The `fido2` Python library provides comprehensive tools for implementing both client-side and server-side FIDO2/WebAuthn functionality. Currently at version 2.1.1, it maintains an active development pace with feature releases every few months and major versions approximately annually, ensuring compliance with the latest WebAuthn specifications (Level 3 working draft) and CTAP protocols.
Install & Compatibility
Where this runs
tested against v2.2.0 · pip install
no network on importno background threads
Install × environment matrix
Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux
muslpy 3.10–3.920 runs
installs and imports cleanly · install 0.0s · import 0.132s · 35.6MB
glibcpy 3.10–3.920 runs
installs and imports cleanly · install 2.4s · import 0.115s · 36MB
33MB installed
● package 33MB
Code
Verified usage
Verified import paths — ran on the pinned version, not inferred.
from fido2.webauthn import AttestationObject
from fido2.webauthn import CollectedClientData
The primary verification functions are now top-level in `fido2.webauthn` for clarity.
from fido2.webauthn import verify_registration_response
from fido2.client import Fido2Client
This quickstart demonstrates how to verify a FIDO2 WebAuthn registration response on the server-side. It simulates receiving `clientDataJSON` and `attestationObject` from a browser and uses `fido2.webauthn.verify_registration_response` to validate them against server-generated challenge and Relying Party (RP) configuration. The example uses minimal mock data for demonstration purposes.
import os
import json
import base64
from fido2.webauthn import (
AttestationObject,
CollectedClientData,
verify_registration_response,
)
from fido2 import cbor
# --- Server-side configuration and stored data ---
# In a real application, these would be generated and stored securely.
RP_ID = os.environ.get("FIDO2_RP_ID", "example.com")
RP_ORIGIN = f"https://{RP_ID}"
# A challenge issued previously by the server to the client for this registration attempt
# This must be a cryptographically secure random 32-byte value.
CHALLENGE = base64.urlsafe_b64decode(b"uKz0s4zP6T3o-J2V-5rX_s_L4l6m-c7C8j9k0l1m2n3o4p5q6r7s8t9u0v1w2x3y=") # Example base64url-encoded bytes for a 32-byte challenge
USER_ID = b"some_unique_user_id_bytes" # The user ID for whom registration was requested
EXPECTED_RP_ID = RP_ID
EXPECTED_ORIGINS = {RP_ORIGIN}
# --- Simulate client-provided data (in a real app, these come from the browser) ---
# Example: clientDataJSON received from the browser as a string
client_data_json_str = f'''
{{
"type": "webauthn.create",
"challenge": "{base64.urlsafe_b64encode(CHALLENGE).rstrip(b'=').decode('utf-8')}",
"origin": "{RP_ORIGIN}",
"crossOrigin": false
}}
'''
# Example: AttestationObject received from the browser as base64url-encoded CBOR bytes
# This is a minimal 'none' attestation for demonstration purposes.
# Real attestations are more complex.
attestation_object_b64url = "o2NmbXRoZJpvbmVhdHRTdG10oGhhdXRoRGF0YVjLp_hNq_D0D8x4jL17w2-5rX_s_L4l6m-c7C8j9k0l1m2n3o4p5q6r7s8t9u0v1w2x3yFkQAAAAAAAAAAAAAAAAAAAAAAwIAIAxM0k3Kz-k_D0x4jL17w2-5rX_s_L4l6m-c7C8j9k0l1m2n3o4p5q6r7s8t9u0v1w2x3yBoAAAAAAAAAAAAAAAAAAAAAADAAAAAQAg"
# --- Server-side verification using fido2 library ---
try:
# Parse the client data and attestation object
client_data = CollectedClientData(json.loads(client_data_json_str))
attestation_object = AttestationObject(base64.urlsafe_b64decode(attestation_object_b64url + "==")) # Add padding back for base64
# Verify the registration response
auth_data = verify_registration_response(
client_data=client_data,
attestation_object=attestation_object,
challenge=CHALLENGE,
rp_id=EXPECTED_RP_ID,
origins=EXPECTED_ORIGINS,
user_id=USER_ID
# In production, you would pass `trusted_attestation_public_keys`
# or `attestation_callback` to validate attestation certificates.
)
print("Registration successful!")
print(f"Credential ID: {base64.urlsafe_b64encode(auth_data.credential_id).decode('utf-8')}")
print(f"Public Key: {base64.urlsafe_b64encode(auth_data.credential_public_key).decode('utf-8')}")
print(f"Signature Count: {auth_data.sign_count}")
# In a real application, you would store auth_data.credential_id,
# auth_data.credential_public_key, and auth_data.sign_count
# associated with the user for future authentication.
except Exception as e:
print(f"Registration failed: {e}")
fido2 --version
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Version history
Breaking-change detection hasn't run for this library yet.
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Security & dependencies
CVE tracking and dependency tree are planned for a later release.