open: add OpenInRoot and Reopen tests

These are mostly based on the partialOpen tests, but making sure we don't return any partial resolutions. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
cyphar · Jul 11, 2024 · 975d7b3 · 975d7b3
1 parent 1e6990b
commit 975d7b3
Showing 1 changed file with 384 additions and 0 deletions.
diff --git a/open_linux_test.go b/open_linux_test.go
@@ -0,0 +1,384 @@
+//go:build linux
+
+// Copyright (C) 2024 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securejoin
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
+)
+
+type openInRootFunc func(root, unsafePath string) (*os.File, error)
+
+type openResult struct {
+	handlePath string
+	err        error
+	fileType   uint32
+}
+
+// O_LARGEFILE is automatically added by the kernel when opening files on
+// 64-bit machines. Unfortunately, it is architecture-dependent and
+// unix.O_LARGEFILE is 0 (presumably to avoid users setting it). So we need to
+// initialise it at init.
+var O_LARGEFILE = 0x8000
+
+func init() {
+	switch runtime.GOARCH {
+	case "arm", "arm64":
+		O_LARGEFILE = 0x20000
+	case "mips", "mips64", "mips64le", "mips64p32", "mips64p32le":
+		O_LARGEFILE = 0x2000
+	case "ppc", "ppc64", "ppc64le":
+		O_LARGEFILE = 0x10000
+	case "sparc", "sparc64":
+		O_LARGEFILE = 0x40000
+	default:
+		// 0x8000 is the default flag in asm-generic.
+	}
+}
+
+func checkReopen(t *testing.T, handle *os.File, flags int, expectedErr error) {
+	newHandle, err := Reopen(handle, flags)
+	if newHandle != nil {
+		defer newHandle.Close()
+	}
+	if expectedErr != nil {
+		if assert.Error(t, err) {
+			assert.ErrorIs(t, err, expectedErr)
+		} else {
+			t.Errorf("unexpected handle %q", handle.Name())
+		}
+		return
+	}
+	assert.NoError(t, err)
+
+	// Get the original handle path.
+	handlePath, err := procSelfFdReadlink(handle)
+	require.NoError(t, err, "get real path of original handle")
+	// Make sure the handle matches the readlink path.
+	assert.Equal(t, handlePath, handle.Name(), "handle.Name() matching real original handle path")
+
+	// Check that the new and old handle have the same path.
+	newHandlePath, err := procSelfFdReadlink(newHandle)
+	require.NoError(t, err, "get real path of reopened handle")
+	assert.Equal(t, handlePath, newHandlePath, "old and reopen handle paths")
+	assert.Equal(t, handle.Name(), newHandle.Name(), "old and reopen handle.Name()")
+
+	// Check the fd flags.
+	newHandleFdFlags, err := unix.FcntlInt(newHandle.Fd(), unix.F_GETFD, 0)
+	require.NoError(t, err, "fcntl(F_GETFD)")
+	assert.Equal(t, unix.FD_CLOEXEC, newHandleFdFlags&unix.FD_CLOEXEC, "FD_CLOEXEC flag must be set")
+
+	// Check the file handle flags.
+	newHandleStatusFlags, err := unix.FcntlInt(newHandle.Fd(), unix.F_GETFL, 0)
+	require.NoError(t, err, "fcntl(F_GETFL)")
+	flags &^= unix.O_CLOEXEC             // O_CLOEXEC is checked by F_GETFD
+	newHandleStatusFlags &^= O_LARGEFILE // ignore the O_LARGEFILE flag
+	assert.Equal(t, flags, newHandleStatusFlags, "re-opened handle status flags must match re-open flags (%+x)")
+}
+
+func checkOpenInRoot(t *testing.T, openInRootFn openInRootFunc, root, unsafePath string, expected openResult) {
+	handle, err := openInRootFn(root, unsafePath)
+	if handle != nil {
+		defer handle.Close()
+	}
+	if expected.err != nil {
+		if assert.Error(t, err) {
+			assert.ErrorIs(t, err, expected.err)
+		} else {
+			t.Errorf("unexpected handle %q", handle.Name())
+		}
+		return
+	}
+	assert.NoError(t, err)
+
+	// Check the handle path.
