def encode(m, embits, hash_class=hashlib.sha1,
mgf=mgf.mgf1, salt=None, s_len=None, random=random.SystemRandom):
m_hash = hash_class(m).digest()
h_len = len(m_hash)
if salt is not None:
s_len = len(salt)
else:
if s_len is None:
s_len = h_len
salt = primitives.i2osp(random().getrandbits(s_len*8), s_len)
em_len = primitives.integer_ceil(embits, 8)
if em_len < len(m_hash) + s_len + 2:
raise exceptions.EncodingError
m_prime = ('\x00' * 8) + m_hash + salt
h = hash_class(m_prime).digest()
ps = '\x00' * (em_len - s_len - h_len - 2)
db = ps + '\x01' + salt
db_mask = mgf(h, em_len - h_len - 1)
masked_db = primitives.string_xor(db, db_mask)
octets, bits = (8 * em_len - embits) / 8, (8*em_len-embits) % 8
# replace first `octets' bytes
masked_db = ('\x00' * octets) + masked_db[octets:]
new_byte = chr(ord(masked_db[octets]) & (255 >> bits))
masked_db = masked_db[:octets] + new_byte + masked_db[octets+1:]
return masked_db + h + '\xbc'
def verify(public_key,
message,
signature,
emsa_pss_verify=emsa_pss.verify,
hash_class=hashlib.sha1,
mgf1=mgf.mgf1):
'''Verify the signature of message signed using private_key and the
PKCS#1 2.0 RSASSA-PSS algorithm.
private_key - the private key to use
message - the signed byte string
signature - the byte string of the signature of the message
emsa_pss_verify - the verify function for the used encoding,
default to EMSA-PSS verification function
hash_class - the hash algorithme to use, default to SHA-1 from the
Python hashlib package.
mgf1 - the mask generating function to use, default to MGF1
'''
mod_bits = public_key.bit_size
s = primitives.os2ip(signature)
m = public_key.rsavp1(s)
embits = mod_bits - 1
em_len = primitives.integer_ceil(embits, 8)
em = primitives.i2osp(m, em_len)
return emsa_pss_verify(message,
em,
embits,
hash_class=hash_class,
mgf=mgf1)
def verify(public_key, message, signature,
emsa_pss_verify=emsa_pss.verify):
mod_bits = public_key.bit_size
s = primitives.os2ip(signature)
m = public_key.rsavp1(s)
embits = mod_bits - 1
em_len = primitives.integer_ceil(embits, 8)
em = primitives.i2osp(m, em_len)
return emsa_pss_verify(message, em, embits)
def verify(m, em, embits, hash_class=hashlib.sha1, mgf=mgf.mgf1, s_len=None):
'''
Verify that a message padded using the PKCS#1 v2 PSS algorithm matched a
given message string.
m - the message to match
em - the padded message
embits - the length in bits of the padded message
hash_class - the hash algorithm used to compute the digest of the message
mgf - the mask generation function
s_len - the length of the salt string, if None the length of the digest is used.
Return: True if the message matches, False otherwise.
'''
# 1. cannot verify, does not know the max input length of hash_class
# 2.
m_hash = hash_class(m).digest()
h_len = len(m_hash)
if s_len is None:
s_len = h_len
em_len = primitives.integer_ceil(embits, 8)
# 3.
if em_len < len(m_hash) + s_len + 2:
return False
# 4.
if em[-1] != '\xbc':
return False
# 5.
masked_db, h = em[:em_len-h_len-1], em[em_len-h_len-1:-1]
# 6.
octets, bits = (8 * em_len - embits) / 8, (8*em_len-embits) % 8
zero = masked_db[:octets] + chr(ord(masked_db[octets]) & ~(255 >>bits))
for c in zero:
if c != '\x00':
return False
# 7.
db_mask = mgf(h, em_len - h_len - 1, hash_class=hash_class)
# 8.
db = primitives.string_xor(masked_db, db_mask)
# 9.
new_byte = chr(ord(db[octets]) & (255 >> bits))
db = ('\x00' * octets) + new_byte + db[octets+1:]
# 10.
for c in db[:em_len-h_len-s_len-2]:
if c != '\x00':
return False
if db[em_len-h_len-s_len-2] != '\x01':
return False
# 11.
salt = db[-s_len:]
# 12.
m_prime = ('\x00' * 8) + m_hash + salt
# 13.
h_prime = hash_class(m_prime).digest()
# 14.
return primitives.constant_time_cmp(h_prime, h)
def verify(m, em, embits, hash_class=hashlib.sha1, mgf=mgf.mgf1, s_len=None):
'''
Verify that a message padded using the PKCS#1 v2 PSS algorithm matched a
given message string.
m - the message to match
em - the padded message
embits - the length in bits of the padded message
hash_class - the hash algorithm used to compute the digest of the message
mgf - the mask generation function
s_len - the length of the salt string, if None the length of the digest is used.
