X-Git-Url: http://git.scottworley.com/auto-upgrade-with-pinch/blobdiff_plain/d8537205b9696e3b76bc8cad98966e52f1ab626f..15d7ea954e9c4ca687f2175630724cf60346f758:/modules/auto-upgrade.nix

diff --git a/modules/auto-upgrade.nix b/modules/auto-upgrade.nix
index 1facaba..e41716b 100644
--- a/modules/auto-upgrade.nix
+++ b/modules/auto-upgrade.nix
@@ -1,6 +1,204 @@
+# auto-upgrade-with-pinch: Secure managed NixOS updates
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, version 3.
+
 { config, lib, pkgs, ... }:
 with lib;
-let cfg = config.system.autoUpgradeWithPinch;
+let
+  local-pkgs = import ../. { inherit pkgs; };
+  cfg = config.system.autoUpgradeWithPinch;
+  pull-repo-script = pkgs.writeShellScript "pull-repo" ''
+    set -eo pipefail
+
+    path=$1
+    config=$2
+
+    prop() {
+      ${pkgs.jq}/bin/jq -r ".$1" <<< "$config"
+    }
+
+    echo Pulling in "$path" >&2
+
+    if [[ ! -e "$path" ]];then
+      d=$(mktemp -d)
+      ${pkgs.git}/bin/git init "$d"
+      ${pkgs.git}/bin/git -C "$d" checkout -b "$(prop localBranch)"
+      ${pkgs.git}/bin/git -C "$d" remote add "$(prop remoteName)" "$(prop url)"
+      ${pkgs.git}/bin/git -C "$d" branch -u "$(prop remoteBranch)"
+      mkdir -p "$(${pkgs.coreutils}/bin/dirname "$path")"
+      mv "$d" "$path"
+    fi
+
+    cd "$path"
+
+    if [[ "$(${pkgs.git}/bin/git remote get-url "$(prop remoteName)")" != "$(prop url)" ]]; then
+      echo Expected git remote "$(prop remoteName)" to point at "$(prop url)" \
+        but it points at "$(${pkgs.git}/bin/git remote get-url "$(prop remoteName)")" >&2
+      case "$(prop onRemoteURLMismatch)" in
+        abort)  exit 1;;
+        update) echo Updating it >&2
+                ${pkgs.git}/bin/git -C "$d" remote set-url "$(prop remoteName)" "$(prop url)";;
+      esac
+    fi
+
+    ${pkgs.git}/bin/git fetch "$(prop remoteName)" "$(prop remoteBranch)"
+
+    if [[ "$(${pkgs.git}/bin/git rev-parse --abbrev-ref HEAD)" != "$(prop localBranch)" ]];then
+      echo Could not merge because currently-checked-out \
+           \""$(${pkgs.git}/bin/git rev-parse --abbrev-ref HEAD)"\" is not \
+           \""$(prop localBranch)"\"
+      case "$(prop onBranchMismatch)" in
+        abort) exit 1;;
+        continue) exit 0;;
+      esac
+    fi
+
+    if [[ "$(prop requireSignature)" == true ]]; then
+      ${pkgs.polite-merge}/bin/polite-merge \
+        -c gpg.program=${escapeShellArg (local-pkgs.keyed-gpg cfg.signingKeys)} \
+        merge --ff-only --verify-signatures
+    else
+      ${pkgs.polite-merge}/bin/polite-merge merge --ff-only
+    fi
+  '';
+
+  auto-upgrade-script = pkgs.writeShellScript "auto-upgrade" ''
+    ${pkgs.util-linux}/bin/flock /run/auto-upgrade-with-pinch ${
+      pkgs.writeShellScript "auto-upgrade-with-lock-held" ''
+        set -eo pipefail
+
+        dry_run=false
+        pinch_args=()
+        if [[ "$1" == --dry-run ]];then
+          dry_run=true
+          pinch_args=( --dry-run )
+        fi
+
+        hydrate() {
+          if "$dry_run";then
+            echo "Would run: $*"
+          else
+            "$@"
+          fi
+        }
+
+        die() {
+          echo "$*" >&2
+          exit 1
+        }
+
+        in_tmpdir() {
+          d=$(${pkgs.coreutils}/bin/mktemp -d)
+          pushd "$d"
+          "$@"
+          popd
+          ${pkgs.coreutils}/bin/rm -r "$d"
+        }
+
+        ${optionalString (cfg.upgradeConfigOwnershipPolicy != "any") (''
+          verify_ownership() {
+            if [[ "$1" != /* ]];then
+              die "Unexpected relative path: $1"
+            fi
+            if [[ "$1" != / ]];then
+              verify_ownership "$(${pkgs.coreutils}/bin/dirname "$1")"
+            fi
+            if [[ ! -e "$1" ]];then
+              die "Could not find upgrade config: $1 does not exist"
