bekkalokk/gitea: set up gitea-web sync units

hosts/bekkalokk/services/gitea/default.nix

@@ -6,7 +6,8 @@ let
 in {
   imports = [
     ./ci.nix
-    ./import-users.nix
+    ./import-users
+    ./web-secret-provider
   ];
 
   sops.secrets = {

hosts/bekkalokk/services/gitea/web-secret-provider/default.nix

@@ -0,0 +1,106 @@
+{ config, pkgs, lib, ... }:
+let
+  organizations = [
+    "Drift"
+    "Projects"
+    "Kurs"
+  ];
+
+  giteaCfg = config.services.gitea;
+
+  giteaWebSecretProviderScript = pkgs.writers.writePython3 "gitea-web-secret-provider" {
+    libraries = with pkgs.python3Packages; [ requests ];
+    flakeIgnore = [
+      "E501" # Line over 80 chars lol
+      "E201" # "whitespace after {"
+      "E202" # "whitespace after }"
+      "E251" # unexpected spaces around keyword / parameter equals
+      "W391" # Newline at end of file
+    ];
+    makeWrapperArgs = [
+      "--prefix PATH : ${(lib.makeBinPath [ pkgs.openssh ])}"
+    ];
+  } (builtins.readFile ./gitea-web-secret-provider.py);
+in
+{
+  users.groups."gitea-web" = { };
+  users.users."gitea-web" = {
+    group = "gitea-web";
+    isSystemUser = true;
+  };
+
+  sops.secrets."gitea/web-secret-provider/token" = {
+    owner = "gitea-web";
+    group = "gitea-web";
+    restartUnits = [
+      "gitea-web-secret-provider@"
+    ] ++ (map (org: "gitea-web-secret-provider@${org}") organizations);
+  };
+
+  systemd.slices.system-giteaweb = {
+    description = "Gitea web directories";
+  };
+
+  # https://www.freedesktop.org/software/systemd/man/latest/systemd.unit.html#Specifiers
+  # %i - instance name (after the @)
+  # %d - secrets directory
+  systemd.services."gitea-web-secret-provider@" = {
+    description = "Ensure all repos in %i has an SSH key to push web content";
+    requires = [ "gitea.service" "network.target" ];
+    serviceConfig = {
+      Slice = "system-giteaweb.slice";
+      Type = "oneshot";
+      ExecStart = let
+        args = lib.cli.toGNUCommandLineShell { } {
+          org = "%i";
+          token-path = "%d/token";
+          api-url = "${giteaCfg.settings.server.ROOT_URL}api/v1";
+          key-dir = "/var/lib/gitea-web/keys/%i";
+          authorized-keys-path = "/var/lib/gitea-web/authorized_keys.d/%i";
+          rrsync-script = pkgs.writeShellScript "rrsync-chown" ''
+            ${lib.getExe pkgs.rrsync} -wo "$1"
+            ${pkgs.coreutils}/bin/chown -R gitea-web:nginx "$1"
+          '';
+          web-dir = "/var/lib/gitea-web/web";
+        };
+      in "${giteaWebSecretProviderScript} ${args}";
+
+      User = "gitea-web";
+      Group = "gitea-web";
+
+      StateDirectory = "gitea-web";
+      StateDirectoryMode = "0750";
+      LoadCredential = [
+        "token:${config.sops.secrets."gitea/web-secret-provider/token".path}"
+      ];
+
+      NoNewPrivileges = true;
+      PrivateTmp = true;
+      PrivateDevices = true;
+      ProtectSystem = true;
+      ProtectHome = true;
+      ProtectControlGroups = true;
+      ProtectKernelModules = true;
+      ProtectKernelTunables = true;
+      RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+      RestrictRealtime = true;
+      RestrictSUIDSGID = true;
+      MemoryDenyWriteExecute = true;
+      LockPersonality = true;
+    };
+  };
+
+  systemd.timers."gitea-web-secret-provider@" = {
+    description = "Ensure all repos in %i has an SSH key to push web content";
+    timerConfig = {
+      RandomizedDelaySec = "1h";
+      Persistent = true;
+      Unit = "gitea-web-secret-provider@%i.service";
+      OnCalendar = "daily";
+    };
+  };
+
+  systemd.targets.timers.wants = map (org: "gitea-web-secret-provider@${org}.timer") organizations;
+
+  services.openssh.authorizedKeysFiles = map (org: "/var/lib/gitea-web/authorized_keys.d/${org}") organizations;
+}

