Mercurial > cpython-lru_cache-weakref

diff Objects/bufferobject.c @ 75100:6b7704fe1be1 2.6

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
- Issue #13703: oCERT-2011-003: add -R command-line option and PYTHONHASHSEED environment variable, to provide an opt-in way to protect against denial of service attacks due to hash collisions within the dict and set types. Patch by David Malcolm, based on work by Victor Stinner.
author Barry Warsaw <barry@python.org>
date Mon, 20 Feb 2012 20:42:21 -0500
parents 787b969d37f0
children 6b3217b96a77
line wrap: on
line diff
--- a/Objects/bufferobject.c	Mon Feb 20 14:43:22 2012 -0500
+++ b/Objects/bufferobject.c	Mon Feb 20 20:42:21 2012 -0500
@@ -334,10 +334,20 @@
         return -1;
     p = (unsigned char *) ptr;
     len = size;
-    x = *p << 7;
+    /*
+      We make the hash of the empty buffer be 0, rather than using
+      (prefix ^ suffix), since this slightly obfuscates the hash secret
+    */
+    if (len == 0) {
+        self->b_hash = 0;
+        return 0;
+    }
+    x = _Py_HashSecret.prefix;
+    x ^= *p << 7;
     while (--len >= 0)
         x = (1000003*x) ^ *p++;
     x ^= size;
+    x ^= _Py_HashSecret.suffix;
     if (x == -1)
         x = -2;
     self->b_hash = x;