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# Copyright (c) 2018 Yubico AB
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or
# without modification, are permitted provided that the following
# conditions are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following
# disclaimer in the documentation and/or other materials provided
# with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
"""
Connects to the first FIDO device found which supports the HmacSecret extension,
creates a new credential for it with the extension enabled, and uses it to
derive two separate secrets.
NOTE: This extension is not enabled by default as direct access to the extension
is now allowed in a browser setting. See also prf.py for an example which uses
the PRF extension which is enabled by default.
"""
from fido2.hid import CtapHidDevice
from fido2.server import Fido2Server
from fido2.client import Fido2Client, WindowsClient
from fido2.ctap2.extensions import HmacSecretExtension
from exampleutils import CliInteraction
import ctypes
import sys
import os
try:
from fido2.pcsc import CtapPcscDevice
except ImportError:
CtapPcscDevice = None
def enumerate_devices():
for dev in CtapHidDevice.list_devices():
yield dev
if CtapPcscDevice:
for dev in CtapPcscDevice.list_devices():
yield dev
uv = "discouraged"
if WindowsClient.is_available() and not ctypes.windll.shell32.IsUserAnAdmin():
# Use the Windows WebAuthn API if available, and we're not running as admin
# By default only the PRF extension is allowed, we need to explicitly
# configure the client to allow hmac-secret
client = WindowsClient("https://example.com", allow_hmac_secret=True)
else:
# Locate a device
for dev in enumerate_devices():
client = Fido2Client(
dev,
"https://example.com",
user_interaction=CliInteraction(),
# By default only the PRF extension is allowed, we need to explicitly
# configure the client to allow hmac-secret
extensions=[HmacSecretExtension(allow_hmac_secret=True)],
)
if "hmac-secret" in client.info.extensions:
break
else:
print("No Authenticator with the HmacSecret extension found!")
sys.exit(1)
server = Fido2Server({"id": "example.com", "name": "Example RP"}, attestation="none")
user = {"id": b"user_id", "name": "A. User"}
# Prepare parameters for makeCredential
create_options, state = server.register_begin(
user,
resident_key_requirement="discouraged",
user_verification=uv,
authenticator_attachment="cross-platform",
)
# Create a credential
result = client.make_credential(
{
**create_options["publicKey"],
"extensions": {"hmacCreateSecret": True},
}
)
# Complete registration
auth_data = server.register_complete(
state, result.client_data, result.attestation_object
)
credentials = [auth_data.credential_data]
# HmacSecret result:
if not result.extension_results.get("hmacCreateSecret"):
print("Failed to create credential with HmacSecret")
sys.exit(1)
credential = result.attestation_object.auth_data.credential_data
print("New credential created, with the HmacSecret extension.")
# Prepare parameters for getAssertion
allow_list = [{"type": "public-key", "id": credential.credential_id}]
# Generate a salt for HmacSecret:
salt = os.urandom(32)
print("Authenticate with salt:", salt.hex())
# Prepare parameters for getAssertion
request_options, state = server.authenticate_begin(credentials, user_verification=uv)
# Authenticate the credential
result = client.get_assertion(
{
**request_options["publicKey"],
"extensions": {"hmacGetSecret": {"salt1": salt}},
}
)
# Only one cred in allowCredentials, only one response.
result = result.get_response(0)
output1 = result.extension_results.hmac_get_secret.output1
print("Authenticated, secret:", output1.hex())
# Authenticate again, using two salts to generate two secrets:
# Generate a second salt for HmacSecret:
salt2 = os.urandom(32)
print("Authenticate with second salt:", salt2.hex())
# The first salt is reused, which should result in the same secret.
result = client.get_assertion(
{
**request_options["publicKey"],
"extensions": {"hmacGetSecret": {"salt1": salt, "salt2": salt2}},
}
)
# Only one cred in allowCredentials, only one response.
result = result.get_response(0)
output = result.extension_results.hmac_get_secret
print("Old secret:", output.output1.hex())
print("New secret:", output.output2.hex())
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