从访问令牌获取Google登录个人资料信息-Golang

Question

I have the following JavaScript code

auth2.grantOfflineAccess().then(function(codeData) {
    if (!codeData) {
        alert("Something went wrong");
        return;
    }

    $.post("/do/signIn/google", codeData, function() { ... });
});

I am sending the code for a Google sign in to my golang web app. I successfully got an access token from POST https://www.googleapis.com/oauth2/v4/token.

My issue is, I am unable to get the user's profile information (such as email, display name etc.)

I've tried sending a request to GET https://www.googleapis.com/auth/userinfo.profile?access_token=xxx and I receive an empty response (blank body).

Answer 1

You must decode the Google ID token returned by POST https://www.googleapis.com/oauth2/v4/token to convert it into a Google+ ID then you may use GET https://www.googleapis.com/plus/v1/people/[gplusID]?access_token=[accessToken]

Using Go, you can decode the google ID token using the following function. Normally, it is critical that you validate an ID token before you use it, but since you are communicating directly with Google over an intermediary-free HTTPS channel and using your Client Secret to authenticate yourself to Google, you can be confident that the token you receive really comes from Google and is valid. If your server passes the ID token to other components of your app, it is extremely important that the other components validate the token before using it.

Using Go, you can decode the ID token with the following function.

func decodeGoogleIDToken(idToken string) (gplusID string, err error) {
    var set struct {
        Sub string
    }
    if idToken != "" {
        // Check that the padding is correct for a base64decode
        parts := strings.Split(idToken, ".")
        if len(parts) < 2 {
            return "", fmt.Errorf("Malformed ID token")
        }
        // Decode the ID token
        s := parts[1]
        switch len(s) % 4 {
        case 2:
            s += "=="
        case 3:
            s += "="
        }

        b, err := base64.URLEncoding.DecodeString(s)
        if err != nil {
            return "", fmt.Errorf("Malformed ID token: %v", err)
        }
        err = json.Unmarshal(b, &set)
        if err != nil {
            return "", fmt.Errorf("Malformed ID token: %v", err)
        }
    }
    return set.Sub, nil
}

Check out an example here at https://play.golang.org/p/M7sYmE2ztx