From 864f5d4c127def386dd5cc926ad96934b297f04e Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Sun, 23 Sep 2018 20:07:25 +0200
Subject: [PATCH] UriQuery.c: Fix out-of-bounds-write in ComposeQuery and ...Ex

Reported by Google Autofuzz team
---
 lib/UriQuery.c |  1 +
 test/test.cpp  | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/lib/UriQuery.c b/lib/UriQuery.c
index 5fd6b68..eb22157 100644
--- a/lib/UriQuery.c
+++ b/lib/UriQuery.c
@@ -219,6 +219,7 @@ int URI_FUNC(ComposeQueryEngine)(URI_CHAR * dest,
 
 			/* Copy key */
 			if (firstItem == URI_TRUE) {
+				ampersandLen = 1;
 				firstItem = URI_FALSE;
 			} else {
 				write[0] = _UT('&');
diff --git a/test/test.cpp b/test/test.cpp
index 41e3912..dbb8adb 100644
--- a/test/test.cpp
+++ b/test/test.cpp
@@ -91,6 +91,7 @@ class UriSuite : public Suite {
 		TEST_ADD(UriSuite::testCrash_MakeOwner_Bug20080207)
 		TEST_ADD(UriSuite::testQueryList)
 		TEST_ADD(UriSuite::testQueryListPair)
+		TEST_ADD(UriSuite::testQueryCompositionMathWrite_GoogleAutofuzz113244572)
 		TEST_ADD(UriSuite::testFreeCrash_Bug20080827)
 	}
 
@@ -1501,6 +1502,37 @@ Rule                                | Example | hostSet | absPath | emptySeg
 		testQueryListPairHelper("one=two=three=four", "one", "two=three=four", "one=two%3Dthree%3Dfour");
 	}
 
+	void testQueryCompositionMathWrite_GoogleAutofuzz113244572() {
+		UriQueryListA second = { .key = "\x11", .value = NULL, .next = NULL };
+		UriQueryListA first = { .key = "\x01", .value = "\x02", .next = &second };
+
+		const UriBool spaceToPlus = URI_TRUE;
+		const UriBool normalizeBreaks = URI_FALSE;  /* for factor 3 but 6 */
+
+		const int charsRequired = (3 + 1 + 3) + 1 + (3);
+
+		{
+			// Minimum space to hold everything fine
+			const char * const expected = "%01=%02" "&" "%11";
+			char dest[charsRequired + 1];
+			int charsWritten;
+			TEST_ASSERT(uriComposeQueryExA(dest, &first, sizeof(dest),
+					&charsWritten, spaceToPlus, normalizeBreaks)
+				== URI_SUCCESS);
+			TEST_ASSERT(! strcmp(dest, expected));
+			TEST_ASSERT(charsWritten == strlen(expected) + 1);
+		}
+
+		{
+			// Previous math failed to take ampersand into account
+			char dest[charsRequired + 1 - 1];
+			int charsWritten;
+			TEST_ASSERT(uriComposeQueryExA(dest, &first, sizeof(dest),
+					&charsWritten, spaceToPlus, normalizeBreaks)
+				== URI_ERROR_OUTPUT_TOO_LARGE);
+		}
+	}
+
 	void testFreeCrash_Bug20080827() {
 		char const * const sourceUri = "abc";
 		char const * const baseUri = "http://www.example.org/";