pkg/ffuf: fix panic in Windows when parsing wordlist flag (#335)

This change addresses two panics that happened while parsing the provided
wordlist flag in Windows systems.

- pkg/ffuf/util.go:40: panic happened when the provided path was
invalid. Example: ".\wordlist.txt:" as the os.Stat call returned an
error different than os.ErrNotExist.

- pkg/ffuf/optionsparser.go:179: panic happened when the provided value
did not existed and did not contain a colon character. Example:
".\asdf.txt" when the local file ".\asdf.txt" did not exist. This panic
happened due to strings.LastIndex returning -1 when the provided
substring does not appear. Therefore, v[:-1] panicking.

Fixes #333

Signed-off-by: Miguel Ángel Jimeno <miguelangel4b@gmail.com>

CHANGELOG.md

@@ -14,6 +14,7 @@
     - Fixed the issue where the option -ac was overwriting existing filters. Now auto-calibration will add them where needed.
     - The `-w` flag now accepts comma delimited values in the form of `file1:W1,file2:W2`.
     - Links in the HTML report are now clickable
+    - Fixed panic during wordlist flag parsing in Windows systems.
 
 - v1.1.0
   - New

pkg/ffuf/optionsparser.go

@@ -176,7 +176,11 @@ func ConfigFromOptions(parseOpts *ConfigOptions, ctx context.Context, cancel con
 				// The wordlist was supplied without a keyword parameter
 				wl = []string{v}
 			} else {
-				filepart := v[:strings.LastIndex(v, ":")]
+				filepart := v
+				if strings.Contains(filepart, ":") {
+					filepart = v[:strings.LastIndex(filepart, ":")]
+				}
+
 				if FileExists(filepart) {
 					wl = []string{filepart, v[strings.LastIndex(v, ":")+1:]}
 				} else {

pkg/ffuf/util.go

@@ -31,11 +31,13 @@ func UniqStringSlice(inslice []string) []string {
 	return ret
 }
 
-//FileExists checks if the filepath exists and is not a directory
+//FileExists checks if the filepath exists and is not a directory.
+//Returns false in case it's not possible to describe the named file.
 func FileExists(path string) bool {
 	md, err := os.Stat(path)
-	if os.IsNotExist(err) {
+	if err != nil {
 		return false
 	}
+
 	return !md.IsDir()
 }