option handler

added in middleware: Cors and Helmet

README.md

@@ -27,7 +27,7 @@ func main() {
 	r.Use(middleware1, middleware2)
 
 	// let's add a route
-	r.Get("/hello", func(w http.ResponseWriter, r *http.Request) {
+	r.GET("/hello", func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("i am route /hello"))
 	})
 	// r.Post(pattern string, h http.HandlerFunc)
@@ -37,7 +37,7 @@ func main() {
 	// you can inline middleware(s) to a route
 	r.
 		With(mwInline).
-		Get("/hello-2", func(w http.ResponseWriter, r *http.Request) {
+		GET("/hello-2", func(w http.ResponseWriter, r *http.Request) {
 			w.Write([]byte("i am route /hello-2 with my own middleware"))
 		})
 
@@ -64,13 +64,13 @@ func main() {
 	// create a group of few routes with their own middlewares
 	r.Group(func(grp *mux.Router) {
 		grp.Use(mwGroup)
-		grp.Get("/group", func(w http.ResponseWriter, r *http.Request) {
+		grp.GET("/group", func(w http.ResponseWriter, r *http.Request) {
 			w.Write([]byte("i am route /group"))
 		})
 	})
 
 	// catches all
-	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
+	r.GET("/", func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("hello there"))
 	})
 

example/main.go

@@ -5,11 +5,16 @@ import (
 	"net/http"
 
 	"gitserver.in/patialtech/mux"
+	"gitserver.in/patialtech/mux/middleware"
 )
 
 func main() {
 	// create a new router
 	r := mux.NewRouter()
+	r.Use(middleware.CORS(middleware.CORSOption{
+		AllowedOrigins: []string{"*"},
+		MaxAge:         60,
+	}))
 
 	// you can use any middleware that is: "func(http.Handler) http.Handler"
 	// so you can use any of it
@@ -20,7 +25,7 @@ func main() {
 	r.Use(middleware1, middleware2)
 
 	// let's add a route
-	r.Get("/hello", func(w http.ResponseWriter, r *http.Request) {
+	r.GET("/hello", func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("i am route /hello"))
 	})
 	// r.Post(pattern string, h http.HandlerFunc)
@@ -30,13 +35,13 @@ func main() {
 	// you can inline middleware(s) to a route
 	r.
 		With(mwInline).
-		Get("/hello-2", func(w http.ResponseWriter, r *http.Request) {
+		GET("/hello-2", func(w http.ResponseWriter, r *http.Request) {
 			w.Write([]byte("i am route /hello-2 with my own middleware"))
 		})
 
 	// define a resource
 	r.Resource("/photos", func(resource *mux.Resource) {
-		// rails style resource routes
+		// Rails style resource routes
 		// GET       /photos
 		// GET       /photos/new
 		// POST      /photos
@@ -57,13 +62,13 @@ func main() {
 	// create a group of few routes with their own middlewares
 	r.Group(func(grp *mux.Router) {
 		grp.Use(mwGroup)
-		grp.Get("/group", func(w http.ResponseWriter, r *http.Request) {
+		grp.GET("/group", func(w http.ResponseWriter, r *http.Request) {
 			w.Write([]byte("i am route /group"))
 		})
 	})
 
 	// catches all
-	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
+	r.GET("/", func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("hello there"))
 	})
 

