Factor out most crypto bits into their own functions and modules, where they can sensibly be tested.
This commit is contained in:
William Grant
+31
-209
@@ -15,6 +15,7 @@
|
||||
# 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>
|
||||
|
||||
import base64
|
||||
import hashlib
|
||||
@@ -23,6 +24,14 @@ import time
|
||||
|
||||
import dns.resolver
|
||||
|
||||
from dkim.crypto import (
|
||||
DigestTooLargeError,
|
||||
parse_private_key,
|
||||
parse_public_key,
|
||||
RSASSA_PKCS1_v1_5_sign,
|
||||
RSASSA_PKCS1_v1_5_verify,
|
||||
UnparsableKeyError,
|
||||
)
|
||||
from dkim.util import (
|
||||
InvalidTagValueList,
|
||||
parse_tag_value,
|
||||
@@ -99,29 +108,6 @@ def _remove(s, t):
|
||||
assert i >= 0
|
||||
return s[:i] + s[i+len(t):]
|
||||
|
||||
|
||||
def EMSA_PKCS1_v1_5_encode(digest, modlen, hashid):
|
||||
"""Encode a digest with EMSA-PKCS1-v1_5.
|
||||
|
||||
Defined in RFC3447 section 9.2.
|
||||
|
||||
@param digest: A digest value to encode.
|
||||
@param modlen: The desired message length.
|
||||
@param hashid: The ID of the hash used to generate the digest.
|
||||
"""
|
||||
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 message header fields."""
|
||||
@@ -146,22 +132,6 @@ def hash_headers(hasher, canonicalize_headers, headers, include_headers,
|
||||
hasher.update(x[1])
|
||||
|
||||
|
||||
def parse_public_key(data):
|
||||
"""Parse an RSA public key.
|
||||
|
||||
@param data: A DER-encoded X.509 subjectPublicKeyInfo
|
||||
containing an RFC3447 RSAPublicKey.
|
||||
"""
|
||||
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 validate_signature_fields(sig, debuglog=None):
|
||||
"""Validate DKIM-Signature fields.
|
||||
|
||||
@@ -217,148 +187,10 @@ def validate_signature_fields(sig, debuglog=None):
|
||||
return False
|
||||
return True
|
||||
|
||||
|
||||
INTEGER = 0x02
|
||||
BIT_STRING = 0x03
|
||||
OCTET_STRING = 0x04
|
||||
NULL = 0x05
|
||||
OBJECT_IDENTIFIER = 0x06
|
||||
SEQUENCE = 0x30
|
||||
|
||||
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 asn1_parse(template, data):
|
||||
"""Parse a data structure according to ASN.1 template.
|
||||
|
||||
@param template: A list of tuples comprising the ASN.1 template.
|
||||
@param data: A list of bytes to parse.
|
||||
|
||||
"""
|
||||
|
||||
r = []
|
||||
i = 0
|
||||
for t in template:
|
||||
tag = ord(data[i])
|
||||
i += 1
|
||||
if tag == t[0]:
|
||||
length = ord(data[i])
|
||||
i += 1
|
||||
if length & 0x80:
|
||||
n = length & 0x7f
|
||||
length = 0
|
||||
for j in range(n):
|
||||
length = (length << 8) | ord(data[i])
|
||||
i += 1
|
||||
if tag == INTEGER:
|
||||
n = 0
|
||||
for j in range(length):
|
||||
n = (n << 8) | ord(data[i])
|
||||
i += 1
|
||||
r.append(n)
|
||||
elif tag == BIT_STRING:
|
||||
r.append(data[i:i+length])
|
||||
i += length
|
||||
elif tag == NULL:
|
||||
assert length == 0
|
||||
r.append(None)
|
||||
elif tag == OBJECT_IDENTIFIER:
|
||||
r.append(data[i:i+length])
|
||||
i += length
|
||||
elif tag == SEQUENCE:
|
||||
r.append(asn1_parse(t[1], data[i:i+length]))
|
||||
i += length
|
||||
else:
|
||||
raise KeyFormatError("Unexpected tag in template: %02x" % tag)
|
||||
else:
|
||||
raise KeyFormatError("Unexpected tag (got %02x, expecting %02x)" % (tag, t[0]))
|
||||
return r
|
||||
|
||||
def asn1_length(n):
|
||||
"""Return a string representing a field length in ASN.1 format."""
