62 lines
1.9 KiB
Go
62 lines
1.9 KiB
Go
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package identity
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import (
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"context"
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"encoding/json"
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"errors"
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"io"
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"net/http"
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"net/url"
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"time"
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)
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var ErrInvalidCode = errors.New("WeChat login code is invalid or expired")
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var errUnavailable = errors.New("WeChat identity verification is unavailable")
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// WeChat exchanges wx.login codes at the server only. Client is an optional
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// network dependency for tests; production uses a bounded HTTPS client.
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type WeChat struct {
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AppID string
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AppSecret string
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Client *http.Client
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}
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// Exchange returns an app-scoped openid after WeChat verifies the code. It never
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// returns session_key or wraps URL errors, since exchange URLs contain secrets.
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func (w *WeChat) Exchange(ctx context.Context, code string) (string, error) {
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if w.AppID == "" || w.AppSecret == "" {
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return "", errUnavailable
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}
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query := url.Values{"appid": {w.AppID}, "secret": {w.AppSecret}, "js_code": {code}, "grant_type": {"authorization_code"}}
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request, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://api.weixin.qq.com/sns/jscode2session?"+query.Encode(), nil)
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if err != nil {
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return "", errUnavailable
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}
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client := w.Client
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if client == nil {
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client = &http.Client{Timeout: 5 * time.Second, CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
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}
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response, err := client.Do(request)
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if err != nil {
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return "", errUnavailable
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}
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defer response.Body.Close()
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if response.StatusCode != 200 {
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return "", errUnavailable
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}
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var result struct {
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OpenID string `json:"openid"`
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ErrCode int `json:"errcode"`
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}
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if err = json.NewDecoder(io.LimitReader(response.Body, 16*1024)).Decode(&result); err != nil {
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return "", errUnavailable
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}
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if result.ErrCode == 40029 || result.ErrCode == 40163 {
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return "", ErrInvalidCode
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}
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if result.ErrCode != 0 || result.OpenID == "" {
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return "", errUnavailable
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}
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return w.AppID + ":" + result.OpenID, nil
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}
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