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1package oauth
2
3import (
4 "context"
5 "crypto/ecdsa"
6 "crypto/rand"
7 "crypto/sha256"
8 "encoding/base64"
9 "encoding/hex"
10 "encoding/json"
11 "fmt"
12 "io"
13 "net/http"
14 "net/url"
15 "strings"
16 "time"
17
18 "github.com/golang-jwt/jwt/v5"
19 "github.com/google/uuid"
20 "github.com/lestrrat-go/jwx/v2/jwk"
21)
22
23type OauthClient struct {
24 h *http.Client
25 clientPrivateKey *ecdsa.PrivateKey
26 clientKid string
27 clientId string
28 redirectUri string
29}
30
31type OauthClientArgs struct {
32 H *http.Client
33 ClientJwk jwk.Key
34 ClientId string
35 RedirectUri string
36}
37
38func NewOauthClient(args OauthClientArgs) (*OauthClient, error) {
39 if args.ClientId == "" {
40 return nil, fmt.Errorf("no client id provided")
41 }
42
43 if args.RedirectUri == "" {
44 return nil, fmt.Errorf("no redirect uri provided")
45 }
46
47 if args.H == nil {
48 args.H = &http.Client{
49 Timeout: 5 * time.Second,
50 }
51 }
52
53 clientPkey, err := getPrivateKey(args.ClientJwk)
54 if err != nil {
55 return nil, fmt.Errorf("could not load private key from provided client jwk: %w", err)
56 }
57
58 kid := args.ClientJwk.KeyID()
59
60 return &OauthClient{
61 h: args.H,
62 clientKid: kid,
63 clientPrivateKey: clientPkey,
64 clientId: args.ClientId,
65 redirectUri: args.RedirectUri,
66 }, nil
67}
68
69func (c *OauthClient) ResolvePDSAuthServer(ctx context.Context, ustr string) (string, error) {
70 u, err := isSafeAndParsed(ustr)
71 if err != nil {
72 return "", err
73 }
74
75 u.Path = "/.well-known/oauth-protected-resource"
76
77 req, err := http.NewRequestWithContext(ctx, "GET", u.String(), nil)
78 if err != nil {
79 return "", fmt.Errorf("error creating request for oauth protected resource: %w", err)
80 }
81
82 resp, err := c.h.Do(req)
83 if err != nil {
84 return "", fmt.Errorf("could not get response from server: %w", err)
85 }
86 defer resp.Body.Close()
87
88 if resp.StatusCode != http.StatusOK {
89 io.Copy(io.Discard, resp.Body)
90 return "", fmt.Errorf("received non-200 response from pds. code was %d", resp.StatusCode)
91 }
92
93 b, err := io.ReadAll(resp.Body)
94 if err != nil {
95 return "", fmt.Errorf("could not read body: %w", err)
96 }
97
98 var resource OauthProtectedResource
99 if err := resource.UnmarshalJSON(b); err != nil {
100 return "", fmt.Errorf("could not unmarshal json: %w", err)
101 }
102
103 if len(resource.AuthorizationServers) == 0 {
104 return "", fmt.Errorf("oauth protected resource contained no authorization servers")
105 }
106
107 return resource.AuthorizationServers[0], nil
108}
109
110func (c *OauthClient) FetchAuthServerMetadata(
111 ctx context.Context,
112 ustr string,
113) (*OauthAuthorizationMetadata, error) {
114 u, err := isSafeAndParsed(ustr)
115 if err != nil {
116 return nil, err
117 }
118
119 u.Path = "/.well-known/oauth-authorization-server"
120
121 req, err := http.NewRequestWithContext(ctx, "GET", u.String(), nil)
122 if err != nil {
123 return nil, fmt.Errorf("error creating request to fetch auth metadata: %w", err)
124 }
125
126 resp, err := c.h.Do(req)
127 if err != nil {
128 return nil, fmt.Errorf("error getting response for auth metadata: %w", err)
129 }
130 defer resp.Body.Close()
131
132 if resp.StatusCode != http.StatusOK {
