Adds handling for common JSON parsing exceptions and wraps them in a JwtException

Move the parser error handling logic out of DefaultJwtParser into the new JwtDeserializer and wraps them with developer freiendly exceptions
Add check for common JSON parsing exceptions like stack overflow when parsing deeply nested (or malformed) JSON

Author: bdemers

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## Release Notes
 
+### 0.11.3
+
+This patch release:
+
+* Adds handling for common JSON parsing exceptions and wraps them in a `JwtException`.
+
 ### 0.11.2
 
 This patch release:

impl/src/main/java/io/jsonwebtoken/impl/DefaultJwtParser.java

@@ -42,7 +42,6 @@
 import io.jsonwebtoken.impl.lang.LegacyServices;
 import io.jsonwebtoken.io.Decoder;
 import io.jsonwebtoken.io.Decoders;
-import io.jsonwebtoken.io.DeserializationException;
 import io.jsonwebtoken.io.Deserializer;
 import io.jsonwebtoken.lang.Assert;
 import io.jsonwebtoken.lang.DateFormats;
@@ -111,7 +110,7 @@ public DefaultJwtParser() { }
     @Override
     public JwtParser deserializeJsonWith(Deserializer<Map<String, ?>> deserializer) {
         Assert.notNull(deserializer, "deserializer cannot be null.");
-        this.deserializer = deserializer;
+        this.deserializer = new JwtDeserializer<>(deserializer);
         return this;
     }
 
@@ -253,7 +252,7 @@ public Jwt parse(String jwt) throws ExpiredJwtException, MalformedJwtException,
         if (this.deserializer == null) {
             // try to find one based on the services available
             // TODO: This util class will throw a UnavailableImplementationException here to retain behavior of previous version, remove in v1.0
-            this.deserializer = LegacyServices.loadFirst(Deserializer.class);
+            this.deserializeJsonWith(LegacyServices.loadFirst(Deserializer.class));
         }
 
         Assert.hasText(jwt, "JWT String argument cannot be null or empty.");
@@ -617,11 +616,7 @@ public Jws<Claims> onClaimsJws(Jws<Claims> jws) {
 
     @SuppressWarnings("unchecked")
     protected Map<String, ?> readValue(String val) {
-        try {
-            byte[] bytes = val.getBytes(Strings.UTF_8);
-            return deserializer.deserialize(bytes);
-        } catch (DeserializationException e) {
-            throw new MalformedJwtException("Unable to read JSON value: " + val, e);
-        }
+        byte[] bytes = val.getBytes(Strings.UTF_8);
+        return deserializer.deserialize(bytes);
     }
 }

impl/src/main/java/io/jsonwebtoken/impl/DefaultJwtParserBuilder.java

@@ -204,7 +204,7 @@ public JwtParser build() {
                                      allowedClockSkewMillis,
                                      expectedClaims,
                                      base64UrlDecoder,
-                                     deserializer,
+                                     new JwtDeserializer<>(deserializer),
                                      compressionCodecResolver));
     }
 }

impl/src/main/java/io/jsonwebtoken/impl/JwtDeserializer.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2021 jsonwebtoken.io
+ *
+ * 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.jsonwebtoken.impl;
+
+import io.jsonwebtoken.MalformedJwtException;
+import io.jsonwebtoken.io.DeserializationException;
+import io.jsonwebtoken.io.Deserializer;
+import io.jsonwebtoken.io.IOException;
+import io.jsonwebtoken.lang.Assert;
+
+import java.nio.charset.StandardCharsets;
+
+/**
+ * A {@link Deserializer} implementation that wraps another Deserializer implementation to adds common JWT related
+ * error handling.
+ * @param <T> type of object to deserialize.
+ * @since 0.11.3
+ */
+class JwtDeserializer<T> implements Deserializer<T> {
+
+    static final String MALFORMED_ERROR = "Malformed JWT JSON: ";
+    static final String MALFORMED_COMPLEX_ERROR = "Malformed or excessively complex JWT JSON. This could reflect a potential malicious JWT, please investigate the JWT source further. JSON: ";
+
+    private final Deserializer<T> deserializer;
+
+    JwtDeserializer(Deserializer<T> deserializer) {
+        Assert.notNull(deserializer, "deserializer cannot be null.");
+        this.deserializer = deserializer;
+    }
+
+    @Override
+    public T deserialize(byte[] bytes) throws DeserializationException {
+        try {
+            return deserializer.deserialize(bytes);
+        } catch (DeserializationException e) {
+            throw new MalformedJwtException(MALFORMED_ERROR + new String(bytes, StandardCharsets.UTF_8), e);
+        } catch (StackOverflowError e) {
+            throw new IOException(MALFORMED_COMPLEX_ERROR + new String(bytes, StandardCharsets.UTF_8), e);
+        }
+    }
+}

