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WW-5845 Validate JSONP callback names #2121

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428db20
WW-5845 Validate the JSONP callback parameter name before wrapping th…
g0w6y Nov 7, 2026
89ea169
WW-5845 Address review: normalize the logged callback name, cover the…
g0w6y Nov 8, 2026
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7 changes: 6 additions & 1 deletion plugins/json/src/main/java/org/apache/struts2/json/JSONInterceptor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -541,8 +541,13 @@ private boolean checkSMDMethodSignature(Method method, String name, int paramete
protected String addCallbackIfApplicable(HttpServletRequest request, String json) {
if ((callbackParameter != null) && (callbackParameter.length() > 0)) {
String callbackName = request.getParameter(callbackParameter);
if ((callbackName != null) && (callbackName.length() > 0))
if ((callbackName != null) && (callbackName.length() > 0)) {
if (!JSONUtil.isValidJsonpCallbackName(callbackName)) {
LOG.warn("JSONP callback parameter [{}] is not a valid identifier; rejected", normalizeSpace(callbackName));
return json;
}
json = callbackName + "(" + json + ")";
}
}
return json;
}
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4 changes: 4 additions & 0 deletions plugins/json/src/main/java/org/apache/struts2/json/JSONResult.java
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Expand Up @@ -282,6 +282,10 @@ protected String addCallbackIfApplicable(HttpServletRequest request, String json
if ((callbackParameter != null) && (callbackParameter.length() > 0)) {
String callbackName = request.getParameter(callbackParameter);
if (StringUtils.isNotEmpty(callbackName)) {
if (!JSONUtil.isValidJsonpCallbackName(callbackName)) {
LOG.warn("JSONP callback parameter [{}] is not a valid identifier; rejected", StringUtils.normalizeSpace(callbackName));
return json;
}
json = callbackName + "(" + json + ")";
}
}
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16 changes: 16 additions & 0 deletions plugins/json/src/main/java/org/apache/struts2/json/JSONUtil.java
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Expand Up @@ -62,6 +62,9 @@ public class JSONUtil {
/** Chunk size used to read input incrementally while applying the length limit. */
private static final int READ_CHUNK_SIZE = 8192;

private static final Pattern JSONP_CALLBACK_PATTERN =
Pattern.compile("[A-Za-z_$][A-Za-z0-9_$]*(\\.[A-Za-z_$][A-Za-z0-9_$]*)*");

private JSONReader reader;
private JSONWriter writer;

Expand Down Expand Up @@ -565,6 +568,19 @@ public static boolean isGzipInRequest(HttpServletRequest request) {
return StringUtils.contains(request.getHeader("Accept-Encoding"), "gzip");
}

/**

@lukaszlenart lukaszlenart Nov 7, 2026

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Please reduce this to the contract: the accepted shape (dotted ASCII identifier, [A-Za-z_$][A-Za-z0-9_$]*, segments joined by .), the length cap, and @since. The two {@link}s to the call sites and the paragraph about what an unchecked value could do belong in the ticket, not in the Javadoc.

* Checks a JSONP callback name: a dotted ASCII identifier ({@code [A-Za-z_$][A-Za-z0-9_$]*},
* segments joined by {@code .}) of at most 128 characters.
*
* @param callbackName the requested callback name
* @return true if {@code callbackName} has that shape
* @since 7.5.0
*/
public static boolean isValidJsonpCallbackName(String callbackName) {
return callbackName != null && callbackName.length() <= 128
&& JSONP_CALLBACK_PATTERN.matcher(callbackName).matches();
}

public static final String REGEXP_PATTERN = "regexp";
public static final String WILDCARD_PATTERN = "wildcard";
/* package */ static final String SPLIT_PATTERN = "split";
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29 changes: 29 additions & 0 deletions plugins/json/src/test/java/org/apache/struts2/json/JSONInterceptorTest.java
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Expand Up @@ -240,6 +240,35 @@ public void testSMDPrimitivesNoResult() throws Exception {
assertEquals("application/json;charset=UTF-8", response.getContentType());
}

