101 pointsby ledoge9 hours ago11 comments
  • philsnow2 minutes ago
    It's so insane to have PDF programs doing their own encryption, not because "don't roll your own crypto" (although yes for that reason too), but because the people who write PDF programs (libraries, viewers, general-purpose tools like qpdf, etc etc) aren't (necessarily) going to be great at understanding or designing good encryption UX.

    Also, I get that a lot of sensitive information is exchanged with PDFs these days, but why should PDFs have encryption built-in to the file format? Sensitive information is also exchanged in image files, word documents, zip files, html, etc etc etc etc. If you take all the work that goes into making the crypto UX decent for one kind of file and apply that to "all files", then each ecosystem doesn't have to invent their own.

    This is just like "high-end" car manufacturers insisting on making their own software, and not integrating apple carplay. They're either going to make a truly shitty podcast app, or they're not even going to bother and instead tell people to use bluetooth to listen to podcasts like it's 2006.

  • tptacek7 hours ago
    "MuPDF versions before 1.28.5 use an implementation of the drand48 family" yeah, ok, so they're basically not doing real encryption. The number of bits in the key space isn't the real story; the keys simply aren't cryptographically random.
    • somat4 hours ago
      You could do what openbsd did and tie all the traditional weak psudorandom interfaces into a cryptographically secure one. it will still match the drand48() interface. I still don't think I would use them for secure things but now rand() is actually random. http://man.openbsd.org/drand48

      Another pet peeve is when people use the rand() when they want hash() but I will leave that rant for another day.

      • aidenn033 minutes ago
        Per the manpage you linked, openbsd's behavior does not match the drand48() interface, since the drand48() interface requires determinism.
      • hansvm2 hours ago
        I'm interested in that rant (at $WORK we adopted hash() for almost everything, and I'm curious to hear other perspectives).
  • NelsonMinar6 hours ago
    What is wrong with software engineers that we keep making really stupid basic mistakes like this? Sometimes I think programming should require licensing and regular testing.
    • anonymous9082136 hours ago
      We direly need to split things into a licensed engineering field which is necessary for working on security- and reliability-critical systems, and a generic unlicensed software developer field where people can screw around with their 1000 dependency JS frontends to their hearts' content. The two should not be conflated and yet so easily are.
      • greggsy4 hours ago
        Certification do exist for engineers, and various industries and governments impose their own certification programs on platforms and software before they’re authorised for use.

        Each with varying degrees of trust. The outcome is never perfect, but that’s not their purpose.

    • LeoPanthera6 hours ago
      This is partly why I'm not too worried about AI slopcode.

      The human bar is not that high.

      I would much rather have rigorous testing than a filter based on the origin of the code.

      • hansvm2 hours ago
        What's your method for implementing rigorous testing while using AI?
    • rsalus6 hours ago
      I think it's safe to assume anything associated with PDFs is radioactive.
    • HackerThemAll6 hours ago
      Those are not the "software engineers" but coders, those who like to say that the university degree doesn't add anything in programming.
      • anonymous9082136 hours ago
        University degrees are not the difference between an engineer and a developer, universities have churned out millions of people who don't care about programming and have no idea what they're doing, who are just following the script with as little effort as possible because they were told it was the easiest way to make a lot of money.
      • adrianNan hour ago
        You can get through a Computer Science degree with just a few thousand lines of code if you focus on theory courses.
      • thin_carapace5 hours ago
        a small wonder the wunderkinds of computer science were at all capable given their lack of computer science degrees
      • gsich6 hours ago
        one and the same
  • jburgess7776 hours ago
    Does the DMCA still make it illegal to access encrypted content no matter how easy it is to discover the key? https://www.law.cornell.edu/uscode/text/17/1201

    Would the new LLM model owners like to strike this down, or use it to demonstrate how dangerous unrestricted models can be?

    • nextaccountican hour ago
      there is a case to be made that weak encryption is equivalent to no encryption at all
  • ubutler7 hours ago
    Rule #1 of rolling your own RNG: don’t.

    Rule #2? Please don’t.

    • j16sdiz7 hours ago
      That's why we use the system RNG !
      • cowlevel6 hours ago
        Be careful to use the cryptographic one, not rand(3)

        And if you're a sysadmin, be extremely careful when generating keys in VMs or embedded devices. They tend to overestimate their entropy sources - it's possible that every clone of a VM generates the same keys. In some cases (cough ECDSA) generating the same key and nonce to sign two different messages is catastrophic - it immediately leaks the private key.

        • saidnooneever6 hours ago
          good point about VMs. if you run some VPS your provider could just link in a shitty rng into the thing and not give access to the correct hardware rng. U'd really need to dig into that to find out :/.

          -object rng-random,id=objrng0,filename=/dev/null

          or maybe just a file that contains 4 :O

          • Novosell4 hours ago
            As long as the 4 is random!
        • 6 hours ago
          undefined
      • flanz_106 hours ago
        btw, the idea that the system rng isnt good enough, or "runs out" or whatever, is no longer true on pretty much every modern, widely used os.

        btw... im sure there's some legacy rng in windows or some shit that isnt good. read the docs but if it's the blessed system rng, you're probably fine!

        although... i suppose if this is news to you (the person reading this), then you probably shouldn't be implementing whatever you are that really requires prng. ask a friend for help. im not trying to be a jerk, i just want to make sure you dont hurt yourself!

