fix: Enhanced SQL injection protection in funcspec

- Added sanitization for path parameters in mergePathParams
- Added sanitization for query parameters with p- prefix in mergeQueryParams
- Added sanitization for header parameters in mergeHeaderParams
- Fixed IN clause to sanitize all values individually
- Improved ValidSQL function with better escaping and more injection patterns
- Added backslash escaping to colvalue mode
- Extended dangerous keyword list in select mode

Co-authored-by: warkanum <208308+warkanum@users.noreply.github.com>

pkg/funcspec/function_api.go

@@ -662,7 +662,10 @@ func (h *Handler) mergePathParams(r *http.Request, sqlquery string, variables ma
 		for k, v := range pathVars {
 			kword := fmt.Sprintf("[%s]", k)
 			if strings.Contains(sqlquery, kword) {
-				sqlquery = strings.ReplaceAll(sqlquery, kword, fmt.Sprintf("%v", v))
+				// Sanitize the value before replacing
+				vStr := fmt.Sprintf("%v", v)
+				sanitized := ValidSQL(vStr, "colvalue")
+				sqlquery = strings.ReplaceAll(sqlquery, kword, sanitized)
 			}
 			variables[k] = v
 
@@ -690,7 +693,9 @@ func (h *Handler) mergeQueryParams(r *http.Request, sqlquery string, variables m
 		// Replace in SQL if placeholder exists
 		if strings.Contains(sqlquery, kword) && len(val) > 0 {
 			if strings.HasPrefix(parmk, "p-") {
-				sqlquery = strings.ReplaceAll(sqlquery, kword, val)
+				// Sanitize the parameter value before replacing
+				sanitized := ValidSQL(val, "colvalue")
+				sqlquery = strings.ReplaceAll(sqlquery, kword, sanitized)
 			}
 		}
 
@@ -702,7 +707,12 @@ func (h *Handler) mergeQueryParams(r *http.Request, sqlquery string, variables m
 		// Apply filters if allowed
 		if allowFilter && len(parmk) > 1 && strings.Contains(strings.ToLower(sqlquery), strings.ToLower(parmk)) {
 			if len(parmv) > 1 {
-				sqlquery = sqlQryWhere(sqlquery, fmt.Sprintf("%s IN (%s)", ValidSQL(parmk, "colname"), strings.Join(parmv, ",")))
+				// Sanitize each value in the IN clause
+				sanitizedValues := make([]string, len(parmv))
+				for i, v := range parmv {
+					sanitizedValues[i] = ValidSQL(v, "colvalue")
+				}
+				sqlquery = sqlQryWhere(sqlquery, fmt.Sprintf("%s IN (%s)", ValidSQL(parmk, "colname"), strings.Join(sanitizedValues, ",")))
 			} else {
 				if strings.Contains(val, "match=") {
 					colval := strings.ReplaceAll(val, "match=", "")
@@ -743,7 +753,9 @@ func (h *Handler) mergeHeaderParams(r *http.Request, sqlquery string, variables
 
 		kword := fmt.Sprintf("[%s]", k)
 		if strings.Contains(sqlquery, kword) {
-			sqlquery = strings.ReplaceAll(sqlquery, kword, val)
+			// Sanitize the header value before replacing
+			sanitized := ValidSQL(val, "colvalue")
+			sqlquery = strings.ReplaceAll(sqlquery, kword, sanitized)
 		}
 
 		// Handle special headers
@@ -862,17 +874,30 @@ func ValidSQL(input, mode string) string {
 		reg := regexp.MustCompile(`[^a-zA-Z0-9_\.]`)
 		return reg.ReplaceAllString(input, "")
 	case "colvalue":
-		// For column values, escape single quotes
+		// For column values, escape single quotes and backslashes
-		return strings.ReplaceAll(input, "'", "''")
+		result := strings.ReplaceAll(input, "\\", "\\\\")
+		result = strings.ReplaceAll(result, "'", "''")
+		return result
 	case "select":
 		// For SELECT clauses, be more permissive but still safe
 		// Remove semicolons and common SQL injection patterns
-		dangerous := []string{";", "--", "/*", "*/", "xp_", "sp_", "DROP ", "DELETE ", "TRUNCATE ", "UPDATE ", "INSERT "}
+		dangerous := []string{
+			";", "--", "/*", "*/", "xp_", "sp_",
+			"DROP ", "drop ", "Drop ",
+			"DELETE ", "delete ", "Delete ",
+			"TRUNCATE ", "truncate ", "Truncate ",
+			"UPDATE ", "update ", "Update ",
+			"INSERT ", "insert ", "Insert ",
+			"EXEC ", "exec ", "Exec ",
+			"EXECUTE ", "execute ", "Execute ",
+			"UNION ", "union ", "Union ",
+			"DECLARE ", "declare ", "Declare ",
+			"ALTER ", "alter ", "Alter ",
+			"CREATE ", "create ", "Create ",
+		}
 		result := input
 		for _, d := range dangerous {
 			result = strings.ReplaceAll(result, d, "")
-			result = strings.ReplaceAll(result, strings.ToLower(d), "")
-			result = strings.ReplaceAll(result, strings.ToUpper(d), "")
 		}
 		return result
 	default: