Extract crypto stuff to dkim.crypto.

2011-03-09 23:27:04 +11:00
parent b6d3502f9e
commit 6f715a1a01
2 changed files with 114 additions and 84 deletions
@@ -0,0 +1,110 @@
+# This software is provided 'as-is', without any express or implied
+# warranty.  In no event will the author be held liable for any damages
+# arising from the use of this software.
+#
+# Permission is granted to anyone to use this software for any purpose,
+# including commercial applications, and to alter it and redistribute it
+# freely, subject to the following restrictions:
+#
+# 1. The origin of this software must not be misrepresented; you must not
+#    claim that you wrote the original software. If you use this software
+#    in a product, an acknowledgment in the product documentation would be
+#    appreciated but is not required.
+# 2. Altered source versions must be plainly marked as such, and must not be
+#    misrepresented as being the original software.
+# 3. This notice may not be removed or altered from any source distribution.
+#
+# Copyright (c) 2008 Greg Hewgill http://hewgill.com
+# Copyright (c) 2011 William Grant <me@williamgrant.id.au>
+
+__all__ = [
+    'EMSA_PKCS1_v1_5_encode',
+    'parse_private_key',
+    'parse_public_key',
+    ]
+
+from dkim.asn1 import (
+    asn1_build,
+    asn1_parse,
+    BIT_STRING,
+    INTEGER,
+    SEQUENCE,
+    OBJECT_IDENTIFIER,
+    OCTET_STRING,
+    NULL,
+    )
+
+
+ASN1_Object = [
+    (SEQUENCE, [
+        (SEQUENCE, [
+            (OBJECT_IDENTIFIER,),
+            (NULL,),
+        ]),
+        (BIT_STRING,),
+    ])
+]
+
+ASN1_RSAPublicKey = [
+    (SEQUENCE, [
+        (INTEGER,),
+        (INTEGER,),
+    ])
+]
+
+ASN1_RSAPrivateKey = [
+    (SEQUENCE, [
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+        (INTEGER,),
+    ])
+]
+
+
+def parse_public_key(data):
+    x = asn1_parse(ASN1_Object, data)
+    # Not sure why the [1:] is necessary to skip a byte.
+    pkd = asn1_parse(ASN1_RSAPublicKey, x[0][1][1:])
+    pk = {
+        'modulus': pkd[0][0],
+        'publicExponent': pkd[0][1],
+    }
+    return pk
+
+
+def parse_private_key(data):
+    pka = asn1_parse(ASN1_RSAPrivateKey, data)
+    pk = {
+        'version': pka[0][0],
+        'modulus': pka[0][1],
+        'publicExponent': pka[0][2],
+        'privateExponent': pka[0][3],
+        'prime1': pka[0][4],
+        'prime2': pka[0][5],
+        'exponent1': pka[0][6],
+        'exponent2': pka[0][7],
+        'coefficient': pka[0][8],
+    }
+    return pk
+
+
+def EMSA_PKCS1_v1_5_encode(digest, modlen, hashid):
+    dinfo = asn1_build(
+        (SEQUENCE, [
+            (SEQUENCE, [
+                (OBJECT_IDENTIFIER, hashid),
+                (NULL, None),
+            ]),
+            (OCTET_STRING, digest),
+        ]),
+    )
+    if len(dinfo)+3 > modlen:
+        raise Exception("Hash too large for modulus") # XXX: DKIMException
+    return "\x00\x01"+"\xff"*(modlen-len(dinfo)-3)+"\x00"+dinfo
+