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bpo-31933: fix blake2 multi-byte params on big endian platforms (#4250)

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All Blake2 params have to be encoded in little-endian byte order. For
the two multi-byte integer params, leaf_length and node_offset, that
means that assigning a native-endian integer to them appears to work on
little-endian platforms, but gives the wrong result on big-endian. The
current libb2 API doesn't make that very clear, and @sneves is working
on new API functions in the GH issue above. In the meantime, we can work
around the problem by explicitly assigning little-endian values to the
parameter block.

See https://github.com/BLAKE2/libb2/issues/12.
This commit is contained in:
Jack O'Connor 2017-11-03 15:02:41 -04:00 • committed by Christian Heimes
parent f6f90ff079
commit dcfb0e3c04
4 changed files with 46 additions and 4 deletions
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6
Modules/_blake2/blake2b_impl.c
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@ -162,7 +162,8 @@ py_blake2b_new_impl(PyTypeObject *type, PyObject *data, int digest_size,
goto error;
}
}
self->param.leaf_length = (unsigned int)leaf_size;
// NB: Simple assignment here would be incorrect on big endian platforms.
store32(&(self->param.leaf_length), leaf_size);
if (node_offset_obj != NULL) {
node_offset = PyLong_AsUnsignedLongLong(node_offset_obj);
@ -178,7 +179,8 @@ py_blake2b_new_impl(PyTypeObject *type, PyObject *data, int digest_size,
}
store48(&(self->param.node_offset), node_offset);
#else
self->param.node_offset = node_offset;
// NB: Simple assignment here would be incorrect on big endian platforms.
store64(&(self->param.node_offset), node_offset);
#endif
if (node_depth < 0 || node_depth > 255) {