libbinder: support calls over sockets
Minimal-ish change for basic binder RPC.
This enables binder to work over sockets. The main change to core code
is in 'Parcel' and 'BpBinder'. The Parcel format is now associated with
the binder that it is either for or a reply from (we no longer have
binder 'objects' for the kernel). BpBinder is extended to support
talking over sockets (ideally, this would be a subclass, but
IBinder::localBinder/remoteBinder mean there is a lot of code which
presupposes what type of binder we have).
In addition, we have a few new objects:
- RpcServer - set this up to serve a connection
- RpcConnection - symmetrical object handling dispatch to a known
server/client
- RpcAddress - (this will definitely change) randomly generated
addresses - this might include things like host VM context, ip
address, or similar in the future. In that case, the address
generation should be cryptographically secure.
- RpcState - this keeps track of known binders, their refcounts, and
async transactions, and it understand the binder socket wire
protocol
The connection itself looks like N socket accepts to a server (the
server might have M socket accepts back to the client for symmetrical
connections, that is connections which need more than nested
transactions). The number of these socket connections controls how many
synchronous transactions can be made. Wherever possible, the behavior
here seeks to mimick the binder driver, and some differences are
documented in the code.
After this CL merges, the future work I intend on completing includes:
- support to work over vsock
- performance benchmarking
- optimization of the socket code here (may include delaying refcounts)
- support to pass 'transitive' binders (pass a binder from one service
to a different service, to let it setup a new connection). This task
may be excluded from my efforts as a security hedge if I can manage.
- fuzzer for this wire format
- support for linkToDeath
- support for transaction encryption
- support for promoting from a weak pointer
- handling SIGPIPE for dead connections
- and many more! :)
Bug: 167966510
Test: binderRpcTest
Change-Id: I276c6e312f584b57f4e7a14389ea4a1d63cfa2f4
diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 1a4ede1..b91d72b 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -48,6 +48,7 @@
#include <utils/String16.h>
#include <private/binder/binder_module.h>
+#include "RpcState.h"
#include "Static.h"
#include "Utils.h"
@@ -191,6 +192,22 @@
status_t Parcel::flattenBinder(const sp<IBinder>& binder)
{
+ if (isForRpc()) {
+ if (binder) {
+ status_t status = writeInt32(1); // non-null
+ if (status != OK) return status;
+ RpcAddress address = RpcAddress::zero();
+ status = mConnection->state()->onBinderLeaving(mConnection, binder, &address);
+ if (status != OK) return status;
+ status = address.writeToParcel(this);
+ if (status != OK) return status;
+ } else {
+ status_t status = writeInt32(0); // null
+ if (status != OK) return status;
+ }
+ return finishFlattenBinder(binder);
+ }
+
flat_binder_object obj;
obj.flags = FLAT_BINDER_FLAG_ACCEPTS_FDS;
@@ -205,8 +222,13 @@
BpBinder *proxy = binder->remoteBinder();
if (proxy == nullptr) {
ALOGE("null proxy");
+ } else {
+ if (proxy->isRpcBinder()) {
+ ALOGE("Sending a socket binder over RPC is prohibited");
+ return INVALID_OPERATION;
+ }
}
- const int32_t handle = proxy ? proxy->getPrivateAccessorForHandle().handle() : 0;
+ const int32_t handle = proxy ? proxy->getPrivateAccessorForId().binderHandle() : 0;
obj.hdr.type = BINDER_TYPE_HANDLE;
obj.binder = 0; /* Don't pass uninitialized stack data to a remote process */
obj.handle = handle;
@@ -245,6 +267,26 @@
status_t Parcel::unflattenBinder(sp<IBinder>* out) const
{
+ if (isForRpc()) {
+ LOG_ALWAYS_FATAL_IF(mConnection == nullptr,
+ "RpcConnection required to read from remote parcel");
+
+ int32_t isNull;
+ status_t status = readInt32(&isNull);
+ if (status != OK) return status;
+
+ sp<IBinder> binder;
+
+ if (isNull & 1) {
+ auto addr = RpcAddress::zero();
+ status_t status = addr.readFromParcel(*this);
+ if (status != OK) return status;
+ binder = mConnection->state()->onBinderEntering(mConnection, addr);
+ }
+
+ return finishUnflattenBinder(binder, out);
+ }
+
const flat_binder_object* flat = readObject(false);
if (flat) {
@@ -511,6 +553,21 @@
mDeallocZero = true;
}
+void Parcel::markForBinder(const sp<IBinder>& binder) {
+ if (binder && binder->remoteBinder() && binder->remoteBinder()->isRpcBinder()) {
+ markForRpc(binder->remoteBinder()->getPrivateAccessorForId().rpcConnection());
+ }
+}
+
+void Parcel::markForRpc(const sp<RpcConnection>& connection) {
+ LOG_ALWAYS_FATAL_IF(connection == nullptr, "markForRpc requires connection");
+ mConnection = connection;
+}
+
+bool Parcel::isForRpc() const {
+ return mConnection != nullptr;
+}
+
void Parcel::updateWorkSourceRequestHeaderPosition() const {
// Only update the request headers once. We only want to point
// to the first headers read/written.
@@ -1070,6 +1127,11 @@
status_t Parcel::writeFileDescriptor(int fd, bool takeOwnership)
{
+ if (isForRpc()) {
+ ALOGE("Cannot write file descriptor to remote binder.");
+ return BAD_TYPE;
+ }
+
flat_binder_object obj;
obj.hdr.type = BINDER_TYPE_FD;
obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
@@ -2413,6 +2475,7 @@
mDataPos = 0;
ALOGV("initState Setting data size of %p to %zu", this, mDataSize);
ALOGV("initState Setting data pos of %p to %zu", this, mDataPos);
+ mConnection = nullptr;
mObjects = nullptr;
mObjectsSize = 0;
mObjectsCapacity = 0;