|
||||
assert n >= 0
|
||||
if n < 0x7f:
|
||||
return chr(n)
|
||||
r = ""
|
||||
while n > 0:
|
||||
r = chr(n & 0xff) + r
|
||||
n >>= 8
|
||||
return r
|
||||
|
||||
def asn1_build(node):
|
||||
"""Build an ASN.1 data structure based on pairs of (type, data)."""
|
||||
if node[0] == OCTET_STRING:
|
||||
return chr(OCTET_STRING) + asn1_length(len(node[1])) + node[1]
|
||||
if node[0] == NULL:
|
||||
assert node[1] is None
|
||||
return chr(NULL) + asn1_length(0)
|
||||
elif node[0] == OBJECT_IDENTIFIER:
|
||||
return chr(OBJECT_IDENTIFIER) + asn1_length(len(node[1])) + node[1]
|
||||
elif node[0] == SEQUENCE:
|
||||
r = ""
|
||||
for x in node[1]:
|
||||
r += asn1_build(x)
|
||||
return chr(SEQUENCE) + asn1_length(len(r)) + r
|
||||
else:
|
||||
raise InternalError("Unexpected tag in template: %02x" % node[0])
|
||||
|
||||
# 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"
|
||||
|
||||
def str2int(s):
|
||||
"""Convert an octet string to an integer. Octet string assumed to represent a positive integer."""
|
||||
r = 0
|
||||
for c in s:
|
||||
r = (r << 8) | ord(c)
|
||||
return r
|
||||
|
||||
def int2str(n, length = -1):
|
||||
"""Convert an integer to an octet string. Number must be positive.
|
||||
|
||||
@param n: Number to convert.
|
||||
@param length: Minimum length, or -1 to return the smallest number of bytes that represent the integer.
|
||||
|
||||
"""
|
||||
|
||||
assert n >= 0
|
||||
r = []
|
||||
while length < 0 or len(r) < length:
|
||||
r.append(chr(n & 0xff))
|
||||
n >>= 8
|
||||
if length < 0 and n == 0: break
|
||||
r.reverse()
|
||||
assert length < 0 or len(r) == length
|
||||
return r
|
||||
|
||||
def rfc822_parse(message):
|
||||
"""Parse a message in RFC822 format.
|
||||
|
||||
@@ -443,18 +275,10 @@ def sign(message, selector, domain, privkey, identity=None, canonicalize=(Simple
|
||||
raise KeyFormatError(str(e))
|
||||
if debuglog is not None:
|
||||
print >>debuglog, " ".join("%02x" % ord(x) for x in pkdata)
|
||||
pka = asn1_parse(ASN1_RSAPrivateKey, pkdata)
|
||||
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],
|
||||
}
|
||||
try:
|
||||
pk = parse_private_key(pkdata)
|
||||
except UnparsableKeyError, e:
|
||||
raise KeyFormatError(str(e))
|
||||
|
||||
if identity is not None and not identity.endswith(domain):
|
||||
raise ParameterError("identity must end with domain")
|
||||
@@ -503,10 +327,12 @@ def sign(message, selector, domain, privkey, identity=None, canonicalize=(Simple
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "sign digest:", " ".join("%02x" % ord(x) for x in d)
|
||||
|
||||
modlen = len(int2str(pk['modulus']))
|
||||
encoded = EMSA_PKCS1_v1_5_encode(d, modlen, HASHID_SHA256)
|
||||
sig2 = int2str(pow(str2int(encoded), pk['privateExponent'], pk['modulus']), modlen)
|
||||
sig += base64.b64encode(''.join(sig2))
|
||||
try:
|
||||
sig2 = RSASSA_PKCS1_v1_5_sign(
|
||||
d, HASHID_SHA256, pk['privateExponent'], pk['modulus'])
|
||||
except DigestTooLargeError:
|
||||
raise ParameterError("digest too large for modulus")
|
||||
sig += base64.b64encode(sig2)
|
||||
|
||||
return sig + "\r\n"
|
||||
|
||||
@@ -597,10 +423,12 @@ def verify(message, debuglog=None, dnsfunc=dnstxt):
|
||||
pub = parse_tag_value(s)
|
||||
except InvalidTagValueList:
|
||||
return False
|
||||
pk = parse_public_key(base64.b64decode(pub['p']))
|
||||
modlen = len(int2str(pk['modulus']))
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "modlen:", modlen
