import unicodedata
from hmac import compare_digest
from typing import Dict, Optional, Union
from urllib.parse import quote, urlencode, urlparse
[docs]def build_uri(
secret: str,
name: str,
initial_count: Optional[int] = None,
issuer: Optional[str] = None,
algorithm: Optional[str] = None,
digits: Optional[int] = None,
period: Optional[int] = None,
image: Optional[str] = None,
) -> str:
"""
Returns the provisioning URI for the OTP; works for either TOTP or HOTP.
This can then be encoded in a QR Code and used to provision the Google
Authenticator app.
For module-internal use.
See also:
https://github.com/google/google-authenticator/wiki/Key-Uri-Format
:param secret: the hotp/totp secret used to generate the URI
:param name: name of the account
:param initial_count: starting counter value, defaults to None.
If none, the OTP type will be assumed as TOTP.
:param issuer: the name of the OTP issuer; this will be the
organization title of the OTP entry in Authenticator
:param algorithm: the algorithm used in the OTP generation.
:param digits: the length of the OTP generated code.
:param period: the number of seconds the OTP generator is set to
expire every code.
:param image: optional logo image url
:returns: provisioning uri
"""
# initial_count may be 0 as a valid param
is_initial_count_present = initial_count is not None
# Handling values different from defaults
is_algorithm_set = algorithm is not None and algorithm != "sha1"
is_digits_set = digits is not None and digits != 6
is_period_set = period is not None and period != 30
otp_type = "hotp" if is_initial_count_present else "totp"
base_uri = "otpauth://{0}/{1}?{2}"
url_args: Dict[str, Union[None, int, str]] = {"secret": secret}
label = quote(name)
if issuer is not None:
label = quote(issuer) + ":" + label
url_args["issuer"] = issuer
if is_initial_count_present:
url_args["counter"] = initial_count
if is_algorithm_set:
url_args["algorithm"] = algorithm.upper() # type: ignore
if is_digits_set:
url_args["digits"] = digits
if is_period_set:
url_args["period"] = period
if image:
image_uri = urlparse(image)
if image_uri.scheme != "https" or not image_uri.netloc or not image_uri.path:
raise ValueError("{} is not a valid url".format(image_uri))
url_args["image"] = image
uri = base_uri.format(otp_type, label, urlencode(url_args).replace("+", "%20"))
return uri
[docs]def strings_equal(s1: str, s2: str) -> bool:
"""
Timing-attack resistant string comparison.
Normal comparison using == will short-circuit on the first mismatching
character. This avoids that by scanning the whole string, though we
still reveal to a timing attack whether the strings are the same
length.
"""
s1 = unicodedata.normalize("NFKC", s1)
s2 = unicodedata.normalize("NFKC", s2)
return compare_digest(s1.encode("utf-8"), s2.encode("utf-8"))