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gitolite/doc/3-faq-tips-etc.mkd
Sitaram Chamarty 09195afd44 document deny rules a bit better
2010-02-01 15:59:03 +05:30

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# assorted faqs, tips, and notes on gitolite
In this document:
* common errors and mistakes
* git version dependency
* other errors, warnings, notes...
* ssh-copy-id
* cloning an empty repo
* `@all` syntax for repos
* umask setting
* getting a tar file from a clone
* differences from gitosis
* simpler syntax
* two levels of access rights checking
* file/dir NAME based restrictions
* error checking the config file
* including config lines from other files
* delegating parts of the config file
* easier to specify gitweb "description" and gitweb/daemon access
* easier to link gitweb authorisation with gitolite
* better logging
* one user, many keys
* support for git installed outside default PATH
* what repos do I have access to?
* "exclude" (or "deny") rules
* "personal" branches
* custom hooks and custom git config
* access control for external commands
* design choices
* keeping the parser and the access control separate
### common errors and mistakes
* adding `repositories/` at the start of the repo name in the `git clone`.
This error is typically made by the *admin* himself -- because he knows
what `$REPO_BASE` is set to and thinks he has to provide that prefix on
the client side also :-) In fact gitolite prepends `$REPO_BASE`
internally, so you shouldn't also do the same thing!
* being able to clone but getting errors on push. Most likely caused by a
combination of:
* you already have shell access to the server, not just "gitolite"
access, *and*
* you cloned using `git clone git@server:repositories/repo.git` (notice
there's an extra "repositories/" in there?)
In other words, you used a key that completely bypassed gitolite and went
straight to the shell to do the clone.
Please see doc/6-ssh-troubleshooting.mkd for what all this means.
### git version dependency
Here's a workaround for a version dependency that the normal flow of gitolite
has.
When you edit your config file to create a new repo, and push the changes to
the server, gitolite creates an empty, bare repo for you. Normally, you're
expected to clone this on the client side, and start working -- make your
first commit(s), then push, etc.
However, cloning an empty repo requires a server side git version that is at
least 1.6.2. Gitolite detects this when creating a repo, and warns you.
The workaround is to use the older (gitosis-style) method on the client:
create an empty repo locally, make a commit or two, set an "origin" remote,
and then push. Something like:
mkdir my-new-project
cd my-new-project
git init
git commit --allow-empty -m 'Initial repository'
# or, if your client side git is too old for --allow-empty, just make some
# files, "git add" them, then "git commit"
git remote add origin git@gitolite-server:my-new-project.git
git push origin master:master
Once this is done, the repo is available for cloning by anyone else in the
normal way, since it's not empty anymore.
### other errors, warnings, notes...
#### ssh-copy-id
don't have `ssh-copy-id`? This is broadly what that command does, if you want
to replicate it manually. The input is your pubkey, typically
`~/.ssh/id_rsa.pub` from your client/workstation.
* it copies it to the server as some file
* it appends that file to `~/.ssh/authorized_keys` on the server
(creating it if it doesn't already exist)
* it then makes sure that all these files/directories have go-w perms
set (assuming user is "git"):
/home/git/.ssh/authorized_keys
/home/git/.ssh
/home/git
[Actually, sshd requires that even directories *above* ~ (/, /home,
typically) also must be `go-w`, but that needs root. And typically
they're already set that way anyway. (Or if they're not, you've got
bigger problems than gitolite install not working!)]
#### cloning an empty repo
Cloning an empty repo is only possible with clients greater than 1.6.2. So at
least one of your clients needs to have a recent git. Once at least one
commit has been made, older clients can also use it
When you clone an empty repo, git seems to complain about `fatal: The remote
end hung up unexpectedly`. However, you can ignore this, since it doesn't
seem to hurt anything. [Update 2009-09-14; this has been fixed in git
1.6.4.3]
#### `@all` syntax for repos
There *is* a way to use the `@all` syntax for repos also, as described in
`conf/example.conf`. However, there is an important difference between this
and the old `@all` (for users):
* `@all` for repos is immediately expanded, when found, into the currently
known list of repos. "Currently" means upto this point in the config
file, and "known" means having some user with some permissions associated
with the repo!
* This means that if you really want *all* repos, you'd better put this para
at the **end** of the config file!
