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import hashlib
from typing import Any, Optional
from . import utils
from .otp import OTP
class HOTP(OTP):
"""
Handler for HMAC-based OTP counters.
"""
def __init__(
self,
s: str,
digits: int = 6,
digest: Any = None,
name: Optional[str] = None,
issuer: Optional[str] = None,
initial_count: int = 0,
) -> None:
"""
:param s: secret in base32 format
:param initial_count: starting HMAC counter value, defaults to 0
:param digits: number of integers in the OTP. Some apps expect this to be 6 digits, others support more.
:param digest: digest function to use in the HMAC (expected to be SHA1)
:param name: account name
:param issuer: issuer
"""
if digest is None:
digest = hashlib.sha1
self.initial_count = initial_count
super().__init__(s=s, digits=digits, digest=digest, name=name, issuer=issuer)
def at(self, count: int) -> str:
"""
Generates the OTP for the given count.
:param count: the OTP HMAC counter
:returns: OTP
"""
return self.generate_otp(self.initial_count + count)
def verify(self, otp: str, counter: int) -> bool:
"""
Verifies the OTP passed in against the current counter OTP.
:param otp: the OTP to check against
:param counter: the OTP HMAC counter
"""
return utils.strings_equal(str(otp), str(self.at(counter)))
def provisioning_uri(
self,
name: Optional[str] = None,
initial_count: Optional[int] = None,
issuer_name: Optional[str] = None,
image: Optional[str] = None,
) -> str:
"""
Returns the provisioning URI for the OTP. This can then be
encoded in a QR Code and used to provision an OTP app like
Google Authenticator.
See also:
https://github.com/google/google-authenticator/wiki/Key-Uri-Format
:param name: name of the user account
:param initial_count: starting HMAC counter value, defaults to 0
:param issuer_name: the name of the OTP issuer; this will be the
organization title of the OTP entry in Authenticator
:returns: provisioning URI
"""
return utils.build_uri(
self.secret,
name=name if name else self.name,
initial_count=initial_count if initial_count else self.initial_count,
issuer=issuer_name if issuer_name else self.issuer,
algorithm=self.digest().name,
digits=self.digits,
image=image,
)