*/krebs -> krebs/*

17 files changed, 1735 insertions, 0 deletions

diff --git a/krebs/3modules/default.nix b/krebs/3modules/default.nix
new file mode 100644
index 000000000..cd9cd732b
--- /dev/null
+++ b/krebs/3modules/default.nix
@@ -0,0 +1,407 @@
+{ config, lib, ... }:
+
+with import ../4lib { inherit lib; };
+let
+  cfg = config.krebs;
+
+  out = {
+    imports = [
+      ./github-hosts-sync.nix
+      ./git.nix
+      ./nginx.nix
+      ./retiolum.nix
+      ./urlwatch.nix
+    ];
+    options.krebs = api;
+    config = mkIf cfg.enable imp;
+  };
+
+  api = {
+    enable = mkEnableOption "krebs";
+
+    build = mkOption {
+      type = types.submodule ({ config, ... }: {
+        options = {
+          target = mkOption {
+            type = with types; nullOr str;
+            default = null;
+          };
+          deps = mkOption {
+            type = with types; attrsOf (submodule {
+              options = {
+                url = mkOption {
+                  type = str;
+                };
+                rev = mkOption {
+                  type = nullOr str;
+                  default = null;
+                };
+              };
+            });
+            default = {};
+          };
+          script = mkOption {
+            type = types.str;
+            default = ''
+              #! /bin/sh
+              set -efux
+
+              target=${escapeShellArg cfg.build.target}
+
+              push(){(
+                src=$1/
+                dst=$target:$2
+                rsync \
+                  --exclude .git \
+                  --exclude .graveyard \
+                  --exclude old \
+                  --rsync-path="mkdir -p \"$dst\" && rsync" \
+                  --usermap=\*:0 \
+                  --groupmap=\*:0 \
+                  --delete-excluded \
+                  -vrLptgoD \
+                  "$src" "$dst"
+              )}
+
+              ${concatStrings (mapAttrsToList (name: { url, rev, ... }:
+                optionalString (rev == null) ''
+                  push ${toString (map escapeShellArg [
+                    "${url}"
+                    "/root/src/${name}"
+                  ])}
+                '') config.deps)}
+
+              exec ssh -S none "$target" /bin/sh <<\EOF
+              set -efux
+              fetch(){(
+                url=$1
+                rev=$2
+                dst=$3
+                mkdir -p "$dst"
+                cd "$dst"
+                if ! test -e .git; then
+                  git init
+                fi
+                if ! cur_url=$(git config remote.origin.url 2>/dev/null); then
+                  git remote add origin "$url"
+                elif test "$cur_url" != "$url"; then
+                  git remote set-url origin "$url"
+                fi
+                if test "$(git rev-parse --verify HEAD 2>/dev/null)" != "$rev"; then
+                  git fetch origin
+                  git checkout "$rev" -- .
+                  git checkout -q "$rev"
+                  git submodule init
+                  git submodule update
+                fi
+                git clean -dxf
+              )}
+
+              ${concatStrings (mapAttrsToList (name: { url, rev, ... }:
+                optionalString (rev != null) ''
+                  fetch ${toString (map escapeShellArg [
+                    url
+                    rev
+                    "/root/src/${name}"
+                  ])}
+                '') config.deps)}
+
+              echo build system...
+              profile=/nix/var/nix/profiles/system
+              NIX_PATH=/root/src \
+              nix-env \
+                -Q \
+                -p "$profile" \
+                -f '<stockholm>' \
+                --set \
+                -A system \
+                --argstr user-name ${escapeShellArg cfg.build.user.name} \
+                --argstr system-name ${escapeShellArg cfg.build.host.name}
+
+              exec "$profile"/bin/switch-to-configuration switch
+              EOF
+            '';
+          };
+          host = mkOption {
+            type = types.host;
+          };
+          user = mkOption {
+            type = types.user;
+          };
+        };
+      });
+      # Define defaul value, so unset values of the submodule get reported.
+      default = {};
+    };
+
+    dns = {
+      providers = mkOption {
+        # TODO with types; tree dns.label dns.provider, so we can merge.
+        # Currently providers can only be merged if aliases occur just once.
