git.giacomolli.uk - onechat/blob - chatgpt.go

   1 package main
   2
   3 import (
   4         "bytes"
   5         "cmp"
   6         "context"
   7         "encoding/base64"
   8         "encoding/json"
   9         "errors"
  10         "fmt"
  11         "io"
  12         "net/http"
  13         "net/url"
  14         "os"
  15         "path/filepath"
  16         "strconv"
  17         "strings"
  18         "sync"
  19         "time"
  20 )
  21
  22 const (
  23         // chatgptIssuer is the OpenAI login service.
  24         chatgptIssuer = "https://auth.openai.com"
  25
  26         // chatgptClientID is the OAuth client ID of the Codex CLI. The ChatGPT
  27         // backend takes the tokens of this client only.
  28         chatgptClientID = "app_EMoamEEZ73f0CkXaXp7hrann"
  29
  30         // chatgptAuthClaim is the JWT claim that holds the ChatGPT account ID.
  31         chatgptAuthClaim = "https://api.openai.com/auth"
  32
  33         // chatgptRefreshMargin is how long before its expiry an access token is
  34         // refreshed.
  35         chatgptRefreshMargin = 60 * time.Second
  36
  37         // chatgptLoginTimeout is how long a device code login waits for the
  38         // user.
  39         chatgptLoginTimeout = 15 * time.Minute
  40
  41         // chatgptTokenFileName is the name of the token file in the data
  42         // directory.
  43         chatgptTokenFileName = "auth.json"
  44
  45         // chatgptDefaultPollInterval is the poll interval of a device code
  46         // login when the login service gives none.
  47         chatgptDefaultPollInterval = 5 * time.Second
  48 )
  49
  50 // errChatGPTLoginNeeded tells that no valid token is available, so the user
  51 // must run "onechat login".
  52 var errChatGPTLoginNeeded = errors.New(`login needed: run "onechat login"`)
  53
  54 // chatgptLogin runs "onechat login": the device code login into the token file
  55 // of the data directory. It holds the lock of the token file, so it does not
  56 // run while the daemon runs.
  57 func chatgptLogin(ctx context.Context, out io.Writer) (err error) {
  58         dir, err := dataDir()
  59         if err != nil {
  60                 return err
  61         }
  62
  63         tokens, err := lockTokens(dir)
  64         if err != nil {
  65                 return err
  66         }
  67
  68         defer func() {
  69                 err = errors.Join(err, tokens.Close())
  70         }()
  71
  72         return newChatGPTAuth(filepath.Join(dir, chatgptTokenFileName), chatgptIssuer).Login(ctx, out)
  73 }
  74
  75 // newChatGPTAuth returns the authorizer for the token file at path, with the
  76 // login service at issuer.
  77 func newChatGPTAuth(path, issuer string) *ChatGPTAuth {
  78         return &ChatGPTAuth{
  79                 path:   path,
  80                 issuer: issuer,
  81                 http:   &http.Client{},
  82         }
  83 }
  84
  85 // ChatGPTAuth authorizes model calls to the ChatGPT backend with the tokens in
  86 // the token file. The tokens belong to OneChat only. The Codex CLI rotates the
  87 // refresh token on each refresh, so two programs with one token file log each
  88 // other out.
  89 //
  90 // Before each call it reads the expiry from the access token. Within
  91 // chatgptRefreshMargin of the expiry it gets new tokens with the refresh token
  92 // and replaces the file atomically. A mutex lets one refresh run at a time, and
  93 // a call that waits for it uses the new tokens.
  94 type ChatGPTAuth struct {
  95         mutex  sync.Mutex
  96         path   string
  97         issuer string
  98         http   *http.Client
  99 }
 100
 101 // Authorize sets the access token and the account ID, after a refresh when the
 102 // token expires within chatgptRefreshMargin.
 103 func (a *ChatGPTAuth) Authorize(ctx context.Context, header http.Header) error {
 104         a.mutex.Lock()
 105         defer a.mutex.Unlock()
 106
 107         tokens, err := a.read()
 108         if err != nil {
 109                 return err
 110         }
 111
 112         expiry, found := chatgptTokenExpiry(tokens.AccessToken)
 113         if !found || !time.Now().Before(expiry.Add(-chatgptRefreshMargin)) {
 114                 tokens, err = a.refresh(ctx, tokens)
 115                 if err != nil {
 116                         return err
 117                 }
 118         }
 119
 120         header.Set("Authorization", "Bearer "+tokens.AccessToken)
 121         header.Set("ChatGPT-Account-Id", tokens.AccountID)
 122
 123         return nil
 124 }
 125
 126 // Login runs the device code login. It writes the link and the code for the
 127 // user to out, waits until the user approves the code, and writes the tokens
 128 // to the token file.
