一日開發發現使用pietty 0.4.00無法連上某台開發機(SUSE Linux Enterprise 12)，改用putty 0.70可正常連線
初步檢查client log發現在key exchange階段被server斷線
putty預設使用ECDH key exchange演算法
pietty使用Diffie-Hellman group exchange演算法，而pietty中沒有提供ECDH選項
持續使用了putty一段時間後…決定來解決這個問題
觀察系統dmesg發現sshd程式crash
[1288847.216184] type=1326 audit(1520387105.670:1595): auid=4294967295 uid=498 gid=498 ses=4294967295 pid=2322 comm="sshd" sig=31 syscall=4 compat=0 ip=0x7fbda0c9bdf5 code=0x0
[1288882.058782] type=1006 audit(1520387140.530:1596): pid=2323 uid=0 old auid=4294967295 new auid=2020 old ses=4294967295 new ses=1556 res=1
[1289237.351002] type=1006 audit(1520387496.018:1597): pid=2438 uid=0 old auid=4294967295 new auid=2020 old ses=4294967295 new ses=1557 res=1
[1289620.053059] type=1326 audit(1520387878.938:1598): auid=4294967295 uid=498 gid=498 ses=4294967295 pid=2570 comm="sshd" sig=31 syscall=4 compat=0 ip=0x7feca1389df5 code=0x0
猜測在server進行key exchange計算的時候崩潰
檢查/etc/ssh/sshd_config
KexAlgorithms欄位有列出相關演算法
撈取sshd相關lib備用
$ ldd sshd
linux-vdso.so.1 (0x00007fffd6700000)
libwrap.so.0 => /lib64/libwrap.so.0 (0x00007f067d848000)
libaudit.so.1 => /usr/lib64/libaudit.so.1 (0x00007f067d625000)
libpam.so.0 => /lib64/libpam.so.0 (0x00007f067d415000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f067d1f1000)
libcrypto.so.1.0.0 => /lib64/libcrypto.so.1.0.0 (0x00007f067cdff000)
libutil.so.1 => /lib64/libutil.so.1 (0x00007f067cbfb000)
libz.so.1 => /lib64/libz.so.1 (0x00007f067c9e5000)
libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007f067c7aa000)
libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2 (0x00007f067c562000)
libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x00007f067c291000)
libcom_err.so.2 => /lib64/libcom_err.so.2 (0x00007f067c08d000)
libc.so.6 => /lib64/libc.so.6 (0x00007f067bce4000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f067bae0000)
libpcre.so.1 => /usr/lib64/libpcre.so.1 (0x00007f067b87a000)
/lib64/ld-linux-x86-64.so.2 (0x00007f067dd41000)
libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3 (0x00007f067b649000)
libkrb5support.so.0 => /usr/lib64/libkrb5support.so.0 (0x00007f067b43c000)
libkeyutils.so.1 => /lib64/libkeyutils.so.1 (0x00007f067b238000)
libresolv.so.2 => /lib64/libresolv.so.2 (0x00007f067b020000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f067ae03000)
先排除系統程式問題，檢查系統完整性
# rpm -V --all
檢查列出檔案無上述相關程式檔或函式庫檔
改由另一台相同環境之開發機進行版本比對
# rpm -qa
比對發現三項可疑packages
libopenssl1_0_0-1.0.1i-18.1.x86_64 | libopenssl1_0_0-1.0.1i-2.12.x86
libz1-1.2.8-5.1.x86_64 | libz1-1.2.8-13.15.x86_64
openssl-1.0.1i-9.1.x86_64 | openssl-1.0.1i-2.12.x86_64
查詢詳細資訊如下(部分省略)
# rpm -qi libopenssl1_0_0
Name : libopenssl1_0_0
Version : 1.0.1i
Release : 18.1
Architecture: x86_64
Install Date: Tue Dec 19 10:29:11 2017
Size : 2581136
Build Date : Tue Sep 27 23:53:04 2016
Build Host : build81
Distribution: openSUSE Leap 42.1
# rpm -qi openssl
Name : openssl
Version : 1.0.1i
Release : 9.1
Architecture: x86_64
Install Date: Tue Dec 19 10:29:12 2017
Size : 1374628
Build Date : Wed Dec 9 00:26:26 2015
Build Host : cloud124
Distribution: openSUSE Leap 42.1
downgrade release
# rpm -Uvh --oldpackage libopenssl1_0_0-1.0.1i-2.12.x86_64.rpm openssl-1.0.1i-2.12.x86_64.rpm
Preparing... ################################# [100%]
Updating / installing...
1:libopenssl1_0_0-1.0.1i-2.12 ################################# [ 25%]
2:openssl-1.0.1i-2.12 ################################# [ 50%]
Cleaning up / removing...
3:openssl-1.0.1i-9.1 ################################# [ 75%]
4:libopenssl1_0_0-1.0.1i-18.1 ################################# [100%]
# rpm -qi libopenssl1_0_0
Name : libopenssl1_0_0
Version : 1.0.1i
Release : 2.12
Architecture: x86_64
Install Date: Wed Mar 7 10:20:30 2018
Size : 2568576
Build Date : Sat Sep 27 03:32:44 2014
Build Host : sheep15
Distribution: SUSE Linux Enterprise 12
# rpm -qi openssl
Name : openssl
Version : 1.0.1i
Release : 2.12
Architecture: x86_64
Install Date: Wed Mar 7 10:20:30 2018
Size : 1374054
Build Date : Sat Sep 27 03:32:44 2014
Build Host : sheep15
Distribution: SUSE Linux Enterprise 12
pietty即可順利連線
世界又恢復了和平
