mirror of
https://github.com/PiBrewing/craftbeerpi4.git
synced 2024-11-30 10:44:14 +01:00
66 lines
2.3 KiB
Python
66 lines
2.3 KiB
Python
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import absolute_import, division, print_function
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from cryptography.exceptions import InvalidSignature
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from cryptography.hazmat.primitives import constant_time
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_POLY1305_TAG_SIZE = 16
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_POLY1305_KEY_SIZE = 32
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class _Poly1305Context(object):
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def __init__(self, backend, key):
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self._backend = backend
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key_ptr = self._backend._ffi.from_buffer(key)
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# This function copies the key into OpenSSL-owned memory so we don't
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# need to retain it ourselves
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evp_pkey = self._backend._lib.EVP_PKEY_new_raw_private_key(
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self._backend._lib.NID_poly1305,
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self._backend._ffi.NULL,
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key_ptr,
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len(key),
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)
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self._backend.openssl_assert(evp_pkey != self._backend._ffi.NULL)
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self._evp_pkey = self._backend._ffi.gc(
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evp_pkey, self._backend._lib.EVP_PKEY_free
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)
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ctx = self._backend._lib.EVP_MD_CTX_new()
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self._backend.openssl_assert(ctx != self._backend._ffi.NULL)
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self._ctx = self._backend._ffi.gc(
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ctx, self._backend._lib.EVP_MD_CTX_free
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)
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res = self._backend._lib.EVP_DigestSignInit(
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self._ctx,
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self._backend._ffi.NULL,
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self._backend._ffi.NULL,
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self._backend._ffi.NULL,
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self._evp_pkey,
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)
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self._backend.openssl_assert(res == 1)
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def update(self, data):
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data_ptr = self._backend._ffi.from_buffer(data)
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res = self._backend._lib.EVP_DigestSignUpdate(
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self._ctx, data_ptr, len(data)
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)
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self._backend.openssl_assert(res != 0)
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def finalize(self):
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buf = self._backend._ffi.new("unsigned char[]", _POLY1305_TAG_SIZE)
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outlen = self._backend._ffi.new("size_t *")
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res = self._backend._lib.EVP_DigestSignFinal(self._ctx, buf, outlen)
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self._backend.openssl_assert(res != 0)
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self._backend.openssl_assert(outlen[0] == _POLY1305_TAG_SIZE)
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return self._backend._ffi.buffer(buf)[: outlen[0]]
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def verify(self, tag):
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mac = self.finalize()
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if not constant_time.bytes_eq(mac, tag):
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raise InvalidSignature("Value did not match computed tag.")
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