tests: OAuth2 - Replace Python `/userinfo` endpoint with Caddy

Better documented, easier flow and separation of concerns via Caddy.

The python code had additional noise related to setting up a basic API which is abstracted away via `Caddyfile` config that's dedicated to this task.

test/config/oauth2/Caddyfile

@@ -0,0 +1,67 @@
+# Mocked OAuth2 /userinfo endpoint normally provided via an Authorization Server (AS) / Identity Provider (IdP)
+#
+# Dovecot will query the mocked `/userinfo` endpoint with the OAuth2 bearer token it was provided during login.
+# If the session for the token is valid, a response returns an attribute to perform a UserDB lookup on (default: email).
+
+:80 {
+  # This is the `/userinfo` endpoint that Dovecot connects to with the OAuth2 setting (default: `introspection_mode = auth`).
+  # Example: curl http://auth.example.test/userinfo -H 'Authorization: Bearer <token here>'
+  handle_path /userinfo {
+    reverse_proxy localhost:2000
+  }
+
+  # An additional endpoint for maintainers to generate `test/files/auth/imap-oauth2-auth.txt`
+  handle_path /imap/xoauth2 {
+    reverse_proxy localhost:3000
+  }
+}
+
+#
+# Internal blocks below provide actual endpoint logic
+#
+
+# /userinfo
+:2000 {
+  # OAuth2.0 Bearer token (paste into https://jwt.io/ to check it's contents).
+  # You should never need to edit this unless you REALLY need to change the issuer.
+  vars token "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vcHJvdmlkZXIuZXhhbXBsZS50ZXN0OjgwMDAvIiwic3ViIjoiODJjMWMzMzRkY2M2ZTMxMWFlNGFhZWJmZTk0NmM1ZTg1OGYwNTVhZmYxY2U1YTM3YWE3Y2M5MWFhYjE3ZTM1YyIsImF1ZCI6Im1haWxzZXJ2ZXIiLCJ1aWQiOiI4OU4zR0NuN1M1Y090WkZNRTVBeVhNbmxURFdVcnEzRmd4YWlyWWhFIn0.zuCytArbphhJn9XT_y9cBdGqDCNo68tBrtOwPIsuKNyF340SaOuZa0xarZofygytdDpLtYr56QlPTKImi-n1ZWrHkRZkwrQi5jQ-j_n2hEAL0vUToLbDnXYfc5q2w7z7X0aoCmiK8-fV7Kx4CVTM7riBgpElf6F3wNAIcX6R1ijUh6ISCL0XYsdogf8WUNZipXY-O4R7YHXdOENuOp3G48hWhxuUh9PsUqE5yxDwLsOVzCTqg9S5gxPQzF2eCN9J0I2XiIlLKvLQPIZ2Y_K7iYvVwjpNdgb4xhm9wuKoIVinYkF_6CwIzAawBWIDJAbix1IslkUPQMGbupTDtOgTiQ"
+
+  # Expects to match an authorization header with a specific bearer token:
+  # https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication#authentication_schemes
+  @auth header Authorization "Bearer {vars.token}"
+
+  # If the provided authorization header has the expected value (bearer token), respond with this JSON payload:
+  handle @auth {
+    # JSON inlined via HereDoc string feature:
+    # Dovecot OAuth2 defaults to `username_attribute = email`, which must be returned in the response to match
+    # with the `user` credentials field that Dovecot received via base64 encoded IMAP `AUTHENTICATE` value.
+    respond <<EOF
+{
+      "email": "user1@localhost.localdomain",
+      "email_verified": true,
+      "sub": "82c1c334dcc6e311ae4aaebfe946c5e858f055aff1ce5a37aa7cc91aab17e35c"
+    }
+    EOF
+  }
+
+  # Failed to authorize, close connection and send a 401 status (unauthorized):
+  respond 401 {
+    close
+  }
+}
+
+# /imap/xoauth2
+# Responds with the auth string (base64 encoded) for use with the IMAP `AUTHENTICATE` command:
+# curl http://auth.example.test/imap/xoauth2
+# When Dovecot queries /userinfo endpoint, it will be after base64 decoding the IMAP `AUTHENTICATE` value,
+# and sending the `auth` value from the `credentials` variable as an HTTP Authorization header.
+:3000 {
+  route {
+    vars token "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vcHJvdmlkZXIuZXhhbXBsZS50ZXN0OjgwMDAvIiwic3ViIjoiODJjMWMzMzRkY2M2ZTMxMWFlNGFhZWJmZTk0NmM1ZTg1OGYwNTVhZmYxY2U1YTM3YWE3Y2M5MWFhYjE3ZTM1YyIsImF1ZCI6Im1haWxzZXJ2ZXIiLCJ1aWQiOiI4OU4zR0NuN1M1Y090WkZNRTVBeVhNbmxURFdVcnEzRmd4YWlyWWhFIn0.zuCytArbphhJn9XT_y9cBdGqDCNo68tBrtOwPIsuKNyF340SaOuZa0xarZofygytdDpLtYr56QlPTKImi-n1ZWrHkRZkwrQi5jQ-j_n2hEAL0vUToLbDnXYfc5q2w7z7X0aoCmiK8-fV7Kx4CVTM7riBgpElf6F3wNAIcX6R1ijUh6ISCL0XYsdogf8WUNZipXY-O4R7YHXdOENuOp3G48hWhxuUh9PsUqE5yxDwLsOVzCTqg9S5gxPQzF2eCN9J0I2XiIlLKvLQPIZ2Y_K7iYvVwjpNdgb4xhm9wuKoIVinYkF_6CwIzAawBWIDJAbix1IslkUPQMGbupTDtOgTiQ"
+    vars user "user1@localhost.localdomain"
+    vars credentials "user={vars.user}\001auth=Bearer {vars.token}\001\001"
+  }
+
+  templates
+  respond "{{b64enc \"{vars.credentials}\"}}"
+}