middleware/cors.go

@@ -0,0 +1,322 @@
+package middleware
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+// copied from https://github.com/gorilla/handlers/blob/main/cors.go
+// with some editing to fit in
+//
+
+// CORSOption represents a functional option for configuring the CORS middleware.
+type CORSOption struct {
+	// AllowedOrigins list, including "*" will allow all
+	AllowedOrigins []string
+
+	// AllowedHeaders are a list of headers clients are allowed to use with.
+	// default: []string{"Accept", "Accept-Language", "Content-Language", "Origin"}
+	AllowedHeaders []string
+
+	// AllowedMethods are a list of methods clients are allowed to use.
+	//
+	// default: []string{"HEAD", "GET", "POST"}
+	AllowedMethods []string
+
+	ExposedHeaders []string
+	// MaxAge in seconds, max allowed value is 600
+	MaxAge           uint
+	AllowCredentials bool
+}
+
+type cors struct {
+	h                      http.Handler
+	allowedHeaders         []string
+	allowedMethods         []string
+	allowedOrigins         []string
+	allowedOriginValidator OriginValidator
+	exposedHeaders         []string
+	maxAge                 uint
+	ignoreOptions          bool
+	allowCredentials       bool
+	optionStatusCode       int
+}
+
+// OriginValidator takes an origin string and returns whether that origin is allowed.
+type OriginValidator func(string) bool
+
+var (
+	defaultCorsOptionStatusCode = http.StatusOK
+	defaultCorsMethods          = []string{http.MethodHead, http.MethodGet, http.MethodPost}
+	defaultCorsHeaders          = []string{"Accept", "Accept-Language", "Content-Type", "Content-Language", "Origin"}
+	// (WebKit/Safari v9 sends the Origin header by default in AJAX requests).
+)
+
+const (
+	corsOptionMethod           string = http.MethodOptions
+	corsAllowOriginHeader      string = "Access-Control-Allow-Origin"
+	corsExposeHeadersHeader    string = "Access-Control-Expose-Headers"
+	corsMaxAgeHeader           string = "Access-Control-Max-Age"
+	corsAllowMethodsHeader     string = "Access-Control-Allow-Methods"
+	corsAllowHeadersHeader     string = "Access-Control-Allow-Headers"
+	corsAllowCredentialsHeader string = "Access-Control-Allow-Credentials"
+	corsRequestMethodHeader    string = "Access-Control-Request-Method"
+	corsRequestHeadersHeader   string = "Access-Control-Request-Headers"
+	corsOriginHeader           string = "Origin"
+	corsVaryHeader             string = "Vary"
+	corsOriginMatchAll         string = "*"
+)
+
+// CORS provides Cross-Origin Resource Sharing middleware.
+// Example:
+//
+//	import (
+//	    "net/http"
+//	    "gitserver.in/patialtech/mux/middleware"
+//	    "gitserver.in/patialtech/mux"
+//	)
+//
+//	func main() {
+//		r := mux.NewRouter()
+//		r.Use(middleware.CORS(middleware.CORSOption{
+//			AllowedOrigins: []string{"*"},
+//			MaxAge:         60,
+//		}))
+//
+//		r.Get("/", func(w http.ResponseWriter, r *http.Request) {
+//			w.Write([]byte("hello there"))
+//		})
+//
+//		r.Serve(func(srv *http.Server) error {
+//			srv.Addr = ":3001"
+//			slog.Info("listening on http://localhost" + srv.Addr)
+//			return srv.ListenAndServe()
+//		})
+//	}
+func CORS(opts CORSOption) func(http.Handler) http.Handler {
+	return func(h http.Handler) http.Handler {
+		ch := &cors{
+			h:                h,
+			allowedMethods:   defaultCorsMethods,
+			allowedHeaders:   defaultCorsHeaders,
+			allowedOrigins:   []string{},
+			optionStatusCode: defaultCorsOptionStatusCode,
+		}
+
+		ch.setAllowedOrigins(opts.AllowedOrigins)
+		ch.setAllowedHeaders(opts.AllowedHeaders)
+		ch.setAllowedMethods(opts.AllowedMethods)
+		ch.setExposedHeaders(opts.ExposedHeaders)
+		ch.setMaxAge(opts.MaxAge)
+		ch.maxAge = opts.MaxAge
+		ch.allowCredentials = opts.AllowCredentials
+
+		return ch
+	}
+}
+
+func (ch *cors) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	origin := r.Header.Get(corsOriginHeader)
+	if !ch.isOriginAllowed(origin) {
+		if r.Method != corsOptionMethod || ch.ignoreOptions {
+			ch.h.ServeHTTP(w, r)
+		}
+
+		return
+	}
+
+	if r.Method == corsOptionMethod {
+		if ch.ignoreOptions {
+			ch.h.ServeHTTP(w, r)
+			return
+		}
+
+		if _, ok := r.Header[corsRequestMethodHeader]; !ok {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+
+		method := r.Header.Get(corsRequestMethodHeader)
+		if !ch.isMatch(method, ch.allowedMethods) {
+			w.WriteHeader(http.StatusMethodNotAllowed)
+			return
+		}
+
+		requestHeaders := strings.Split(r.Header.Get(corsRequestHeadersHeader), ",")
+		var allowedHeaders []string
+		for _, v := range requestHeaders {
+			canonicalHeader := http.CanonicalHeaderKey(strings.TrimSpace(v))
+			if canonicalHeader == "" || ch.isMatch(canonicalHeader, defaultCorsHeaders) {
