Linux sandbox: move CurrentProcessHasOpenDirectories

sandbox/linux/services/credentials.h

 // Copyright (c) 2013 The Chromium 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 SANDBOX_LINUX_SERVICES_CREDENTIALS_H_
 #define SANDBOX_LINUX_SERVICES_CREDENTIALS_H_
 
 #include "build/build_config.h"
 // Link errors are tedious to track, raise a compile-time error instead.
 #if defined(OS_ANDROID)
 #error "Android is not supported."
 #endif  // defined(OS_ANDROID).
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace sandbox {
 
 // This class should be used to manipulate the current process' credentials.
 // It is currently a stub used to manipulate POSIX.1e capabilities as
 // implemented by the Linux kernel.
 class Credentials {
  public:
   Credentials();
   ~Credentials();
 
+  // Checks whether the current process has any directory file descriptor open.
+  // Directory file descriptors are "capabilities" that would let a process use
+  // system calls such as openat() to bypass restrictions such as
+  // DropFileSystemAccess().
+  // Sometimes it's useful to call HasOpenDirectory() after file system access
+  // has been dropped. In this case, |proc_fd| should be a file descriptor to
+  // /proc. The file descriptor in |proc_fd| will be ignored by
+  // HasOpenDirectory() and remains owned by the caller. It is very important
+  // for the caller to close it.
+  // If /proc is available, |proc_fd| can be passed as -1.
+  // If |proc_fd| is -1 and /proc is not available, this function will return
+  // false.
+  bool HasOpenDirectory(int proc_fd);
+
   // Drop all capabilities in the effective, inheritable and permitted sets for
   // the current process.
   bool DropAllCapabilities();
   // Return true iff there is any capability in any of the capabilities sets
   // of the current process.
   bool HasAnyCapability() const;
   // Returns the capabilities of the current process in textual form, as
   // documented in libcap2's cap_to_text(3). This is mostly useful for
   // debugging and tests.
   scoped_ptr<std::string> GetCurrentCapString() const;
 
   // Move the current process to a new "user namespace" as supported by Linux
   // 3.8+ (CLONE_NEWUSER).
   // The uid map will be set-up so that the perceived uid and gid will not
   // change.
   // If this call succeeds, the current process will be granted a full set of
   // capabilities in the new namespace.
   bool MoveToNewUserNS();
 
   // Remove the ability of the process to access the file system. File
   // descriptors which are already open prior to calling this API remain
   // available.
   // The implementation currently uses chroot(2) and requires CAP_SYS_CHROOT.
   // CAP_SYS_CHROOT can be acquired by using the MoveToNewUserNS() API.
   // Make sure to call DropAllCapabilities() after this call to prevent
   // escapes.
-  // To be secure, it's very important for this API to not be called with any
-  // directory file descriptor present. TODO(jln): integrate with
-  // crbug.com/269806 when available.
+  // To be secure, it's very important for this API to not be called while the
+  // process has any directory file descriptor open.
   bool DropFileSystemAccess();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Credentials);
 };
 
 }  // namespace sandbox.
 
 #endif  // SANDBOX_LINUX_SERVICES_CREDENTIALS_H_