Support private flakes on FlakeHub (#38)

Use the GitHub Actions-issued JWT to authenticate with FlakeHub.
The repository will be granted its due permissions on FlakeHub,
and be able to pull the user's private flakes.

README.md

@@ -15,13 +15,38 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v4
+        uses: DeterminateSystems/nix-installer-action@main
       - name: Run `nix build`
         run: nix build .
 ```
 
 See [`.github/workflows/ci.yml`](.github/workflows/ci.yml) for a full example.
 
+To use private flakes from FlakeHub, use a configuration like this:
+
+```yaml
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  lints:
+    name: Build
+    runs-on: ubuntu-22.04
+    permissions:
+      id-token: "write"
+      contents: "read"
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@main
+        with:
+          flakehub: true
+      - name: Run `nix build`
+        run: nix build .
+```
+
 ## Configuration
 
 | Parameter                | Description                                                                                                                                                                                           | Type                                       | Default                                              |
@@ -29,6 +54,7 @@ See [`.github/workflows/ci.yml`](.github/workflows/ci.yml) for a full example.
 | `backtrace`              | The setting for [`RUST_BACKTRACE`][backtrace]                                                                                                                                                         | string                                     |                                                      |
 | `extra-args`             | Extra arguments to pass to the planner (prefer using structured `with:` arguments unless using a custom [planner]!)                                                                                   | string                                     |                                                      |
 | `extra-conf`             | Extra configuration lines for `/etc/nix/nix.conf` (includes `access-tokens` with `secrets.GITHUB_TOKEN` automatically if `github-token` is set)                                                       | string                                     |                                                      |
+| `flakehub`               | Log in to FlakeHub to pull private flakes using the GitHub Actions [JSON Web Token](https://jwt.io) (JWT), which is bound to the `api.flakehub.com` audience.                                         | Boolean                                    | `false`                                              |
 | `github-token`           | A [GitHub token] for making authenticated requests (which have a higher rate-limit quota than unauthenticated requests)                                                                               | string                                     | `${{ github.token }}`                                |
 | `init`                   | The init system to configure (requires `planner: linux-multi`)                                                                                                                                        | enum (`none` or `systemd`)                 |                                                      |
 | `local-root`             | A local `nix-installer` binary root. Overrides the `nix-installer-url` setting (a `nix-installer.sh` should exist, binaries should be named `nix-installer-$ARCH`, eg. `nix-installer-x86_64-linux`). | Boolean                                    | `false`                                              |

action.yml

@@ -13,6 +13,10 @@ inputs:
   extra-conf:
     description: Extra configuration lines for `/etc/nix/nix.conf` (includes `access-tokens` with `secrets.GITHUB_TOKEN` automatically if `github-token` is set)
     required: false
+  flakehub:
+    description: Automatically log in to your [FlakeHub](https://flakehub.com) account, for accessing private flakes.
+    required: false
+    default: false
   github-token:
     description: A GitHub token for making authenticated requests (which have a higher rate-limit quota than unauthenticated requests)
     default: ${{ github.token }}

dist/index.js

@@ -61,6 +61,7 @@ class NixInstallerAction {
         this.backtrace = action_input_string_or_null("backtrace");
         this.extra_args = action_input_string_or_null("extra-args");
         this.extra_conf = action_input_multiline_string_or_null("extra-conf");
+        this.flakehub = action_input_bool("flakehub");
         this.github_token = action_input_string_or_null("github-token");
         this.init = action_input_string_or_null("init");
         this.local_root = action_input_string_or_null("local-root");
@@ -87,6 +88,7 @@ class NixInstallerAction {
         this.nix_installer_url = resolve_nix_installer_url(this.platform, this.correlation);
     }
     executionEnvironment() {
+        return __awaiter(this, void 0, void 0, function* () {
             const execution_env = {};
             execution_env.NIX_INSTALLER_NO_CONFIRM = "true";
             execution_env.NIX_INSTALLER_DIAGNOSTIC_ATTRIBUTION = this.correlation;
@@ -186,6 +188,10 @@ class NixInstallerAction {
                 extra_conf += `trusted-users = root ${process.env.USER}`;
                 extra_conf += "\n";