133 io.Copy(io.Discard, resp.Body)
134 return nil, fmt.Errorf(
135 "received non-200 response from pds. status code was %d",
136 resp.StatusCode,
137 )
138 }
139
140 b, err := io.ReadAll(resp.Body)
141 if err != nil {
142 return nil, fmt.Errorf("could not read body for metadata response: %w", err)
143 }
144
145 var metadata OauthAuthorizationMetadata
146 if err := metadata.UnmarshalJSON(b); err != nil {
147 return nil, fmt.Errorf("could not unmarshal metadata: %w", err)
148 }
149
150 if err := metadata.Validate(u); err != nil {
151 return nil, fmt.Errorf("could not validate metadata: %w", err)
152 }
153
154 return &metadata, nil
155}
156
157func (c *OauthClient) ClientAssertionJwt(authServerUrl string) (string, error) {
158 claims := jwt.MapClaims{
159 "iss": c.clientId,
160 "sub": c.clientId,
161 "aud": authServerUrl,
162 "jti": uuid.NewString(),
163 "iat": time.Now().Unix(),
164 }
165
166 token := jwt.NewWithClaims(jwt.SigningMethodES256, claims)
167 token.Header["kid"] = c.clientKid
168
169 tokenString, err := token.SignedString(c.clientPrivateKey)
170 if err != nil {
171 return "", err
172 }
173
174 return tokenString, nil
175}
176
177func (c *OauthClient) AuthServerDpopJwt(method, url, nonce string, privateJwk jwk.Key) (string, error) {
178 pubJwk, err := privateJwk.PublicKey()
179 if err != nil {
180 return "", err
181 }
182
183 b, err := json.Marshal(pubJwk)
184 if err != nil {
185 return "", err
186 }
187
188 var pubMap map[string]any
189 if err := json.Unmarshal(b, &pubMap); err != nil {
190 return "", err
191 }
192
193 now := time.Now().Unix()
194
195 claims := jwt.MapClaims{
196 "jti": uuid.NewString(),
197 "htm": method,
198 "htu": url,
199 "iat": now,
200 "exp": now + 30,
201 }
202
203 if nonce != "" {
204 claims["nonce"] = nonce
205 }
206
207 token := jwt.NewWithClaims(jwt.SigningMethodES256, claims)
208 token.Header["typ"] = "dpop+jwt"
209 token.Header["alg"] = "ES256"
210 token.Header["jwk"] = pubMap
211
212 var rawKey any
213 if err := privateJwk.Raw(&rawKey); err != nil {
214 return "", err
215 }
216
217 tokenString, err := token.SignedString(rawKey)
218 if err != nil {
219 return "", fmt.Errorf("failed to sign token: %w", err)
220 }
221
222 return tokenString, nil
223}
224
225type SendParAuthResponse struct {
226 PkceVerifier string
227 State string
228 DpopAuthserverNonce string
229 Resp map[string]any
230}
231
232func (c *OauthClient) SendParAuthRequest(ctx context.Context, authServerUrl string, authServerMeta *OauthAuthorizationMetadata, loginHint, scope string, dpopPrivateKey jwk.Key) (*SendParAuthResponse, error) {
233 if authServerMeta == nil {
234 return nil, fmt.Errorf("nil metadata provided")
235 }
236
237 parUrl := authServerMeta.PushedAuthorizationRequestEndpoint
238
239 state, err := generateToken(10)
240 if err != nil {
241 return nil, fmt.Errorf("could not generate state token: %w", err)
242 }
243
244 pkceVerifier, err := generateToken(48)
245 if err != nil {
246 return nil, fmt.Errorf("could not generate pkce verifier: %w", err)
247 }
248
249 codeChallenge := generateCodeChallenge(pkceVerifier)
250 codeChallengeMethod := "S256"
251
252 clientAssertion, err := c.ClientAssertionJwt(authServerUrl)
253 if err != nil {
254 return nil, err
255 }
256
