Subject: SAP-ABAP (Security and Crime Prevention in SAP)
One of the most common vulnerabilities exploited in SAP systems is improper handling of user inputs. Attackers often exploit poorly validated inputs to perform SQL injection, cross-site scripting (XSS), or unauthorized data manipulation. To prevent such crimes, SAP ABAP developers must enforce strict input validation.
Two primary strategies exist for validating inputs: Whitelisting and Blacklisting. Understanding their differences, benefits, and drawbacks is crucial for secure coding in SAP environments.
Input validation is the process of ensuring that user-supplied data conforms to expected patterns before being processed or stored. It prevents malicious input from compromising system security.
Blacklisting involves defining a list of disallowed characters, words, or patterns and rejecting inputs containing them.
Example: Blocking characters like <, >, ', ; to prevent script injection or SQL injection.
Whitelisting permits only inputs that strictly match a defined pattern or set of acceptable values. All other inputs are rejected.
Example: Allowing only numeric digits for a phone number field, or alphabetic characters for a name.
Given the critical nature of SAP systems and the sophistication of modern attacks, whitelisting is the recommended approach for input validation in ABAP development.
ABAP offers the CL_ABAP_REGEX class for regex-based validation.
DATA: lv_input TYPE string,
lo_regex TYPE REF TO cl_abap_regex,
lo_matcher TYPE REF TO cl_abap_matcher.
lv_input = 'JohnDoe'.
* Define whitelist pattern: only alphabets
lo_regex = cl_abap_regex=>create( pattern = '^[A-Za-z]+$' ).
lo_matcher = lo_regex->create_matcher( text = lv_input ).
IF lo_matcher->find( ) = abap_true.
WRITE: / 'Valid input'.
ELSE.
WRITE: / 'Invalid input'.
ENDIF.
For fields with fixed options, check input against a predefined list.
DATA: lt_allowed_values TYPE TABLE OF char10,
lv_input TYPE char10.
lt_allowed_values = VALUE #( ( 'ADMIN' ) ( 'USER' ) ( 'GUEST' ) ).
lv_input = 'ADMIN'.
READ TABLE lt_allowed_values WITH KEY table_line = lv_input TRANSPORTING NO FIELDS.
IF sy-subrc = 0.
WRITE: / 'Valid input'.
ELSE.
WRITE: / 'Invalid input'.
ENDIF.
Blacklisting attempts like replacing < or > characters can be bypassed by encoding or Unicode tricks. For example, malicious inputs using URL encoding %3C or HTML entities can slip through.
| Aspect | Whitelisting | Blacklisting |
|---|---|---|
| Approach | Allow only known good inputs | Block known bad inputs |
| Security | Higher security | Lower, prone to bypass |
| Maintenance | Lower once defined | High, needs constant updates |
| User Experience | May be restrictive | May allow some malicious input |
| Implementation | Requires precise definitions | Easier to start but less safe |
For secure SAP ABAP development and crime prevention, whitelisting input validation is the best practice. It provides a robust defense against injection attacks and other input-based vulnerabilities by strictly enforcing acceptable input patterns.
While blacklisting can be a quick fix for known threats, it is insufficient against evolving attack techniques. SAP developers should invest in defining and implementing effective whitelisting strategies to protect SAP systems from security breaches and malicious activities.