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csp.go
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csp.go
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// Copyright 2017 Corey Scott http://www.sage42.org/
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package middleware
import (
"net/http"
"github.com/corsc/go-commons/http/middleware/csp"
)
const (
cspHeader = "Content-Security-Policy"
cspPrefixDefault = "default-src"
cspPrefixBase = "base-uri"
cspPrefixChild = "child-src"
cspPrefixConnect = "connect-src"
cspPrefixFont = "font-src"
cspPrefixForm = "form-action"
cspPrefixFrame = "frame-ancestors"
cspPrefixImage = "img-src"
cspPrefixMedia = "media-src"
cspPrefixObject = "object-src"
cspPrefixPlugin = "plugin-types"
cspPrefixReport = "report-uri"
cspPrefixScript = "script-src"
cspPrefixStyle = "style-src"
cspPrefixUpgradeInsecure = "upgrade-insecure-requests"
cspSeparator = ";"
)
// CSP sends Content Security Policy header.
//
// Reference:
// https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP
// https://www.html5rocks.com/en/tutorials/security/content-security-policy/
func CSP(handler http.Handler, config *csp.Config) http.HandlerFunc {
return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
value := ""
cspAdd(&value, cspPrefixDefault, config.Default)
cspAdd(&value, cspPrefixBase, config.Base)
cspAdd(&value, cspPrefixChild, config.Child)
cspAdd(&value, cspPrefixConnect, config.Connect)
cspAdd(&value, cspPrefixFont, config.Font)
cspAdd(&value, cspPrefixForm, config.Form)
cspAdd(&value, cspPrefixFrame, config.Frame)
cspAdd(&value, cspPrefixImage, config.Image)
cspAdd(&value, cspPrefixMedia, config.Media)
cspAdd(&value, cspPrefixObject, config.Object)
cspAdd(&value, cspPrefixPlugin, config.Plugin)
cspAdd(&value, cspPrefixScript, config.Script)
cspAdd(&value, cspPrefixStyle, config.Style)
cspAddString(&value, cspPrefixReport, config.Report)
cspAddBool(&value, cspPrefixUpgradeInsecure, config.UpgradeInsecure)
resp.Header().Set(cspHeader, value)
handler.ServeHTTP(resp, req)
})
}
func cspAdd(dest *string, prefix string, locations []string) {
if len(locations) == 0 {
return
}
if len(*dest) > 0 {
*dest += " "
}
*dest += prefix
for _, location := range locations {
*dest += " " + location
}
*dest += cspSeparator
}
func cspAddString(dest *string, prefix string, value string) {
if len(value) == 0 {
return
}
if len(*dest) > 0 {
*dest += " "
}
*dest += prefix + " " + value + cspSeparator
}
func cspAddBool(dest *string, output string, value bool) {
if !value {
return
}
if len(*dest) > 0 {
*dest += " "
}
*dest += output + cspSeparator
}