+				continue
+			}
+
+			if !ch.isMatch(canonicalHeader, ch.allowedHeaders) {
+				w.WriteHeader(http.StatusForbidden)
+				return
+			}
+
+			allowedHeaders = append(allowedHeaders, canonicalHeader)
+		}
+
+		if len(allowedHeaders) > 0 {
+			w.Header().Set(corsAllowHeadersHeader, strings.Join(allowedHeaders, ","))
+		}
+
+		if ch.maxAge > 0 {
+			w.Header().Set(corsMaxAgeHeader, strconv.Itoa(int(ch.maxAge)))
+		}
+
+		if !ch.isMatch(method, defaultCorsMethods) {
+			w.Header().Set(corsAllowMethodsHeader, method)
+		}
+	} else if len(ch.exposedHeaders) > 0 {
+		w.Header().Set(corsExposeHeadersHeader, strings.Join(ch.exposedHeaders, ","))
+	}
+
+	if ch.allowCredentials {
+		w.Header().Set(corsAllowCredentialsHeader, "true")
+	}
+
+	if len(ch.allowedOrigins) > 1 {
+		w.Header().Set(corsVaryHeader, corsOriginHeader)
+	}
+
+	returnOrigin := origin
+	if ch.allowedOriginValidator == nil && len(ch.allowedOrigins) == 0 {
+		returnOrigin = "*"
+	} else {
+		for _, o := range ch.allowedOrigins {
+			// A configuration of * is different from explicitly setting an allowed
+			// origin. Returning arbitrary origin headers in an access control allow
+			// origin header is unsafe and is not required by any use case.
+			if o == corsOriginMatchAll {
+				returnOrigin = "*"
+				break
+			}
+		}
+	}
+	w.Header().Set(corsAllowOriginHeader, returnOrigin)
+
+	if r.Method == corsOptionMethod {
+		w.WriteHeader(ch.optionStatusCode)
+		return
+	}
+	ch.h.ServeHTTP(w, r)
+}
+
+// AllowedOrigins sets the allowed origins for CORS requests, as used in the
+// 'Allow-Access-Control-Origin' HTTP header.
+// Note: Passing in a []string{"*"} will allow any domain.
+func (ch *cors) setAllowedOrigins(origins []string) {
+	// look for "*"
+	for _, v := range origins {
+		if v == corsOriginMatchAll {
+			ch.allowedOrigins = []string{corsOriginMatchAll}
+			return
+		}
+	}
+
+	ch.allowedOrigins = origins
+}
+
+// setAllowedHeaders adds the provided headers to the list of allowed headers in a
+// CORS request.
+// This is an appended operation, so the headers Accept, Accept-Language,
+// and Content-Language are always allowed.
+// Content-Type must be explicitly declared if accepting Content-Types other than
+// application/x-www-form-urlencoded, multipart/form-data, or text/plain.
+func (ch *cors) setAllowedHeaders(headers []string) {
+	for _, v := range headers {
+		normalizedHeader := http.CanonicalHeaderKey(strings.TrimSpace(v))
+		if normalizedHeader == "" {
+			continue
+		}
+
+		if !ch.isMatch(normalizedHeader, ch.allowedHeaders) {
+			ch.allowedHeaders = append(ch.allowedHeaders, normalizedHeader)
+		}
+	}
+}
+
+// AllowedMethods can be used to explicitly allow methods in the
+// Access-Control-Allow-Methods header.
+// This is a replacement operation, so you must also
+// pass GET, HEAD, and POST if you wish to support those methods.
+func (ch *cors) setAllowedMethods(methods []string) {
+	if len(methods) == 0 {
+		return
+	}
+
+	ch.allowedMethods = []string{}
+	for _, v := range methods {
+		normalizedMethod := strings.ToUpper(strings.TrimSpace(v))
+		if normalizedMethod == "" {
+			continue
+		}
+
+		if !ch.isMatch(normalizedMethod, ch.allowedMethods) {
+			ch.allowedMethods = append(ch.allowedMethods, normalizedMethod)
+		}
+	}
+}
+
+// ExposedHeaders can be used to specify headers that are available
+// and will not be stripped out by the user-agent.
+func (ch *cors) setExposedHeaders(headers []string) {
+	ch.exposedHeaders = []string{}
+	for _, v := range headers {
+		normalizedHeader := http.CanonicalHeaderKey(strings.TrimSpace(v))
+		if normalizedHeader == "" {
+			continue
+		}
+
+		if !ch.isMatch(normalizedHeader, ch.exposedHeaders) {
+			ch.exposedHeaders = append(ch.exposedHeaders, normalizedHeader)
+		}
+	}
+}
+
+// MaxAge determines the maximum age (in seconds) between preflight requests. A
+// maximum of 10 minutes is allowed. An age above this value will default to 10
+// minutes.
+func (ch *cors) setMaxAge(age uint) {
+	// Maximum of 10 minutes.
+	if age > 600 {
+		age = 600
+	}
+
+	ch.maxAge = age
+}
+
+func (ch *cors) isOriginAllowed(origin string) bool {
+	if origin == "" {
+		return false
+	}
+
+	if ch.allowedOriginValidator != nil {
+		return ch.allowedOriginValidator(origin)
+	}
+
+	if len(ch.allowedOrigins) == 0 {
+		return true
+	}
+
+	for _, allowedOrigin := range ch.allowedOrigins {
+		if allowedOrigin == origin || allowedOrigin == corsOriginMatchAll {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (ch *cors) isMatch(needle string, haystack []string) bool {
+	for _, v := range haystack {
+		if v == needle {
+			return true
+		}
+	}
+
+	return false
+}

