diff --git a/metropolis/proto/api/BUILD.bazel b/metropolis/proto/api/BUILD.bazel
index 61d14fb..ef8885d 100644
--- a/metropolis/proto/api/BUILD.bazel
+++ b/metropolis/proto/api/BUILD.bazel
@@ -11,6 +11,7 @@
         "management.proto",
     ],
     visibility = ["//visibility:public"],
+    deps = ["//metropolis/proto/ext:ext_proto"],
 )
 
 go_proto_library(
@@ -19,6 +20,7 @@
     importpath = "source.monogon.dev/metropolis/proto/api",
     proto = ":api_proto",
     visibility = ["//visibility:public"],
+    deps = ["//metropolis/proto/ext:go_default_library"],
 )
 
 go_library(
diff --git a/metropolis/proto/api/aaa.proto b/metropolis/proto/api/aaa.proto
index e469d0d..faf6dda 100644
--- a/metropolis/proto/api/aaa.proto
+++ b/metropolis/proto/api/aaa.proto
@@ -18,6 +18,8 @@
 package metropolis.proto.api;
 option go_package = "source.monogon.dev/metropolis/proto/api";
 
+import "metropolis/proto/ext/authorization.proto";
+
 // Authentication, authorization and accounting.
 service AAA {
     // Escrow is an endpoint used to retrieve short-lived access credentials to
@@ -144,7 +146,13 @@
     // will lead to retrieving identities from with the same namespace of
     // entities.
     //
-    rpc Escrow(stream EscrowFromClient) returns (stream EscrowFromServer);
+    rpc Escrow(stream EscrowFromClient) returns (stream EscrowFromServer) {
+        option (metropolis.proto.ext.authorization) = {
+            // The AAA implementation performs its own checks as needed, so the
+            // RPC middleware should allow everything through.
+            allow_unauthenticated: true
+        };
+    }
 }
 
 message EscrowFromClient {
diff --git a/metropolis/proto/api/management.proto b/metropolis/proto/api/management.proto
index c0b8332..ae7dd8d 100644
--- a/metropolis/proto/api/management.proto
+++ b/metropolis/proto/api/management.proto
@@ -2,6 +2,8 @@
 package metropolis.proto.api;
 option go_package = "source.monogon.dev/metropolis/proto/api";
 
+import "metropolis/proto/ext/authorization.proto";
+
 // Management service available to Cluster Managers.
 service Management {
     // GetRegisterTicket retrieves the current RegisterTicket which is required
@@ -10,7 +12,11 @@
     // registration. Instead, it is used to guard the API surface of the
     // Register RPC from potential denial of service attacks, and can be
     // regenerated at any time in case it leaks.
-    rpc GetRegisterTicket(GetRegisterTicketRequest) returns (GetRegisterTicketResponse);
+    rpc GetRegisterTicket(GetRegisterTicketRequest) returns (GetRegisterTicketResponse) {
+        option (metropolis.proto.ext.authorization) = {
+            need: PERMISSION_GET_REGISTER_TICKET
+        };
+    }
 }
 
 message GetRegisterTicketRequest {