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symwalk.go
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symwalk.go
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package template
import (
"fmt"
"os"
"path/filepath"
"strings"
)
// Walk extends filepath.Walk to also follow symlinks. The scope should be within the boundary.
func Walk(path, boundary string, followSymlink bool, walkFn filepath.WalkFunc) error {
boundary, err := filepath.Abs(boundary)
if err != nil {
return err
}
return walk(path, path, boundary, followSymlink, walkFn)
}
func walk(filename, linkDirname, boundary string, followSymlink bool, walkFn filepath.WalkFunc) error {
if !followSymlink {
return filepath.Walk(filename, walkFn)
}
followSymlinkWalkFunc := func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if rel, err := filepath.Rel(filename, path); err == nil {
path = filepath.Join(linkDirname, rel)
} else {
return err
}
if isSymlink(info) {
finalPath, err := filepath.EvalSymlinks(path)
if err != nil {
return err
}
// the boundary could be a symbolic link
boundaryPath, err := filepath.EvalSymlinks(boundary)
if err != nil {
return err
}
within, err := withinBoundary(finalPath, boundaryPath)
if err != nil {
return err
}
if !within {
return nil
}
info, err := os.Lstat(finalPath)
if err != nil {
return walkFn(path, info, err)
}
if info.IsDir() {
return walk(finalPath, path, boundary, followSymlink, walkFn)
}
}
return walkFn(path, info, err)
}
return filepath.Walk(filename, followSymlinkWalkFunc)
}
func isSymlink(info os.FileInfo) bool {
return info.Mode()&os.ModeSymlink == os.ModeSymlink
}
func withinBoundary(path, boundary string) (bool, error) {
path, err := filepath.Abs(path)
if err != nil {
return false, fmt.Errorf("failed to get absolute path: %v", err)
}
rel, err := filepath.Rel(boundary, path)
if err != nil {
return false, fmt.Errorf("failed to check boundary: %v", err)
}
if !strings.HasPrefix(rel, "..") {
return true, nil
}
return false, nil
}