293 lines
8.1 KiB
Nix
293 lines
8.1 KiB
Nix
{ config, lib, pkgs, ... }:
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let
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inherit (builtins)
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attrNames concatLists filter hasAttr head lessThan removeAttrs tail toJSON
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typeOf;
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inherit (lib)
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concatStrings concatStringsSep escapeShellArg hasPrefix listToAttrs
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makeSearchPath mapAttrsToList mkIf mkOption removePrefix singleton
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sort types unique;
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inherit (pkgs) linkFarm writeScript writeText;
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ensureList = x:
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if typeOf x == "list" then x else [x];
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getName = x: x.name;
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makeAuthorizedKey = command-script: user@{ name, pubkey }:
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# TODO assert name
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# TODO assert pubkey
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let
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options = concatStringsSep "," [
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''command="exec ${command-script} ${name}"''
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"no-agent-forwarding"
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"no-port-forwarding"
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"no-pty"
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"no-X11-forwarding"
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];
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in
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"${options} ${pubkey}";
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# [case-pattern] -> shell-script
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# Create a shell script that succeeds (exit 0) when all its arguments
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# match the case patterns (in the given order).
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makeAuthorizeScript =
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let
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# TODO escape
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to-pattern = x: concatStringsSep "|" (ensureList x);
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go = i: ps:
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if ps == []
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then "exit 0"
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else ''
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case ''$${toString i} in ${to-pattern (head ps)})
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${go (i + 1) (tail ps)}
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esac'';
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in
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patterns: ''
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#! /bin/sh
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set -euf
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${concatStringsSep "\n" (map (go 1) patterns)}
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exit -1
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'';
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reponames = rules: sort lessThan (unique (map (x: x.repo.name) rules));
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toShellArgs = xs: toString (map escapeShellArg xs);
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# TODO makeGitHooks that uses runCommand instead of scriptFarm?
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scriptFarm =
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farm-name: scripts:
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let
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makeScript = script-name: script-string: {
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name = script-name;
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path = writeScript "${farm-name}_${script-name}" script-string;
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};
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in
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linkFarm farm-name (mapAttrsToList makeScript scripts);
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writeJSON = name: data: writeText name (toJSON data);
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cfg = config.services.git;
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in
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# TODO unify logging of shell scripts to user and journal
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# TODO move all scripts to ${etcDir}, so ControlMaster connections
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# immediately pick up new authenticators
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# TODO when authorized_keys changes, then restart ssh
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# (or kill already connected users somehow)
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{
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options.services.git = {
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enable = mkOption {
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type = types.bool;
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default = false;
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description = "Enable Git repository hosting.";
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};
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dataDir = mkOption {
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type = types.str;
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default = "/var/lib/git";
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description = "Directory used to store repositories.";
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};
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etcDir = mkOption {
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type = types.str;
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default = "/etc/git-ssh";
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};
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rules = mkOption {
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type = types.unspecified;
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};
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repos = mkOption {
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type = types.unspecified;
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};
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users = mkOption {
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type = types.unspecified;
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};
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};
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config =
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let
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command-script = writeScript "git-ssh-command" ''
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#! /bin/sh
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set -euf
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PATH=${makeSearchPath "bin" (with pkgs; [
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coreutils
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git
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gnugrep
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gnused
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systemd
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])}
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abort() {
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echo "error: $1" >&2
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systemd-cat -p err -t git-ssh echo "error: $1"
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exit -1
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}
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GIT_SSH_USER=$1
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systemd-cat -p info -t git-ssh echo \
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"authorizing $GIT_SSH_USER $SSH_CONNECTION $SSH_ORIGINAL_COMMAND"
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# References: The Base Definitions volume of
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# POSIX.1‐2013, Section 3.278, Portable Filename Character Set
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portable_filename_bre="^[A-Za-z0-9._-]\\+$"
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command=$(echo "$SSH_ORIGINAL_COMMAND" \
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| sed -n 's/^\([^ ]*\) '"'"'\(.*\)'"'"'/\1/p' \
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| grep "$portable_filename_bre" \
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|| abort 'cannot read command')
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GIT_SSH_REPO=$(echo "$SSH_ORIGINAL_COMMAND" \
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| sed -n 's/^\([^ ]*\) '"'"'\(.*\)'"'"'/\2/p' \
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| grep "$portable_filename_bre" \