middleware/helmet.go

@@ -0,0 +1,351 @@
+package middleware
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+// inspired from Helmet.js
+// https://github.com/helmetjs/helmet/tree/main
+
+type (
+	HelmetOption struct {
+		ContentSecurityPolicy CSP
+
+		StrictTransportSecurity *TransportSecurity
+
+		// "require-corp" will be the default policy
+		CrossOriginEmbedderPolicy Embedder
+
+		// "same-origin" will be the default policy
+		CrossOriginOpenerPolicy Opener
+
+		// "same-origin" will be the default policy
+		CrossOriginResourcePolicy Resource
+
+		// "no-referrer" will be the default policy
+		ReferrerPolicy []Referrer
+
+		OriginAgentCluster bool
+
+		// set true to remove header "X-Content-Type-Options"
+		DisableSniffMimeType bool
+
+		// set true for header "X-DNS-Prefetch-Control: off"
+		//
+		// default is "X-DNS-Prefetch-Control: on"
+		DisableDNSPrefetch bool
+
+		// set true to remove header "X-Download-Options: noopen"
+		DisableXDownload bool
+
+		// X-Frame-Options
+		XFrameOption XFrame
+
+		// X-Permitted-Cross-Domain-Policies
+		//
+		// default value will be "none"
+		CrossDomainPolicies CDP
+
+		// X-XSS-Protection
+		//
+		// default is off
+		XssProtection bool
+	}
+
+	// CSP  is Content-Security-Policy settings
+	//
+	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/Sources
+	CSP struct {
+		// default-src, default value will be 'self'
+		DefaultSrc []string
+		// script-src,  default value will be 'self'
+		ScriptSrc []string
+		// script-src-attr, default value will be 'none'
+		ScriptSrcAttr []string
+		// style-src, default value will be 'self' https: 'unsafe-inline'
+		StyleSrc []string
+		// img-src, default value will be 'self' data:
+		ImgSrc []string
+		// object-src, default value will be 'none'
+		ObjectSrc []string
+		// base-uri, default value will be 'self'
+		BaseUri []string
+		// font-src, default value will be 'self' https: data:
+		FontSrc []string
+		// form-action, default value will be 'self'
+		FormAction []string
+		// frame-ancestors, default value will be 'self'
+		FrameAncestors []string
+
+		UpgradeInsecureRequests bool
+	}
+
+	TransportSecurity struct {
+		// Age in seconts
+		MaxAge            uint
+		IncludeSubDomains bool
+		Preload           bool
+	}
+
+	Embedder string
+	Opener   string
+	Resource string
+	Referrer string
+	// CDP Cross-Domain-Policy
+	CDP    string
+	XFrame string
+)
+
+const (
+	YearDuration = 365 * 24 * 60 * 60
+
+	// EmbedderDefault default value will be "require-corp"
+	EmbedderDefault        Embedder = ""
+	EmbedderRequireCorp    Embedder = "require-corp"
+	EmbedderCredentialLess Embedder = "credentialless"
+	EmbedderUnsafeNone     Embedder = "unsafe-none"
+
+	// OpenerDefault default value will be "same-origin"
+	OpenerDefault               Opener = ""
+	OpenerSameOrigin            Opener = "same-origin"
+	OpenerSameOriginAllowPopups Opener = "same-origin-allow-popups"
+	OpenerUnsafeNone            Opener = "unsafe-none"
+
+	// ResourceDefault default value will be "same-origin"
+	ResourceDefault     Resource = ""
+	ResourceSameOrigin  Resource = "same-origin"
+	ResourceSameSite    Resource = "same-site"
+	ResourceCrossOrigin Resource = "cross-origin"
+
+	NoReferrer                  Referrer = "no-referrer"
+	NoReferrerWhenDowngrade     Referrer = "no-referrer-when-downgrade"
+	SameOrigin                  Referrer = "same-origin"