+	gotPath, err := procSelfFdReadlink(handle)
+	require.NoError(t, err, "get real path of returned handle")
+	assert.Equal(t, expected.handlePath, gotPath, "real handle path")
+	// Make sure the handle matches the readlink path.
+	assert.Equal(t, gotPath, handle.Name(), "handle.Name() matching real handle path")
+
+	// Check the handle type.
+	unixStat, err := fstat(handle)
+	require.NoError(t, err, "fstat handle")
+	assert.Equal(t, expected.fileType, unixStat.Mode&unix.S_IFMT, "handle S_IFMT type")
+
+	// Check that re-opening produces a handle with the same path.
+	switch expected.fileType {
+	case unix.S_IFDIR:
+		checkReopen(t, handle, unix.O_RDONLY, nil)
+		checkReopen(t, handle, unix.O_DIRECTORY, nil)
+	case unix.S_IFREG:
+		checkReopen(t, handle, unix.O_RDWR, nil)
+		checkReopen(t, handle, unix.O_DIRECTORY, unix.ENOTDIR)
+	// Only files and directories are safe to open this way. Use O_PATH for
+	// everything else.
+	default:
+		checkReopen(t, handle, unix.O_PATH, nil)
+		checkReopen(t, handle, unix.O_PATH|unix.O_DIRECTORY, unix.ENOTDIR)
+	}
+}
+
+func testOpenInRoot(t *testing.T, openInRootFn openInRootFunc) {
+	tree := []string{
+		"dir a",
+		"dir b/c/d/e/f",
+		"file b/c/file",
+		"symlink e /b/c/d/e",
+		"symlink b-file b/c/file",
+		// Dangling symlinks.
+		"symlink a-fake1 a/fake",
+		"symlink a-fake2 a/fake/foo/bar/..",
+		"symlink a-fake3 a/fake/../../b",
+		"dir c",
+		"symlink c/a-fake1 a/fake",
+		"symlink c/a-fake2 a/fake/foo/bar/..",
+		"symlink c/a-fake3 a/fake/../../b",
+		// Test non-lexical symlinks.
+		"dir target",
+		"dir link1",
+		"symlink link1/target_abs /target",
+		"symlink link1/target_rel ../target",
+		"dir link2",
+		"symlink link2/link1_abs /link1",
+		"symlink link2/link1_rel ../link1",
+		"dir link3",
+		"symlink link3/target_abs /link2/link1_rel/target_rel",
+		"symlink link3/target_rel ../link2/link1_rel/target_rel",
+		"symlink link3/deep_dangling1 ../link2/link1_rel/target_rel/nonexist",
+		"symlink link3/deep_dangling2 ../link2/link1_rel/target_rel/nonexist",
+		// Deep dangling symlinks (with single components).
+		"dir dangling",
+		"symlink dangling/a b/c",
+		"dir dangling/b",
+		"symlink dangling/b/c ../c",
+		"symlink dangling/c d/e",
+		"dir dangling/d",
+		"symlink dangling/d/e ../e",
+		"symlink dangling/e f/../g",
+		"dir dangling/f",
+		"symlink dangling/g h/i/j/nonexistent",
+		"dir dangling/h/i/j",
+		// Deep dangling symlink using a non-dir component.
+		"dir dangling-file",
+		"symlink dangling-file/a b/c",
+		"dir dangling-file/b",
+		"symlink dangling-file/b/c ../c",
+		"symlink dangling-file/c d/e",
+		"dir dangling-file/d",
+		"symlink dangling-file/d/e ../e",
+		"symlink dangling-file/e f/../g",
+		"dir dangling-file/f",
+		"symlink dangling-file/g h/i/j/file/foo",
+		"dir dangling-file/h/i/j",
+		"file dangling-file/h/i/j/file",
+		// Some "bad" inodes that a regular user can create.
+		"fifo b/fifo",
+		"sock b/sock",
+		// Symlink loops.
+		"dir loop",
+		"symlink loop/basic-loop1 basic-loop1",
+		"symlink loop/basic-loop2 /loop/basic-loop2",
+		"symlink loop/basic-loop3 ../loop/basic-loop3",
+		"dir loop/a",
+		"symlink loop/a/link ../b/link",
+		"dir loop/b",
+		"symlink loop/b/link /loop/c/link",
+		"dir loop/c",
+		"symlink loop/c/link /loop/d/link",
+		"symlink loop/d e",
+		"dir loop/e",
+		"symlink loop/e/link ../a/link",
+		"symlink loop/link a/link",
+	}
+
+	root := createTree(t, tree...)
