complain when nbytes > buflen to fix possible buffer overflow (closes #20246)

benjaminp · benjaminp · commit fbf648ebba32 · 2014-01-13T22:59:38.000-05:00
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
@@ -1968,6 +1968,14 @@ def testRecvFromIntoMemoryview(self):
 
     _testRecvFromIntoMemoryview = _testRecvFromIntoArray
 
+    def testRecvFromIntoSmallBuffer(self):
+        # See issue #20246.
+        buf = bytearray(8)
+        self.assertRaises(ValueError, self.cli_conn.recvfrom_into, buf, 1024)
+
+    def _testRecvFromIntoSmallBuffer(self):
+        self.serv_conn.send(MSG*2048)
+
 
 TIPC_STYPE = 2000
 TIPC_LOWER = 200
diff --git a/Misc/ACKS b/Misc/ACKS
@@ -1020,6 +1020,7 @@ Eric V. Smith
 Christopher Smith
 Gregory P. Smith
 Roy Smith
+Ryan Smith-Roberts
 Rafal Smotrzyk
 Dirk Soede
 Paul Sokolovsky
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -10,6 +10,8 @@ What's New in Python 3.2.6?
 Library
 -------
 
+- Issue #20246: Fix buffer overflow in socket.recvfrom_into.
+
 - Issue #12226: HTTPS is now used by default when connecting to PyPI.
 
 - Issue #19435: Fix directory traversal attack on CGIHttpRequestHandler.
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
@@ -2598,6 +2598,11 @@ sock_recvfrom_into(PySocketSockObject *s, PyObject *args, PyObject* kwds)
     if (recvlen == 0) {
         /* If nbytes was not specified, use the buffer's length */
         recvlen = buflen;
+    } else if (recvlen > buflen) {
+        PyBuffer_Release(&pbuf);
+        PyErr_SetString(PyExc_ValueError,
+                        "nbytes is greater than the length of the buffer");
+        return NULL;
     }
 
     readlen = sock_recvfrom_guts(s, buf, recvlen, flags, &addr);