 129 func (a *ChatGPTAuth) Login(ctx context.Context, out io.Writer) error {
 130         a.mutex.Lock()
 131         defer a.mutex.Unlock()
 132
 133         var code ChatGPTDeviceCode
 134
 135         err := a.postJSON(ctx, "/api/accounts/deviceauth/usercode", map[string]string{
 136                 "client_id": chatgptClientID,
 137         }, &code)
 138         if err != nil {
 139                 return fmt.Errorf("request device code (device code login must be allowed in the ChatGPT security settings): %w", err)
 140         }
 141
 142         userCode := cmp.Or(code.UserCode, code.UserCodeAlt)
 143         if code.DeviceAuthID == "" || userCode == "" {
 144                 return errors.New("device code response has no device ID or user code")
 145         }
 146
 147         _, err = fmt.Fprintf(out, "Open %s/codex/device on any device and enter this code:\n\n    %s\n\nWaiting for the approval...\n", a.issuer, userCode)
 148         if err != nil {
 149                 return fmt.Errorf("write device code: %w", err)
 150         }
 151
 152         grant, err := a.poll(ctx, code.DeviceAuthID, userCode, chatgptPollInterval(code.Interval))
 153         if err != nil {
 154                 return err
 155         }
 156
 157         tokens, err := a.exchange(ctx, grant)
 158         if err != nil {
 159                 return err
 160         }
 161
 162         err = a.write(tokens)
 163         if err != nil {
 164                 return err
 165         }
 166
 167         _, err = fmt.Fprintln(out, "Logged in.")
 168         if err != nil {
 169                 return fmt.Errorf("write login result: %w", err)
 170         }
 171
 172         return nil
 173 }
 174
 175 // read reads the token file.
 176 func (a *ChatGPTAuth) read() (ChatGPTTokenFile, error) {
 177         data, err := os.ReadFile(a.path)
 178         if errors.Is(err, os.ErrNotExist) {
 179                 return ChatGPTTokenFile{}, errChatGPTLoginNeeded
 180         }
 181
 182         if err != nil {
 183                 return ChatGPTTokenFile{}, fmt.Errorf("read token file: %w", err)
 184         }
 185
 186         var tokens ChatGPTTokenFile
 187
 188         err = json.Unmarshal(data, &tokens)
 189         if err == nil && (tokens.AccessToken == "" || tokens.RefreshToken == "" || tokens.AccountID == "") {
 190                 err = errors.New("a token or the account ID is missing")
 191         }
 192
 193         if err != nil {
 194                 return ChatGPTTokenFile{}, fmt.Errorf("token file: %w: %w", err, errChatGPTLoginNeeded)
 195         }
 196
 197         return tokens, nil
 198 }
 199
 200 // refresh gets new tokens with the refresh token and replaces the token file.
 201 // It keeps the old refresh token and ID token when the answer has none.
 202 func (a *ChatGPTAuth) refresh(ctx context.Context, tokens ChatGPTTokenFile) (ChatGPTTokenFile, error) {
 203         var response ChatGPTTokenResponse
 204
 205         err := a.postJSON(ctx, "/oauth/token", map[string]string{
 206                 "client_id":     chatgptClientID,
 207                 "grant_type":    "refresh_token",
 208                 "refresh_token": tokens.RefreshToken,
 209                 "scope":         "openid profile email",
 210         }, &response)
 211         if err == nil && response.AccessToken == "" {
 212                 err = errors.New("refresh response has no access token")
 213         }
 214
 215         if err != nil {
 216                 return ChatGPTTokenFile{}, fmt.Errorf("refresh tokens: %w: %w", err, errChatGPTLoginNeeded)
 217         }
 218
 219         tokens.AccessToken = response.AccessToken
 220         tokens.RefreshToken = cmp.Or(response.RefreshToken, tokens.RefreshToken)
 221         tokens.IDToken = cmp.Or(response.IDToken, tokens.IDToken)
 222         tokens.AccountID = cmp.Or(chatgptAccountID(tokens.AccessToken), chatgptAccountID(tokens.IDToken), tokens.AccountID)
 223
 224         err = a.write(tokens)
 225         if err != nil {
 226                 return ChatGPTTokenFile{}, err
 227         }
 228
 229         return tokens, nil
 230 }
 231
 232 // postJSON posts body as JSON to the path of the login service and decodes the
 233 // answer into result.