Return: True if the message matches, False otherwise.
'''
# 1. cannot verify, does not know the max input length of hash_class
# 2.
m_hash = hash_class(m).digest()
h_len = len(m_hash)
if s_len is None:
s_len = h_len
em_len = primitives.integer_ceil(embits, 8)
# 3.
if em_len < len(m_hash) + s_len + 2:
return False
# 4.
if em[-1] != '\xbc':
return False
# 5.
masked_db, h = em[:em_len - h_len - 1], em[em_len - h_len - 1:-1]
# 6.
octets, bits = (8 * em_len - embits) / 8, (8 * em_len - embits) % 8
zero = masked_db[:octets] + chr(ord(masked_db[octets]) & ~(255 >> bits))
for c in zero:
if c != '\x00':
return False
# 7.
db_mask = mgf(h, em_len - h_len - 1)
# 8.
db = primitives.string_xor(masked_db, db_mask)
# 9.
new_byte = chr(ord(db[octets]) & (255 >> bits))
db = ('\x00' * octets) + new_byte + db[octets + 1:]
# 10.
for c in db[:em_len - h_len - s_len - 2]:
if c != '\x00':
return False
if db[em_len - h_len - s_len - 2] != '\x01':
return False
# 11.
salt = db[-s_len:]
# 12.
m_prime = ('\x00' * 8) + m_hash + salt
# 13.
h_prime = hash_class(m_prime).digest()
# 14.
return primitives.constant_time_cmp(h_prime, h)
def mgf1(mgf_seed, mask_len, hash_class=hashlib.sha1):
'''Mask Generation Function v1'''
h_len = hash_class().digest_size
if mask_len > 0x10000:
raise ValueError('mask too long')
T = ''
for i in xrange(0, integer_ceil(mask_len, h_len)):
C = i2osp(i, 4)
T = T + hash_class(mgf_seed + C).digest()
return T[:mask_len]
def encode(m,
embits,
hash_class=hashlib.sha1,
mgf=mgf.mgf1,
salt=None,
s_len=None,
rnd=default_crypto_random):
'''Encode a message using the PKCS v2 PSS padding.
m - the message to encode
embits - the length of the padded message
mgf - a masg generating function, default is mgf1 the mask generating
function proposed in the PKCS#1 v2 standard.
hash_class - the hash algorithm to use to compute the digest of the
message, must conform to the hashlib class interface.
salt - a fixed salt string to use, if None, a random string of length
s_len is used instead, necessary for tests,
s_len - the length of the salt string when using a random generator to
create it, if None the length of the digest is used.
rnd - the random generator used to compute the salt string
Return value: the padded message
'''
m_hash = hash_class(m).digest()
h_len = len(m_hash)
if salt is not None:
s_len = len(salt)
else:
if s_len is None:
s_len = h_len
salt = primitives.i2osp(rnd.getrandbits(s_len * 8), s_len)
em_len = primitives.integer_ceil(embits, 8)
if em_len < len(m_hash) + s_len + 2:
raise exceptions.EncodingError
m_prime = ('\x00' * 8) + m_hash + salt
h = hash_class(m_prime).digest()
ps = '\x00' * (em_len - s_len - h_len - 2)
db = ps + '\x01' + salt
db_mask = mgf(h, em_len - h_len - 1)
masked_db = primitives.string_xor(db, db_mask)
octets, bits = (8 * em_len - embits) / 8, (8 * em_len - embits) % 8
# replace first `octets' bytes
masked_db = ('\x00' * octets) + masked_db[octets:]
new_byte = chr(ord(masked_db[octets]) & (255 >> bits))
masked_db = masked_db[:octets] + new_byte + masked_db[octets + 1:]
return masked_db + h + '\xbc'
def mgf1(mgf_seed, mask_len, hash_class=hashlib.sha1):
'''
Mask Generation Function v1 from the PKCS#1 v2.0 standard.
mgs_seed - the seed, a byte string
mask_len - the length of the mask to generate
hash_class - the digest algorithm to use, default is SHA1
Return value: a pseudo-random mask, as a byte string
'''
h_len = hash_class().digest_size
if mask_len > 0x10000:
raise ValueError('mask too long')
T = ''
for i in xrange(0, integer_ceil(mask_len, h_len)):
C = i2osp(i, 4)
T = T + hash_class(mgf_seed + C).digest()
return T[:mask_len]
def mgf1(mgf_seed, mask_len, hash_class=hashlib.sha1):
'''
Mask Generation Function v1 from the PKCS#1 v2.0 standard.
