[FAB-2643] MsgCryptoSvc: NPE when no policyMgr found

Scenario:
Peer gets an AliveMessage in gossip from an external organization,
and the messageCryptoService tries to validate it.
The validation first goes to the local MSP (and fails) so it tries
validating using one of the channel policies
(which were recently introduced), but it fails because
the channelPolicyManagerGetter returns a nil policyManager
from some reason.
This results in a null dereference panic and the unexpected and
sorrowful death of the peer.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x756ff5]

goroutine 45 [running]:
panic(0xc1ad00, 0xc420016050)
/opt/go/src/runtime/panic.go:500 +0x1a1
fabric/peer/gossip/mcs.(*mspMessageCryptoService).VerifyByChannel
/opt/gopath/src/github.com/hyperledger/fabric/peer/gossip/mcs/mcs.go:234
github.com/hyperledger/fabric/peer/gossip/mcs.(*mspMessageCryptoService).Verify
...
Full stacktrace available in the JIRA item.

I added a nil check in 2 places and also added tests that check these
corner cases.

Change-Id: I3f45aff6cbf483258fcb4166f059e03647b947c8
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

peer/gossip/mcs/mcs.go

@@ -17,11 +17,10 @@ limitations under the License.
 package mcs
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 
-	"bytes"
-
 	"github.com/hyperledger/fabric/bccsp"
 	"github.com/hyperledger/fabric/bccsp/factory"
 	"github.com/hyperledger/fabric/common/crypto"
@@ -156,6 +155,9 @@ func (s *mspMessageCryptoService) VerifyBlock(chainID common.ChainID, signedBloc
 
 	// Get the policy manager for channelID
 	cpm, ok := s.channelPolicyManagerGetter.Manager(channelID)
+	if cpm == nil {
+		return fmt.Errorf("Could not acquire policy manager for channel %s", channelID)
+	}
 	// ok is true if it was the manager requested, or false if it is the default manager
 	logger.Debugf("Got policy manager for channel [%s] with flag [%s]", channelID, ok)
 
@@ -228,6 +230,9 @@ func (s *mspMessageCryptoService) VerifyByChannel(chainID common.ChainID, peerId
 
 	// Get the policy manager for channel chainID
 	cpm, flag := s.channelPolicyManagerGetter.Manager(string(chainID))
+	if cpm == nil {
+		return fmt.Errorf("Could not acquire policy manager for channel %s", string(chainID))
+	}
 	logger.Debugf("Got policy manager for channel [%s] with flag [%s]", string(chainID), flag)
 
 	// Get channel reader policy

peer/gossip/mcs/mcs_test.go

@@ -17,16 +17,15 @@ limitations under the License.
 package mcs
 
 import (
+	"fmt"
 	"testing"
 
+	"github.com/golang/protobuf/proto"
 	"github.com/hyperledger/fabric/bccsp"
 	"github.com/hyperledger/fabric/bccsp/factory"
-
-	mockscrypto "github.com/hyperledger/fabric/common/mocks/crypto"
-
-	"github.com/golang/protobuf/proto"
 	"github.com/hyperledger/fabric/common/crypto"
 	"github.com/hyperledger/fabric/common/localmsp"
+	mockscrypto "github.com/hyperledger/fabric/common/mocks/crypto"
 	"github.com/hyperledger/fabric/common/policies"
 	"github.com/hyperledger/fabric/common/util"
 	"github.com/hyperledger/fabric/gossip/api"
@@ -79,6 +78,7 @@ func TestVerify(t *testing.T) {
 			map[string]policies.Manager{
 				"A": &mockChannelPolicyManager{&mockPolicy{&mockIdentityDeserializer{[]byte("Bob"), []byte("msg2")}}},
 				"B": &mockChannelPolicyManager{&mockPolicy{&mockIdentityDeserializer{[]byte("Charlie"), []byte("msg3")}}},
+				"C": nil,
 			},
 		},
 		&mockscrypto.LocalSigner{Identity: []byte("Alice")},
@@ -87,6 +87,7 @@ func TestVerify(t *testing.T) {
 			channelDeserializers: map[string]msp.IdentityDeserializer{
 				"A": &mockIdentityDeserializer{[]byte("Bob"), []byte("msg2")},
 				"B": &mockIdentityDeserializer{[]byte("Charlie"), []byte("msg3")},
+				"C": &mockIdentityDeserializer{[]byte("Yacov"), []byte("msg4")},
 			},
 		},
 	)
@@ -103,6 +104,12 @@ func TestVerify(t *testing.T) {
 
 	err = msgCryptoService.Verify(api.PeerIdentityType("Charlie"), sigma, msg)
 	assert.Error(t, err, "Charlie should not verify the signature")
+
+	sigma, err = msgCryptoService.Sign(msg)
+	assert.NoError(t, err)
+	err = msgCryptoService.Verify(api.PeerIdentityType("Yacov"), sigma, msg)
+	assert.Error(t, err)
+	assert.Contains(t, fmt.Sprintf("%v", err), "Could not acquire policy manager")
 }
 
 func TestVerifyBlock(t *testing.T) {
@@ -112,6 +119,7 @@ func TestVerifyBlock(t *testing.T) {
 			"A": &mockChannelPolicyManager{&mockPolicy{&mockIdentityDeserializer{[]byte("Bob"), []byte("msg2")}}},
 			"B": &mockChannelPolicyManager{&mockPolicy{&mockIdentityDeserializer{[]byte("Charlie"), []byte("msg3")}}},
 			"C": &mockChannelPolicyManager{&mockPolicy{&mockIdentityDeserializer{[]byte("Alice"), []byte("msg1")}}},
+			"D": &mockChannelPolicyManager{&mockPolicy{&mockIdentityDeserializer{[]byte("Alice"), []byte("msg1")}}},
 		},
 	}
 
@@ -130,9 +138,15 @@ func TestVerifyBlock(t *testing.T) {
 	// - Prepare testing valid block, Alice signs it.
 	blockRaw, msg := mockBlock(t, "C", aliceSigner, nil)
 	policyManagerGetter.managers["C"].(*mockChannelPolicyManager).mockPolicy.(*mockPolicy).deserializer.(*mockIdentityDeserializer).msg = msg
+	blockRaw2, msg2 := mockBlock(t, "D", aliceSigner, nil)
+	policyManagerGetter.managers["D"].(*mockChannelPolicyManager).mockPolicy.(*mockPolicy).deserializer.(*mockIdentityDeserializer).msg = msg2
 
 	// - Verify block
 	assert.NoError(t, msgCryptoService.VerifyBlock([]byte("C"), blockRaw))
+	delete(policyManagerGetter.managers, "D")
+	nilPolMgrErr := msgCryptoService.VerifyBlock([]byte("D"), blockRaw2)
+	assert.Contains(t, fmt.Sprintf("%v", nilPolMgrErr), "Could not acquire policy manager")
+	assert.Error(t, nilPolMgrErr)
 	assert.Error(t, msgCryptoService.VerifyBlock([]byte("A"), blockRaw))
 	assert.Error(t, msgCryptoService.VerifyBlock([]byte("B"), blockRaw))