feat(web/converse): Import repository

Imports the converse forum software I wrote a few years ago. I want to
clean this up a bit and try using Hotwire with it.

Note: The original repository was AGPL-3.0 licensed. I'm the copyright
holder and have relicensed it to GPL-3.0 in the commit that is being
merged.

Imported from: https://github.com/tazjin/converse

git-subtree-dir: web/converse
git-subtree-mainline: 386afdc794
git-subtree-split: 09168021e7
Change-Id: Ia8b587db5174ef5b3c52910d3d027199150c58e0

web/converse/src/oidc.rs

@@ -0,0 +1,149 @@
+// Copyright (C) 2018-2021 Vincent Ambo <tazjin@tvl.su>
+//
+// This file is part of Converse.
+//
+// This program is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see
+// <https://www.gnu.org/licenses/>.
+
+//! This module provides authentication via OIDC compliant
+//! authentication sources.
+//!
+//! Currently Converse only supports a single OIDC provider. Note that
+//! this has so far only been tested with Office365.
+
+use actix::prelude::*;
+use reqwest;
+use url::Url;
+use url_serde;
+use errors::*;
+use reqwest::header::Authorization;
+use hyper::header::Bearer;
+
+/// This structure represents the contents of an OIDC discovery
+/// document.
+#[derive(Deserialize, Debug, Clone)]
+pub struct OidcConfig {
+    #[serde(with = "url_serde")]
+    authorization_endpoint: Url,
+    token_endpoint: String,
+    userinfo_endpoint: String,
+
+    scopes_supported: Vec<String>,
+    issuer: String,
+}
+
+#[derive(Clone, Debug)]
+pub struct OidcExecutor {
+    pub client_id: String,
+    pub client_secret: String,
+    pub redirect_uri: String,
+    pub oidc_config: OidcConfig,
+}
+
+/// This struct represents the form response returned by an OIDC
+/// provider with the `code`.
+#[derive(Debug, Deserialize)]
+pub struct CodeResponse {
+    pub code: String,
+}
+
+/// This struct represents the data extracted from the ID token and
+/// stored in the user's session.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Author {
+    pub name: String,
+    pub email: String,
+}
+
+impl Actor for OidcExecutor {
+    type Context = Context<Self>;
+}
+
+/// Message used to request the login URL:
+pub struct GetLoginUrl; // TODO: Add a nonce parameter stored in session.
+message!(GetLoginUrl, String);
+
+impl Handler<GetLoginUrl> for OidcExecutor {
+    type Result = String;
+
+    fn handle(&mut self, _: GetLoginUrl, _: &mut Self::Context) -> Self::Result {
+        let mut url: Url = self.oidc_config.authorization_endpoint.clone();
+        {
+            let mut params = url.query_pairs_mut();
+            params.append_pair("client_id", &self.client_id);
+            params.append_pair("response_type", "code");
+            params.append_pair("scope", "openid");
+            params.append_pair("redirect_uri", &self.redirect_uri);
+            params.append_pair("response_mode", "form_post");
+        }
+        return url.into_string();
+    }
+}
+
+/// Message used to request the token from the returned code and
+/// retrieve userinfo from the appropriate endpoint.
+pub struct RetrieveToken(pub CodeResponse);
+message!(RetrieveToken, Result<Author>);
+
+#[derive(Debug, Deserialize)]
+struct TokenResponse {
+    access_token: String,
+}
+
+// TODO: This is currently hardcoded to Office365 fields.
+#[derive(Debug, Deserialize)]
+struct Userinfo {
+    name: String,
+    unique_name: String, // email in office365
+}
+
+impl Handler<RetrieveToken> for OidcExecutor {
+    type Result = Result<Author>;
+
+    fn handle(&mut self, msg: RetrieveToken, _: &mut Self::Context) -> Self::Result {
+        debug!("Received OAuth2 code, requesting access_token");
+        let client = reqwest::Client::new();
+        let params: [(&str, &str); 5] = [
+            ("client_id", &self.client_id),
+            ("client_secret", &self.client_secret),
+            ("grant_type", "authorization_code"),
+            ("code", &msg.0.code),
+            ("redirect_uri", &self.redirect_uri),
+        ];
+
+        let mut response = client.post(&self.oidc_config.token_endpoint)
+            .form(&params)
+            .send()?;
+
+        debug!("Received token response: {:?}", response);
+        let token: TokenResponse = response.json()?;
+
+        let user: Userinfo = client.get(&self.oidc_config.userinfo_endpoint)
+            .header(Authorization(Bearer { token: token.access_token }))
+            .send()?
+            .json()?;
+
+        Ok(Author {
+            name: user.name,
+            email: user.unique_name,
+        })
+    }
+}
+
+/// Convenience function to attempt loading an OIDC discovery document
+/// from a specified URL:
+pub fn load_oidc(url: &str) -> Result<OidcConfig> {
+    let config: OidcConfig = reqwest::get(url)?.json()?;
+    Ok(config)
+}