+        type = with types; attrsOf unspecified;
+      };
+    };
+
+    hosts = mkOption {
+      type = with types; attrsOf host;
+    };
+
+    users = mkOption {
+      type = with types; attrsOf user;
+    };
+
+    # XXX is there a better place to define search-domain?
+    # TODO search-domains :: listOf hostname
+    search-domain = mkOption {
+      type = types.hostname;
+      default = "retiolum";
+    };
+  };
+
+  imp = mkMerge [
+    { krebs = lass-imp; }
+    { krebs = makefu-imp; }
+    { krebs = tv-imp; }
+    {
+      krebs.dns.providers = {
+        de.krebsco = "ovh";
+        internet = "hosts";
+        retiolum = "hosts";
+      };
+
+      # XXX This overlaps with krebs.retiolum
+      networking.extraHosts = concatStringsSep "\n" (flatten (
+        mapAttrsToList (hostname: host:
+          mapAttrsToList (netname: net:
+            let
+              aliases = toString (unique (longs ++ shorts));
+              providers = dns.split-by-provider net.aliases cfg.dns.providers;
+              longs = providers.hosts;
+              shorts = map (removeSuffix ".${cfg.search-domain}") longs;
+            in
+            map (addr: "${addr} ${aliases}") net.addrs
+          ) host.nets
+        ) cfg.hosts
+      ));
+    }
+  ];
+
+  lass-imp = {
+    hosts = addNames {
+    };
+    users = addNames {
+      lass = {
+        pubkey = readFile ../../Zpubkeys/lass.ssh.pub;
+      };
+      uriel = {
+        pubkey = readFile ../../Zpubkeys/uriel.ssh.pub;
+      };
+    };
+  };
+
+  makefu-imp = {
+    hosts = addNames {
+      pnp = {
+        cores = 1;
+        dc = "makefu"; #vm on 'omo'
+        nets = {
+          retiolum = {
+            addrs4 = ["10.243.0.210"];
+            addrs6 = ["42:f9f1:0000:0000:0000:0000:0000:0001"];
+            aliases = [
+              "pnp.retiolum"
+              "cgit.pnp.retiolum"
+            ];
+            tinc.pubkey = ''
+              -----BEGIN RSA PUBLIC KEY-----
+              MIIBCgKCAQEAugkgEK4iy2C5+VZHwhjj/q3IOhhazE3TYHuipz37KxHWX8ZbjH+g
+              Ewtm79dVysujAOX8ZqV8nD8JgDAvkIZDp8FCIK0/rgckhpTsy1HVlHxa7ECrOS8V
+              pGz4xOxgcPFRbv5H2coHtbnfQc4GdA5fcNedQ3BP3T2Tn7n/dbbVs30bOP5V0EMR
+              SqZwNmtqaDQxOvjpPg9EoHvAYTevrpbbIst9UzCyvmNli9R+SsiDrzEPgB7zOc4T
+              TG12MT+XQr6JUu4jPpzdhb6H/36V6ADCIkBjzWh0iSfWGiFDQFinD+YSWbA1NOTr
+              Qtd1I3Ov+He7uc2Z719mb0Og2kCGnCnPIwIDAQAB
+              -----END RSA PUBLIC KEY-----
+              '';
+          };
+        };
+      };
+    };
+    users = addNames {
+      makefu = {
+        mail = "root@euer.krebsco.de";
+        pubkey = readFile ../../Zpubkeys/makefu_arch.ssh.pub;
+      };
+    };
+  };
+
+  tv-imp = {
+    dns.providers = {
+      de.viljetic = "regfish";
+    };
+    hosts = addNames {
+      cd = {
+        cores = 2;
+        dc = "tv"; #dc = "cac";
+        nets = rec {
+          internet = {
+            addrs4 = ["162.219.7.216"];
+            aliases = [
+              "cd.internet"
+              "cd.viljetic.de"
+              "cgit.cd.viljetic.de"
+              "cd.krebsco.de"
+            ];
+          };
+          retiolum = {
+            via = internet;
+            addrs4 = ["10.243.113.222"];
