ContainerImage.Pinniped/internal/oidc/provider/formposthtml/formposthtml.go

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// Copyright 2021 the Pinniped contributors. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
// Package formposthtml defines HTML templates used by the Supervisor.
//nolint: gochecknoglobals // This package uses globals to ensure that all parsing and minifying happens at init.
package formposthtml
import (
"crypto/sha256"
_ "embed" // Needed to trigger //go:embed directives below.
"encoding/base64"
"html/template"
"strings"
"github.com/tdewolff/minify/v2/minify"
)
var (
//go:embed form_post.css
rawCSS string
minifiedCSS = mustMinify(minify.CSS(rawCSS))
//go:embed form_post.js
rawJS string
minifiedJS = mustMinify(minify.JS(rawJS))
//go:embed form_post.gohtml
rawHTMLTemplate string
)
// Parse the Go templated HTML and inject functions providing the minified inline CSS and JS.
var parsedHTMLTemplate = template.Must(template.New("form_post.gohtml").Funcs(template.FuncMap{
"minifiedCSS": func() template.CSS { return template.CSS(minifiedCSS) },
"minifiedJS": func() template.JS { return template.JS(minifiedJS) }, //nolint:gosec // This is 100% static input, not attacker-controlled.
}).Parse(rawHTMLTemplate))
// Generate the CSP header value once since it's effectively constant:
var cspValue = strings.Join([]string{
`default-src 'none'`,
`script-src '` + cspHash(minifiedJS) + `'`,
`style-src '` + cspHash(minifiedCSS) + `'`,
`img-src data:`,
`connect-src *`,
`frame-ancestors 'none'`,
}, "; ")
func mustMinify(s string, err error) string {
if err != nil {
panic(err)
}
return s
}
func cspHash(s string) string {
hashBytes := sha256.Sum256([]byte(s))
return "sha256-" + base64.StdEncoding.EncodeToString(hashBytes[:])
}
// ContentSecurityPolicy returns the Content-Security-Policy header value to make the Template() operate correctly.
//
// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/default-src#:~:text=%27%3Chash-algorithm%3E-%3Cbase64-value%3E%27.
func ContentSecurityPolicy() string { return cspValue }
// Template returns the html/template.Template for rendering the response_type=form_post response page.
func Template() *template.Template { return parsedHTMLTemplate }