Add support for rewriting headers

http_modifier.go

@@ -16,6 +16,7 @@ func NewHTTPModifier(config *HTTPModifierConfig) *HTTPModifier {
 	if len(config.urlRegexp) == 0 &&
 		len(config.urlNegativeRegexp) == 0 &&
 		len(config.urlRewrite) == 0 &&
+		len(config.headerRewrite) == 0 &&
 		len(config.headerFilters) == 0 &&
 		len(config.headerNegativeFilters) == 0 &&
 		len(config.headerHashFilters) == 0 &&
@@ -153,5 +154,19 @@ func (m *HTTPModifier) Rewrite(payload []byte) (response []byte) {
 		}
 	}
 
+	if len(m.config.headerRewrite) > 0 {
+		for _, f := range m.config.headerRewrite {
+			value := proto.Header(payload, f.header)
+			if len(value) == 0 {
+				break
+			}
+
+			if f.src.Match(value) {
+				newValue := f.src.ReplaceAll(value, f.target)
+				payload = proto.SetHeader(payload, f.header, newValue)
+			}
+		}
+	}
+
 	return payload
 }

http_modifier_settings.go

@@ -13,6 +13,7 @@ type HTTPModifierConfig struct {
 	urlNegativeRegexp     HTTPUrlRegexp
 	urlRegexp             HTTPUrlRegexp
 	urlRewrite            UrlRewriteMap
+	headerRewrite         HeaderRewriteMap
 	headerFilters         HTTPHeaderFilters
 	headerNegativeFilters HTTPHeaderFilters
 	headerHashFilters     HTTPHashFilters
@@ -196,6 +197,43 @@ func (r *UrlRewriteMap) Set(value string) error {
 	return nil
 }
 
+//
+// Handling of --http-rewrite-header option
+//
+type headerRewrite struct {
+	header []byte
+	src    *regexp.Regexp
+	target []byte
+}
+
+type HeaderRewriteMap []headerRewrite
+
+func (r *HeaderRewriteMap) String() string {
+	return fmt.Sprint(*r)
+}
+
+func (r *HeaderRewriteMap) Set(value string) error {
+	headerArr := strings.SplitN(value, ":", 2)
+	if len(headerArr) < 2 {
+		return errors.New("need both header, regexp and rewrite target, colon-delimited (ex. Header: regexp,target)")
+	}
+
+	header := headerArr[0]
+	valArr := strings.SplitN(strings.TrimSpace(headerArr[1]), ",", 2)
+
+	if len(valArr) < 2 {
+		return errors.New("need both header, regexp and rewrite target, colon-delimited (ex. Header: regexp,target)")
+	}
+
+	regexp, err := regexp.Compile(valArr[0])
+	if err != nil {
+		return err
+	}
+	*r = append(*r, headerRewrite{header: []byte(header), src: regexp, target: []byte(valArr[1])})
+	return nil
+}
+
+
 //
 // Handling of --http-allow-url option
 //

http_modifier_test.go

@@ -107,6 +107,27 @@ func TestHTTPModifierURLRewrite(t *testing.T) {
 	}
 }
 
+func TestHTTPModifierHeaderRewrite(t *testing.T) {
+	var header, newHeader []byte
+
+	rewrites := HeaderRewriteMap{}
+	payload := []byte("GET / HTTP/1.1\r\nContent-Length: 7\r\nHost: www.w3.org\r\n\r\na=1&b=2")
+
+	err := rewrites.Set("Host: (.*).w3.org,$1.beta.w3.org")
+	if err != nil {
+		t.Error("Should not error", err)
+	}
+
+	modifier := NewHTTPModifier(&HTTPModifierConfig{
+		headerRewrite: rewrites,
+	})
+
+	header = []byte("www.beta.w3.org")
+	if newHeader = proto.Header(modifier.Rewrite(payload), []byte("Host")); !bytes.Equal(newHeader, header) {
+		t.Error("Request header should have been rewritten, wasn't", string(newHeader), string(header))
+	}
+}
+
 func TestHTTPModifierHeaderHashFilters(t *testing.T) {
 	filters := HTTPHashFilters{}
 	filters.Set("Header2:1/2")

settings.go

@@ -148,6 +148,8 @@ func init() {
 	flag.Var(&Settings.modifierConfig.headers, "http-set-header", "Inject additional headers to http reqest:\n\tgor --input-raw :8080 --output-http staging.com --http-set-header 'User-Agent: Gor'")
 	flag.Var(&Settings.modifierConfig.headers, "output-http-header", "WARNING: `--output-http-header` DEPRECATED, use `--http-set-header` instead")
 
+	flag.Var(&Settings.modifierConfig.headerRewrite, "http-rewrite-header", "Rewrite the request header based on a mapping:\n\tgor --input-raw :8080 --output-http staging.com --http-rewrite-header Host: (.*).example.com,$1.beta.example.com")
+
 	flag.Var(&Settings.modifierConfig.params, "http-set-param", "Set request url param, if param already exists it will be overwritten:\n\tgor --input-raw :8080 --output-http staging.com --http-set-param api_key=1")
 
 	flag.Var(&Settings.modifierConfig.methods, "http-allow-method", "Whitelist of HTTP methods to replay. Anything else will be dropped:\n\tgor --input-raw :8080 --output-http staging.com --http-allow-method GET --http-allow-method OPTIONS")