stockholm/modules/tv/git.nix

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{ config, lib, pkgs, ... }:
let
inherit (builtins)
attrNames concatLists filter hasAttr head lessThan removeAttrs tail toJSON
typeOf;
inherit (lib)
concatStrings concatStringsSep escapeShellArg hasPrefix listToAttrs
makeSearchPath mapAttrsToList mkIf mkOption removePrefix singleton
sort types unique;
inherit (pkgs) linkFarm writeScript writeText;
ensureList = x:
if typeOf x == "list" then x else [x];
getName = x: x.name;
makeAuthorizedKey = command-script: user@{ name, pubkey }:
# TODO assert name
# TODO assert pubkey
let
options = concatStringsSep "," [
''command="exec ${command-script} ${name}"''
"no-agent-forwarding"
"no-port-forwarding"
"no-pty"
"no-X11-forwarding"
];
in
"${options} ${pubkey}";
# [case-pattern] -> shell-script
# Create a shell script that succeeds (exit 0) when all its arguments
# match the case patterns (in the given order).
makeAuthorizeScript =
let
# TODO escape
to-pattern = x: concatStringsSep "|" (ensureList x);
go = i: ps:
if ps == []
then "exit 0"
else ''
case ''$${toString i} in ${to-pattern (head ps)})
${go (i + 1) (tail ps)}
esac'';
in
patterns: ''
#! /bin/sh
set -euf
${concatStringsSep "\n" (map (go 1) patterns)}
exit -1
'';
reponames = rules: sort lessThan (unique (map (x: x.repo.name) rules));
toShellArgs = xs: toString (map escapeShellArg xs);
# TODO makeGitHooks that uses runCommand instead of scriptFarm?
scriptFarm =
farm-name: scripts:
let
makeScript = script-name: script-string: {
name = script-name;
path = writeScript "${farm-name}_${script-name}" script-string;
};
in
linkFarm farm-name (mapAttrsToList makeScript scripts);
writeJSON = name: data: writeText name (toJSON data);
cfg = config.services.git;
in
# TODO unify logging of shell scripts to user and journal
# TODO move all scripts to ${etcDir}, so ControlMaster connections
# immediately pick up new authenticators
# TODO when authorized_keys changes, then restart ssh
# (or kill already connected users somehow)
{
options.services.git = {
enable = mkOption {
type = types.bool;
default = false;
description = "Enable Git repository hosting.";
};
dataDir = mkOption {
type = types.str;
default = "/var/lib/git";
description = "Directory used to store repositories.";
};
etcDir = mkOption {
type = types.str;
default = "/etc/git-ssh";
};
rules = mkOption {
type = types.unspecified;
};
repos = mkOption {
type = types.unspecified;
};
users = mkOption {
type = types.unspecified;
};
};
config =
let
command-script = writeScript "git-ssh-command" ''
#! /bin/sh
set -euf
PATH=${makeSearchPath "bin" (with pkgs; [
coreutils
git
gnugrep
gnused
systemd
])}
abort() {
echo "error: $1" >&2
systemd-cat -p err -t git-ssh echo "error: $1"
exit -1
}
GIT_SSH_USER=$1
systemd-cat -p info -t git-ssh echo \
"authorizing $GIT_SSH_USER $SSH_CONNECTION $SSH_ORIGINAL_COMMAND"
# References: The Base Definitions volume of
# POSIX.12013, Section 3.278, Portable Filename Character Set
portable_filename_bre="^[A-Za-z0-9._-]\\+$"
command=$(echo "$SSH_ORIGINAL_COMMAND" \
| sed -n 's/^\([^ ]*\) '"'"'\(.*\)'"'"'/\1/p' \
| grep "$portable_filename_bre" \
|| abort 'cannot read command')
