173 lines
6 KiB
Python
173 lines
6 KiB
Python
# -*- coding: utf-8 -*-
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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"""SHA-256 cryptographic hash algorithm.
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SHA-256 belongs to the SHA-2_ family of cryptographic hashes.
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It produces the 256 bit digest of a message.
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>>> from Crypto.Hash import SHA256
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>>>
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>>> h = SHA256.new()
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>>> h.update(b'Hello')
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>>> print h.hexdigest()
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*SHA* stands for Secure Hash Algorithm.
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.. _SHA-2: http://csrc.nist.gov/publications/fips/fips180-2/fips180-4.pdf
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"""
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from Crypto.Util.py3compat import *
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from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
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VoidPointer, SmartPointer,
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create_string_buffer,
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get_raw_buffer, c_size_t,
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expect_byte_string)
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_raw_sha256_lib = load_pycryptodome_raw_lib("Crypto.Hash._SHA256",
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"""
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int SHA256_init(void **shaState);
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int SHA256_destroy(void *shaState);
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int SHA256_update(void *hs,
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const uint8_t *buf,
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size_t len);
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int SHA256_digest(const void *shaState,
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uint8_t digest[32]);
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int SHA256_copy(const void *src, void *dst);
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""")
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class SHA256Hash(object):
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"""Class that implements a SHA-256 hash
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"""
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#: The size of the resulting hash in bytes.
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digest_size = 32
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#: The internal block size of the hash algorithm in bytes.
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block_size = 64
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#: ASN.1 Object ID
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oid = "2.16.840.1.101.3.4.2.1"
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def __init__(self, data=None):
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state = VoidPointer()
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result = _raw_sha256_lib.SHA256_init(state.address_of())
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if result:
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raise ValueError("Error %d while instantiating SHA256"
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% result)
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self._state = SmartPointer(state.get(),
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_raw_sha256_lib.SHA256_destroy)
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if data:
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self.update(data)
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def update(self, data):
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"""Continue hashing of a message by consuming the next chunk of data.
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Repeated calls are equivalent to a single call with the concatenation
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of all the arguments. In other words:
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>>> m.update(a); m.update(b)
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is equivalent to:
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>>> m.update(a+b)
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:Parameters:
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data : byte string
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The next chunk of the message being hashed.
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"""
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expect_byte_string(data)
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result = _raw_sha256_lib.SHA256_update(self._state.get(),
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data,
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c_size_t(len(data)))
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if result:
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raise ValueError("Error %d while instantiating SHA256"
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% result)
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def digest(self):
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"""Return the **binary** (non-printable) digest of the message that has been hashed so far.
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This method does not change the state of the hash object.
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You can continue updating the object after calling this function.
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:Return: A byte string of `digest_size` bytes. It may contain non-ASCII
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characters, including null bytes.
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"""
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bfr = create_string_buffer(self.digest_size)
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result = _raw_sha256_lib.SHA256_digest(self._state.get(),
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bfr)
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if result:
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raise ValueError("Error %d while instantiating SHA256"
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% result)
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return get_raw_buffer(bfr)
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def hexdigest(self):
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"""Return the **printable** digest of the message that has been hashed so far.
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This method does not change the state of the hash object.
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:Return: A string of 2* `digest_size` characters. It contains only
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hexadecimal ASCII digits.
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"""
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return "".join(["%02x" % bord(x) for x in self.digest()])
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def copy(self):
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"""Return a copy ("clone") of the hash object.
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The copy will have the same internal state as the original hash
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object.
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This can be used to efficiently compute the digests of strings that
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share a common initial substring.
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:Return: A hash object of the same type
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"""
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clone = SHA256Hash()
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result = _raw_sha256_lib.SHA256_copy(self._state.get(),
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clone._state.get())
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if result:
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raise ValueError("Error %d while copying SHA256" % result)
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return clone
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def new(self, data=None):
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return SHA256Hash(data)
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def new(data=None):
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"""Return a fresh instance of the hash object.
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:Parameters:
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data : byte string
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The very first chunk of the message to hash.
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It is equivalent to an early call to `SHA256Hash.update()`.
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Optional.
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:Return: A `SHA256Hash` object
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"""
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return SHA256Hash().new(data)
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#: The size of the resulting hash in bytes.
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digest_size = SHA256Hash.digest_size
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#: The internal block size of the hash algorithm in bytes.
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block_size = SHA256Hash.block_size
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