+            addrs6 = ["42:4522:25f8:36bb:8ccb:0150:231a:2af3"];
+            aliases = [
+              "cd.retiolum"
+              "cgit.cd.retiolum"
+            ];
+            tinc.pubkey = ''
+              -----BEGIN RSA PUBLIC KEY-----
+              MIICCgKCAgEAvmCBVNKT/Su4v9nl/Nm3STPo5QxWPg7xEkzIs3Oh39BS8+r6/7UQ
+              rebib7mczb+ebZd+Rg2yFoGrWO8cmM0VcLy5bYRMK7in8XroLEjWecNNM4TRfNR4
+              e53+LhcPdkxo0A3/D+yiut+A2Mkqe+4VXDm/JhAiAYkZTn7jUtj00Atrc7CWW1gN
+              sP3jIgv4+CGftdSYOB4dm699B7OD9XDLci2kOaFqFl4cjDYUok03G0AduUlRx10v
+              CKbKOTIdm8C36A902/3ms+Hyzkruu+VagGIZuPSwqXHJPCu7Ju+jarKQstMmpQi0
+              PubweWDL0o/Dfz2qT3DuL4xDecIvGE6kv3m41hHJYiK+2/azTSehyPFbsVbL7w0V
+              LgKN3usnZNcpTsBWxRGT7nMFSnX2FLDu7d9OfCuaXYxHVFLZaNrpccOq8NF/7Hbk
+              DDW81W7CvLyJDlp0WLnAawSOGTUTPoYv/2wAapJ89i8QGCueGvEc6o2EcnBVMFEW
+              ejWTQzyD816f4RsplnrRqLVlIMbr9Q/n5TvlgjjhX7IMEfMy4+7qLGRQkNbFzgwK
+              jxNG2fFSCjOEQitm0gAtx7QRIyvYr6c7/xiHz4AwxYzBmvQsL/OK57NO4+Krwgj5
+              Vk8TQ2jGO7J4bB38zaxK+Lrtfl8i1AK1171JqFMhOc34JSJ7T4LWDMECAwEAAQ==
+              -----END RSA PUBLIC KEY-----
+            '';
+          };
+        };
+      };
+      mkdir = {
+        cores = 1;
+        dc = "tv"; #dc = "cac";
+        nets = rec {
+          internet = {
+            addrs4 = ["162.248.167.241"];
+            aliases = [
+              "mkdir.internet"
+            ];
+          };
+          retiolum = {
+            via = internet;
+            addrs4 = ["10.243.113.223"];
+            addrs6 = ["42:4522:25f8:36bb:8ccb:0150:231a:2af4"];
+            aliases = [
+              "mkdir.retiolum"
+              "cgit.mkdir.retiolum"
+            ];
+            tinc.pubkey = ''
+              -----BEGIN RSA PUBLIC KEY-----
+              MIIBCgKCAQEAuyfM+3od75zOYXqnqRMAt+yp/4z/vC3vSWdjUvEmCuM23c5BOBw+
+              dKqbWoSPTzOuaQ0szdL7a6YxT+poSUXd/i3pPz59KgCl192rd1pZoJKgvoluITev
+              voYSP9rFQOUrustfDb9qKW/ZY95cwdCvypo7Vf4ghxwDCnlmyCGz7qXTJMLydNKF
+              2PH9KiY4suv15sCg/zisu+q0ZYQXUc1TcgpoIYBOftDunOJoNdbti+XjwWdjGmJZ
+              Bn4GelsrrpwJFvfDmouHUe8GsD7nTgbZFtiJbKfCEiK16N0Q0d0ZFHhAV2nPjsk2
+              3JhG4n9vxATBkO82f7RLrcrhkx9cbLfN3wIDAQAB
+              -----END RSA PUBLIC KEY-----
+            '';
+          };
+        };
+      };
+      nomic = {
+        cores = 2;
+        dc = "tv"; #dc = "gg23";
+        nets = rec {
+          retiolum = {
+            addrs4 = ["10.243.0.110"];
+            addrs6 = ["42:02d5:733f:d6da:c0f5:2bb7:2b18:09ec"];
+            aliases = [
+              "nomic.retiolum"
+              "cgit.nomic.retiolum"
+            ];
+            tinc.pubkey = ''
+              -----BEGIN RSA PUBLIC KEY-----
+              MIIBCgKCAQEAwb8Yk/YRc17g2J9n960p6j4W/l559OPyuMPdGJ4DmCm3WNQtxoa+
+              qTFUiDiI85BcmfqnSeddLG8zTC2XnSlIvCRMJ9oKzppFM4PX4OTAaJZVE5WyCQhw
+              Kd4tHVdoQgJW5yFepmT9IUmHqkxXJ0R2W93l2eSZNOcnFvFn0ooiAlRi4zAiHClu
+              5Mz80Sc2rvez+n9wtC2D06aYjP23pHYld2xighHR9SUqX1dFzgSXNSoWWCcgNp2a
+              OKcM8LzxLV7MTMZFOJCJndZ77e4LsUvxhQFP6nyKZWg30PC0zufZsuN5o2xsWSlA
