Stephen Crane | 2a3c250 | 2020-06-16 17:48:35 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2020 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | use crate::sys; |
| 18 | |
| 19 | use libc::{pid_t, uid_t}; |
| 20 | |
| 21 | /// Static utility functions to manage Binder process state. |
| 22 | pub struct ProcessState; |
| 23 | |
| 24 | impl ProcessState { |
| 25 | /// Start the Binder IPC thread pool |
| 26 | pub fn start_thread_pool() { |
| 27 | unsafe { |
| 28 | // Safety: Safe FFI |
| 29 | sys::ABinderProcess_startThreadPool(); |
| 30 | } |
| 31 | } |
| 32 | |
| 33 | /// Set the maximum number of threads that can be started in the threadpool. |
| 34 | /// |
| 35 | /// By default, after startThreadPool is called, this is 15. If it is called |
| 36 | /// additional times, it will only prevent the kernel from starting new |
| 37 | /// threads and will not delete already existing threads. |
| 38 | pub fn set_thread_pool_max_thread_count(num_threads: u32) { |
| 39 | unsafe { |
| 40 | // Safety: Safe FFI |
| 41 | sys::ABinderProcess_setThreadPoolMaxThreadCount(num_threads); |
| 42 | } |
| 43 | } |
| 44 | |
| 45 | /// Block on the Binder IPC thread pool |
| 46 | pub fn join_thread_pool() { |
| 47 | unsafe { |
| 48 | // Safety: Safe FFI |
| 49 | sys::ABinderProcess_joinThreadPool(); |
| 50 | } |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | /// Static utility functions to manage Binder thread state. |
| 55 | pub struct ThreadState; |
| 56 | |
| 57 | impl ThreadState { |
| 58 | /// This returns the calling UID assuming that this thread is called from a |
| 59 | /// thread that is processing a binder transaction (for instance, in the |
| 60 | /// implementation of |
| 61 | /// [`Remotable::on_transact`](crate::Remotable::on_transact)). |
| 62 | /// |
| 63 | /// This can be used with higher-level system services to determine the |
| 64 | /// caller's identity and check permissions. |
| 65 | /// |
| 66 | /// Available since API level 29. |
| 67 | /// |
| 68 | /// \return calling uid or the current process's UID if this thread isn't |
| 69 | /// processing a transaction. |
| 70 | pub fn get_calling_uid() -> uid_t { |
| 71 | unsafe { |
| 72 | // Safety: Safe FFI |
| 73 | sys::AIBinder_getCallingUid() |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | /// This returns the calling PID assuming that this thread is called from a |
| 78 | /// thread that is processing a binder transaction (for instance, in the |
| 79 | /// implementation of |
| 80 | /// [`Remotable::on_transact`](crate::Remotable::on_transact)). |
| 81 | /// |
| 82 | /// This can be used with higher-level system services to determine the |
| 83 | /// caller's identity and check permissions. However, when doing this, one |
| 84 | /// should be aware of possible TOCTOU problems when the calling process |
| 85 | /// dies and is replaced with another process with elevated permissions and |
| 86 | /// the same PID. |
| 87 | /// |
| 88 | /// Available since API level 29. |
| 89 | /// |
| 90 | /// \return calling pid or the current process's PID if this thread isn't |
| 91 | /// processing a transaction. |
| 92 | /// |
| 93 | /// If the transaction being processed is a oneway transaction, then this |
| 94 | /// method will return 0. |
| 95 | pub fn get_calling_pid() -> pid_t { |
| 96 | unsafe { |
| 97 | // Safety: Safe FFI |
| 98 | sys::AIBinder_getCallingPid() |
| 99 | } |
| 100 | } |
Janis Danisevskis | 798a09a | 2020-08-18 08:35:38 -0700 | [diff] [blame^] | 101 | |
| 102 | /// This function makes the client's security context available to the |
| 103 | /// service calling this function. This can be used for access control. |
| 104 | /// It does not suffer from the TOCTOU issues of get_calling_pid. |
| 105 | /// |
| 106 | /// Implementations of `check_permission` should use the given CStr |
| 107 | /// argument as context for selinux permission checks. If `None` is |
| 108 | /// given, the implementation should fall back to using the PID |
| 109 | /// instead. |
| 110 | /// |
| 111 | /// Note: `None` may be passed to the callback if the caller did not |
| 112 | /// `set_requesting_sid` on the serviced binder, or if the underlying |
| 113 | /// kernel is too old to support this feature. |
| 114 | pub fn with_calling_sid<T, F>(check_permission: F) -> T |
| 115 | where |
| 116 | for<'a> F: FnOnce(Option<&'a std::ffi::CStr>) -> T { |
| 117 | // Safety: AIBinder_getCallingSid returns a c-string pointer |
| 118 | // that is valid for a transaction. Also, the string returned |
| 119 | // is thread local. By restricting the lifetime of the CStr |
| 120 | // reference to the scope of the callback, we prevent it being |
| 121 | // used beyond the guaranteed lifetime. |
| 122 | check_permission(unsafe { |
| 123 | let sid = sys::AIBinder_getCallingSid(); |
| 124 | // AIBinder_getCallingSid() returns a '\0' terminated string |
| 125 | // or NULL. |
| 126 | if sid.is_null() { |
| 127 | None |
| 128 | } else { |
| 129 | Some(std::ffi::CStr::from_ptr(sid)) |
| 130 | } |
| 131 | }) |
| 132 | } |
Stephen Crane | 2a3c250 | 2020-06-16 17:48:35 -0700 | [diff] [blame] | 133 | } |