Backport 1.7: Return an error when trying to store a too-large key with Raft (#13282)

changelog/13282.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+storage/raft: Fix a panic when trying to write a key > 32KB
+```

physical/raft/raft.go

@@ -1174,6 +1174,10 @@ func (b *RaftBackend) Get(ctx context.Context, path string) (*physical.Entry, er
 // or if the call to applyLog fails.
 func (b *RaftBackend) Put(ctx context.Context, entry *physical.Entry) error {
 	defer metrics.MeasureSince([]string{"raft-storage", "put"}, time.Now())
+	if len(entry.Key) > bolt.MaxKeySize {
+		return fmt.Errorf("%s, max key size for integrated storage is %d", physical.ErrKeyTooLarge, bolt.MaxKeySize)
+	}
+
 	command := &LogData{
 		Operations: []*LogOperation{
 			&LogOperation{

physical/raft/raft_test.go

@@ -15,6 +15,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/hashicorp/go-secure-stdlib/base62"
+
 	"github.com/go-test/deep"
 	"github.com/golang/protobuf/proto"
 	hclog "github.com/hashicorp/go-hclog"
@@ -225,6 +227,34 @@ func TestRaft_Backend(t *testing.T) {
 	physical.ExerciseBackend(t, b)
 }
 
+func TestRaft_Backend_LargeKey(t *testing.T) {
+	b, dir := getRaft(t, true, true)
+	defer os.RemoveAll(dir)
+
+	key, err := base62.Random(bolt.MaxKeySize + 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	entry := &physical.Entry{Key: key, Value: []byte(key)}
+
+	err = b.Put(context.Background(), entry)
+	if err == nil {
+		t.Fatal("expected error for put entry")
+	}
+
+	if !strings.Contains(err.Error(), physical.ErrKeyTooLarge) {
+		t.Fatalf("expected %q, got %v", physical.ErrKeyTooLarge, err)
+	}
+
+	out, err := b.Get(context.Background(), entry.Key)
+	if err != nil {
+		t.Fatalf("unexpected error after failed put: %v", err)
+	}
+	if out != nil {
+		t.Fatal("expected response entry to be nil after a failed put")
+	}
+}
+
 func TestRaft_Backend_LargeValue(t *testing.T) {
 	b, dir := getRaft(t, true, true)
 	defer os.RemoveAll(dir)

sdk/physical/physical.go

@@ -21,6 +21,7 @@ const (
 
 const (
 	ErrValueTooLarge = "put failed due to value being too large"
+	ErrKeyTooLarge   = "put failed due to key being too large"
 )
 
 // Backend is the interface required for a physical