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client.py
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client.py
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import secrets
from datetime import date
from typing import Dict, Optional, Tuple
from kvac.verifiable_encryption import Ciphertext, KeyCommitment
from zkgroup.auth_credential import AuthCredential
from zkgroup.client.client_group import ClientGroup
from zkgroup.constants import Role, GMK_LENGTH, PK_LENGTH
from zkgroup.profile_key_credential import ProfileKeyCredential, \
calc_profile_key_version, calc_profile_key_commitment
from zkgroup.server.server import Server
class Client:
"""Client for ZKGroups. It can have multiple groups (with secret information for each),
a ProfileKey, one Auth- and various ProfileKeyCredentials."""
def __init__(self, uid: bytes):
if len(uid) != 16:
raise ValueError("UID must be 16 bytes long.")
self.uid: bytes = uid
self.auth_credential: Optional[AuthCredential] = None
self.profile_key: Optional[bytes] = None
# use corresponding UIDs as keys
self.profile_key_credentials: Dict[bytes, ProfileKeyCredential] = {}
# use numeric IDs for user-friendliness
self.groups: Dict[int, ClientGroup] = {}
# Operations for Credentials
def fetch_auth_credential(self, redemption_date: date):
"""The Client gets a new AuthCredential from the Server."""
# assumes an authenticated channel
auth_credential = AuthCredential(Server().auth_public_key, self.uid, redemption_date)
request, _ = auth_credential.request()
response = Server().get_auth_credential(request, redemption_date)
auth_credential.activate(response)
self.auth_credential = auth_credential
def generate_new_profile_key(self):
"""The Client generates a new ProfileKey and sends the commitment to the server."""
# assumes an authenticated channel
profile_key = secrets.token_bytes(PK_LENGTH)
Server().commit_to_profile_key(
self.uid,
calc_profile_key_version(profile_key),
calc_profile_key_commitment(Server().profile_key_public_key, self.uid, profile_key))
self.profile_key = profile_key
def fetch_profile_key_credential(self, target_uid: bytes, profile_key: bytes):
version = calc_profile_key_version(profile_key)
profile_key_credential = ProfileKeyCredential(
Server().profile_key_public_key,
target_uid,
profile_key)
request, commitment = profile_key_credential.request()
response = Server().get_profile_key_credential(
request,
target_uid,
version,
commitment)
profile_key_credential.activate(response)
self.profile_key_credentials[target_uid] = profile_key_credential
# Operations for Group Management
def create_group(self) -> int:
"""The Client creates a new group and registers it with the Server.
Returns the internal ID of the new group."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
if self.profile_key is None:
raise ValueError("Client has no ProfileKey.")
new_group = ClientGroup(secrets.token_bytes(GMK_LENGTH))
Server().create_group(
(new_group.uid_pk, new_group.profile_key_pk),
new_group.encrypt_profile_key(self.profile_key, self.uid),
self.auth_credential.present([new_group.uid_key]),
self.profile_key_credentials[self.uid].present([new_group.uid_key, new_group.profile_key_key]),
self.auth_cred_redemption_date)
new_group_id = max(self.groups) + 1 if self.groups else 0
self.groups[new_group_id] = new_group
return new_group_id
def leave_group(self, group_id: int):
"""The Client leaves a group and deletes it."""
self.delete_group_member(group_id, self.uid)
del self.groups[group_id]
def delete_group_member(self, group_id: int, member_uid: bytes):
"""The Client deletes a member from a group. It should notify the removed member."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
group = self.groups[group_id]
Server().remove_member(
(group.uid_pk, group.profile_key_pk),
group.encrypt_uid(member_uid),
self.auth_credential.present([group.uid_key]),
self.auth_cred_redemption_date)
def notify_removed_from_group(self, group_pk: Tuple[KeyCommitment, KeyCommitment]):
"""The Client is notified that it was removed from a group."""
for group_id, group in self.groups.items():
if (group.uid_pk, group.profile_key_pk) == group_pk:
del self.groups[group_id]
break
def notify_added_to_group(self, gmk: bytes) -> int:
"""The Client is notified that it was added to a group."""
new_group_id = max(self.groups) + 1 if self.groups else 0
self.groups[new_group_id] = ClientGroup(gmk)
return new_group_id
def delete_group(self, group_id: int):
"""The Client deletes a group. It should notify all members first."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
group = self.groups[group_id]
Server().delete_group(
(group.uid_pk, group.profile_key_pk),
self.auth_credential.present([group.uid_key]),
self.auth_cred_redemption_date)
del self.groups[group_id]
def add_invited_group_member(self, group_id: int, new_member_uid: bytes, role: Role):
"""The Client adds a new invited member to a group (without ProfileKey)."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
group = self.groups[group_id]
Server().add_invited_group_member(
(group.uid_pk, group.profile_key_pk),
group.encrypt_uid(new_member_uid),
role,
self.auth_credential.present([group.uid_key]),
self.auth_cred_redemption_date)
def add_group_member(self, group_id: int, new_member_uid: bytes, new_member_pk: bytes, role: Role):
"""The Client adds a new member to a group."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
group = self.groups[group_id]
Server().add_group_member(
(group.uid_pk, group.profile_key_pk),
group.encrypt_uid(new_member_uid),
group.encrypt_profile_key(new_member_pk, new_member_uid),
role,
self.auth_credential.present([group.uid_key]),
self.profile_key_credentials[new_member_uid].present(
[group.uid_key, group.profile_key_key]),
self.auth_cred_redemption_date)
def receive_group_invitation(self, gmk: bytes) -> int:
"""The Client receives a group invitation."""
new_group_id = max(self.groups) + 1 if self.groups else 0
group = ClientGroup(gmk)
self.groups[new_group_id] = group
self.update_profile_key(new_group_id)
return new_group_id
def update_profile_key(self, group_id: int):
"""The Client updates its ProfileKey in a group."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
if self.profile_key is None:
raise ValueError("Client has no ProfileKey.")
group = self.groups[group_id]
Server().update_profile_key(
(group.uid_pk, group.profile_key_pk),
group.encrypt_profile_key(self.profile_key, self.uid),
self.auth_credential.present([group.uid_key]),
self.profile_key_credentials[self.uid].present([group.uid_key, group.profile_key_key]),
self.auth_cred_redemption_date)
def fetch_group_members(self, group_id: int) -> Dict[bytes, Tuple[Optional[bytes], Role]]:
"""The Client fetches the members of a group."""
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
group = self.groups[group_id]
encrypted_members = Server().fetch_group_members(
(group.uid_pk, group.profile_key_pk),
self.auth_credential.present([group.uid_key]),
self.auth_cred_redemption_date)
decrypted_members: Dict[bytes, Tuple[Optional[bytes], Role]] = {}
for member_uid, (member_pk, role) in encrypted_members.items():
decrypted_uid = group.decrypt_uid(Ciphertext.from_bytes(member_uid))
if member_pk is not None:
decrypted_pk = group.decrypt_profile_key(Ciphertext.from_bytes(member_pk), decrypted_uid)
decrypted_members[decrypted_uid] = (decrypted_pk, role)
else:
decrypted_members[decrypted_uid] = (None, role)
return decrypted_members
@property
def auth_cred_redemption_date(self) -> date:
if self.auth_credential is None:
raise ValueError("Client has no AuthCredential.")
return date.fromordinal(
int.from_bytes(bytes(self.auth_credential.redemption_date), byteorder="little"))