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package middleware
import (
"bytes"
"encoding/json"
"fmt"
"net/url"
"reflect"
"strings"
"time"
"github.com/labstack/echo/v4"
"github.com/labstack/echo/v4/middleware"
)
const HeaderReportTo = "ReportTo"
type ContentSecurityPolicyConfig struct {
Skipper middleware.Skipper
ReportOnly bool
DefaultSrc []CSPDirective `csp:"default-src"`
ChildSrc []CSPDirective `csp:"child-src"`
ConnectSrc []CSPDirective `csp:"connect-src"`
FontSrc []CSPDirective `csp:"font-src"`
FrameSrc []CSPDirective `csp:"frame-src"`
ImageSrc []CSPDirective `csp:"img-src"`
ManifestSrc []CSPDirective `csp:"manifest-src"`
MediaSrc []CSPDirective `csp:"media-src"`
ObjectSrc []CSPDirective `csp:"object-src"`
ScriptSrc []CSPDirective `csp:"script-src"`
StyleSrc []CSPDirective `csp:"style-src"`
BaseUri []CSPDirective `csp:"base-uri"`
Sandbox []CSPSandbox `csp:"sandbox"`
FormAction []CSPDirective `csp:"form-action"`
UpgradeInsecureRequests bool `csp:"upgrade-insecure-requests"`
FrameAncestors []CSPDirective `csp:"frame-ancestors"`
ReportUri []*url.URL `csp:"report-uri"` // deprecated
ReportTo []CSPReportTo `csp:"report-to"` // experimental
PrefetchSrc []CSPDirective `csp:"prefetch-src"` // experimental
ScriptSrcElem []CSPDirective `csp:"script-src-elem"` // experimental
StyleSrcElem []CSPDirective `csp:"style-src-elem"` // experimental
StyleSrcAttr []CSPDirective `csp:"script-src-attr"` // experimental
WorkerSrc []CSPDirective `csp:"worker-src"` // experimental
NavigateTo []CSPDirective `csp:"navigate-to"` // experimental
RequireTrustedTypesFor []CSPDirective `csp:"require-trusted-types-for"` // experimental
}
func (c *ContentSecurityPolicyConfig) String() string {
st := reflect.TypeOf(*c)
sv := reflect.ValueOf(*c)
lines := []string{}
for i := 0; i < st.NumField(); i++ {
cspTag := st.Field(i).Tag.Get("csp")
if cspTag == "" {
continue
}
v := sv.Field(i)
switch v.Kind() {
case reflect.Slice:
if v.Cap() == 0 {
continue
}
items := make([]string, v.Cap())
for j := 0; j < v.Cap(); j++ {
// Call the String() method if there is one to handle things
// like *net.URL instances. Otherwise just treat the value as a
// string because it probably is (all CSPDirective types are
// strings).
if str := v.Index(j).MethodByName("String"); str.IsValid() {
items[j] = str.Call(nil)[0].String()
} else {
items[j] = v.Index(j).String()
}
}
lines = append(lines, fmt.Sprintf("%s %s", cspTag, strings.Join(items, " ")))
case reflect.Bool:
if v.Bool() {
lines = append(lines, cspTag)
}
}
}
return strings.Join(lines, "; ") + ";"
}
type CSPReportTo struct {
GroupName string
MaxAge time.Duration
Endpoints []*url.URL
}
func (r CSPReportTo) MarshalJSON() ([]byte, error) {
ep := []map[string]string{}
for _, u := range r.Endpoints {
ep = append(ep, map[string]string{"url": u.String()})
}
return json.Marshal(map[string]interface{}{
"group": r.GroupName,
"max_age": r.MaxAge.Seconds(),
"endpoints": ep,
})
}
type CSPDirective string
const (
CSPNone CSPDirective = "'none'"
CSPSelf = "'self'"
CSPUnsafeInline = "'unsafe-inline'"
CSPUnsafeEval = "'unsafe-eval'"
CSPUnsafeHashes = "'unsafe-hashes'"
CSPStrictDynamic = "'strict-dynamic'"
CSPReportSample = "'report-sample'"
CSPData = "data:"
CSPBlob = "blob:"
CSPMediastream = "mediastream:"
CSPFilesystem = "filesystem:"
CSPHttp = "http:"
CSPHttps = "https:"
)
func CSPHost(s string) CSPDirective {
return CSPDirective(s)
}
func CSPNonce(n string) CSPDirective {
return CSPDirective(fmt.Sprintf("'nonce-%s'", n))
}
func CSPShaString(size int, h string) CSPDirective {
return CSPDirective(fmt.Sprintf("'sha%d-%s'", size, h))
}
type CSPSandbox string
const (
CSPAllowDownloads CSPSandbox = "allow-downloads"
CSPAllowDownloadsNoUser = "allow-downloads-without-user-activation"
CSPAllowForms = "allow-forms"
CSPAllowModals = "allow-modals"
CSPAllowOrientationLock = "allow-orientation-lock"
CSPAllowPointerLock = "allow-pointer-lock"
CSPAllowPopups = "allow-popups"
CSPAllowPopupEscape = "allow-popups-to-escape-sandbox"
CSPAllowPresentation = "allow-presentation"
CSPAllowSameOrigin = "allow-same-origin"
CSPAllowScripts = "allow-scripts"
CSPAllowStorageAccessByUser = "allow-storage-access-by-user-activation"
CSPAllowTopActivation = "allow-top-navigation"
CSPAllowNavigationByUser = "allow-top-navigation-by-user-activation"
)
var DefaultContentSecurityPolicyConfig = ContentSecurityPolicyConfig{
Skipper: middleware.DefaultSkipper,
DefaultSrc: []CSPDirective{CSPSelf, CSPData},
}
func ContentSecurityPolicy() echo.MiddlewareFunc {
return ContentSecurityPolicyWithConfig(DefaultContentSecurityPolicyConfig)
}
func ContentSecurityPolicyWithConfig(config ContentSecurityPolicyConfig) echo.MiddlewareFunc {
if config.Skipper == nil {
config.Skipper = DefaultContentSecurityPolicyConfig.Skipper
}
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
if config.Skipper(c) {
return next(c)
}
h := c.Response().Header()
if config.ReportOnly {
h.Set(echo.HeaderContentSecurityPolicyReportOnly, config.String())
} else {
h.Set(echo.HeaderContentSecurityPolicy, config.String())
}
if config.ReportTo != nil {
rt := bytes.Buffer{}
je := json.NewEncoder(&rt)
for _, r := range config.ReportTo {
_ = je.Encode(r)
rt.WriteString(", ")
}
h.Set(HeaderReportTo, rt.String())
}
return next(c)
}
}
}
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