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archive/zip: cap out of range #10956

dvyukov opened this issue May 26, 2015 · 1 comment

archive/zip: cap out of range #10956

dvyukov opened this issue May 26, 2015 · 1 comment


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@dvyukov dvyukov commented May 26, 2015

The following program crashes with a panic:

package main

import (

func main() {
    data := []byte("PK\x06\x06PK\x06\a0000\x00\x00\x00\x00\x00\x00\x00\x00" +
        "0000PK\x05\x06000000000000" +
    z, err := zip.NewReader(bytes.NewReader(data), int64(len(data)))
    if err != nil {
        if z != nil {
            panic("non nil z")
    for _, f := range z.File {
        r, err := f.Open()
        if err != nil {
        if f.UncompressedSize64 < 1e6 {
            n, err := io.Copy(ioutil.Discard, r)
            if err == nil && uint64(n) != f.UncompressedSize64 {
                println("bad size:", n, f.UncompressedSize64)
                panic("bad size")
panic: runtime error: makeslice: cap out of range

goroutine 1 [running]:
archive/zip.(*Reader).init(0xc2080104c0, 0x7fbacc72d1e8, 0xc208014450, 0x39, 0x0, 0x0)
    src/archive/zip/reader.go:81 +0xf7
archive/zip.NewReader(0x7fbacc72d1e8, 0xc208014450, 0x39, 0x7fbacc72d1e8, 0x0, 0x0)
    src/archive/zip/reader.go:69 +0x67
    zip.go:14 +0x131

This vulnerability makes it dangerous to open any untrusted zip files. I think that the code must check that the provided data size is large enough to contain the claimed number of files. For example, if the header claims to contains 1e9 files, then data size should be at least dozens of gigs (which should be caught by e.g. HTTP content cap).

on commit 8017ace

@dvyukov dvyukov added this to the Go1.5 milestone May 26, 2015
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@gopherbot gopherbot commented May 27, 2015

CL mentions this issue.

@bradfitz bradfitz assigned bradfitz and unassigned adg May 27, 2015
@bradfitz bradfitz closed this in 553f45a May 27, 2015
@golang golang locked and limited conversation to collaborators Jun 25, 2016
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