#### umask setting
Gitweb not able to read your repos? You can change the umask for newly
created repos to something more relaxed -- see the `~/.gitolite.rc` file
### getting a tar file from a clone
You can clone the repo from github or indefero, then execute a make command to
extract a tar file of the branch you want. Please use the make command, not a
plain "git archive", because the Makefile adds a file called
`.GITOLITE-VERSION` that will help you identify which version you are using.
git clone git://github.com/sitaramc/gitolite.git
# (OR)
git clone git://sitaramc.indefero.net/sitaramc/gitolite.git
cd gitolite
make master.tar
# or maybe "make rebel.tar" or "make pu.tar"
<a name="diff"></a>
### differences from gitosis
Apart from the big ones listed in the top level README, and subjective ones
like "better config file format", there are some small, but significant and
concrete, differences from gitosis.
<a name="simpler_syntax"></a>
#### simpler syntax
The basic syntax is simpler and cleaner but it goes beyond that: **you can
specify access in bits and pieces**, even if they overlap.
Some access needs are best grouped by repo, some by username, and some by
both. So just do all of them, and gitolite will combine all the access lists!
Here's an example:
# define groups of people
@bosses = phb1 phb2 phb3
@devs = dev1 dev2 dev3
@interns = int1 int2 int3
# define groups of projects
@open = git gitolite linux rakudo
@closed = c1 c2 c3
@topsecret = ts1 ts2 ts3
# all bosses have read access to all projects
repo @open @closed @topsecret
R = @bosses
# everyone has read access to "open" projects
repo @open
R = @bosses @devs @interns
[...or any other combination you want...]
# later in the file:
# specify access for individual repos (like RW, RW+, etc)
repo c1
[...]
[...etc...]
If you notice that `@bosses` are given read access to `@open` via both rules,
do not worry that this causes some duplication or inefficiency. It doesn't
:-)
See the "specify gitweb/daemon access" section below for one more example.
#### two levels of access rights checking
Gitolite has two levels of access checks. The **first check** is what I will
call the **pre-git** level (this is the only check that gitosis has). At this
stage, the `gl-auth-command` has been invoked by `sshd`, and it knows just
three things:
* who,
* what repository, and
* what type of access (R or W)
Note that at this point no git program has entered the picture, and we have no
way of knowing what **ref** (branch, tag, etc) he is trying to update, even if
it is a "write" operation.
For a "read" operation to pass this check, the username (or `@all`) must have
read permission (i.e., R, RW, or RW+) on at least one branch of the repo.
For a "write" operation, there is an additional restriction: lines specifying
only `R` (read access) don't count. *The user must have write access to
**some** ref in the repo in order to pass this stage!*
The **second check** is via a git `update hook`. This check only happens for
write operations. By this time we know what "ref" he is trying to update, as
well as the old and the new SHAs of that ref (by which we can also deduce
whether it's a rewind or not). This is where the "per-branch" permissions
come into play.
Each refex that allows `W` access (or `+` if this is a rewind) for *this*
user, on *this* repo, is matched against the actual refname being updated. If
any of the refexes match, the push succeeds. If none of them match, it fails.
Gitolite also allows "exclude" or "deny" rules. See later in this document
for details.
#### file/dir NAME based restrictions
In addition to branch-name based restrictions, gitolite also allows you to
restrict what files or directories can be involved in changes being pushed.
This basically uses `git diff --name-only` to obtain the list of files being
changed, treating each filename as a "ref" to be matched.
Please see `conf/example.conf` for syntax and examples.
#### error checking the config file
gitosis does not do any. I just found out that if you mis-spell `members` as
`member`, gitosis will silently ignore it, and leave you wondering why access
was denied.
Gitolite "compiles" the config file first and keyword typos *are* caught so
you know right away.
#### including config lines from other files
See the entry under "INCLUDE SOME OTHER FILE" in `conf/example.conf`.
#### delegating parts of the config file
You can now split up the config file and delegate the authority to specify
access control for their own pieces. See
[doc/5-delegation.mkd](http://github.com/sitaramc/gitolite/blob/pu/doc/5-delegation.mkd)
for details.
