io/ioutil: reject path separators in TempDir, TempFile pattern

Fixes #33920

Change-Id: I2351a1caa80c086ff5a8e02aad70d996be7aac35
Reviewed-on: https://go-review.googlesource.com/c/go/+/212597
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/io/ioutil/tempfile.go

@@ -5,6 +5,7 @@
 package ioutil
 
 import (
+	"errors"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -52,7 +53,10 @@ func TempFile(dir, pattern string) (f *os.File, err error) {
 		dir = os.TempDir()
 	}
 
-	prefix, suffix := prefixAndSuffix(pattern)
+	prefix, suffix, err := prefixAndSuffix(pattern)
+	if err != nil {
+		return
+	}
 
 	nconflict := 0
 	for i := 0; i < 10000; i++ {
@@ -71,9 +75,15 @@ func TempFile(dir, pattern string) (f *os.File, err error) {
 	return
 }
 
+var errPatternHasSeparator = errors.New("pattern contains path separator")
+
 // prefixAndSuffix splits pattern by the last wildcard "*", if applicable,
 // returning prefix as the part before "*" and suffix as the part after "*".
-func prefixAndSuffix(pattern string) (prefix, suffix string) {
+func prefixAndSuffix(pattern string) (prefix, suffix string, err error) {
+	if strings.ContainsRune(pattern, os.PathSeparator) {
+		err = errPatternHasSeparator
+		return
+	}
 	if pos := strings.LastIndex(pattern, "*"); pos != -1 {
 		prefix, suffix = pattern[:pos], pattern[pos+1:]
 	} else {
@@ -96,7 +106,10 @@ func TempDir(dir, pattern string) (name string, err error) {
 		dir = os.TempDir()
 	}
 
-	prefix, suffix := prefixAndSuffix(pattern)
+	prefix, suffix, err := prefixAndSuffix(pattern)
+	if err != nil {
+		return
+	}
 
 	nconflict := 0
 	for i := 0; i < 10000; i++ {

src/io/ioutil/tempfile_test.go

@@ -48,6 +48,48 @@ func TestTempFile_pattern(t *testing.T) {
 	}
 }
 
+func TestTempFile_BadPattern(t *testing.T) {
+	tmpDir, err := TempDir("", t.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	const sep = string(os.PathSeparator)
+	tests := []struct {
+		pattern string
+		wantErr bool
+	} {
+		{"ioutil*test", false},
+		{"ioutil_test*foo", false},
+		{"ioutil_test" + sep + "foo", true},
+		{"ioutil_test*" + sep + "foo", true},
+		{"ioutil_test" + sep + "*foo", true},
+		{sep + "ioutil_test" + sep + "*foo", true},
+		{"ioutil_test*foo" + sep, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.pattern, func(t *testing.T) {
+			tmpfile, err := TempFile(tmpDir, tt.pattern)
+			defer func() {
+				if tmpfile != nil {
+					tmpfile.Close()
+				}
+			}()
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("Expected an error for pattern %q", tt.pattern)
+				}
+				if g, w := err, errPatternHasSeparator; g != w {
+					t.Errorf("Error mismatch: got %#v, want %#v for pattern %q", g, w, tt.pattern)
+				}
+			} else if err != nil {
+				t.Errorf("Unexpected error %v for pattern %q", err, tt.pattern)
+			}
+		})
+	}
+}
+
 func TestTempDir(t *testing.T) {
 	name, err := TempDir("/_not_exists_", "foo")
 	if name != "" || err == nil {
@@ -112,3 +154,40 @@ func TestTempDir_BadDir(t *testing.T) {
 		t.Errorf("TempDir error = %#v; want PathError for path %q satisifying os.IsNotExist", err, badDir)
 	}
 }
+
+func TestTempDir_BadPattern(t *testing.T) {
+	tmpDir, err := TempDir("", t.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	const sep = string(os.PathSeparator)
+	tests := []struct {
+		pattern string
+		wantErr bool
+	} {
+		{"ioutil*test", false},
+		{"ioutil_test*foo", false},
+		{"ioutil_test" + sep + "foo", true},
+		{"ioutil_test*" + sep + "foo", true},
+		{"ioutil_test" + sep + "*foo", true},
+		{sep + "ioutil_test" + sep + "*foo", true},
+		{"ioutil_test*foo" + sep, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.pattern, func(t *testing.T) {
+			_, err := TempDir(tmpDir, tt.pattern)
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("Expected an error for pattern %q", tt.pattern)
+				}
+				if g, w := err, errPatternHasSeparator; g != w {
+					t.Errorf("Error mismatch: got %#v, want %#v for pattern %q", g, w, tt.pattern)
+				}
+			} else if err != nil {
+				t.Errorf("Unexpected error %v for pattern %q", err, tt.pattern)
+			}
+		})
+	}
+}

src/os/os_test.go

@@ -1785,7 +1785,7 @@ func TestAppend(t *testing.T) {
 
 func TestStatDirWithTrailingSlash(t *testing.T) {
 	// Create new temporary directory and arrange to clean it up.
-	path, err := ioutil.TempDir("", "/_TestStatDirWithSlash_")
+	path, err := ioutil.TempDir("", "_TestStatDirWithSlash_")
 	if err != nil {
 		t.Fatalf("TempDir: %s", err)
 	}