linux命令：系统裁剪之五dropbear嵌入式系统专用ssh服务

Posted 2020-08-24

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Linux系统裁剪笔记之五dropbear嵌入式系统专用ssh远程登录服务

1.什么裁剪?

本篇文章的主要目的是让笔者和读者更深的认识Linux系统的运作方式,大致内容就是把Linux拆开自己一个个组件来组装,然后完成一个微型的Linux系统.下面,让我们来实现吧..写的不好的地方请指教.

2.原理

大家都知道,操作系统的启动流程是(主要是Linux):POST—>Bios—>MBR—kernel-->initrd-->sbin/init,

POST,BIOS都不是我们管的,所以这里我们从MBR开始,Linux的系统引导先主要是用的grub这个软件,grub引导系统了,然后启动内核,内核调用initrd来实现最基本的操作系统.

3.实验目的（给精简linux增加ssh服务应用）

前期准备：已经安装制作了一个精简的linux系统

在宿主虚拟机添加IDE硬盘，并分2个分区，并挂载:

mount /dev/hda1 /mnt/boot

mount /dev/hda2 /mnt/sysroot

dropbear：嵌入式系统专用的ssh服务器端和客户端工具

服务器端：dropbear dropbearkey

客户端：dbclient

dropbear默认使用nsswitch实现名称解析

/etc/nsswitch.conf

/lib/libnss_files*

/usr/lib/libnss3.so

/usr/lib/libnss_files*

dropbear会在用户登录检查其默认shell是否当前系统的安全shell

/etc/shells

主机密钥默认位置：

/etc/dropbear/

RSA：dropbear_rsa_host_key （RSA加密方式）

长度可变，只要是8的整数倍，默认为1024

DSS：dropbear_dss_host_key (DSS加密方式)

长度固定，默认为1024

dropbearkey 生成密钥命令

-t rsa|dss 指定密钥类型

-f /path/to/KEY_FILE 指定生成的密钥保存位置

-s SIZE 指定生成密钥的字节大小

实现ssh远程登录服务的步骤如下：

1、先下载dropbear-2013.56.tar.bz2

[[email protected] ~]# lftp [email protected] 登录ftp服务器

口令:

lftp [email protected]:/> get dropbear-2013.56.tar.bz2 下载dropber软件

1578454 bytes transferred

lftp [email protected]:/> exit

[[email protected] ~]# ls

anaconda-ks.cfg Desktop install.log sbin bin sys lib dev

install.log.syslog showdate.sh busybox-1.20.2 dropbear-2013.56.tar.bz2

[[email protected] ~]# tar xf dropbear-2013.56.tar.bz2 解压缩安装包

[[email protected] ~]# cd dropbear-2013.56 进入解压缩目录

[[email protected] dropbear-2013.56]#./configure 编译前生成makefile

[[email protected] dropbear-2013.56]#make 编译

[[email protected] dropbear-2013.56]# make install 编译安装

install -d -m 755 /usr/local/sbin

install -m 755 dropbear /usr/local/sbin

chown root /usr/local/sbin/dropbear

chgrp 0 /usr/local/sbin/dropbear

install -d -m 755 /usr/local/bin

install -m 755 dbclient /usr/local/bin

chown root /usr/local/bin/dbclient

chgrp 0 /usr/local/bin/dbclient

install -d -m 755 /usr/local/bin

install -m 755 dropbearkey /usr/local/bin

chown root /usr/local/bin/dropbearkey

chgrp 0 /usr/local/bin/dropbearkey

install -d -m 755 /usr/local/bin

install -m 755 dropbearconvert /usr/local/bin

chown root /usr/local/bin/dropbearconvert

chgrp 0 /usr/local/bin/dropbearconvert

[[email protected] dropbear-2013.56]# cd ~ 进入到家目录，该目录有复制binlib脚本

[[email protected] ~]# ./cpbin.sh 执行复制库命令脚本，复制dropbear所需的三个文档

dropbear dbclient dropbearkey

Your command:dropbear

copy /usr/local/sbin/dropbear is finished.

copy lib /lib64/libcrypt.so.1 finished.

copy lib /lib64/libutil.so.1 finished.

copy lib /usr/lib64/libz.so.1 finished.

copy /usr/local/sbin/dropbear finished.

