104 lines
3.4 KiB
Python
104 lines
3.4 KiB
Python
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# -*- 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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"""Public-key encryption and signature algorithms.
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Public-key encryption uses two different keys, one for encryption and
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one for decryption. The encryption key can be made public, and the
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decryption key is kept private. Many public-key algorithms can also
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be used to sign messages, and some can *only* be used for signatures.
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"""
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from Crypto.Util.asn1 import (DerSequence, DerInteger, DerBitString,
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DerObjectId, DerNull)
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def _expand_subject_public_key_info(encoded):
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"""Parse a SubjectPublicKeyInfo structure.
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It returns a triple with:
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* OID (string)
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* encoded public key (bytes)
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* Algorithm parameters (bytes or None)
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"""
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#
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# SubjectPublicKeyInfo ::= SEQUENCE {
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# algorithm AlgorithmIdentifier,
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# subjectPublicKey BIT STRING
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# }
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#
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# AlgorithmIdentifier ::= SEQUENCE {
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# algorithm OBJECT IDENTIFIER,
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# parameters ANY DEFINED BY algorithm OPTIONAL
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# }
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#
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spki = DerSequence().decode(encoded, nr_elements=2)
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algo = DerSequence().decode(spki[0], nr_elements=(1,2))
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algo_oid = DerObjectId().decode(algo[0])
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spk = DerBitString().decode(spki[1]).value
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if len(algo) == 1:
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algo_params = None
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else:
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try:
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DerNull().decode(algo[1])
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algo_params = None
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except:
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algo_params = algo[1]
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return algo_oid.value, spk, algo_params
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def _create_subject_public_key_info(algo_oid, secret_key, params=None):
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if params is None:
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params = DerNull()
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spki = DerSequence([
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DerSequence([
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DerObjectId(algo_oid),
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params]),
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DerBitString(secret_key)
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])
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return spki.encode()
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def _extract_subject_public_key_info(x509_certificate):
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"""Extract subjectPublicKeyInfo from a DER X.509 certificate."""
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certificate = DerSequence().decode(x509_certificate, nr_elements=3)
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tbs_certificate = DerSequence().decode(certificate[0],
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nr_elements=list(range(6, 11)))
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index = 5
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try:
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tbs_certificate[0] + 1
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# Version not present
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version = 1
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except TypeError:
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version = DerInteger(explicit=0).decode(tbs_certificate[0]).value
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if version not in (2, 3):
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raise ValueError("Incorrect X.509 certificate version")
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index = 6
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return tbs_certificate[index]
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