File: test_challenge_auth.py

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# ------------------------------------
# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.
# ------------------------------------
"""
Tests for the HTTP challenge authentication implementation. These tests aren't parallelizable, because
the challenge cache is global to the process.
"""
import functools
import os
import time
from urllib.parse import urlparse
from uuid import uuid4

from devtools_testutils import recorded_by_proxy

try:
    from unittest.mock import Mock, patch
except ImportError:  # python < 3.3
    from mock import Mock, patch  # type: ignore

import pytest
from azure.core.credentials import AccessToken
from azure.core.exceptions import ServiceRequestError
from azure.core.pipeline import Pipeline
from azure.core.pipeline.policies import SansIOHTTPPolicy
from azure.core.pipeline.transport import HttpRequest
from azure.identity import ClientSecretCredential
from azure.keyvault.keys import KeyClient
from azure.keyvault.keys._shared import ChallengeAuthPolicy, HttpChallenge, HttpChallengeCache
from azure.keyvault.keys._shared.client_base import DEFAULT_VERSION

from _shared.helpers import Request, mock_response, validating_transport
from _shared.test_case import KeyVaultTestCase
from _test_case import KeysClientPreparer, get_decorator
from _keys_test_case import KeysTestCase

only_default_version = get_decorator(api_versions=[DEFAULT_VERSION])

class TestChallengeAuth(KeyVaultTestCase, KeysTestCase):
    @pytest.mark.parametrize("api_version,is_hsm", only_default_version)
    @KeysClientPreparer()
    @recorded_by_proxy
    def test_multitenant_authentication(self, client, is_hsm, **kwargs):
        if not self.is_live:
            pytest.skip("This test is incompatible with test proxy in playback")

        client_id = os.environ.get("KEYVAULT_CLIENT_ID")
        client_secret = os.environ.get("KEYVAULT_CLIENT_SECRET")
        if not (client_id and client_secret):
            pytest.skip("Values for KEYVAULT_CLIENT_ID and KEYVAULT_CLIENT_SECRET are required")

        # we set up a client for this method to align with the async test, but we actually want to create a new client
        # this new client should use a credential with an initially fake tenant ID and still succeed with a real request
        credential = ClientSecretCredential(
            tenant_id=str(uuid4()), client_id=client_id, client_secret=client_secret, additionally_allowed_tenants="*"
        )
        managed_hsm_url = kwargs.pop("managed_hsm_url", None)
        keyvault_url = kwargs.pop("vault_url", None)
        vault_url = managed_hsm_url if is_hsm else keyvault_url
        client = KeyClient(vault_url=vault_url, credential=credential)

        if self.is_live:
            time.sleep(2)  # to avoid throttling by the service
        key_name = self.get_resource_name("multitenant-key")
        key = client.create_rsa_key(key_name)
        assert key.id

        # try making another request with the credential's token revoked
        # the challenge policy should correctly request a new token for the correct tenant when a challenge is cached
        client._client._config.authentication_policy._token = None
        fetched_key = client.get_key(key_name)
        assert key.id == fetched_key.id

def empty_challenge_cache(fn):
    @functools.wraps(fn)
    def wrapper(**kwargs):
        HttpChallengeCache.clear()
        assert len(HttpChallengeCache._cache) == 0
        return fn(**kwargs)

    return wrapper


def get_random_url():
    """The challenge cache is keyed on URLs. Random URLs defend against tests interfering with each other."""

    return f"https://{uuid4()}.vault.azure.net/{uuid4()}".replace("-", "")


def add_url_port(url: str):
    """Like `get_random_url`, but includes a port number (comes after the domain, and before the path of the URL)."""

    parsed = urlparse(url)
    return f"{parsed.scheme}://{parsed.netloc}:443{parsed.path}"


def test_enforces_tls():
    url = "http://not.secure"
    HttpChallengeCache.set_challenge_for_url(url, HttpChallenge(url, "Bearer authorization=_, resource=_"))

    credential = Mock()
    pipeline = Pipeline(transport=Mock(), policies=[ChallengeAuthPolicy(credential)])
    with pytest.raises(ServiceRequestError):
        pipeline.run(HttpRequest("GET", url))



def test_challenge_cache():
    url_a = get_random_url()
    challenge_a = HttpChallenge(url_a, "Bearer authorization=authority A, resource=resource A")

    url_b = get_random_url()
    challenge_b = HttpChallenge(url_b, "Bearer authorization=authority B, resource=resource B")

    for url, challenge in zip((url_a, url_b), (challenge_a, challenge_b)):
        HttpChallengeCache.set_challenge_for_url(url, challenge)
        assert HttpChallengeCache.get_challenge_for_url(url) == challenge
        assert HttpChallengeCache.get_challenge_for_url(url + "/some/path") == challenge
        assert HttpChallengeCache.get_challenge_for_url(url + "/some/path?with-query=string") == challenge
        assert HttpChallengeCache.get_challenge_for_url(add_url_port(url)) == challenge

