Add RunAsUserName functionality for the Windows Pod Sandbox Container

There was recent changes to cri to bring in a Windows section containing a
security context object to the pod config. Before this there was no way to specify
a user for the pod sandbox container to run as. In addition, the security context
is a field for field mirror of the Windows container version of it, so add the
ability to specify a GMSA credential spec for the pod sandbox container as well.

Signed-off-by: Daniel Canter <dcanter@microsoft.com>

pkg/cri/server/sandbox_run_windows.go

@@ -56,6 +56,25 @@ func (c *criService) sandboxContainerSpec(id string, config *runtime.PodSandboxC
 
 	specOpts = append(specOpts, customopts.WithWindowsDefaultSandboxShares)
 
+	// Start with the image config user and override below if RunAsUsername is not "".
+	username := imageConfig.User
+
+	runAsUser := config.GetWindows().GetSecurityContext().GetRunAsUsername()
+	if runAsUser != "" {
+		username = runAsUser
+	}
+
+	cs := config.GetWindows().GetSecurityContext().GetCredentialSpec()
+	if cs != "" {
+		specOpts = append(specOpts, customopts.WithWindowsCredentialSpec(cs))
+	}
+
+	// There really isn't a good Windows way to verify that the username is available in the
+	// image as early as here like there is for Linux. Later on in the stack hcsshim
+	// will handle the behavior of erroring out if the user isn't available in the image
+	// when trying to run the init process.
+	specOpts = append(specOpts, oci.WithUser(username))
+
 	for pKey, pValue := range getPassthroughAnnotations(config.Annotations,
 		runtimePodAnnotations) {
 		specOpts = append(specOpts, customopts.WithAnnotation(pKey, pValue))

pkg/cri/server/sandbox_run_windows_test.go

@@ -53,6 +53,7 @@ func getRunPodSandboxTestData() (*runtime.PodSandboxConfig, *imagespec.ImageConf
 		Entrypoint: []string{"/pause"},
 		Cmd:        []string{"forever"},
 		WorkingDir: "/workspace",
+		User:       "test-image-user",
 	}
 	specCheck := func(t *testing.T, id string, spec *runtimespec.Spec) {
 		assert.Equal(t, "test-hostname", spec.Hostname)
@@ -62,6 +63,13 @@ func getRunPodSandboxTestData() (*runtime.PodSandboxConfig, *imagespec.ImageConf
 		assert.Equal(t, "/workspace", spec.Process.Cwd)
 		assert.EqualValues(t, *spec.Windows.Resources.CPU.Shares, opts.DefaultSandboxCPUshares)
 
+		// Also checks if override of the image configs user is behaving.
+		t.Logf("Check username")
+		assert.Contains(t, spec.Process.User.Username, "test-user")
+
+		t.Logf("Check credential spec")
+		assert.Contains(t, spec.Windows.CredentialSpec, "{\"test\": \"spec\"}")
+
 		t.Logf("Check PodSandbox annotations")
 		assert.Contains(t, spec.Annotations, annotations.SandboxID)
 		assert.EqualValues(t, spec.Annotations[annotations.SandboxID], id)