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Kernel: Add unveil('b')

Browse source 
This is a new "browse" permission that lets you open (and subsequently list
contents of) directories underneath the path, but not regular files or any other
types of files.
This commit is contained in:
Sergey Bugaev 2020-11-21 22:55:20 +03:00 committed by Andreas Kling
parent 23dc3ff0c2
commit 098070b767
Notes: sideshowbarker 2024-07-19 01:17:40 +09:00 
Author: https://github.com/bugaevc
Commit: https://github.com/SerenityOS/serenity/commit/098070b767d
Pull-request: https://github.com/SerenityOS/serenity/pull/4130
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
5 changed files with 30 additions and 6 deletions
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4
Base/usr/share/man/man2/unveil.md
View file

@ -28,6 +28,7 @@ include the following characters:
* `w`: May write to a file at this path
* `x`: May execute a program image at this path
* `c`: May create or remove a file at this path
* `b`: May browse directories at this path
A single `unveil()` call may specify multiple permission characters at once.
Subsequent `unveil()` calls may take away permissions from the ones allowed
@ -78,6 +79,9 @@ unveil("/etc/WindowServer/WindowServer.ini", "rwc");
// Allow the process to execute Calendar:
unveil("/bin/Calendar", "x");
// Allow the process to browse files from /usr/share:
unveil("/usr/share", "b");
// Disallow any further veil manipulation:
unveil(nullptr, nullptr);
```

2
Kernel/FileSystem/ProcFS.cpp
View file

@ -644,6 +644,8 @@ static Optional<KBuffer> procfs$pid_unveil(InodeIdentifier identifier)
permissions_builder.append('x');
if (unveiled_path.permissions & UnveiledPath::Access::CreateOrRemove)
permissions_builder.append('c');
if (unveiled_path.permissions & UnveiledPath::Access::Browse)
permissions_builder.append('b');
obj.add("permissions", permissions_builder.to_string());
}
array.finish();

24
Kernel/FileSystem/VirtualFileSystem.cpp
View file

@ -825,7 +825,13 @@ const UnveiledPath* VFS::find_matching_unveiled_path(StringView path)
for (auto& unveiled_path : Process::current()->unveiled_paths()) {
if (path == unveiled_path.path)
return &unveiled_path;
if (path.starts_with(unveiled_path.path) && path.length() > unveiled_path.path.length() && path[unveiled_path.path.length()] == '/')
if (!path.starts_with(unveiled_path.path))
continue;
// /foo/ and /foo/bar
if (unveiled_path.path.ends_with('/'))
return &unveiled_path;
// /foo and /foo/bar
if (path.length() > unveiled_path.path.length() && path[unveiled_path.path.length()] == '/')
return &unveiled_path;
}
return nullptr;
@ -863,10 +869,18 @@ KResult VFS::validate_path_against_process_veil(StringView path, int options)
return KSuccess;
}
if (options & O_RDONLY) {
if (!(unveiled_path->permissions & UnveiledPath::Access::Read)) {
dbg() << "Rejecting path '" << path << "' since it hasn't been unveiled with 'r' permission.";
dump_backtrace();
return KResult(-EACCES);
if (options & O_DIRECTORY) {
if (!(unveiled_path->permissions & (UnveiledPath::Access::Read | UnveiledPath::Access::Browse))) {
dbg() << "Rejecting path '" << path << "' since it hasn't been unveiled with 'r' or 'b' permissions.";
dump_backtrace();
return KResult(-EACCES);
}
} else {
if (!(unveiled_path->permissions & UnveiledPath::Access::Read)) {
dbg() << "Rejecting path '" << path << "' since it hasn't been unveiled with 'r' permission.";
dump_backtrace();
return KResult(-EACCES);
}
}
}
if (options & O_WRONLY) {

1
Kernel/Process.h
View file

@ -101,6 +101,7 @@ struct UnveiledPath {
Write = 2,
Execute = 4,
CreateOrRemove = 8,
Browse = 16,
};
String path;

5
Kernel/Syscalls/unveil.cpp
View file

@ -49,7 +49,7 @@ int Process::sys$unveil(Userspace<const Syscall::SC_unveil_params*> user_params)
if (!params.path.characters || !params.permissions.characters)
return -EINVAL;
if (params.permissions.length > 4)
if (params.permissions.length > 5)
return -EINVAL;
auto path = get_syscall_path_argument(params.path);
@ -79,6 +79,9 @@ int Process::sys$unveil(Userspace<const Syscall::SC_unveil_params*> user_params)
case 'c':
new_permissions |= UnveiledPath::Access::CreateOrRemove;
break;
case 'b':
new_permissions |= UnveiledPath::Access::Browse;
break;
default:
return -EINVAL;
}