        HttpChallengeCache.remove_challenge_for_url(url)
        assert not HttpChallengeCache.get_challenge_for_url(url)


def test_challenge_parsing():
    tenant = "tenant"
    authority = f"https://login.authority.net/{tenant}"
    resource = "https://challenge.resource"
    challenge = HttpChallenge(
        "https://request.uri", challenge=f"Bearer authorization={authority}, resource={resource}"
    )

    assert challenge.get_authorization_server() == authority
    assert challenge.get_resource() == resource
    assert challenge.tenant_id == tenant


@empty_challenge_cache
def test_scope():
    """The policy's token requests should always be for an AADv2 scope"""

    expected_content = b"a duck"

    def test_with_challenge(challenge, expected_scope):
        expected_token = "expected_token"

        class Requests:
            count = 0

        def send(request):
            Requests.count += 1
            if Requests.count == 1:
                # first request should be unauthorized and have no content
                assert not request.body
                assert request.headers["Content-Length"] == "0"
                return challenge
            elif Requests.count == 2:
                # second request should be authorized according to challenge and have the expected content
                assert request.headers["Content-Length"]
                assert request.body == expected_content
                assert expected_token in request.headers["Authorization"]
                return Mock(status_code=200)
            raise ValueError("unexpected request")

        def get_token(*scopes, **_):
            assert len(scopes) == 1
            assert scopes[0] == expected_scope
            return AccessToken(expected_token, 0)

        credential = Mock(get_token=Mock(wraps=get_token))
        pipeline = Pipeline(policies=[ChallengeAuthPolicy(credential=credential)], transport=Mock(send=send))
        request = HttpRequest("POST", get_random_url())
        request.set_bytes_body(expected_content)
        pipeline.run(request)

        assert credential.get_token.call_count == 1

    endpoint = "https://authority.net/tenant"

    # an AADv1 resource becomes an AADv2 scope with the addition of '/.default'
    resource = "https://vault.azure.net"
    scope = resource + "/.default"

    challenge_with_resource = Mock(
        status_code=401,
        headers={"WWW-Authenticate": f'Bearer authorization="{endpoint}", resource={resource}'},
    )

    challenge_with_scope = Mock(
        status_code=401, headers={"WWW-Authenticate": f'Bearer authorization="{endpoint}", scope={scope}'}
    )

    test_with_challenge(challenge_with_resource, scope)
    test_with_challenge(challenge_with_scope, scope)


@empty_challenge_cache
def test_tenant():
    """The policy's token requests should pass the parsed tenant ID from the challenge"""

    expected_content = b"a duck"

    def test_with_challenge(challenge, expected_tenant):
        expected_token = "expected_token"

        class Requests:
            count = 0

        def send(request):
            Requests.count += 1
            if Requests.count == 1:
                # first request should be unauthorized and have no content
                assert not request.body
                assert request.headers["Content-Length"] == "0"
                return challenge
            elif Requests.count == 2:
                # second request should be authorized according to challenge and have the expected content
                assert request.headers["Content-Length"]
                assert request.body == expected_content
                assert expected_token in request.headers["Authorization"]
                return Mock(status_code=200)
            raise ValueError("unexpected request")

        def get_token(*_, **kwargs):
            assert kwargs.get("tenant_id") == expected_tenant
            return AccessToken(expected_token, 0)

        credential = Mock(get_token=Mock(wraps=get_token))
        pipeline = Pipeline(policies=[ChallengeAuthPolicy(credential=credential)], transport=Mock(send=send))
        request = HttpRequest("POST", get_random_url())
        request.set_bytes_body(expected_content)
        pipeline.run(request)

        assert credential.get_token.call_count == 1

    tenant = "tenant-id"
    endpoint = f"https://authority.net/{tenant}"
    resource = "https://vault.azure.net"

    challenge = Mock(
        status_code=401,
        headers={"WWW-Authenticate": f'Bearer authorization="{endpoint}", resource={resource}'},
    )

    test_with_challenge(challenge, tenant)


def test_policy_updates_cache():
    """
    It's possible for the challenge returned for a request to change, e.g. when a vault is moved to a new tenant.
    When the policy receives a 401, it should update the cached challenge for the requested URL, if one exists.
    """

    url = get_random_url()
    first_scope = "https://vault.azure.net/first-scope"
    first_token = "first-scope-token"
    second_scope = "https://vault.azure.net/second-scope"
    second_token = "second-scope-token"
    challenge_fmt = 'Bearer authorization="https://login.authority.net/tenant", resource='

