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// Copyright 2015 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_NAMESPACE_UTILS_H_
#define SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
#include <sys/types.h>
#include <type_traits>
#include "sandbox/sandbox_export.h"
namespace sandbox {
// Utility functions for using Linux namepaces.
class SANDBOX_EXPORT NamespaceUtils {
public:
static_assert(std::is_same<uid_t, gid_t>::value,
"uid_t and gid_t must be the same type");
// generic_id_t can be used for either uid_t or gid_t.
typedef uid_t generic_id_t;
NamespaceUtils() = delete;
NamespaceUtils(const NamespaceUtils&) = delete;
NamespaceUtils& operator=(const NamespaceUtils&) = delete;
// Write a uid or gid mapping from |id| to |id| in |map_file|. This function
// is async-signal-safe.
[[nodiscard]] static bool WriteToIdMapFile(const char* map_file,
generic_id_t id);
// Returns true if unprivileged namespaces of type |type| is supported
// (meaning that both CLONE_NEWUSER and type are are supported). |type| must
// be one of CLONE_NEWIPC, CLONE_NEWNET, CLONE_NEWNS, CLONE_NEWPID,
// CLONE_NEWUSER, or CLONE_NEWUTS. This relies on access to /proc, so it will
// not work from within a sandbox.
static bool KernelSupportsUnprivilegedNamespace(int type);
// Returns true if the kernel supports denying setgroups in a user namespace.
// On kernels where this is supported, DenySetgroups must be called before a
// gid mapping can be added.
static bool KernelSupportsDenySetgroups();
// Disables setgroups() within the current user namespace. On Linux 3.18.2 and
// later, this is required in order to write to /proc/self/gid_map without
// having CAP_SETGID. Callers can determine whether is this needed with
// KernelSupportsDenySetgroups. This function is async-signal-safe.
[[nodiscard]] static bool DenySetgroups();
};
} // namespace sandbox
#endif // SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
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