+	Origin                      Referrer = "origin"
+	StrictOrigin                Referrer = "strict-origin"
+	OriginWhenCrossOrigin       Referrer = "origin-when-cross-origin"
+	StrictOriginWhenCrossOrigin Referrer = "strict-origin-when-cross-origin"
+	UnsafeUrl                   Referrer = "unsafe-url"
+
+	// CDPDefault default value is  "none"
+	CDPDefault       CDP = ""
+	CDPNone          CDP = "none"
+	CDPMasterOnly    CDP = "master-only"
+	CDPByContentType CDP = "by-content-type"
+	CDPAll           CDP = "all"
+
+	// XFrameDefault default value will be "sameorigin"
+	XFrameDefault    XFrame = ""
+	XFrameSameOrigin XFrame = "sameorigin"
+	XFrameDeny       XFrame = "deny"
+)
+
+// Helmet headers to secure server response
+func Helmet(opt HelmetOption) func(http.Handler) http.Handler {
+	return func(h http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Add("Content-Security-Policy", opt.ContentSecurityPolicy.value())
+
+			// Cross-Origin-Embedder-Policy, if nil set default
+			if opt.CrossOriginEmbedderPolicy == EmbedderDefault {
+				w.Header().Add("Cross-Origin-Embedder-Policy", string(EmbedderRequireCorp))
+			} else {
+				w.Header().Add("Cross-Origin-Embedder-Policy", string(opt.CrossOriginEmbedderPolicy))
+			}
+
+			// Cross-Origin-Opener-Policy, if nil set default
+			if opt.CrossOriginOpenerPolicy == OpenerDefault {
+				w.Header().Add("Cross-Origin-Opener-Policy", string(OpenerSameOrigin))
+			} else {
+				w.Header().Add("Cross-Origin-Opener-Policy", string(opt.CrossOriginOpenerPolicy))
+			}
+
+			// Cross-Origin-Resource-Policy, if nil set default
+			if opt.CrossOriginResourcePolicy == ResourceDefault {
+				w.Header().Add("Cross-Origin-Resource-Policy", string(ResourceSameOrigin))
+			} else {
+				w.Header().Add("Cross-Origin-Resource-Policy", string(opt.CrossOriginResourcePolicy))
+			}
+
+			// Referrer-Policy
+			rpCount := len(opt.ReferrerPolicy)
+			if rpCount > 0 {
+				refP := make([]string, rpCount)
+				for i, r := range opt.ReferrerPolicy {
+					refP[i] = string(r)
+				}
+				w.Header().Add("Referrer-Policy", string(NoReferrer))
+			} else {
+				// default no referer
+				w.Header().Add("Referrer-Policy", string(NoReferrer))
+			}
+
+			// Origin-Agent-Cluster
+			if opt.OriginAgentCluster {
+				w.Header().Add("Origin-Agent-Cluster", "?1")
+			}
+
+			// Strict-Transport-Security
+			if opt.StrictTransportSecurity != nil {
+				var sb strings.Builder
+
+				if opt.StrictTransportSecurity.MaxAge == 0 {
+					opt.StrictTransportSecurity.MaxAge = YearDuration
+				}
+
+				sb.WriteString(fmt.Sprintf("max-age=%d", opt.StrictTransportSecurity.MaxAge))
+				if opt.StrictTransportSecurity.IncludeSubDomains {
+					sb.WriteString("; includeSubDomains")
+				}
+
+				if opt.StrictTransportSecurity.Preload {
+					sb.WriteString("; preload")
+				}
+
+				w.Header().Add("Strict-Transport-Security", sb.String())
+			}
+
+			if !opt.DisableSniffMimeType {
+				// MIME types advertised in the Content-Current headers should be followed and not be changed
+				w.Header().Add("X-Content-Type-Options", "nosniff")
+			}
+
+			if opt.DisableDNSPrefetch {
+				w.Header().Add("X-DNS-Prefetch-Control", "off")
+			} else {
+				w.Header().Add("X-DNS-Prefetch-Control", "on")
+			}
+
+			if !opt.DisableXDownload {
+				// Instructs Internet Explorer not to open the file directly but to offer it for download first.
