From 3d35a0ea307693a97583a61973e729a5e7db2687 Mon Sep 17 00:00:00 2001
From: Adam Lesinski <adamlesinski@google.com>
Date: Thu, 9 Nov 2017 17:12:17 -0800
Subject: [PATCH] Check for null-terminator in ResStringPool::string8At

All other stringAt methods check for null termination. Be consistent
so that upper levels don't end up with huge corrupt strings.

Bug: 62537081
Test: none
Change-Id: I17bdfb0c1e34507b66c6cad651bbdb12c5d4c417
---
 libs/androidfw/ResourceTypes.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libs/androidfw/ResourceTypes.cpp b/libs/androidfw/ResourceTypes.cpp
index 5d248c24c3763..3fe75cffaa713 100644
--- a/libs/androidfw/ResourceTypes.cpp
+++ b/libs/androidfw/ResourceTypes.cpp
@@ -812,7 +812,13 @@ const char* ResStringPool::string8At(size_t idx, size_t* outLen) const
             *outLen = encLen;
 
             if ((uint32_t)(str+encLen-strings) < mStringPoolSize) {
-                return (const char*)str;
+                // Reject malformed (non null-terminated) strings
+                if (str[encLen] != 0x00) {
+                    ALOGW("Bad string block: string #%d is not null-terminated",
+                          (int)idx);
+                    return NULL;
+                }
+              return (const char*)str;
             } else {
                 ALOGW("Bad string block: string #%d extends to %d, past end at %d\n",
                         (int)idx, (int)(str+encLen-strings), (int)mStringPoolSize);