SERVER-10259 Do not return pointer into temporary string

Convert the location found within the temporary string into the
equivalent (and correct) location in the source string.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/mongo/platform/strcasestr.cpp b/src/mongo/platform/strcasestr.cpp
index 748f1bf0cca..1bcd0a37094 100644
--- a/src/mongo/platform/strcasestr.cpp
+++ b/src/mongo/platform/strcasestr.cpp
@@ -59,7 +59,12 @@ namespace pal {
                        needleLower.begin(),
                        ::tolower);
 
-        return strstr(haystackLower.c_str(), needleLower.c_str());
+        // Use strstr() to find 'lowercased needle' in 'lowercased haystack'
+        // If found, use the location to compute the matching location in the original string
+        // If not found, return NULL
+        const char* haystackLowerStart = haystackLower.c_str();
+        const char* location = strstr(haystackLowerStart, needleLower.c_str());
+        return location ? (haystack + (location - haystackLowerStart)) : NULL;
     }
 
 #if defined(__sunos__)