I’ve heard this over and over… what’s the difference security-wise between sudo running some install script and sudo installing a .deb (or whatever package format) ?
@gomp try comparing it with apt install, not with downloading a .deb file from a random website - that is obviously also very insecure. But the main thing curl|sh will never have is verifying the signature of the downloaded file - what if the server got compromised, and someone simply replaced it. You want to make sure that it comes from the actual author (you still need to trust the author, but that’s a given, since you are running their code). Even a signed tarball is better than curl|sh.
If you have a pre-shared trusted signature to check against (like with your distro’s repos), yes. But… that’s obviously not the case since we are talking installing software from the developer’s website.
Whatever cryptografic signature you can get from the same potentially compromised website you get the software from would be worth as much as the usual md5/sha checksums (ie. it would only check against transmission errors).
That would be “a pre-shared trusted signature to check against”, and is seldom available (in the real world where people live - yes, there are imaginary/ideal worlds where PGP is widespread and widely used) :)
My bad for causing confusion: when I wrote “trusted signature” I should have said “trusted public key”.
The signatures in an apt repo need to be verified with some public key (you can think of signatures as hashes encrypted with some private key).
For the software you install from your distro’s “official” repo, that key came with the .iso back when you installed your system with (it may have been updated afterwards, but that’s beyond the point here).
When you install from third-party repos, you have to manually trust the key (IIRC in Ubuntu it’s something like curl <some-url> | sudo apt-key add -?). So, this key must be pre-shared (you usually get it from the dev’s website) and trusted.
@gomp Yes but the point is that it comes from a different place and a different time, so for you to execute a compromised program, it would have to be compromised for a prolonged time without anyone else noticing. You are protected by the crowd. In curl|sh you are not protected from this at all
A deb is just a zip file that gets unpacked to where your binaries go. A shell script you curl pipe into shell could contain literally any instructions
Binary packages have scripts (IIRC for .deb they are preinst/postinst to be run before/after installation and prerm/postrm before/after removal) that are run as root.
BTW the “unzip” part is also run as root, and a binary package can typically place stuff anywhere in your system (that’s their job after all)… even if you used literal zip files they could still install a script in ways that would cause the OS to execute it.
I’ve heard this over and over… what’s the difference security-wise between sudo running some install script and sudo installing a .deb (or whatever package format) ?
@gomp try comparing it with
apt install, not with downloading a .deb file from a random website - that is obviously also very insecure. But the main thingcurl|shwill never have is verifying the signature of the downloaded file - what if the server got compromised, and someone simply replaced it. You want to make sure that it comes from the actual author (you still need to trust the author, but that’s a given, since you are running their code). Even a signed tarball is better than curl|sh.Installing a .deb is what I was thinking about.
If you have a pre-shared trusted signature to check against (like with your distro’s repos), yes. But… that’s obviously not the case since we are talking installing software from the developer’s website.
Whatever cryptografic signature you can get from the same potentially compromised website you get the software from would be worth as much as the usual md5/sha checksums (ie. it would only check against transmission errors).
@gomp Why would you be taking the signature from the same website? Ever heard of PGP key servers?
That would be “a pre-shared trusted signature to check against”, and is seldom available (in the real world where people live - yes, there are imaginary/ideal worlds where PGP is widespread and widely used) :)
@gomp You mean, as seldom available as every
apt installever? https://superuser.com/a/990153My bad for causing confusion: when I wrote “trusted signature” I should have said “trusted public key”.
The signatures in an apt repo need to be verified with some public key (you can think of signatures as hashes encrypted with some private key).
For the software you install from your distro’s “official” repo, that key came with the .iso back when you installed your system with (it may have been updated afterwards, but that’s beyond the point here).
When you install from third-party repos, you have to manually trust the key (IIRC in Ubuntu it’s something like
curl <some-url> | sudo apt-key add -?). So, this key must be pre-shared (you usually get it from the dev’s website) and trusted.@gomp Yes but the point is that it comes from a different place and a different time, so for you to execute a compromised program, it would have to be compromised for a prolonged time without anyone else noticing. You are protected by the crowd. In curl|sh you are not protected from this at all
A deb is just a zip file that gets unpacked to where your binaries go. A shell script you curl pipe into shell could contain literally any instructions
Binary packages have scripts (IIRC for .deb they are preinst/postinst to be run before/after installation and prerm/postrm before/after removal) that are run as root.
BTW the “unzip” part is also run as root, and a binary package can typically place stuff anywhere in your system (that’s their job after all)… even if you used literal zip files they could still install a script in ways that would cause the OS to execute it.
Yeah I’m over simplifying on purpose here. The bottom line is piping into
shis dangerous