<a name="gwd"></a>
#### easier to specify gitweb "description" and gitweb/daemon access
To enable access to a repo via gitweb *and* create a "description" for it to
show up on the webpage, just add a line like this, anywhere in the config
file:
reponame = "one line of description"
You can also specify an "owner":
reponame "owner name" = "one line of description"
To enable access to one or more repos via git daemon, just give "read"
permissions to the special username `daemon`.
There is also a special user called `gitweb` to specify gitweb access; useful
if you don't care about specifying individual descriptions for each repo and
just want to quickly enable gitweb access to one or more repos.
Remember gitolite lets you specify the access control specs in bits and
pieces, so you can keep all the daemon/gitweb access in one place, even if
each repo has more specific branch-level access config specified elsewhere.
Here's an example, using really short reponames because I'm lazy:
# maybe near the top of the file, for ease of access:
@only_web = r1 r2 r3
@only_daemon = r4 r5 r6
@web_and_daemon = r7 r8 r9
repo @only_web
R = gitweb
repo @only_daemon
R = daemon
repo @web_and_daemon
R = gitweb
R = daemon
# ...maybe much later in the file:
repo r1
# normal developer access lists for r1 and its branches/tags in the
# usual way
repo r2
# ...and so on...
<a name="gitwebauth"></a>
#### easier to link gitweb authorisation with gitolite
Over and above whether a repo is even *shown* by gitweb, you may want to
further restrict people, allowing them to view *only* those repos for which
they have been given read access by gitolite.
This requires that:
* you have to have some sort of HTTP auth on your web server (out of my
scope, sorry!)
* the HTTP auth should use the same username (like "sitaram") as used in the
gitolite config (for the corresponding user)
Once that is done, it's easy. Gitweb allows you to specify a subroutine to
decide on access. We use that feature and tie it to gitolite. Sample code
(untested, munged from something I saw [here][leho]) is given below.
Note the **utter simplicity** of the actual check (just 1 line!). This is an
unexpected piece of luck coming from the decision to keep the config parse
separate from the actual access control. The config parser puts a pure perl
hash in that file named below as `$gl_conf_compiled`, so all the parsing is
already done and we just use it!
# completely untested... but the basic idea should work fine
# change these as needed
# projectroot should be the same as gitolite's REPO_BASE, but converted to
# an absolute path
$projectroot = '/home/git/repositories/';
my $gl_conf_compiled = '/home/git/.gitolite/conf/gitolite.conf-compiled.pm';
# I assume this gives us the HTTP auth username
my $username = $cgi->remote_user;
# ----------
# parse the config file; updates %repos hash
our %repos;
die "parse $gl_conf_compiled failed: " . ($! or $@) unless do $gl_conf_compiled;
# this is gitweb's mechanism; it calls whatever sub is pointed at by this
# variable to decide access yes/no
$export_auth_hook = sub {
my $reponame = shift;
# gitweb passes us the full repo path; so we strip the beginning...
$reponame =~ s/\Q$projectroot\E\/?//;
# ...and the end, to get the repo name as it is specified in gitolite conf
$reponame =~ s/\.git$//;
return exists $repos{$reponame}{R}{$username}
|| exists $repos{$reponame}{R}{'@all'};
};
[leho]: http://leho.kraav.com/news/2009/10/27/using-apache-authentication-with-gitweb-gitosis-repository-access-control/
#### better logging
If you have been too liberal with the permission to rewind, it has built-in
logging as an emergency fallback if someone goes too far, or for audit
purposes [`*`]. The logfile names and location are configurable, and can
include the year/month/day etc in the filename for easy archival or further
processing. The log file even tells you which pattern in the config file
matched to allow that specific access to proceed.
> [`*`] setting `core.logAllRefUpdates true` does provide a safety net
> against over-zealous rewinds, but it does not tell you "who". And
> strangely, management does not seem to share the view that "blame" is just
> a synonym for "annotate" ;-)]
The log lines look like this:
2009-09-19.10:24:37 + b4e76569659939 4fb16f2a88d8b5 myrepo refs/heads/master user2 refs/heads/master
The "+" at the start indicates a non-fast forward update, in this case from
b4e76569659939 to 4fb16f2a88d8b5. So b4e76569659939 is the one to restore!
Can it get easier?
The other parts of the log line are the name of the repo, the refname being
updated, the user updating it, and the refex pattern (from the config file)
that matched, in case you need to debug the config file itself.
