Function Modules (FMs) are a fundamental building block in SAP ABAP development, encapsulating reusable code to perform business logic, data processing, or system interactions. However, insecure use or design of function modules can expose SAP systems to various security risks, including SAP-ABAP crimes like unauthorized data access, privilege escalation, and data manipulation.
This article discusses best practices for securely using and developing function modules to protect SAP systems from abuse and maintain data integrity.
Function modules, if not properly secured, can be exploited in multiple ways:
Every function module performing sensitive operations must include explicit AUTHORITY-CHECK statements for relevant authorization objects.
AUTHORITY-CHECK OBJECT 'Z_SALES_AUTH'
ID 'ACTVT' FIELD '03'
ID 'VKORG' FIELD iv_sales_org.
IF sy-subrc <> 0.
MESSAGE 'Not authorized to perform this action' TYPE 'E'.
ENDIF.
This prevents bypassing security by direct calls from unauthorized programs or users.
Never trust input data blindly. Always check parameter values against expected formats, ranges, and existence.
IF iv_customer_id IS INITIAL OR NOT cl_abap_regex=>matches( iv_customer_id, '^\d{10}$' ).
MESSAGE 'Invalid customer ID' TYPE 'E'.
ENDIF.
Input validation helps prevent injection attacks and unexpected system behavior.
Leverage SAP’s built-in function modules which follow strict security guidelines instead of creating custom solutions from scratch.
Only return sensitive data from function modules if absolutely necessary, and ensure the caller is authorized.
Function modules should be designed to avoid unwanted side effects or implicit changes to global data, minimizing the risk of unpredictable behavior exploitable by attackers.
Robust error handling prevents leaking internal system information and supports security monitoring.
TRY.
" FM call
CATCH cx_sy_authorization INTO DATA(lx_auth).
MESSAGE 'Authorization failure' TYPE 'E'.
ENDTRY.
Log security-relevant events such as failed authorization attempts for forensic purposes.
Restrict access to function modules in transaction SE93 or via roles using authorization object S_FUNC.
Function modules are powerful tools in SAP ABAP development but require careful security considerations to prevent SAP-ABAP crimes. By embedding authorization checks, validating inputs, limiting sensitive data exposure, and controlling access, organizations can secure their SAP environments effectively.
Secure function module practices not only protect critical business data but also uphold compliance and trust across the enterprise.