 234 func (a *ChatGPTAuth) postJSON(ctx context.Context, path string, body, result any) error {
 235         data, err := json.Marshal(body)
 236         if err != nil {
 237                 return fmt.Errorf("encode request: %w", err)
 238         }
 239
 240         _, err = a.post(ctx, path, "application/json", data, result)
 241
 242         return err
 243 }
 244
 245 // poll asks for the grant of the device code until the user approves it or the
 246 // login times out.
 247 func (a *ChatGPTAuth) poll(ctx context.Context, deviceID, userCode string, interval time.Duration) (ChatGPTDeviceGrant, error) {
 248         ctx, cancel := context.WithTimeout(ctx, chatgptLoginTimeout)
 249         defer cancel()
 250
 251         body, err := json.Marshal(map[string]string{
 252                 "device_auth_id": deviceID,
 253                 "user_code":      userCode,
 254         })
 255         if err != nil {
 256                 return ChatGPTDeviceGrant{}, fmt.Errorf("encode poll request: %w", err)
 257         }
 258
 259         for {
 260                 var grant ChatGPTDeviceGrant
 261
 262                 status, err := a.post(ctx, "/api/accounts/deviceauth/token", "application/json", body, &grant)
 263                 if err == nil && (grant.AuthorizationCode == "" || grant.CodeVerifier == "") {
 264                         err = errors.New("device grant has no authorization code or code verifier")
 265                 }
 266
 267                 if err == nil {
 268                         return grant, nil
 269                 }
 270
 271                 if status != http.StatusForbidden && status != http.StatusNotFound {
 272                         return ChatGPTDeviceGrant{}, fmt.Errorf("poll device code: %w", err)
 273                 }
 274
 275                 timer := time.NewTimer(interval)
 276                 select {
 277                 case <-ctx.Done():
 278                         timer.Stop()
 279
 280                         return ChatGPTDeviceGrant{}, fmt.Errorf("wait for approval: %w", ctx.Err())
 281                 case <-timer.C:
 282                 }
 283         }
 284 }
 285
 286 // exchange trades the grant of the device code for tokens.
 287 func (a *ChatGPTAuth) exchange(ctx context.Context, grant ChatGPTDeviceGrant) (ChatGPTTokenFile, error) {
 288         form := url.Values{
 289                 "grant_type":    {"authorization_code"},
 290                 "code":          {grant.AuthorizationCode},
 291                 "redirect_uri":  {a.issuer + "/deviceauth/callback"},
 292                 "client_id":     {chatgptClientID},
 293                 "code_verifier": {grant.CodeVerifier},
 294         }
 295
 296         var response ChatGPTTokenResponse
 297
 298         _, err := a.post(ctx, "/oauth/token", "application/x-www-form-urlencoded", []byte(form.Encode()), &response)
 299         if err != nil {
 300                 return ChatGPTTokenFile{}, fmt.Errorf("exchange code for tokens: %w", err)
 301         }
 302
 303         if response.AccessToken == "" || response.RefreshToken == "" || response.IDToken == "" {
 304                 return ChatGPTTokenFile{}, errors.New("token response has no access, refresh, or ID token")
 305         }
 306
 307         tokens := ChatGPTTokenFile{
 308                 AccessToken:  response.AccessToken,
 309                 RefreshToken: response.RefreshToken,
 310                 IDToken:      response.IDToken,
 311         }
 312
 313         tokens.AccountID = cmp.Or(chatgptAccountID(tokens.AccessToken), chatgptAccountID(tokens.IDToken))
 314         if tokens.AccountID == "" {
 315                 return ChatGPTTokenFile{}, errors.New("tokens have no ChatGPT account ID")
 316         }
 317
 318         return tokens, nil
 319 }
 320
 321 // write replaces the token file atomically. The file has mode 0600.
 322 func (a *ChatGPTAuth) write(tokens ChatGPTTokenFile) error {
 323         data, err := json.Marshal(tokens)
 324         if err != nil {
 325                 return fmt.Errorf("encode tokens: %w", err)
 326         }
 327
 328         err = writeFileAtomic(a.path, append(data, '\n'))
 329         if err != nil {
 330                 return fmt.Errorf("write token file: %w", err)
 331         }
 332
 333         return nil
 334 }
 335
 336 // post posts body to the path of the login service and decodes a 200 answer
 337 // into result. It returns the HTTP status, or 0 when no answer came. The error
 338 // holds the status, but not the body, which can hold a token.