257 dpopAuthserverNonce := ""
258 dpopProof, err := c.AuthServerDpopJwt("POST", parUrl, dpopAuthserverNonce, dpopPrivateKey)
259 if err != nil {
260 return nil, fmt.Errorf("error getting dpop proof: %w", err)
261 }
262
263 params := url.Values{
264 "response_type": {"code"},
265 "code_challenge": {codeChallenge},
266 "code_challenge_method": {codeChallengeMethod},
267 "client_id": {c.clientId},
268 "state": {state},
269 "redirect_uri": {c.redirectUri},
270 "scope": {scope},
271 "client_assertion_type": {"urn:ietf:params:oauth:client-assertion-type:jwt-bearer"},
272 "client_assertion": {clientAssertion},
273 }
274
275 if loginHint != "" {
276 params.Set("login_hint", loginHint)
277 }
278
279 _, err = isSafeAndParsed(parUrl)
280 if err != nil {
281 return nil, err
282 }
283
284 req, err := http.NewRequestWithContext(ctx, "POST", parUrl, strings.NewReader(params.Encode()))
285 if err != nil {
286 return nil, err
287 }
288
289 req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
290 req.Header.Set("DPoP", dpopProof)
291
292 resp, err := c.h.Do(req)
293 if err != nil {
294 return nil, err
295 }
296 defer resp.Body.Close()
297
298 var rmap map[string]any
299 if err := json.NewDecoder(resp.Body).Decode(&rmap); err != nil {
300 return nil, err
301 }
302
303 if resp.StatusCode == 400 && rmap["error"] == "use_dpop_nonce" {
304 dpopAuthserverNonce = resp.Header.Get("DPoP-Nonce")
305 dpopProof, err := c.AuthServerDpopJwt("POST", parUrl, dpopAuthserverNonce, dpopPrivateKey)
306 if err != nil {
307 return nil, err
308 }
309
310 req2, err := http.NewRequestWithContext(
311 ctx,
312 "POST",
313 parUrl,
314 strings.NewReader(params.Encode()),
315 )
316 if err != nil {
317 return nil, err
318 }
319
320 req2.Header.Set("Content-Type", "application/x-www-form-urlencoded")
321 req2.Header.Set("DPoP", dpopProof)
322
323 resp2, err := c.h.Do(req2)
324 if err != nil {
325 return nil, err
326 }
327 defer resp2.Body.Close()
328
329 rmap = map[string]any{}
330 if err := json.NewDecoder(resp2.Body).Decode(&rmap); err != nil {
331 return nil, err
332 }
333
334 fmt.Println(rmap)
335 }
336
337 return &SendParAuthResponse{
338 PkceVerifier: pkceVerifier,
339 State: state,
340 DpopAuthserverNonce: dpopAuthserverNonce,
341 Resp: rmap,
342 }, nil
343}
344
345type TokenResponse struct {
346 DpopAuthserverNonce string
347 Resp map[string]any
348}
349
350func (c *OauthClient) InitialTokenRequest(
351 ctx context.Context,
352 code,
353 appUrl,
354 authserverIss,
355 pkceVerifier,
356 dpopAuthserverNonce string,
357 dpopPrivateJwk jwk.Key,
358) (*TokenResponse, error) {
359 authserverMeta, err := c.FetchAuthServerMetadata(ctx, authserverIss)
360 if err != nil {
361 return nil, err
362 }
363
364 clientAssertion, err := c.ClientAssertionJwt(authserverIss)
365 if err != nil {
366 return nil, err
367 }
368
369 params := url.Values{
370 "client_id": {c.clientId},
371 "redirect_uri": {c.redirectUri},
372 "grant_type": {"authorization_code"},
373 "code": {code},
374 "code_verifier": {pkceVerifier},
375 "client_assertion_type": {"urn:ietf:params:oauth:client-assertion-type:jwt-bearer"},
376 "client_assertion": {clientAssertion},
377 }
378
379 dpopProof, err := c.AuthServerDpopJwt(
380 "POST",
381 authserverMeta.TokenEndpoint,
382 dpopAuthserverNonce,
