.NET/Java PDF, Tiff, Barcode SDK Library

The HASHED implementation simply converted the OBJECT_ID passed into the query into a FILE/BLOCK to be read and read it no index. The HEAP table, however, had to do two I/Os on the index for each row. The cr=2 in the TKPROF Row Source Operation line shows us exactly how many consistent reads were done against the index. Each time I looked up OBJECT_ID = :B1, Oracle had to get the root block of the index and then find the leaf block containing the location of that row. Then, I had to take the leaf block information, which included the ROWID of that row, and access that row in the table for a third I/O. The HEAP table did three times the I/O of the HASHED implementation. The points of interest here are as follows: The hash cluster did significantly less I/O (query column). This is what we anticipated. The query simply took the random OBJECT_IDs, performed the hash on them, and went to the block. The hash cluster has to do at least one I/O to get the data. The conventional table with an index had to perform index scans followed by a table access by rowid to get the same answer. The indexed table has to do at least three I/Os in this case to get the data.

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The two most important are stdcall, which is the convention used by Windows APIs (and many others DLLs), and cdecl, which is the convention used by the C language Other implementations of the runtime may provide additional conventions to the user In the PInvoke design, there is nothing restricting the supported conventions to these two (and in fact the runtime uses the fcall convention for invoking services provided by the runtime from managed code)..

1 row created ops$tkyte%ORA11GR2> commit; Commit complete The pw table looks like a pretty important table, but remember, users do not know it exists However, they do have access to the INJ routine: ops$tkyte%ORA11GR2> grant execute on inj to scott; Grant succeeded So the evil developer/user, can simply execute: scott%ORA11GR2> alter session set 2 nls_date_format = '"''union select tname,0,null from tab--"'; Session altered scott%ORA11GR2> exec ops$tkyteinj( sysdate ) select * from all_users where created = ''union select tname,0,null from tab--' USER_PW.... PL/SQL procedure successfully completed Now, that NLS_DATE_FORMAT is interesting most people don t even know you can include character string literals with the NLS_DATE_FORMAT (Heck, many people don t even know you can change the date format like that even without this trick.

) What the malicious user did here was to trick your code into querying a table you did not intend him to query using your set of privileges The TAB dictionary view limits its view to the set of tables the current schema can see When users run the procedure, the current schema used for authorization is the owner of that procedure (you, in short, not them) They can now see what tables reside in that schema They see that table USER_PW and say hmmm, sounds interesting So, they try to access that table: scott%ORA11GR2> select * from ops$tkyteuser_pw; select * from ops$tkyteuser_pw * ERROR at line 1: ORA-00942: table or view does not exist The malicious user can t access the table directly; he lacks the SELECT privilege on the table Not to worry, however, there is another way.

The additional information required to perform the function call is provided by custom attributes that are used to decorate a function prototype and inform the runtime about the signature of the exported function.

The user wants to know about the columns in the table Here s one way to find out more about the table s structure: scott%ORA11GR2> alter session set 2 nls_date_format = '"''union select tname||cname,0,null from col--"'; Session altered scott%ORA11GR2> exec ops$tkyteinj( sysdate ) select * from all_users where created = ''union select.

tname||cname,0,null from col--' USER_PWPW..... USER_PWUNAME..... There we go, we know the column names. Now that we know the table names and the column names of tables in that schema, we can change the NLS_DATE_FORMAT one more time to query that table not the dictionary tables. So the malicious user can next do the following: scott%ORA11GR2> alter session set 2 nls_date_format = '"''union select uname,0,null from user_pw--"'; Session altered. scott%ORA11GR2> exec ops$tkyte.inj( sysdate ) select * from all_users where created = ''union select uname,0,null from user_pw--' TKYTE..... PL/SQL procedure successfully completed. scott%ORA11GR2> alter session set 2 nls_date_format = '"''union select pw,0,null from user_pw--"'; Session altered. scott%ORA11GR2> exec ops$tkyte.inj( sysdate ) select * from all_users where created = ''union select pw,0,null from user_pw--' TOP SECRET..... PL/SQL procedure successfully completed. And there we go that evil developer/user now has your sensitive username and password information. How could you have protected yourself By using bind variables. For example: ops$tkyte%ORA11GR2> create or replace procedure NOT_inj( p_date in date ) 2 as 3 l_rec all_users%rowtype; 4 c sys_refcursor; 5 l_query long; 6 begin 7 l_query := ' 8 select * 9 from all_users 10 where created = :x'; 11 12 dbms_output.put_line( l_query ); 13 open c for l_query USING P_DATE; 14 15 for i in 1 .. 5

This section starts with a simple example of a DLL developed using C++ to which you will add code during your experiments using PInvoke. The CInteropDLL.h header file declares a macro defining the decorations associated with each exported function: #define CINTEROPDLL_API __declspec(dllexport) extern "C" { void CINTEROPDLL_API HelloWorld(); } The __declspec directive is specific to the Microsoft Visual C++ compiler, and other compilers may provide different ways to indicate the functions that must be exported when compiling a DLL.