1 I've started reviewing this, and the main thing I don't like is the
2 post-commit wrapper wrapper that ikiwiki-makerepo is patched to set up.
3 That just seems unnecessarily complicated. Why can't ikiwiki itself detect
4 the "cvs add <directory>" call and avoid doing anything in that case?
7 > The wrapper wrapper does three things:
9 > 7. It ignores `cvs add <directory>`, since this is a weird CVS
10 > behavior that ikiwiki gets confused by and doesn't need to act on.
11 > 7. It prevents `cvs` locking against itself: `cvs commit` takes a
12 > write lock and runs the post-commit hook, which runs `cvs update`,
13 > which wants a read lock and sleeps forever -- unless the post-commit
14 > hook runs in the background so the commit can "finish".
15 > 7. It fails silently if the ikiwiki post-commit hook is missing.
16 > CVS doesn't have any magic post-commit filenames, so hooks have to
17 > be configured explicitly. I don't think a commit will actually fail
18 > if a configured post-commit hook is missing (though I can't test
19 > this at the moment).
21 > Thing 1 can probably be handled within ikiwiki, if that seems less
24 >> It seems like it might be. You can use a `getopt` hook to check
25 >> `@ARGV` to see how it was called. --[[Joey]]
27 >>> This does the trick iff the post-commit wrapper passes its args
28 >>> along. Committed on my branch. This seems potentially dangerous,
29 >>> since the args passed to ikiwiki are influenced by web commits.
30 >>> I don't see an exploit, but for paranoia's sake, maybe the wrapper
31 >>> should only be built with execv() if the cvs plugin is loaded?
34 >>>> Hadn't considered that. While in wrapper mode the normal getopt is not
35 >>>> done, plugin getopt still runs, and so any unsafe options that
36 >>>> other plugins support could be a problem if another user runs
37 >>>> the setuid wrapper and passes those options through. --[[Joey]]
39 >>>>> I've tried compiling the argument check into the wrapper as
40 >>>>> the first thing main() does, and was surprised to find that
41 >>>>> this doesn't prevent the `cvs add <dir>` deadlock in a web
42 >>>>> commit. I was convinced this'd be a reasonable solution,
43 >>>>> especially if conditionalized on the cvs plugin being loaded,
44 >>>>> but it doesn't work. And I stuck debug printfs at the beginning
45 >>>>> of all the rcs_foo() subs, and whatever `cvs add <dir>` is
46 >>>>> doing to ikiwiki isn't visible to my plugin, because none of
47 >>>>> those subs are getting called. Nuts. Can you think of anything
48 >>>>> else that might solve the problem, or should I go back to
49 >>>>> generating a minimal wrapper wrapper that checks for just
50 >>>>> this one thing? --[[schmonz]]
52 >>>>>> I don't see how there could possibly be a difference between
53 >>>>>> ikiwiki's C wrapper and your shell wrapper wrapper here. --[[Joey]]
55 >>>>>>> I was comparing strings overly precisely. Fixed on my branch.
56 >>>>>>> I've also knocked off the two most pressing to-do items. I
57 >>>>>>> think the plugin's ready for prime time. --[[schmonz]]
59 > Thing 2 I'm less sure of. (I'd like to see the web UI return
60 > immediately on save anyway, to a temporary "rebuilding, please wait
61 > if you feel like knowing when it's done" page, but this problem
62 > with CVS happens with any kind of commit, and could conceivably
63 > happen with some other VCS.)
65 >> None of the other VCSes let a write lock block a read lock, apparently.
67 >> Anyway, re the backgrounding, when committing via the web, the
68 >> post-commit hook doesn't run anyway; the rendering is done via the
69 >> ikiwiki CGI. It would certianly be nice if it popped up a quick "working"
70 >> page and replaced it with the updated page when done, but that's
71 >> unrelated; the post-commit
72 >> hook only does rendering when committing using the VCS directly. The
73 >> backgrounding you do actually seems safe enough -- but tacking
74 >> on a " &" to the ikiwiki wrapper call doesn't need a wrapper script,
75 >> does it? --[[Joey]]
77 >>> Nope, it works fine to append it to the `CVSROOT/loginfo` line.
78 >>> Fixed on my branch. --[[schmonz]]
80 > Thing 3 I think I did in order to squelch the error messages that
81 > were bollixing up the CGI. It was easy to do this in the wrapper
82 > wrapper, but if that's going away, it can be done just as easily
83 > with output redirection in `CVSROOT/loginfo`.
87 >> If the error messages screw up the CGI they must go to stdout.
88 >> I thought we had stderr even in the the CVS dark ages. ;-) --[[Joey]]
90 >>> Some messages go to stderr, but definitely not all. That's why
91 >>> I wound up reaching for IPC::Cmd, to execute the command line
92 >>> safely while shutting CVS up. Anyway, I've tested what happens
93 >>> if a configured post-commit hook is missing, and it seems fine,
94 >>> probably also thanks to IPC::Cmd.
100 Further review.. --[[Joey]]
102 I don't understand what `cvs_shquote_commit` is
103 trying to do with the test message, but it seems
104 highly likely to be insecure; I never trust anything
105 that relies on safely quoting user input passed to the shell.
107 (As an aside, `shell_quote` can die on certian inputs.)
109 Seems to me that, if `IPC::Cmd` exposes input to the shell
110 (which I have not verified but its docs don't specify; a bad sign)
111 you chose the wrong tool and ended up doing down the wrong
112 route, dragging in shell quoting problems and fixes. Since you
113 chose to use `IPC::Cmd` just because you wanted to shut
114 up CVS stderr, my suggestion would be to use plain `system`
115 to run the command, with stderr temporarily sent to /dev/null:
117 open(my $savederr, ">&STDERR");
118 open(STDERR, ">", "/dev/null");
119 my $ret=system("cvs", "-Q", @_);
120 open(STDERR, ">$savederr");
122 `cvs_runcvs` should not take an array reference. It's
123 usual for this type of function to take a list of parameters
124 to pass to the command.
126 > Thanks for reading carefully. I've tested your suggestions and
127 > applied them on my branch. --[[schmonz]]
131 I've abstracted out CVS's involvement in the wrapper, adding a new
132 "wrapperargcheck" hook to examine `argc/argv` and return success or
133 failure (failure causes the wrapper to terminate) and implementing
134 this hook in the plugin. In the non-CVS case, the check immediately
135 returns success, so the added overhead is just a function call.
137 Given how rarely anything should need to reach in and modify the
138 wrapper -- I'd go so far as to say we shouldn't make it too easy
139 -- I don't think it's worth the effort to try and design a more
140 general-purpose way to do so. If and when some other problem thinks
141 it wants to be solved by a new wrapper hook, it's easy enough to add
142 one. Until then, I'd say it's more important to keep the wrapper as
143 short and clear as possible. --[[schmonz]]
145 > I've committed a slightly different hook, which should be general enough
146 > that `IkiWiki::Receive` can also use it, so please adapt your code to
149 >> Done. --[[schmonz]].