chore: go mod tidy / vendor / make deps

vendor/github.com/cyphar/filepath-securejoin/pathrs-lite/openat2_linux.go

@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build linux
+
+// Copyright (C) 2024-2025 Aleksa Sarai <cyphar@cyphar.com>
+// Copyright (C) 2024-2025 SUSE LLC
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package pathrs
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/cyphar/filepath-securejoin/pathrs-lite/internal/fd"
+	"github.com/cyphar/filepath-securejoin/pathrs-lite/procfs"
+)
+
+func openat2(dir fd.Fd, path string, how *unix.OpenHow) (*os.File, error) {
+	file, err := fd.Openat2(dir, path, how)
+	if err != nil {
+		return nil, err
+	}
+	// If we are using RESOLVE_IN_ROOT, the name we generated may be wrong.
+	if how.Resolve&unix.RESOLVE_IN_ROOT == unix.RESOLVE_IN_ROOT {
+		if actualPath, err := procfs.ProcSelfFdReadlink(file); err == nil {
+			// TODO: Ideally we would not need to dup the fd, but you cannot
+			//       easily just swap an *os.File with one from the same fd
+			//       (the GC will close the old one, and you cannot clear the
+			//       finaliser easily because it is associated with an internal
+			//       field of *os.File not *os.File itself).
+			newFile, err := fd.DupWithName(file, actualPath)
+			if err != nil {
+				return nil, err
+			}
+			file = newFile
+		}
+	}
+	return file, nil
+}
+
+func lookupOpenat2(root fd.Fd, unsafePath string, partial bool) (*os.File, string, error) {
+	if !partial {
+		file, err := openat2(root, unsafePath, &unix.OpenHow{
+			Flags:   unix.O_PATH | unix.O_CLOEXEC,
+			Resolve: unix.RESOLVE_IN_ROOT | unix.RESOLVE_NO_MAGICLINKS,
+		})
+		return file, "", err
+	}
+	return partialLookupOpenat2(root, unsafePath)
+}
+
+// partialLookupOpenat2 is an alternative implementation of
+// partialLookupInRoot, using openat2(RESOLVE_IN_ROOT) to more safely get a
+// handle to the deepest existing child of the requested path within the root.
+func partialLookupOpenat2(root fd.Fd, unsafePath string) (*os.File, string, error) {
+	// TODO: Implement this as a git-bisect-like binary search.
+
+	unsafePath = filepath.ToSlash(unsafePath) // noop
+	endIdx := len(unsafePath)
+	var lastError error
+	for endIdx > 0 {
+		subpath := unsafePath[:endIdx]
+
+		handle, err := openat2(root, subpath, &unix.OpenHow{
+			Flags:   unix.O_PATH | unix.O_CLOEXEC,
+			Resolve: unix.RESOLVE_IN_ROOT | unix.RESOLVE_NO_MAGICLINKS,
+		})
+		if err == nil {
+			// Jump over the slash if we have a non-"" remainingPath.
+			if endIdx < len(unsafePath) {
+				endIdx++
+			}
+			// We found a subpath!
+			return handle, unsafePath[endIdx:], lastError
+		}
+		if errors.Is(err, unix.ENOENT) || errors.Is(err, unix.ENOTDIR) {
+			// That path doesn't exist, let's try the next directory up.
+			endIdx = strings.LastIndexByte(subpath, '/')
+			lastError = err
+			continue
+		}
+		return nil, "", fmt.Errorf("open subpath: %w", err)
+	}
+	// If we couldn't open anything, the whole subpath is missing. Return a
+	// copy of the root fd so that the caller doesn't close this one by
+	// accident.
+	rootClone, err := fd.Dup(root)
+	if err != nil {
+		return nil, "", err
+	}
+	return rootClone, unsafePath, lastError
+}