383 dpopPrivateJwk,
384 )
385 if err != nil {
386 return nil, err
387 }
388
389 req, err := http.NewRequestWithContext(
390 ctx,
391 "POST",
392 authserverMeta.TokenEndpoint,
393 strings.NewReader(params.Encode()),
394 )
395 if err != nil {
396 return nil, err
397 }
398
399 req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
400 req.Header.Set("DPoP", dpopProof)
401
402 resp, err := c.h.Do(req)
403 if err != nil {
404 return nil, err
405 }
406 defer resp.Body.Close()
407
408 // TODO: use nonce if needed, same as in par
409
410 var rmap map[string]any
411 if err := json.NewDecoder(resp.Body).Decode(&rmap); err != nil {
412 return nil, err
413 }
414
415 return &TokenResponse{
416 DpopAuthserverNonce: dpopAuthserverNonce,
417 Resp: rmap,
418 }, nil
419}
420
421type RefreshTokenArgs struct {
422 AuthserverUrl string
423 RefreshToken string
424 DpopPrivateJwk string
425 DpopAuthserverNonce string
426}
427
428func (c *OauthClient) RefreshTokenRequest(
429 ctx context.Context,
430 args RefreshTokenArgs,
431 appUrl string,
432) (any, error) {
433 authserverMeta, err := c.FetchAuthServerMetadata(ctx, args.AuthserverUrl)
434 if err != nil {
435 return nil, err
436 }
437
438 clientAssertion, err := c.ClientAssertionJwt(args.AuthserverUrl)
439 if err != nil {
440 return nil, err
441 }
442
443 params := url.Values{
444 "client_id": {c.clientId},
445 "grant_type": {"refresh_token"},
446 "refresh_token": {args.RefreshToken},
447 "client_assertion_type": {"urn:ietf:params:oauth:client-assertion-type:jwt-bearer"},
448 "client_assertion": {clientAssertion},
449 }
450
451 dpopPrivateJwk, err := parsePrivateJwkFromString(args.DpopPrivateJwk)
452 if err != nil {
453 return nil, err
454 }
455
456 dpopProof, err := c.AuthServerDpopJwt(
457 "POST",
458 authserverMeta.TokenEndpoint,
459 args.DpopAuthserverNonce,
460 dpopPrivateJwk,
461 )
462 if err != nil {
463 return nil, err
464 }
465
466 req, err := http.NewRequestWithContext(
467 ctx,
468 "POST",
469 authserverMeta.TokenEndpoint,
470 strings.NewReader(params.Encode()),
471 )
472 if err != nil {
473 return nil, err
474 }
475
476 req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
477 req.Header.Set("DPoP", dpopProof)
478
479 resp, err := c.h.Do(req)
480 if err != nil {
481 return nil, err
482 }
483 defer resp.Body.Close()
484
485 // TODO: handle same thing as above...
486
487 if resp.StatusCode != 200 && resp.StatusCode != 201 {
488 b, _ := io.ReadAll(resp.Body)
489 return nil, fmt.Errorf("token refresh error: %s", string(b))
490 }
491
492 var rmap map[string]any
493 if err := json.NewDecoder(resp.Body).Decode(&rmap); err != nil {
494 return nil, err
495 }
496
497 return &TokenResponse{
498 DpopAuthserverNonce: args.DpopAuthserverNonce,
499 Resp: rmap,
500 }, nil
501}
502
503func generateToken(len int) (string, error) {
504 b := make([]byte, len)
505 if _, err := rand.Read(b); err != nil {
506 return "", err
507 }
508
509 return hex.EncodeToString(b), nil
510}
511
512func generateCodeChallenge(pkceVerifier string) string {
513 h := sha256.New()
514 h.Write([]byte(pkceVerifier))
515 hash := h.Sum(nil)
516 return base64.RawURLEncoding.EncodeToString(hash)
517}
518
519func parsePrivateJwkFromString(str string) (jwk.Key, error) {
520 return jwk.ParseKey([]byte(str))
521}