+
+	for name, test := range map[string]struct {
+		unsafePath string
+		expected   openResult
+	}{
+		// Complete lookups.
+		"complete-dir1": {"a", openResult{handlePath: "/a", fileType: unix.S_IFDIR}},
+		"complete-dir2": {"b/c/d/e/f", openResult{handlePath: "/b/c/d/e/f", fileType: unix.S_IFDIR}},
+		"complete-fifo": {"b/fifo", openResult{handlePath: "/b/fifo", fileType: unix.S_IFIFO}},
+		"complete-sock": {"b/sock", openResult{handlePath: "/b/sock", fileType: unix.S_IFSOCK}},
+		// Partial lookups.
+		"partial-dir-basic":  {"a/b/c/d/e/f/g/h", openResult{err: unix.ENOENT}},
+		"partial-dir-dotdot": {"a/foo/../bar/baz", openResult{err: unix.ENOENT}},
+		// Complete lookups of non-lexical symlinks.
+		"nonlexical-basic-complete":                 {"target", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-basic-partial":                  {"target/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-basic-partial-dotdot":           {"target/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level1-abs-complete":            {"link1/target_abs", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level1-abs-partial":             {"link1/target_abs/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level1-abs-partial-dotdot":      {"link1/target_abs/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level1-rel-complete":            {"link1/target_rel", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level1-rel-partial":             {"link1/target_rel/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level1-rel-partial-dotdot":      {"link1/target_rel/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-abs-abs-complete":        {"link2/link1_abs/target_abs", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level2-abs-abs-partial":         {"link2/link1_abs/target_abs/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-abs-abs-partial-dotdot":  {"link2/link1_abs/target_abs/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-abs-rel-complete":        {"link2/link1_abs/target_rel", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level2-abs-rel-partial":         {"link2/link1_abs/target_rel/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-abs-rel-partial-dotdot":  {"link2/link1_abs/target_rel/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-abs-open-complete":       {"link2/link1_abs/../target", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level2-abs-open-partial":        {"link2/link1_abs/../target/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-abs-open-partial-dotdot": {"link2/link1_abs/../target/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-rel-abs-complete":        {"link2/link1_rel/target_abs", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level2-rel-abs-partial":         {"link2/link1_rel/target_abs/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-rel-abs-partial-dotdot":  {"link2/link1_rel/target_abs/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-rel-rel-complete":        {"link2/link1_rel/target_rel", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level2-rel-rel-partial":         {"link2/link1_rel/target_rel/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-rel-rel-partial-dotdot":  {"link2/link1_rel/target_rel/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-rel-open-complete":       {"link2/link1_rel/../target", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level2-rel-open-partial":        {"link2/link1_rel/../target/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level2-rel-open-partial-dotdot": {"link2/link1_rel/../target/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level3-abs-complete":            {"link3/target_abs", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level3-abs-partial":             {"link3/target_abs/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level3-abs-partial-dotdot":      {"link3/target_abs/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		"nonlexical-level3-rel-complete":            {"link3/target_rel", openResult{handlePath: "/target", fileType: unix.S_IFDIR}},
+		"nonlexical-level3-rel-partial":             {"link3/target_rel/foo", openResult{err: unix.ENOENT}},
+		"nonlexical-level3-rel-partial-dotdot":      {"link3/target_rel/../target/foo/bar/../baz", openResult{err: unix.ENOENT}},
+		// Partial lookups due to hitting a non-directory.