|
||||
try:
|
||||
pk = parse_public_key(base64.b64decode(pub['p']))
|
||||
except UnparsableKeyError, e:
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "could not parse public key: %s" % e
|
||||
return False
|
||||
|
||||
include_headers = re.split(r"\s*:\s*", sig['h'])
|
||||
h = hasher()
|
||||
@@ -609,17 +437,11 @@ def verify(message, debuglog=None, dnsfunc=dnstxt):
|
||||
d = h.digest()
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "verify digest:", " ".join("%02x" % ord(x) for x in d)
|
||||
signature = base64.b64decode(re.sub(r"\s+", "", sig['b']))
|
||||
try:
|
||||
sig2 = EMSA_PKCS1_v1_5_encode(d, modlen, hashid)
|
||||
except ParameterError:
|
||||
return RSASSA_PKCS1_v1_5_verify(
|
||||
d, hashid, signature, pk['publicExponent'], pk['modulus'])
|
||||
except DigestTooLargeError:
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "digest too large for modulus"
|
||||
return False
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "sig2:", " ".join("%02x" % ord(x) for x in sig2)
|
||||
print >>debuglog, sig['b']
|
||||
print >>debuglog, re.sub(r"\s+", "", sig['b'])
|
||||
v = int2str(pow(str2int(base64.b64decode(re.sub(r"\s+", "", sig['b']))), pk['publicExponent'], pk['modulus']), modlen)
|
||||
if debuglog is not None:
|
||||
print >>debuglog, "v:", " ".join("%02x" % ord(x) for x in v)
|
||||
assert len(v) == len(sig2)
|
||||
# Byte-by-byte compare of signatures
|
||||
return not [1 for x in zip(v, sig2) if x[0] != x[1]]
|
||||
|
||||
+128
@@ -0,0 +1,128 @@
|
||||
# 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__ = [
|
||||
'asn1_build',
|
||||
'asn1_parse',
|
||||
'ASN1FormatError',
|
||||
'BIT_STRING',
|
||||
'INTEGER',
|
||||
'SEQUENCE',
|
||||
'OBJECT_IDENTIFIER',
|
||||
'OCTET_STRING',
|
||||
'NULL',
|
||||
]
|
||||
|
||||
INTEGER = 0x02
|
||||
BIT_STRING = 0x03
|
||||
OCTET_STRING = 0x04
|
||||
NULL = 0x05
|
||||
OBJECT_IDENTIFIER = 0x06
|
||||
SEQUENCE = 0x30
|
||||
|
||||
|
||||
class ASN1FormatError(Exception):
|
||||
pass
|
||||
|
||||
|
||||
def asn1_parse(template, data):
|
||||
"""Parse a data structure according to an ASN.1 template.
|
||||
|
||||
@param template: tuples comprising the ASN.1 template
|
||||
@param data: byte string data to parse
|
||||
@return: decoded structure
|
||||
"""
|
||||
|
||||
r = []
|
||||
i = 0
|
||||
for t in template:
|
||||
tag = ord(data[i])
|
||||
i += 1
|
||||
if tag == t[0]:
|
||||
length = ord(data[i])
|
||||
i += 1
|
||||
if length & 0x80:
|
||||
n = length & 0x7f
|
||||
length = 0
|
||||
for j in range(n):
|
||||
length = (length << 8) | ord(data[i])
|
||||
i += 1
|
||||
if tag == INTEGER:
|
||||
n = 0
|
||||
for j in range(length):
|
||||
n = (n << 8) | ord(data[i])
|
||||
i += 1
|
||||
r.append(n)
|
||||
elif tag == BIT_STRING:
|
||||
r.append(data[i:i+length])
|
||||
i += length
|
||||
elif tag == NULL:
|
||||
assert length == 0
|
||||
r.append(None)
|
||||
elif tag == OBJECT_IDENTIFIER:
|
||||
r.append(data[i:i+length])
|
||||
i += length
|
||||
elif tag == SEQUENCE:
|
||||
r.append(asn1_parse(t[1], data[i:i+length]))
|
||||
i += length
|
||||
else:
|
||||
raise ASN1FormatError(
|
||||
"Unexpected tag in template: %02x" % tag)
|
||||
else:
|
||||
raise ASN1FormatError(
|
||||
"Unexpected tag (got %02x, expecting %02x)" % (tag, t[0]))
|
||||
return r
|
||||
|
||||
|
||||
def asn1_length(n):
|
||||
"""Return a string representing a field length in ASN.1 format.
