sandbox/linux/syscall_broker/broker_client.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SANDBOX_LINUX_SYSCALL_BROKER_BROKER_CLIENT_H_
   6 #define SANDBOX_LINUX_SYSCALL_BROKER_BROKER_CLIENT_H_
   7
   8 #include "base/macros.h"
   9 #include "sandbox/linux/syscall_broker/broker_channel.h"
  10 #include "sandbox/linux/syscall_broker/broker_common.h"
  11
  12 namespace sandbox {
  13
  14 namespace syscall_broker {
  15
  16 class BrokerPolicy;
  17
  18 // This class can be embedded in a sandboxed process and can be
  19 // used to perform certain system calls in another, presumably
  20 // non-sandboxed process (which embeds BrokerHost).
  21 // A key feature of this class is the ability to use some of its methods in a
  22 // thread-safe and async-signal safe way. The goal is to be able to use it to
  23 // replace the open() or access() system calls happening anywhere in a process
  24 // (as allowed for instance by seccomp-bpf's SIGSYS mechanism).
  25 class BrokerClient {
  26  public:
  27   // |policy| needs to match the policy used by BrokerHost. This
  28   // allows to predict some of the requests which will be denied
  29   // and save an IPC round trip.
  30   // |ipc_channel| needs to be a suitable SOCK_SEQPACKET unix socket.
  31   // |fast_check_in_client| should be set to true and
  32   // |quiet_failures_for_tests| to false unless you are writing tests.
  33   BrokerClient(const BrokerPolicy& policy,
  34                BrokerChannel::EndPoint ipc_channel,
  35                bool fast_check_in_client,
  36                bool quiet_failures_for_tests);
  37   ~BrokerClient();
  38
  39   // Can be used in place of access().
  40   // X_OK will always return an error in practice since the broker process
  41   // doesn't support execute permissions.
  42   // It's similar to the access() system call and will return -errno on errors.
  43   // This is async signal safe.
  44   int Access(const char* pathname, int mode) const;
  45   // Can be used in place of open().
  46   // The implementation only supports certain white listed flags and will
  47   // return -EPERM on other flags.
  48   // It's similar to the open() system call and will return -errno on errors.
  49   // This is async signal safe.
  50   int Open(const char* pathname, int flags) const;
  51
  52   // Get the file descriptor used for IPC. This is used for tests.
  53   int GetIPCDescriptor() const { return ipc_channel_.get(); }
  54
  55  private:
  56   const BrokerPolicy& broker_policy_;
  57   const BrokerChannel::EndPoint ipc_channel_;
  58   const bool fast_check_in_client_;  // Whether to forward a request that we
  59                                      // know will be denied to the broker. (Used
  60                                      // for tests).
  61   const bool quiet_failures_for_tests_;  // Disable certain error message when
  62                                          // testing for failures.
  63
  64   int PathAndFlagsSyscall(IPCCommand syscall_type,
  65                           const char* pathname,
  66                           int flags) const;
  67
  68   DISALLOW_COPY_AND_ASSIGN(BrokerClient);
  69 };
  70
  71 }  // namespace syscall_broker
  72
  73 }  // namespace sandbox
  74
  75 #endif  //  SANDBOX_LINUX_SYSCALL_BROKER_BROKER_CLIENT_H_