Initial implementation of a DPoP proofing mechanism

implementation/src/main/java/io/smallrye/jwt/auth/dpop/AbstractDpopTokenValidator.java

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+/*
+ * Copyright 2020 Red Hat, Inc, and individual contributors.
+ *
+ * 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 io.smallrye.jwt.auth.dpop;
+
+import static org.jose4j.jwa.AlgorithmConstraints.ConstraintType.PERMIT;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Map;
+
+import org.eclipse.microprofile.jwt.Claims;
+import org.eclipse.microprofile.jwt.JsonWebToken;
+import org.jose4j.jwa.AlgorithmConstraints;
+import org.jose4j.jwt.JwtClaims;
+import org.jose4j.jwt.consumer.InvalidJwtException;
+import org.jose4j.jwt.consumer.JwtConsumer;
+import org.jose4j.jwt.consumer.JwtConsumerBuilder;
+import org.jose4j.jwt.consumer.Validator;
+import org.jose4j.jwx.JsonWebStructure;
+import org.jose4j.keys.resolvers.EmbeddedJwkVerificationKeyResolver;
+import org.jose4j.lang.HashUtil;
+import org.jose4j.lang.JoseException;
+
+import io.smallrye.jwt.auth.principal.JWTAuthContextInfo;
+import io.smallrye.jwt.auth.principal.ParseException;
+
+/**
+ * Common functionality for classes implementing DPoP token proofing using
+ * HTTP request headers and a valid DPoP-bound {@link JsonWebToken}.
+ *
+ * @author Aaron Coburn {@literal <[email protected]>}
+ */
+public abstract class AbstractDpopTokenValidator {
+
+    protected static final String DPOP_HEADER = "DPoP";
+    protected static final String DPOP_HTTP_URI_CLAIM = "htu";
+    protected static final String DPOP_HTTP_METHOD_CLAIM = "htm";
+    protected static final String DPOP_JWT_TYPE = "dpop+jwt";
+    protected static final String JSON_WEB_KEY_THUMBPRINT = "jkt";
+
+    private final JWTAuthContextInfo authContextInfo;
+
+    protected AbstractDpopTokenValidator(JWTAuthContextInfo authContextInfo) {
+        this.authContextInfo = authContextInfo;
+    }
+
+    public void verify(JsonWebToken accessToken) throws ParseException {
+        final String dpop = getDpopHeaderValue();
+        final String thumbprint = getDpopKeyThumbprint(accessToken);
+        // DPoP validation is only relevant for access tokens with a bound confirmation key.
+        if (thumbprint != null) {
+            if (dpop != null) {
+                final JwtConsumer parser = new JwtConsumerBuilder()
+                        .setRequireJwtId()
+                        .setExpectedType(true, DPOP_JWT_TYPE)
+                        .setJwsAlgorithmConstraints(new AlgorithmConstraints(PERMIT,
+                                authContextInfo.getSignatureAlgorithm().getAlgorithm()))
+                        .setVerificationKeyResolver(new EmbeddedJwkVerificationKeyResolver())
+                        .setRequireIssuedAt().setAllowedClockSkewInSeconds(authContextInfo.getExpGracePeriodSecs())
+                        .setExpectedIssuer(false, null)
+                        .registerValidator(htuValidator(getRequestUri()))
+                        .registerValidator(htmValidator(getRequestMethod()))
+                        .registerValidator(thumbprintValidator(thumbprint))
+                        .build();
+                try {
+                    parser.process(dpop);
+                } catch (InvalidJwtException e) {
+                    DpopLogging.log.invalidDpopToken();
+                    throw DpopMessages.msg.failedToVerifyDpopToken(e);
+                }
+            } else {
+                DpopLogging.log.missingDpopToken();
+                throw DpopMessages.msg.missingDpopProof();
+            }
+        } else {
+            DpopLogging.log.missingDpopKeyBinding();
+            throw DpopMessages.msg.missingDpopKeyBinding();
+        }
+    }
+
+    /**
+     * Retrieve the DPoP-bound key thumbprint from the access token's confirmation claim.
+     *
+     * @param accessToken the access token
+     * @return the thumbprint of the DPoP-bound key, if one exists
+     */
+    protected String getDpopKeyThumbprint(JsonWebToken accessToken) {
+        final Object cnf = accessToken.getClaim(Claims.cnf.name());
+        if (cnf instanceof Map) {
+            final Object jkt = ((Map) cnf).get(JSON_WEB_KEY_THUMBPRINT);
+            if (jkt instanceof String) {
+                return (String) jkt;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Retrieve an HTTP DPoP header value.
+     *
+     * @return value of the header
+     */
+    protected abstract String getDpopHeaderValue();
+
+    /**
+     * Retrieve the HTTP request URI.
+     *
+     * @return the HTTP request URI
+     */
+    protected abstract String getRequestUri();
+
+    /**
+     * Retrieve the HTTP method.
+     *
+     * @return the HTTP method
+     */
+    protected abstract String getRequestMethod();
+
+    /**
+     * Validate the htu (HTTP URI) claim in the DPoP token.
+     *
+     * @param uri the HTTP request URI
+     */
+    static Validator htuValidator(String uri) {
+        return ctx -> {
+            final JwtClaims claims = ctx.getJwtClaims();
+            if (!claims.hasClaim(DPOP_HTTP_URI_CLAIM)) {
+                return "Missing required htu claim in DPoP token";
+            }
+            if (!compareUrls(uri, claims.getClaimValueAsString(DPOP_HTTP_URI_CLAIM))) {
+                return "Incorrect htu claim";
+            }
+            return null;
+        };
+    }
+
+    /**
+     * Validate the htm (HTTP Method) claim in the DPoP token.
+     *
+     * @param method the HTTP method
+     */
+    static Validator htmValidator(String method) {
+        return ctx -> {
+            final JwtClaims claims = ctx.getJwtClaims();
+            if (!claims.hasClaim(DPOP_HTTP_METHOD_CLAIM)) {
+                return "Missing required htm claim in DPoP token";
+            }
+
+            if (!method.equalsIgnoreCase(claims.getClaimValueAsString(DPOP_HTTP_METHOD_CLAIM))) {
+                return "Incorrect htm claim";
+            }
+            return null;
+        };
+    }
+
+    /**
+     * Validate that the embedded public key matches the provided thumbprint.
+     * 
+     * @param thumbprint the thumbprint of the expected public key
+     */
+    static Validator thumbprintValidator(String thumbprint) {
+        return ctx -> {
+            try {
+                for (JsonWebStructure jose : ctx.getJoseObjects()) {
+                    if (thumbprint.equals(jose.getJwkHeader().calculateBase64urlEncodedThumbprint(HashUtil.SHA_256))) {
+                        return null;
+                    }
+                }
+            } catch (JoseException ex) {
+                return "Could not calculate SHA-256 thumbprint of embedded DPoP key: " + ex.getMessage();
+            }
+            return "Mismatched public key thumbprint: " + thumbprint;
+        };
+    }
+
+    /**
+     * Compare two URLs, ignoring case and any query parameters.
+     *
+     * @param url1 the first URL
+     * @param url2 the second URL
+     * @return true if the two URLs are equivalent; otherwise, return false
+     */
+    static boolean compareUrls(String url1, String url2) {
+        if (url1 != null && url2 != null) {
+            if (url1.equalsIgnoreCase(url2)) {
+                return true;
+            }
+            // If a simple comparison was inconclusive, parse both into URI objects
+            try {
+                final URI uri1 = new URI(url1);
+                final URI uri2 = new URI(url2);
+                return uri1.getScheme().equalsIgnoreCase(uri2.getScheme())
+                        && uri1.getAuthority().equalsIgnoreCase(uri2.getAuthority())
+                        && uri1.getPath().equalsIgnoreCase(uri2.getPath());
+            } catch (URISyntaxException ex) {
+                DpopLogging.log.invalidRequestUrl(ex.getMessage());
+            }
+        }
+        return false;
+    }
+}

