osfs: Expand dot on BoundOS

Signed-off-by: Paulo Gomes <[email protected]>

Author: pjbgf

osfs/os_bound.go

@@ -20,6 +20,7 @@
 package osfs
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -29,6 +30,11 @@ import (
 	"github.com/go-git/go-billy/v5"
 )
 
+var (
+	ErrBaseDirCannotBeRemoved = errors.New("base dir cannot be removed")
+	ErrBaseDirCannotBeRenamed = errors.New("base dir cannot be renamed")
+)
+
 // BoundOS is a fs implementation based on the OS filesystem which is bound to
 // a base dir.
 // Prefer this fs implementation over ChrootOS.
@@ -54,6 +60,7 @@ func (fs *BoundOS) Create(filename string) (billy.File, error) {
 }
 
 func (fs *BoundOS) OpenFile(filename string, flag int, perm os.FileMode) (billy.File, error) {
+	filename = fs.expandDot(filename)
 	fn, err := fs.abs(filename)
 	if err != nil {
 		return nil, err
@@ -62,6 +69,7 @@ func (fs *BoundOS) OpenFile(filename string, flag int, perm os.FileMode) (billy.
 }
 
 func (fs *BoundOS) ReadDir(path string) ([]os.FileInfo, error) {
+	path = fs.expandDot(path)
 	dir, err := fs.abs(path)
 	if err != nil {
 		return nil, err
@@ -71,6 +79,12 @@ func (fs *BoundOS) ReadDir(path string) ([]os.FileInfo, error) {
 }
 
 func (fs *BoundOS) Rename(from, to string) error {
+	if from == "." || from == fs.baseDir {
+		return ErrBaseDirCannotBeRenamed
+	}
+
+	from = fs.expandDot(from)
+	to = fs.expandDot(to)
 	f, err := fs.abs(from)
 	if err != nil {
 		return err
@@ -89,6 +103,7 @@ func (fs *BoundOS) Rename(from, to string) error {
 }
 
 func (fs *BoundOS) MkdirAll(path string, perm os.FileMode) error {
+	path = fs.expandDot(path)
 	dir, err := fs.abs(path)
 	if err != nil {
 		return err
@@ -97,10 +112,12 @@ func (fs *BoundOS) MkdirAll(path string, perm os.FileMode) error {
 }
 
 func (fs *BoundOS) Open(filename string) (billy.File, error) {
+	filename = fs.expandDot(filename)
 	return fs.OpenFile(filename, os.O_RDONLY, 0)
 }
 
 func (fs *BoundOS) Stat(filename string) (os.FileInfo, error) {
+	filename = fs.expandDot(filename)
 	filename, err := fs.abs(filename)
 	if err != nil {
 		return nil, err
@@ -109,6 +126,10 @@ func (fs *BoundOS) Stat(filename string) (os.FileInfo, error) {
 }
 
 func (fs *BoundOS) Remove(filename string) error {
+	if filename == "." || filename == fs.baseDir {
+		return ErrBaseDirCannotBeRemoved
+	}
+
 	fn, err := fs.abs(filename)
 	if err != nil {
 		return err
@@ -136,6 +157,11 @@ func (fs *BoundOS) Join(elem ...string) string {
 }
 
 func (fs *BoundOS) RemoveAll(path string) error {
+	if path == "." || path == fs.baseDir {
+		return ErrBaseDirCannotBeRemoved
+	}
+
+	path = fs.expandDot(path)
 	dir, err := fs.abs(path)
 	if err != nil {
 		return err
@@ -144,6 +170,7 @@ func (fs *BoundOS) RemoveAll(path string) error {
 }
 
 func (fs *BoundOS) Symlink(target, link string) error {
+	link = fs.expandDot(link)
 	ln, err := fs.abs(link)
 	if err != nil {
 		return err
@@ -155,7 +182,20 @@ func (fs *BoundOS) Symlink(target, link string) error {
 	return os.Symlink(target, ln)
 }
 
