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// Copyright 2013 The Chromium Authors
// 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 <sys/types.h>
#include "build/build_config.h"
// Link errors are tedious to track, raise a compile-time error instead.
#if BUILDFLAG(IS_ANDROID)
#error "Android is not supported."
#endif // BUILDFLAG(IS_ANDROID).
#include <string>
#include <vector>
#include "sandbox/linux/system_headers/capability.h"
#include "sandbox/sandbox_export.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 SANDBOX_EXPORT Credentials {
public:
// For brevity, we only expose enums for the subset of capabilities we use.
// This can be expanded as the need arises.
enum class Capability {
SYS_CHROOT,
SYS_ADMIN,
};
Credentials() = delete;
Credentials(const Credentials&) = delete;
Credentials& operator=(const Credentials&) = delete;
// Checks that the set of RES-uids and the set of RES-gids have
// one element each and returns that element in |resuid| and |resgid|
// respectively. It's OK to pass NULL as one or both of the ids.
static bool GetRESIds(uid_t* resuid, gid_t* resgid);
// Sets gid and uid maps. See man newgidmap(1)/newuidmap(1) for details.
static bool SetGidAndUidMaps(gid_t gid, uid_t uid);
// Drops all capabilities in the effective, inheritable and permitted sets for
// the current thread. For security reasons, since capabilities are
// per-thread, the caller is responsible for ensuring it is single-threaded
// when calling this API.
// |proc_fd| must be a file descriptor to /proc/ and remains owned by
// the caller.
[[nodiscard]] static bool DropAllCapabilities(int proc_fd);
// A similar API which assumes that it can open /proc/self/ by itself.
[[nodiscard]] static bool DropAllCapabilities();
// Sets the effective and permitted capability sets for the current thread to
// the list of capabiltiies in |caps|. All other capability flags are cleared.
[[nodiscard]] static bool SetCapabilities(
int proc_fd,
const std::vector<Capability>& caps);
// Versions of the above functions which do not check that the process is
// single-threaded. After calling these functions, capabilities of other
// threads will not be changed. This is dangerous, do not use unless you know
// what you are doing.
[[nodiscard]] static bool DropAllCapabilitiesOnCurrentThread();
[[nodiscard]] static bool SetCapabilitiesOnCurrentThread(
const std::vector<Capability>& caps);
// Returns true if the current thread has either the effective, permitted, or
// inheritable flag set for the given capability.
static bool HasCapability(Capability cap);
// Returns true iff there is any capability in any of the capabilities sets
// of the current thread.
static bool HasAnyCapability();
// Returns whether the kernel supports CLONE_NEWUSER and whether it would be
// possible to immediately move to a new user namespace. There is no point
// in using this method right before calling MoveToNewUserNS(), simply call
// MoveToNewUserNS() immediately. This method is only useful to test the
// ability to move to a user namespace ahead of time.
static bool CanCreateProcessInNewUserNS();
// Moves 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.
// This will fail if the process is not mono-threaded.
[[nodiscard]] static bool MoveToNewUserNS();
// Removes 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.
// |proc_fd| must be a file descriptor to /proc/ and must be the only open
// directory file descriptor of the process.
//
// CRITICAL:
// - the caller must close |proc_fd| eventually or access to the file
// system can be recovered.
// - DropAllCapabilities() must be called to prevent escapes.
[[nodiscard]] static bool DropFileSystemAccess(int proc_fd);
// This function returns true if the process can still access the filesystem.
static bool HasFileSystemAccess();
// Forks and drops capabilities in the child.
static pid_t ForkAndDropCapabilitiesInChild();
};
} // namespace sandbox.
#endif // SANDBOX_LINUX_SERVICES_CREDENTIALS_H_
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