- 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.
diff --git a/Objects/bufferobject.c b/Objects/bufferobject.c
index 0f7e763..c52f0bc 100644
--- a/Objects/bufferobject.c
+++ b/Objects/bufferobject.c
@@ -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;