headers: New 'request_header' directive; handle Host header specially

Before this change, only response headers could be manipulated with the
Caddyfile's 'header' directive.

Also handle the request Host header specially, since the Go standard
library treats it separately from the other header fields...

1 files changed, 11 insertions, 0 deletions

diff --git a/modules/caddyhttp/headers/headers.go b/modules/caddyhttp/headers/headers.go
index e740004..ba9d89d 100644
--- a/modules/caddyhttp/headers/headers.go
+++ b/modules/caddyhttp/headers/headers.go
@@ -58,7 +58,18 @@ type RespHeaderOps struct {
 
 func (h Headers) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
 	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+
 	apply(h.Request, r.Header, repl)
+
+	// request header's Host is handled specially by the
+	// Go standard library, so if that header was changed,
+	// change it in the Host field since the Header won't
+	// be used
+	if intendedHost := r.Header.Get("Host"); intendedHost != "" {
+		r.Host = intendedHost
+		r.Header.Del("Host")
+	}
+
 	if h.Response != nil {
 		if h.Response.Deferred || h.Response.Require != nil {
 			w = &responseWriterWrapper{