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| author | Georg Brandl <georg@python.org> | 2012-02-20 18:54:16 (GMT) |
|---|---|---|
| committer | Georg Brandl <georg@python.org> | 2012-02-20 18:54:16 (GMT) |
| commit | 2daf6ae2495c862adf8bc717bfe9964081ea0b10 (patch) | |
| tree | ebd7efe668e4f7842c6d51bdbde47b00f92a57db /Objects/bytesobject.c | |
| parent | ec1712a1662282c909b4cd4cc0c7486646bc9246 (diff) | |
| download | cpython-2daf6ae2495c862adf8bc717bfe9964081ea0b10.zip cpython-2daf6ae2495c862adf8bc717bfe9964081ea0b10.tar.gz cpython-2daf6ae2495c862adf8bc717bfe9964081ea0b10.tar.bz2 | |
Issue #13703: add a way to randomize the hash values of basic types (str, bytes, datetime)
in order to make algorithmic complexity attacks on (e.g.) web apps much more complicated.
The environment variable PYTHONHASHSEED and the new command line flag -R control this
behavior.
Diffstat (limited to 'Objects/bytesobject.c')
| -rw-r--r-- | Objects/bytesobject.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c index f2ee131..e6ab440 100644 --- a/Objects/bytesobject.c +++ b/Objects/bytesobject.c @@ -899,11 +899,21 @@ bytes_hash(PyBytesObject *a) if (a->ob_shash != -1) return a->ob_shash; len = Py_SIZE(a); + /* + We make the hash of the empty string be 0, rather than using + (prefix ^ suffix), since this slightly obfuscates the hash secret + */ + if (len == 0) { + a->ob_shash = 0; + return 0; + } p = (unsigned char *) a->ob_sval; - x = *p << 7; + x = _Py_HashSecret.prefix; + x ^= *p << 7; while (--len >= 0) x = (1000003*x) ^ *p++; x ^= Py_SIZE(a); + x ^= _Py_HashSecret.suffix; if (x == -1) x = -2; a->ob_shash = x; |