libchromeos: Support setting uid/gid of child processes in process.h

chromeos/process.h

 // Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_PROCESS_H_
 #define CHROMEOS_PROCESS_H_
 
 #include <sys/types.h>
 
 #include <map>
@@ skipping 33 matching lines @@
   }
 
   // Redirects stderr and stdout to |output_file|.
   virtual void RedirectOutput(const std::string& output_file) = 0;
 
   // Indicates we want to redirect |child_fd| in the child process's
   // file table to a pipe.  |child_fd| will be available for reading
   // from child process's perspective iff |is_input|.
   virtual void RedirectUsingPipe(int child_fd, bool is_input) = 0;
 
+  // Set the real/effective/saved user ID of the child process.
+  virtual void SetUid(uid_t uid) = 0;
+
+  // Set the real/effective/saved group ID of the child process.
+  virtual void SetGid(gid_t gid) = 0;
+
   // Gets the pipe file descriptor mapped to the process's |child_fd|.
   virtual int GetPipe(int child_fd) = 0;
 
   // Starts this process, returning true if successful.
   virtual bool Start() = 0;
 
   // Waits for this process to finish.  Returns the process's exit
-  // status if it exited normally, or otherwise returns -1.
+  // status if it exited normally, or otherwise returns -1.  Note
+  // that kErrorExitStatus may be returned if an error occurred
+  // after forking and before execing the child process.
   virtual int Wait() = 0;
 
   // Start and wait for this process to finish.  Returns same value as
   // Wait().
   virtual int Run() = 0;
 
   // Returns the pid of this process or else returns 0 if there is no
   // corresponding process (either because it has not yet been started
   // or has since exited).
   virtual pid_t pid() = 0;
@@ skipping 11 matching lines @@
 
   // Same as Reset but reads the pid from |pid_file|.  Returns false
   // only when the file cannot be read/parsed.
   virtual bool ResetPidByFile(const std::string& pid_file) = 0;
 
   // Releases the process so that on destruction, the process is not killed.
   virtual pid_t Release() = 0;
 
   // Returns if |pid| is a currently running process.
   static bool ProcessExists(pid_t pid);
+
+  // When returned from Wait or Run, indicates an error may have occurred
+  // creating the process.
+  enum { kErrorExitStatus = 127 };
 };
 
 class ProcessImpl : public Process {
  public:
   ProcessImpl();
   virtual ~ProcessImpl();
 
   virtual void AddArg(const std::string& arg);
   virtual void RedirectOutput(const std::string& output_file);
   virtual void RedirectUsingPipe(int child_fd, bool is_input);
+  virtual void SetUid(uid_t uid);
+  virtual void SetGid(gid_t gid);
   virtual int GetPipe(int child_fd);
   virtual bool Start();
   virtual int Wait();
   virtual int Run();
   virtual pid_t pid();
   virtual bool Kill(int signal, int timeout);
   virtual void Reset(pid_t pid);
   virtual bool ResetPidByFile(const std::string& pid_file);
   virtual pid_t Release();
 
  protected:
   struct PipeInfo {
     PipeInfo() : parent_fd_(-1), child_fd_(-1), is_input_(false) {}
     // Parent (our) side of the pipe to the the child process.
     int parent_fd_;
     // Child's side of the pipe to the parent.
     int child_fd_;
     // Is this an input or output pipe from child's perspective.
     bool is_input_;
   };
   typedef std::map<int, PipeInfo> PipeMap;
 
-  std::string output_file_;
-  std::vector<std::string> arguments_;
-  // Map of child target file descriptors (first) to information about
-  // pipes created (second).
-  PipeMap pipe_map_;
-
   void UpdatePid(pid_t new_pid);
   bool PopulatePipeMap();
 
  private:
   // Pid of currently managed process or 0 if no currently managed
   // process.  pid must not be modified except by calling
   // UpdatePid(new_pid).
   pid_t pid_;
+  std::string output_file_;
+  std::vector<std::string> arguments_;
+  // Map of child target file descriptors (first) to information about
+  // pipes created (second).
+  PipeMap pipe_map_;
+  uid_t uid_;
+  gid_t gid_;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_PROCESS_H