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There is no silver bullet, but one very helpful principle: Avoid complexity. But let me ask you: What are the big security problems that you see with a persona

There is no silver bullet, but one very helpful principle: Avoid complexity. But let me ask you: What are the big security problems that you see with a personal email server that you think are difficult to get right/to avoid?

sanderjd 10y ago
All the same things that are difficult to get right in any other chunk of code that handles arbitrary input from across the internet. I have a couple tomes on this subject: "The Art of Software Security Assessment" is 1200 pages long, "The Web Application Hacker's Handbook" is another 900 pages. Nobody has solved all the issues discussed in those (and many other) books in such a way that makes this no longer "hard". Note that I'm not at all claiming this stuff is impossible or a total lost cause, just that I think it easily passes the bar for "hard", and is certainly tricky enough to get right that I personally don't think it's worth the effort to run network-connected services unless they're for a business that I'm hoping will pay for my time and effort somehow.
- zAy0LfpBZLC8mAC 10y ago
  > All the same things that are difficult to get right in any other chunk of code that handles arbitrary input from across the internet. That's about as unspecific as you can be, isn't it? So, let me give the equally uninformative answer: All of those are either easy to prevent, or they lead to a DoS, which isn't a big concern for a personal email server. > "The Art of Software Security Assessment" is 1200 pages long Haven't read it, but by its TOC, it's mostly irrelevant to the given problem (except maybe that it teaches you to not write you personal mail server in C, who would have thought ...). > "The Web Application Hacker's Handbook" is another 900 pages. Didn't I say something about avoiding complexity? No, you should not build your mail server as a web application, in case that wasn't clear. > Nobody has solved all the issues discussed in those (and many other) books in such a way that makes this no longer "hard". Well, how about you give an example of one problem that you think is still hard enough to be a major obstacle to implementing you own secure personal mail server? > [...] that I personally don't think it's worth the effort to run network-connected services unless they're for a business that I'm hoping will pay for my time and effort somehow. How is it that you suddenly switched to "services"? I thought we were talking about "network software"? Am I supposed to believe that you are not running a web browser unless it's for a business that you're hoping will pay for your time and effort somehow? How about web applications? Or what is your justification for a distinction between "services" and "network software", as far as possible security impact is concerned?
  - sanderjd 10y ago
    As for your final paragraph about word choice: I'm not sure what you mean, I'm just talking about any software that is running somewhere and accessible across a network. As for the rest of it... there was a time when I would have bothered trying to delineate some specifics for you, thinking I was providing some educational service or something, or that maybe I'd learn something from you in the discussion, but I'm getting the sense that if I did that, you would just be dismissive of all those things as "not a big concern", "because of complexity", "because of C", etc., and I would be wasting my time. There are plenty of places you can go read about this stuff if you want to, but I don't think you do, I think you're just looking for an argument. Good luck to you!
    - zAy0LfpBZLC8mAC 10y ago
      > As for your final paragraph about word choice: I'm not sure what you mean, I'm just talking about any software that is running somewhere and accessible across a network. Well, a web browser is accessible across a network. An email client is accessible across a network. What fundamentally distinguishes a mail server from either of those that justifies rejecting to run one of those yourself outright, while presumably being fine with the others? You seem to have some implicit assumption that a piece of software that opens a listening TCP socket is somehow much more vulnerable than one that doesn't. I don't think that that is justified, and if anything, gives you a false sense of security. > but I'm getting the sense that if I did that, you would just be dismissive of all those things as "not a big concern", "because of complexity", "because of C", etc., and I would be wasting my time. I am not dismissing anything, I am just pointing out why those aren't problems. If you disagree, feel free to disagree. And maybe make an actual more specific argument than "there are a lot of things one can do wrong". I mean, how is it relevant that there are tons of ways to screw up buffer handling in C when the obvious solution is to just not write your own personal mail server in C? Yes, it is hard to write secure software in C. Very hard. Yes, there are cases where there are good reasons to write network software in C despite that. Is your own personal mail server one of them? No. Or how is it relevant that the web is a hugely complex mess of inherently insecure APIs when the task at hand is writing an email server? Just don't write your email server as a web application and you don't have to deal with any of the myriads of security problems that plague the web. > There are plenty of places you can go read about this stuff if you want to, but I don't think you do, I think you're just looking for an argument. Good luck to you! Thanks, but I think I have found enough vulnerabilities to not need any introductory books to understand how people constantly screw up security in their code.

