system versus qx security

[mce]

Hi All,

I might be totally wrong about this issue, but here if goes.
It is a security issue when using shell escapes (in CGI).
I have a program like

my $cmd="ls";
my $arg1=" file; ls";
my $arg2=" file";
 
system($cmd,$arg1,$arg2);
warn qx/$cmd $arg1 $arg2/;
warn `$cmd $arg1 $arg2`;

This generates this output
ls: file; ls: No such file or directory
ls: file: No such file or directory
file
file
file
file
When using the system command, if 'qoutes' the arguments, which is more safe in CGI. But how do I do this in qx or <backtick>? I can use quotemeta, but isn't there a better solution?

What I want to achieve, is to capture the output of a command, which system will not allow.

Any suggestions?
---------------------------
Dr. Mark Ceulemans
Senior Consultant
BMC, Belgium

[zby]

Actually what the system function is doing is not 'quoting' the parameters but directly supplying them to the OS exec call.

Note that argument processing varies depending on the number of arguments. If there is more than one argument in LIST, or if LIST is an array with more than one value, starts the program given by the first element of the list with arguments given by the rest of the list. If there is only one scalar argument, (...)

While qx supplies the command to the shell for parsing for arguments. And this happens in the 'only one scalar argument' case above too (which I cut out for brevity).

You might try to look at IPC::Open2 or IPC::Open3 functions. They can be called in simmilar fashions as system.

[Jenda]

If such a call exists. Under some OSes it does quote parameters (and then crosses fingers). It's true though that the shell is not involved in system($cmd,@params).

Edit by castaway: Closed small tag in signature