One criticism of Windows was folks being encouraged (by websites) to download custom .exe file to Desktop and double click.

In response to this, a wave a security products and some access control changes, put a stop to that.

Some users missed the convenience.

Could this ever happen on Linux / Unix?


Here is an extract from the install instructions for a Google publicised project:

curl -L | bash

Seems the nix community is in too great a hurry to put convenience before security.

I point out some of the reasons why not in the next section.

Internet pipe to Bash – why not?

To suggest such an install procedure, is to ignore many of the security lessons from the past decade.

Possible risks 1: Fat fingered redirect

By advising the user invoke curl with -L flag, the developer is encouraging users to trust any locally coded redirection.

The reason curl advises of redirection is to allow the end user to verify any redirection themselves rather than trusting what redirection is entered at the remote site.

What would happen if a bogus redirect was inserted by mistake, or by a malicious insider? If it only happened for an hour would the company think it important enough to inform the developer population?

Possible risks 2: Shifting sands

Exactly how do you personally know that the code that was there yesterday is the same code as today?

Does it come in a package with checksums and a well understood inbuilt verification of checksum feature?

Can you manually download a verification checksum from a different mirror server, than the actual code download?

Possible risks 3: Compromised server

Compromised servers are always a risk for any internet hosted software.

Hosting code through acceptance in a distribution like Debian or Red Hat, allows a small company to leverage the infrastructure provided.

It also elevates untrusted software somewhat, due to the integration build process, qa review, and hosting infrastructure which such distributions provide.

Bitbucket, Gitorious, Google code and Github offer some minor improvement from self hosting a project yourself.

Then there is Pypi, CPAN, and other convenience collections, which whilst not offering massive assurance, at least mitigate the next problem described.

Possible risks 4: Dns hijack / redirection

Dns cache poisoning is all too common unfortunately.

Whilst this project is getting some backing from Google, it would be unwise to assume that it (and any mirrors?) employ DNSSEC to mitigate Cache poisoning. If they did employ DNSSEC effectively, would that be on the original http endpoint or the redirected http endpoint?

Commentary and other examples:

In fairness to the developers, there are some additional install notes, and in particular there is some hints for Debian / Ubuntu folks that include this line:

sudo npm install -g yeoman

However, those install instructions also suggest at the start, that you should still do an initial pipe bash, in case you had a previous install present.

Doing that initial pipe bash, then switching to more traditional package management techniques, does not mitigate any of the risks described earlier.

It may be that developers are being encouraged to do this sort of hacky curl stuff by seeing this entry from the npm site:

curl | sh

The observant amongst you will notice that there is no -L flag here, so strike off one of those risks listed earlier.

What comes after the pipe symbol ( | )? Does that make any difference from the other example?

That answer is left as an exercise for the reader.

Further examples (added after article first written):