    # mocking a tenant change:
    # 1. first request -> respond with challenge
    # 2. second request should be authorized according to the challenge
    # 3. third request should match the second (using a cached access token)
    # 4. fourth request should also match the second -> respond with a new challenge
    # 5. fifth request should be authorized according to the new challenge
    # 6. sixth request should match the fifth
    transport = validating_transport(
        requests=(
            Request(url),
            Request(url, required_headers={"Authorization": f"Bearer {first_token}"}),
            Request(url, required_headers={"Authorization": f"Bearer {first_token}"}),
            Request(url, required_headers={"Authorization": f"Bearer {first_token}"}),
            Request(url, required_headers={"Authorization": f"Bearer {second_token}"}),
            Request(url, required_headers={"Authorization": f"Bearer {second_token}"}),
        ),
        responses=(
            mock_response(status_code=401, headers={"WWW-Authenticate": challenge_fmt + first_scope}),
            mock_response(status_code=200),
            mock_response(status_code=200),
            mock_response(status_code=401, headers={"WWW-Authenticate": challenge_fmt + second_scope}),
            mock_response(status_code=200),
            mock_response(status_code=200),
        ),
    )

    credential = Mock(get_token=Mock(return_value=AccessToken(first_token, time.time() + 3600)))
    pipeline = Pipeline(policies=[ChallengeAuthPolicy(credential=credential)], transport=transport)

    # policy should complete and cache the first challenge and access token
    for _ in range(2):
        pipeline.run(HttpRequest("GET", url))
        assert credential.get_token.call_count == 1

    # The next request will receive a new challenge. The policy should handle it and update caches.
    credential.get_token.return_value = AccessToken(second_token, time.time() + 3600)
    for _ in range(2):
        pipeline.run(HttpRequest("GET", url))
        assert credential.get_token.call_count == 2



def test_token_expiration():
    """policy should not use a cached token which has expired"""

    url = get_random_url()

    expires_on = time.time() + 3600
    first_token = "*"
    second_token = "**"
    resource = "https://vault.azure.net"

    token = AccessToken(first_token, expires_on)

    def get_token(*_, **__):
        return token

    credential = Mock(get_token=Mock(wraps=get_token))
    transport = validating_transport(
        requests=[
            Request(),
            Request(required_headers={"Authorization": "Bearer " + first_token}),
            Request(required_headers={"Authorization": "Bearer " + first_token}),
            Request(required_headers={"Authorization": "Bearer " + second_token}),
        ],
        responses=[
            mock_response(
                status_code=401, headers={"WWW-Authenticate": f'Bearer authorization="{url}", resource={resource}'}
            )
        ]
        + [mock_response()] * 3,
    )
    pipeline = Pipeline(policies=[ChallengeAuthPolicy(credential=credential)], transport=transport)

    for _ in range(2):
        pipeline.run(HttpRequest("GET", url))
        assert credential.get_token.call_count == 1

    token = AccessToken(second_token, time.time() + 3600)
    with patch("time.time", lambda: expires_on):
        pipeline.run(HttpRequest("GET", url))
    assert credential.get_token.call_count == 2


@empty_challenge_cache
def test_preserves_options_and_headers():
    """After a challenge, the policy should send the original request with its options and headers preserved"""

    url = get_random_url()
    token = "**"
    resource = "https://vault.azure.net"

    def get_token(*_, **__):
        return AccessToken(token, 0)

    credential = Mock(get_token=Mock(wraps=get_token))

    transport = validating_transport(
        requests=[Request()] * 2 + [Request(required_headers={"Authorization": "Bearer " + token})],
        responses=[
            mock_response(
                status_code=401, headers={"WWW-Authenticate": f'Bearer authorization="{url}", resource={resource}'}
            )
        ]
        + [mock_response()] * 2,
    )

