From 09034a905676afd72d351994142fceece2ac48a2 Mon Sep 17 00:00:00 2001
From: Steven Moreland <smoreland@google.com>
Date: Wed, 31 May 2023 20:49:11 +0000
Subject: RPC binder: limit experimental wire protocol usage

Add runtime checks, because we only currently check the
defaults.

Fixes: 278946301
Test: binderRpcTest
Change-Id: I119c8c49d5938a9d6f36c29c1bb70732155c6037
---
 libs/binder/RpcState.cpp | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

(limited to 'libs/binder/RpcState.cpp')

diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index ff35f5f35c..5c1b2305a6 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -34,6 +34,10 @@
 
 #include <inttypes.h>
 
+#ifdef __ANDROID__
+#include <cutils/properties.h>
+#endif
+
 namespace android {
 
 using base::StringPrintf;
@@ -399,14 +403,27 @@ status_t RpcState::rpcRec(
 }
 
 bool RpcState::validateProtocolVersion(uint32_t version) {
-    if (version >= RPC_WIRE_PROTOCOL_VERSION_NEXT &&
-        version != RPC_WIRE_PROTOCOL_VERSION_EXPERIMENTAL) {
+    if (version == RPC_WIRE_PROTOCOL_VERSION_EXPERIMENTAL) {
+#if defined(__ANDROID__)
+        char codename[PROPERTY_VALUE_MAX];
+        property_get("ro.build.version.codename", codename, "");
+        if (!strcmp(codename, "REL")) {
+            ALOGE("Cannot use experimental RPC binder protocol on a release branch.");
+            return false;
+        }
+#else
+        // don't restrict on other platforms, though experimental should
+        // only really be used for testing, we don't have a good way to see
+        // what is shipping outside of Android
+#endif
+    } else if (version >= RPC_WIRE_PROTOCOL_VERSION_NEXT) {
         ALOGE("Cannot use RPC binder protocol version %u which is unknown (current protocol "
               "version "
               "is %u).",
               version, RPC_WIRE_PROTOCOL_VERSION);
         return false;
     }
+
     return true;
 }
 
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