[PATCH] treewide: more portable bash shebangs

[Jordan Glover]

On Tuesday, July 16, 2019 10:08 PM, Jörg Thalheim <joerg at higgsboson.tk> wrote:

> On 16/07/2019 18.32, Jordan Glover wrote:
>
> > On Tuesday, July 16, 2019 12:21 PM, Jörg Thalheim joerg at higgsboson.tk wrote:
> >
> > > While /usr/bin/env is more or less available on all POSIX systems
> > > /bin/bash might not be. This is particular the case on NixOS and the BSD
> > > family (/usr/local/bin/bash). Downstream packagers would often rewrite
> > > those shebangs back automatically as they can rely on absolute paths
> > > but having portable shebangs in the repository helps to run the code
> > > without any further modification.
> >
> > The reason almost everyone hardcodes bash to /bin/bash is the potential
> > environment attack where someone create malicious "bash" and export it in PATH:
> > https://developer.apple.com/library/archive/documentation/OpenSource/Conceptual/ShellScripting/ShellScriptSecurity/ShellScriptSecurity.html
> > Obviously wg scripts are handling quite sensitive data like private keys...
> > Seriously if you except that downstream packagers would rewrite it back to
> > /bin/bash then why the others can't rewrite it to /usr/bin/env bash right
> > now if this is something they want?
> > Jordan
>
> This argument does not apply here since all commands internally could
> be redirected by a PATH change as well since the PATH is not set in the scripts.

Yep, that's something to actually fix as you won't fix things by making it worse.

> I am also not quite sure what threat model here is?
> The scripts changed here are not designed to run from a CGI context
> and are not hardened for that purpose.
> The idea is that you can run the scripts unmodified from the repository
> without having to alter the files, which is convenient for development w.r.t to git.

Then simply run "bash <script.sh>" and call it a day.

Jordan