+		"partial-nondir-dot":             {"b/c/file/.", openResult{err: unix.ENOENT}},
+		"partial-nondir-dotdot1":         {"b/c/file/..", openResult{err: unix.ENOENT}},
+		"partial-nondir-dotdot2":         {"b/c/file/../foo/bar", openResult{err: unix.ENOENT}},
+		"partial-nondir-symlink-dot":     {"b-file/.", openResult{err: unix.ENOENT}},
+		"partial-nondir-symlink-dotdot1": {"b-file/..", openResult{err: unix.ENOENT}},
+		"partial-nondir-symlink-dotdot2": {"b-file/../foo/bar", openResult{err: unix.ENOENT}},
+		"partial-fifo-dot":               {"b/fifo/.", openResult{err: unix.ENOENT}},
+		"partial-fifo-dotdot1":           {"b/fifo/..", openResult{err: unix.ENOENT}},
+		"partial-fifo-dotdot2":           {"b/fifo/../foo/bar", openResult{err: unix.ENOENT}},
+		"partial-sock-dot":               {"b/sock/.", openResult{err: unix.ENOENT}},
+		"partial-sock-dotdot1":           {"b/sock/..", openResult{err: unix.ENOENT}},
+		"partial-sock-dotdot2":           {"b/sock/../foo/bar", openResult{err: unix.ENOENT}},
+		// Dangling symlinks are treated as though they are non-existent.
+		"dangling1-inroot-trailing":       {"a-fake1", openResult{err: unix.ENOENT}},
+		"dangling1-inroot-partial":        {"a-fake1/foo", openResult{err: unix.ENOENT}},
+		"dangling1-inroot-partial-dotdot": {"a-fake1/../bar/baz", openResult{err: unix.ENOENT}},
+		"dangling1-sub-trailing":          {"c/a-fake1", openResult{err: unix.ENOENT}},
+		"dangling1-sub-partial":           {"c/a-fake1/foo", openResult{err: unix.ENOENT}},
+		"dangling1-sub-partial-dotdot":    {"c/a-fake1/../bar/baz", openResult{err: unix.ENOENT}},
+		"dangling2-inroot-trailing":       {"a-fake2", openResult{err: unix.ENOENT}},
+		"dangling2-inroot-partial":        {"a-fake2/foo", openResult{err: unix.ENOENT}},
+		"dangling2-inroot-partial-dotdot": {"a-fake2/../bar/baz", openResult{err: unix.ENOENT}},
+		"dangling2-sub-trailing":          {"c/a-fake2", openResult{err: unix.ENOENT}},
+		"dangling2-sub-partial":           {"c/a-fake2/foo", openResult{err: unix.ENOENT}},
+		"dangling2-sub-partial-dotdot":    {"c/a-fake2/../bar/baz", openResult{err: unix.ENOENT}},
+		"dangling3-inroot-trailing":       {"a-fake3", openResult{err: unix.ENOENT}},
+		"dangling3-inroot-partial":        {"a-fake3/foo", openResult{err: unix.ENOENT}},
+		"dangling3-inroot-partial-dotdot": {"a-fake3/../bar/baz", openResult{err: unix.ENOENT}},
+		"dangling3-sub-trailing":          {"c/a-fake3", openResult{err: unix.ENOENT}},
+		"dangling3-sub-partial":           {"c/a-fake3/foo", openResult{err: unix.ENOENT}},
+		"dangling3-sub-partial-dotdot":    {"c/a-fake3/../bar/baz", openResult{err: unix.ENOENT}},
+		// Tricky dangling symlinks.
+		"dangling-tricky1-trailing":       {"link3/deep_dangling1", openResult{err: unix.ENOENT}},
+		"dangling-tricky1-partial":        {"link3/deep_dangling1/foo", openResult{err: unix.ENOENT}},
+		"dangling-tricky1-partial-dotdot": {"link3/deep_dangling1/..", openResult{err: unix.ENOENT}},
+		"dangling-tricky2-trailing":       {"link3/deep_dangling2", openResult{err: unix.ENOENT}},
+		"dangling-tricky2-partial":        {"link3/deep_dangling2/foo", openResult{err: unix.ENOENT}},
+		"dangling-tricky2-partial-dotdot": {"link3/deep_dangling2/..", openResult{err: unix.ENOENT}},
+		// Really deep dangling links.
