IDN: Fix handling of long domain names.

We were incorrectly using sizeof() to calculate the size of the
output array. Note that this change also changes the output size
to 512 to minimize behavioural differences (especially wrt. ICU
checks on sizes).

bug: 30765246
Change-Id: I5d28ddc45d2d6d2bed3e479ca195ed2779b906ed
(cherry picked from commit fffeb3b)

Author: narayank

luni/src/main/native/libcore_icu_NativeIDN.cpp

@@ -37,11 +37,12 @@ static jstring NativeIDN_convertImpl(JNIEnv* env, jclass, jstring javaSrc, jint
     if (src.get() == NULL) {
         return NULL;
     }
-    UChar dst[256];
+    static const size_t kDstSize = 512;
+    UChar dst[kDstSize];
     UErrorCode status = U_ZERO_ERROR;
     size_t resultLength = toAscii
-        ? uidna_IDNToASCII(src.get(), src.size(), &dst[0], sizeof(dst), flags, NULL, &status)
-        : uidna_IDNToUnicode(src.get(), src.size(), &dst[0], sizeof(dst), flags, NULL, &status);
+        ? uidna_IDNToASCII(src.get(), src.size(), &dst[0], kDstSize, flags, NULL, &status)
+        : uidna_IDNToUnicode(src.get(), src.size(), &dst[0], kDstSize, flags, NULL, &status);
     if (U_FAILURE(status)) {
         jniThrowException(env, "java/lang/IllegalArgumentException", u_errorName(status));
         return NULL;

luni/src/test/java/libcore/java/net/IDNTest.java

@@ -37,4 +37,15 @@ public void test_toUnicode_failures() {
         String longInput = makePunyString(512);
         assertEquals(longInput, IDN.toUnicode(longInput));
     }
+
+    // http://b/30765246
+    public void testLongDomainName() {
+        String label63 = "123456789-123456789-123456789-123456789-123456789-123456789-123";
+        String host255 = label63 + "." + label63 + "." + label63 + "." + label63;
+        try {
+            IDN.toASCII(host255.substring(3) + ".com");
+            fail();
+        } catch (IllegalArgumentException expected) {
+        }
+    }
 }