test/config/oauth2/provider.py

@@ -1,56 +0,0 @@
-# OAuth2 mock service
-#
-# Dovecot will query this service with the token it was provided.
-# If the session for the token is valid, a response provides an attribute to perform a UserDB lookup on (default: email).
-
-import json
-import base64
-from http.server import BaseHTTPRequestHandler, HTTPServer
-
-# OAuth2.0 Bearer token (paste into https://jwt.io/ to check it's contents).
-# You should never need to edit this unless you REALLY need to change the issuer.
-token = "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vcHJvdmlkZXIuZXhhbXBsZS50ZXN0OjgwMDAvIiwic3ViIjoiODJjMWMzMzRkY2M2ZTMxMWFlNGFhZWJmZTk0NmM1ZTg1OGYwNTVhZmYxY2U1YTM3YWE3Y2M5MWFhYjE3ZTM1YyIsImF1ZCI6Im1haWxzZXJ2ZXIiLCJ1aWQiOiI4OU4zR0NuN1M1Y090WkZNRTVBeVhNbmxURFdVcnEzRmd4YWlyWWhFIn0.zuCytArbphhJn9XT_y9cBdGqDCNo68tBrtOwPIsuKNyF340SaOuZa0xarZofygytdDpLtYr56QlPTKImi-n1ZWrHkRZkwrQi5jQ-j_n2hEAL0vUToLbDnXYfc5q2w7z7X0aoCmiK8-fV7Kx4CVTM7riBgpElf6F3wNAIcX6R1ijUh6ISCL0XYsdogf8WUNZipXY-O4R7YHXdOENuOp3G48hWhxuUh9PsUqE5yxDwLsOVzCTqg9S5gxPQzF2eCN9J0I2XiIlLKvLQPIZ2Y_K7iYvVwjpNdgb4xhm9wuKoIVinYkF_6CwIzAawBWIDJAbix1IslkUPQMGbupTDtOgTiQ"
-
-# This is the string the user-facing client (e.g. Roundcube) should send via IMAP to Dovecot.
-# We include the user and the above token separated by '\1' chars as per the XOAUTH2 spec.
-xoauth2 = base64.b64encode(f"user=user1@localhost.localdomain\1auth=Bearer {token}\1\1".encode("utf-8"))
-# If changing the user above, use the new output from the below line with the contents of the AUTHENTICATE command in test/test-files/auth/imap-oauth2-auth.txt
-print("XOAUTH2 string: " + str(xoauth2))
-
-
-class HTTPRequestHandler(BaseHTTPRequestHandler):
-    def do_GET(self):
-        auth = self.headers.get("Authorization")
-        if auth is None:
-            self.send_response(401)
-            self.end_headers()
-            return
-        if len(auth.split()) != 2:
-            self.send_response(401)
-            self.end_headers()
-            return
-        auth = auth.split()[1]
-        # Valid session, respond with JSON containing the expected `email` claim to match as Dovecot username:
-        if auth == token:
-            self.send_response(200)
-            self.send_header('Content-Type', 'application/json')
-            self.end_headers()
-            self.wfile.write(json.dumps({
-                "email": "user1@localhost.localdomain",
-                "email_verified": True,
-                "sub": "82c1c334dcc6e311ae4aaebfe946c5e858f055aff1ce5a37aa7cc91aab17e35c"
-            }).encode("utf-8"))
-        else:
-            self.send_response(401)
-        self.end_headers()
-
-server = HTTPServer(('', 80), HTTPRequestHandler)
-print("Starting server", flush=True)
-
-try:
-    server.serve_forever()
-except KeyboardInterrupt:
-    print()
-    print("Received keyboard interrupt")
-finally:
-    print("Exiting")

test/tests/serial/mail_with_oauth2.bats

@@ -19,11 +19,10 @@ function setup_file() {
   docker run --rm -d --name "${CONTAINER2_NAME}" \
     --hostname "${FQDN_OAUTH2}" \
     --network "${DMS_TEST_NETWORK}" \
-    --volume "${REPOSITORY_ROOT}/test/config/oauth2/:/app/" \
+    --volume "${REPOSITORY_ROOT}/test/config/oauth2/Caddyfile:/etc/caddy/Caddyfile:ro" \
-    docker.io/library/python:latest \
+    caddy:2.7
-    python /app/provider.py
 
-  _run_until_success_or_timeout 20 sh -c "docker logs ${CONTAINER2_NAME} 2>&1 | grep 'Starting server'"
+  _run_until_success_or_timeout 20 sh -c "docker logs ${CONTAINER2_NAME} 2>&1 | grep 'serving initial configuration'"
 
   #
   # Setup DMS container