    key = "foo"
    value = "bar"

    def add(request):
        # add the expected option and header
        request.context.options[key] = value
        request.http_request.headers[key] = value

    adder = Mock(spec_set=SansIOHTTPPolicy, on_request=Mock(wraps=add), on_exception=lambda _: False)

    def verify(request):
        # authorized (non-challenge) requests should have the expected option and header
        if request.http_request.headers.get("Authorization"):
            assert request.context.options.get(key) == value, "request option wasn't preserved across challenge"
            assert request.http_request.headers.get(key) == value, "headers wasn't preserved across challenge"

    verifier = Mock(spec=SansIOHTTPPolicy, on_request=Mock(wraps=verify))

    challenge_policy = ChallengeAuthPolicy(credential=credential)
    policies = [adder, challenge_policy, verifier]
    pipeline = Pipeline(policies=policies, transport=transport)

    pipeline.run(HttpRequest("GET", url))

    # ensure the mock sans I/O policies were called
    assert adder.on_request.called, "mock policy wasn't invoked"
    assert verifier.on_request.called, "mock policy wasn't invoked"


@empty_challenge_cache
@pytest.mark.parametrize("verify_challenge_resource", [True, False])
def test_verify_challenge_resource_matches(verify_challenge_resource):
    """The auth policy should raise if the challenge resource doesn't match the request URL unless check is disabled"""

    url = get_random_url()
    url_with_port = add_url_port(url)
    token = "**"
    resource = "https://myvault.azure.net"  # Doesn't match a "".vault.azure.net" resource because of the "my" prefix

    def get_token(*_, **__):
        return AccessToken(token, 0)

    credential = Mock(get_token=Mock(wraps=get_token))

    transport = validating_transport(
        requests=[Request(), Request(required_headers={"Authorization": f"Bearer {token}"})],
        responses=[
            mock_response(
                status_code=401, headers={"WWW-Authenticate": f'Bearer authorization="{url}", resource={resource}'}
            ),
            mock_response(status_code=200, json_payload={"key": {"kid": f"{url}/key-name"}})
        ]
    )
    transport_2 = validating_transport(
        requests=[Request(), Request(required_headers={"Authorization": f"Bearer {token}"})],
        responses=[
            mock_response(
                status_code=401, headers={"WWW-Authenticate": f'Bearer authorization="{url}", resource={resource}'}
            ),
            mock_response(status_code=200, json_payload={"key": {"kid": f"{url}/key-name"}})
        ]
    )

    client = KeyClient(url, credential, transport=transport, verify_challenge_resource=verify_challenge_resource)
    client_with_port = KeyClient(
        url_with_port, credential, transport=transport_2, verify_challenge_resource=verify_challenge_resource
    )

    if verify_challenge_resource:
        with pytest.raises(ValueError) as e:
            client.get_key("key-name")
        assert f"The challenge resource 'myvault.azure.net' does not match the requested domain" in str(e.value)
        with pytest.raises(ValueError) as e:
            client_with_port.get_key("key-name")
        assert f"The challenge resource 'myvault.azure.net' does not match the requested domain" in str(e.value)
    else:
        key = client.get_key("key-name")
        assert key.name == "key-name"
        key = client_with_port.get_key("key-name")
        assert key.name == "key-name"


@empty_challenge_cache
@pytest.mark.parametrize("verify_challenge_resource", [True, False])
def test_verify_challenge_resource_valid(verify_challenge_resource):
    """The auth policy should raise if the challenge resource isn't a valid URL unless check is disabled"""

    url = get_random_url()
    token = "**"
    resource = "bad-resource"

    def get_token(*_, **__):
        return AccessToken(token, 0)

    credential = Mock(get_token=Mock(wraps=get_token))

    transport = validating_transport(
        requests=[Request(), Request(required_headers={"Authorization": f"Bearer {token}"})],
        responses=[
            mock_response(
                status_code=401, headers={"WWW-Authenticate": f'Bearer authorization="{url}", resource={resource}'}
            ),
            mock_response(status_code=200, json_payload={"key": {"kid": f"{url}/key-name"}})
        ]
    )

    client = KeyClient(url, credential, transport=transport, verify_challenge_resource=verify_challenge_resource)

    if verify_challenge_resource:
        with pytest.raises(ValueError) as e:
            client.get_key("key-name")
        assert "The challenge contains invalid scope" in str(e.value)
    else:
        key = client.get_key("key-name")
        assert key.name == "key-name"