mgs_seed - the seed, a byte string
mask_len - the length of the mask to generate
hash_class - the digest algorithm to use, default is SHA1
Return value: a pseudo-random mask, as a byte string
'''
h_len = hash_class().digest_size
if mask_len > 0x10000:
raise ValueError('mask too long')
T = ''
for i in xrange(0, integer_ceil(mask_len, h_len)):
C = i2osp(i, 4)
T = T + hash_class(mgf_seed + C).digest()
return T[:mask_len]
def verify(m, em, embits, hash_class=hashlib.sha1, mgf=mgf.mgf1, s_len=None):
# 1. cannot verify, does not know the max input length of hash_class
# 2.
m_hash = hash_class(m).digest()
h_len = len(m_hash)
if s_len is None:
s_len = h_len
em_len = primitives.integer_ceil(embits, 8)
# 3.
if em_len < len(m_hash) + s_len + 2:
return False
# 4.
if em[-1] != '\xbc':
return False
# 5.
masked_db, h = em[:em_len-h_len-1], em[em_len-h_len-1:-1]
# 6.
octets, bits = (8 * em_len - embits) / 8, (8*em_len-embits) % 8
zero = masked_db[:octets] + chr(ord(masked_db[octets]) & ~(255 >>bits))
for c in zero:
if c != '\x00':
return False
# 7.
db_mask = mgf(h, em_len - h_len - 1)
# 8.
db = primitives.string_xor(masked_db, db_mask)
# 9.
new_byte = chr(ord(db[octets]) & (255 >> bits))
db = ('\x00' * octets) + new_byte + db[octets+1:]
# 10.
for c in db[:em_len-h_len-s_len-2]:
if c != '\x00':
return False
if db[em_len-h_len-s_len-2] != '\x01':
return False
# 11.
salt = db[-s_len:]
# 12.
m_prime = ('\x00' * 8) + m_hash + salt
# 13.
h_prime = hash_class(m_prime).digest()
# 14.
return primitives.constant_time_cmp(h_prime, h)
def encode(m, embits, hash_class=hashlib.sha1,
mgf=mgf.mgf1, salt=None, s_len=None, rnd=default_crypto_random):
'''Encode a message using the PKCS v2 PSS padding.
m - the message to encode
embits - the length of the padded message
mgf - a masg generating function, default is mgf1 the mask generating
function proposed in the PKCS#1 v2 standard.
hash_class - the hash algorithm to use to compute the digest of the
message, must conform to the hashlib class interface.
salt - a fixed salt string to use, if None, a random string of length
s_len is used instead, necessary for tests,
s_len - the length of the salt string when using a random generator to
create it, if None the length of the digest is used.
rnd - the random generator used to compute the salt string
Return value: the padded message
'''
m_hash = hash_class(m).digest()
h_len = len(m_hash)
if salt is not None:
s_len = len(salt)
else:
if s_len is None:
s_len = h_len
salt = primitives.i2osp(rnd.getrandbits(s_len*8), s_len)
em_len = primitives.integer_ceil(embits, 8)
if em_len < len(m_hash) + s_len + 2:
raise exceptions.EncodingError
m_prime = ('\x00' * 8) + m_hash + salt
h = hash_class(m_prime).digest()
ps = '\x00' * (em_len - s_len - h_len - 2)
db = ps + '\x01' + salt
db_mask = mgf(h, em_len - h_len - 1, hash_class=hash_class)
masked_db = primitives.string_xor(db, db_mask)
octets, bits = (8 * em_len - embits) / 8, (8*em_len-embits) % 8
# replace first `octets' bytes
masked_db = ('\x00' * octets) + masked_db[octets:]
new_byte = chr(ord(masked_db[octets]) & (255 >> bits))
masked_db = masked_db[:octets] + new_byte + masked_db[octets+1:]
return masked_db + h + '\xbc'
def verify(public_key, message, signature,
emsa_pss_verify=emsa_pss.verify,
hash_class=hashlib.sha1,
mgf1=mgf.mgf1):
'''Verify the signature of message signed using private_key and the
PKCS#1 2.0 RSASSA-PSS algorithm.
private_key - the private key to use
message - the signed byte string
signature - the byte string of the signature of the message
emsa_pss_verify - the verify function for the used encoding,
default to EMSA-PSS verification function
hash_class - the hash algorithme to use, default to SHA-1 from the
Python hashlib package.
mgf1 - the mask generating function to use, default to MGF1
'''
mod_bits = public_key.bit_size
s = primitives.os2ip(signature)
m = public_key.rsavp1(s)
embits = mod_bits - 1
em_len = primitives.integer_ceil(embits, 8)
em = primitives.i2osp(m, em_len)
return emsa_pss_verify(message, em, embits, hash_class=hash_class,
mgf=mgf1)
