On 2024-08-30 19:18:29 +0000, Simon Connah via Python-list wrote: > I need to write a script that will take some user input (supplied on a > website) and then execute a Python script on a host via SSH. I'm > curious what the best options are for protecting against malicious > input in much the smae way as you sanitise SQL to protect against SQL > injections.
(Aside: Don't "sanitize" SQL. Use placeholders.) > I could do it either on the website itself or by doing it on the host > machine. You will have to do it in the web site. The SSH manual states: | If supplied, the arguments will be appended to the command, separated by | spaces, before it is sent to the server to be executed. So whether you call ssh myhost print_args a b c or ssh myhost print_args a "b c" in both cases exactly the same string will be sent to myhost, and it won't have any chance to distinguish them. So you will either have to filter ("sanitize") the arguments or properly quote them before invoking SSH. > If someone has any suggestions I'd appreciated it. If you need more > information then please let me know. First, if there is any chance that your arguments can contain characters with meaning to the shell (like an apostrophe in a name), get the quoting correct. If you can, transmit those arguments in a different way (e.g. as input, maybe just nul-separated, may as JSON, or whatever). That removes the SSH-specific problems. There may still be problems with the python script on the host. Then, do all the validation you can on the web server. Reject all requests which aren't valid. But be sure to check against the relevant specifications, not your prejudices (You may not think that an apostrophe in an email address is valid, but it is). Include meaningful error messages (not just "input invalid"). Helping your legitimate users is more important than slightly inconveniencing an attacker. hp -- _ | Peter J. Holzer | Story must make more sense than reality. |_|_) | | | | | h...@hjp.at | -- Charles Stross, "Creative writing __/ | http://www.hjp.at/ | challenge!"
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