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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/LexicalPath.h>
#include <AK/StringView.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
#include <Kernel/Process.h>
namespace Kernel {
int Process::sys$unveil(Userspace<const Syscall::SC_unveil_params*> user_params)
{
Syscall::SC_unveil_params params;
if (!copy_from_user(¶ms, user_params))
return -EFAULT;
if (!params.path.characters && !params.permissions.characters) {
m_veil_state = VeilState::Locked;
return 0;
}
if (m_veil_state == VeilState::Locked)
return -EPERM;
if (!params.path.characters || !params.permissions.characters)
return -EINVAL;
if (params.permissions.length > 5)
return -EINVAL;
auto path = get_syscall_path_argument(params.path);
if (path.is_error())
return path.error();
if (path.value().is_empty() || path.value().characters()[0] != '/')
return -EINVAL;
auto permissions = copy_string_from_user(params.permissions);
if (permissions.is_null())
return -EFAULT;
// Let's work out permissions first...
unsigned new_permissions = 0;
for (const char permission : permissions) {
switch (permission) {
case 'r':
new_permissions |= UnveilAccess::Read;
break;
case 'w':
new_permissions |= UnveilAccess::Write;
break;
case 'x':
new_permissions |= UnveilAccess::Execute;
break;
case 'c':
new_permissions |= UnveilAccess::CreateOrRemove;
break;
case 'b':
new_permissions |= UnveilAccess::Browse;
break;
default:
return -EINVAL;
}
}
// Now, let's try and resolve the path and obtain custody of the inode on the disk, and if not, bail out with
// the error from resolve_path_without_veil()
// However, if the user specified unveil() with "c" permissions, we don't set errno if ENOENT is encountered,
// because they most likely intend the program to create the file for them later on.
// If this case is encountered, the parent node of the path is returned and the custody of that inode is used instead.
RefPtr<Custody> parent_custody; // Parent inode in case of ENOENT
String new_unveiled_path;
auto custody_or_error = VFS::the().resolve_path_without_veil(path.value(), root_directory(), &parent_custody);
if (!custody_or_error.is_error()) {
new_unveiled_path = custody_or_error.value()->absolute_path();
} else if (custody_or_error.error() == -ENOENT && parent_custody && (new_permissions & UnveilAccess::CreateOrRemove)) {
String basename = LexicalPath(path.value()).basename();
new_unveiled_path = String::formatted("{}/{}", parent_custody->absolute_path(), basename);
} else {
// FIXME Should this be EINVAL?
return custody_or_error.error();
}
LexicalPath lexical_path(new_unveiled_path);
auto it = lexical_path.parts().begin();
auto& matching_node = m_unveiled_paths.traverse_until_last_accessible_node(it, lexical_path.parts().end());
if (it.is_end()) {
auto old_permissions = matching_node.permissions();
// Allow "elevating" the permissions when the permissions are inherited from root (/),
// as that would be the first time this path is unveiled.
if (old_permissions != UnveilAccess::None || !matching_node.permissions_inherited_from_root()) {
if (new_permissions & ~old_permissions)
return -EPERM;
}
matching_node.set_metadata({ matching_node.path(), (UnveilAccess)new_permissions, true, false });
return 0;
}
matching_node.insert(
it,
lexical_path.parts().end(),
{ new_unveiled_path, (UnveilAccess)new_permissions, true },
[](auto& parent, auto& it) -> Optional<UnveilMetadata> { return UnveilMetadata { String::formatted("{}/{}", parent.path(), *it), parent.permissions(), false, parent.permissions_inherited_from_root() }; });
VERIFY(m_veil_state != VeilState::Locked);
m_veil_state = VeilState::Dropped;
return 0;
}
}
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