Re: [GENERAL] Security implications of (plpgsql) functions

[ Thread moved to hackers.]

Crash reproduced here.

My guess is that you are recursing and crashing the backend, which then
forces the other backends to reset. I think we need to fix this by
either setting a limit in the amount of function recursion, or allowing
only the offending backend to crash without forcing all the other
backends to crash.

---------------------------------------------------------------------------

Marcin Owsiany wrote:
> CREATE FUNCTION "x" (integer) RETURNS integer AS '
> BEGIN
> RETURN x(0);
> END' LANGUAGE 'plpgsql' WITH ( isstrict );
> SELECT x(0);
> server closed the connection unexpectedly
> This probably means the server terminated abnormally
> before or while processing the request.
> The connection to the server was lost. Attempting reset: Failed.
> !>
>
> The log says:
> DEBUG: server process (pid 3550) was terminated by signal 11
> DEBUG: terminating any other active server processes
>
> The thing that worries me most is the last message: postmaster terminates all
> other backends, therefore overflowing the stack via a plpgsql function can be
> used to DoS-attack the server.
>
> Is there anything one (as a postgresql installation admin) can do? Disabling
> procedural languages in databases of the users I don't trust comes to mind, but
> does it really make me safe? I mean: won't such attack still be possible with
> pure SQL?
>
> regards,
>
> Marcin
> --
> Marcin Owsiany <marcin(at)owsiany(dot)pl> http://marcin.owsiany.pl/
> GnuPG: 1024D/60F41216 FE67 DA2D 0ACA FC5E 3F75 D6F6 3A0D 8AA0 60F4 1216
>
> "Every program in development at MIT expands until it can read mail."
> -- Unknown
>
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