grain.social
Grain flutter app
refactor: remove dpop
chadtmiller.com
-153
lib/dpop_client.dart
-153
lib/dpop_client.dart
···
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import 'dart:convert';
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import 'package:crypto/crypto.dart';
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import 'package:http/http.dart' as http;
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import 'package:jose/jose.dart';
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import 'package:uuid/uuid.dart';
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class DpopHttpClient {
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final JsonWebKey dpopKey;
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final Map<String, String> _nonces = {}; // origin -> nonce
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DpopHttpClient({required this.dpopKey});
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/// Extract origin (scheme + host + port) from a URL
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String _extractOrigin(String url) {
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final uri = Uri.parse(url);
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final portPart = (uri.hasPort && uri.port != 80 && uri.port != 443) ? ':${uri.port}' : '';
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return '${uri.scheme}://${uri.host}$portPart';
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}
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/// Strip query and fragment from URL per spec
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String _buildHtu(String url) {
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final uri = Uri.parse(url);
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return '${uri.scheme}://${uri.host}${uri.path}';
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}
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/// Calculate ath claim: base64url(sha256(access_token))
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String _calculateAth(String accessToken) {
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final hash = sha256.convert(utf8.encode(accessToken));
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return base64Url.encode(hash.bytes).replaceAll('=', '');
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}
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/// Calculate the JWK Thumbprint for EC or RSA keys per RFC 7638.
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/// The input [jwk] is the public part of your key as a Map`<String, dynamic>`.
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///
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/// For EC keys, required fields are: crv, kty, x, y
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/// For RSA keys, required fields are: e, kty, n
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String calculateJwkThumbprint(Map<String, dynamic> jwk) {
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late Map<String, String> ordered;
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if (jwk['kty'] == 'EC') {
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ordered = {'crv': jwk['crv'], 'kty': jwk['kty'], 'x': jwk['x'], 'y': jwk['y']};
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} else if (jwk['kty'] == 'RSA') {
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ordered = {'e': jwk['e'], 'kty': jwk['kty'], 'n': jwk['n']};
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} else {
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throw ArgumentError('Unsupported key type for thumbprint calculation');
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}
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final jsonString = jsonEncode(ordered);
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final digest = sha256.convert(utf8.encode(jsonString));
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return base64Url.encode(digest.bytes).replaceAll('=', '');
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}
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/// Build the DPoP JWT proof
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Future<String> _buildProof({
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required String htm,
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required String htu,
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String? nonce,
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String? ath,
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}) async {
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final now = (DateTime.now().millisecondsSinceEpoch / 1000).floor();
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final jti = Uuid().v4();
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final publicJwk = Map<String, String>.from(dpopKey.toJson())..remove('d');
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final payload = {
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'htu': htu,
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'htm': htm,
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'iat': now,
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'jti': jti,
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if (nonce != null) 'nonce': nonce,
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if (ath != null) 'ath': ath,
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};
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final builder = JsonWebSignatureBuilder()
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..jsonContent = payload
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..addRecipient(dpopKey, algorithm: dpopKey.algorithm)
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..setProtectedHeader('typ', 'dpop+jwt')
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..setProtectedHeader('jwk', publicJwk);
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final jws = builder.build();
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return jws.toCompactSerialization();
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}
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/// Public method to send requests with DPoP proof, retries once on use_dpop_nonce error
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Future<http.Response> send({
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required String method,
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required Uri url,
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required String accessToken,
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Map<String, String>? headers,
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Object? body,
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}) async {
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final origin = _extractOrigin(url.toString());
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final nonce = _nonces[origin];
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final htu = _buildHtu(url.toString());
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final ath = _calculateAth(accessToken);
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final proof = await _buildProof(htm: method.toUpperCase(), htu: htu, nonce: nonce, ath: ath);
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// Compose headers, allowing override of Content-Type for raw uploads
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final requestHeaders = <String, String>{
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'Authorization': 'DPoP $accessToken',
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'DPoP': proof,
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if (headers != null) ...headers,
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};
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http.Response response;
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switch (method.toUpperCase()) {
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case 'GET':
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response = await http.get(url, headers: requestHeaders);
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break;
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case 'POST':
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response = await http.post(url, headers: requestHeaders, body: body);
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break;
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case 'PUT':
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response = await http.put(url, headers: requestHeaders, body: body);
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break;
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case 'DELETE':
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response = await http.delete(url, headers: requestHeaders, body: body);
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break;
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default:
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throw UnsupportedError('Unsupported HTTP method: $method');
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}
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final newNonce = response.headers['dpop-nonce'];
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if (newNonce != null && newNonce != nonce) {
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// Save new nonce for origin
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_nonces[origin] = newNonce;
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}
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if (response.statusCode == 401) {
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final wwwAuth = response.headers['www-authenticate'];
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if (wwwAuth != null &&
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wwwAuth.contains('DPoP') &&
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wwwAuth.contains('error="use_dpop_nonce"') &&
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newNonce != null &&
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newNonce != nonce) {
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// Retry once with updated nonce
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return send(
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method: method,
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url: url,
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accessToken: accessToken,
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headers: headers,
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body: body,
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);
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}
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}
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return response;
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}
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}