libbinder: RPC drop extra header info

A lot of the data written in interface tokens (work source, strict mode,
etc..) doesn't make sense in the context of RPC calls. Also, we don't
want to freeze this part of the wire protocol.

Bug: 167966510
Test: binderRpcTest
Change-Id: I5c0bb923d1d4c2a4ffa49b117dbed16bce0a1c20

1 files changed, 38 insertions, 32 deletions

diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index b91d72b87a..34a474b252 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -41,11 +41,12 @@
 #include <binder/TextOutput.h>
 
 #include <cutils/ashmem.h>
+#include <cutils/compiler.h>
 #include <utils/Flattenable.h>
 #include <utils/Log.h>
-#include <utils/misc.h>
-#include <utils/String8.h>
 #include <utils/String16.h>
+#include <utils/String8.h>
+#include <utils/misc.h>
 
 #include <private/binder/binder_module.h>
 #include "RpcState.h"
@@ -590,12 +591,14 @@ status_t Parcel::writeInterfaceToken(const String16& interface)
 }
 
 status_t Parcel::writeInterfaceToken(const char16_t* str, size_t len) {
-    const IPCThreadState* threadState = IPCThreadState::self();
-    writeInt32(threadState->getStrictModePolicy() | STRICT_MODE_PENALTY_GATHER);
-    updateWorkSourceRequestHeaderPosition();
-    writeInt32(threadState->shouldPropagateWorkSource() ?
-            threadState->getCallingWorkSourceUid() : IPCThreadState::kUnsetWorkSource);
-    writeInt32(kHeader);
+    if (CC_LIKELY(!isForRpc())) {
+        const IPCThreadState* threadState = IPCThreadState::self();
+        writeInt32(threadState->getStrictModePolicy() | STRICT_MODE_PENALTY_GATHER);
+        updateWorkSourceRequestHeaderPosition();
+        writeInt32(threadState->shouldPropagateWorkSource() ? threadState->getCallingWorkSourceUid()
+                                                            : IPCThreadState::kUnsetWorkSource);
+        writeInt32(kHeader);
+    }
 
     // currently the interface identification token is just its name as a string
     return writeString16(str, len);
@@ -642,31 +645,34 @@ bool Parcel::enforceInterface(const char16_t* interface,
                               size_t len,
                               IPCThreadState* threadState) const
 {
-    // StrictModePolicy.
-    int32_t strictPolicy = readInt32();
-    if (threadState == nullptr) {
-        threadState = IPCThreadState::self();
-    }
-    if ((threadState->getLastTransactionBinderFlags() &
-         IBinder::FLAG_ONEWAY) != 0) {
-      // For one-way calls, the callee is running entirely
-      // disconnected from the caller, so disable StrictMode entirely.
-      // Not only does disk/network usage not impact the caller, but
-      // there's no way to commuicate back any violations anyway.
-      threadState->setStrictModePolicy(0);
-    } else {
-      threadState->setStrictModePolicy(strictPolicy);
-    }
-    // WorkSource.
-    updateWorkSourceRequestHeaderPosition();
-    int32_t workSource = readInt32();
-    threadState->setCallingWorkSourceUidWithoutPropagation(workSource);
-    // vendor header
-    int32_t header = readInt32();
-    if (header != kHeader) {
-        ALOGE("Expecting header 0x%x but found 0x%x. Mixing copies of libbinder?", kHeader, header);
-        return false;
+    if (CC_LIKELY(!isForRpc())) {
+        // StrictModePolicy.
+        int32_t strictPolicy = readInt32();
+        if (threadState == nullptr) {
+            threadState = IPCThreadState::self();
+        }
+        if ((threadState->getLastTransactionBinderFlags() & IBinder::FLAG_ONEWAY) != 0) {
+            // For one-way calls, the callee is running entirely
+            // disconnected from the caller, so disable StrictMode entirely.
+            // Not only does disk/network usage not impact the caller, but
+            // there's no way to communicate back violations anyway.
+            threadState->setStrictModePolicy(0);
+        } else {
+            threadState->setStrictModePolicy(strictPolicy);
+        }
+        // WorkSource.
+        updateWorkSourceRequestHeaderPosition();
+        int32_t workSource = readInt32();
+        threadState->setCallingWorkSourceUidWithoutPropagation(workSource);
+        // vendor header
+        int32_t header = readInt32();
+        if (header != kHeader) {
+            ALOGE("Expecting header 0x%x but found 0x%x. Mixing copies of libbinder?", kHeader,
+                  header);
+            return false;
+        }
     }
+
     // Interface descriptor.
     size_t parcel_interface_len;
     const char16_t* parcel_interface = readString16Inplace(&parcel_interface_len);