func()

in oauthproxy.go [524:583]
53 lines of code
12 McCabe index (conditional complexity)

func (p *OAuthProxy) OAuthCallback(rw http.ResponseWriter, req *http.Request) {
	remoteAddr := getRemoteAddr(req)

	// finish the oauth cycle
	err := req.ParseForm()
	if err != nil {
		p.ErrorPage(rw, 500, "Internal Error", err.Error())
		return
	}
	errorString := req.Form.Get("error")
	if errorString != "" {
		p.ErrorPage(rw, 403, "Permission Denied", errorString)
		return
	}

	session, err := p.redeemCode(req.Host, req.Form.Get("code"))
	if err != nil {
		log.Printf("%s error redeeming code %s", remoteAddr, err)
		p.ErrorPage(rw, 500, "Internal Error", "Internal Error")
		return
	}

	s := strings.SplitN(req.Form.Get("state"), ":", 2)
	if len(s) != 2 {
		p.ErrorPage(rw, 500, "Internal Error", "Invalid State")
		return
	}
	nonce := s[0]
	redirect := s[1]
	c, err := req.Cookie(p.CSRFCookieName)
	if err != nil {
		p.ErrorPage(rw, 403, "Permission Denied", err.Error())
		return
	}
	p.ClearCSRFCookie(rw, req)
	if c.Value != nonce {
		log.Printf("%s csrf token mismatch, potential attack", remoteAddr)
		p.ErrorPage(rw, 403, "Permission Denied", "csrf failed")
		return
	}

	if !strings.HasPrefix(redirect, "/") || strings.HasPrefix(redirect, "//") {
		redirect = "/"
	}

	// set cookie, or deny
	if p.Validator(session.Email) && p.provider.ValidateGroup(session.Email) {
		log.Printf("%s authentication complete %s", remoteAddr, session)
		err := p.SaveSession(rw, req, session)
		if err != nil {
			log.Printf("%s %s", remoteAddr, err)
			p.ErrorPage(rw, 500, "Internal Error", "Internal Error")
			return
		}
		http.Redirect(rw, req, redirect, 302)
	} else {
		log.Printf("%s Permission Denied: %q is unauthorized", remoteAddr, session.Email)
		p.ErrorPage(rw, 403, "Permission Denied", "Invalid Account")
	}
}