    • ahartmetz6 hours ago
      Rule 3: Use as many bits of randomness as the key size.

      Rule 3b: Failing rule 3, disclose motivations and full list of employers and / or customers

      • timerol2 hours ago
        Rule 3c: At least as many bits. Bits tend to not be as random as you think they are
  • snvzzan hour ago
    That's way too many PDF implementations affected by this category of stupidity.

    It makes me wonder: Coincidence, really? There's enough there to think that there might be some invisible hand behind it.

  • JonChesterfield7 hours ago
    Wonderful.
  • paulpauper8 hours ago
    it's like the weak hardware wallet entropy bug
  • RobotToaster6 hours ago
    Obligatory xkcd https://m.xkcd.com/221/
  • esafak6 hours ago
    I assume this is the fruit of AI-driven decompilation? Nice work.
  • jeffbee8 hours ago
    You'd have to be completely off your rocker to use a PDF tool written in C anyway.
    • advisedwang7 hours ago
      very VERY few people judge tools like this by the language used to develop them.
      • jeffbee7 hours ago
        How many people judge their tools based on the AES key entropy?
        • OptionX7 hours ago
          A lot actually.

          You're confusing just assuming by default its enough for purpose rather than not caring at all.

      • j16sdiz7 hours ago
        just down vote it.

        You can downvote anything not interesting.

        If he have list some alternative or give example, it might be interesting.

    • cowlevel7 hours ago
      What are the alternatives?
      • crote7 hours ago
        PDF.js, for example. It's what Firefox uses, and most websites with integrated on-page PDF viewing functionality.
    • lirolero7 hours ago
      Genuine question, since I'm not very knowledgeable about this: why is using C for a PDF tool such a bad idea?
      • zamalek6 hours ago
        File formats are the buffer issue honeypot. You may be aware of how often video and audio codecs have vulnerabilities - it's nearly never the hand-tuned frame decode assembly (where you would think all the mistakes would be). It's nearly always the thing that reads the metadata and encoded frames to memory. Binary formats have things like offsets in them, and those can be trivially used to overrun.

        Same thing applies here. Even Rust has a crate for dealing with binary data, despite its memory promises: https://crates.io/crates/untrusted

        It's a fucking minefield, and this is one area where the Rust zealots are undeniably correct. It doesn't have to be Rust, any memory safe language will do, but Rust also happens to be performance competitive and that's usually also desirable.

        • tialaramex5 hours ago
          The technology you want for this sort of work is WUFFS, for Wrangling Untrusted File Formats Safely.

          Rust is a general purpose programming language, which is great if your problem might be something never imagined before, but this literally isn't our first rodeo, we have wrangled lots of file formats before, we should use a language purpose-built to do that safely.

          • zamalek5 hours ago
            > Rust is a general purpose programming language

            I don't understand how I hit the anti-Rust tripwire here:

            > My comment: any memory safe language will do

            • tialaramex4 hours ago
              Not an anti-Rust tripwire. Just that WUFFS is the appropriate technology.

              I like 4th edition D&D but if you're trying to make a story about nuanced inter-personal conflict in which there's no actual violence it's just not the right roleplaying system and so I'm not going to agree with your choice to recommend 4eD&D as the system for the story "Love and Jealousy in the Elven Forest"

              I've written a whole bunch of Rust, and hardly any WUFFS - but, I wasn't writing code for Wrangling Untrusted File Formats and that's very much what you're doing in a PDF parser.

              • jeffbee4 hours ago
                I am a big fan of WUFFS but some recent developments by people assisted by AIs writing format parsers in other languages has made me question whether it will be maintained or forgotten.
      • tptacek7 hours ago
        I think the claim is hyperbolic, since most people memory-unsafe PDF implementations, but PDF is a monster format, a metaformat that brings in virtually every conceivable display format, and their renderer implementations with them, often poorly-maintained, never-touched reference implementations from the before times. PDF is pretty scary.
      • cowlevel6 hours ago
        PDFs are usually untrusted input and C provides no assurance there isn't a bug in the code that allows corrupted input to turn into arbitrary remote code execution.
        • F3nd05 hours ago
          Other than Ada/SPARK, which languages can guarantee this won’t happen?
          • cowlevel4 hours ago
            Very few languages can prevent you writing something like "if(text == "shibboleth") rootshell();" but most languages don't make it trivial to write accidentally.
          • tialaramex5 hours ago
            This trivially can't happen in WUFFS. Forget RCE, WUFFS can't even do a traditional Hello World program because (1) you can't do I/O in WUFFS and (2) the language doesn't have strings.

            https://github.com/google/wuffs

      • recursive7 hours ago
        buffer overflow vulnerability in code dealing with user generated data and a complex file format.