移植sshd到JK2410开发板

1.       引言

SSH是由芬兰的一家公司开发出来的，但是由于版权和加密算法的限制，openssh作为一种安全的网络服务应用程序在业界被广泛应用。Openssh是ssh的代替软件而且免费。在上篇文档《移植OProfile到JK2410开发板》中有提到，Montavista 公司提供的应用程序开发和系统分析工具devrocket在调试和分析性能时需要在开发板和主机之间建立一条连接，通过ssh协议通信。由于JK2410开发板上没有配置sshd伺服程序，所以需要将sshd移植到JK2410开发板上。

2.       环境

硬件环境：

Host：

       X86 PC

Target：

JK2410开发板

 

软件环境：

Host：

       VMware 6

       OS：CentOS 5

       Strace 调试工具

Target：

       OS： linux-2.6.18 pro500

       RootFS: initrd-edwin-25M.img

Strace 调试工具

3.       移植步骤

源码包：

openssh-4.6p1.tar.gz  

openssl-0.9.8e.tar.gz     

zlib-1.2.3.tar.tar            

 

编译工具

       arm-9tdmi-linux-gnu-gcc 

    arm-9tdmi-linux-gnu-g++

 

3.1.   交叉编译

在/work目下面创建ssh目录

# mkdir /work/lib            ----〉共享库目录，通过nfs挂载

# mkdir /work/ssh           -----〉工作目录

# cd  /work/ssh

# mkdir compressed install source  -----〉compressed 用于存放源码包

                                                               Install    软件安装目录

                                                               Source    源码包解压目录

#mv tarpakgs/openssh-4.6p1.tar.gz  /work/ssh/compressed

#mv tarpakgs/openssl-0.9.8e.tar.gz  /work/ssh/compressed

#mv tarpakgs/zlib-1.2.3.tar.tar       /work/ssh/compressed

 

交叉编译 zlib

# cd /work/ssh/compressed/

# tar xvf zlib-1.2.3.tar.tar  -C  ../source

# cd ../source/zlib-1.2.3

# ./configure --prefix=/work/ssh/install/zlib-1.2.3

# vim Makefile

CC=arm-9tdmi-linux-gnu-gcc

AR=arm-9tdmi-linux-gnu-ar rc

CPP =arm-9tdmi-linux-gnu-gcc -E

LDSHARED=arm-9tdmi-linux-gnu-gcc

 

# make

# make install

 

交叉编译openssl

# cd /work/ssh/compressed/

# tar zxvf openssl-0.9.8e.tar.gz  -C  ../source

# cd ../source/openssl-0.9.8e

# ./Configure --prefix=/work/ssh/install/openssl-0.9.8e  os/compiler:arm-9tdmi-linux-gnu-gcc

 

# make

# make install

 

交叉编译openssh

# cd /work/ssh/compressed

# tar zxvf openssh-4.6p1.tar.gz  –C ../source

# cd ../source/ openssh-4.6p1

#./configure --host=arm-9tdmi-linux-gnu --with-libs --with-zlib=/work/ssh/install/zlib-1.2.3 --with-ssl-dir=/work/ssh/install/openssl-0.9.8e --disable-etc-default-login CC=arm-9tdmi-linux-gnu-gcc AR=arm-9tdmi-linux-gnu-ar

 

 

打印出如下信息：

OpenSSH has been configured with the following options:

User binaries: /usr/local/bin

System binaries: /usr/local/sbin

Configuration files: /usr/local/etc

Askpass program: /usr/local/libexec/ssh-askpass

Manual pages: /usr/local/share/man/manX

PID file: /var/run

Privilege separation chroot path: /var/empty

sshd default user PATH: /usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin

Manpage format: doc

PAM support: no

OSF SIA support: no

KerberosV support: no

SELinux support: no

Smartcard support: no

S/KEY support: no

TCP Wrappers support: no

MD5 password support: no

libedit support: no

Solaris process contract support: no

IP address in $DISPLAY hack: no

Translate v4 in v6 hack: yes

BSD Auth support: no

Random number source: OpenSSL internal ONLY

 