 339 func (a *ChatGPTAuth) post(ctx context.Context, path, contentType string, body []byte, result any) (status int, err error) {
 340         request, err := http.NewRequestWithContext(ctx, http.MethodPost, a.issuer+path, bytes.NewReader(body))
 341         if err != nil {
 342                 return 0, fmt.Errorf("create request: %w", err)
 343         }
 344
 345         request.Header.Set("Content-Type", contentType)
 346
 347         response, err := a.http.Do(request)
 348         if err != nil {
 349                 return 0, fmt.Errorf("send request: %w", err)
 350         }
 351
 352         defer func() {
 353                 err = errors.Join(err, response.Body.Close())
 354         }()
 355
 356         if response.StatusCode != http.StatusOK {
 357                 return response.StatusCode, fmt.Errorf("HTTP %d", response.StatusCode)
 358         }
 359
 360         err = json.NewDecoder(response.Body).Decode(result)
 361         if err != nil {
 362                 return response.StatusCode, fmt.Errorf("decode answer: %w", err)
 363         }
 364
 365         return response.StatusCode, nil
 366 }
 367
 368 // ChatGPTDeviceCode is the answer of the user code endpoint. The interval is a
 369 // number or a string of seconds.
 370 type ChatGPTDeviceCode struct {
 371         DeviceAuthID string          `json:"device_auth_id"`
 372         UserCode     string          `json:"user_code"`
 373         UserCodeAlt  string          `json:"usercode"`
 374         Interval     json.RawMessage `json:"interval"`
 375 }
 376
 377 // ChatGPTTokenFile is the content of the token file.
 378 type ChatGPTTokenFile struct {
 379         AccessToken  string `json:"access_token"`
 380         RefreshToken string `json:"refresh_token"`
 381         IDToken      string `json:"id_token"`
 382         AccountID    string `json:"account_id"`
 383 }
 384
 385 // ChatGPTTokenResponse is the answer of the token endpoint.
 386 type ChatGPTTokenResponse struct {
 387         AccessToken  string `json:"access_token"`
 388         RefreshToken string `json:"refresh_token"`
 389         IDToken      string `json:"id_token"`
 390 }
 391
 392 // ChatGPTDeviceGrant is the answer of the device token endpoint after the user
 393 // approves the code.
 394 type ChatGPTDeviceGrant struct {
 395         AuthorizationCode string `json:"authorization_code"`
 396         CodeVerifier      string `json:"code_verifier"`
 397 }
 398
 399 // chatgptTokenExpiry returns the expiry of a JWT from its exp claim.
 400 func chatgptTokenExpiry(token string) (time.Time, bool) {
 401         var claims struct {
 402                 Exp *float64 `json:"exp"`
 403         }
 404
 405         if !chatgptDecodeClaims(token, &claims) || claims.Exp == nil {
 406                 return time.Time{}, false
 407         }
 408
 409         return time.Unix(int64(*claims.Exp), 0), true
 410 }
 411
 412 // chatgptPollInterval returns the poll interval of a device code, given in
 413 // seconds as a number or a string.
 414 func chatgptPollInterval(raw json.RawMessage) time.Duration {
 415         seconds, err := strconv.ParseFloat(strings.Trim(string(raw), `"`), 64)
 416         if err != nil || seconds < 0 {
 417                 return chatgptDefaultPollInterval
 418         }
 419
 420         return time.Duration(seconds * float64(time.Second))
 421 }
 422
 423 // chatgptAccountID returns the ChatGPT account ID of a JWT, or "" when it has
 424 // none.
 425 func chatgptAccountID(token string) string {
 426         var claims map[string]json.RawMessage
 427
 428         if !chatgptDecodeClaims(token, &claims) {
 429                 return ""
 430         }
 431
 432         var auth struct {
 433                 AccountID string `json:"chatgpt_account_id"`
 434         }
 435
 436         err := json.Unmarshal(claims[chatgptAuthClaim], &auth)
 437         if err != nil {
 438                 return ""
 439         }
 440
 441         return auth.AccountID
 442 }
 443
 444 // chatgptDecodeClaims decodes the payload of a JWT into claims, without a check
 445 // of the signature. The token comes from the login service over HTTPS, and the
 446 // client reads only the expiry and the account ID from it.
 447 func chatgptDecodeClaims(token string, claims any) bool {
 448         parts := strings.Split(token, ".")
 449         if len(parts) != 3 {
 450                 return false
 451         }
 452
 453         payload, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(parts[1], "="))
 454         if err != nil {
 455                 return false
 456         }
 457
 458         return json.Unmarshal(payload, claims) == nil
 459 }