+              Wi9sMB1AUR6mZrxgcgTFpUjbjbLQf+36CwIDAQAB
+              -----END RSA PUBLIC KEY-----
+            '';
+          };
+        };
+        secure = true;
+      };
+      rmdir = {
+        cores = 1;
+        dc = "tv"; #dc = "cac";
+        nets = rec {
+          internet = {
+            addrs4 = ["167.88.44.94"];
+            aliases = [
+              "rmdir.internet"
+            ];
+          };
+          retiolum = {
+            via = internet;
+            addrs4 = ["10.243.113.224"];
+            addrs6 = ["42:4522:25f8:36bb:8ccb:0150:231a:2af5"];
+            aliases = [
+              "rmdir.retiolum"
+              "cgit.rmdir.retiolum"
+            ];
+            tinc.pubkey = ''
+              -----BEGIN RSA PUBLIC KEY-----
+              MIIBCgKCAQEA+twy4obSbJdmZLfBoe9YYeyoDnXkO/WPa2D6Eh6jXrWk5fbhBjRf
+              i3EAQfLiXXFJX3E8V8YvJyazXklI19jJtCLDiu/F5kgJJfyAkWHH+a/hcg7qllDM
+              Xx2CvS/nCbs+p48/VLO6zLC7b1oHu3K/ob5M5bwPK6j9NEDIL5qYiM5PQzV6zryz
+              hS9E/+l8Z+UUpYcfS3bRovXJAerB4txc/gD3Xmptq1zk53yn1kJFYfVlwyyz+NEF
+              59JZj2PDrvWoG0kx/QjiNurs6XfdnyHe/gP3rmSTrihKFVuA3cZM62sDR4FcaeWH
+              SnKSp02pqjBOjC/dOK97nXpKLJgNH046owIDAQAB
+              -----END RSA PUBLIC KEY-----
+            '';
+          };
+        };
+      };
+      wu = {
+        cores = 4;
+        # TODO wu is mobile, so dc means "home data center"
+        dc = "tv"; #dc = "gg23";
+        nets = {
+          retiolum = {
+            addrs4 = ["10.243.13.37"];
+            addrs6 = ["42:0:0:0:0:0:0:1337"];
+            aliases = [
+              "wu.retiolum"
+            ];
+            tinc.pubkey = ''
+              -----BEGIN RSA PUBLIC KEY-----
+              MIIBCgKCAQEArDvU0cuBsVqTjCX2TlWL4XHSy4qSjUhjrDvUPZSKTVN7x6OENCUn
+              M27g9H7j4/Jw/8IHoJLiKnXHavOoc9UJM+P9Fla/4TTVADr69UDSnLgH+wGiHcEg
+              GxPkb2jt0Z8zcpD6Fusj1ATs3sssaLHTHvg1D0LylEWA3cI4WPP13v23PkyUENQT
+              KpSWfR+obqDl38Q7LuFi6dH9ruyvqK+4syddrBwjPXrcNxcGL9QbDn7+foRNiWw4
+              4CE5z25oGG2iWMShI7fe3ji/fMUAl7DSOOrHVVG9eMtpzy+uI8veOHrdTax4oKik
+              AFGCrMIov3F0GIeu3nDlrTIZPZDTodbFKQIDAQAB
+              -----END RSA PUBLIC KEY-----
+            '';
+          };
+        };
+        secure = true;
+      };
+    };
+    users = addNames {
+      mv = {
+        mail = "mv@cd.retiolum";
+        pubkey = readFile ../../Zpubkeys/mv_vod.ssh.pub;
+      };
+      tv = {
+        mail = "tv@wu.retiolum";
+        pubkey = readFile ../../Zpubkeys/tv_wu.ssh.pub;
+      };
+    };
+  };
+
+in
+out
diff --git a/krebs/3modules/git.nix b/krebs/3modules/git.nix
new file mode 100644
index 000000000..64b7820b2
--- /dev/null
+++ b/krebs/3modules/git.nix
@@ -0,0 +1,486 @@
+{ config, pkgs, lib, ... }:
+
+# 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)
+
+with import ../4lib { inherit lib; };
+let
+  cfg = config.krebs.git;
+
+  out = {
+    options.krebs.git = api;
+    config = mkIf cfg.enable (mkMerge [
+      (mkIf cfg.cgit cgit-imp)
+      git-imp
+    ]);
+  };
+
+  api = {
+    enable = mkEnableOption "krebs.git";
+
+    cgit = mkOption {
+      type = types.bool;
+      default = true;
+      description = ''
+          Enable cgit.
