Don't Pipe to your Shell

Re:Don't Pipe to your Shell by bryanlarsen on Thursday October 31, 2013 @10:45PM (#6651525)

Those scripts are typically very short. They'll either download completely or not at all. And if they do abort short then what are the chances that it's going to do it in exactly the wrong place? And then you have to manage to kill the wrong process to start the aborted script.

Statistically a cosmic ray flips a few bits in your RAM every year. Theoretically those bit flips could transform a benign program into a malicious one, and I'm sure that's happened to somebody somewhere sometime.

But it's very unlikely to happen to you tomorrow. You could use ECC RAM to prevent this from happening, but how many people do that?

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Re:Don't Pipe to your Shell by FiloSottile on Thursday October 31, 2013 @11:13PM (#6651584)

Again, here is the counter-point of the author

> This might be unlikely, but the results of this happening, even once, could be catastrophic.

Also, you don't have to kill any process, that was a PoC by the author. The scenario is a connection drop.

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Re:Don't Pipe to your Shell by codezero on Friday November 01, 2013 @12:08AM (#6651710)

Counterpoint to the author: have you ever heard of anyone ever having anything catastrophic happen because of this, ever? Have you ever heard of anyone even having it fail with garbage?

I haven't.

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Re:Don't Pipe to your Shell by mikegirouard on Friday November 01, 2013 @01:22AM (#6651942)

Catastrophic? I can't claim that. But I can tell you that I had a server drop out on me when installing software this way. Here's a quick quote of the bug report I sent to Linode when I was installing Longview.

    > Bug: Update the nginx (?) error pages to be bash friendly
    > 
    > root@marius ~]# curl -s https://lv.linode.com/nGiB | sudo bash
    > bash: line 1: html: No such file or directory
    > bash: line 2: syntax error near unexpected token `<'
    > 'ash: line 2: `<head><title>502 Bad Gateway</title></head>
    > 
    > This could be done by just dumping out echo statements since its already
    > being parsed by the shell. Additional meta about the request (headers,     etc)
    > could be dumped into comments too…
    > 
    > # 502 Bad Gateway
    > echo 
    > echo "Uh oh: Something went sideways during the install!"
    > echo "("
    > echo "Re-running the installer should clear things up."
    > echo 
    > echo " sudo !!"
    > echo

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Re:Don't Pipe to your Shell by codezero on Friday November 01, 2013 @01:25AM (#6651957)

Yep, I agree this is generally bad practice and is prone to error conditions, but I am mainly addressing the article since it is claiming that this should never be done because of the possible catastrophic consequences, and I just don't think that scenario is likely enough to mount a campaign to abolish this practice :)

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Re:Don't Pipe to your Shell by hrjet on Friday November 01, 2013 @03:45AM (#6652387)

How many would talk about a catastrophic failure that was caused because of their stupidity.

Many wouldn't.

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Re:Don't Pipe to your Shell by mikeash on Friday November 01, 2013 @09:45AM (#6653637)

You're right, let's ignore completely realistic failure modes just because nobody's had it happen yet.

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Re:Don't Pipe to your Shell by cbsmith on Saturday November 02, 2013 @12:39AM (#6658175)

No. If the connection drops, wget will retry forever iff you have Content-Length in the HTTP response, which you always do.

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