Host: arm-9tdmi-linux-gnu

Compiler: arm-9tdmi-linux-gnu-gcc

Compiler flags: -g -O2 -Wall -Wpointer-arith -Wuninitialized -Wsign-compare -std=gnu99

Preprocessor flags: -I/work/ssh/install/openssl-0.9.8e/include

                            -I/work/ssh/install/zlib-1.2.3/include

Linker flags: -L/work/ssh/install/openssl-0.9.8e/lib

                   -L/work/ssh/install/zlib-1.2.3/lib

Libraries:   -lresolv -lcrypto -lutil -lz -lnsl  -lcrypt

 

3.2.   安装sshd

按照上面打印出的信息在根文件系统中建立相应的目录并把相应的文件拷贝进去。

我的根文件系统镜像为/tftpboot/initrd-edwin-25M.img.

# cd /tftpboot/

# mkdir 25 && mount –oloop initrd-edwin-25M.img  25

#cd 25/usr/local  && mkdir bin etc libexec sbin share

#cd /work/ssh/source/openssh-4.6p1

#cp scp  sftp  ssh  ssh-add  ssh-agent  ssh-keygen  ssh-keyscan  /tftpboot/25/usr/local/bin

#cp moduli  ssh_config  sshd_config  ssh_host_dsa_key  ssh_host_dsa_key.pub  ssh_host_key  ssh_host_key.pub  ssh_host_rsa_key  ssh_host_rsa_key.pub  /tftpboot/25/usr/local/etc

# cp sftp-server  ssh-keysign   /tftpboot/25/usr/local/libexec

# cp sshd   /tftpboot/25/usr/local/sbin

 

3.3.   搭建调试软件环境

a)       u-boot参数设置

bootargs=root=/dev/ram0 rw console=ttySAC0,115200 mem=64M ramdisk=32768 initrd=0x30800000,25M init=/linuxrc

 bootcmd=tftpboot 0x33000000 uImage; tftpboot 0x30800000 initrd-edwin-25M.img; bootm 33000000

 

b)      将kernel镜像uImage和根文件系统镜像initrd-edwin-25M.img 拷贝到/tftpboot/目录下

c)      设置系统启动后将host机上/work目录挂载到target机上/edwin

Target:

vim /etc/init.d/rcS

echo "mount /work to /edwin .....";

mount -t nfs 192.168.167.131:/work /edwin -o nolock,rsize=1024,wsize=1024,timeo=15

d)      指定共享库搜索目录

Target：

vim /etc/profile

 

# Set search library path

echo "Set search library path in /etc/profile"

export LD_LIBRARY_PATH=/edwin/lib

 

#Set user path

echo "Set user path in /etc/profile"

PATH=/bin:/sbin:/usr/bin:/usr/sbin

export PATH

e)       启动sshd deamon程序

/usr/local/sbin/sshd

显示缺少的库文件，将其拷贝到host主机上的/work/lib目录下。

d)        用strace跟踪sshd，查询缺少的目录和文件，给与相应的添补。

strace –f  –F  /usr/local/sbin/sshd

 

e)         调试成功后将sshd加入自启动

Target：

vim /etc/profile

 

echo "start  sshd deamon routine ....."

/usr/local/sbin/sshd

f)          

 

4.       问题及解决方法

[问题1]

# /usr/local/sbin/sshd

/usr/local/sbin/sshd: error while loading shared libraries: libnsl.so.1: cannot open shared object file: No such file or directory

#

[分析与解决]

[root@localhost lib]# cp libnsl* /work/lib/

 

[问题2] 

# /usr/local/sbin/sshd

Privilege separation user sshd does not exist

#

[分析与解决]

没有sshd用户

sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin

 

Host:

[root@localhost etc]# cp  /etc/passwd   shadow group   /work

 

Target:

mv /edwin/passwd   /etc

mv /edwin/group    /etc

mv /edwin/shadow  /etc

 

注：将root:x:0:0:root:/root:/bin/bash改为root:x:0:0:root:/root:/bin/sh

 

 [问题3]

# /usr/local/sbin/sshd

Missing privilege separation directory: /var/empty

#

 

 

[分析与解决]

# mkdir /var/empty

# /usr/local/sbin/sshd

#

 

 [问题4]

[root@localhost .ssh]# ssh -l root 192.168.167.132

root@192.168.167.132's password:

Permission denied, please try again.