             }
+            if (this.flakehub) {
+                extra_conf += `netrc-file = ${yield this.flakehub_login()}`;
+                extra_conf += "\n";
+            }
             if (this.extra_conf !== null && this.extra_conf.length !== 0) {
                 extra_conf += this.extra_conf.join("\n");
                 extra_conf += "\n";
@@ -196,10 +202,11 @@ class NixInstallerAction {
                 execution_env.NIX_INSTALLER_INIT = "none";
             }
             return execution_env;
+        });
     }
     execute_install(binary_path) {
         return __awaiter(this, void 0, void 0, function* () {
-            const execution_env = this.executionEnvironment();
+            const execution_env = yield this.executionEnvironment();
             actions_core.info(`Execution environment: ${JSON.stringify(execution_env, null, 4)}`);
             const args = ["install"];
             if (this.planner) {
@@ -276,6 +283,24 @@ class NixInstallerAction {
             }
         });
     }
+    flakehub_login() {
+        var _a;
+        return __awaiter(this, void 0, void 0, function* () {
+            const netrc_path = `${process.env["RUNNER_TEMP"]}/determinate-nix-installer-netrc`;
+            const jwt = yield actions_core.getIDToken("api.flakehub.com");
+            yield (0, promises_1.writeFile)(netrc_path, [
+                `machine api.flakehub.com login flakehub password ${jwt}`,
+                `machine flakehub.com login flakehub password ${jwt}`,
+            ].join("\n"));
+            actions_core.info("Logging in to FlakeHub.");
+            // the join followed by a match on ^... looks silly, but extra_config
+            // could contain multi-line values
+            if ((_a = this.extra_conf) === null || _a === void 0 ? void 0 : _a.join("\n").match(/^netrc-file/m)) {
+                actions_core.warning("Logging in to FlakeHub conflicts with the Nix option `netrc-file`.");
+            }
+            return netrc_path;
+        });
+    }
     execute_uninstall() {
         return __awaiter(this, void 0, void 0, function* () {
             const spawned = (0, node_child_process_1.spawn)(`/nix/nix-installer`, ["uninstall"], {

src/main.ts

@@ -1,6 +1,6 @@
 import * as actions_core from "@actions/core";
 import * as github from "@actions/github";
-import { mkdtemp, chmod, access } from "node:fs/promises";
+import { mkdtemp, chmod, access, writeFile } from "node:fs/promises";
 import { spawn } from "node:child_process";
 import { randomUUID } from "node:crypto";
 import { join } from "node:path";
@@ -17,6 +17,7 @@ class NixInstallerAction {
   backtrace: string | null;
   extra_args: string | null;
   extra_conf: string[] | null;
+  flakehub: boolean;
   github_token: string | null;
   // TODO: linux_init
   init: string | null;
@@ -54,6 +55,7 @@ class NixInstallerAction {
     this.backtrace = action_input_string_or_null("backtrace");
     this.extra_args = action_input_string_or_null("extra-args");
     this.extra_conf = action_input_multiline_string_or_null("extra-conf");
+    this.flakehub = action_input_bool("flakehub");
     this.github_token = action_input_string_or_null("github-token");
     this.init = action_input_string_or_null("init");
     this.local_root = action_input_string_or_null("local-root");
@@ -93,7 +95,7 @@ class NixInstallerAction {
     );
   }
 
-  private executionEnvironment(): ExecuteEnvironment {
+  private async executionEnvironment(): Promise<ExecuteEnvironment> {
     const execution_env: ExecuteEnvironment = {};
 
     execution_env.NIX_INSTALLER_NO_CONFIRM = "true";
@@ -217,6 +219,10 @@ class NixInstallerAction {
       extra_conf += `trusted-users = root ${process.env.USER}`;
       extra_conf += "\n";
     }
+    if (this.flakehub) {
+      extra_conf += `netrc-file = ${await this.flakehub_login()}`;
+      extra_conf += "\n";
+    }
     if (this.extra_conf !== null && this.extra_conf.length !== 0) {
       extra_conf += this.extra_conf.join("\n");
       extra_conf += "\n";
@@ -234,7 +240,7 @@ class NixInstallerAction {
   }
 
   private async execute_install(binary_path: string): Promise<number> {
-    const execution_env = this.executionEnvironment();
+    const execution_env = await this.executionEnvironment();
     actions_core.info(
       `Execution environment: ${JSON.stringify(execution_env, null, 4)}`,
     );
@@ -326,6 +332,32 @@ class NixInstallerAction {
     }
   }
 
+  async flakehub_login(): Promise<string> {
+    const netrc_path = `${process.env["RUNNER_TEMP"]}/determinate-nix-installer-netrc`;
+
+    const jwt = await actions_core.getIDToken("api.flakehub.com");
+
+    await writeFile(
+      netrc_path,
+      [
+        `machine api.flakehub.com login flakehub password ${jwt}`,
+        `machine flakehub.com login flakehub password ${jwt}`,
+      ].join("\n"),
+    );
+
+    actions_core.info("Logging in to FlakeHub.");
+
+    // the join followed by a match on ^... looks silly, but extra_config
+    // could contain multi-line values
+    if (this.extra_conf?.join("\n").match(/^netrc-file/m)) {
+      actions_core.warning(
+        "Logging in to FlakeHub conflicts with the Nix option `netrc-file`.",
+      );
+    }
+
+    return netrc_path;
+  }
+
   async execute_uninstall(): Promise<number> {
     const spawned = spawn(`/nix/nix-installer`, ["uninstall"], {
       env: {