validate proposal (#1362)

The new validateProposal() method verifies:

1. The Fabric proposal structure (header, payload)
2. That the creator (BankA's FSC node X.509 certificate) is a known MSP member: mspManager.IsValid(creator)
3. That the proposal signature was made by that creator: verifier.Verify(proposalBytes, signature)

The fix closes a gap where the FSC endorser was not explicitly verifying that the Fabric proposal came from a legitimate, authenticated MSP member before endorsing it.



Signed-off-by: Hayim.Shaul@ibm.com <hayimsha@fhe3.haifa.ibm.com>

Author: HayimShaul

token/services/network/fabric/endorsement/fsc/deps.go

@@ -75,3 +75,22 @@ type NamespaceTxProcessor interface {
 	// EnableTxProcessing signals the backend to process all the transactions for the given tms id
 	EnableTxProcessing(tmsID token.TMSID) error
 }
+
+// MSPManager provides MSP-based identity validation and signature verification for a Fabric channel.
+// It is used to verify that the proposal creator is known to the network.
+//
+//go:generate counterfeiter -o mock/msp_manager.go -fake-name MSPManager . MSPManager
+type MSPManager interface {
+	// IsValid checks that the identity is valid (i.e., known to the network via MSP)
+	IsValid(identity view.Identity) error
+	// GetVerifier returns a verifier for the given identity, which can be used to verify signatures
+	GetVerifier(identity view.Identity) (driver.Verifier, error)
+}
+
+// ChannelProvider provides access to the MSP manager for a given Fabric network and channel.
+//
+//go:generate counterfeiter -o mock/channel_provider.go -fake-name ChannelProvider . ChannelProvider
+type ChannelProvider interface {
+	// GetMSPManager returns the MSP manager for the given network and channel
+	GetMSPManager(network, channel string) (MSPManager, error)
+}