+            fi
+            if [[ -h "$1" ]];then
+              verify_ownership "$(
+                ${pkgs.coreutils}/bin/realpath --no-symlinks \
+                  "$(${pkgs.coreutils}/bin/dirname "$1")/$(${pkgs.coreutils}/bin/readlink "$1")"
+              )"
+            fi
+            perms="$(${pkgs.findutils}/bin/find "$1" -maxdepth 0 -printf "%M")"
+            if [[ "$perms" == d*t ]];then
+              die "Will not use upgrade config in sticky directory $1"
+            fi
+            owner=$(${pkgs.findutils}/bin/find "$1" -maxdepth 0 -printf "%u")
+            if [[ "$owner" != root ]];then
+              die "Will not use upgrade config not owned by root in $1"
+            fi
+            if [[ "$perms" == l* ]];then
+              return 0 # Root-owned symlinks are fine
+            fi
+            if [[ "$perms" == *w? ]];then
+              die "Will not use world-writable upgrade config in $1"
+            fi
+            ${
+              {
+                root = ''
+                  if [[ "$perms" == *w???? ]];then
+                    die "Will not use group-writable upgrade config in $1"
+                  fi
+                '';
+                wheel = ''
+                  if [[ "$perms" == *w???? ]];then
+                    group=$(${pkgs.findutils}/bin/find "$1" -maxdepth 0 -printf "%g")
+                    if [[ "$group" != wheel ]];then
+                      die "Will not use non-wheel-group group-writable upgrade config in $1"
+                    fi
+                  fi
+                '';
+              }."${cfg.upgradeConfigOwnershipPolicy}"
+            }
+          }
+        ''
+          + concatMapStringsSep "\n" (f: "verify_ownership ${escapeShellArg f}")
+          cfg.upgradeConfig)}
+
+        config=$(${pkgs.nix}/bin/nix-instantiate --eval --strict --json -A config \
+          --arg upgradeConfig ${
+            escapeShellArg ("["
+              + lib.concatMapStringsSep " " lib.strings.escapeNixString
+              cfg.upgradeConfig + "]")
+          } ${../upgrade-config.nix})
+
+        config_query() {
+          ${pkgs.jq}/bin/jq -r "$@" <<< "$config"
+        }
+
+        repo_query() {
+          config_query --arg path "$1" ".repos[\$ARGS.named.path]$2"
+        }
+
+        userenv_query() {
+          config_query --arg user "$1" ".userEnvironments[\$ARGS.named.user]$2"
+        }
+
+        # Pull updates
+        while read path;do
+          hydrate /run/wrappers/bin/sudo -u "$(repo_query "$path" .user)" \
+            ${pull-repo-script} "$path" "$(repo_query "$path" "")"
+        done < <( config_query '.repos | keys []' )
+
+        # Update channels
+        config_query '.pinchFiles[]' | ${pkgs.findutils}/bin/xargs --no-run-if-empty --delimiter=\\n ${pkgs.pinch}/bin/pinch update "''${pinch_args[@]}"
+
+        # Build
+        in_tmpdir hydrate ${config.system.build.nixos-rebuild}/bin/nixos-rebuild build
+        while read user;do
+          hydrate /run/wrappers/bin/sudo -u "$user" \
+            ${pkgs.nix}/bin/nix-build --no-out-link '<nixpkgs>' -A "$(userenv_query "$user" .package)"
+        done < <( config_query '.userEnvironments | keys []' )
+
+        # Install
+        hydrate ${config.system.build.nixos-rebuild}/bin/nixos-rebuild switch
+        while read user;do
+          remove_arg=-r
+          if [[ "$(userenv_query "$user" .otherPackagesAction)" == keep ]];then
+            remove_arg=
+          fi
+          hydrate /run/wrappers/bin/sudo -u "$user" \
+            ${pkgs.nix}/bin/nix-env -f '<nixpkgs>' $remove_arg -iA "$(userenv_query "$user" .package)"
+        done < <( config_query '.userEnvironments | keys []' )
+      ''
+    }
+  '';
+
 in {
   options = {
     system.autoUpgradeWithPinch = {
@@ -26,21 +224,69 @@ in {
         '';
       };
 
