Ensure library file starts with 'lib/' prefix.

Test: ApkParsing_test.cpp
Change-Id: I3a1ac8c10b315e49ec668ff357aafe861cd2d0fe
diff --git a/libs/androidfw/ApkParsing.cpp b/libs/androidfw/ApkParsing.cpp
index 32d2c5b..7eedfdb 100644
--- a/libs/androidfw/ApkParsing.cpp
+++ b/libs/androidfw/ApkParsing.cpp
@@ -56,6 +56,11 @@
         return nullptr;
     }
 
+    // Make sure file starts with 'lib/' prefix.
+    if (strncmp(fileName, APK_LIB.data(), APK_LIB_LEN) != 0) {
+        return nullptr;
+    }
+
     // Make sure there aren't subdirectories by checking if the next / after lib/ is the last slash
     if (memchr(fileName + APK_LIB_LEN, '/', fileNameLen - APK_LIB_LEN) != lastSlash) {
         return nullptr;