feat(agentcompat): add scoped IO stream capabilities

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

service/rpc/io_stream_capability_cancel_agentcompat.go

@@ -0,0 +1,99 @@
+//go:build agentcompat
+
+package rpc
+
+import (
+	"errors"
+	"io"
+)
+
+func (s *NezhaHandler) CancelAgentCompatIOStreamCapability(access AgentCompatCapabilityAccess) error {
+	s.ioStreamMutex.Lock()
+	registration, exists := s.agentCompatCapabilities.active[access.Capability.value]
+	if !exists {
+		s.ioStreamMutex.Unlock()
+		return nil
+	}
+	if !agentCompatAccessMatches(access, registration) {
+		s.ioStreamMutex.Unlock()
+		// Foreign and absent capabilities intentionally share the same inert result to prevent enumeration.
+		return nil
+	}
+	if registration.stream == nil || registration.streamID == "" {
+		s.removeAgentCompatCapabilityLocked(access.Capability.value, registration)
+		s.ioStreamMutex.Unlock()
+		return nil
+	}
+	stream := registration.stream
+	stored := registration.registration
+	current, live := s.ioStreams[registration.streamID]
+	if !live {
+		s.removeAgentCompatCapabilityLocked(access.Capability.value, registration)
+		s.ioStreamMutex.Unlock()
+		return nil
+	}
+	creatorMatches := stream.creatorUserID == stored.Owner.UserID
+	if stored.Purpose == AgentCompatCapabilityNAT {
+		creatorMatches = stream.creatorUserID == 0
+	}
+	if !access.ServerAccessAllowed || current != stream || !creatorMatches ||
+		stream.targetServerID != stored.TargetServerID || stream.purpose != stored.Purpose.streamPurpose() {
+		s.ioStreamMutex.Unlock()
+		return nil
+	}
+	stream.revoke()
+	endpoints := make([]io.ReadWriteCloser, 0, 2)
+	if stream.userIo != nil {
+		endpoints = append(endpoints, stream.userIo)
+	}
+	if stream.agentIo != nil {
+		endpoints = append(endpoints, stream.agentIo)
+	}
+	delete(s.ioStreams, registration.streamID)
+	s.publishIOStreamStateChangeLocked()
+	s.removeAgentCompatCapabilityLocked(access.Capability.value, registration)
+	s.ioStreamMutex.Unlock()
+
+	closeErrors := make([]error, 0, len(endpoints))
+	for _, endpoint := range endpoints {
+		if err := endpoint.Close(); err != nil {
+			closeErrors = append(closeErrors, err)
+		}
+	}
+	return errors.Join(closeErrors...)
+}
+
+func (s *NezhaHandler) UnregisterAgentCompatIOStreamCapability(access AgentCompatCapabilityAccess) error {
+	s.ioStreamMutex.Lock()
+	defer s.ioStreamMutex.Unlock()
+	registration, exists := s.agentCompatCapabilities.active[access.Capability.value]
+	if !exists {
+		return nil
+	}
+	if registration.registration.Owner.PATID != access.Owner.PATID || !agentCompatAccessMatches(access, registration) {
+		return nil
+	}
+	if registration.stream != nil {
+		if current, live := s.ioStreams[registration.streamID]; live && current == registration.stream {
+			return ErrAgentCompatCapabilityBound
+		}
+	}
+	s.removeAgentCompatCapabilityLocked(access.Capability.value, registration)
+	return nil
+}
+
+func (s *NezhaHandler) removeAgentCompatCapabilityLocked(capability string, registration *agentCompatCapabilityRegistration) {
+	current, active := s.agentCompatCapabilities.active[capability]
+	if !active || current != registration {
+		return
+	}
+	delete(s.agentCompatCapabilities.active, capability)
+	patID := registration.registration.Owner.PATID
+	remaining := s.agentCompatCapabilities.activeByPAT[patID] - 1
+	if remaining == 0 {
+		delete(s.agentCompatCapabilities.activeByPAT, patID)
+	} else {
+		s.agentCompatCapabilities.activeByPAT[patID] = remaining
+	}
+	registration.publishLocked()
+}