 

[分析与解决]

按照下面打印的消息，添补相应的文件或者目录，主要是用户帐户和密钥相关的文件。

Strace 分析如下：

 

stat64("/root/.ssh", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0

open("/etc/passwd", O_RDONLY)= 4

fcntl64(4, F_GETFD)= 0

fcntl64(4, F_SETFD, FD_CLOEXEC)= 0

fstat64(4, {st_mode=S_IFREG|0644, st_size=1908, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f13000

read(4, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1908

close(4)= 0

munmap(0xb7f13000, 4096)= 0

open("/root/.ssh/identity", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/identity", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/identity", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or d = 0

fcntl64(4, F_SETFD, FD_CLOEXEC)= 0

fstat64(4, {st_mode=S_IFREG|0644, st_size=1908, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f13000

read(4, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1908

close(4) irectory)

open("/root/.ssh/identity.pub", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/etc/passwd", O_RDONLY)= 4

fcntl64(4, F_GETFD)= 0

munmap(0xb7f13000, 4096)= 0

open("/root/.ssh/id_rsa", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/id_rsa", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/id_rsa", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/id_rsa.pub", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/etc/passwd", O_RDONLY)= 4

fcntl64(4, F_GETFD)= 0

fcntl64(4, F_SETFD, FD_CLOEXEC)= 0

fstat64(4, {st_mode=S_IFREG|0644, st_size=1908, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f13000

read(4, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1908

close(4)= 0

munmap(0xb7f13000, 4096)= 0

open("/root/.ssh/id_dsa", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/id_dsa", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/id_dsa", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/root/.ssh/id_dsa.pub", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

open("/etc/passwd", O_RDONLY)= 4

fcntl64(4, F_GETFD)= 0

fcntl64(4, F_SETFD, FD_CLOEXEC)= 0

fstat64(4, {st_mode=S_IFREG|0644, st_size=1908, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f13000

read(4, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1908

close(4)= 0

munmap(0xb7f13000, 4096)= 0

open("/etc/passwd", O_RDONLY)= 4

fcntl64(4, F_GETFD)= 0

fcntl64(4, F_SETFD, FD_CLOEXEC)= 0

fstat64(4, {st_mode=S_IFREG|0644, st_size=1908, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f13000

read(4, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1908

 

[问题5]

# ./ssh-keygen

Generating public/private rsa key pair.

Enter file in which to save the key (/root/.ssh/id_rsa):

Could not create directory '/root/.ssh'.

 

[分析与解决]

# ls /

bin etc linuxrc nfs sys var dev jffs2 lost+found  proc tmpfs yaffs2 edwin lib mnt sbin usr

# cd /root

-sh: cd: can't cd to /root

# mkdir root

# cd /root

# mkdir .ssh

# ls -a

. .. .ssh

 

# ./ssh-keygen

Generating public/private rsa key pair.

Enter file in which to save the key (/root/.ssh/id_rsa):

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /root/.ssh/id_rsa.

Your public key has been saved in /root/.ssh/id_rsa.pub.

The key fingerprint is:

76:dd:b7:c4:35:41:ce:35:97:5d:4e:36:54:fe:67:08 root@(none)

 

# ./ssh-keygen -d

Generating public/private dsa key pair.

Enter file in which to save the key (/root/.ssh/id_dsa):

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /root/.ssh/id_dsa.

Your public key has been saved in /root/.ssh/id_dsa.pub.

