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[FAB-2962] Gossip- Channel name obfuscation
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This commit changes the stateInfo messages in gossip in the following way:
Instead of sending the plaintext of the channel in the channel field
of the GossipMessage - it now sends instead: Hash(channel || PKI-ID).

The added security benefit:
Given a message M with a channel C,
a peer not in C needs to do an exhaustive search / dictionary attack
on channel names, in order to guess C.
Without knowing C, it cannot ask an ordering service, or some other peer
to get a block for that channel because sending the hash would be worthless.

On reception of a StateInfo message from a peer with PKI-ID P, a peer
iterates over all channels (denote CHAN as the current iteration)
it participates in, and computes Hash(P || CHAN) and this way it
knows the channel the message relates to.
- If it is not in the channel, it would simply forward the message
  to peers in the organization (as done today).
- Else, it forwards the message to peers that their organization is a member
  of the channel (as done today).

Change-Id: I419ed3e440b936de80ec5624698b5d6e52376e98
Signed-off-by: Yacov Manevich <[email protected]>
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@yacovm
yacovm committed Apr 14, 2017
1 parent c3009e6 commit 90573e8
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Showing 6 changed files with 334 additions and 146 deletions.
71 changes: 55 additions & 16 deletions gossip/gossip/channel/channel.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ import (
"sync/atomic"
"time"

common_utils "github.com/hyperledger/fabric/common/util"
"github.com/hyperledger/fabric/gossip/api"
"github.com/hyperledger/fabric/gossip/comm"
"github.com/hyperledger/fabric/gossip/common"
Expand Down Expand Up @@ -115,6 +116,7 @@ type gossipChannel struct {
sync.RWMutex
shouldGossipStateInfo int32
mcs api.MessageCryptoService
pkiID common.PKIidType
stopChan chan struct{}
stateInfoMsg *proto.SignedGossipMessage
orgs []api.OrgIdentityType
Expand Down Expand Up @@ -147,8 +149,9 @@ func (mf *membershipFilter) GetMembership() []discovery.NetworkMember {
}

// NewGossipChannel creates a new GossipChannel
func NewGossipChannel(mcs api.MessageCryptoService, chainID common.ChainID, adapter Adapter, joinMsg api.JoinChannelMessage) GossipChannel {
func NewGossipChannel(pkiID common.PKIidType, mcs api.MessageCryptoService, chainID common.ChainID, adapter Adapter, joinMsg api.JoinChannelMessage) GossipChannel {
gc := &gossipChannel{
pkiID: pkiID,
mcs: mcs,
Adapter: adapter,
logger: util.GetLogger(util.LoggingChannelModule, adapter.GetConf().ID),
Expand Down Expand Up @@ -359,7 +362,7 @@ func (gc *gossipChannel) HandleMessage(msg proto.ReceivedMessage) {
return
}
if !gc.IsOrgInChannel(orgID) {
gc.logger.Warning("Point to point message came from", msg.GetConnectionInfo().ID, "but it's not eligible for the channel", msg.GetGossipMessage().Channel)
gc.logger.Warning("Point to point message came from", msg.GetConnectionInfo().ID, "but it's not eligible for the channel", string(gc.chainID))
return
}

Expand Down Expand Up @@ -405,7 +408,7 @@ func (gc *gossipChannel) HandleMessage(msg proto.ReceivedMessage) {
}
if m.IsPullMsg() && m.GetPullMsgType() == proto.PullMsgType_BLOCK_MSG {
if !gc.EligibleForChannel(discovery.NetworkMember{PKIid: msg.GetConnectionInfo().ID}) {
gc.logger.Warning(msg.GetConnectionInfo().ID, "isn't eligible for channel", gc.chainID)
gc.logger.Warning(msg.GetConnectionInfo().ID, "isn't eligible for channel", string(gc.chainID))
return
}
if m.IsDataUpdate() {
Expand Down Expand Up @@ -437,35 +440,42 @@ func (gc *gossipChannel) HandleMessage(msg proto.ReceivedMessage) {
}

func (gc *gossipChannel) handleStateInfSnapshot(m *proto.GossipMessage, sender common.PKIidType) {
chanName := string(gc.chainID)
for _, envelope := range m.GetStateSnapshot().Elements {
stateInf, err := envelope.ToGossipMessage()
if err != nil {
gc.logger.Warning("StateInfo snapshot contains an invalid message:", err)
gc.logger.Warning("Channel", chanName, ": StateInfo snapshot contains an invalid message:", err)
return
}
if !stateInf.IsStateInfoMsg() {
gc.logger.Warning("Element of StateInfoSnapshot isn't a StateInfoMessage:", stateInf, "message sent from", sender)
gc.logger.Warning("Channel", chanName, ": Element of StateInfoSnapshot isn't a StateInfoMessage:",
stateInf, "message sent from", sender)
return
}

