validation: Use non-empty files in masked/readonly tests

Previously we were only looking at directories.  But the spec does not
say these are directory-only options, so test files too.  Put some
content in the files, because runtimetest currently has no way to
check the readability of empty files.

Signed-off-by: W. Trevor King <wking@tremily.us>

Author: wking

cmd/runtimetest/main.go

@@ -426,6 +426,9 @@ func testFileReadAccess(path string) (readable bool, err error) {
 	if err == nil {
 		return true, nil
 	} else if err == io.EOF {
+		// Our validation/ tests only use non-empty files for read-access
+		// tests. So if we get an EOF on the first read, the runtime did
+		// successfully block readability.
 		return false, nil
 	}
 	return false, err

validation/linux_masked_paths.go

@@ -9,10 +9,28 @@ import (
 
 func main() {
 	g := util.GetDefaultGenerator()
-	g.AddLinuxMaskedPaths("/masktest")
+	g.AddLinuxMaskedPaths("/masked-dir")
+	g.AddLinuxMaskedPaths("/masked-file")
 	err := util.RuntimeInsideValidate(g, func(path string) error {
-		pathName := filepath.Join(path, "masktest")
-		return os.MkdirAll(pathName, 0700)
+		testDir := filepath.Join(path, "masked-dir")
+		err := os.MkdirAll(testDir, 0777)
+		if err != nil {
+			return err
+		}
+
+		testFile := filepath.Join(path, "masked-file")
+		f, err := os.OpenFile(testFile, os.O_WRONLY|os.O_CREAT, 0777)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		// runtimetest cannot check the readability of empty files, so
+		// write something.
+		_, err = f.Write([]byte("secrets"))
+		if err != nil {
+			return err
+		}
 	})
 	if err != nil {
 		util.Fatal(err)

validation/linux_readonly_paths.go

@@ -9,10 +9,28 @@ import (
 
 func main() {
 	g := util.GetDefaultGenerator()
-	g.AddLinuxReadonlyPaths("readonlytest")
+	g.AddLinuxReadonlyPaths("/readonly-dir")
+	g.AddLinuxReadonlyPaths("/readonly-file")
 	err := util.RuntimeInsideValidate(g, func(path string) error {
-		pathName := filepath.Join(path, "readonlytest")
-		return os.MkdirAll(pathName, 0700)
+		testDir := filepath.Join(path, "readonly-dir")
+		err := os.MkdirAll(testDir, 0777)
+		if err != nil {
+			return err
+		}
+
+		testFile := filepath.Join(path, "readonly-file")
+		f, err := os.OpenFile(testFile, os.O_WRONLY|os.O_CREAT, 0777)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		// runtimetest cannot check the readability of empty files, so
+		// write something.
+		_, err = f.Write([]byte("secrets"))
+		if err != nil {
+			return err
+		}
 	})
 	if err != nil {
 		util.Fatal(err)