|
||||
|
||||
@param n: integer field length
|
||||
@return: ASN.1 field length
|
||||
"""
|
||||
assert n >= 0
|
||||
if n < 0x7f:
|
||||
return chr(n)
|
||||
r = ""
|
||||
while n > 0:
|
||||
r = chr(n & 0xff) + r
|
||||
n >>= 8
|
||||
return r
|
||||
|
||||
|
||||
def asn1_build(node):
|
||||
"""Build a DER-encoded ASN.1 data structure.
|
||||
|
||||
@param node: (type, data) tuples comprising the ASN.1 structure
|
||||
@return: DER-encoded ASN.1 byte string
|
||||
"""
|
||||
if node[0] == OCTET_STRING:
|
||||
return chr(OCTET_STRING) + asn1_length(len(node[1])) + node[1]
|
||||
if node[0] == NULL:
|
||||
assert node[1] is None
|
||||
return chr(NULL) + asn1_length(0)
|
||||
elif node[0] == OBJECT_IDENTIFIER:
|
||||
return chr(OBJECT_IDENTIFIER) + asn1_length(len(node[1])) + node[1]
|
||||
elif node[0] == SEQUENCE:
|
||||
r = ""
|
||||
for x in node[1]:
|
||||
r += asn1_build(x)
|
||||
return chr(SEQUENCE) + asn1_length(len(r)) + r
|
||||
else:
|
||||
raise ASN1FormatError("Unexpected tag in template: %02x" % node[0])
|
||||
+221
@@ -0,0 +1,221 @@
|
||||
# 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__ = [
|
||||
'DigestTooLargeError',
|
||||
'parse_private_key',
|
||||
'parse_public_key',
|
||||
'RSASSA_PKCS1_v1_5_sign',
|
||||
'RSASSA_PKCS1_v1_5_verify',
|
||||
'UnparsableKeyError',
|
||||
]
|
||||
|
||||
from dkim.asn1 import (
|
||||
ASN1FormatError,
|
||||
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,),
|
||||
])
|
||||
]
|
||||
|
||||
|
||||
class DigestTooLargeError(Exception):
|
||||
"""The digest is too large to fit within the requested length."""
|
||||
pass
|
||||
|
||||
|
||||
class UnparsableKeyError(Exception):
|
||||
"""The data could not be parsed as a key."""
|
||||
pass
|
||||
|
||||
|
||||
def parse_public_key(data):
|
||||
"""Parse an RSA public key.
|
||||
|
||||
@param data: DER-encoded X.509 subjectPublicKeyInfo
|
||||
containing an RFC3447 RSAPublicKey.
|
||||
@return: RSA public key
|
||||
"""
|
||||
try:
|
||||
# Not sure why the [1:] is necessary to skip a byte.
|
||||
x = asn1_parse(ASN1_Object, data)
|
||||
pkd = asn1_parse(ASN1_RSAPublicKey, x[0][1][1:])
|
||||
except ASN1FormatError, e:
|
||||
raise UnparsableKeyError(str(e))
|
||||
pk = {
|
||||
'modulus': pkd[0][0],
|
||||
'publicExponent': pkd[0][1],
|
||||
}
|
||||
return pk
|
||||
|
||||
|
||||
def parse_private_key(data):
|
||||
"""Parse an RSA private key.
|
||||
|
||||
@param data: DER-encoded RFC3447 RSAPrivateKey.
