SERVER-9502 prohibit _id as RegEx

Otherwise, this breaks when replication attempts to do a query with the regular expression as _id.

3 files changed, 36 insertions, 2 deletions

diff --git a/jstests/replsets/regex.js b/jstests/replsets/regex.js
new file mode 100644
index 00000000000..0a2db95acb4
--- /dev/null
+++ b/jstests/replsets/regex.js
@@ -0,0 +1,19 @@
+// don't allow regex as _id: SERVER-9502
+
+var replTest = new ReplSetTest( {name: "server9502", nodes: 2} );
+var nodes = replTest.startSet();
+replTest.initiate();
+var master = replTest.getMaster();
+var mdb = master.getDB("test");
+mdb.foo.insert({ _id: "ABCDEF" });
+var gle = master.getDB("test").runCommand({getLastError : 1, w : 2, wtimeout : 60000});
+assert(gle.err === null);
+
+mdb.foo.insert({ _id: /^A/ });
+var gle = master.getDB("test").runCommand({getLastError : 1, w : 2, wtimeout : 60000});
+assert(gle.code === 16814);
+
+// _id doesn't have to be first; still disallowed
+mdb.foo.insert({ xxx: "ABCDEF", _id: /ABCDEF/ });
+var gle = master.getDB("test").runCommand({getLastError : 1, w : 2, wtimeout : 60000});
+assert(gle.code === 16814);
diff --git a/src/mongo/db/instance.cpp b/src/mongo/db/instance.cpp
index 39f35945610..225ae66120c 100644
--- a/src/mongo/db/instance.cpp
+++ b/src/mongo/db/instance.cpp
@@ -742,13 +742,21 @@ namespace mongo {
     void checkAndInsert(const char *ns, /*modifies*/BSONObj& js) { 
         uassert( 10059 , "object to insert too large", js.objsize() <= BSONObjMaxUserSize);
         {
-            // check no $ modifiers.  note we only check top level.  (scanning deep would be quite expensive)
             BSONObjIterator i( js );
             while ( i.more() ) {
                 BSONElement e = i.next();
-                uassert( 13511 , "document to insert can't have $ fields" , e.fieldName()[0] != '$' );
+
+                // check no $ modifiers.  note we only check top level.  
+                // (scanning deep would be quite expensive)
+                uassert( 13511, "document to insert can't have $ fields", e.fieldName()[0] != '$' );
+                
+                // check no regexp for _id (SERVER-9502)
+                if (str::equals(e.fieldName(), "_id")) {
+                    uassert(16814, "can't use a regex for _id", e.type() != RegEx);
+                }
             }
         }
+
         theDataFileMgr.insertWithObjMod(ns,
                                         // May be modified in the call to add an _id field.
                                         js,
diff --git a/src/mongo/db/jsobj.cpp b/src/mongo/db/jsobj.cpp
index dcb105e50ba..16659ed8cd6 100644
--- a/src/mongo/db/jsobj.cpp
+++ b/src/mongo/db/jsobj.cpp
@@ -893,6 +893,13 @@ namespace mongo {
                     ;
             }
 
+            // check no regexp for _id (SERVER-9502)
+            if (mongoutils::str::equals(e.fieldName(), "_id")) {
+                if (e.type() == RegEx) {
+                    return false;
+                }
+            }
+
             if ( e.mayEncapsulate() ) {
                 switch ( e.type() ) {
                 case Object: