Please bear with my dumb ass. if validating a certificate / signature is risking an RCE, does that essentially make this a planet-wide potential supply chain hack (wherever gnupg is used, at least?)
Follow up: I suppose the verification could be done in a container?
Wearing a dog collar for a highly technical live presentation of a critical security feature requires a degree of personal confidence I can only admire.
I’m probably having a brainfart (watched the video during insomnia), but re: the section 12m 10s into the video, can someone please clarify why “the instructions are dangerously wrong”?
I understand it relates to the earlier demo in which those instructions gave the illusion of “verifying” an ISO that was in fact malicious. But:
- why did those instructions fail to genuinely verify the ISO?
- what would the correct instructions have been?
Cleatext signing (having the signature and data in the same file) is broken in many ways. It is possible to put unsigned data at the top of the file in a way that sha256sum will use it. Watch the 39c3 GPG talk if your interested in the gory details.
The solution is to use detached signatures (checksum.txt and checksum.txt.gpg to verify that). This makes sure that all of checksum.txt is actually covered by the signature.
cc @[email protected]
or, binary signatures, [which I prefer: compressionable], as textfiles are insecure formats.I prefer a headed, mided, and tailed verification, similar to MPEG keyframing, for constant stream verification.
idk about the specific formats, but i don’t think you can say that in general. what are those two formats and why does it make a difference in this case?
- what binary signatures offer:
- smaller sizes
- ability to compression
- the actually signature
- confidentiality
-
File headersdef, midingdef, tailingdef.
i don’t think you can say that in general
What is your academic literacy please?
Cite your papers please.
or gen z:
Drop your academic flex.
What grade you at?
papers pls🙏
no, i mean, you say text files are insecure and you prefer binary.
while it is true that processing text files needs additional code (validating/converting charsets/encoding), which increases the number of potential attack vectors, security threats introduced by this are not a fault of them being text, but of the parser code.
at the end of the day the attacker just switches from text editor to hex editor to prepare a malicious file.
I was never talking about vectorization, but regular file integrity. Textfiles have no error correctiveness. Yet a binary can be. Either can be edited and vectorized. Heck the point of this talk is manipulating expectations, as
sha256sumisn’t file verifier.yeah, but nobody stops you from adding error correctiveness. you could for example just put the whole thing three times with a seperator.
however there’s also an important point for text files: you can post them wherever you can write text messages. being able to digitally sign them even adds to your freedom, as you can post anonymously and your readers are able to verify it’s from the same source. like you could post your heated political manifesto or cousin incest smut on 4chan or some darknet forum and if you later make a part 2, ppl will be able to tell you apart from imposters.
Lexi Groves is quoting Fedora’s own mailing list irt social engineering. Both Fedora’s instructions are wrong, and the method to properly verify ISO, that to be brutal, should have been outdated decades ago, is “dangerously wrong.” It’s a nice gibe.
