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/secrets.nix

@@ -0,0 +1,6 @@
+let
+  keys = import ../keys;
+in
+{
+  "admin-environment.age".publicKeys = keys.rootKeys;
+}

.gitignore

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

.terraform.lock.hcl

@@ -0,0 +1,38 @@
+# This file is maintained automatically by "tofu init".
+# Manual edits may be lost in future updates.
+
+provider "registry.opentofu.org/numtide/secret" {
+  version     = "1.2.1"
+  constraints = "~> 1.2.1"
+  hashes = [
+    "h1:t2z3CjxVsXjKb3g59WGkLtvDIR4NzLU7UFEcyAgF2C0=",
+    "zh:17cbc7f3b90ee2b3ae5adfc3bd9cb70166a5ffbd8e642e64afa7cb0e32a34bae",
+    "zh:5d66ce2aea25fc3c12cec6fc569b8ff314df6d773b9c3449983a4e9cde8347c7",
+    "zh:67d02e96bf0d07f2fcf16ce9427a7a26f53e695676405d0c2b815808f950411d",
+    "zh:77c3c05681ce199e6b0e2e5a2dfe418f61ae8863d527e7a7d47a9699d912683b",
+    "zh:7f37e633b4f94ba9f347cfe68d44f80fe066188feb954b13ee0f621caae4121d",
+    "zh:ea16bbe494c6ddd0af7bbea9554474c387517db4e7f0d15513bb29ff893871bc",
+  ]
+}
+
+provider "registry.opentofu.org/raitobezarius/garage" {
+  version     = "1.0.3"
+  constraints = "~> 1.0.3"
+  hashes = [
+    "h1:QKbZcU7u9OG1t/h4S3+pXS3sOUfVMmfLTiYh5L5j1rE=",
+    "zh:04f220a2baf4bd1bae07888a1c311cacd6076c209de83adbe573525fc50f2ea4",
+    "zh:078938d5fa07e024d779c664823427af28935bbeb77e0ff940bac3e7bc41f1e8",
+    "zh:2dd58a2d82094a1b07ff1b6de57e4a0d96e1f20abecd4f70a6469079b46b76d9",
+    "zh:325da7a74b1c84f934b38134d7c419253292aeed6f6836a2fb37f42d13a8ff67",
+    "zh:3ca9230ef87e70691b24fd83d40bb5b6a08f0b91ab26cbb2e692f92155b6d179",
+    "zh:45ef683a18a5053c93c691d08f3903fd4918467dfa056b1c274207de8a6aeb74",
+    "zh:4c9ee6c34b07c209c5daf1e9ff182f828667e54a90a683bc11cdcea86e4f8ef7",
+    "zh:5f0bb6524b2fffa606e0e3585af93dfc31b611c7abf55e4371ae5fc36e85972c",
+    "zh:7a3495dc211164c7d4042769c20d7111c767d0fd5908742e0766281c70d7d184",
+    "zh:7ce79867cdd4b1f7028da811cd5cb271a46820c79c0328a1221dd3bb6215c631",
+    "zh:93278861ee6bcb64e23bd1268f79b02035fba4fca0a98607a98f46abf8dfdf83",
+    "zh:937e681beea8b0dd899557f2a194c8128bd8810417ff04954bc9958ff826e980",
+    "zh:cae6e1598dd32f23f3900c41e50a6ece7d9456dbd033d855bb238ac21539d67b",
+    "zh:f6f7556ba7d5578604290170a709e00140be6d7f8a510a20bce49a9a23d75e5f",
+  ]
+}

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;
+  };
+}