<a name="multikeys"></a>
#### one user, many keys
I have a laptop and a desktop I need to access the server from. I have
different private keys on them, but as far as gitolite is concerned both of
them should be treated as "sitaram". How does this work?
In gitosis, the admin creates a single "sitaram.pub" containing one line for
each of my pubkeys. In gitolite, we keep them separate: "sitaram@laptop.pub"
and "sitaram@desktop.pub". The part before the "@" is the username, so
gitolite knows these two keys belong to the same person.
Note that you don't say "sitaram@laptop" and so on in the **config** file --
as far as the config file is concerned there's just **one** user called
"sitaram" -- so you only say "sitaram" there.
I think this is easier to maintain if you have to delete or change one of
those keys.
However, now that `sitaramc@gmail.com` is also a valid username, we need to
distinguish between `sitaramc@gmail.com.pub` and `sitaramc@desktop.pub`. We
do that by requiring that the multi-key suffix you use (like "desktop" and
"laptop") should not have a `"."` in it. If it does, it looks like an email
address. The following table lists sample pubkey filenames and the
corresponding derived usernames (which is what goes into the
`conf/gitolite.conf` file):
* old style multikeys; not mistaken for emails because there is no "." in
hostname part
sitaramc.pub sitaramc
sitaramc@laptop.pub sitaramc
sitaramc@desktop.pub sitaramc
* new style, email keys; there is a "." in hostname part; so it's an email
address
sitaramc@gmail.com.pub sitaramc@gmail.com
* multikeys *with* email address
sitaramc@gmail.com@laptop.pub sitaramc@gmail.com
sitaramc@gmail.com@desktop.pub sitaramc@gmail.com
#### support for git installed outside default PATH
The normal solution is to add to the system default PATH somehow, either by
munging `/etc/profile` or by enabling `PermitUserEnvironment` in
`/etc/ssh/sshd_config` and then setting the PATH in `~/.ssh/.environment`.
All these are security risks because they allow a lot more than just you and
your git install :-)
And if you don't have root, you can't do this anyway.
The only solution till now has been to ask every client to set the config
parameters `remote.<name>.receivepack` and `remote.<name>.uploadpack`. But
telling *every* client to do so is a pain...
Gitolite lets you specify the directory in which git binaries are to be found,
via a new variable (`$GIT_PATH`) in the "rc" file. If this variable is
non-empty, it will be appended to the PATH environment variable before
attempting to run git stuff.
Very easy, very simple, and completely transparent to the users :-)
<a name="myrights"></a>
#### what repos do I have access to?
Sometimes there are too many repos, maybe even named similarly, or with the
potential for typos, confusion about hyphens/underscores or upper/lower case,
etc. You'd just like a simple way to know what repos you have access to.
Easy! Just use ssh and try to log in as if you were attempting to get a
shell:
$ ssh gitolite info
PTY allocation request failed on channel 0
hello sitaram, the gitolite version here is v0.6-17-g94ed189
you have the following permissions:
R W Anu-WSD
R ROtest
R W SecureBrowse
R W entrans
R W git-notes
R W gitolite
R W gitolite-admin
R W indic_web_input
R W proxy
@ @ testing
R W vkc
Note that until this version, we used to put out an ugly `need
SSH_ORIGINAL_COMMAND` error, just like gitosis used to. All we did is put
that code path to better use :-)
#### "exclude" (or "deny") rules
Here is an illustrative explanation of "deny" rules. However, please be sure
to read the "DENY/EXCLUDE RULES" section in `conf/example.conf` for important
notes/caveats before using "deny" rules.
Take a look at the following snippet, which *seems* to say that "bruce" can
write versioned tags (anything containing `refs/tags/v[0-9]`), but the other
staffers can't:
@staff = bruce whitfield martin
[... and later ...]
RW refs/tags/v[0-9] = bruce
RW refs/tags = @staff
But that's not how the matching works. As long as any refex matches the
refname being updated, it's a "yes". Since the second refex (which says
"anything containing `refs/tags`") is a superset of the first one, it lets
anyone on `@staff` create versioned tags, not just Bruce.
One way to fix this is to allow "excludes" -- some changes in syntax, combined
with a rigorous, ordered, interpretation would do it.