orgID := gc.GetOrgOfPeer(stateInf.GetStateInfo().PkiId)
si := stateInf.GetStateInfo()
orgID := gc.GetOrgOfPeer(si.PkiId)
if orgID == nil {
gc.logger.Warning("Couldn't find org identity of peer", stateInf.GetStateInfo().PkiId, "message sent from", sender)
gc.logger.Warning("Channel", chanName, ": Couldn't find org identity of peer",
si.PkiId, "message sent from", sender)
return
}

if !gc.IsOrgInChannel(orgID) {
gc.logger.Warning("Peer", stateInf.GetStateInfo().PkiId, "is not in an eligible org, can't process a stateInfo from it, sent from", sender)
gc.logger.Warning("Channel", chanName, ": Peer", stateInf.GetStateInfo().PkiId,
"is not in an eligible org, can't process a stateInfo from it, sent from", sender)
return
}

if !bytes.Equal(stateInf.Channel, []byte(gc.chainID)) {
gc.logger.Warning("StateInfo message is of an invalid channel", stateInf, "sent from", sender)
expectedMAC := ChannelMAC(si.PkiId, gc.chainID)
if !bytes.Equal(si.ChannelMAC, expectedMAC) {
gc.logger.Warning("Channel", chanName, ": StateInfo message", stateInf,
", has an invalid MAC. Expected", expectedMAC, ", got", si.ChannelMAC, ", sent from", sender)
return
}
err = gc.ValidateStateInfoMessage(stateInf)
if err != nil {
gc.logger.Warning("Failed validating state info message:", stateInf, ":", err, "sent from", sender)
gc.logger.Warning("Channel", chanName, ": Failed validating state info message:",
stateInf, ":", err, "sent from", sender)
return
}
gc.stateInfoMsgStore.Add(stateInf)
Expand Down Expand Up @@ -524,6 +534,26 @@ func (gc *gossipChannel) verifyMsg(msg proto.ReceivedMessage) bool {
return false
}

if m.IsStateInfoMsg() {
si := m.GetStateInfo()
expectedMAC := ChannelMAC(si.PkiId, gc.chainID)
if !bytes.Equal(expectedMAC, si.ChannelMAC) {
gc.logger.Warning("Message contains wrong channel MAC(", si.ChannelMAC, "), expected", expectedMAC)
return false
}
return true
}

if m.IsStateInfoPullRequestMsg() {
sipr := m.GetStateInfoPullReq()
expectedMAC := ChannelMAC(msg.GetConnectionInfo().ID, gc.chainID)
if !bytes.Equal(expectedMAC, sipr.ChannelMAC) {
gc.logger.Warning("Message contains wrong channel MAC(", sipr.ChannelMAC, "), expected", expectedMAC)
return false
}
return true
}

if !bytes.Equal(m.Channel, []byte(gc.chainID)) {
gc.logger.Warning("Message contains wrong channel(", m.Channel, "), expected", gc.chainID)
return false
Expand All @@ -533,11 +563,12 @@ func (gc *gossipChannel) verifyMsg(msg proto.ReceivedMessage) bool {

func (gc *gossipChannel) createStateInfoRequest() *proto.SignedGossipMessage {
return (&proto.GossipMessage{
Channel: gc.chainID,
Tag: proto.GossipMessage_CHAN_OR_ORG,
Nonce: 0,
Tag: proto.GossipMessage_CHAN_OR_ORG,
Nonce: 0,
Content: &proto.GossipMessage_StateInfoPullReq{
StateInfoPullReq: &proto.StateInfoPullRequest{},
StateInfoPullReq: &proto.StateInfoPullRequest{
ChannelMAC: ChannelMAC(gc.pkiID, gc.chainID),
},
},
}).NoopSign()
}
Expand Down Expand Up @@ -586,3 +617,11 @@ func (cache *stateInfoCache) Add(msg *proto.SignedGossipMessage) bool {
}
return added
}

// ChannelMAC returns a byte slice that is derived from the peer's PKI-ID
// and a channel name
func ChannelMAC(pkiID common.PKIidType, channelID common.ChainID) []byte {
// Hash is computed on (PKI-ID || channel ID)
preImage := append([]byte(pkiID), []byte(channelID)...)
return common_utils.ComputeSHA256(preImage)
}
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