feat(infra): introduce Terranix

This requires the support for monorepo-terraform-state.s3.dgnum.eu being
available.

`.credentials/` is age-encrypted using only my key for now until we
figure out the right mechanism.

Signed-off-by: Ryan Lahfa <ryan@dgnum.eu>

.credentials/admin-environment.age

@@ -0,0 +1,5 @@
+age-encryption.org/v1
+-> ssh-ed25519 +qVung Rzqud7wBklrZ+T/50qx2Ly8d7OVb1za+pShg/4Wu3Hw
+CtSs7bGmE8gpt6pxm5FlP8Btr0hwx9F4UUB40bxSg24
+--- Ur0gMkDzmnrlX8rwx0b2uPA11KYnD28WhC3E2sQYUic
+®T£û£Ý¥ñlF›ÚìIRušˆâŠëP8±w
Z9<5A>ŠZ¿<>ù·ÿçúc^ (ÊßX°»Â&	¹#P<>­“áb_‰0†³[ÚHæŽI Ì´·áÞrcñS¬?0îx¾üÁqgqÞ,”ÙÂá1Fîj,V¹J#ܾe8!5[PüÐBÕFâ'Ðx«È‰!›¤x¹)ë9Nöy„
;×iØ9)pП~‡+”DÄ¡Pòõ~

.gitignore

@@ -9,3 +9,6 @@ result-*
 *.qcow2
 .gcroots
 .pre-commit-config.yaml
+
+# Ignore Terraform configuration file
+config.tf.json

default.nix

@@ -67,9 +67,18 @@ let
       commitizen.enable = true;
     };
   };
+
+  terranixConfig = import "${sources.terranix}/core" {
+    inherit pkgs;
+    strip_nulls = true;
+    terranix_config.imports = [ ./terranix ];
+  };
+  terranixConfigFile = (pkgs.formats.json { }).generate "config.tf.json" terranixConfig.config;
 in
 
 {
+  inherit terranixConfigFile terranixConfig;
+
   nodes = builtins.mapAttrs (
     host: { site, ... }: "${host}.${site}.infra.dgnum.eu"
   ) (import ./meta/nodes.nix);
@@ -83,11 +92,36 @@ in
       name = "dgnum-infra";
 
       packages = [
+        (pkgs.writeShellScriptBin "tf" ''
+          set -eo pipefail
+          ln -snf ${terranixConfigFile} config.tf.json
+          exec ${pkgs.lib.getExe pkgs.opentofu} "$@"
+        '')
+        (pkgs.writeShellScriptBin "decryptAndSourceEnvironment" ''
+          set -eo pipefail
+
+          # TODO: don't hardcode me.
+          SECRET_FILE=".credentials/admin-environment.age"
+          IDENTITIES=()
+          for identity in [ "$HOME/.ssh/id_ed25519" "$HOME/.ssh/id_rsa" ]; do
+            test -r "$identity" || continue
+            IDENTITIES+=(-i)
+            IDENTITIES+=("$identity")
+          done
+
+          test "''${#IDENTITIES[@]}" -eq 0 && echo "[agenix-shell] WARNING: no readable identities found!"
+
+          test -f "$SECRET_FILE" || echo "[agenix-shell] WARNING: encrypted environment file $SECRET_FILE not found!"
+          export eval $(${pkgs.lib.getExe pkgs.rage} --decrypt "''${IDENTITIES[@]}" -o - $SECRET_FILE)
+
+          echo "[agenix-shell] Repository-wide secrets loaded in the environment."
+        '')
         (pkgs.nixos-generators.overrideAttrs (_: {
           version = "1.8.0-unstable";
           src = builtins.storePath sources.nixos-generators;
         }))
         pkgs.npins
+        pkgs.rage
 
         (pkgs.callPackage ./lib/colmena { inherit (nix-pkgs) colmena; })
         (pkgs.callPackage "${sources.agenix}/pkgs/agenix.nix" { })
@@ -97,6 +131,8 @@ in
 
       shellHook = ''
         ${git-checks.shellHook}
+        # If we want to export these environments, we need to source it, not call it.
+        source $(which decryptAndSourceEnvironment)
       '';
 
       preferLocalBuild = true;

npins/sources.json

@@ -300,6 +300,21 @@
       "url": null,
       "hash": "11vvfxw2sznc155x0xlgl00g6n9sr90xa0b1hr14vchg7gkz46r5"
     },
+    "terranix": {
+      "type": "GitRelease",
+      "repository": {
+        "type": "GitHub",
+        "owner": "terranix",
+        "repo": "terranix"
+      },
+      "pre_releases": false,
+      "version_upper_bound": null,
+      "release_prefix": null,
+      "version": "2.7.0",
+      "revision": "00710f39f38a0a654a2c4fd96cbb988b4f4cedfa",
+      "url": "https://api.github.com/repos/terranix/terranix/tarball/2.7.0",
+      "hash": "1wsyhsdsjw6xlhpkhaqvia3x0na3nx2vamcb2rbcbdmb7ra1y9f6"
+    },
     "wp4nix": {
       "type": "Git",
       "repository": {

terranix/common.nix

@@ -0,0 +1,7 @@
+{
+  # Until we get some kind of KMS operational, store secrets in the state file.
+  terraform.required_providers.secret = {
+    version = "~> 1.2.1";
+    source = "numtide/secret";
+  };
+}

terranix/default.nix

@@ -0,0 +1,6 @@
+{
+  imports = [
+    ./common.nix
+    ./state.nix
+  ];
+}

terranix/state.nix

@@ -0,0 +1,21 @@
+{
+  # We use terraform.backend.s3 directly instead of the type-checked Terranix
+  # backend.s3 options. The latter does not support setting arbitrary s3
+  # endpoints.
+  #
+  # Note: currently requires the user to provide AWS_ACCESS_KEY_ID as well as
+  # AWS_SECRET_ACCESS_KEY in their environment variables.
+
+  terraform.backend.s3 = {
+    endpoints.s3 = "s3.dgnum.eu";
+    region = "garage";
+    bucket = "monorepo-terraform-state";
+    key = "state";
+
+    # It's just a dumb Garage server, don't try to be smart.
+    skip_credentials_validation = true;
+    skip_region_validation = true;
+    skip_requesting_account_id = true;
+    skip_metadata_api_check = true;
+  };
+}