Let's recap the **existing semantics**:
> the first matching refex that has the permission you're looking for (`W`
> or `+`), results in success. A fallthrough results in failure
Here are the **new semantics**, with changes from the "main" one in bold:
> the first matching refex that has the permission you're looking for (`W`
> or `+`) **or a minus (`-`)**, results in success **or failure,
> respectively**. A fallthrough **also** results in failure
So the example we started with becomes, if you use "deny" rules:
RW refs/tags/v[0-9] = bruce
- refs/tags/v[0-9] = @staff
RW refs/tags = @staff
And here's how it works:
* for non-version tags, only the 3rd rule matches, so anyone on staff can
push them
* for version tags by bruce, the first rule matches so he can push them
* for version tags by staffers *other than bruce*, the second rule matches
before the third one, and it has a `-` as the permission, so the push
fails
#### "personal" branches
"personal" branches are great for corporate environments, where
unauthenticated pull/clone is a no-no. Since a dev workstation cannot do
authentication, even work shared just between 2 devs has to go *via* the
server. This causes the same branch name clutter as in a centralised VCS,
plus setting up permissions for this becomes a chore for the admin.
gitolite lets you define a "personal" or "scratch" namespace prefix for
each developer (e.g., `refs/personal/<devname>/*`), with full
permissions for that dev and read-only for everyone else. And you get
this without adding a single line to the access config file -- pretty
much fire and forget as far as the admin is concerned, even if there is
constant churn in the project teams.
Not bad for something that took just *one* line of code to implement.
And that's one clean, readable, line, by the way ;-)
The admin would set `$PERSONAL_BRANCH_PREFIX` in the rc file and communicate
this to all users. It could be something like `refs/heads/personal`, which
means all such branches will show up in `git branch` lookups and `git clone`
will fetch them. Or he could use, say, `refs/personal`, which means it won't
show up in any normal "branch-y" commands and stuff, and generally be much
less noisy.
**Note that a user who has NO write access cannot have personal branches**; if
you read the section (above) on "two levels of access rights checking" you'll
understand why.
For instance, in the following example, `user3` cannot push to any
`refs/heads/personal/user3/*` branches because the first level check stops him
cold:
# assume $PERSONAL = 'refs/heads/personal' in ~/.gitolite.rc
repo myrepo
RW+ master = sitaram
RW+ release = qa_guy
RW = user1 user2
R = user3
If we relax that check, *any* access becomes *write* access. Yes it will be
caught later, by the hook, but it's good practice to catch things in multiple
places.
If you want `user3` to have his own personal branch, but without write access
to any of the "real" branches (like "master", "release", etc.), just use a
dummy branch. Choose a name that will never exist in practice, or even if
someone creates it, we don't care. For example, this will get him past the
first check:
RW dummy = user3
Just don't *show* the user this config file; it might sound insulting :-)
#### custom hooks and custom git config
You can specify hooks that you want to propagate to all repos, as well as
per-repo "gitconfig" settings. Please see `doc/2-admin.mkd` and
`conf/example.conf` for details.
#### access control for external commands
Gitolite now has a mechanism for allowing access control for arbitrary
external commands, as long as they are invoked via ssh and present a
server-side command that contains enough information to make an access control
decision. The first (and only, so far) such command implemented is rsync.
Note that this is incompatible with giving people shell access as described in
`doc/6-ssh-troubleshooting.mkd` -- people who have shell access are not
subject to this mechanism (it wouldn't make sense to try and control someone
who has shell access anyway).
Please see the config files (both of them) for examples and usage.
### design choices
#### keeping the parser and the access control separate
There are two programs concerned with access control:
* `gl-auth-command`, the program that is run via `~/.ssh/authorized_keys`;
this decides whether git should even be allowed to run (basic R/W/no
access). (This one cannot decide on the branch-level access; it is not
known at this point what branch is being accessed)
* the update-hook on each repo, which decides the per-branch permissions
I have chosen to keep the relatively complex task of parsing the config file
out of them to keep them simpler (and faster). So any changes to the config
have to be first "compiled", and the access control programs use this
"compiled" version of the config. (The compile step also refreshes
`~/.ssh/authorized_keys`).
If you choose the "easy install" method, all this is quite transparent to you
anyway. If you cannot use the easy install and must install manually, I have
clear instructions on how to set it up.
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