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  1. <!DOCTYPE html><head><meta charset="utf-8" /><meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no" /><meta name="keywords" content="GNU, Emacs, Libre Software, Hurd, Guile, Guix" /><meta name="description" content="GNUcode.me is a website focusing on libre software projects, especially the GNU project." /><link type="application/atom+xml" rel="alternate" title="GNUcode.me -- Feed" href="/feed.xml" /><a rel="me" href="https://fosstodon.org/@thegnuguy"></a><link type="text/css" href="css/footer.min.css" rel="stylesheet"></link><link type="text/css" href="css/header.min.css" rel="stylesheet"></link><link type="text/css" href="css/main.min.css" rel="stylesheet"></link><title>OpenBSD's Philosophy — GNUcode.me</title></head><body><header><nav><ul><li><a href="index.html">GNUcode.me</a></li><li><a href="services.html">Services</a></li><li><a href="about.html">About</a></li><li><a href="business-ideas.html">Business-ideas</a></li></ul></nav></header><h1>OpenBSD's Philosophy</h1><main><section class="basic-section-padding"><article><h3>by Joshua Branson — April 17, 2024</h3><div><p>I have talked about OpenBSD before in this blog, and I recently
    2. 

  2. watched a talk by OpenBSD's leader Theo de Raadt about <code>pledge ()</code> and
    3. 

  3. <code>arc4random()</code>. He described OpenBSD's design philosophy so well, that
    4. 

  4. I wanted to write it down.  You should definitely take some time to
    5. 

  5. hear Theo speak.  He's entertaining, and his talks are super awesome!</p><p>So a long time ago (early 90s ?), a cracker (1) broke into Theo's
    6. 

  6. OpenBSD's syslog.  This got Theo to examine OpenBSD's source code to
    7. 

  7. fix any lingering bugs, and he found a lot.  He realized that trying
    8. 

  8. to constantly examine source code to prevent bugs is a never ending
    9. 

  9. process.  He wanted to ensure code quality got better over time.  He
    10. 

  10. envision an operating system that that enforced code correctness like
    11. 

  11. the below ASCII art shows.</p><pre><code>__________________________
    12. 

  12. | Poorly written programs |
    13. 

  13. | crash on OpenBSD.       |
    14. 

  14. | ----------------------  |
    15. 

  15. | | Correctly written  |  |
    16. 

  16. | | programs run well  |  |
    17. 

  17. | | on OpenBSD.        |  |
    18. 

  18. | ----------------------  |
    19. 

  19. ---------------------------</code></pre><p>He wondered if he could create features to slightly narrow the things
    20. 

  20. that applications could do.  When poorly written programs run on
    21. 

  21. OpenBSD, they crash in deterministic ways, but correct programs work
    22. 

  22. just fine.  Theo also made sure that &quot;mitigations&quot;, or checks to ensure
    23. 

  23. a program's correctness, <em>cannot</em> be turned off on OpenBSD.  If a user
    24. 

  24. or a project manager has a problem with an application not working on
    25. 

  25. OpenBSD due to a toggleable security feature, then the user or project
    26. 

  26. manager will just turn off the feature.  So to ensure that programs
    27. 

  27. abide by the mitigations, OpenBSD enforces their security policies.</p><p>OpenBSD also makes it easy to use their security features.  If they
    28. 

  28. introduce a policy that is manatory, they try to make the API easy to
    29. 

  29. use.  If you create a security policy that is hard for the programmer
    30. 

  30. to use, then the security policy won't be used.</p><p>When OpenBSD creates a new mitigation, their application porters port
    31. 

  31. 3rd party software packages to OpenBSD.  Typically these changes find
    32. 

  32. their way into the upstream packages.  What's awesome is that usually
    33. 

  33. other operating systems start to use OpenBSD mitigations on their
    34. 

  34. systems 5 years after OpenBSD introduced them.  Windows, Mac, and
    35. 

  35. Linux applications all benefit from the strict standards that OpenBSD
    36. 

  36. creates. Theo's talks gave two examples for this: <code>pledge ()</code> and
    37. 

  37. <code>arc4random ()</code>.</p><p>Here's a question for you.  How do you get random data?  Well you read
    38. 

  38. <code>/dev/random</code> of course.  Simple.  Easy.  Done.  That used to be how
    39. 

  39. things were handled.  Apparently reading from <code>/dev/random</code> has some
    40. 

  40. limitations that Theo mentioned.  Can you read from <code>/dev/random</code>
    41. 

  41. inside the kernel?  Inside a library?  In your libc?  Reading from
    42. 

