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https://github.com/RGBCube/serenity
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e598f22768
Check if the process we are currently running is in a jail, and if that is the case, fail early with the EPERM error code. Also, as Brian noted, we should also disallow attaching to a jail in case of already running within a setid executable, as this leaves the user with false thinking of being secure (because you can't exec new setid binaries), but the current program is still marked setid, which means that at the very least we gained permissions while we didn't expect it, so let's block it.
78 lines
2.9 KiB
C++
78 lines
2.9 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Userspace.h>
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#include <Kernel/Jail.h>
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#include <Kernel/JailManagement.h>
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#include <Kernel/Process.h>
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#include <Kernel/StdLib.h>
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#include <LibC/sys/ioctl_numbers.h>
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namespace Kernel {
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constexpr size_t jail_name_max_size = 50;
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ErrorOr<FlatPtr> Process::sys$jail_create(Userspace<Syscall::SC_jail_create_params*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::jail));
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auto params = TRY(copy_typed_from_user(user_params));
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auto jail_name = TRY(get_syscall_path_argument(params.name));
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if (jail_name->length() > jail_name_max_size)
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return ENAMETOOLONG;
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params.index = TRY(m_attached_jail.with([&](auto& my_jail) -> ErrorOr<u64> {
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// Note: If we are already in a jail, don't let the process to be able to create other jails
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// even if it will not be able to join them later on. The reason for this is to prevent as much as possible
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// any info leak about the "outside world" jail metadata.
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if (my_jail)
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return Error::from_errno(EPERM);
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auto jail = TRY(JailManagement::the().create_jail(move(jail_name)));
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return jail->index().value();
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}));
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// Note: We do the copy_to_user outside of the m_attached_jail Spinlock locked scope because
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// we rely on page faults to work properly.
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TRY(copy_to_user(user_params, ¶ms));
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return 0;
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}
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ErrorOr<FlatPtr> Process::sys$jail_attach(Userspace<Syscall::SC_jail_attach_params const*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::jail));
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// NOTE: Because the user might run a binary that is using this syscall and
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// that binary was marked as SUID, then the user might be unaware of the
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// fact that while no new setuid binaries might be executed, he is already
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// running within such binary so for the sake of completeness and preventing
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// naive sense of being secure, we should block that.
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TRY(with_protected_data([&](auto& protected_data) -> ErrorOr<void> {
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if (protected_data.executable_is_setid)
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return EPERM;
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return {};
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}));
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auto params = TRY(copy_typed_from_user(user_params));
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return m_attached_jail.with([&](auto& my_jail) -> ErrorOr<FlatPtr> {
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// Note: If we are already in a jail, don't let the process escape it even if
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// it knows there are other jails.
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// Note: To ensure the process doesn't try to maliciously enumerate all jails
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// in the system, just return EPERM before doing anything else.
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if (my_jail)
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return EPERM;
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auto jail = JailManagement::the().find_jail_by_index(static_cast<JailIndex>(params.index));
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if (!jail)
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return EINVAL;
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my_jail = *jail;
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my_jail->attach_count().with([&](auto& attach_count) {
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attach_count++;
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});
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return 0;
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});
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}
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}
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