feat(cresettings): add RemoteExecutableWorkflowDONBindingEnabled gate

Global bool (default false) that, when enabled, lets the remote executable
capability server reject requests whose RequestMetadata.WorkflowDonID does not
match the authenticated calling DON.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: prashantkumar1982

pkg/settings/cresettings/README.md

@@ -52,6 +52,10 @@ flowchart
         VaultSignedResponseRequestIDEnabled[/VaultSignedResponseRequestIDEnabled\]:::gate
     end
 
+    subgraph executableServer[remote executable capability server.OnMessage]
+        RemoteExecutableWorkflowDONBindingEnabled[/RemoteExecutableWorkflowDONBindingEnabled\]:::gate
+    end
+
     subgraph HandleNodeMessage[gatewayHandler.HandleNodeMessage]
 %%      DON nodes → gateway (separate from the inbound trigger flow)
         GatewayHTTPGlobalRate[\GatewayHTTPGlobalRate/]:::rate

pkg/settings/cresettings/defaults.json

@@ -5,6 +5,7 @@
 	"GatewayVaultManagementEnabled": "true",
 	"VaultJWTAuthEnabled": "false",
 	"CentralizedWorkflowOwnerVerificationEnabled": "false",
+	"RemoteExecutableWorkflowDONBindingEnabled": "false",
 	"TenantID": "0",
 	"VaultOrgIdAsSecretOwnerEnabled": "false",
 	"PropagateOrgIDInRequestMetadata": "false",

pkg/settings/cresettings/defaults.toml

@@ -4,6 +4,7 @@ GatewayIncomingPayloadSizeLimit = '1mb'
 GatewayVaultManagementEnabled = 'true'
 VaultJWTAuthEnabled = 'false'
 CentralizedWorkflowOwnerVerificationEnabled = 'false'
+RemoteExecutableWorkflowDONBindingEnabled = 'false'
 TenantID = '0'
 VaultOrgIdAsSecretOwnerEnabled = 'false'
 PropagateOrgIDInRequestMetadata = 'false'

pkg/settings/cresettings/settings.go

@@ -58,6 +58,7 @@ var Default = Schema{
 	GatewayVaultManagementEnabled:               Bool(true),
 	VaultJWTAuthEnabled:                         Bool(false),
 	CentralizedWorkflowOwnerVerificationEnabled: Bool(false),
+	RemoteExecutableWorkflowDONBindingEnabled:   Bool(false),
 	TenantID: Uint64(0),
 	// Deprecated: retained for backwards compatibility; workflow owner identifies secret ownership.
 	VaultOrgIdAsSecretOwnerEnabled:                    Bool(false),
@@ -318,6 +319,12 @@ type Schema struct {
 	GatewayVaultManagementEnabled                     Setting[bool]
 	VaultJWTAuthEnabled                               Setting[bool]
 	CentralizedWorkflowOwnerVerificationEnabled       Setting[bool]
+	// RemoteExecutableWorkflowDONBindingEnabled, when true, makes the remote
+	// executable capability server reject any request whose
+	// RequestMetadata.WorkflowDonID does not match the authenticated calling DON
+	// (msg.CallerDonId). Binds caller-supplied WorkflowDonID to the authenticated
+	// sender DON so it cannot be spoofed by a colluding calling DON.
+	RemoteExecutableWorkflowDONBindingEnabled Setting[bool]
 	TenantID                                          Setting[uint64]
 	VaultOrgIdAsSecretOwnerEnabled                    Setting[bool] // Deprecated
 	PropagateOrgIDInRequestMetadata                   Setting[bool]