2010/7/5 Florian Pflug <fgp(at)phlo(dot)org>:
> On Jul4, 2010, at 13:57 , Pavel Stehule wrote:
>>> I don't really buy that argument. By using a psql variable, you simply move the quoting & escaping business from SQL to the shell where psql is called. True, you avoid SQL injectiont, but in turn you make yourself vulnerable to shell injection.
>> can you show some example of shell injection? For me, this way via
>> psql variables is the best. There are clean interface between outer
>> and inner space. And I can call simply just psql scripts - without
>> external bash.
> Well, on the one hand you have (with your syntax)
> echo "DO (a int := $VALUE) $$ ... $$" | psql
> which allows sql injection if $VALUE isn't sanitized or quoted & escaped properly.
sure - but it is same for you syntax, isn't it? This is classical
dynamic SQL - and more used in from untyped language.
> On the other hand you have
> echo "DO (a int := :value) $$ ... $$$ | psql --variable value=$VALUE
> which allows at least injection of additional arguments to psql if $VALUE contains spaces. You might try to avoid that by encoding value=$VALUE in double quotes, but I doubt that it's 100% safe even then.
[pavel(at)nemesis ~]$ cat y.sh
a='some variable with " ajjaja" jjaja'
b='other variable with "jaja'
psql postgres --variable a="$a" --variable b="$b" --variable c="$c" <<EOT
\echo 'a = ' :'a'
\echo 'b = ' :'b'
\echo 'c = ' :'c'
[pavel(at)nemesis ~]$ sh y.sh
a = 'some variable with " ajjaja" jjaja'
b = 'other variable with "jaja'
c = 'third ''variable'
it is safe - and it is only one really secure way. My design calculate with it
you can do
DO(a int := :'variable') ... and variable is well escaped and value is
casted to int. I am really very happy from :'xxx' feature.
> The point is that interpolating the value into the command is always risky, independent from whether it's a shell command or an sql command.
> best regards,
> Florian Pflug
In response to
pgsql-hackers by date
|Next:||From: Pavel Stehule||Date: 2010-07-05 05:51:56|
|Subject: Implementation of median in PostgreSQL - questions|
|Previous:||From: Takahiro Itagaki||Date: 2010-07-05 02:23:52|
|Subject: Always truncate segments before unlink|