craban/server/api/auth.go

package api

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strconv"
	"strings"

	"git.ctrlz.es/mgdelacroix/craban/model"

	"github.com/dgrijalva/jwt-go"
	"github.com/rs/zerolog/log"
)

const userContextKey = "user"

func (a *API) Login(w http.ResponseWriter, r *http.Request) {
	body := ParseBody(r)
	username := body.String("username")
	password := body.String("password")

	token, err := a.App.Login(username, password)
	if err != nil {
		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
		return
	}

	if token == "" {
		http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
		return
	}

	_, _ = w.Write([]byte(token))
}

func (a *API) getUserFromToken(tokenStr string) (*model.User, error) {
	token, err := jwt.Parse(tokenStr, func(token *jwt.Token) (interface{}, error) {
		// Validate the alg is what you expect:
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
		}

		return []byte(*a.App.Config.Secret), nil
	})
	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
		userIDClaim, ok := claims["userID"].(string)
		if !ok {
			return nil, errors.New("userID claim is not set")
		}
		userID, err := strconv.Atoi(userIDClaim)
		if err != nil {
			return nil, err
		}

		return a.App.GetUserByID(userID)
	} else {
		return nil, errors.New("Malformed claims")
	}
}

func (a *API) Secured(fn func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		tokenStr := r.Header.Get("Authorization")
		if tokenStr == "" {
			http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
			return
		}
		tokenStr = strings.TrimPrefix(tokenStr, "Bearer ")

		user, err := a.getUserFromToken(tokenStr)
		if err != nil {
			log.Debug().Err(err).Str("token", tokenStr).Msg("cannot get user from token")
			http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
			return
		}

		// get user
		ctx := context.WithValue(r.Context(), userContextKey, user)
		fn(w, r.Clone(ctx))
	}
}

func UserFromRequest(r *http.Request) (*model.User, bool) {
	user, ok := r.Context().Value(userContextKey).(*model.User)
	return user, ok
}