Support substring exempt user agents (#91)

Author: joecorall

README.md

@@ -90,7 +90,7 @@ services:
             --providers.docker=true
             --providers.docker.network=default
             --experimental.plugins.captcha-protect.modulename=github.com/libops/captcha-protect
-            --experimental.plugins.captcha-protect.version=v1.12.4
+            --experimental.plugins.captcha-protect.version=v1.12.5
         volumes:
             - /var/run/docker.sock:/var/run/docker.sock:z
             - /CHANGEME/TO/A/HOST/PATH/FOR/STATE/FILE:/tmp/state.json:rw
@@ -130,7 +130,7 @@ services:
 | `protectFileExtensions` | `[]string`              | `""`                     | Comma-separated file extensions to protect. By default, your protected routes only protect html files. This is to prevent files like CSS/JS/img from tripping the rate limit.                    |
 | `protectHttpMethods`    | `[]string`              | `"GET,HEAD"`             | Comma-separated list of HTTP methods to protect against                                                                                                                                          |
 | `exemptIps`             | `[]string`              | `privateIPs`             | CIDR-formatted IPs that should never be challenged. Private IP ranges are always exempt.                                                                                                         |
-| `exemptUserAgents`      | `[]string`              | `""`                     | Comma-separated list of case-insensitive user agent **prefixes** to never challenge. e.g. `exemptUserAgents: edge` would never challenge useragents like "Edge/12.4 ..."                         |
+| `exemptUserAgents`      | `[]string`              | `""`                     | Comma-separated list of case-insensitive user agent substrings to never challenge. For example, `exemptUserAgents: YandexBot` exempts user agents containing `YandexBot`.                         |
 | `challengeURL`          | `string`                | `"/challenge"`           | URL where challenges are served. This will override existing routes if there is a conflict. Setting to blank will have the challenge presented on the same page that tripped the rate limit.     |
 | `challengeTmpl`         | `string`                | `"./challenge.tmpl.html"`| Path to the Go HTML template for the captcha challenge page.                                                                                                                                     |
 | `challengeStatusCode`   | `int`                   | `200`                    | HTTP Response status code to return when serving a challenge                                                                                                                                     |

main.go

@@ -858,8 +858,8 @@ protected:
 
 func (bc *CaptchaProtect) isGoodUserAgent(ua string) bool {
 	ua = strings.ToLower(ua)
-	for _, agentPrefix := range bc.config.ExemptUserAgents {
-		if strings.HasPrefix(ua, agentPrefix) {
+	for _, agentSubstring := range bc.config.ExemptUserAgents {
+		if strings.Contains(ua, agentSubstring) {
 			return true
 		}
 	}

main_test.go

@@ -615,10 +615,11 @@ func TestIsGoodUserAgent(t *testing.T) {
 		ua               string
 		expected         bool
 	}{
-		{"Matching first prefix", []string{"Mozilla", "Google"}, "Mozilla/5.0 (Windows NT 10.0; Win64; x64)", true},
-		{"Matching second prefix", []string{"Bing", "Edge"}, "Edge/12.0", true},
+		{"Matching first substring", []string{"Mozilla", "Google"}, "Mozilla/5.0 (Windows NT 10.0; Win64; x64)", true},
+		{"Matching second substring", []string{"Bing", "Edge"}, "Edge/12.0", true},
+		{"Matching substring within user agent", []string{"YandexBot"}, "Mozilla/5.0 (compatible; YandexBot/3.0; +http://yandex.com/bots)", true},
 		{"Case insensitive", []string{"bing", "Edge"}, "BING/12.0", true},
-		{"No matching prefix", []string{"Mozilla", "Google"}, "Safari/537.36", false},
+		{"No matching substring", []string{"Mozilla", "Google"}, "Safari/537.36", false},
 		{"Empty user agent", []string{"Mozilla", "Google"}, "", false},
 		{"Empty exempt list", []string{}, "Mozilla/5.0", false},
 	}