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ABAP Keyword Documentation →  ABAP - Security Notes →  Security Risks Caused by Input from Outside →  SQL Injections 

SQL Injections Using Dynamic Tokens

The ABAP SQL syntax allows almost every clause of an ABAP SQL statement to be specified dynamically as the content of a data object specified in parentheses. If all of part of the content of one of these data objects originates from outside of the program, there is a risk of one of the following SQL injections:

Other versions: 7.31 | 7.40 | 7.54


Note

In a dynamic token, it is more secure to specify the name of an ABAP data object as an operand, instead of entering a value as a literal.


Example

The first dynamic WHERE condition is insecure compared to an SQL injection, if input is an external input, which is not checked or masked beforehand. This is not necessary for the second dynamic WHERE condition.

DATA(sql_cond1) = `CARRID = '` && input && `'`.
SELECT SINGLE * FROM scarr WHERE (sql_cond1) INTO @wa.

DATA(sql_cond2) = `CARRID = @input`.
SELECT SINGLE * FROM scarr WHERE (sql_cond2) INTO @wa.

Access to Non-Permitted Database Tables

If dynamically specified database tables source_syntax (for the statement SELECT or target_syntax for writes) originate in full or in part from outside the program, users could potentially access databases for which they usually do not have authorization. If the use of external input in dynamically specified database tables is unavoidable, the input must be properly checked. For example, the class CL_ABAP_DYN_PRG can be used to make a comparison with a whitelist.


Example

In the following program section, the method CHECK_TABLE_NAME_STR only allows access to tables of the flight data model. Input from other or nonexistent database tables are rejected. Access to oversized database tables is also not allowed, to avoid putting too much strain on system performance.

DATA dbtab TYPE string. 
cl_demo_input=>request( CHANGING field = dbtab ). 

TRY. 
    dbtab = 
      cl_abap_dyn_prg=>check_table_name_str( 
        val = to_upper( dbtab ) 
        packages = 'SAPBC_DATAMODEL' ). 
  CATCH cx_abap_not_a_table cx_abap_not_in_package. 
    cl_demo_output=>display( 'Wrong input' ). 
    LEAVE PROGRAM. 
ENDTRY. 

DATA dref TYPE REF TO data. 
FIELD-SYMBOLS <fs> TYPE STANDARD TABLE. 
CREATE DATA dref TYPE STANDARD TABLE OF (dbtab) 
                 WITH EMPTY KEY. 
ASSIGN dref->* TO <fs>. 

DATA lines TYPE i. 
SELECT COUNT(*) 
       FROM (dbtab) 
       INTO (@lines). 
IF lines > 1000. 
  cl_demo_output=>display( 'Table too large' ). 
  LEAVE PROGRAM. 
ENDIF. 

SELECT * 
       FROM (dbtab) 
       INTO TABLE @<fs>. 
cl_demo_output=>display( <fs> ).

Access to Non-Permitted Table Columns

If the dynamically specified table columns column_syntax in the SELECT list of the statement SELECT originate fully or in part from outside the program, users could potentially access table columns for which they usually do not have authorization. Users could also rename columns without permission or use aggregate functions to perform unauthorized calculations. If the use of external input in a dynamically specified table columns is unavoidable, the input must be properly checked. For example, the class CL_ABAP_DYN_PRG can be used to make a comparison with a whitelist.


Note

When specifying columns after GROUP BY, the same security advice applies as to columns specified dynamically directly after SELECT.


Example

See the example in column _syntax. Here only columns from a whitelist are permitted to be read.

Manipulation of the Dynamic WHERE Condition

If a dynamic WHERE condition cond_syntax originates completely or partially from outside the program, then users could potentially access data for which they usually do not have authorization. If the use of external input in a dynamic WHERE condition cannot be avoided, the input must be properly checked and usually masked as well. To do this, you can sue the methods of class CL_ABAP_DYN_PRG.


Note

When dynamically specifying a HAVING condition, the same security advice applies as for the dynamic WHERE condition.


Example

In the following program section, a potential SQL injection is prevented by using the method QUOTE of the class CL_ABAP_DYN_PRG, which adds quotation marks at the beginning and end. If this method is not used, and if "x' OR name <> '" is entered, for example, all the data in the SCUSTOM table would be displayed.

DATA name TYPE string. 
DATA customers TYPE TABLE OF scustom WITH EMPTY KEY. 

cl_demo_input=>request( CHANGING field = name ). 

DATA(cond) = `country = 'DE' AND name = ` && 
             cl_abap_dyn_prg=>quote( name ). 

TRY. 
    SELECT * FROM scustom 
             WHERE (cond) 
             INTO TABLE @customers. 
    cl_demo_output=>display( customers ). 
  CATCH cx_sy_dynamic_osql_syntax. 
    cl_demo_output=>display( 'Wrong input' ). 
ENDTRY.

More examples under dynamic WHERE condition.

Manipulation of a Dynamic Change Expression

If a dynamic change expression expr_syntax (for the statement UPDATE) originates completely or partially from outside the program, then users could potentially change data for which they usually do not have authorization. If the use of external input in a dynamic change expression cannot be avoided, the input must be properly checked and usually masked as well. To do this, you can sue the methods of class CL_ABAP_DYN_PRG.


Example

In the following program section, a potential SQL injection is prevented by using the method QUOTE of the class CL_ABAP_DYN_PRG, which adds quotation marks at the beginning and end. If this method is not used, and if "...' discount = '90", for example, is entered in one of the input fields, the discount for the relevant customer would be set to 90.

DATA in TYPE REF TO if_demo_input. 

DATA customer TYPE scustom. 

DATA: id TYPE scustom-id, 
      name     TYPE string, 
      street   TYPE string, 
      city     TYPE string, 
      postcode TYPE string. 

id = '00000001'. 
SELECT SINGLE * 
       FROM scustom 
       WHERE id = @id 
       INTO @customer. 

name    = customer-name. 
street  = customer-street. 
city    = customer-city. 
postcode = customer-postcode. 

in = cl_demo_input=>new( ). 
in->add_field( CHANGING field = name 
 )->add_field( CHANGING field = street 
 )->add_field( CHANGING field = city 
 )->add_field( CHANGING field = postcode 
 )->request( ). 

DATA(set_expr) = 
  COND string( WHEN name IS NOT INITIAL 
               THEN ` NAME = ` && 
               cl_abap_dyn_prg=>quote( name ) ) && 
  COND string( WHEN street IS NOT INITIAL 
               THEN ` STREET = `   && 
               cl_abap_dyn_prg=>quote( street ) ) && 
  COND string( WHEN city IS NOT INITIAL 
               THEN ` CITY = ` && 
               cl_abap_dyn_prg=>quote( city ) ) && 
  COND string( WHEN postcode IS NOT INITIAL 
               THEN ` POSTCODE = ` && 
               cl_abap_dyn_prg=>quote( postcode ) ). 

TRY. 
    UPDATE scustom SET (set_expr) WHERE id = @id. 
  CATCH cx_sy_dynamic_osql_syntax. 
    cl_demo_output=>display( 'Wrong input' ). 
ENDTRY.