discussion

I've started reviewing this, and the main thing I don't like is the post-commit wrapper wrapper that ikiwiki-makerepo is patched to set up. That just seems unnecessarily complicated. Why can't ikiwiki itself detect the "cvs add " call and avoid doing anything in that case? --Joey

The wrapper wrapper does three things:

It ignores cvs add <directory>, since this is a weird CVS behavior that ikiwiki gets confused by and doesn't need to act on.

It prevents cvs locking against itself: cvs commit takes a write lock and runs the post-commit hook, which runs cvs update, which wants a read lock and sleeps forever -- unless the post-commit hook runs in the background so the commit can "finish".

It fails silently if the ikiwiki post-commit hook is missing. CVS doesn't have any magic post-commit filenames, so hooks have to be configured explicitly. I don't think a commit will actually fail if a configured post-commit hook is missing (though I can't test this at the moment).

Thing 1 can probably be handled within ikiwiki, if that seems less gross to you.

It seems like it might be. You can use a getopt hook to check @ARGV to see how it was called. --Joey

This does the trick iff the post-commit wrapper passes its args along. Committed on my branch. This seems potentially dangerous, since the args passed to ikiwiki are influenced by web commits. I don't see an exploit, but for paranoia's sake, maybe the wrapper should only be built with execv() if the cvs plugin is loaded? --schmonz

Hadn't considered that. While in wrapper mode the normal getopt is not done, plugin getopt still runs, and so any unsafe options that other plugins support could be a problem if another user runs the setuid wrapper and passes those options through. --Joey

I've tried compiling the argument check into the wrapper as the first thing main() does, and was surprised to find that this doesn't prevent the cvs add <dir> deadlock in a web commit. I was convinced this'd be a reasonable solution, especially if conditionalized on the cvs plugin being loaded, but it doesn't work. And I stuck debug printfs at the beginning of all the rcs_foo() subs, and whatever cvs add <dir> is doing to ikiwiki isn't visible to my plugin, because none of those subs are getting called. Nuts. Can you think of anything else that might solve the problem, or should I go back to generating a minimal wrapper wrapper that checks for just this one thing? --schmonz

I don't see how there could possibly be a difference between ikiwiki's C wrapper and your shell wrapper wrapper here. --Joey

I was comparing strings overly precisely. Fixed on my branch. I've also knocked off the two most pressing to-do items. I think the plugin's ready for prime time. --schmonz

Thing 2 I'm less sure of. (I'd like to see the web UI return immediately on save anyway, to a temporary "rebuilding, please wait if you feel like knowing when it's done" page, but this problem with CVS happens with any kind of commit, and could conceivably happen with some other VCS.)

None of the other VCSes let a write lock block a read lock, apparently.

Anyway, re the backgrounding, when committing via the web, the post-commit hook doesn't run anyway; the rendering is done via the ikiwiki CGI. It would certianly be nice if it popped up a quick "working" page and replaced it with the updated page when done, but that's unrelated; the post-commit hook only does rendering when committing using the VCS directly. The backgrounding you do actually seems safe enough -- but tacking on a " &" to the ikiwiki wrapper call doesn't need a wrapper script, does it? --Joey

Nope, it works fine to append it to the CVSROOT/loginfo line. Fixed on my branch. --schmonz

Thing 3 I think I did in order to squelch the error messages that were bollixing up the CGI. It was easy to do this in the wrapper wrapper, but if that's going away, it can be done just as easily with output redirection in CVSROOT/loginfo.

--schmonz

If the error messages screw up the CGI they must go to stdout. I thought we had stderr even in the the CVS dark ages. --Joey

Some messages go to stderr, but definitely not all. That's why I wound up reaching for IPC::Cmd, to execute the command line safely while shutting CVS up. Anyway, I've tested what happens if a configured post-commit hook is missing, and it seems fine, probably also thanks to IPC::Cmd. --schmonz

Further review.. --Joey

I don't understand what cvs_shquote_commit is trying to do with the test message, but it seems highly likely to be insecure; I never trust anything that relies on safely quoting user input passed to the shell.

(As an aside, shell_quote can die on certian inputs.)

Seems to me that, if IPC::Cmd exposes input to the shell (which I have not verified but its docs don't specify; a bad sign) you chose the wrong tool and ended up doing down the wrong route, dragging in shell quoting problems and fixes. Since you chose to use IPC::Cmd just because you wanted to shut up CVS stderr, my suggestion would be to use plain system to run the command, with stderr temporarily sent to /dev/null:

open(my $savederr, ">&STDERR");
open(STDERR, ">", "/dev/null");
my $ret=system("cvs", "-Q", @_);
open(STDERR, ">$savederr");

cvs_runcvs should not take an array reference. It's usual for this type of function to take a list of parameters to pass to the command.

Thanks for reading carefully. I've tested your suggestions and applied them on my branch. --schmonz

I've abstracted out CVS's involvement in the wrapper, adding a new "wrapperargcheck" hook to examine argc/argv and return success or failure (failure causes the wrapper to terminate) and implementing this hook in the plugin. In the non-CVS case, the check immediately returns success, so the added overhead is just a function call.

Given how rarely anything should need to reach in and modify the wrapper -- I'd go so far as to say we shouldn't make it too easy -- I don't think it's worth the effort to try and design a more general-purpose way to do so. If and when some other problem thinks it wants to be solved by a new wrapper hook, it's easy enough to add one. Until then, I'd say it's more important to keep the wrapper as short and clear as possible. --schmonz

I've committed a slightly different hook, which should be general enough that IkiWiki::Receive can also use it, so please adapt your code to that. --Joey

Done. --schmonz.

I'm attempting to bring some polish to this plugin, starting with fuller test coverage. In preparation, I've refactored the tests a bunch (and shuffled the code a bit) in my branch. I'm worried, however, that my misunderstanding of git rebase may have made my branch harder for you to pull.

Before I go writing a whole swack of test cases, could you merge my latest? Through at least ad0e56cdcaaf76bc68d1b5c56e6845307b51c44a there should be no functional change. --schmonz

Never mind, I was able to convince myself (by cloning origin afresh and merging from schmonz/cvs). The history is a little gross but the before-and-after diff looks right.

Bugs found and fixed so far:

Stop treating text files as binary (-kb) on rcs_add() (ac8eab29e8394aca4c0b23a6687ec947ea1ac869)

Merged to current head. --Joey

Hi! Bugfixes in schmonz/cvs I'd like to see merged:

6753235d: Return bounded output from rcs_diff() when asked, as the API states.
e45175d5: Always explicitly set CVS keyword substitution behavior. Fixes behavior when a text file is added under a name formerly used for a binary file.
b30cacdf: If the previous working directory no longer exists after a CVS operation, don't try to chdir() back to it afterward.
91b477c0: Fix diffurl links (cvsweb expects unescaped '/').

These are all the diffs that exist on the branch, so if the changes are acceptable you should be able to simply merge the branch. --schmonz

All applied. --Joey