app/endpoints/oauth.py

#!/usr/bin/env python3
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# to you under the Apache License, Version 2.0 (the
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#
#   http://www.apache.org/licenses/LICENSE-2.0
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"""OAuth+OIDC Portal for the Apache Software Foundation"""

import quart
import re
from ..lib import middleware, config, ldap

from oic import rndstr
from oic.oic import Client
import oic.utils.authn.client
import oic.oic.message
import oic.utils.keyio
import urllib.parse


def make_client():
    """Construct a useful OIDC client from our config yaml"""
    client = Client(
        client_id=config.oidc.client_id,
        client_authn_method=oic.utils.authn.client.CLIENT_AUTHN_METHOD,
    )

    client_reg = oic.oic.message.RegistrationResponse(
        client_id=config.oidc.client_id,
        client_secret=config.oidc.client_secret,
        redirect_uris=[config.oidc.redirect_uri],
    )

    provider = oic.oic.message.ProviderConfigurationResponse(
        version="1.0",
        issuer=config.oidc.issuer,
        authorization_endpoint=config.oidc.endpoint + "auth",
        token_endpoint=config.oidc.endpoint + "token",
        jwks_uri=config.oidc.endpoint + "certs",
        userinfo_endpoint=config.oidc.endpoint + "userinfo",
    )

    client.handle_provider_config(provider, provider["issuer"])
    client.store_registration_info(client_reg)
    client.redirect_uris = [
        config.oidc.redirect_uri,
    ]

    return client


def make_redirect_url(url, **kwargs):
    """Appends any number of query string args to an existing URL"""
    # Parse original URL, so we can munge it with our token
    origin_url = urllib.parse.unquote(url)
    url_parsed = urllib.parse.urlparse(origin_url)
    args = dict(urllib.parse.parse_qsl(url_parsed.query))

    # Add the token
    args.update(**kwargs)

    # Encode args and reconstruct URL
    args_encoded = urllib.parse.urlencode(args, doseq=True)

    new_url = urllib.parse.ParseResult(
        url_parsed.scheme, url_parsed.netloc, url_parsed.path, url_parsed.params, args_encoded, url_parsed.fragment
    ).geturl()

    return new_url


states = {}  # Track current oauth states
client = make_client()  # OIDC client


async def init_oidc(form_data):
    """Initial OAuth gateway. Verify parameters, log state, punt auth to OIDC"""
    origin_state = form_data.get("state")
    redirect_uri = form_data.get("redirect_uri")

    # Validate state and callback
    if not origin_state or len(origin_state) < 10 or len(origin_state) > 64:
        return quart.Response(
            status=400, response="Origin OAuth state ID MUST be between 10 and 64 characters", mimetype="text/plain"
        )
    if not re.match(r"^[-a-z0-9]+$", origin_state):
        return quart.Response(status=400, response="Origin state ID MUST be hex or alphanumerical (dashes are allowed)")
    if not redirect_uri or not re.match(r"https://([-0-9a-zA-Z\.]+)", redirect_uri):
        return quart.Response(
            status=400,
            response="Invalid redirect URI specified. MUST be of format https://foo.bar/baz.html and MUST be https",
        )

    session = {
        "state": rndstr(),
        "nonce": rndstr(),
        "original_state": origin_state,
        "redirect_uri": redirect_uri,
    }
    args = {
        "client_id": config.oidc.client_id,
        "response_type": "code",
        "scope": ["openid"],
        "state": session["state"],
        "nonce": session["nonce"],
        "redirect_uri": config.oidc.redirect_uri,
    }
    auth_req = client.construct_AuthorizationRequest(request_args=args)
    login_url = auth_req.request(client.authorization_endpoint)
    states[session["state"]] = session
    return quart.Response(
        status=302,
        response="Redirecting...",
        headers={
            "Location": login_url,
        },
    )


async def callback_oidc(form_data):
    """OIDC callback. Ensure OIDC response is valid, obtain a token, verify username"""
    aresp = client.parse_response(oic.oic.message.AuthorizationResponse, info=form_data, sformat="dict")
    oidc_state = aresp.get("state")
    oidc_code = aresp.get("code")
    if oidc_state not in states:
        return quart.Response(status=400, response="Unknown session, perhaps it expired? Please retry your login.")

    resp = client.do_access_token_request(
        scope=["openid"],
        state=oidc_state,
        request_args={"code": oidc_code},
    )
    if isinstance(resp, oic.oic.message.AccessTokenResponse):  # Could be ErrorResponse, we don't want that...
        userinfo = client.do_user_info_request(state=oidc_state)
        if userinfo:
            username = userinfo["preferred_username"]
            committer = ldap.Committer(username)
            details = await committer.verify()
            if details:
                states[oidc_state]["credentials"] = details
                url = make_redirect_url(states[oidc_state]["redirect_uri"], code=oidc_state)
                return quart.Response(
                    status=302,
                    response="Redirecting...",
                    headers={
                        "Location": url,
                    },
                )
    return quart.Response(status=400, response="The OIDC provider did not respond well....booo")


async def token_oidc(form_data):
    """Token response. Given a valid oauth token, presents the backend client with committer details"""
    code = form_data.get("code")
    if code and code in states:
        credentials = states[code]["credentials"]
        del states[code]
        return credentials
    return quart.Response(status=404, response="Could not find the login session that was requested.")


# Endpoint for OAuth init
quart.current_app.add_url_rule(
    "/oauth-oidc",
    methods=[
        "GET",
    ],
    view_func=middleware.glued(init_oidc),
)

# Second endpoint for OAuth init, allowing for backwards compat (auth instead of oauth)
quart.current_app.add_url_rule(
    "/auth-oidc",
    methods=[
        "GET",
    ],
    view_func=middleware.glued(init_oidc),
)

# Endpoint for callback from OIDC Provider
quart.current_app.add_url_rule(
    "/callback-oidc",
    methods=[
        "GET",
    ],
    view_func=middleware.glued(callback_oidc),
)

# Endpoint for backend requesting OAuth data
quart.current_app.add_url_rule(
    "/token-oidc",
    methods=["GET", "POST"],
    view_func=middleware.glued(token_oidc),
)