GIT_SSH_REPO=$(echo "$SSH_ORIGINAL_COMMAND" \
| sed -n 's/^\([^ ]*\) '"'"'\(.*\)'"'"'/\2/p' \
| grep "$portable_filename_bre" \
|| abort 'cannot read reponame')
${cfg.etcDir}/authorize-command \
"$GIT_SSH_USER" "$GIT_SSH_REPO" "$command" \
|| abort 'access denied'
repodir=${escapeShellArg cfg.dataDir}/$GIT_SSH_REPO
systemd-cat -p info -t git-ssh \
echo "authorized exec $command $repodir"
export GIT_SSH_USER
export GIT_SSH_REPO
exec "$command" "$repodir"
'';
init-script = writeScript "git-ssh-init" ''
#! /bin/sh
set -euf
PATH=${makeSearchPath "bin" (with pkgs; [
coreutils
findutils
gawk
git
])}
dataDir=${escapeShellArg cfg.dataDir}
mkdir -p "$dataDir"
for reponame in ${toShellArgs (reponames cfg.rules)}; do
repodir=$dataDir/$reponame
if ! test -d "$repodir"; then
mkdir -m 0700 "$repodir"
git init --bare --template=/var/empty "$repodir"
chown -R git: "$repodir"
# branches/
# description
# hooks/
# info/
fi
ln -snf ${hooks} "$repodir/hooks"
done
'';
# TODO repo-specific hooks
hooks = scriptFarm "git-ssh-hooks" {
pre-receive = ''
#! /bin/sh
set -euf
PATH=${makeSearchPath "bin" (with pkgs; [
coreutils # env
git
systemd
])}
accept() {
#systemd-cat -p info -t git-ssh echo "authorized $1"
accept_string="''${accept_string+$accept_string
}authorized $1"
}
reject() {
#systemd-cat -p err -t git-ssh echo "denied $1"
#echo 'access denied' >&2
#exit_code=-1
reject_string="''${reject_string+$reject_string
}access denied: $1"
}
empty=0000000000000000000000000000000000000000
accept_string=
reject_string=
while read oldrev newrev ref; do
if [ $oldrev = $empty ]; then
receive_mode=create
elif [ $newrev = $empty ]; then
receive_mode=delete
elif [ "$(git merge-base $oldrev $newrev)" = $oldrev ]; then
receive_mode=fast-forward
else
receive_mode=non-fast-forward
fi
if ${cfg.etcDir}/authorize-push \
"$GIT_SSH_USER" "$GIT_SSH_REPO" "$ref" "$receive_mode"; then
accept "$receive_mode $ref"
else
reject "$receive_mode $ref"
fi
done
if [ -n "$reject_string" ]; then
systemd-cat -p err -t git-ssh echo "$reject_string"
exit -1
fi
systemd-cat -p info -t git-ssh echo "$accept_string"
'';
update = ''
#! /bin/sh
set -euf
echo update hook: $* >&2
'';
post-update = ''
#! /bin/sh
set -euf
echo post-update hook: $* >&2
'';
};
etc-base =
assert (hasPrefix "/etc/" cfg.etcDir);
removePrefix "/etc/" cfg.etcDir;
in
mkIf cfg.enable {
system.activationScripts.git-ssh-init = "${init-script}";
# TODO maybe put all scripts here and then use PATH?
environment.etc."${etc-base}".source =
scriptFarm "git-ssh-authorizers" {
authorize-command = makeAuthorizeScript (map ({ repo, user, perm }: [
(map getName (ensureList user))
(map getName (ensureList repo))
(map getName perm.allow-commands)
]) cfg.rules);
authorize-push = makeAuthorizeScript (map ({ repo, user, perm }: [
(map getName (ensureList user))
(map getName (ensureList repo))
(ensureList perm.allow-receive-ref)
(map getName perm.allow-receive-modes)
]) (filter (x: hasAttr "allow-receive-ref" x.perm) cfg.rules));
};
users.extraUsers = singleton {
description = "Git repository hosting user";
name = "git";
shell = "/bin/sh";
openssh.authorizedKeys.keys =
mapAttrsToList (_: makeAuthorizedKey command-script) cfg.users;
uid = 112606723; # genid git
};
};
}