Avoid invalid JSON in JSONErrorReportValve output

java/org/apache/catalina/valves/JsonErrorReportValve.java

@@ -22,6 +22,7 @@
 import org.apache.catalina.connector.Request;
 import org.apache.catalina.connector.Response;
 import org.apache.tomcat.util.ExceptionUtils;
+import org.apache.tomcat.util.json.JSONFilter;
 import org.apache.tomcat.util.res.StringManager;
 
 /**
@@ -62,9 +63,9 @@ protected void report(Request request, Response response, Throwable throwable) {
             }
         }
         String jsonReport = "{\n" +
-                            "  \"type\": \"" + type + "\",\n" +
-                            "  \"message\": \"" + message + "\",\n" +
-                            "  \"description\": \"" + description + "\"\n" +
+                            "  \"type\": \"" + JSONFilter.escape(type) + "\",\n" +
+                            "  \"message\": \"" + JSONFilter.escape(message) + "\",\n" +
+                            "  \"description\": \"" + JSONFilter.escape(description) + "\"\n" +
                             "}";
         try {
             try {

java/org/apache/tomcat/util/json/JSONFilter.java

@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.tomcat.util.json;
+
+/**
+ * Provides escaping of values so they can be included in a JSON document.
+ * Escaping is based on the definition of JSON found in
+ * <a href="https://www.rfc-editor.org/rfc/rfc8259.html">RFC 8259</a>.
+ */
+public class JSONFilter {
+
+    private JSONFilter() {
+        // Utility class. Hide the default constructor.
+    }
+
+    public static String escape(String input) {
+        /*
+         * While any character MAY be escaped, only U+0000 to U+001F (control
+         * characters), U+0022 (quotation mark) and U+005C (reverse solidus)
+         * MUST be escaped.
+         */
+        char[] chars = input.toCharArray();
+        StringBuffer escaped = null;
+        int lastUnescapedStart = 0;
+        for (int i = 0; i < chars.length; i++) {
+            if (chars[i] < 0x20 || chars[i] == 0x22 || chars[i] == 0x5c) {
+                if (escaped == null) {
+                    escaped = new StringBuffer(chars.length + 20);
+                }
+                if (lastUnescapedStart < i) {
+                    escaped.append(input.subSequence(lastUnescapedStart, i));
+                }
+                lastUnescapedStart = i + 1;
+                escaped.append("\\u");
+                escaped.append(String.format("%04X", Integer.valueOf(chars[i])));
+            }
+        }
+        if (escaped == null) {
+            return input;
+        } else {
+            if (lastUnescapedStart < chars.length) {
+                escaped.append(input.subSequence(lastUnescapedStart, chars.length));
+            }
+            return escaped.toString();
+        }
+    }
+}

test/org/apache/tomcat/util/json/TestJSONFilter.java

@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.tomcat.util.json;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+
+
+@RunWith(Parameterized.class)
+public class TestJSONFilter {
+
+    @Parameterized.Parameters(name = "{index}: input[{0}], output[{1}]")
+    public static Collection<Object[]> parameters() {
+        Collection<Object[]> parameterSets = new ArrayList<>();
+
+        // Empty
+        parameterSets.add(new String[] { "", "" });
+
+        // Must escape
+        parameterSets.add(new String[] { "\"", "\\u0022" });
+        parameterSets.add(new String[] { "\\", "\\u005C" });
+        // Sample of controls
+        parameterSets.add(new String[] { "\t", "\\u0009" });
+        parameterSets.add(new String[] { "\n", "\\u000A" });
+        parameterSets.add(new String[] { "\r", "\\u000D" });
+
+        // No escape
+        parameterSets.add(new String[] { "aaa", "aaa" });
+
+        // Start
+        parameterSets.add(new String[] { "\naaa", "\\u000Aaaa" });
+        parameterSets.add(new String[] { "\n\naaa", "\\u000A\\u000Aaaa" });
+
+        // Middle
+        parameterSets.add(new String[] { "aaa\naaa", "aaa\\u000Aaaa" });
+        parameterSets.add(new String[] { "aaa\n\naaa", "aaa\\u000A\\u000Aaaa" });
+
+        // End
+        parameterSets.add(new String[] { "aaa\n", "aaa\\u000A" });
+        parameterSets.add(new String[] { "aaa\n\n", "aaa\\u000A\\u000A" });
+
+        // Start, middle and end
+        parameterSets.add(new String[] { "\naaa\naaa\n", "\\u000Aaaa\\u000Aaaa\\u000A" });
+        parameterSets.add(new String[] { "\n\naaa\n\naaa\n\n", "\\u000A\\u000Aaaa\\u000A\\u000Aaaa\\u000A\\u000A" });
+
+        // Multiple
+        parameterSets.add(new String[] { "\n\n", "\\u000A\\u000A" });
+
+        return parameterSets;
+    }
+
+    @Parameter(0)
+    public String input;
+
+    @Parameter(1)
+    public String output;
+
+    @Test
+    public void testStringEscaping() {
+        Assert.assertEquals(output, JSONFilter.escape(input));;
+    }
+}

webapps/docs/changelog.xml

@@ -166,6 +166,11 @@
         provided error code during error page processing rather than assuming an
         error code of 500. (markt)
       </fix>
+      <fix>
+        Escape values used to construct output for the
+        <code>JsonErrorReportValve</code> to ensure that it always outputs valid
+        JSON. (markt)
+      </fix>
     </changelog>
   </subsection>
   <subsection name="Coyote">