fix(agentci): split path sanitising and validation

Co-Authored-By: Virgil <virgil@lethean.io>

agentci/security.go

@@ -16,28 +16,36 @@ import (
 var safeNameRegex = regexp.MustCompile(`^[a-zA-Z0-9\-\_\.]+$`)
 
 // SanitizePath ensures a filename or directory name is safe and prevents path traversal.
-// Returns the validated input unchanged.
+// Returns the validated basename.
 // Usage: SanitizePath(...)
 func SanitizePath(input string) (string, error) {
 	if input == "" {
 		return "", coreerr.E("agentci.SanitizePath", "path element is required", nil)
 	}
-	if strings.ContainsAny(input, `/\`) {
-		return "", coreerr.E("agentci.SanitizePath", "path separators are not allowed: "+input, nil)
-	}
-	if input == "." || input == ".." {
+	safeName := filepath.Base(input)
+	if safeName == "." || safeName == ".." {
 		return "", coreerr.E("agentci.SanitizePath", "invalid path element: "+input, nil)
 	}
-	if !safeNameRegex.MatchString(input) {
+	if strings.ContainsAny(safeName, `/\`) {
+		return "", coreerr.E("agentci.SanitizePath", "path separators are not allowed: "+input, nil)
+	}
+	if !safeNameRegex.MatchString(safeName) {
 		return "", coreerr.E("agentci.SanitizePath", "invalid characters in path element: "+input, nil)
 	}
-	return input, nil
+	return safeName, nil
 }
 
 // ValidatePathElement validates a single local path element and returns its safe form.
 // Usage: ValidatePathElement(...)
 func ValidatePathElement(input string) (string, error) {
-	return SanitizePath(input)
+	safeName, err := SanitizePath(input)
+	if err != nil {
+		return "", err
+	}
+	if safeName != input {
+		return "", coreerr.E("agentci.ValidatePathElement", "path separators are not allowed: "+input, nil)
+	}
+	return safeName, nil
 }
 
 // ResolvePathWithinRoot resolves a validated path element beneath a root directory.

agentci/security_test.go

@@ -21,6 +21,9 @@ func TestSanitizePath_Good(t *testing.T) {
 		{"with.dot", "with.dot"},
 		{"CamelCase", "CamelCase"},
 		{"123", "123"},
+		{"../secret", "secret"},
+		{"/var/tmp/report.txt", "report.txt"},
+		{"nested/path/file", "file"},
 	}
 
 	for _, tt := range tests {
@@ -44,8 +47,8 @@ func TestSanitizePath_Bad(t *testing.T) {
 		{"pipe", "file|name"},
 		{"ampersand", "file&name"},
 		{"dollar", "file$name"},
-		{"slash", "path/to/file.txt"},
 		{"backslash", `path\to\file.txt`},
+		{"current dir", "."},
 		{"parent traversal base", ".."},
 		{"root", "/"},
 		{"empty", ""},