| /* |
| * Copyright (C) 2020 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| use crate::sys; |
| |
| use libc::{pid_t, uid_t}; |
| |
| /// Static utility functions to manage Binder process state. |
| pub struct ProcessState; |
| |
| impl ProcessState { |
| /// Start the Binder IPC thread pool |
| pub fn start_thread_pool() { |
| unsafe { |
| // Safety: Safe FFI |
| sys::ABinderProcess_startThreadPool(); |
| } |
| } |
| |
| /// Set the maximum number of threads that can be started in the threadpool. |
| /// |
| /// By default, after startThreadPool is called, this is 15. If it is called |
| /// additional times, it will only prevent the kernel from starting new |
| /// threads and will not delete already existing threads. |
| pub fn set_thread_pool_max_thread_count(num_threads: u32) { |
| unsafe { |
| // Safety: Safe FFI |
| sys::ABinderProcess_setThreadPoolMaxThreadCount(num_threads); |
| } |
| } |
| |
| /// Block on the Binder IPC thread pool |
| pub fn join_thread_pool() { |
| unsafe { |
| // Safety: Safe FFI |
| sys::ABinderProcess_joinThreadPool(); |
| } |
| } |
| } |
| |
| /// Static utility functions to manage Binder thread state. |
| pub struct ThreadState; |
| |
| impl ThreadState { |
| /// This returns the calling UID assuming that this thread is called from a |
| /// thread that is processing a binder transaction (for instance, in the |
| /// implementation of |
| /// [`Remotable::on_transact`](crate::Remotable::on_transact)). |
| /// |
| /// This can be used with higher-level system services to determine the |
| /// caller's identity and check permissions. |
| /// |
| /// Available since API level 29. |
| /// |
| /// \return calling uid or the current process's UID if this thread isn't |
| /// processing a transaction. |
| pub fn get_calling_uid() -> uid_t { |
| unsafe { |
| // Safety: Safe FFI |
| sys::AIBinder_getCallingUid() |
| } |
| } |
| |
| /// This returns the calling PID assuming that this thread is called from a |
| /// thread that is processing a binder transaction (for instance, in the |
| /// implementation of |
| /// [`Remotable::on_transact`](crate::Remotable::on_transact)). |
| /// |
| /// This can be used with higher-level system services to determine the |
| /// caller's identity and check permissions. However, when doing this, one |
| /// should be aware of possible TOCTOU problems when the calling process |
| /// dies and is replaced with another process with elevated permissions and |
| /// the same PID. |
| /// |
| /// Available since API level 29. |
| /// |
| /// \return calling pid or the current process's PID if this thread isn't |
| /// processing a transaction. |
| /// |
| /// If the transaction being processed is a oneway transaction, then this |
| /// method will return 0. |
| pub fn get_calling_pid() -> pid_t { |
| unsafe { |
| // Safety: Safe FFI |
| sys::AIBinder_getCallingPid() |
| } |
| } |
| |
| /// This function makes the client's security context available to the |
| /// service calling this function. This can be used for access control. |
| /// It does not suffer from the TOCTOU issues of get_calling_pid. |
| /// |
| /// Implementations of `check_permission` should use the given CStr |
| /// argument as context for selinux permission checks. If `None` is |
| /// given, the implementation should fall back to using the PID |
| /// instead. |
| /// |
| /// Note: `None` may be passed to the callback if the caller did not |
| /// `set_requesting_sid` on the serviced binder, or if the underlying |
| /// kernel is too old to support this feature. |
| pub fn with_calling_sid<T, F>(check_permission: F) -> T |
| where |
| for<'a> F: FnOnce(Option<&'a std::ffi::CStr>) -> T { |
| // Safety: AIBinder_getCallingSid returns a c-string pointer |
| // that is valid for a transaction. Also, the string returned |
| // is thread local. By restricting the lifetime of the CStr |
| // reference to the scope of the callback, we prevent it being |
| // used beyond the guaranteed lifetime. |
| check_permission(unsafe { |
| let sid = sys::AIBinder_getCallingSid(); |
| // AIBinder_getCallingSid() returns a '\0' terminated string |
| // or NULL. |
| if sid.is_null() { |
| None |
| } else { |
| Some(std::ffi::CStr::from_ptr(sid)) |
| } |
| }) |
| } |
| } |