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1 files changed, 94 insertions, 0 deletions

diff --git a/lib/Crypto/PublicKey/__init__.py b/lib/Crypto/PublicKey/__init__.py
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+++ b/lib/Crypto/PublicKey/__init__.py
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+# -*- coding: utf-8 -*-
+#
+# ===================================================================
+# The contents of this file are dedicated to the public domain.  To
+# the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.
+# No rights are reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+
+from Crypto.Util.asn1 import (DerSequence, DerInteger, DerBitString,
+                             DerObjectId, DerNull)
+
+
+def _expand_subject_public_key_info(encoded):
+    """Parse a SubjectPublicKeyInfo structure.
+
+    It returns a triple with:
+        * OID (string)
+        * encoded public key (bytes)
+        * Algorithm parameters (bytes or None)
+    """
+
+    #
+    # SubjectPublicKeyInfo  ::=  SEQUENCE  {
+    #   algorithm         AlgorithmIdentifier,
+    #   subjectPublicKey  BIT STRING
+    # }
+    #
+    # AlgorithmIdentifier  ::=  SEQUENCE  {
+    #   algorithm   OBJECT IDENTIFIER,
+    #   parameters  ANY DEFINED BY algorithm OPTIONAL
+    # }
+    #
+
+    spki = DerSequence().decode(encoded, nr_elements=2)
+    algo = DerSequence().decode(spki[0], nr_elements=(1,2))
+    algo_oid = DerObjectId().decode(algo[0])
+    spk = DerBitString().decode(spki[1]).value
+
+    if len(algo) == 1:
+        algo_params = None
+    else:
+        try:
+            DerNull().decode(algo[1])
+            algo_params = None
+        except:
+            algo_params = algo[1]
+
+    return algo_oid.value, spk, algo_params
+
+
+def _create_subject_public_key_info(algo_oid, public_key, params):
+
+    if params is None:
+        algorithm = DerSequence([DerObjectId(algo_oid)])
+    else:
+        algorithm = DerSequence([DerObjectId(algo_oid), params])
+
+    spki = DerSequence([algorithm,
+                        DerBitString(public_key)
+                        ])
+    return spki.encode()
+
+
+def _extract_subject_public_key_info(x509_certificate):
+    """Extract subjectPublicKeyInfo from a DER X.509 certificate."""
+
+    certificate = DerSequence().decode(x509_certificate, nr_elements=3)
+    tbs_certificate = DerSequence().decode(certificate[0],
+                                           nr_elements=range(6, 11))
+
+    index = 5
+    try:
+        tbs_certificate[0] + 1
+        # Version not present
+        version = 1
+    except TypeError:
+        version = DerInteger(explicit=0).decode(tbs_certificate[0]).value
+        if version not in (2, 3):
+            raise ValueError("Incorrect X.509 certificate version")
+        index = 6
+
+    return tbs_certificate[index]