+          Cgit is an attempt to create a fast web interface for the git version
+          control system, using a built in cache to decrease pressure on the 
+          git server.
+          cgit in this module is being served via fastcgi nginx.This module
+          deploys a http://cgit.<hostname> nginx configuration and enables nginx
+          if not yet enabled.
+          '';
+    };
+    dataDir = mkOption {
+      type = types.str;
+      default = "/var/lib/git";
+      description = "Directory used to store repositories.";
+    };
+    etcDir = mkOption {
+      type = types.str;
+      default = "/etc/git";
+    };
+    repos = mkOption {
+      type = types.attrsOf (types.submodule ({
+        options = {
+          desc = mkOption {
+            type = types.nullOr types.str;
+            default = null;
+            description = ''
+              Repository description.
+            '';
+          };
+          section = mkOption {
+            type = types.nullOr types.str;
+            default = null;
+            description = ''
+              Repository section.
+            '';
+          };
+          name = mkOption {
+            type = types.str;
+            description = ''
+              Repository name.
+            '';
+          };
+          hooks = mkOption {
+            type = types.attrsOf types.str;
+            default = {};
+            description = ''
+              Repository-specific hooks.
+            '';
+          };
+          public = mkOption {
+            type = types.bool;
+            default = false;
+            description = ''
+              Allow everybody to read the repository via HTTP if cgit enabled.
+            '';
+            # TODO allow every configured user to fetch the repository via SSH.
+          };
+        };
+      }));
+
+      default = {};
+
+      example = literalExample ''
+        {
+          testing = {
+            name = "testing";
+            hooks.post-update = '''
+              #! /bin/sh
+              set -euf
+              echo post-update hook: $* >&2
+            ''';
+          };
+          testing2 = { name = "testing2"; };
+        }
+      '';
+
+      description = ''
+        Repositories.
+      '';
+    };
+    root-desc = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = ''
+        Text printed below the heading on the repository index page.
+        Default value: "a fast webinterface for the git dscm".
+      '';
+    };
+    root-title = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = ''
+        Text printed as heading on the repository index page.
+        Default value: "Git Repository Browser".
+      '';
+    };
+    rules = mkOption {
+      type = types.unspecified;
+    };
+  };
+
+  git-imp = {
+    system.activationScripts.git-init = "${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 git-ssh-command)
+          config.krebs.users;
+      uid = 129318403; # genid git
+    };
+  };
+
+  cgit-imp = {
+    users.extraUsers = lib.singleton {
+      inherit (fcgitwrap-user) group name uid;
+      home = toString (pkgs.runCommand "empty" {} "mkdir -p $out");
+    };
+
+    users.extraGroups = lib.singleton {
+      inherit (fcgitwrap-group) gid name;
+    };
+
+    services.fcgiwrap = {
+      enable = true;
+      user = fcgitwrap-user.name;
+      group = fcgitwrap-user.group;
+      # socketAddress = "/run/fcgiwrap.sock" (default)
+      # socketType = "unix" (default)
+    };
+
+    environment.etc."cgitrc".text = ''
+      css=/static/cgit.css
+      logo=/static/cgit.png
+
+      # if you do not want that webcrawler (like google) index your site
+      robots=noindex, nofollow
+
+      virtual-root=/
+
+      # TODO make this nicer (and/or somewhere else)
+      cache-root=/tmp/cgit
+
+      cache-size=1000
+      enable-commit-graph=1
+      enable-index-links=1
+      enable-index-owner=0
+      enable-log-filecount=1
+      enable-log-linecount=1
+      enable-remote-branches=1
+
+      ${optionalString (cfg.root-title != null) "root-title=${cfg.root-title}"}
