path/filepath: handle ".." in normalizing a path on Windows

Current code assumes there are not ".." in the Clean(path).
That's not true. Clean doesn't handle leading "..", so we need to stop
normalization if we see "..".

Fixes #16793

Change-Id: I0a7901bedac17f1210b134d593ebd9f5e8483775
Reviewed-on: https://go-review.googlesource.com/27410
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

4 files changed, 159 insertions, 8 deletions

diff --git a/src/path/filepath/export_windows_test.go b/src/path/filepath/export_windows_test.go
index 8ca007f70a..a7e2e6422b 100644
--- a/src/path/filepath/export_windows_test.go
+++ b/src/path/filepath/export_windows_test.go
@@ -4,4 +4,7 @@
 
 package filepath
 
-var ToNorm = toNorm
+var (
+	ToNorm   = toNorm
+	NormBase = normBase
+)
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
index 0c495a5f1c..e32922b4cc 100644
--- a/src/path/filepath/path_test.go
+++ b/src/path/filepath/path_test.go
@@ -845,7 +845,7 @@ func TestEvalSymlinks(t *testing.T) {
 		if p, err := filepath.EvalSymlinks(path); err != nil {
 			t.Errorf("EvalSymlinks(%q) error: %v", d.path, err)
 		} else if filepath.Clean(p) != filepath.Clean(dest) {
-			t.Errorf("Clean(%q)=%q, want %q", path, p, dest)
+			t.Errorf("EvalSymlinks(%q)=%q, want %q", path, p, dest)
 		}
 
 		// test EvalSymlinks(".")
@@ -877,6 +877,34 @@ func TestEvalSymlinks(t *testing.T) {
 			t.Errorf(`EvalSymlinks(".") in %q directory returns %q, want "." or %q`, d.path, p, want)
 		}()
 
+		// test EvalSymlinks(".."+path)
+		func() {
+			defer func() {
+				err := os.Chdir(wd)
+				if err != nil {
+					t.Fatal(err)
+				}
+			}()
+
+			err := os.Chdir(simpleJoin(tmpDir, "test"))
+			if err != nil {
+				t.Error(err)
+				return
+			}
+
+			path := simpleJoin("..", d.path)
+			dest := simpleJoin("..", d.dest)
+			if filepath.IsAbs(d.dest) || os.IsPathSeparator(d.dest[0]) {
+				dest = d.dest
+			}
+
+			if p, err := filepath.EvalSymlinks(path); err != nil {
+				t.Errorf("EvalSymlinks(%q) error: %v", d.path, err)
+			} else if filepath.Clean(p) != filepath.Clean(dest) {
+				t.Errorf("EvalSymlinks(%q)=%q, want %q", path, p, dest)
+			}
+		}()
+
 		// test EvalSymlinks where parameter is relative path
 		func() {
 			defer func() {
@@ -894,7 +922,7 @@ func TestEvalSymlinks(t *testing.T) {
 			if p, err := filepath.EvalSymlinks(d.path); err != nil {
 				t.Errorf("EvalSymlinks(%q) error: %v", d.path, err)
 			} else if filepath.Clean(p) != filepath.Clean(d.dest) {
-				t.Errorf("Clean(%q)=%q, want %q", d.path, p, d.dest)
+				t.Errorf("EvalSymlinks(%q)=%q, want %q", d.path, p, d.dest)
 			}
 		}()
 	}
diff --git a/src/path/filepath/path_windows_test.go b/src/path/filepath/path_windows_test.go
index 180c2e90af..2be200cb7d 100644
--- a/src/path/filepath/path_windows_test.go
+++ b/src/path/filepath/path_windows_test.go
@@ -309,9 +309,106 @@ func TestToNorm(t *testing.T) {
 	for _, test := range tests {
 		got, err := filepath.ToNorm(test.arg, stubBase)
 		if err != nil {
-			t.Errorf("unexpected toNorm error, arg: %s, err: %v\n", test.arg, err)
+			t.Errorf("toNorm(%s) failed: %v\n", test.arg, err)
 		} else if got != test.want {
-			t.Errorf("toNorm error, arg: %s, want: %s, got: %s\n", test.arg, test.want, got)
+			t.Errorf("toNorm(%s) returns %s, but %s expected\n", test.arg, got, test.want)
+		}
+	}
+
+	testPath := `{{tmp}}\test\foo\bar`
+
+	testsDir := []struct {
+		wd   string
+		arg  string
+		want string
+	}{
+		// test absolute paths
+		{".", `{{tmp}}\test\foo\bar`, `{{tmp}}\test\foo\bar`},
+		{".", `{{tmp}}\.\test/foo\bar`, `{{tmp}}\test\foo\bar`},
+		{".", `{{tmp}}\test\..\test\foo\bar`, `{{tmp}}\test\foo\bar`},
+		{".", `{{tmp}}\TEST\FOO\BAR`, `{{tmp}}\test\foo\bar`},
+
+		// test relative paths begin with drive letter
+		{`{{tmp}}\test`, `{{tmpvol}}.`, `{{tmpvol}}.`},
+		{`{{tmp}}\test`, `{{tmpvol}}..`, `{{tmpvol}}..`},
+		{`{{tmp}}\test`, `{{tmpvol}}foo\bar`, `{{tmpvol}}foo\bar`},
+		{`{{tmp}}\test`, `{{tmpvol}}.\foo\bar`, `{{tmpvol}}foo\bar`},
+		{`{{tmp}}\test`, `{{tmpvol}}foo\..\foo\bar`, `{{tmpvol}}foo\bar`},
+		{`{{tmp}}\test`, `{{tmpvol}}FOO\BAR`, `{{tmpvol}}foo\bar`},
+
+		// test relative paths begin with '\'
+		{".", `{{tmpnovol}}\test\foo\bar`, `{{tmpnovol}}\test\foo\bar`},
+		{".", `{{tmpnovol}}\.\test\foo\bar`, `{{tmpnovol}}\test\foo\bar`},
+		{".", `{{tmpnovol}}\test\..\test\foo\bar`, `{{tmpnovol}}\test\foo\bar`},
+		{".", `{{tmpnovol}}\TEST\FOO\BAR`, `{{tmpnovol}}\test\foo\bar`},
+
+		// test relative paths begin without '\'
+		{`{{tmp}}\test`, ".", `.`},
+		{`{{tmp}}\test`, "..", `..`},
+		{`{{tmp}}\test`, `foo\bar`, `foo\bar`},
+		{`{{tmp}}\test`, `.\foo\bar`, `foo\bar`},
+		{`{{tmp}}\test`, `foo\..\foo\bar`, `foo\bar`},
+		{`{{tmp}}\test`, `FOO\BAR`, `foo\bar`},
+	}
+
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		err := os.Chdir(cwd)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	tmp, err := ioutil.TempDir("", "testToNorm")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmp)
+
+	// ioutil.TempDir might return "non-canonical" name.
+	tmp, err = filepath.EvalSymlinks(tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = os.MkdirAll(strings.Replace(testPath, "{{tmp}}", tmp, -1), 0777)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tmpVol := filepath.VolumeName(tmp)
+	tmpNoVol := tmp[len(tmpVol):]
+
+	for _, test := range testsDir {
+		wd := strings.Replace(strings.Replace(strings.Replace(test.wd, "{{tmp}}", tmp, -1), "{{tmpvol}}", tmpVol, -1), "{{tmpnovol}}", tmpNoVol, -1)
+		arg := strings.Replace(strings.Replace(strings.Replace(test.arg, "{{tmp}}", tmp, -1), "{{tmpvol}}", tmpVol, -1), "{{tmpnovol}}", tmpNoVol, -1)
+		want := strings.Replace(strings.Replace(strings.Replace(test.want, "{{tmp}}", tmp, -1), "{{tmpvol}}", tmpVol, -1), "{{tmpnovol}}", tmpNoVol, -1)
+
+		if test.wd == "." {
+			err := os.Chdir(cwd)
+			if err != nil {
+				t.Error(err)
+
+				continue
+			}
+		} else {
+			err := os.Chdir(wd)
+			if err != nil {
+				t.Error(err)
+
+				continue
+			}
+		}
+
+		got, err := filepath.ToNorm(arg, filepath.NormBase)
+		if err != nil {
+			t.Errorf("toNorm(%s) failed: %v (wd=%s)\n", arg, err, wd)
+		} else if got != want {
+			t.Errorf("toNorm(%s) returns %s, but %s expected (wd=%s)\n", arg, got, want, wd)
 		}
 	}
 }
diff --git a/src/path/filepath/symlink_windows.go b/src/path/filepath/symlink_windows.go
index 243352819e..bb05aabc92 100644
--- a/src/path/filepath/symlink_windows.go
+++ b/src/path/filepath/symlink_windows.go
@@ -22,7 +22,7 @@ func normVolumeName(path string) string {
 	return strings.ToUpper(volume)
 }
 