+				w.Header().Add("X-Download-Options", "noopen")
+			}
+
+			// indicate whether a browser should be allowed to render a page in iframe | frame | embed | object
+			if opt.XFrameOption == XFrameDefault {
+				w.Header().Add("X-Frame-Options", string(XFrameSameOrigin))
+			} else {
+				w.Header().Add("X-Frame-Options", string(opt.XFrameOption))
+			}
+
+			if opt.CrossDomainPolicies == CDPDefault {
+				w.Header().Add("X-Permitted-Cross-Domain-Policies", string(CDPNone))
+			} else {
+				w.Header().Add("X-Permitted-Cross-Domain-Policies", string(opt.CrossDomainPolicies))
+			}
+
+			w.Header().Del("X-Powered-By")
+
+			if opt.XssProtection {
+				// feature of IE, Chrome and Safari that stops pages from loading when they detect reflected
+				// cross-site scripting (XSS) attacks.
+				w.Header().Add("X-Xss-Protection", "1; mode=block")
+			} else {
+				// Following a decision by Google Chrome developers to disable Auditor,
+				// developers should be able to disable the auditor for older browsers and set it to 0.
+				// The X-XSS-PROTECTION header was found to have a multitude of issues, instead of helping the
+				// developers protect their application.
+				w.Header().Add("X-Xss-Protection", "0")
+			}
+
+			h.ServeHTTP(w, r)
+		})
+	}
+}
+
+func (csp *CSP) value() string {
+	var sb strings.Builder
+
+	// should be the first thing
+	if csp.UpgradeInsecureRequests {
+		sb.WriteString("upgrade-insecure-requests;")
+	}
+
+	sb.WriteString(fmt.Sprintf(
+		"default-src %s; ",
+		cspNormalised(csp.DefaultSrc, []string{"self"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"script-src %s; ",
+		cspNormalised(csp.ScriptSrc, []string{"self"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"script-src-attr %s; ",
+		cspNormalised(csp.ScriptSrcAttr, []string{"none"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"style-src %s; ",
+		cspNormalised(csp.StyleSrc, []string{"self", "https:", "unsafe-inline"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"img-src %s; ",
+		cspNormalised(csp.ImgSrc, []string{"self", "data:"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"object-src %s; ",
+		cspNormalised(csp.ObjectSrc, []string{"none"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"base-uri %s; ",
+		cspNormalised(csp.BaseUri, []string{"self"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"font-src %s; ",
+		cspNormalised(csp.FontSrc, []string{"self", "https:", "data:"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"form-action %s; ",
+		cspNormalised(csp.FormAction, []string{"self"}),
+	))
+
+	sb.WriteString(fmt.Sprintf(
+		"frame-ancestors %s; ",
+		cspNormalised(csp.FrameAncestors, []string{"self"}),
+	))
+
+	return sb.String()
+}
+
+func cspNormalised(v, defaultVal []string) string {
+	if len(v) == 0 {
+		v = defaultVal
+	}
+
+	var sb strings.Builder
+	for _, val := range v {
+		val = strings.TrimSpace(val)
+		if val == "" {
+			continue
+		}
+
+		sb.WriteString(" " + cspQuoted(val))
+	}
+
+	return strings.TrimSpace(sb.String())
+}
+
+func cspQuoted(v string) string {
+	switch v {
+	case "none",
+		"self",
+		"strict-dynamic",
+		"report-sample",
+		"inline-speculation-rules",
+		"unsafe-inline",
+		"unsafe-eval",
+		"unsafe-hashes",
+		"wasm-unsafe-eval":
+		return fmt.Sprintf("'%s'", v)
+	default:
+		return v
+	}
+}

