From b557a93f83e92760b2c763423e2e9be51c1f18ef Mon Sep 17 00:00:00 2001
From: Tommy Murphy <tommymurphy@google.com>
Date: Thu, 1 Oct 2020 15:46:37 -0400
Subject: [PATCH] auth: support nodePublishSecretRef

---
 config/config.go      | 12 ++++++++++-
 config/config_test.go | 46 +++++++++++++++++++++++++++++++++++++++++++
 server/server.go      | 17 ++++++++++------
 3 files changed, 68 insertions(+), 7 deletions(-)

diff --git a/config/config.go b/config/config.go
index 96474fc4..2794524c 100644
--- a/config/config.go
+++ b/config/config.go
@@ -17,12 +17,15 @@
 package config
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"log"
 	"os"
 
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
 	"gopkg.in/yaml.v2"
 	"k8s.io/apimachinery/pkg/types"
 )
@@ -52,6 +55,7 @@ type MountConfig struct {
 	PodInfo     *PodInfo
 	TargetPath  string
 	Permissions os.FileMode
+	TokenSource oauth2.TokenSource
 }
 
 // MountParams hold unparsed arguments from the CSI Driver from the mount event.
@@ -85,10 +89,16 @@ func Parse(in *MountParams) (*MountConfig, error) {
 
 	// The secrets here are the relevant CSI driver (k8s) secrets. See
 	// https://kubernetes-csi.github.io/docs/secrets-and-credentials-storage-class.html
-	// Currently unused.
 	if err := json.Unmarshal([]byte(in.KubeSecrets), &secret); err != nil {
 		return nil, fmt.Errorf("failed to unmarshal secrets: %v", err)
 	}
+	if _, ok := secret["key.json"]; ok {
+		creds, err := google.CredentialsFromJSON(context.Background(), []byte(secret["key.json"]), "https://www.googleapis.com/auth/cloud-platform")
+		if err != nil {
+			return nil, fmt.Errorf("unable to generate credentials from key.json: %w", err)
+		}
+		out.TokenSource = creds.TokenSource
+	}
 
 	if os.Getenv("DEBUG") == "true" {
 		log.Printf("attributes: %v", attrib)
diff --git a/config/config_test.go b/config/config_test.go
index 860198b0..a001e5b2 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -160,3 +160,49 @@ func TestParseErrors(t *testing.T) {
 		})
 	}
 }
+
+func TestParseSecret(t *testing.T) {
+	in := &MountParams{
+		Attributes: `
+		{
+			"secrets": "- resourceName: \"projects/project/secrets/test/versions/latest\"\n  fileName: \"good1.txt\"\n",
+			"csi.storage.k8s.io/pod.namespace": "default",
+			"csi.storage.k8s.io/pod.name": "mypod",
+			"csi.storage.k8s.io/pod.uid": "123",
+			"csi.storage.k8s.io/serviceAccount.name": "mysa"
+		}
+		`,
+		KubeSecrets: `{"key.json":"{\"private_key_id\": \"123\",\"private_key\": \"a-secret\",\"token_uri\": \"https://example.com/token\",\"type\": \"service_account\"}"}`,
+		TargetPath:  "/tmp/foo",
+		Permissions: 777,
+	}
+
+	got, err := Parse(in)
+	if err != nil {
+		t.Errorf("Parse() failed: %v", err)
+	}
+	if got == nil || got.TokenSource == nil {
+		t.Errorf("TokenSource missing.")
+	}
+}
+
+func TestParseSecretError(t *testing.T) {
+	in := &MountParams{
+		Attributes: `
+		{
+			"secrets": "- resourceName: \"projects/project/secrets/test/versions/latest\"\n  fileName: \"good1.txt\"\n",
+			"csi.storage.k8s.io/pod.namespace": "default",
+			"csi.storage.k8s.io/pod.name": "mypod",
+			"csi.storage.k8s.io/pod.uid": "123",
+			"csi.storage.k8s.io/serviceAccount.name": "mysa"
+		}
+		`,
+		KubeSecrets: `{"key.json":"a"}`,
+		TargetPath:  "/tmp/foo",
+		Permissions: 777,
+	}
+
+	if _, err := Parse(in); err == nil {
+		t.Errorf("Parse() succeeded for malformed input, want error")
+	}
+}
diff --git a/server/server.go b/server/server.go
index 2030d734..5cdbc5c1 100644
--- a/server/server.go
+++ b/server/server.go
@@ -74,13 +74,18 @@ func (s *Server) Mount(ctx context.Context, req *v1alpha1.MountRequest) (*v1alph
 
 	smOpts := []option.ClientOption{option.WithUserAgent(s.UA)}
 
-	// Build the workload identity auth token if possible (fallback to node ID)
-	token, err := auth.Token(ctx, cfg, s.Kubeconfig)
-	if err != nil {
-		log.Printf("unable to use workload identity: %v", err)
-		return nil, status.Error(codes.PermissionDenied, fmt.Sprintf("Unable to obtain workload identity auth: %v", err))
+	if cfg.TokenSource == nil {
+		// Build the workload identity auth token
+		token, err := auth.Token(ctx, cfg, s.Kubeconfig)
+		if err != nil {
+			log.Printf("unable to use workload identity: %v", err)
+			return nil, status.Error(codes.PermissionDenied, fmt.Sprintf("Unable to obtain workload identity auth: %v", err))
+		} else {
+			smOpts = append(smOpts, option.WithTokenSource(oauth2.StaticTokenSource(token)))
+		}
 	} else {
-		smOpts = append(smOpts, option.WithTokenSource(oauth2.StaticTokenSource(token)))
+		// Use the secret provided in the CSI mount command for auth
+		smOpts = append(smOpts, option.WithTokenSource(cfg.TokenSource))
 	}
 
 	// Build the secret manager client