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|| abort 'cannot read reponame')
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${cfg.etcDir}/authorize-command \
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"$GIT_SSH_USER" "$GIT_SSH_REPO" "$command" \
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|| abort 'access denied'
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repodir=${escapeShellArg cfg.dataDir}/$GIT_SSH_REPO
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systemd-cat -p info -t git-ssh \
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echo "authorized exec $command $repodir"
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export GIT_SSH_USER
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export GIT_SSH_REPO
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exec "$command" "$repodir"
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'';
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init-script = writeScript "git-ssh-init" ''
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#! /bin/sh
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set -euf
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PATH=${makeSearchPath "bin" (with pkgs; [
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coreutils
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findutils
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gawk
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git
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])}
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dataDir=${escapeShellArg cfg.dataDir}
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mkdir -p "$dataDir"
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for reponame in ${toShellArgs (reponames cfg.rules)}; do
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repodir=$dataDir/$reponame
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if ! test -d "$repodir"; then
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mkdir -m 0700 "$repodir"
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git init --bare --template=/var/empty "$repodir"
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chown -R git: "$repodir"
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# branches/
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# description
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# hooks/
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# info/
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fi
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ln -snf ${hooks} "$repodir/hooks"
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done
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'';
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# TODO repo-specific hooks
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hooks = scriptFarm "git-ssh-hooks" {
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pre-receive = ''
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#! /bin/sh
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set -euf
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PATH=${makeSearchPath "bin" (with pkgs; [
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coreutils # env
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git
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systemd
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])}
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accept() {
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#systemd-cat -p info -t git-ssh echo "authorized $1"
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accept_string="''${accept_string+$accept_string
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}authorized $1"
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}
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reject() {
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#systemd-cat -p err -t git-ssh echo "denied $1"
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#echo 'access denied' >&2
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#exit_code=-1
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reject_string="''${reject_string+$reject_string
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}access denied: $1"
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}
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empty=0000000000000000000000000000000000000000
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accept_string=
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reject_string=
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while read oldrev newrev ref; do
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if [ $oldrev = $empty ]; then
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receive_mode=create
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elif [ $newrev = $empty ]; then
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receive_mode=delete
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elif [ "$(git merge-base $oldrev $newrev)" = $oldrev ]; then
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receive_mode=fast-forward
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else
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receive_mode=non-fast-forward
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fi
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if ${cfg.etcDir}/authorize-push \
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"$GIT_SSH_USER" "$GIT_SSH_REPO" "$ref" "$receive_mode"; then
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accept "$receive_mode $ref"
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else
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reject "$receive_mode $ref"
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fi
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done
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if [ -n "$reject_string" ]; then
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systemd-cat -p err -t git-ssh echo "$reject_string"
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exit -1
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fi
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systemd-cat -p info -t git-ssh echo "$accept_string"
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'';
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update = ''
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#! /bin/sh
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set -euf
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echo update hook: $* >&2
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'';
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post-update = ''
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#! /bin/sh
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set -euf
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echo post-update hook: $* >&2
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'';
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};
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etc-base =
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assert (hasPrefix "/etc/" cfg.etcDir);
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removePrefix "/etc/" cfg.etcDir;
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in
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mkIf cfg.enable {
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system.activationScripts.git-ssh-init = "${init-script}";
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# TODO maybe put all scripts here and then use PATH?
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environment.etc."${etc-base}".source =
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scriptFarm "git-ssh-authorizers" {
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authorize-command = makeAuthorizeScript (map ({ repo, user, perm }: [
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(map getName (ensureList user))
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(map getName (ensureList repo))
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(map getName perm.allow-commands)
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]) cfg.rules);
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authorize-push = makeAuthorizeScript (map ({ repo, user, perm }: [
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(map getName (ensureList user))
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(map getName (ensureList repo))
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(ensureList perm.allow-receive-ref)
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(map getName perm.allow-receive-modes)
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]) (filter (x: hasAttr "allow-receive-ref" x.perm) cfg.rules));
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};
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users.extraUsers = singleton {
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description = "Git repository hosting user";
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name = "git";
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shell = "/bin/sh";
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openssh.authorizedKeys.keys =
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mapAttrsToList (_: makeAuthorizedKey command-script) cfg.users;
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uid = 112606723; # genid git
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};
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};
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}
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