hosts/bekkalokk/services/gitea/web-secret-provider/gitea-web-secret-provider.py

@@ -0,0 +1,112 @@
+import argparse
+import hashlib
+import os
+import requests
+import subprocess
+from pathlib import Path
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description="Generate SSH keys for Gitea repositories and add them as secrets")
+    parser.add_argument("--org", required=True, type=str, help="The organization to generate keys for")
+    parser.add_argument("--token-path", metavar='PATH', required=True, type=Path, help="Path to a file containing the Gitea API token")
+    parser.add_argument("--api-url", metavar='URL', type=str, help="The URL of the Gitea API", default="https://git.pvv.ntnu.no/api/v1")
+    parser.add_argument("--key-dir", metavar='PATH', type=Path, help="The directory to store the generated keys in", default="/run/gitea-web-secret-provider")
+    parser.add_argument("--authorized-keys-path", metavar='PATH', type=Path, help="The path to the resulting authorized_keys file", default="/etc/ssh/authorized_keys.d/gitea-web-secret-provider")
+    parser.add_argument("--rrsync-script", metavar='PATH', type=Path, help="The path to a rrsync script, taking the destination path as its single argument")
+    parser.add_argument("--web-dir", metavar='PATH', type=Path, help="The directory to sync the repositories to", default="/var/www")
+    parser.add_argument("--force", action="store_true", help="Overwrite existing keys")
+    return parser.parse_args()
+
+
+def add_secret(args: argparse.Namespace, token: str, repo: str, name: str, secret: str):
+    result = requests.put(
+        f"{args.api_url}/repos/{args.org}/{repo}/actions/secrets/{name}",
+        json = { 'data': secret },
+        headers = { 'Authorization': 'token ' + token },
+    )
+    if result.status_code not in (201, 204):
+        raise Exception(f"Failed to add secret: {result.json()}")
+
+
+def get_org_repo_list(args: argparse.Namespace, token: str):
+    result = requests.get(
+        f"{args.api_url}/orgs/{args.org}/repos",
+        headers = { 'Authorization': 'token ' + token },
+    )
+    return [repo["name"] for repo in result.json()]
+
+
+def generate_ssh_key(args: argparse.Namespace, repository: str):
+    keyname = hashlib.sha256(args.org.encode() + repository.encode()).hexdigest()
+    key_path = args.key_dir / keyname
+    if not key_path.is_file() or args.force:
+        subprocess.run(
+            [
+                "ssh-keygen",
+                *("-t", "ed25519"),
+                *("-f", key_path),
+                *("-N", ""),
+                *("-C", f"{args.org}/{repository}"),
+            ],
+            check=True,
+            stdin=subprocess.DEVNULL,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
+        print(f"Generated SSH key for `{args.org}/{repository}`")
+
+    with open(key_path, "r") as f:
+        private_key = f.read()
+
+    pub_key_path = args.key_dir / (keyname + '.pub')
+    with open(pub_key_path, "r") as f:
+        public_key = f.read()
+
+    return private_key, public_key
+
+
+SSH_OPTS = ",".join([
+    "restrict",
+    "no-agent-forwarding",
+    "no-port-forwarding",
+    "no-pty",
+    "no-X11-forwarding",
+])
+
+
+def generate_authorized_keys(args: argparse.Namespace, repo_public_keys: list[tuple[str, str]]):
+    lines = []
+    for repo, public_key in repo_public_keys:
+        command = f"{args.rrsync_script} {args.web_dir}/{args.org}/{repo}"
+        lines.append(f'command="{command}",{SSH_OPTS} {public_key}')
+
+    with open(args.authorized_keys_path, "w") as f:
+        f.writelines(lines)
+
+
+def main():
+    args = parse_args()
+
+    with open(args.token_path, "r") as f:
+        token = f.read().strip()
+
+    os.makedirs(args.key_dir, 0o700, exist_ok=True)
+    os.makedirs(args.authorized_keys_path.parent, 0o700, exist_ok=True)
+
+    repos = get_org_repo_list(args, token)
+    print(f'Found {len(repos)} repositories in `{args.org}`')
+
+    repo_public_keys = []
+    for repo in repos:
+        print(f"Locating key for `{args.org}/{repo}`")
+        private_key, public_key = generate_ssh_key(args, repo)
+        add_secret(args, token, repo, "WEB_SYNC_SSH_KEY", private_key)
+        repo_public_keys.append((repo, public_key))
+
+    generate_authorized_keys(args, repo_public_keys)
+    print(f"Wrote authorized_keys file to `{args.authorized_keys_path}`")
+
+
+if __name__ == "__main__":
+    main()