feat: add assignment readiness gate

server/domain/assignment.go

@@ -0,0 +1,50 @@
+package domain
+
+import (
+	"crypto/sha256"
+	"fmt"
+)
+
+type AllocationManifest struct {
+	AllocationID string
+	MatchID      string
+	ServerID     string
+	Region       string
+	Build        string
+	Protocol     int
+	Transport    string
+	RosterDigest string
+}
+
+type Assignment struct {
+	Allocation Allocation
+	Manifest   AllocationManifest
+	Endpoint   string
+}
+
+var ErrManifestRejected = fmt.Errorf("allocation manifest rejected")
+
+// VerifyAssignment is the assignment-ready gate. A Ready/Allocated process
+// has no client-facing endpoint until its signed manifest, allocator binding,
+// and hosted endpoint all pass this check.
+func VerifyAssignment(allocation Allocation, manifest AllocationManifest, endpoint string, signature []byte, verify func([]byte, []byte) bool) (Assignment, error) {
+	if allocation.State != ServerAllocated || allocation.AllocationID == "" || allocation.MatchID == "" || allocation.ServerID == "" || endpoint == "" || len(signature) == 0 || verify == nil {
+		return Assignment{}, ErrManifestRejected
+	}
+	if manifest.AllocationID != allocation.AllocationID || manifest.MatchID != allocation.MatchID || manifest.ServerID != allocation.ServerID || manifest.Region != allocation.Region || manifest.Build != allocation.Build || manifest.Protocol != allocation.Protocol || manifest.Transport != allocation.Transport || manifest.RosterDigest == "" {
+		return Assignment{}, ErrManifestRejected
+	}
+	if !verify(manifestBytes(manifest), signature) {
+		return Assignment{}, ErrManifestRejected
+	}
+	return Assignment{Allocation: allocation, Manifest: manifest, Endpoint: endpoint}, nil
+}
+
+func manifestBytes(manifest AllocationManifest) []byte {
+	canonical := fmt.Sprintf("%s\x00%s\x00%s\x00%s\x00%s\x00%d\x00%s\x00%s", manifest.AllocationID, manifest.MatchID, manifest.ServerID, manifest.Region, manifest.Build, manifest.Protocol, manifest.Transport, manifest.RosterDigest)
+	return []byte(canonical)
+}
+
+func ManifestDigest(manifest AllocationManifest) [32]byte {
+	return sha256.Sum256(manifestBytes(manifest))
+}