Re: How does one make the following psql statement sql-injection resilient?

On 3/16/2015 4:30 PM, David G. Johnston wrote:
> psql "$SERVICE" \
>       --echo-queries \
>       --set=string_input="${1:-ok_to_return}" \
>       --set=start="${2:-5}" \
>       --set=end="${3:-10}" \
> <<'SQL'
>      SELECT idx
>          FROM generate_series(1, 20) gs (idx)
>          WHERE 'short-circuit' != :'string_input'
>          AND idx BETWEEN :start AND :end;
> SQL
>
> # (6 rows)
>
> --set=end="${3:-10 AND false}"
>
> # (0 rows)
>
> Am I forced to represent the input as text (using :'end') and then
> perform a conversion to integer?
>
> Thanks!
>
> David J.
>


The --set's make it a little complicated.  How about:

string_input="${1:-ok_to_return}"
start="${2:-5}"
end="${3:-10}"

psql "$SERVICE" --echo-queries <<'SQL'
  prepare tmp as SELECT idx
          FROM generate_series(1, 20) gs (idx)
          WHERE 'short-circuit' != $1
          AND idx BETWEEN $2 AND :$3;

   execute tmp($string_input, $start, $end);
   deallocate tmp;
SQL

That's untested, and probably wont work.  The "execute tmp($1, $2, $3)"
need to be passed to psql as-is, but $string_input, $start and $end need
to be replaced in bash before its sent to psql.  Maybe use \$1?

Docs here:

http://www.postgresql.org/docs/9.4/static/sql-prepare.html


-Andy