4 ms·

"Nobody should be running Exim in 2021." Maybe, yet it still shuffles a lot of email around the place. It deals with a lot of corner cases. When I say corner

"Nobody should be running Exim in 2021." Maybe, yet it still shuffles a lot of email around the place. It deals with a lot of corner cases. When I say corner cases I mean orthogonality that might put off a top class mathematician fresh from fiddling with spherical cows in n dimensions. Email is not simply a bit odd but downright pathologically weird. We all know what email is and it's just so simple. You can use telnet and point it at a smtpd and send a message. HELO me ... mail from: .... rcpt to: .... data .... . (blah blah message_id:x) Yet, for some reason an MTA is a massive edifice of oddities. You could make an MTA that simply shuffles a text stream from a to b but what sort of text stream? MIME encoded doesn't mean what you think it does in quite a lot of cases. MIME is nearly formally defined but as always the beauty is in the eye of the programmer. As well as moving text around a bit, MTAs are asked to do a firewall's role and also integrate with AV and anti spam. Ideally they should also be capable of reading minds. I could go on. Exim is probably not the most beautiful example of modern security practice but it is actively developed by people who do give a shit and are trying to keep something that no one will ever allow to go away working, as best they can. RFC822 (etc, int al, ad nauseam) can never be considered a modern communication technique that will ever lend itself to secure programming practices. Email is never going to be "secure" by worrying about what language an MTA is written in and I think you might have forgotten the worst part of the security circus here: The end user. You can call out the MTA as much as you like but your Go or Rust jobbie will still deliver an email that my Financial Controller clicks on and dumps my bank account. Nobody should be using email in 2021 (discuss ... 8)

tptacek 6y ago
You could break the glass and roll back the year numbers on this comment, switch the "Exim" badge to "Sendmail", and sell this as an authentic comp.security.unix post circa 1996. I think we can see in retrospect what an absolute debacle that was for the Internet. The difference is that today we have better options. Postfix is written in C, and none of us should be comfortable with that, but it's not macraméd out of heap overflows, and its heap doesn't start with a blob that will shell-expand to system commands.
- ornxka 6y ago
  >Postfix is written in C, and none of us should be comfortable with that qmail is written in C, and it has never had a serious security hole that I am aware of. Not all C code is unsafe.
  - erik_seaberg 6y ago
    64-bit qmail was remotely exploitable. The author believes a small address space (below 4 GB) was an adequate mitigation, but the code was confused and trying to do something unsafe. https://lwn.net/Articles/820969/ https://lwn.net/Articles/820969/
  - tptacek 6y ago
    One thing you can say for both Postfix and qmail is that they're written to avoid the problems of the C standard library. Exim is not.
- guenthert 6y ago
  > what an absolute debacle that was for the Internet You make it sound like it ended the Internet or something. One could also argue (with only similar level of hyperbole) that it was sendmail which made the Internet a success. Obviously the truth is in between, but lets give credit where credit is due. Sendmail served us well in its time. It's not inherently the fault of its developers, that the Internet evolved to a much darker place over time.
  - tptacek 6y ago
    We disagree on how big of a deal pervasive serverside memory corruption vulnerabilities have been. Easily a bigger problem than early-1990s congestion collapse.

tptacek 6y ago

You could break the glass and roll back the year numbers on this comment, switch the "Exim" badge to "Sendmail", and sell this as an authentic comp.security.unix post circa 1996. I think we can see in retrospect what an absolute debacle that was for the Internet. The difference is that today we have better options. Postfix is written in C, and none of us should be comfortable with that, but it's not macraméd out of heap overflows, and its heap doesn't start with a blob that will shell-expand to system commands.

ornxka 6y ago
>Postfix is written in C, and none of us should be comfortable with that qmail is written in C, and it has never had a serious security hole that I am aware of. Not all C code is unsafe.
- erik_seaberg 6y ago
  64-bit qmail was remotely exploitable. The author believes a small address space (below 4 GB) was an adequate mitigation, but the code was confused and trying to do something unsafe. https://lwn.net/Articles/820969/ https://lwn.net/Articles/820969/
- tptacek 6y ago
  One thing you can say for both Postfix and qmail is that they're written to avoid the problems of the C standard library. Exim is not.
guenthert 6y ago
> what an absolute debacle that was for the Internet You make it sound like it ended the Internet or something. One could also argue (with only similar level of hyperbole) that it was sendmail which made the Internet a success. Obviously the truth is in between, but lets give credit where credit is due. Sendmail served us well in its time. It's not inherently the fault of its developers, that the Internet evolved to a much darker place over time.
- tptacek 6y ago
  We disagree on how big of a deal pervasive serverside memory corruption vulnerabilities have been. Easily a bigger problem than early-1990s congestion collapse.