARIABLE);
+	}
 
 
 	@Override