The key fingerprint is:

7a:96:b7:05:cf:d2:d1:e2:16:70:0a:6f:b2:62:12:d8 root@(none)

 

[问题6]

# /usr/local/sbin/sshd

Missing privilege separation directory: /var/empty

 

[分析与解决]

# ls /var

# mkdir /var/empty

# /usr/local/sbin/sshd

#

 

 

[问题7]

[root@localhost ~]# ssh 192.168.167.132

ssh: connect to host 192.168.167.132 port 22: Connection refused     

 

[分析与解决]

Target端sshd deamon程序没有启动。

 

/usr/local/sbin/sshd

[问题8]

Target 端sshd用户的创建？

 

[分析与解决]

用busybox制作的根文件系统提供的adduser和passwd命令和PC机上的使用方法不同。

PC机上创建帐户：

[root@localhost 25]#adduser  test

[root@localhost 25]# passwd test

[root@localhost 25]# passwd test

Changing password for user test.

New UNIX password:

 

Target上创建帐户：

首先要用-D选项设定不设定密码，否则会提示：unknown  uid

# adduser –h /test  -s /bin/sh   -D  test

# passwd  test

 

[问题9]

在客户端ssh到target板后，用户帐户和密码验证通过，但是没有启动shell？

 

[分析与解决]

Step1:用strace跟踪，没有发现任何有价值的信息。

Step2:修改openssh源码使其打印出尽可能多的debug信息。

       log.c文件注释掉以下两行就可以打印所有的调试信息了。

       //if (level > log_level)

              //return;

Step3:重新编译openssh并按照3.2重新安装sshd

Step4：target端创建/var/log目录

Step5：启动syslogd服务

Step6：启动sshd，并且在host端ssh到target端

       Host:  /usr/local/sbin/sshd

       Target：ssh –l root  192.168.167.132

观察var/log/messages debug信息：

 

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: session_by_channel: session 0 channel 0

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: session_input_channel_req: session 0 req pty-req

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: Allocating pty.

Jan  1 01:27:03 (none) auth.err sshd[436]: error: openpty: No such file or directory

Jan  1 01:27:03 (none) auth.err sshd[436]: error: session_pty_req: session 0 alloc failed

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: server_input_channel_req: channel 0 request env reply 0

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: session_by_channel: session 0 channel 0

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: session_input_channel_req: session 0 req env

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug2: Ignoring env request LANG: disallowed name

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: server_input_channel_req: channel 0 request shell reply 0

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: session_by_channel: session 0 channel 0

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug1: session_input_channel_req: session 0 req shell

Jan  1 01:27:03 (none) auth.err sshd[440]: error: setlogin failed: Illegal seek

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug2: fd 3 setting TCP_NODELAY

Jan  1 01:27:03 (none) auth.debug sshd[436]: debug2: fd 7 setting O_NONBLOCK

 

在openssh源码中搜索openpty，发现在openpty函数中需要打开许多设备文件，如: /dev/ptmx, pt, /dev/ptc等，意识到是不是缺少了相应的设备文件，因为制作根文件系统时根据需要选择部分的设备文件，并没有添加完全。于是将所有的设备文件都添加进去

#cp –avf /dev/*   /tftpboot/25/dev/

重新启动，还是不可以。

 

在网上搜索openpty，找到解决方法解决“sshd makes error 'openpty: No such file or directory”

- mknod /dev/ptmx c 5 2

      chmod 666 /dev/ptmx

      mkdir /dev/pts

 

- Add to /etc/fstab:

       none            /dev/pts        devpts        gid=5,mode=620    0 0

      

(Note:  gid=5 is applicable for RedHat systems for which group "tty" has gid 5.  Adjust according to your distribution.  Use mode=600 if you want "mesg n" to be default.

 

- Mount /dev/pts

 

原贴在：

 

按照上面的操作，从host端ssh到target端，ok。

 

5.       小结

Sshd总算移植成功了，很大一点感触是：强烈建议制作根文件系统时，把所有的设备文件添加上。Strace是个很好的跟踪调试工具。