1 // Copyright (c) 2013 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_CREDENTIALS_H_ 6 #define SANDBOX_LINUX_SERVICES_CREDENTIALS_H_ 7 8 #include "build/build_config.h" 9 // Link errors are tedious to track, raise a compile-time error instead. 10 #if defined(OS_ANDROID) 11 #error "Android is not supported." 12 #endif // defined(OS_ANDROID). 13 14 #include <string> 15 #include <vector> 16 17 #include "base/compiler_specific.h" 18 #include "base/macros.h" 19 #include "sandbox/linux/system_headers/capability.h" 20 #include "sandbox/sandbox_export.h" 21 22 namespace sandbox { 23 24 // This class should be used to manipulate the current process' credentials. 25 // It is currently a stub used to manipulate POSIX.1e capabilities as 26 // implemented by the Linux kernel. 27 class SANDBOX_EXPORT Credentials { 28 public: 29 // For brevity, we only expose enums for the subset of capabilities we use. 30 // This can be expanded as the need arises. 31 enum class Capability { 32 SYS_CHROOT, 33 SYS_ADMIN, 34 }; 35 36 // Drop all capabilities in the effective, inheritable and permitted sets for 37 // the current thread. For security reasons, since capabilities are 38 // per-thread, the caller is responsible for ensuring it is single-threaded 39 // when calling this API. 40 // |proc_fd| must be a file descriptor to /proc/ and remains owned by 41 // the caller. 42 static bool DropAllCapabilities(int proc_fd) WARN_UNUSED_RESULT; 43 // A similar API which assumes that it can open /proc/self/ by itself. 44 static bool DropAllCapabilities() WARN_UNUSED_RESULT; 45 // Sets the effective and permitted capability sets for the current thread to 46 // the list of capabiltiies in |caps|. All other capability flags are cleared. 47 static bool SetCapabilities(int proc_fd, 48 const std::vector<Capability>& caps) 49 WARN_UNUSED_RESULT; 50 51 // Versions of the above functions which do not check that the process is 52 // single-threaded. After calling these functions, capabilities of other 53 // threads will not be changed. This is dangerous, do not use unless you nkow 54 // what you are doing. 55 static bool DropAllCapabilitiesOnCurrentThread() WARN_UNUSED_RESULT; 56 static bool SetCapabilitiesOnCurrentThread( 57 const std::vector<Capability>& caps) WARN_UNUSED_RESULT; 58 59 // Returns true if the current thread has either the effective, permitted, or 60 // inheritable flag set for the given capability. 61 static bool HasCapability(Capability cap); 62 63 // Return true iff there is any capability in any of the capabilities sets 64 // of the current thread. 65 static bool HasAnyCapability(); 66 67 // Returns whether the kernel supports CLONE_NEWUSER and whether it would be 68 // possible to immediately move to a new user namespace. There is no point 69 // in using this method right before calling MoveToNewUserNS(), simply call 70 // MoveToNewUserNS() immediately. This method is only useful to test the 71 // ability to move to a user namespace ahead of time. 72 static bool CanCreateProcessInNewUserNS(); 73 74 // Move the current process to a new "user namespace" as supported by Linux 75 // 3.8+ (CLONE_NEWUSER). 76 // The uid map will be set-up so that the perceived uid and gid will not 77 // change. 78 // If this call succeeds, the current process will be granted a full set of 79 // capabilities in the new namespace. 80 // This will fail if the process is not mono-threaded. 81 static bool MoveToNewUserNS() WARN_UNUSED_RESULT; 82 83 // Remove the ability of the process to access the file system. File 84 // descriptors which are already open prior to calling this API remain 85 // available. 86 // The implementation currently uses chroot(2) and requires CAP_SYS_CHROOT. 87 // CAP_SYS_CHROOT can be acquired by using the MoveToNewUserNS() API. 88 // |proc_fd| must be a file descriptor to /proc/ and must be the only open 89 // directory file descriptor of the process. 90 // 91 // CRITICAL: 92 // - the caller must close |proc_fd| eventually or access to the file 93 // system can be recovered. 94 // - DropAllCapabilities() must be called to prevent escapes. 95 static bool DropFileSystemAccess(int proc_fd) WARN_UNUSED_RESULT; 96 97 // Forks and drops capabilities in the child. 98 static pid_t ForkAndDropCapabilitiesInChild(); 99 100 private: 101 DISALLOW_IMPLICIT_CONSTRUCTORS(Credentials); 102 }; 103 104 } // namespace sandbox. 105 106 #endif // SANDBOX_LINUX_SERVICES_CREDENTIALS_H_ 107