-      key = mkOption {
-        type = types.path;
+      signingKeys = mkOption {
+        type = types.listOf types.path;
+        description = ''
+          Files containing GPG keys that are authorized to sign updates.
+          Updates are only merged if the commit at the tip of the remote
+          ref is signed with one of these keys.
+        '';
+      };
+
+      upgradeConfig = mkOption {
+        type = types.listOf types.path;
+        description = ''
+          Configuration files that specify what git repo paths to pull, what
+          pinch files to update from, and what user environments to update.
+          These are specified in separate configuration files processed at
+          update time so that changes to this configuration take effect in
+          the same update cycle.
+        '';
+      };
+
+      upgradeConfigOwnershipPolicy = mkOption {
+        type = types.enum [ "root" "wheel" "any" ];
+        default = "root";
         description = ''
-          GPG key that signs updates.  Updates are only merged if the commit
-          at the tip of the remote branch is signed with this key.
+          Verify ownership of upgrade config files before using them for
+          system upgrades.
+
+          root = Config must be writable only by root.
+          wheel = Config must be writable only by root and wheel.
+          any = No checks.  Not recommended.
         '';
       };
     };
   };
 
   config = lib.mkIf cfg.enable {
+
+    security.sudo.extraRules = lib.mkAfter [{
+      groups = [ "users" ];
+      commands = [{
+        command = "${auto-upgrade-script}";
+        options = [ "NOPASSWD" "NOSETENV" ];
+      }];
+    }];
+    # NOSETENV above still allows through ~17 vars, including PATH.  Block those
+    # as well:
+    security.sudo.extraConfig = ''
+      Defaults!${auto-upgrade-script} !env_check
+      Defaults!${auto-upgrade-script} !env_keep
+    '';
+
     nixpkgs.overlays = [
-      (import ../overlays/keyedgit.nix)
       (import ../overlays/pinch.nix)
+      (import ../overlays/polite-merge.nix)
+      (self: super: {
+        auto-upgrade = super.writeShellScriptBin "auto-upgrade" ''
+          /run/wrappers/bin/sudo ${auto-upgrade-script}
+        '';
+      })
     ];
+
+    environment.systemPackages = [ pkgs.auto-upgrade ];
+
     systemd.services.nixos-upgrade = {
       description = "NixOS Upgrade";
       restartIfChanged = false;
@@ -58,19 +304,18 @@ in {
         gitMinimal
         gnutar
         gzip
-        pinch
         xz.bin
       ];
 
       script = ''
-        set -e
-        (
-          cd /etc/nixos
-          ${pkgs.keyedgit cfg.key}/bin/git pull --ff-only --verify-signatures
-          pinch update channels
-        )
-
-        ${config.system.build.nixos-rebuild}/bin/nixos-rebuild switch --no-build-output
+        set -eo pipefail
+
+        # Chill for awhile before applying updates.  If applying an update
+        # badly breaks things, we want a window in which an operator can
+        # intervene either to fix the problem or disable automatic updates.
+        sleep 2h
+
+        ${auto-upgrade-script}
       '';
 
       startAt = cfg.dates;