69 lines
1.6 KiB
Go
69 lines
1.6 KiB
Go
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package main
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import (
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"crypto/rand"
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"fmt"
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"math/big"
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"net/http"
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"os"
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"log/slog"
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"github.com/a-h/templ"
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)
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func main() {
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log := slog.New(slog.NewJSONHandler(os.Stderr, nil))
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// Create HTTP routes.
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mux := http.NewServeMux()
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mux.Handle("/", templ.Handler(template()))
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// Wrap the router with CSP middleware to apply the CSP nonce to templ scripts.
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withCSPMiddleware := NewCSPMiddleware(log, mux)
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log.Info("Listening...", slog.String("addr", "127.0.0.1:7001"))
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if err := http.ListenAndServe("127.0.0.1:7001", withCSPMiddleware); err != nil {
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log.Error("failed to start server", slog.Any("error", err))
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}
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}
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func NewCSPMiddleware(log *slog.Logger, next http.Handler) *CSPMiddleware {
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return &CSPMiddleware{
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Log: log,
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Next: next,
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Size: 28,
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}
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}
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type CSPMiddleware struct {
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Log *slog.Logger
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Next http.Handler
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Size int
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}
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func (m *CSPMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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nonce, err := m.generateNonce()
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if err != nil {
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m.Log.Error("failed to generate nonce", slog.Any("error", err))
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http.Error(w, "Internal server error", http.StatusInternalServerError)
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return
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}
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ctx := templ.WithNonce(r.Context(), nonce)
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w.Header().Add("Content-Security-Policy", fmt.Sprintf("script-src 'nonce-%s'", nonce))
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m.Next.ServeHTTP(w, r.WithContext(ctx))
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}
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func (m *CSPMiddleware) generateNonce() (string, error) {
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const letters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"
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ret := make([]byte, m.Size)
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for i := 0; i < m.Size; i++ {
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num, err := rand.Int(rand.Reader, big.NewInt(int64(len(letters))))
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if err != nil {
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return "", err
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}
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ret[i] = letters[num.Int64()]
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}
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return string(ret), nil
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}
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