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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/callback_forward.h"
     13 #include "base/pickle.h"
     14 #include "base/process/process.h"
     15 #include "sandbox/sandbox_export.h"
     16 
     17 namespace sandbox {
     18 
     19 // Create a new "broker" process to which we can send requests via an IPC
     20 // channel.
     21 // This is a low level IPC mechanism that is suitable to be called from a
     22 // signal handler.
     23 // A process would typically create a broker process before entering
     24 // sandboxing.
     25 // 1. BrokerProcess open_broker(read_whitelist, write_whitelist);
     26 // 2. CHECK(open_broker.Init(NULL));
     27 // 3. Enable sandbox.
     28 // 4. Use open_broker.Open() to open files.
     29 class SANDBOX_EXPORT BrokerProcess {
     30  public:
     31   // |denied_errno| is the error code returned when methods such as Open()
     32   // or Access() are invoked on a file which is not in the whitelist. EACCESS
     33   // would be a typical value.
     34   // |allowed_r_files| and |allowed_w_files| are white lists of files that can
     35   // be opened later via the Open() API, respectively for reading and writing.
     36   // A file available read-write should be listed in both.
     37   // |fast_check_in_client| and |quiet_failures_for_tests| are reserved for
     38   // unit tests, don't use it.
     39   explicit BrokerProcess(int denied_errno,
     40                          const std::vector<std::string>& allowed_r_files,
     41                          const std::vector<std::string>& allowed_w_files,
     42                          bool fast_check_in_client = true,
     43                          bool quiet_failures_for_tests = false);
     44   ~BrokerProcess();
     45   // Will initialize the broker process. There should be no threads at this
     46   // point, since we need to fork().
     47   // broker_process_init_callback will be called in the new broker process,
     48   // after fork() returns.
     49   bool Init(const base::Callback<bool(void)>& broker_process_init_callback);
     50 
     51   // Can be used in place of access(). Will be async signal safe.
     52   // X_OK will always return an error in practice since the broker process
     53   // doesn't support execute permissions.
     54   // It's similar to the access() system call and will return -errno on errors.
     55   int Access(const char* pathname, int mode) const;
     56   // Can be used in place of open(). Will be async signal safe.
     57   // The implementation only supports certain white listed flags and will
     58   // return -EPERM on other flags.
     59   // It's similar to the open() system call and will return -errno on errors.
     60   int Open(const char* pathname, int flags) const;
     61 
     62   int broker_pid() const { return broker_pid_; }
     63 
     64  private:
     65   enum IPCCommands {
     66     kCommandInvalid = 0,
     67     kCommandOpen,
     68     kCommandAccess,
     69   };
     70   int PathAndFlagsSyscall(enum IPCCommands command_type,
     71                           const char* pathname,
     72                           int flags) const;
     73   bool HandleRequest() const;
     74   bool HandleRemoteCommand(IPCCommands command_type,
     75                            int reply_ipc,
     76                            const Pickle& read_pickle,
     77                            PickleIterator iter) const;
     78 
     79   void AccessFileForIPC(const std::string& requested_filename,
     80                         int mode,
     81                         Pickle* write_pickle) const;
     82   void OpenFileForIPC(const std::string& requested_filename,
     83                       int flags,
     84                       Pickle* write_pickle,
     85                       std::vector<int>* opened_files) const;
     86   bool GetFileNameIfAllowedToAccess(const char*, int, const char**) const;
     87   bool GetFileNameIfAllowedToOpen(const char*, int, const char**) const;
     88   const int denied_errno_;
     89   bool initialized_;               // Whether we've been through Init() yet.
     90   bool is_child_;                  // Whether we're the child (broker process).
     91   bool fast_check_in_client_;      // Whether to forward a request that we know
     92                                    // will be denied to the broker.
     93   bool quiet_failures_for_tests_;  // Disable certain error message when
     94                                    // testing for failures.
     95   pid_t broker_pid_;               // The PID of the broker (child).
     96   const std::vector<std::string> allowed_r_files_;  // Files allowed for read.
     97   const std::vector<std::string> allowed_w_files_;  // Files allowed for write.
     98   int ipc_socketpair_;  // Our communication channel to parent or child.
     99   DISALLOW_IMPLICIT_CONSTRUCTORS(BrokerProcess);
    100 
    101   friend class BrokerProcessTestHelper;
    102 };
    103 
    104 }  // namespace sandbox
    105 
    106 #endif  // SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
    107