middleware/helmet_test.go

@@ -0,0 +1,52 @@
+package middleware
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"gitserver.in/patialtech/mux"
+)
+
+func TestHelmet(t *testing.T) {
+	r := mux.NewRouter()
+	r.Use(Helmet(HelmetOption{}))
+	r.Get("/hello", func(writer http.ResponseWriter, request *http.Request) {
+		_, _ = writer.Write([]byte("hello there"))
+	})
+
+	srv := httptest.NewServer(r)
+	defer srv.Close()
+	w, _ := testRequest(t, srv, "GET", "/hello", nil)
+
+	csp := w.Header.Get("Content-Security-Policy")
+	// must not have a csp header, technically no header related to helmet but lets test with one.
+	if csp == "" {
+		t.Error("csp header is expected")
+	}
+
+}
+
+func testRequest(t *testing.T, ts *httptest.Server, method, path string, body io.Reader) (*http.Response, string) {
+	req, err := http.NewRequest(method, ts.URL+path, body)
+	if err != nil {
+		t.Fatal(err)
+		return nil, ""
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+		return nil, ""
+	}
+
+	respBody, err := io.ReadAll(io.Reader(resp.Body))
+	if err != nil {
+		t.Fatal(err)
+		return nil, ""
+	}
+	defer resp.Body.Close()
+
+	return resp, string(respBody)
+}

router.go

@@ -14,9 +14,10 @@ type Router struct {
 }
 
 func NewRouter() *Router {
-	return &Router{
+	r := &Router{
 		mux: http.NewServeMux(),
 	}
+	return r
 }
 
