emissary/internal/proxy/host_rewrite.go

package proxy

import (
	"net/http"
	"net/url"
	"sort"

	"forge.cadoles.com/Cadoles/emissary/internal/proxy/wildcard"
	"gitlab.com/wpetit/goweb/logger"
)

func RewriteHosts(mappings map[string]*url.URL) Middleware {
	patterns := make([]string, len(mappings))

	for p := range mappings {
		patterns = append(patterns, p)
	}

	sort.Strings(patterns)
	reverse(patterns)

	return func(h http.Handler) http.Handler {
		fn := func(w http.ResponseWriter, r *http.Request) {
			ctx := r.Context()

			var match *url.URL

			for _, p := range patterns {
				logger.Debug(ctx, "matching host to pattern", logger.F("host", r.Host), logger.F("pattern", p))

				if matches := wildcard.Match(r.Host, p); !matches {
					continue
				}

				match = mappings[p]
				break
			}

			if match == nil {
				h.ServeHTTP(w, r)

				return
			}

			ctx = logger.With(ctx, logger.F("originalHost", r.Host))
			r = r.WithContext(ctx)

			originalURL := r.URL.String()

			r.URL.Host = match.Host
			r.URL.Scheme = match.Scheme

			logger.Debug(ctx, "rewriting url", logger.F("from", originalURL), logger.F("to", r.URL.String()))

			h.ServeHTTP(w, r)
		}

		return http.HandlerFunc(fn)
	}
}

func WithRewriteHosts(mappings map[string]*url.URL) OptionFunc {
	return func(o *Options) {
		o.Middlewares = append(o.Middlewares, RewriteHosts(mappings))
	}
}