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Use NtCreateFile to get handle to reparse point

master
Jakub Konka 2020-07-14 23:06:55 +02:00
parent d17c9b3591
commit ae8abedbed
4 changed files with 131 additions and 43 deletions
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44
lib/std/os.zig
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@ -2394,36 +2394,37 @@ pub const readlinkC = @compileError("deprecated: renamed to readlinkZ");
/// See also `readlinkZ`.
pub fn readlinkW(file_path: [*:0]const u16, out_buffer: []u8) ReadLinkError![]u8 {
const w = windows;
const sharing = w.FILE_SHARE_DELETE | w.FILE_SHARE_READ | w.FILE_SHARE_WRITE;
const disposition = w.OPEN_EXISTING;
const flags = w.FILE_FLAG_BACKUP_SEMANTICS | w.FILE_FLAG_OPEN_REPARSE_POINT;
const handle = w.CreateFileW(file_path, 0, sharing, null, disposition, flags, null) catch |err| {
const dir = if (std.fs.path.isAbsoluteWindowsW(file_path)) null else std.fs.cwd().fd;
const handle = w.OpenAsReparsePoint(dir, file_path) catch |err| {
switch (err) {
error.SharingViolation => return error.AccessDenied,
error.PathAlreadyExists => unreachable,
error.PipeBusy => unreachable,
error.PathAlreadyExists => unreachable,
error.NoDevice => return error.FileNotFound,
else => |e| return e,
}
};
var reparse_buf align(@alignOf(w.REPARSE_DATA_BUFFER)) = [_]u8{0} ** (w.MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
var reparse_buf: [w.MAXIMUM_REPARSE_DATA_BUFFER_SIZE]u8 = undefined;
_ = try w.DeviceIoControl(handle, w.FSCTL_GET_REPARSE_POINT, null, reparse_buf[0..], null);
const reparse_struct = @ptrCast(*const w.REPARSE_DATA_BUFFER, &reparse_buf[0]);
// std.debug.warn("\n\n{x}\n\n", .{reparse_buf});
const reparse_struct = @ptrCast(*const w.REPARSE_DATA_BUFFER, @alignCast(@alignOf(w.REPARSE_DATA_BUFFER), &reparse_buf[0]));
switch (reparse_struct.ReparseTag) {
w.IO_REPARSE_TAG_SYMLINK => {
const alignment = @alignOf(w.SymbolicLinkReparseBuffer);
const buf = @ptrCast(*const w.SymbolicLinkReparseBuffer, @alignCast(alignment, &reparse_struct.DataBuffer[0]));
const offset = buf.SubstituteNameOffset / 2;
const len = buf.SubstituteNameLength / 2;
const f = buf.Flags;
const buf = @ptrCast(*const w.SymbolicLinkReparseBuffer, @alignCast(@alignOf(w.SymbolicLinkReparseBuffer), &reparse_struct.DataBuffer[0]));
const offset = buf.SubstituteNameOffset >> 1;
const len = buf.SubstituteNameLength >> 1;
const path_buf = @as([*]const u16, &buf.PathBuffer);
std.debug.warn("got symlink => offset={}, len={}, flags = {}, {}\n", .{ offset, len, f, w.SYMLINK_FLAG_RELATIVE });
// TODO handle absolute paths and namespace prefix
const out_len = std.unicode.utf16leToUtf8(out_buffer, path_buf[offset .. offset + len]) catch unreachable;
std.debug.warn("got symlink => utf8={}\n", .{out_buffer[0..out_len]});
return out_buffer[0..out_len];
const is_relative = buf.Flags & w.SYMLINK_FLAG_RELATIVE != 0;
return parseReadlinkPath(path_buf[offset .. offset + len], is_relative, out_buffer);
},
w.IO_REPARSE_TAG_MOUNT_POINT => {
@panic("TODO parse mount point");
const buf = @ptrCast(*const w.MountPointReparseBuffer, @alignCast(@alignOf(w.MountPointReparseBuffer), &reparse_struct.DataBuffer[0]));
const offset = buf.SubstituteNameOffset >> 1;
const len = buf.SubstituteNameLength >> 1;
const path_buf = @as([*]const u16, &buf.PathBuffer);
return parseReadlinkPath(path_buf[offset .. offset + len], false, out_buffer);
},
else => |value| {
std.debug.warn("unsupported symlink type: {}", .{value});
@ -2432,6 +2433,13 @@ pub fn readlinkW(file_path: [*:0]const u16, out_buffer: []u8) ReadLinkError![]u8
}
}
fn parseReadlinkPath(path: []const u16, is_relative: bool, out_buffer: []u8) []u8 {
const out_len = std.unicode.utf16leToUtf8(out_buffer, path) catch unreachable;
std.debug.warn("got symlink => utf8={}\n", .{out_buffer[0..out_len]});
// TODO handle absolute paths and namespace prefix '/??/'
return out_buffer[0..out_len];
}
/// Same as `readlink` except `file_path` is null-terminated.
pub fn readlinkZ(file_path: [*:0]const u8, out_buffer: []u8) ReadLinkError![]u8 {
if (builtin.os.tag == .windows) {

58
lib/std/os/test.zig
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@ -43,32 +43,42 @@ test "fstatat" {
test "readlink" {
if (builtin.os.tag == .wasi) return error.SkipZigTest;
var cwd = fs.cwd();
try cwd.writeFile("file.txt", "nonsense");
try os.symlink("file.txt", "symlinked");
var tmp = tmpDir(.{});
defer tmp.cleanup();
// create file
try tmp.dir.writeFile("file.txt", "nonsense");
// get paths
// TODO: use Dir's realpath function once that exists
var arena = ArenaAllocator.init(testing.allocator);
defer arena.deinit();
const base_path = blk: {
const relative_path = try fs.path.join(&arena.allocator, &[_][]const u8{ "zig-cache", "tmp", tmp.sub_path[0..]});
break :blk try fs.realpathAlloc(&arena.allocator, relative_path);
};
const target_path = try fs.path.join(&arena.allocator, &[_][]const u8{base_path, "file.txt"});
const symlink_path = try fs.path.join(&arena.allocator, &[_][]const u8{base_path, "symlinked"});
// create symbolic link by path
try os.symlink(target_path, symlink_path);
// now, read the link and verify
var buffer: [fs.MAX_PATH_BYTES]u8 = undefined;
const given = try os.readlink(symlink_path, buffer[0..]);
expect(mem.eql(u8, symlink_path, given));
const given = try os.readlink("symlinked", buffer[0..]);
expect(mem.eql(u8, "file.txt", given));
// var tmp = tmpDir(.{});
// defer tmp.cleanup();
// // create file
// try tmp.dir.writeFile("file.txt", "nonsense");
// // get paths
// // TODO: use Dir's realpath function once that exists
// var arena = ArenaAllocator.init(testing.allocator);
// defer arena.deinit();
// const base_path = blk: {
// const relative_path = try fs.path.join(&arena.allocator, &[_][]const u8{ "zig-cache", "tmp", tmp.sub_path[0..]});
// break :blk try fs.realpathAlloc(&arena.allocator, relative_path);
// };
// const target_path = try fs.path.join(&arena.allocator, &[_][]const u8{base_path, "file.txt"});
// const symlink_path = try fs.path.join(&arena.allocator, &[_][]const u8{base_path, "symlinked"});
// std.debug.warn("\ntarget_path={}\n", .{target_path});
// std.debug.warn("symlink_path={}\n", .{symlink_path});
// // create symbolic link by path
// try os.symlink(target_path, symlink_path);
// // now, read the link and verify
// var buffer: [fs.MAX_PATH_BYTES]u8 = undefined;
// const given = try os.readlink(symlink_path, buffer[0..]);
// expect(mem.eql(u8, symlink_path, given));
}
test "readlinkat" {

70
lib/std/os/windows.zig