public void testSMDInvalidJSONPCallbackLeavesJsonUnwrapped() throws Exception {
String json = executeSMDWithCallback("cb);STRUTS_PROBE_MARKER;(");

assertEquals(TestUtils.normalize(JSONResultTest.class.getResource("smd-11.txt")), TestUtils.normalize(json, true));
assertFalse(json.contains("STRUTS_PROBE_MARKER"));
}

public void testSMDValidJSONPCallbackWrapsJson() throws Exception {
String json = executeSMDWithCallback("exec");

assertTrue(json.startsWith("exec(") && json.endsWith(")"));
assertEquals(TestUtils.normalize(JSONResultTest.class.getResource("smd-11.txt")),
TestUtils.normalize(json.substring("exec(".length(), json.length() - 1), true));
}

private String executeSMDWithCallback(String callback) throws Exception {
setRequestContent("smd-6.txt");
this.request.addHeader("Content-Type", "application/json-rpc");
this.request.addParameter("callback", callback);

JSONInterceptor interceptor = createInterceptor();
interceptor.setEnableSMD(true);
interceptor.setCallbackParameter("callback");
this.invocation.setAction(new SMDActionTest1());

interceptor.intercept(this.invocation);
return response.getContentAsString();
}

public void testSMDReturnObject() throws Exception {
// request
setRequestContent("smd-10.txt");
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19 changes: 19 additions & 0 deletions plugins/json/src/test/java/org/apache/struts2/json/JSONResultTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -539,6 +539,25 @@ public void testJSONP() throws Exception {
assertEquals("application/json;charset=UTF-8", response.getContentType());
}

// control case: testJSONP()
public void testJSONPCallbackMustBeValidIdentifier() throws Exception {
JSONResult result = new JSONResult();
result.setCallbackParameter("callback");
JSONUtil jsonUtil = new JSONUtil();
jsonUtil.setWriter(new StrutsJSONWriter());
result.setJsonUtil(jsonUtil);

String notAnIdentifier = "cb);STRUTS_PROBE_MARKER;(";
request.addParameter("callback", notAnIdentifier);

executeTest2Action(result);
String json = response.getContentAsString();

assertFalse("Non-identifier callback value must not be concatenated into the response",
json.contains(notAnIdentifier));
assertFalse(json.contains("STRUTS_PROBE_MARKER"));
}

public void testNoCache() throws Exception {
JSONResult result = new JSONResult();
result.setNoCache(true);
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13 changes: 13 additions & 0 deletions plugins/json/src/test/java/org/apache/struts2/json/JSONUtilTest.java
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Expand Up @@ -79,4 +79,17 @@ public void testSerializeListOfList() throws Exception {
assertEquals("{\"listOfLists\":[[\"1\",\"2\"],[\"3\",\"4\"],[\"5\",\"6\"],[\"7\",\"8\"],[\"9\",\"0\"]]}", actual);
}

public void testIsValidJsonpCallbackName() {
assertTrue(JSONUtil.isValidJsonpCallbackName("exec"));
assertTrue(JSONUtil.isValidJsonpCallbackName("_cb$1"));
assertTrue(JSONUtil.isValidJsonpCallbackName("jQuery123.ajaxCallback"));

assertFalse(JSONUtil.isValidJsonpCallbackName("cb);STRUTS_PROBE_MARKER;("));
assertFalse(JSONUtil.isValidJsonpCallbackName("cb\nSTRUTS_PROBE_MARKER"));
assertFalse(JSONUtil.isValidJsonpCallbackName("</script><STRUTS_PROBE_MARKER>"));
assertFalse(JSONUtil.isValidJsonpCallbackName(""));
assertFalse(JSONUtil.isValidJsonpCallbackName(null));
assertFalse(JSONUtil.isValidJsonpCallbackName("a".repeat(129)));
}

}
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