✔️ CentOS 5 + bash 3.2, CentOS 6 + bash 4.1.2, CentOS 7 + bash 4.2.45에서 테스트하였습니다.
1 개요[ | ]
- shellshock
- [CVE-2014-6271] GNU Bash 원격코드 인젝션 취약점 확인 및 조치
- 2014년 9월 Bourne Again Shell(Bash) 취약점 보안 업데이트
- 쉘쇼크, 셸쇼크, 쉘쇼크 해결방법, 조치방법
- CentOS 6: bash-4.1.2-15.el6_4.x86_64 → bash-4.1.2-15.el6_5.2.x86_64
- CentOS 7: bash-4.2.45-5.el7.x86_64 → bash-4.2.45-5.el7_0.4.x86_64
2 확인방법[ | ]
Bash
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env x='() { :;}; echo vulnerable' bash -c "echo this is a test"
Bash
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rm -f echo; env X='() { (a)=>\' sh -c "echo date"; cat echo
Bash
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(for x in {1..200} ; do echo "for x$x in ; do :"; done; for x in {1..200} ; do echo done ; done) | bash ||
echo "CVE-2014-7187 vulnerable, word_lineno"
3 확인 1 (취약)[ | ]
Console
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[root@zetawiki ~]# env x='() { :;}; echo vulnerable' bash -c "echo this is a test"
vulnerable
this is a test
- →
echo vulnerable이 수행되었으므로 취약함
Console
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[root@zetawiki ~]# rm -f echo; env X='() { (a)=>\' sh -c "echo date"; cat echo
sh: X: line 1: syntax error near unexpected token `='
sh: X: line 1: `'
sh: error importing function definition for `X'
Sun Feb 15 18:41:31 KST 2015
- → date 명령어가 실행되고 echo 파일이 생성되었으므로 취약함
Console
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[root@zetawiki ~]# (for x in {1..200} ; do echo "for x$x in ; do :"; done; for x in {1..200} ; do echo done ; done) | bash ||
> echo "CVE-2014-7187 vulnerable, word_lineno"
bash: line 129: syntax error near `x129'
bash: line 129: `for x129 in ; do :'
CVE-2014-7187 vulnerable, word_lineno
- → echo ... 명령어가 수행되었으므로 취약함
4 Bash 버전 확인[ | ]
Bash 버전 확인 문서를 참고하십시오.
Console
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[root@zetawiki ~]# rpm -qa | grep bash
bash-3.2-32.el5
Console
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[root@zetawiki ~]# rpm -qa | grep bash
bash-4.1.2-15.el6_4.x86_64
5 Bash 업데이트[ | ]
Console
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[root@zetawiki ~]# yum update bash
... (생략)
================================================================
Package Arch Version Repository Size
================================================================
Updating:
bash x86_64 4.1.2-29.el6 base 907 k
Transaction Summary
================================================================
Upgrade 1 Package(s)
Total download size: 907 k
Is this ok [y/N]: y
Console
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... (생략)
Updated:
bash.x86_64 0:4.1.2-29.el6
Complete!
6 확인 2 (안전)[ | ]
Console
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[root@zetawiki ~]# env x='() { :;}; echo vulnerable' bash -c "echo this is a test"
this is a test
Console
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[root@zetawiki ~]# rm -f echo; env X='() { (a)=>\' sh -c "echo date"; cat echo
date
cat: echo: No such file or directory
Console
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[root@zetawiki ~]# (for x in {1..200} ; do echo "for x$x in ; do :"; done; for x in {1..200} ; do echo done ; done) | bash ||
> echo "CVE-2014-7187 vulnerable, word_lineno"