CSRF

Cross-site request forgery (CSRF) is a method of attack that holds a user hostage to perform an unintended action on a currently logged-in Web application.

Hertz provides CSRF middleware to help you prevent cross-site request forgery attacks.

Install

go get github.com/hertz-contrib/csrf

Example

package main

import (
	"context"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"
)

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("secret"))
	h.Use(sessions.New("csrf-session", store))
	h.Use(csrf.New())

	h.GET("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, csrf.GetToken(ctx))
	})

	h.POST("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "CSRF token is valid")
	})

	h.Spin()
}

Config

Option	Default	Description
Secret	“csrfSecret”	Secret used to generate token.
IgnoreMethods	“GET”, “HEAD”, “OPTIONS”, “TRACE”	Ignored methods will be considered no protection required.
Next	nil	Next defines a function to skip this middleware when returned true.
KeyLookup	“header:X-CSRF-TOKEN”	KeyLookup is a string in the form of “:” that is used to create an Extractor that extracts the token from the request.
ErrorFunc	func(ctx context.Context, c *app.RequestContext) { panic(c.Errors.Last()) }	ErrorFunc is executed when an error is returned from app.HandlerFunc.
Extractor	Default will create an Extractor based on KeyLookup.	Extractor returns the csrf token. If set this will be used in place of an Extractor based on KeyLookup.

WithSecret

The csrf middleware provides WithSecret to help users set a custom secret key for issuing token, which is csrfSecret by default.

Function Signature:

func WithSecret(secret string) Option

Default：csrfSecret

Sample Code:

package main

import (
	"context"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"
)

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("store"))
	h.Use(sessions.New("csrf-session", store))
	h.Use(csrf.New(csrf.WithSecret("your_secret")))

	h.GET("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, csrf.GetToken(ctx))
	})
	h.POST("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "CSRF token is valid")
	})

	h.Spin()
}

WithIgnoredMethods

The csrf middleware provides WithIgnoredMethods to help users set up custom methods that do not need to be protected, the defaults are GET, HEAD, OPTIONS and TRACE.

Function Signature:

func WithIgnoredMethods(methods []string) Option

Default: {"GET", "HEAD", "OPTIONS", "TRACE"}

Sample Code:

package main

import (
	"context"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"
)

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("secret"))
	h.Use(sessions.New("session", store))
	h.Use(csrf.New(csrf.WithIgnoredMethods([]string{"GET", "HEAD", "TRACE"})))

	h.GET("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, csrf.GetToken(ctx))
	})

	h.OPTIONS("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "success")
	})
	h.Spin()
}

WithErrorFunc

The csrf middleware provides WithErrorFunc to facilitate user-defined error handling logic.

Function Signature:

func WithErrorFunc(f app.HandlerFunc) Option

Default:

func(ctx context.Context, c *app.RequestContext) { panic(c.Errors.Last()) }

Sample Code:

package main

import (
	"context"
	"fmt"
	"net/http"
	
	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"

)

func myErrFunc(c context.Context, ctx *app.RequestContext) {
    if ctx.Errors.Last() == nil {
        err := fmt.Errorf("myErrFunc called when no error occurs")
        ctx.String(400, err.Error())
        ctx.Abort()
    }
	ctx.AbortWithMsg(ctx.Errors.Last().Error(), http.StatusBadRequest)
}

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("store"))
	h.Use(sessions.New("csrf-session", store))
	h.Use(csrf.New(csrf.WithErrorFunc(myErrFunc)))

	h.GET("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, csrf.GetToken(ctx))
	})
	h.POST("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "CSRF token is valid")
	})

	h.Spin()
}

WithKeyLookUp

The csrf middleware provides WithKeyLookUp to help users set keyLookup.

csrf is used to extract token from source (supported sources include header, param, query, form).

The format is <source>:<key> and the default value is :header:X-CSRF-TOKEN.

Function Signature:

func WithKeyLookUp(lookup string) Option

Default: header:X-CSRF-TOKEN"

Sample Code:

package main

import (
	"context"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"
)

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("store"))
	h.Use(sessions.New("csrf-session", store))
	h.Use(csrf.New(csrf.WithKeyLookUp("form:csrf")))

	h.GET("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, csrf.GetToken(ctx))
	})
	h.POST("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "CSRF token is valid")
	})

	h.Spin()
}

WithNext

The csrf middleware provides WithNext to facilitate user-defined settings to skip the csrf middleware under certain conditions.

Function Signature:

func WithNext(f CsrfNextHandler) Option

Default:nil

Sample Code:

package main

import (
	"context"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"
)

func isPostMethod(_ context.Context, ctx *app.RequestContext) bool {
	if string(ctx.Method()) == "POST" {
		return true
	} else {
		return false
	}
}

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("store"))
	h.Use(sessions.New("csrf-session", store))

	//  skip csrf middleware when request method is post
	h.Use(csrf.New(csrf.WithNext(isPostMethod)))

	h.POST("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "success even no csrf-token in header")
	})
	h.Spin()
}

WithExtractor

The csrf middleware provides WithExtractor for the user to get the csrf-token from the request via a custom method.

Function Signature:

func WithExtractor(f CsrfExtractorHandler) Option

Default:

func CsrfFromHeader(param string) func(ctx context.Context, c *app.RequestContext) (string, error) {
	return func(ctx context.Context, c *app.RequestContext) (string, error) {
		token := c.GetHeader(param)
		if string(token) == "" {
			return "", errMissingHeader
		}
		return string(token), nil
	}
}

Sample Code:

package main

import (
	"context"
	"errors"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/app/server"
	"github.com/hertz-contrib/csrf"
	"github.com/hertz-contrib/sessions"
	"github.com/hertz-contrib/sessions/cookie"
)

func myExtractor(c context.Context, ctx *app.RequestContext) (string, error) {
	token := ctx.FormValue("csrf-token")
	if token == nil {
		return "", errors.New("missing token in form-data")
	}
	return string(token), nil
}

func main() {
	h := server.Default()

	store := cookie.NewStore([]byte("secret"))
	h.Use(sessions.New("csrf-session", store))
	h.Use(csrf.New(csrf.WithExtractor(myExtractor)))

	h.GET("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, csrf.GetToken(ctx))
	})
	h.POST("/protected", func(c context.Context, ctx *app.RequestContext) {
		ctx.String(200, "CSRF token is valid")
	})

	h.Spin()
}

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Last modified July 30, 2023 : fix type error (#735) (50c91bf)