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fix path traversal issue in extract_entry #1

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fix path traversal issue in extract_entry #1

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28 changes: 23 additions & 5 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ import (
"rsc.io/getopt"
"strconv"
"strings"
securejoin "github.com/cyphar/filepath-securejoin"
)

var (
Expand Down Expand Up @@ -226,7 +227,14 @@ func extract_entry(areader *zip.ReadCloser, file *zip.FileHeader) {
var err error
var dest_path string
var dest *os.File


// Make base destination absolute (stable even with sudo)
baseDest, err := filepath.Abs(destdir)
if err != nil {
fmt.Fprintf(os.Stderr, "bad destdir %q: %v\n", destdir, err)
os.Exit(1)
}

/* Business as usual. */
if fVerbose && !fJSON {
fmt.Printf("x %s ", file.Name)
Expand All @@ -245,13 +253,23 @@ func extract_entry(areader *zip.ReadCloser, file *zip.FileHeader) {
* For some reason, this is an option that has been requisited
* per users of Info-ZIP's unzip command for some years, so we
* will be having it implemented here as well. */
if !fExplode { /* Default. */
dest_path = filepath.Join(destdir, file.Name)
} else {
dest_path = filepath.Join(destdir, filepath.Base(file.Name))

entryName := file.Name
if fExplode {
entryName = filepath.Base(file.Name)
}

entryName = filepath.ToSlash(entryName)
entryName = strings.TrimLeft(entryName, "/")

dest_path, err = securejoin.SecureJoin(baseDest, entryName)
if err != nil {
fmt.Fprintf(os.Stderr, "path traversal blocked: entry=%q: %v\n", file.Name, err)
os.Exit(1) // or: return (to skip)
}

if file.FileInfo().IsDir() && !fExplode {

err = os.MkdirAll(dest_path, file.Mode())
if fVerbose && !fJSON {
fmt.Println("directory")
Expand Down