-// normBase retruns the last element of path.
+// normBase returns the last element of path with correct case.
 func normBase(path string) (string, error) {
 	p, err := syscall.UTF16PtrFromString(path)
 	if err != nil {
@@ -40,7 +40,24 @@ func normBase(path string) (string, error) {
 	return syscall.UTF16ToString(data.FileName[:]), nil
 }
 
-func toNorm(path string, base func(string) (string, error)) (string, error) {
+// baseIsDotDot returns whether the last element of path is "..".
+// The given path should be 'Clean'-ed in advance.
+func baseIsDotDot(path string) bool {
+	i := strings.LastIndexByte(path, Separator)
+	return path[i+1:] == ".."
+}
+
+// toNorm returns the normalized path that is guranteed to be unique.
+// It should accept the following formats:
+//   * UNC paths                              (e.g \\server\share\foo\bar)
+//   * absolute paths                         (e.g C:\foo\bar)
+//   * relative paths begin with drive letter (e.g C:foo\bar, C:..\foo\bar, C:.., C:.)
+//   * relative paths begin with '\'          (e.g \foo\bar)
+//   * relative paths begin without '\'       (e.g foo\bar, ..\foo\bar, .., .)
+// The returned normalized path will be in the same form (of 5 listed above) as the input path.
+// If two paths A and B are indicating the same file with the same format, toNorm(A) should be equal to toNorm(B).
+// The normBase parameter should be equal to the normBase func, except for in tests.  See docs on the normBase func.
+func toNorm(path string, normBase func(string) (string, error)) (string, error) {
 	if path == "" {
 		return path, nil
 	}
@@ -58,7 +75,13 @@ func toNorm(path string, base func(string) (string, error)) (string, error) {
 	var normPath string
 
 	for {
-		name, err := base(volume + path)
+		if baseIsDotDot(path) {
+			normPath = path + `\` + normPath
+
+			break
+		}
+
+		name, err := normBase(volume + path)
 		if err != nil {
 			return "", err
 		}