 // Use will register middleware(s) with router stack
@@ -27,48 +28,46 @@ func (r *Router) Use(h ...func(http.Handler) http.Handler) {
 	r.middlewares = append(r.middlewares, h...)
 }
 
-// Get method route
-func (r *Router) Get(pattern string, h http.HandlerFunc) {
+// GET method route
+func (r *Router) GET(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodGet, pattern, h)
 }
 
-// Head method route
-func (r *Router) Head(pattern string, h http.HandlerFunc) {
+// HEAD method route
+func (r *Router) HEAD(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodHead, pattern, h)
 }
 
-// Post method route
-func (r *Router) Post(pattern string, h http.HandlerFunc) {
+// POST method route
+func (r *Router) POST(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodPost, pattern, h)
 }
 
-// Put method route
-func (r *Router) Put(pattern string, h http.HandlerFunc) {
+// PUT method route
+func (r *Router) PUT(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodPut, pattern, h)
 }
 
-// Patch method route
-func (r *Router) Patch(pattern string, h http.HandlerFunc) {
+// PATCH method route
+func (r *Router) PATCH(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodPatch, pattern, h)
 }
 
-// Delete method route
-func (r *Router) Delete(pattern string, h http.HandlerFunc) {
+// DELETE method route
+func (r *Router) DELETE(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodDelete, pattern, h)
 }
 
-// Connect method route
-func (r *Router) Connect(pattern string, h http.HandlerFunc) {
+// CONNECT method route
+func (r *Router) CONNECT(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodConnect, pattern, h)
-}
-
-// Options method route
-func (r *Router) Options(pattern string, h http.HandlerFunc) {
+} // OPTIONS method route
+func (r *Router) OPTIONS(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodOptions, pattern, h)
 }
 
-// Trace method route
-func (r *Router) Trace(pattern string, h http.HandlerFunc) {
+// TRACE method route
+func (r *Router) TRACE(pattern string, h http.HandlerFunc) {
 	r.handlerFunc(http.MethodTrace, pattern, h)
 }
 
@@ -144,6 +143,8 @@ func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	r.mux.ServeHTTP(w, req)
 }
 
+// TODO: proxy for aws lambda
+
 // stack middlewares(http handler) in order they are passed (FIFO)
 func stack(middlewares []func(http.Handler) http.Handler, endpoint http.Handler) http.Handler {
 	// Return ahead of time if there aren't any middlewares for the chain

router_serve.go

@@ -3,6 +3,7 @@ package mux
 import (
 	"context"
 	"errors"
+	"io"
 	"log/slog"
 	"net/http"
 	"os"
@@ -13,6 +14,21 @@ type ServeCB func(srv *http.Server) error
 
 // Serve with graceful shutdown
 func (r *Router) Serve(cb ServeCB) {
+	// catch all options
+	// lets get it thorugh all middlewares
+	r.OPTIONS("/", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Length", "0")
+		if r.ContentLength != 0 {
+			// Read up to 4KB of OPTIONS body (as mentioned in the
+			// spec as being reserved for future use), but anything
+			// over that is considered a waste of server resources
+			// (or an attack) and we abort and close the connection,
+			// courtesy of MaxBytesReader's EOF behavior.
+			mb := http.MaxBytesReader(w, r.Body, 4<<10)
+			io.Copy(io.Discard, mb)
+		}
+	})
+
 	srv := &http.Server{
 		Handler: r,
 	}