implementation/src/main/java/io/smallrye/jwt/auth/dpop/DpopLogging.java

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+package io.smallrye.jwt.auth.dpop;
+
+import org.jboss.logging.BasicLogger;
+import org.jboss.logging.Logger;
+import org.jboss.logging.annotations.LogMessage;
+import org.jboss.logging.annotations.Message;
+import org.jboss.logging.annotations.MessageLogger;
+
+@MessageLogger(projectCode = "SRJWT", length = 5)
+interface DpopLogging extends BasicLogger {
+    DpopLogging log = Logger.getMessageLogger(DpopLogging.class, DpopLogging.class.getPackage().getName());
+
+    @LogMessage(level = Logger.Level.DEBUG)
+    @Message(id = 15000, value = "Invalid DPoP token")
+    void invalidDpopToken();
+
+    @LogMessage(level = Logger.Level.DEBUG)
+    @Message(id = 15001, value = "Missing DPoP token")
+    void missingDpopToken();
+
+    @LogMessage(level = Logger.Level.DEBUG)
+    @Message(id = 15002, value = "Missing DPoP key binding in access token")
+    void missingDpopKeyBinding();
+
+    @LogMessage(level = Logger.Level.DEBUG)
+    @Message(id = 15003, value = "Invalid request URL: %s")
+    void invalidRequestUrl(String invalidUrlMsg);
+}

implementation/src/main/java/io/smallrye/jwt/auth/dpop/DpopMessages.java

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+package io.smallrye.jwt.auth.dpop;
+
+import org.jboss.logging.Messages;
+import org.jboss.logging.annotations.Cause;
+import org.jboss.logging.annotations.Message;
+import org.jboss.logging.annotations.MessageBundle;
+
+import io.smallrye.jwt.auth.principal.ParseException;
+
+@MessageBundle(projectCode = "SRJWT", length = 5)
+interface DpopMessages {
+    DpopMessages msg = Messages.getBundle(DpopMessages.class);
+
+    @Message(id = 14000, value = "Failed to verify DPoP token")
+    ParseException failedToVerifyDpopToken(@Cause Throwable e);
+
+    @Message(id = 14001, value = "Missing DPoP proofing value")
+    ParseException missingDpopProof();
+
+    @Message(id = 14002, value = "Missing DPoP key binding")
+    ParseException missingDpopKeyBinding();
+}