headers: Support wildcards for delete ops (close #4830) (#4831)

modules/caddyhttp/headers/headers.go

@@ -118,10 +118,16 @@ type HeaderOps struct {
 	// Sets HTTP headers; replaces existing header fields.
 	Set http.Header `json:"set,omitempty"`
 
-	// Names of HTTP header fields to delete.
+	// Names of HTTP header fields to delete. Basic wildcards are supported:
+	//
+	// - Start with `*` for all field names with the given suffix;
+	// - End with `*` for all field names with the given prefix;
+	// - Start and end with `*` for all field names containing a substring.
 	Delete []string `json:"delete,omitempty"`
 
-	// Performs substring replacements of HTTP headers in-situ.
+	// Performs in-situ substring replacements of HTTP headers.
+	// Keys are the field names on which to perform the associated replacements.
+	// If the field name is `*`, the replacements are performed on all header fields.
 	Replace map[string][]Replacement `json:"replace,omitempty"`
 }
 
@@ -208,7 +214,29 @@ func (ops HeaderOps) ApplyTo(hdr http.Header, repl *caddy.Replacer) {
 
 	// delete
 	for _, fieldName := range ops.Delete {
-		hdr.Del(repl.ReplaceAll(fieldName, ""))
+		fieldName = strings.ToLower(repl.ReplaceAll(fieldName, ""))
+		switch {
+		case strings.HasPrefix(fieldName, "*") && strings.HasSuffix(fieldName, "*"):
+			for existingField := range hdr {
+				if strings.Contains(strings.ToLower(existingField), fieldName[1:len(fieldName)-1]) {
+					delete(hdr, existingField)
+				}
+			}
+		case strings.HasPrefix(fieldName, "*"):
+			for existingField := range hdr {
+				if strings.HasSuffix(strings.ToLower(existingField), fieldName[1:]) {
+					delete(hdr, existingField)
+				}
+			}
+		case strings.HasSuffix(fieldName, "*"):
+			for existingField := range hdr {
+				if strings.HasPrefix(strings.ToLower(existingField), fieldName[:len(fieldName)-1]) {
+					delete(hdr, existingField)
+				}
+			}
+		default:
+			hdr.Del(fieldName)
+		}
 	}
 
 	// replace

modules/caddyhttp/headers/headers_test.go

@@ -79,6 +79,26 @@ func TestHandler(t *testing.T) {
 				"Keep-Me": []string{"i swear i'm innocent"},
 			},
 		},
+		{
+			handler: Handler{
+				Request: &HeaderOps{
+					Delete: []string{
+						"*-suffix",
+						"prefix-*",
+						"*_*",
+					},
+				},
+			},
+			reqHeader: http.Header{
+				"Header-Suffix": []string{"lalala"},
+				"Prefix-Test":   []string{"asdf"},
+				"Host_Header":   []string{"silly django... sigh"}, // see issue #4830
+				"Keep-Me":       []string{"foofoofoo"},
+			},
+			expectedReqHeader: http.Header{
+				"Keep-Me": []string{"foofoofoo"},
+			},
+		},
 		{
 			handler: Handler{
 				Request: &HeaderOps{