Validate External Tracker URL Format (#7089)

* Validate External Tracker URL Format

Add some validation checks for external tracker URL format.

Fixes #7068

* Don't make {index} a hard requirement

* Fix Description

* make fmt

* move regex to package level

* fix copyright date

modules/validation/helpers.go

@@ -7,6 +7,7 @@ package validation
 import (
 	"net"
 	"net/url"
+	"regexp"
 	"strings"
 
 	"code.gitea.io/gitea/modules/setting"
@@ -14,6 +15,8 @@ import (
 
 var loopbackIPBlocks []*net.IPNet
 
+var externalTrackerRegex = regexp.MustCompile(`({?)(?:user|repo|index)+?(}?)`)
+
 func init() {
 	for _, cidr := range []string{
 		"127.0.0.0/8", // IPv4 loopback
@@ -75,3 +78,19 @@ func IsValidExternalURL(uri string) bool {
 
 	return true
 }
+
+// IsValidExternalTrackerURLFormat checks if URL matches required syntax for external trackers
+func IsValidExternalTrackerURLFormat(uri string) bool {
+	if !IsValidExternalURL(uri) {
+		return false
+	}
+
+	// check for typoed variables like /{index/ or /[repo}
+	for _, match := range externalTrackerRegex.FindAllStringSubmatch(uri, -1) {
+		if (match[1] == "{" || match[2] == "}") && (match[1] != "{" || match[2] != "}") {
+			return false
+		}
+	}
+
+	return true
+}