Detecting the use of "curl | bash" server-side

>>rubyn0+(OP)
Neat! But it's not obviously a bad idea. You have a TLS connection with the site you're downloading from. `curl | bash` is no worse than downloading a .dmg or .deb from the same server would be.

>>cjbpri+e2
deb/rpm is better because it's usually signed by maintainer with GPG keys. I think that it's harder to steal keys from maintainer than to infiltrate web server.

>>vbezhe+p2
We came up with a way to do gpg verified curl | bash for ZeroTier. It still works without gpg too. Scroll down to Linux.

https://zerotier.com/download.shtml

>>api+B2
Quote(trying to fit it to narrow widt, for others on mobile):

  curl -s \
  'https://pgp.mit.edu/pks/lookup?op=get&search=0x1657198823E52A61'
  | gpg --import \
  && if z=$(curl -s 'https://install.zerotier.com/' | gpg);
  then echo "$z"
  | sudo bash;
  fi

It's interesting - it tries to import a given gpg key from keyserver, then grabs a gpg armored text file with a bash header - with the gpg header wrapped in a here-document:

  #!/bin/bash
  <<ENDOFSIGSTART=
  -----BEGIN PGP SIGNED MESSAGE-----
  Hash: SHA256

  ENDOFSIGSTART=

I'm unsure, but I think you could just stick your malicious code before the signature?

  #!/bin/bash
  sudo much_evil
  <<ENDOFSIGSTART=
  -----BEGIN PGP SIGNED MESSAGE-----
  Hash: SHA256

  ENDOFSIGSTART=

So it really isn't any better, as far as I can tell. There's also a trade-off between scripts that can be typed (curl https://i.com.com) and need copy-pasting - as copy-pasting also isn't safe - even if that's a somewhat different attack vector (compromising the web site, altering js depending on visitor).

zlacker