Continue: dbclient

copy /usr/local/bin/dbclient is finished.

copy /usr/local/bin/dbclient finished.

Continue: dropbearkey

copy /usr/local/bin/dropbearkey is finished.

copy /usr/local/bin/dropbearkey finished.

Continue: q

[[email protected] ~]# sync

[[email protected] ~]# cd /mnt/sysroot 进入到系统挂载的根目录

[[email protected] sysroot]# vim etc/shells 新建shell文档

/bin/sh

/bin/bash

/bin/ash

/bin/hush

[[email protected] sysroot]# vim etc/fstab 编辑fstab文档

sysfs /sys sysfs defaults 0 0

proc /proc proc defaults 0 0

devpts /dev/pts devpts mode=620 0 0 新增改行内容

/dev/hda1 /boot ext3 defaults 0 0

/dev/hda2 / ext3 defaults 1 1

[[email protected] sysroot]# mkdir dev/pts 新建pts目录

[[email protected] sysroot]# sync

[[email protected] sysroot]# mkdir etc/dropbear

[[email protected] sysroot]# dropbearkey -t rsa -f /mnt/sysroot/etc/dropbear

/drobear_rsa_host_key -s 2048 指定密钥类型为rsa并生成密钥存储在指定目录中

Will output 2048 bit rsa secret key to ‘/mnt/sysroot/etc/dropbear/dropbear_rsa_host_key‘

Generating key, this may take a while...

Public key portion is:

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAwCkisXjhRaNz1oHo4XbFR6LHGHx7rtk8CVGJ263h5UBWUtmoo/fVZK/x8ZvzJQiDJn3sQjxH9DT41wpFnu79Z1h2Fmfq0YSmRVc0jxlYGfJWScIbspkFF89kGa0z+PuqD1lEbbrzCQ8lfzqNS7CYA3OOZKlLxfGQbev7KGMqvaHOkorEHP7D27nIug1Ftm5DWqax3lIOfL5r5fdMMMVjVQvRM8ZXV7RiXZKnHeMJhkLcB4dbkZy1mktEjTd43tDUSf+Knz/oz0sEt1eNxSCoqf20Q62syJIWJhE3ZTTBdvrKhhoiEOP8UScgH88AogkQgONL7srCxZ0dCCFOIDZc+6q4Rc= [email protected]

Fingerprint: md5 03:df:ce:13:9c:72:98:4c:56:10:77:21:2d:de:1f:6b

[[email protected] sysroot]# dropbearkey -t dss -f /mnt/sysroot/etc/dropbear

/drobear_dss_host_key 指定密钥类型为dss并生成密钥存储在指定目录中

Will output 1024 bit dss secret key to ‘/mnt/sysroot/etc/dropbear/dropbear_dss_host_key‘

Generating key, this may take a while...

Public key portion is:

ssh-dss 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 [email protected]

Fingerprint: md5 9f:b0:e3:8f:71:c4:ca:89:90:97:7f:a5:f1:48:dc:bf

[[email protected] sysroot]# ls etc/dropbear/

dropbear_dss_host_key dropbear_rsa_host_key 两种类型的密钥已生成

[[email protected] sysroot]# mkdir usr/lib

[[email protected] sysroot]# ls usr/

bin lib lib64 local sbin

[[email protected] sysroot]# pwd

/mnt/sysroot

[[email protected] sysroot]# cd ~

[[email protected] ~]# cp -d /lib/libnss_files* /mnt/sysroot/lib/ 复制密钥所需的库文件

[[email protected] ~]# cp -d /usr/lib/libnss3.so /usr/lib/libnss_files.so /mnt/sysroot/usr/lib/ 复制密钥所需库文件，路径要对应

[[email protected] ~]# ls /mnt/sysroot/lib