Validate environment variables in `Gitlab::Git::RevList`

The list of environment variables in `Gitlab::Git::RevList` need to be validate
to make sure that they don't reference any other project on disk.

This commit mixes in `ActiveModel::Validations` into `Gitlab::Git::RevList`, and
validates that the environment variables are on the level (using a custom
validator class). If the validations fail, the force push is still executed
without any environment variables set.

Add specs for the validation using shared examples.

2 files changed, 100 insertions, 0 deletions

diff --git a/spec/lib/gitlab/git/rev_list_spec.rb b/spec/lib/gitlab/git/rev_list_spec.rb
new file mode 100644
index 00000000000..cdfbff5658c
--- /dev/null
+++ b/spec/lib/gitlab/git/rev_list_spec.rb
@@ -0,0 +1,36 @@
+require 'spec_helper'
+require 'validators/git_environment_variables_validator_spec'
+
+describe Gitlab::Git::RevList, lib: true do
+  let(:project) { create(:project) }
+
+  context "validations" do
+    it_behaves_like(
+      "validated git environment variables",
+      ->(env, project) { Gitlab::Git::RevList.new('oldrev', 'newrev', project: project, env: env) }
+    )
+  end
+
+  context "#execute" do
+    let(:env) { { "GIT_OBJECT_DIRECTORY" => project.repository.path_to_repo } }
+    let(:rev_list) { Gitlab::Git::RevList.new('oldrev', 'newrev', project: project, env: env) }
+
+    it "calls out to `popen` without environment variables if the record is invalid" do
+      allow(rev_list).to receive(:valid?).and_return(false)
+      allow(Open3).to receive(:popen3)
+
+      rev_list.execute
+
+      expect(Open3).to have_received(:popen3).with(hash_excluding(env), any_args)
+    end
+
+    it "calls out to `popen` with environment variables if the record is valid" do
+      allow(rev_list).to receive(:valid?).and_return(true)
+      allow(Open3).to receive(:popen3)
+
+      rev_list.execute
+
+      expect(Open3).to have_received(:popen3).with(hash_including(env), any_args)
+    end
+  end
+end
diff --git a/spec/validators/git_environment_variables_validator_spec.rb b/spec/validators/git_environment_variables_validator_spec.rb
new file mode 100644
index 00000000000..81b028b6572
--- /dev/null
+++ b/spec/validators/git_environment_variables_validator_spec.rb
@@ -0,0 +1,64 @@
+require 'spec_helper'
+
+shared_examples_for "validated git environment variables" do |record_fn| 
+  subject { GitEnvironmentVariablesValidator.new(attributes: ['env']) }
+  let(:project) { create(:project) }
+
+  context "GIT_OBJECT_DIRECTORY" do
+    it "accepts values starting with the project repo path" do
+      env = { "GIT_OBJECT_DIRECTORY" => "#{project.repository.path_to_repo}/objects" }
+      record = record_fn[env, project]
+
+      subject.validate_each(record, 'env', env)
+
+      expect(record).to be_valid, "expected #{project.repository.path_to_repo}"
+    end
+
+    it "rejects values starting not with the project repo path" do
+      env = { "GIT_OBJECT_DIRECTORY" => "/some/other/path" }
+      record = record_fn[env, project]
+
+      subject.validate_each(record, 'env', env)
+
+      expect(record).to be_invalid
+    end
+
+    it "rejects values containing the project repo path but not starting with it" do
+      env = { "GIT_OBJECT_DIRECTORY" => "/some/other/path/#{project.repository.path_to_repo}" }
+      record = record_fn[env, project]
+
+      subject.validate_each(record, 'env', env)
+
+      expect(record).to be_invalid
+    end
+  end
+
+  context "GIT_ALTERNATE_OBJECT_DIRECTORIES" do
+    it "accepts values starting with the project repo path" do
+      env = { "GIT_ALTERNATE_OBJECT_DIRECTORIES" => project.repository.path_to_repo }
+      record = record_fn[env, project]
+
+      subject.validate_each(record, 'env', env)
+
+      expect(record).to be_valid, "expected #{project.repository.path_to_repo}"
+    end
+
+    it "rejects values starting not with the project repo path" do
+      env = { "GIT_ALTERNATE_OBJECT_DIRECTORIES" => "/some/other/path" }
+      record = record_fn[env, project]
+
+      subject.validate_each(record, 'env', env)
+
+      expect(record).to be_invalid
+    end
+
+    it "rejects values containing the project repo path but not starting with it" do
+      env = { "GIT_ALTERNATE_OBJECT_DIRECTORIES" => "/some/other/path/#{project.repository.path_to_repo}" }
+      record = record_fn[env, project]
+
+      subject.validate_each(record, 'env', env)
+
+      expect(record).to be_invalid
+    end
+  end
+end