+      ${optionalString (cfg.root-desc != null) "root-desc=${cfg.root-desc}"}
+
+      snapshots=0
+      max-stats=year
+
+      ${concatMapStringsSep "\n" (repo: ''
+        repo.url=${repo.name}
+        repo.path=${cfg.dataDir}/${repo.name}
+        ${optionalString (repo.section != null) "repo.section=${repo.section}"}
+        ${optionalString (repo.desc != null) "repo.desc=${repo.desc}"}
+      '') (filter isPublicRepo (attrValues cfg.repos))}
+    '';
+
+    system.activationScripts.cgit = ''
+      mkdir -m 0700 -p /tmp/cgit
+      chown ${toString fcgitwrap-user.uid}:${toString fcgitwrap-group.gid} /tmp/cgit
+    '';
+
+    krebs.nginx = {
+      enable = true;
+      servers.cgit = {
+        server-names = [
+          "cgit.${config.networking.hostName}"
+          "cgit.${config.networking.hostName}.retiolum"
+        ];
+        locations = [
+          (nameValuePair "/" ''
+            include             ${pkgs.nginx}/conf/fastcgi_params;
+            fastcgi_param       SCRIPT_FILENAME ${pkgs.cgit}/cgit/cgit.cgi;
+            fastcgi_param       PATH_INFO       $uri;
+            fastcgi_param       QUERY_STRING    $args;
+            fastcgi_param       HTTP_HOST       $server_name;
+            fastcgi_pass        unix:${config.services.fcgiwrap.socketAddress};
+          '')
+          (nameValuePair "/static/" ''
+            root ${pkgs.cgit}/cgit;
+            rewrite ^/static(/.*)$ $1 break;
+          '')
+        ];
+      };
+    };
+  };
+
+  fcgitwrap-user = {
+    name = "fcgiwrap";
+    uid = 2867890860; # genid fcgiwrap
+    group = "fcgiwrap";
+  };
+
+  fcgitwrap-group = {
+    name = fcgitwrap-user.name;
+    gid = fcgitwrap-user.uid;
+  };
+
+
+  ensureList = x:
+    if typeOf x == "list" then x else [x];
+
+  getName = x: x.name;
+
+  isPublicRepo = getAttr "public"; # TODO this is also in ./cgit.nix
+
+  makeAuthorizedKey = git-ssh-command: user@{ name, pubkey, ... }:
+    # TODO assert name
+    # TODO assert pubkey
+    let
+      options = concatStringsSep "," [
+        ''command="exec ${git-ssh-command} ${name}"''
+        "no-agent-forwarding"
+        "no-port-forwarding"
+        "no-pty"
+        "no-X11-forwarding"
+      ];
+    in
+    "${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
+      ${concatStringsSep "\n" (map (go 1) patterns)}
+      exit -1
+    '';
+
+  reponames = rules: sort lessThan (unique (map (x: x.repo.name) rules));
+
+  # TODO makeGitHooks that uses runCommand instead of scriptFarm?
+  scriptFarm =
+    farm-name: scripts:
+    let
+      makeScript = script-name: script-string: {
+        name = script-name;
+        path = pkgs.writeScript "${farm-name}_${script-name}" script-string;
+      };
+    in
+    pkgs.linkFarm farm-name (mapAttrsToList makeScript scripts);
+
+
+  git-ssh-command = pkgs.writeScript "git-ssh-command" ''
+    #! /bin/sh
+    set -euf
+
+    PATH=${makeSearchPath "bin" (with pkgs; [
+      coreutils
+      git
+      gnugrep
+      gnused
+      systemd
+    ])}
+
+    abort() {
+      echo "error: $1" >&2
+      systemd-cat -p err -t git echo "error: $1"
+      exit -1
+    }
+
+    GIT_SSH_USER=$1
+
+    systemd-cat -p info -t git echo \
+      "authorizing $GIT_SSH_USER $SSH_CONNECTION $SSH_ORIGINAL_COMMAND"
+
+    # References: The Base Definitions volume of
+    # POSIX.1‐2013, Section 3.278, Portable Filename Character Set
+    portable_filename_bre="^[A-Za-z0-9._-]\\+$"
+
+    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 \
+      echo "authorized exec $command $repodir"
+
+    export GIT_SSH_USER
+    export GIT_SSH_REPO
+    exec "$command" "$repodir"
+  '';
+
+  init-script = pkgs.writeScript "git-init" ''
+    #! /bin/sh
+    set -euf
+
+    PATH=${makeSearchPath "bin" (with pkgs; [
+      coreutils
+      findutils
+      gawk
+      git
+      gnugrep
+      gnused
+    ])}
+
+    dataDir=${escapeShellArg cfg.dataDir}
+    mkdir -p "$dataDir"
+
+    # Notice how the presence of hooks symlinks determine whether
+    # we manage a repositry or not.