sanderjd 10y ago

All the same things that are difficult to get right in any other chunk of code that handles arbitrary input from across the internet. I have a couple tomes on this subject: "The Art of Software Security Assessment" is 1200 pages long, "The Web Application Hacker's Handbook" is another 900 pages. Nobody has solved all the issues discussed in those (and many other) books in such a way that makes this no longer "hard". Note that I'm not at all claiming this stuff is impossible or a total lost cause, just that I think it easily passes the bar for "hard", and is certainly tricky enough to get right that I personally don't think it's worth the effort to run network-connected services unless they're for a business that I'm hoping will pay for my time and effort somehow.

zAy0LfpBZLC8mAC 10y ago
> All the same things that are difficult to get right in any other chunk of code that handles arbitrary input from across the internet. That's about as unspecific as you can be, isn't it? So, let me give the equally uninformative answer: All of those are either easy to prevent, or they lead to a DoS, which isn't a big concern for a personal email server. > "The Art of Software Security Assessment" is 1200 pages long Haven't read it, but by its TOC, it's mostly irrelevant to the given problem (except maybe that it teaches you to not write you personal mail server in C, who would have thought ...). > "The Web Application Hacker's Handbook" is another 900 pages. Didn't I say something about avoiding complexity? No, you should not build your mail server as a web application, in case that wasn't clear. > Nobody has solved all the issues discussed in those (and many other) books in such a way that makes this no longer "hard". Well, how about you give an example of one problem that you think is still hard enough to be a major obstacle to implementing you own secure personal mail server? > [...] that I personally don't think it's worth the effort to run network-connected services unless they're for a business that I'm hoping will pay for my time and effort somehow. How is it that you suddenly switched to "services"? I thought we were talking about "network software"? Am I supposed to believe that you are not running a web browser unless it's for a business that you're hoping will pay for your time and effort somehow? How about web applications? Or what is your justification for a distinction between "services" and "network software", as far as possible security impact is concerned?
- sanderjd 10y ago
  As for your final paragraph about word choice: I'm not sure what you mean, I'm just talking about any software that is running somewhere and accessible across a network. As for the rest of it... there was a time when I would have bothered trying to delineate some specifics for you, thinking I was providing some educational service or something, or that maybe I'd learn something from you in the discussion, but I'm getting the sense that if I did that, you would just be dismissive of all those things as "not a big concern", "because of complexity", "because of C", etc., and I would be wasting my time. There are plenty of places you can go read about this stuff if you want to, but I don't think you do, I think you're just looking for an argument. Good luck to you!
  - zAy0LfpBZLC8mAC 10y ago
    > As for your final paragraph about word choice: I'm not sure what you mean, I'm just talking about any software that is running somewhere and accessible across a network. Well, a web browser is accessible across a network. An email client is accessible across a network. What fundamentally distinguishes a mail server from either of those that justifies rejecting to run one of those yourself outright, while presumably being fine with the others? You seem to have some implicit assumption that a piece of software that opens a listening TCP socket is somehow much more vulnerable than one that doesn't. I don't think that that is justified, and if anything, gives you a false sense of security. > but I'm getting the sense that if I did that, you would just be dismissive of all those things as "not a big concern", "because of complexity", "because of C", etc., and I would be wasting my time. I am not dismissing anything, I am just pointing out why those aren't problems. If you disagree, feel free to disagree. And maybe make an actual more specific argument than "there are a lot of things one can do wrong". I mean, how is it relevant that there are tons of ways to screw up buffer handling in C when the obvious solution is to just not write your own personal mail server in C? Yes, it is hard to write secure software in C. Very hard. Yes, there are cases where there are good reasons to write network software in C despite that. Is your own personal mail server one of them? No. Or how is it relevant that the web is a hugely complex mess of inherently insecure APIs when the task at hand is writing an email server? Just don't write your email server as a web application and you don't have to deal with any of the myriads of security problems that plague the web. > There are plenty of places you can go read about this stuff if you want to, but I don't think you do, I think you're just looking for an argument. Good luck to you! Thanks, but I think I have found enough vulnerabilities to not need any introductory books to understand how people constantly screw up security in their code.