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@ -1370,4 +1370,74 @@ pub fn unexpectedStatus(status: NTSTATUS) std.os.UnexpectedError {
std.debug.dumpCurrentStackTrace(null);
}
return error.Unexpected;
}
pub const OpenAsReparsePointError = error {
FileNotFound,
NoDevice,
SharingViolation,
AccessDenied,
PipeBusy,
PathAlreadyExists,
Unexpected,
NameTooLong,
};
/// Open file as a reparse point
pub fn OpenAsReparsePoint(
dir: ?HANDLE,
sub_path_w: [*:0]const u16,
) OpenAsReparsePointError!HANDLE {
const path_len_bytes = math.cast(u16, mem.lenZ(sub_path_w) * 2) catch |err| switch (err) {
error.Overflow => return error.NameTooLong,
};
var nt_name = UNICODE_STRING{
.Length = path_len_bytes,
.MaximumLength = path_len_bytes,
.Buffer = @intToPtr([*]u16, @ptrToInt(sub_path_w)),
};
if (sub_path_w[0] == '.' and sub_path_w[1] == 0) {
// Windows does not recognize this, but it does work with empty string.
nt_name.Length = 0;
}
var attr = OBJECT_ATTRIBUTES{
.Length = @sizeOf(OBJECT_ATTRIBUTES),
.RootDirectory = if (std.fs.path.isAbsoluteWindowsW(sub_path_w)) null else dir,
.Attributes = 0, // Note we do not use OBJ_CASE_INSENSITIVE here.
.ObjectName = &nt_name,
.SecurityDescriptor = null,
.SecurityQualityOfService = null,
};
var io: IO_STATUS_BLOCK = undefined;
var result_handle: HANDLE = undefined;
const rc = ntdll.NtCreateFile(
&result_handle,
FILE_READ_ATTRIBUTES,
&attr,
&io,
null,
FILE_ATTRIBUTE_NORMAL,
FILE_SHARE_READ,
FILE_OPEN,
FILE_OPEN_REPARSE_POINT,
null,
0,
);
switch (rc) {
.SUCCESS => return result_handle,
.OBJECT_NAME_INVALID => unreachable,
.OBJECT_NAME_NOT_FOUND => return error.FileNotFound,
.OBJECT_PATH_NOT_FOUND => return error.FileNotFound,
.NO_MEDIA_IN_DEVICE => return error.NoDevice,
.INVALID_PARAMETER => unreachable,
.SHARING_VIOLATION => return error.SharingViolation,
.ACCESS_DENIED => return error.AccessDenied,
.PIPE_BUSY => return error.PipeBusy,
.OBJECT_PATH_SYNTAX_BAD => unreachable,
.OBJECT_NAME_COLLISION => return error.PathAlreadyExists,
.FILE_IS_A_DIRECTORY => unreachable,
else => return unexpectedStatus(rc),
}
}

2
lib/std/os/windows/bits.zig
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@ -1568,7 +1568,7 @@ pub const MAXIMUM_REPARSE_DATA_BUFFER_SIZE: ULONG = 16 * 1024;
pub const FSCTL_GET_REPARSE_POINT: DWORD = 0x900a8;
pub const IO_REPARSE_TAG_SYMLINK: ULONG = 0xa000000c;
pub const IO_REPARSE_TAG_MOUNT_POINT: ULONG = 0xa0000003;
pub const SYMLINK_FLAG_RELATIVE: ULONG = 0x1;
pub const SYMLINK_FLAG_RELATIVE: ULONG = 0x00000001;
pub const SYMBOLIC_LINK_FLAG_FILE: DWORD = 0x0;
pub const SYMBOLIC_LINK_FLAG_DIRECTORY: DWORD = 0x1;