hyperguild/ingestion/internal/mcp/auth.go

package mcp

import (
	"crypto/subtle"
	"net/http"
	"strings"

	"github.com/mathiasbq/hyperguild/ingestion/internal/auth"
)

// BearerAuth returns a middleware that enforces authentication on every request.
// It tries a valid Dex JWT first (when v is non-nil), then falls back to the
// static token. Rejects if token is empty and no valid JWT is presented.
func BearerAuth(token string, v *auth.Validator, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		rawToken, ok := strings.CutPrefix(r.Header.Get("Authorization"), "Bearer ")
		if !ok {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}

		if v != nil {
			if _, err := v.Validate(r.Context(), rawToken); err == nil {
				next.ServeHTTP(w, r)
				return
			}
		}

		if token != "" && subtle.ConstantTimeCompare([]byte(rawToken), []byte(token)) == 1 {
			next.ServeHTTP(w, r)
			return
		}

		http.Error(w, "unauthorized", http.StatusUnauthorized)
	})
}