  42. <code>/dev/random</code> is not perfect.  Theo wanted to make something better.</p><p>OpenBSD created <code>arc4random ()</code> as a better source of entropy.  It is
    43. 

  43. a C function that almost any application can call (even the kernel),
    44. 

  44. most of the time.  This lets many applications, libraries, etc. easily
    45. 

  45. use random numbers.  What's surprizing to me is that many operating
    46. 

  46. systems use <code>arc4random ()</code> or a function like it, so that more
    47. 

  47. applictions can easily request random data.  This function (or one
    48. 

  48. like it) exists on your Android phone, iPhone, iMac, and sort of on
    49. 

  49. Linux thanks to OpenBSD.</p><p>What's <code>pledge ()</code> ?  Oh ho, let me tell you!  Let's take a look at a
    50. 

  50. typical program.</p><pre><code class="language-C">int main () {
    51. 

  51. 

  52.   initialize_stuff();
    53. 

  53.   
    54. 

  54.   for (;;) {
    55. 

  55.     ;; let's run the program
    56. 

  56.   }
    57. 

  57. 

  58. }</code></pre><p>Most programs have an initialization phase followed by a loop, in
    59. 

  59. which the application runs.  The OpenBSD team realized that the
    60. 

  60. initialize phase uses most of the system calls.  After the initialize
    61. 

  61. phase, the program typically needs less system calls.  OpenBSD's
    62. 

  62. <code>pledge ()</code> was created in response to this pattern present in most
    63. 

  63. programs.</p><p><code>pledge ()</code> is a security call, by which an application tells the
    64. 

  64. kernel, &quot;I pledge to only do these things and no other.&quot;  For example,
    65. 

  65. &quot;I pledge to only output text&quot;.  Or &quot;I pledge to only access the
    66. 

  66. internet and output text.&quot;  If the application tries to do something
    67. 

  67. that it has pledged not to do, then OpenBSD kills the application.</p><p>A really interesting blog post that talks about this is at
    68. 

  68. <a href="https://justine.lol/pledge/">justine's blog</a>.</p><p>After watching two of Theo's talks, I am fairly convinced that his
    69. 

  69. design goals are slowly working to make all POSIX operating systems
    70. 

  70. more correct and secure.  I used to dual boot Guix System and OpenBSD,
    71. 

  71. but unfortunately my spare SSD busted.  So for now I am only using
    72. 

  72. Guix System.  I personally prefer to use Guix System for my linode
    73. 

  73. server (that powers this blog), because Guix makes it easy to manage
    74. 

  74. servers.</p><p>I wish that the Guix developers could one day create Guix OpenBSD
    75. 

  75. System, but I have been told that Guix System assumes your libc is
    76. 

  76. <code>glibc</code> and that OpenBSD cannot currently make isolated build
    77. 

  77. environments as well as Linux can.  Also fun fact OpenBSD is not
    78. 

  78. currently working on reproducible builds.  :)</p><p>My two only minor complaints with OpenBSD currently are:</p><ul><li>I wish OpenBSD supported Wayland. This may happen in 6 months to a
    79. 

  79. year.  Fingers crossed.</li><li>A better filesystem: OpenBSD's FFS (fast file system) works, but it
    80. 

  80. is possible to lose data in a crash.  Filesystems are <em>really</em> hard
    81. 

  81. to get right.  Kent Overstreet has been working on bcachefs for
    82. 

  82. almost a decade now, and it might soon become one of Linux's best
    83. 

  83. filesystems (my opinion), so I don't blame OpenBSD for not trying to
    84. 

  84. create a new next generational filesystem.  Anybody want to spend 10
    85. 

  85. years of their life creating an awesome filesystem that will
    86. 

  86. probably only work well on OpenBSD?  One might be able to port
    87. 

  87. HammerFS to OpenBSD, and a basic read-only port does exist.</li></ul><p>If you want to try OpenBSD, give it a shot!  It works really well on
    88. 

  88. most lenovo laptops and most desktop machines.</p><ol><li>Nerdy computer people like me use the word &quot;hacker&quot; to mean someone
    89. 

  89. who builds computer programs, and a &quot;cracker&quot; is someone who breaks
    90. 

  90. into computer systems.</li></ol></div></article></section></main><footer><p>© 2020 Joshua Branson.  The text on this site is free culture under the Creative Commons Attribution Share-Alike 4.0 International license.</p><p>This website is build with Haunt, a static site generator written in Guile Scheme.  Source code is <a href="https://notabug.org/jbranso/gnucode.me">available.</a></p><p>The color theme of this website is based off of the famous <a href="#3f3f3f" target="_blank">zenburn</a> theme.</p></footer></body>
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