+		"deep-dangling1":           {"dangling/a", openResult{err: unix.ENOENT}},
+		"deep-dangling2":           {"dangling/b/c", openResult{err: unix.ENOENT}},
+		"deep-dangling3":           {"dangling/c", openResult{err: unix.ENOENT}},
+		"deep-dangling4":           {"dangling/d/e", openResult{err: unix.ENOENT}},
+		"deep-dangling5":           {"dangling/e", openResult{err: unix.ENOENT}},
+		"deep-dangling6":           {"dangling/g", openResult{err: unix.ENOENT}},
+		"deep-dangling-fileasdir1": {"dangling-file/a", openResult{err: unix.ENOENT}},
+		"deep-dangling-fileasdir2": {"dangling-file/b/c", openResult{err: unix.ENOENT}},
+		"deep-dangling-fileasdir3": {"dangling-file/c", openResult{err: unix.ENOENT}},
+		"deep-dangling-fileasdir4": {"dangling-file/d/e", openResult{err: unix.ENOENT}},
+		"deep-dangling-fileasdir5": {"dangling-file/e", openResult{err: unix.ENOENT}},
+		"deep-dangling-fileasdir6": {"dangling-file/g", openResult{err: unix.ENOENT}},
+		// Symlink loops.
+		"loop":        {"loop/link", openResult{err: unix.ELOOP}},
+		"loop-basic1": {"loop/basic-loop1", openResult{err: unix.ELOOP}},
+		"loop-basic2": {"loop/basic-loop2", openResult{err: unix.ELOOP}},
+		"loop-basic3": {"loop/basic-loop3", openResult{err: unix.ELOOP}},
+	} {
+		test := test // copy iterator
+		// Update the handlePath to be inside our root.
+		if test.expected.handlePath != "" {
+			test.expected.handlePath = filepath.Join(root, test.expected.handlePath)
+		}
+		t.Run(name, func(t *testing.T) {
+			checkOpenInRoot(t, openInRootFn, root, test.unsafePath, test.expected)
+		})
+	}
+}
+
+func TestOpenInRoot(t *testing.T) {
+	withWithoutOpenat2(t, true, func(t *testing.T) {
+		testOpenInRoot(t, OpenInRoot)
+	})
+}
+
+func TestOpenInRootHandle(t *testing.T) {
+	withWithoutOpenat2(t, true, func(t *testing.T) {
+		testOpenInRoot(t, func(root, unsafePath string) (*os.File, error) {
+			rootDir, err := os.OpenFile(root, unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
+			if err != nil {
+				return nil, err
+			}
+			defer rootDir.Close()
+
+			return OpenatInRoot(rootDir, unsafePath)
+		})
+	})
+}
+
+func TestOpenInRoot_BadInode(t *testing.T) {
+	requireRoot(t) // mknod
+
+	withWithoutOpenat2(t, true, func(t *testing.T) {
+		tree := []string{
+			// Make sure we don't open "bad" inodes.
+			"dir foo",
+			"char foo/whiteout 0 0",
+			"block foo/whiteout-blk 0 0",
+		}
+
+		root := createTree(t, tree...)
+
+		rootDir, err := os.OpenFile(root, unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
+		require.NoError(t, err)
+		defer rootDir.Close()
+
+		for name, test := range map[string]struct {
+			unsafePath string
+			expected   openResult
+		}{
+			// Complete lookups.
+			"char-trailing": {"foo/whiteout", openResult{handlePath: "/foo/whiteout", fileType: unix.S_IFCHR}},
+			"blk-trailing":  {"foo/whiteout-blk", openResult{handlePath: "/foo/whiteout-blk", fileType: unix.S_IFBLK}},
+			// Partial lookups due to hitting a non-directory.
+			"char-dot":     {"foo/whiteout/.", openResult{err: unix.ENOENT}},
+			"char-dotdot1": {"foo/whiteout/..", openResult{err: unix.ENOENT}},
+			"char-dotdot2": {"foo/whiteout/../foo/bar", openResult{err: unix.ENOENT}},
+			"blk-dot":      {"foo/whiteout-blk/.", openResult{err: unix.ENOENT}},
+			"blk-dotdot1":  {"foo/whiteout-blk/..", openResult{err: unix.ENOENT}},
+			"blk-dotdot2":  {"foo/whiteout-blk/../foo/bar", openResult{err: unix.ENOENT}},
+		} {
+			test := test // copy iterator
+			// Update the handlePath to be inside our root.
+			if test.expected.handlePath != "" {
+				test.expected.handlePath = filepath.Join(root, test.expected.handlePath)
+			}
+			t.Run(name, func(t *testing.T) {
+				checkOpenInRoot(t, OpenInRoot, root, test.unsafePath, test.expected)
+			})
+		}
+	})
+}