def consume(self, tag, message, region):
# Get values
version, signature_type, public_key_algorithm, hash_algorithm, hashed_subpacket_length = region.readlist(
"""
uint:8, uint:8, uint:8, uint:8, uint:16"""
)
# Complain if any values haven't been implemented yet
self.only_implemented(version, (4,), "version four signature packets")
self.only_implemented(signature_type, (0x13, 0x18), "UserId and Subkey binding signatures")
# Get key algorithm
algorithm = Mapped.algorithms.keys[public_key_algorithm]
# Get hasher
hasher = Mapped.algorithms.hashes[hash_algorithm]
# Determine hashed data
subsignature = region.read(hashed_subpacket_length * 8)
hashed_subpacket_data = message.consume_subsignature(subsignature)
# Not cyrptographically protected by signature
# Should only contain advisory information
unhashed_subpacket_length = region.read("uint:16")
unhashed_subpacket_body = region.read(unhashed_subpacket_length * 8)
unhashed_subpacket_data = message.consume_subsignature(unhashed_subpacket_body)
# Left 16 bits of the signed hash value provided for a heuristic test for valid signatures
left_of_signed_hash = region.read(8 * 2)
# Get the mpi value for the RSA hash
# RSA signature value m**d mod n
mdn = Mpi.parse(region).read("uint")
def consume_rest(self, tag, message, region, info):
"""Already have public key things"""
s2k_type = region.read("uint:8")
mpis = self.get_mpis(s2k_type, message, region, info)
# Get the rest of the mpi values and combine with those from public portion
mpi_values = Mpi.consume_private(mpis, info["algorithm"])
mpi_tuple = info["mpi_values"] + mpi_values
# Record key and key_id
info["key"] = info["algorithm"].construct(list(long(i.read("uint")) for i in mpi_tuple))
info["key_id"] = self.determine_key_id(info)
def get_mpi_values(self, region, algorithm):
"""
* Determine position before
* Get individual mpi values
* Determine how much was read
* Reset region to what it was before
* Return byte stream for the amount read in the first pass
"""
pos_before = region.pos
mpi_values = Mpi.consume_public(region, algorithm)
pos_after = region.pos
region.pos = pos_before
mpi_length = (pos_after - pos_before) / 8
raw_mpi_bytes = region.read("bytes:%d" % mpi_length)
return mpi_values, raw_mpi_bytes
