brokeyourbike/gin-gcp-api-gateway-middleware

package gcpapigatewaymw

import (
    "bytes"
    "encoding/base64"
    "encoding/json"
    "net/http"

    "github.com/gin-gonic/gin"
    "github.com/gin-gonic/gin/binding"
)

// gatewayUserInfoHeader is the header that contains the user info.
const gatewayUserInfoHeader = "X-Apigateway-Api-Userinfo"

// gatewayUserInfoCtx is a context key for the GatewayUserInfo.
const gatewayUserInfoCtx = "gatewayUserInfo"

type GatewayUserInfo struct {
    Sub   string `json:"sub" binding:"required"`
    Email string `json:"email" binding:"required,email"`
}

// Middleware creates a new GatewayCtx middleware.
func Middleware() gin.HandlerFunc {
    return func(ctx *gin.Context) {
        encodedUser := ctx.GetHeader(gatewayUserInfoHeader)
        if encodedUser == "" {
            ctx.AbortWithStatus(http.StatusForbidden)
            return
        }

        decodedBytes, err := base64.RawURLEncoding.DecodeString(encodedUser)
        if err != nil {
            ctx.AbortWithStatus(http.StatusForbidden)
            return
        }

        var userInfo GatewayUserInfo

        err = json.NewDecoder(bytes.NewReader(decodedBytes)).Decode(&userInfo)
        if err != nil {
            ctx.AbortWithStatus(http.StatusForbidden)
            return
        }

        err = binding.Validator.ValidateStruct(&userInfo)
        if err != nil {
            ctx.AbortWithStatus(http.StatusForbidden)
            return
        }

        ctx.Set(gatewayUserInfoCtx, userInfo)
        ctx.Next()
    }
}

// GetGatewayUserInfo returns the user info from the context.
func GetGatewayUserInfo(ctx *gin.Context) GatewayUserInfo {
    userInfo := ctx.MustGet(gatewayUserInfoCtx).(GatewayUserInfo)
    return userInfo
}

// GetGatewayUserID returns the user ID from the context.
func GetGatewayUserID(ctx *gin.Context) string {
    userInfo := GetGatewayUserInfo(ctx)
    return userInfo.Sub
}