diff options
Diffstat (limited to 'python/olm/pk.py')
| -rw-r--r-- | python/olm/pk.py | 112 |
1 files changed, 110 insertions, 2 deletions
diff --git a/python/olm/pk.py b/python/olm/pk.py index b67d5a4..193aba5 100644 --- a/python/olm/pk.py +++ b/python/olm/pk.py @@ -17,7 +17,8 @@ This module contains bindings to the PK part of the Olm library. It contains two classes PkDecryption and PkEncryption that are used to -establish an encrypted communication channel using public key encryption. +establish an encrypted communication channel using public key encryption, +as well as a class PkSigning that is used to sign a message. Examples: >>> decryption = PkDecryption() @@ -25,16 +26,22 @@ Examples: >>> plaintext = "It's a secret to everybody." >>> message = encryption.encrypt(plaintext) >>> decrypted_plaintext = decryption.decrypt(message) + >>> seed = PkSigning.generate_seed() + >>> signing = PkSigning(seed) + >>> signature = signing.sign(plaintext) + >>> ed25519_verify(signing.public_key, plaintext, signature) """ from builtins import super from typing import AnyStr, Type + from future.utils import bytes_to_native_str from _libolm import ffi, lib # type: ignore -from ._finalize import track_for_finalization + from ._compat import URANDOM, to_bytearray +from ._finalize import track_for_finalization class PkEncryptionError(Exception): @@ -45,6 +52,10 @@ class PkDecryptionError(Exception): """libolm Pk decryption exception.""" +class PkSigningError(Exception): + """libolm Pk signing exception.""" + + def _clear_pk_encryption(pk_struct): lib.olm_clear_pk_encryption(pk_struct) @@ -344,3 +355,100 @@ class PkDecryption(object): lib.memset(plaintext_buffer, 0, max_plaintext_length) return bytes_to_native_str(plaintext) + + +def _clear_pk_signing(pk_struct): + lib.olm_clear_pk_signing(pk_struct) + + +class PkSigning(object): + """PkSigning class. + + Signs messages using public key cryptography. + + Attributes: + public_key (str): The public key of the PkSigning object, can be + shared and used to verify using Utility.ed25519_verify. + + """ + + def __init__(self, seed): + # type: (bytes) -> None + """Create a new signing object. + + Args: + seed(bytes): the seed to use as the private key for signing. The + seed must have the same length as the seeds generated by + PkSigning.generate_seed(). + """ + if not seed: + raise ValueError("seed can't be empty") + + self._buf = ffi.new("char[]", lib.olm_pk_signing_size()) + self._pk_signing = lib.olm_pk_signing(self._buf) + track_for_finalization(self, self._pk_signing, _clear_pk_signing) + + seed_buffer = ffi.new("char[]", seed) + + pubkey_length = lib.olm_pk_signing_public_key_length() + pubkey_buffer = ffi.new("char[]", pubkey_length) + + ret = lib.olm_pk_signing_key_from_seed( + self._pk_signing, + pubkey_buffer, pubkey_length, + seed_buffer, len(seed) + ) + + # zero out copies of the seed + lib.memset(seed_buffer, 0, len(seed)) + + self._check_error(ret) + + self.public_key = bytes_to_native_str( + ffi.unpack(pubkey_buffer, pubkey_length) + ) + + def _check_error(self, ret): + # type: (int) -> None + if ret != lib.olm_error(): + return + + last_error = bytes_to_native_str( + ffi.string(lib.olm_pk_signing_last_error(self._pk_signing))) + + raise PkSigningError(last_error) + + @classmethod + def generate_seed(cls): + # type: () -> bytes + """Generate a random seed. + """ + random_length = lib.olm_pk_signing_seed_length() + random = URANDOM(random_length) + + return random + + def sign(self, message): + # type: (AnyStr) -> str + """Sign a message + + Returns the signature. + Raises PkSigningError on failure. + + Args: + message(str): the message to sign. + """ + bytes_message = to_bytearray(message) + + signature_length = lib.olm_pk_signature_length() + signature_buffer = ffi.new("char[]", signature_length) + + ret = lib.olm_pk_sign( + self._pk_signing, + ffi.from_buffer(bytes_message), len(bytes_message), + signature_buffer, signature_length) + self._check_error(ret) + + return bytes_to_native_str( + ffi.unpack(signature_buffer, signature_length) + ) |