+
+    # Make sure that no existing repository has hooks.  We can delete
+    # symlinks because we assume we created them.
+    find "$dataDir" -mindepth 2 -maxdepth 2 -name hooks -type l -delete
+    bad_hooks=$(find "$dataDir" -mindepth 2 -maxdepth 2 -name hooks)
+    if echo "$bad_hooks" | grep -q .; then
+      printf 'error: unknown hooks:\n%s\n' \
+        "$(echo "$bad_hooks" | sed 's/^/  /')" \
+        >&2
+      exit -1
+    fi
+
+    # Initialize repositories.
+    ${concatMapStringsSep "\n" (repo:
+      let
+        hooks = scriptFarm "git-hooks" (makeHooks repo);
+      in
+      ''
+        reponame=${escapeShellArg repo.name}
+        repodir=$dataDir/$reponame
+        mode=${toString (if isPublicRepo repo then 0711 else 0700)}
+        if ! test -d "$repodir"; then
+          mkdir -m "$mode" "$repodir"
+          git init --bare --template=/var/empty "$repodir"
+          chown -R git:nogroup "$repodir"
+        fi
+        ln -s ${hooks} "$repodir/hooks"
+      ''
+    ) (attrValues cfg.repos)}
+
+    # Warn about repositories that exist but aren't mentioned in the
+    # current configuration (and thus didn't receive a hooks symlink).
+    unknown_repos=$(find "$dataDir" -mindepth 1 -maxdepth 1 \
+      -type d \! -exec test -e '{}/hooks' \; -print)
+    if echo "$unknown_repos" | grep -q .; then
+      printf 'warning: stale repositories:\n%s\n' \
+        "$(echo "$unknown_repos" | sed 's/^/  /')" \
+        >&2
+    fi
+  '';
+
+  makeHooks = repo: removeAttrs repo.hooks [ "pre-receive" ] // {
+    pre-receive = ''
+      #! /bin/sh
+      set -euf
+
+      PATH=${makeSearchPath "bin" (with pkgs; [
+        coreutils # env
+        git
+        systemd
+      ])}
+
+      accept() {
+        #systemd-cat -p info -t git echo "authorized $1"
+        accept_string="''${accept_string+$accept_string
+      }authorized $1"
+      }
+      reject() {
+        #systemd-cat -p err -t git 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 echo "$reject_string"
+        exit -1
+      fi
+
+      systemd-cat -p info -t git echo "$accept_string"
+
+      ${optionalString (hasAttr "post-receive" repo.hooks) ''
+        # custom post-receive hook
+        ${repo.hooks.post-receive}''}
+    '';
+  };
+
+  etc-base =
+    assert (hasPrefix "/etc/" cfg.etcDir);
+    removePrefix "/etc/" cfg.etcDir;
+
+in
+out
diff --git a/krebs/3modules/github-hosts-sync.nix b/krebs/3modules/github-hosts-sync.nix
new file mode 100644
index 000000000..0274b9d15
--- /dev/null
+++ b/krebs/3modules/github-hosts-sync.nix
@@ -0,0 +1,83 @@
+{ config, lib, pkgs, ... }:
+
+with builtins;
+with lib;
+let
+  cfg = config.krebs.github-hosts-sync;
+
+  out = {
+    options.krebs.github-hosts-sync = api;
+    config = mkIf cfg.enable imp;
+  };
+
+  api = {
+    enable = mkEnableOption "krebs.github-hosts-sync";
+    port = mkOption {
+      type = types.int; # TODO port type
+      default = 1028;
+    };