impl/src/test/groovy/io/jsonwebtoken/DeprecatedJwtParserTest.groovy

@@ -83,7 +83,7 @@ class DeprecatedJwtParserTest {
             Jwts.parser().parse(bad)
             fail()
         } catch (MalformedJwtException expected) {
-            assertEquals expected.getMessage(), 'Unable to read JSON value: ' + junkPayload
+            assertEquals expected.getMessage(), 'Malformed JWT JSON: ' + junkPayload
         }
     }
 

impl/src/test/groovy/io/jsonwebtoken/JwtParserTest.groovy

@@ -86,7 +86,7 @@ class JwtParserTest {
             Jwts.parserBuilder().build().parse(bad)
             fail()
         } catch (MalformedJwtException expected) {
-            assertEquals expected.getMessage(), 'Unable to read JSON value: ' + junkPayload
+            assertEquals expected.getMessage(), 'Malformed JWT JSON: ' + junkPayload
         }
     }
 

impl/src/test/groovy/io/jsonwebtoken/impl/DefaultJwtParserTest.groovy

@@ -29,6 +29,7 @@ import javax.crypto.SecretKey
 
 import static org.junit.Assert.assertEquals
 import static org.junit.Assert.assertSame
+import static org.junit.Assert.assertTrue
 
 // NOTE to the casual reader: even though this test class appears mostly empty, the DefaultJwtParser
 // implementation is tested to 100% coverage.  The vast majority of its tests are in the JwtsTest class.  This class
@@ -69,7 +70,8 @@ class DefaultJwtParserTest {
             }
         }
         def p = new DefaultJwtParser().deserializeJsonWith(deserializer)
-        assertSame deserializer, p.deserializer
+        assertTrue("Expected wrapping deserializer to be instance of JwtDeserializer", p.deserializer instanceof JwtDeserializer )
+        assertSame deserializer, p.deserializer.deserializer
 
         def key = Keys.secretKeyFor(SignatureAlgorithm.HS256)
 

impl/src/test/groovy/io/jsonwebtoken/impl/JwtDeserializerTest.groovy

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2021 jsonwebtoken.io
+ *
+ * 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.jsonwebtoken.impl
+
+import io.jsonwebtoken.MalformedJwtException
+import io.jsonwebtoken.io.DeserializationException
+import io.jsonwebtoken.io.Deserializer
+import io.jsonwebtoken.io.IOException
+import org.junit.Assert
+import org.junit.Test
+
+import java.nio.charset.StandardCharsets
+
+import static org.easymock.EasyMock.expect
+import static org.easymock.EasyMock.mock
+import static org.easymock.EasyMock.replay
+import static org.junit.Assert.assertEquals
+
+class JwtDeserializerTest {
+
+    /**
+     * It's common for JSON parser's to throw a StackOverflowError when body is deeply nested. Since it's common
+     * across multiple parsers, JJWT handles the exception when parsing.
+     */
+    @Test
+    void testParserStackOverflowError() {
+
+        byte[] jsonBytes = '{"test": "testParserStackOverflowError"}'.getBytes(StandardCharsets.UTF_8)
+
+        // create a Deserializer that will throw a StackOverflowError
+        Deserializer<Map<String,?>> deserializer = mock(Deserializer)
+        expect(deserializer.deserialize(jsonBytes)).andThrow(new StackOverflowError("Test exception: testParserStackOverflowError" ))
+        replay(deserializer)
+
+        try {
+            new JwtDeserializer<>(deserializer).deserialize(jsonBytes)
+            Assert.fail("Expected IOException")
+        } catch (IOException e) {
+            assertEquals JwtDeserializer.MALFORMED_COMPLEX_ERROR + new String(jsonBytes), e.message
+        }
+    }
+
+    /**
+     * Check that a DeserializationException, is wrapped and rethrown as a MalformedJwtException with a developer friendly message.
+     */
+    @Test
+    void testDeserializationExceptionMessage() {
+
+        byte[] jsonBytes = '{"test": "testDeserializationExceptionMessage"}'.getBytes(StandardCharsets.UTF_8)
+
+        // create a Deserializer that will throw a DeserializationException
+        Deserializer<Map<String,?>> deserializer = mock(Deserializer)
+        expect(deserializer.deserialize(jsonBytes)).andThrow(new DeserializationException("Test exception: testDeserializationExceptionMessage" ))
+        replay(deserializer)
+
+        try {
+            new JwtDeserializer<>(deserializer).deserialize(jsonBytes)
+            Assert.fail("Expected MalformedJwtException")
+        } catch (MalformedJwtException e) {
+            assertEquals JwtDeserializer.MALFORMED_ERROR + new String(jsonBytes), e.message
+        }
+    }
+}