+func (fs *BoundOS) expandDot(p string) string {
+	if p == "." {
+		return fs.baseDir
+	}
+	for _, prefix := range []string{"./", ".\\"} {
+		if strings.HasPrefix(p, prefix) {
+			return filepath.Join(fs.baseDir, strings.TrimPrefix(p, prefix))
+		}
+	}
+	return p
+}
+
 func (fs *BoundOS) Lstat(filename string) (os.FileInfo, error) {
+	filename = fs.expandDot(filename)
 	filename = filepath.Clean(filename)
 	if !filepath.IsAbs(filename) {
 		filename = filepath.Join(fs.baseDir, filename)
@@ -167,6 +207,7 @@ func (fs *BoundOS) Lstat(filename string) (os.FileInfo, error) {
 }
 
 func (fs *BoundOS) Readlink(link string) (string, error) {
+	link = fs.expandDot(link)
 	if !filepath.IsAbs(link) {
 		link = filepath.Clean(filepath.Join(fs.baseDir, link))
 	}
@@ -247,7 +288,7 @@ func (fs *BoundOS) insideBaseDir(filename string) (bool, error) {
 // that either filename or fs.baseDir may contain.
 func (fs *BoundOS) insideBaseDirEval(filename string) (bool, error) {
 	// "/" contains all others.
-	if fs.baseDir == "/" {
+	if fs.baseDir == "/" || fs.baseDir == filename {
 		return true, nil
 	}
 	dir, err := filepath.EvalSymlinks(filepath.Dir(filename))

osfs/os_bound_test.go

@@ -47,6 +47,14 @@ func TestOpen(t *testing.T) {
 			},
 			filename: "test-file",
 		},
+		{
+			name: "file: dot rel same dir",
+			before: func(dir string) billy.Filesystem {
+				os.WriteFile(filepath.Join(dir, "test-file"), []byte("anything"), 0o600)
+				return newBoundOS(dir, true)
+			},
+			filename: "./test-file",
+		},
 		{
 			name: "file: rel path to above cwd",
 			before: func(dir string) billy.Filesystem {
@@ -160,6 +168,11 @@ func Test_Symlink(t *testing.T) {
 			link:   "symlink",
 			target: filepath.FromSlash("/etc/passwd"),
 		},
+		{
+			name:   "dot link to abs valid target",
+			link:   "./symlink",
+			target: filepath.FromSlash("/etc/passwd"),
+		},
 		{
 			name:   "link to abs inexistent target",
 			link:   "symlink",
@@ -507,6 +520,14 @@ func TestLstat(t *testing.T) {
 			},
 			filename: "test-file",
 		},
+		{
+			name: "file: dot rel",
+			before: func(dir string) billy.Filesystem {
+				os.WriteFile(filepath.Join(dir, "test-file"), []byte("anything"), 0o600)
+				return newBoundOS(dir, true)
+			},
+			filename: "./test-file",
+		},
 		{
 			name: "file: abs",
 			before: func(dir string) billy.Filesystem {
@@ -610,6 +631,13 @@ func TestStat(t *testing.T) {
 			},
 			filename: "test-file",
 		},
+		{
+			name: "rel dot dir",
+			before: func(dir string) billy.Filesystem {
+				return newBoundOS(dir, true)
+			},
+			filename: ".",
+		},
 		{
 			name: "abs file",
 			before: func(dir string) billy.Filesystem {
@@ -674,6 +702,14 @@ func TestRemove(t *testing.T) {
 			filename: "inexistent",
 			wantErr:  notFoundError(),
 		},
+		{
+			name: "same dot dir",
+			before: func(dir string) billy.Filesystem {
+				return newBoundOS(dir, true)
+			},
+			filename: ".",
+			wantErr:  "base dir cannot be removed",
+		},
 		{
 			name: "same dir file",
 			before: func(dir string) billy.Filesystem {
@@ -1105,10 +1141,10 @@ func TestReadDir(t *testing.T) {
 	g.Expect(dirs).To(gomega.BeNil())
 }
 
-func TestInsideBaseDirEval(t*testing.T) {
+func TestInsideBaseDirEval(t *testing.T) {
 	g := gomega.NewWithT(t)
 	fs := BoundOS{baseDir: "/"}
-	b, err :=  fs.insideBaseDirEval("a")
+	b, err := fs.insideBaseDirEval("a")
 	g.Expect(b).To(gomega.BeTrue())
 	g.Expect(err).To(gomega.BeNil())
 }