attestation: improve error message when gh is too old

Library/Homebrew/attestation.rb

@@ -14,6 +14,9 @@ module Attestation
     # @api private
     HOMEBREW_CORE_REPO = "Homebrew/homebrew-core"
 
+    # @api private
+    GH_ATTESTATION_MIN_VERSION = T.let(Version.new("2.49.0").freeze, Version)
+
     # @api private
     BACKFILL_REPO = "trailofbits/homebrew-brew-verify"
 
@@ -59,10 +62,10 @@ def self.enabled?
     # @api private
     sig { returns(Pathname) }
     def self.gh_executable
-      # NOTE: We disable HOMEBREW_VERIFY_ATTESTATIONS when installing `gh` itself,
+      # NOTE: We set HOMEBREW_NO_VERIFY_ATTESTATIONS when installing `gh` itself,
       #       to prevent a cycle during bootstrapping. This can eventually be resolved
       #       by vendoring a pure-Ruby Sigstore verifier client.
-      @gh_executable ||= T.let(with_env("HOMEBREW_VERIFY_ATTESTATIONS" => nil) do
+      @gh_executable ||= T.let(with_env(HOMEBREW_NO_VERIFY_ATTESTATIONS: "1") do
         ensure_executable!("gh")
       end, T.nilable(Pathname))
     end
@@ -104,6 +107,13 @@ def self.check_attestation(bottle, signing_repo, signing_workflow = nil, subject
         # Even if we have credentials, they may be invalid or malformed.
         raise GhAuthNeeded, "invalid credentials" if e.status.exitstatus == 4
 
+        gh_version = Version.new(system_command!(gh_executable, args: ["--version"], print_stderr: false)
+                                 .stdout.match(/\d+(?:\.\d+)+/i).to_s)
+        if gh_version < GH_ATTESTATION_MIN_VERSION
+          raise e,
+                "#{gh_executable} is too old, you must upgrade it to continue"
+        end
+
         raise InvalidAttestationError, "attestation verification failed: #{e}"
       end
 

Library/Homebrew/test/attestation_spec.rb

@@ -4,7 +4,10 @@
 
 RSpec.describe Homebrew::Attestation do
   let(:fake_gh) { Pathname.new("/extremely/fake/gh") }
+  let(:fake_old_gh) { Pathname.new("/extremely/fake/old/gh") }
   let(:fake_gh_creds) { "fake-gh-api-token" }
+  let(:fake_gh_version) { instance_double(SystemCommand::Result, stdout: "2.49.0") }
+  let(:fake_old_gh_version) { instance_double(SystemCommand::Result, stdout: "2.48.0") }
   let(:fake_error_status) { instance_double(Process::Status, exitstatus: 1, termsig: nil) }
   let(:fake_auth_status) { instance_double(Process::Status, exitstatus: 4, termsig: nil) }
   let(:cached_download) { "/fake/cached/download" }
@@ -74,10 +77,42 @@
     end
   end
 
+  describe "::check_attestation fails with old gh" do
+    before do
+      allow(described_class).to receive(:gh_executable)
+        .and_return(fake_old_gh)
+
+      allow(described_class).to receive(:system_command!)
+        .with(fake_old_gh, args: ["--version"], print_stderr: false)
+        .and_return(fake_old_gh_version)
+    end
+
+    it "raises when gh is too old" do
+      expect(GitHub::API).to receive(:credentials)
+        .and_return(fake_gh_creds)
+
+      expect(described_class).to receive(:system_command!)
+        .with(fake_old_gh, args: ["attestation", "verify", cached_download, "--repo",
+                                  described_class::HOMEBREW_CORE_REPO, "--format", "json"],
+              env: { "GH_TOKEN" => fake_gh_creds }, secrets: [fake_gh_creds],
+              print_stderr: false)
+        .and_raise(ErrorDuringExecution.new(["foo"], status: fake_error_status))
+
+      expect do
+        described_class.check_attestation fake_bottle,
+                                          described_class::HOMEBREW_CORE_REPO
+      end.to raise_error(ErrorDuringExecution)
+    end
+  end
+
   describe "::check_attestation" do
     before do
       allow(described_class).to receive(:gh_executable)
         .and_return(fake_gh)
+
+      allow(described_class).to receive(:system_command!)
+        .with(fake_gh, args: ["--version"], print_stderr: false)
+        .and_return(fake_gh_version)
     end
 
     it "raises without any gh credentials" do