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Kernel: Add Credentials to hold a set of user and group IDs

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This patch adds a new object to hold a Process's user credentials:

- UID, EUID, SUID
- GID, EGID, SGID, extra GIDs

Credentials are immutable and child processes initially inherit the
Credentials object from their parent.

Whenever a process changes one or more of its user/group IDs, a new
Credentials object is constructed.

Any code that wants to inspect and act on a set of credentials can now
do so without worrying about data races.
This commit is contained in:
Andreas Kling 2022-08-20 18:25:54 +02:00
parent bec314611d
commit 122d7d9533
11 changed files with 366 additions and 128 deletions
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53
Kernel/Process.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -11,6 +11,7 @@
#include <Kernel/API/Syscall.h>
#include <Kernel/Arch/InterruptDisabler.h>
#include <Kernel/Coredump.h>
#include <Kernel/Credentials.h>
#include <Kernel/Debug.h>
#include <Kernel/Devices/DeviceManagement.h>
#ifdef ENABLE_KERNEL_COVERAGE_COLLECTION
@ -85,7 +86,8 @@ UNMAP_AFTER_INIT void Process::initialize()
bool Process::in_group(GroupID gid) const
{
return this->gid() == gid || extra_gids().contains_slow(gid);
auto credentials = this->credentials();
return credentials->gid() == gid || credentials->extra_gids().contains_slow(gid);
}
void Process::kill_threads_except_self()
@ -224,12 +226,13 @@ ErrorOr<NonnullLockRefPtr<Process>> Process::try_create(LockRefPtr<Thread>& firs
{
auto space = TRY(Memory::AddressSpace::try_create(fork_parent ? &fork_parent->address_space() : nullptr));
auto unveil_tree = UnveilNode { TRY(KString::try_create("/"sv)), UnveilMetadata(TRY(KString::try_create("/"sv))) };
auto process = TRY(adopt_nonnull_lock_ref_or_enomem(new (nothrow) Process(move(name), uid, gid, ppid, is_kernel_process, move(current_directory), move(executable), tty, move(unveil_tree))));
auto credentials = TRY(Credentials::create(uid, gid, uid, gid, uid, gid, {}));
auto process = TRY(adopt_nonnull_lock_ref_or_enomem(new (nothrow) Process(move(name), move(credentials), ppid, is_kernel_process, move(current_directory), move(executable), tty, move(unveil_tree))));
TRY(process->attach_resources(move(space), first_thread, fork_parent));
return process;
}
Process::Process(NonnullOwnPtr<KString> name, UserID uid, GroupID gid, ProcessID ppid, bool is_kernel_process, LockRefPtr<Custody> current_directory, LockRefPtr<Custody> executable, TTY* tty, UnveilNode unveil_tree)
Process::Process(NonnullOwnPtr<KString> name, NonnullRefPtr<Credentials> credentials, ProcessID ppid, bool is_kernel_process, LockRefPtr<Custody> current_directory, LockRefPtr<Custody> executable, TTY* tty, UnveilNode unveil_tree)
: m_name(move(name))
, m_is_kernel_process(is_kernel_process)
, m_executable(move(executable))
@ -243,12 +246,7 @@ Process::Process(NonnullOwnPtr<KString> name, UserID uid, GroupID gid, ProcessID
m_protected_values.pid = allocate_pid();
m_protected_values.ppid = ppid;
m_protected_values.uid = uid;
m_protected_values.gid = gid;
m_protected_values.euid = uid;
m_protected_values.egid = gid;
m_protected_values.suid = uid;
m_protected_values.sgid = gid;
m_protected_values.credentials = move(credentials);
dbgln_if(PROCESS_DEBUG, "Created new process {}({})", m_name, this->pid().value());
}
@ -938,4 +936,39 @@ ErrorOr<void> Process::require_promise(Pledge promise)
return EPROMISEVIOLATION;
}
UserID Process::uid() const
{
return credentials()->uid();
}
GroupID Process::gid() const
{
return credentials()->gid();
}
UserID Process::euid() const
{
return credentials()->euid();
}
GroupID Process::egid() const
{
return credentials()->egid();
}
UserID Process::suid() const
{
return credentials()->suid();
}
GroupID Process::sgid() const
{
return credentials()->sgid();
}
NonnullRefPtr<Credentials> Process::credentials() const
{
return *m_protected_values.credentials;
}
}