Extract crypto stuff to dkim.crypto.

dkim/__init__.py

@@ -5,15 +5,10 @@ import time
 
 import dns.resolver
 
-from dkim.asn1 import (
-    asn1_build,
-    asn1_parse,
-    BIT_STRING,
-    INTEGER,
-    SEQUENCE,
-    OBJECT_IDENTIFIER,
-    OCTET_STRING,
-    NULL,
+from dkim.crypto import (
+    EMSA_PKCS1_v1_5_encode,
+    parse_private_key,
+    parse_public_key,
     )
 
 __all__ = [
@@ -87,22 +82,6 @@ def _remove(s, t):
     assert i >= 0
     return s[:i] + s[i+len(t):]
 
-
-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 ParameterError("Hash too large for modulus")
-    return "\x00\x01"+"\xff"*(modlen-len(dinfo)-3)+"\x00"+dinfo
-
-
 def hash_headers(hasher, canonicalize_headers, headers, include_headers,
                  sigheaders, sig):
     sign_headers = []
@@ -126,33 +105,6 @@ def hash_headers(hasher, canonicalize_headers, headers, include_headers,
         hasher.update(x[1])
 
 
-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 validate_signature_fields(sig, debuglog=None):
     mandatory_fields = ('v', 'a', 'b', 'bh', 'd', 'h', 's')
     for field in mandatory_fields:
@@ -200,38 +152,6 @@ def validate_signature_fields(sig, debuglog=None):
             return False
     return True
 
-
-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,),
-    ])
-]
-
 # These values come from RFC 3447, section 9.2 Notes, page 43.
 HASHID_SHA1 = "\x2b\x0e\x03\x02\x1a"
 HASHID_SHA256 = "\x60\x86\x48\x01\x65\x03\x04\x02\x01"

dkim/crypto.py

@@ -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
+