|
||||
@return: RSA private key
|
||||
"""
|
||||
try:
|
||||
pka = asn1_parse(ASN1_RSAPrivateKey, data)
|
||||
except ASN1FormatError, e:
|
||||
raise UnparsableKeyError(str(e))
|
||||
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, mlen, hashid):
|
||||
"""Encode a digest with RFC3447 EMSA-PKCS1-v1_5.
|
||||
|
||||
@param digest: digest byte string to encode
|
||||
@param mlen: desired message length
|
||||
@param hashid: ID of the hash used to generate the digest
|
||||
@return: encoded digest byte string
|
||||
"""
|
||||
dinfo = asn1_build(
|
||||
(SEQUENCE, [
|
||||
(SEQUENCE, [
|
||||
(OBJECT_IDENTIFIER, hashid),
|
||||
(NULL, None),
|
||||
]),
|
||||
(OCTET_STRING, digest),
|
||||
]))
|
||||
if len(dinfo)+3 > mlen:
|
||||
raise DigestTooLargeError()
|
||||
return "\x00\x01"+"\xff"*(mlen-len(dinfo)-3)+"\x00"+dinfo
|
||||
|
||||
|
||||
def str2int(s):
|
||||
"""Convert a byte string to an integer.
|
||||
|
||||
@param s: byte string representing a positive integer to convert
|
||||
@return: converted integer
|
||||
"""
|
||||
r = 0
|
||||
for c in s:
|
||||
r = (r << 8) | ord(c)
|
||||
return r
|
||||
|
||||
|
||||
def int2str(n, length=-1):
|
||||
"""Convert an integer to a byte string.
|
||||
|
||||
@param n: positive integer to convert
|
||||
@param length: minimum length
|
||||
@return: converted bytestring, of at least the minimum length if it was
|
||||
specified
|
||||
"""
|
||||
assert n >= 0
|
||||
r = []
|
||||
while length < 0 or len(r) < length:
|
||||
r.append(chr(n & 0xff))
|
||||
n >>= 8
|
||||
if length < 0 and n == 0:
|
||||
break
|
||||
r.reverse()
|
||||
assert length < 0 or len(r) == length
|
||||
return ''.join(r)
|
||||
|
||||
|
||||
def perform_rsa(message, exponent, modulus, mlen):
|
||||
"""Perform RSA signing or verification.
|
||||
|
||||
@param message: byte string to operate on
|
||||
@param exponent: public or private key exponent
|
||||
@param modulus: key modulus
|
||||
@param mlen: desired output length
|
||||
@return: byte string result of the operation
|
||||
"""
|
||||
return int2str(pow(str2int(message), exponent, modulus), mlen)
|
||||
|
||||
|
||||
def RSASSA_PKCS1_v1_5_sign(digest, hashid, private_exponent, modulus):
|
||||
"""Sign a digest with RFC3447 RSASSA-PKCS1-v1_5.
|
||||
|
||||
@param digest: digest byte string to sign
|
||||
@param hashid: ID of the hash used to generate the digest
|
||||
@param private_exponent: private key exponent
|
||||
@param modulus: key modulus
|
||||
@return: signed digest byte string
|
||||
"""
|
||||
modlen = len(int2str(modulus))
|
||||
encoded_digest = EMSA_PKCS1_v1_5_encode(digest, modlen, hashid)
|
||||
return perform_rsa(encoded_digest, private_exponent, modulus, modlen)
|
||||
|
||||
|
||||
def RSASSA_PKCS1_v1_5_verify(digest, hashid, signature, public_exponent,
|
||||
modulus):
|
||||
"""Verify a digest signed with RFC3447 RSASSA-PKCS1-v1_5.
|
||||
|
||||
@param digest: digest byte string to check
|
||||
@param hashid: ID of the hash used to generate the digest
|
||||
@param signature: signed digest byte string
|
||||
@param public_exponent: public key exponent
|
||||
@param modulus: key modulus
|
||||
@return: True if the signature is valid, False otherwise
|
||||
"""
|
||||
modlen = len(int2str(modulus))
|
||||
encoded_digest = EMSA_PKCS1_v1_5_encode(digest, modlen, hashid)
|
||||
signed_digest = perform_rsa(signature, public_exponent, modulus, modlen)
|
||||
return encoded_digest == signed_digest
|
||||
Reference in New Issue
Block a user