限制SSH用户访问Linux中指定的目录

限制SSH用户访问Linux中指定的目录
http://os.51cto.com/art/201703/534895.htm#topx http://www.cnblogs.com/lykyl/archive/2011/03/10/1980304.html
采用ChrootDirectory设置需要注意
ChrootDirectory设置的目录及其所有的上级目录属主必须是root且只有属主能拥有写权限，也就是说权限最大设置只能是755。否则会报“fatal: bad ownership or modes for chroot directory”这样的错误。
用户目录下的链接文件失去作用。

useradd readonlyuser;echo -e "123456\n123456\n" |passwd readonlyuser

mkdir -p /ngbs/readonlyuser/dev/
cd /ngbs/readonlyuser/dev/
mknod -m 666 null c 1 3
mknod -m 666 tty c 5 0
mknod -m 666 zero c 1 5
mknod -m 666 random c 1 8

chown root:root /ngbs/readonlyuser
chmod 0755 /ngbs/readonlyuser

mkdir -p /ngbs/readonlyuser/bin
cp /bin/bash /ngbs/readonlyuser/bin/
mkdir -p /ngbs/readonlyuser/lib64/
cp /lib64/{libtinfo.so.5,libdl.so.2,libc.so.6,ld-linux-x86-64.so.2} /ngbs/readonlyuser/lib64/

mkdir /ngbs/readonlyuser/etc
cp -f /etc/{passwd,group} /ngbs/readonlyuser/etc/
tail -1 /ngbs/readonlyuser/etc/passwd >/tmp/1.txt ;cat /tmp/1.txt > /ngbs/readonlyuser/etc/passwd

注意：每次向系统添加更多 SSH 用户时，都需要将更新的帐户文件复制到 /ngbs/readonlyuser/etc 目录中。

vi /etc/ssh/sshd_config
在此文件中添加或修改下面这些行。
# override default of no subsystems
Subsystem ssh /usr/bin/ssh #这里改为ssh

# Example of overriding settings on a per-user basis
Match User readonlyuser 改为Match User readonlyuser
Match User readonlyuser 下面加上这一行 ChrootDirectory /ngbs/readonlyuser

也就是下面这样
# override default of no subsystems
Subsystem ssh /usr/bin/ssh

# Example of overriding settings on a per-user basis
Match User readonlyuser
ChrootDirectory /ngbs/readonlyuser
# X11Forwarding no
# AllowTcpForwarding no

重启 sshd 服务：
/etc/init.d/sshd restart

接下来，在 bin 目录中安装几个用户命令
cp /bin/ls /ngbs/readonlyuser/bin/
cp /bin/cat /ngbs/readonlyuser/bin/
cp /bin/more /ngbs/readonlyuser/bin/
cp /usr/bin/less /ngbs/readonlyuser/bin/
cp /usr/bin/head /ngbs/readonlyuser/bin/
cp /usr/bin/tail /ngbs/readonlyuser/bin/

ldd /bin/ls
ldd /bin/cat
ldd /bin/more
ldd /usr/bin/less
ldd /usr/bin/head
ldd /usr/bin/tail

/bin/cp /lib64/{libselinux.so.1,librt.so.1,libcap.so.2,libacl.so.1,libc.so.6,libdl.so.2,ld-linux-x86-64.so.2,libpthread.so.0,libattr.so.1,libtinfo.so.5,libpcre.so.0} /ngbs/readonlyuser/lib64/

测试 SSH 的 chroot 监狱
ssh readonlyuser@192.168.0.10

*/1 * * * * /usr/bin/rsync -a /ngbs/local/JmCash/log/* /ngbs/readonlyuser/log/
*/1 * * * * /usr/bin/rsync -a /ngbs/local/JmCash/logs/* /ngbs/readonlyuser/logs/
*/1 * * * * /usr/bin/rsync -a /ngbs/local/JmCash/phonelog/* /ngbs/readonlyuser/phonelog/

注意：如果是目录外做一个软链接到目录内是不行的，会报错 no such file or directory
ln -s /data/download /home/test

注意：sftp

30)外部子系统

我们可以配置一个外部的子系统,仅用于SSH-V2协议,一般这里使用sftp,如下:
Subsystem sftp /usr/libexec/openssh/sftp-server
如关闭该选项,将无法使用sftp.
我们看一下使用sftp的通讯过程,如下:
sftp -v 192.168.27.142 /*采用sftp的方式连接ssh服务端*/
Connecting to 192.168.27.142...
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 192.168.27.142 [192.168.27.142] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type 1
debug1: identity file /root/.ssh/id_dsa type 2
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '192.168.27.142' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:1
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: gssapi-keyex,gssapi-with-mic,password,hostbased
debug1: Next authentication method: password
root@192.168.27.142's password:
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug1: Sending subsystem: sftp /*在这里启用了sftp子系统*/
sftp>

我们看一下服务端的进程:
ps -ef|grep ssh
avahi 1133 1 0 03:08 ? 00:00:00 avahi-daemon: registering [ssh-server.local]
root 1718 1 0 03:14 ? 00:00:00 sshd: root@pts/0
root 2005 1 0 03:50 ? 00:00:00 /usr/sbin/sshd
root 2023 2005 0 03:52 ? 00:00:00 sshd: root@notty
root 2025 2023 0 03:52 ? 00:00:00 /usr/libexec/openssh/sftp-server
注:
我们看到服务端启用了sftp-server为sftp客户请求服务.