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      1 // Copyright (c) 2012 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_SERVICES_BROKER_PROCESS_H_
      6 #define SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
      7 
      8 #include <string>
      9 #include <vector>
     10 
     11 #include "base/basictypes.h"
     12 #include "base/pickle.h"
     13 #include "base/process/process.h"
     14 
     15 namespace sandbox {
     16 
     17 // Create a new "broker" process to which we can send requests via an IPC
     18 // channel.
     19 // This is a low level IPC mechanism that is suitable to be called from a
     20 // signal handler.
     21 // A process would typically create a broker process before entering
     22 // sandboxing.
     23 // 1. BrokerProcess open_broker(read_whitelist, write_whitelist);
     24 // 2. CHECK(open_broker.Init(NULL));
     25 // 3. Enable sandbox.
     26 // 4. Use open_broker.Open() to open files.
     27 class BrokerProcess {
     28  public:
     29   // |denied_errno| is the error code returned when methods such as Open()
     30   // or Access() are invoked on a file which is not in the whitelist. EACCESS
     31   // would be a typical value.
     32   // |allowed_r_files| and |allowed_w_files| are white lists of files that can
     33   // be opened later via the Open() API, respectively for reading and writing.
     34   // A file available read-write should be listed in both.
     35   // |fast_check_in_client| and |quiet_failures_for_tests| are reserved for
     36   // unit tests, don't use it.
     37   explicit BrokerProcess(int denied_errno,
     38                          const std::vector<std::string>& allowed_r_files,
     39                          const std::vector<std::string>& allowed_w_files,
     40                          bool fast_check_in_client = true,
     41                          bool quiet_failures_for_tests = false);
     42   ~BrokerProcess();
     43   // Will initialize the broker process. There should be no threads at this
     44   // point, since we need to fork().
     45   // sandbox_callback is a function that should be called to enable the
     46   // sandbox in the broker.
     47   bool Init(bool (*sandbox_callback)(void));
     48 
     49   // Can be used in place of access(). Will be async signal safe.
     50   // X_OK will always return an error in practice since the broker process
     51   // doesn't support execute permissions.
     52   // It's similar to the access() system call and will return -errno on errors.
     53   int Access(const char* pathname, int mode) const;
     54   // Can be used in place of open(). Will be async signal safe.
     55   // The implementation only supports certain white listed flags and will
     56   // return -EPERM on other flags.
     57   // It's similar to the open() system call and will return -errno on errors.
     58   int Open(const char* pathname, int flags) const;
     59 
     60   int broker_pid() const { return broker_pid_; }
     61 
     62  private:
     63   enum IPCCommands {
     64     kCommandInvalid = 0,
     65     kCommandOpen,
     66     kCommandAccess,
     67   };
     68   int PathAndFlagsSyscall(enum IPCCommands command_type,
     69                           const char* pathname,
     70                           int flags) const;
     71   bool HandleRequest() const;
     72   bool HandleRemoteCommand(IPCCommands command_type,
     73                            int reply_ipc,
     74                            const Pickle& read_pickle,
     75                            PickleIterator iter) const;
     76 
     77   void AccessFileForIPC(const std::string& requested_filename,
     78                         int mode,
     79                         Pickle* write_pickle) const;
     80   void OpenFileForIPC(const std::string& requested_filename,
     81                       int flags,
     82                       Pickle* write_pickle,
     83                       std::vector<int>* opened_files) const;
     84   bool GetFileNameIfAllowedToAccess(const char*, int, const char**) const;
     85   bool GetFileNameIfAllowedToOpen(const char*, int, const char**) const;
     86   const int denied_errno_;
     87   bool initialized_;               // Whether we've been through Init() yet.
     88   bool is_child_;                  // Whether we're the child (broker process).
     89   bool fast_check_in_client_;      // Whether to forward a request that we know
     90                                    // will be denied to the broker.
     91   bool quiet_failures_for_tests_;  // Disable certain error message when
     92                                    // testing for failures.
     93   pid_t broker_pid_;               // The PID of the broker (child).
     94   const std::vector<std::string> allowed_r_files_;  // Files allowed for read.
     95   const std::vector<std::string> allowed_w_files_;  // Files allowed for write.
     96   int ipc_socketpair_;  // Our communication channel to parent or child.
     97   DISALLOW_IMPLICIT_CONSTRUCTORS(BrokerProcess);
     98 };
     99 
    100 }  // namespace sandbox
    101 
    102 #endif  // SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
    103