libbinderwrapper: Add GetCallingUid() and GetCallingPid().

Add methods to BinderWrapper for getting the caller's UID
and PID while in a transaction.

Bug: 24988639
Change-Id: Ibd711fc6b3d83623d4bb1060838c65aaef30d76e

include/binderwrapper/binder_wrapper.h

@@ -17,6 +17,8 @@
 #ifndef SYSTEM_CORE_INCLUDE_BINDERWRAPPER_BINDER_WRAPPER_H_
 #define SYSTEM_CORE_INCLUDE_BINDERWRAPPER_BINDER_WRAPPER_H_
 
+#include <sys/types.h>
+
 #include <string>
 
 #include <base/callback.h>
@@ -68,6 +70,10 @@ class BinderWrapper {
   // Unregisters the callback, if any, for |binder|.
   virtual bool UnregisterForDeathNotifications(const sp<IBinder>& binder) = 0;
 
+  // When called while in a transaction, returns the caller's UID or PID.
+  virtual uid_t GetCallingUid() = 0;
+  virtual pid_t GetCallingPid() = 0;
+
  private:
   static BinderWrapper* instance_;
 };

include/binderwrapper/stub_binder_wrapper.h

@@ -77,6 +77,9 @@ class StubBinderWrapper : public BinderWrapper {
   }
   void clear_local_binders() { local_binders_.clear(); }
 
+  void set_calling_uid(uid_t uid) { calling_uid_ = uid; }
+  void set_calling_pid(pid_t pid) { calling_pid_ = pid; }
+
   // Sets the binder to return when |service_name| is passed to GetService() or
   // WaitForService().
   void SetBinderForService(const std::string& service_name,
@@ -97,6 +100,8 @@ class StubBinderWrapper : public BinderWrapper {
   bool RegisterForDeathNotifications(const sp<IBinder>& binder,
                                      const base::Closure& callback) override;
   bool UnregisterForDeathNotifications(const sp<IBinder>& binder) override;
+  uid_t GetCallingUid() override;
+  pid_t GetCallingPid() override;
 
  private:
   using ServiceMap = std::map<std::string, sp<IBinder>>;
@@ -116,6 +121,10 @@ class StubBinderWrapper : public BinderWrapper {
   // death.
   std::map<sp<IBinder>, base::Closure> death_callbacks_;
 
+  // Values to return from GetCallingUid() and GetCallingPid();
+  uid_t calling_uid_;
+  pid_t calling_pid_;
+
   DISALLOW_COPY_AND_ASSIGN(StubBinderWrapper);
 };
 

libbinderwrapper/real_binder_wrapper.cc

@@ -19,6 +19,7 @@
 #include <base/logging.h>
 #include <binder/Binder.h>
 #include <binder/IBinder.h>
+#include <binder/IPCThreadState.h>
 #include <binder/IServiceManager.h>
 
 namespace android {
@@ -111,4 +112,12 @@ bool RealBinderWrapper::UnregisterForDeathNotifications(
   return true;
 }
 
+uid_t RealBinderWrapper::GetCallingUid() {
+  return IPCThreadState::self()->getCallingUid();
+}
+
+pid_t RealBinderWrapper::GetCallingPid() {
+  return IPCThreadState::self()->getCallingPid();
+}
+
 }  // namespace android

libbinderwrapper/real_binder_wrapper.h

@@ -38,6 +38,8 @@ class RealBinderWrapper : public BinderWrapper {
   bool RegisterForDeathNotifications(const sp<IBinder>& binder,
                                      const base::Closure& callback) override;
   bool UnregisterForDeathNotifications(const sp<IBinder>& binder) override;
+  uid_t GetCallingUid() override;
+  pid_t GetCallingPid() override;
 
  private:
   class DeathRecipient;

libbinderwrapper/stub_binder_wrapper.cc

@@ -22,7 +22,9 @@
 
 namespace android {
 
-StubBinderWrapper::StubBinderWrapper() = default;
+StubBinderWrapper::StubBinderWrapper()
+    : calling_uid_(-1),
+      calling_pid_(-1) {}
 
 StubBinderWrapper::~StubBinderWrapper() = default;
 
@@ -73,4 +75,12 @@ bool StubBinderWrapper::UnregisterForDeathNotifications(
   return true;
 }
 
+uid_t StubBinderWrapper::GetCallingUid() {
+  return calling_uid_;
+}
+
+pid_t StubBinderWrapper::GetCallingPid() {
+  return calling_pid_;
+}
+
 }  // namespace android