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package fs
import (
"fmt"
"os"
"path/filepath"
)
// ValidatedReadTarget stores a resolved regular file path for rooted re-opens.
type ValidatedReadTarget struct {
resolvedPath string
rootedPath RootedPath
}
// NewValidatedReadTarget returns a rooted target for a resolved regular file.
func NewValidatedReadTarget(resolvedPath string) (ValidatedReadTarget, error) {
cleanedPath := filepath.Clean(resolvedPath)
if !filepath.IsAbs(cleanedPath) {
return ValidatedReadTarget{}, fmt.Errorf("validated read target requires absolute path: %s", cleanedPath)
}
info, err := os.Lstat(cleanedPath)
if err != nil {
return ValidatedReadTarget{}, fmt.Errorf("lstat validated read target %s: %w", cleanedPath, err)
}
if !info.Mode().IsRegular() {
return ValidatedReadTarget{}, fmt.Errorf("validated read target must be a regular file: %s", cleanedPath)
}
rootedPath, err := NewRootedPath(cleanedPath)
if err != nil {
return ValidatedReadTarget{}, err
}
return ValidatedReadTarget{
resolvedPath: cleanedPath,
rootedPath: rootedPath,
}, nil
}
// Open re-opens the validated file beneath its resolved parent directory.
func (t ValidatedReadTarget) Open() (*os.File, error) {
root, err := t.rootedPath.OpenRoot()
if err != nil {
return nil, fmt.Errorf("open root for %s: %w", t.resolvedPath, err)
}
defer root.Close()
if err := t.validateEntry(root); err != nil {
return nil, err
}
fd, err := root.Open(t.rootedPath.Name())
if err != nil {
return nil, fmt.Errorf("open rooted file %s: %w", t.resolvedPath, err)
}
if err := validateOpenedFile(fd, t.resolvedPath); err != nil {
fd.Close()
return nil, err
}
if err := t.validateEntry(root); err != nil {
fd.Close()
return nil, err
}
return fd, nil
}
func (t ValidatedReadTarget) validateEntry(root *os.Root) error {
info, err := root.Lstat(t.rootedPath.Name())
if err != nil {
return fmt.Errorf("lstat rooted file %s: %w", t.resolvedPath, err)
}
if info.Mode()&os.ModeSymlink != 0 {
return fmt.Errorf("rooted file changed to symlink: %s", t.resolvedPath)
}
if !info.Mode().IsRegular() {
return fmt.Errorf("rooted file changed to non-regular file: %s", t.resolvedPath)
}
return nil
}
func validateOpenedFile(fd *os.File, resolvedPath string) error {
info, err := fd.Stat()
if err != nil {
return fmt.Errorf("stat opened file %s: %w", resolvedPath, err)
}
if !info.Mode().IsRegular() {
return fmt.Errorf("opened file is not regular: %s", resolvedPath)
}
return nil
}
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