JSchException：算法协商失败

Question

我正在尝试使用JSch（0.1.44-1）通过ssh连接到远程sftp服务器，但是在“ session.connect（）;”期间 我收到此异常：

com.jcraft.jsch.JSchException: Algorithm negotiation fail at 
com.jcraft.jsch.Session.receive_kexinit(Session.java:529) at 
com.jcraft.jsch.Session.connect(Session.java:291) at com.jcraft.jsch.Session.connect(Session.java:154)
...

来自JSch的日志：

INFO: Connecting to xx.xx.xx.xxport 22 
INFO: Connection established 
INFO: Remote version string: SSH-2.0-WeOnlyDo 2.0.6 
INFO: Local version string: SSH-2.0-JSCH-0.1.44 
INFO: CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256
INFO: aes256-ctr is not available. 
INFO: aes192-ctr is not available.
INFO: aes256-cbc is not available. 
INFO: aes192-cbc is not available.
INFO: arcfour256 is not available. 
INFO: SSH_MSG_KEXINIT sent
INFO: SSH_MSG_KEXINIT received 
INFO: Disconnecting from xx.xx.xx.xx port 22

我可以使用linux sftp命令登录到远程服务器。我试图在互联网上找到任何线索，但是失败了。

linux sftp命令的调试输出：

OpenSSH_5.5p1-DAM_1.2, OpenSSL 0.9.8r 8 Feb 201

debug1: Reading configuration data /etc/DAM/ssh/ssh_config
debug1: Applying options for *
debug1: Applying options for *.*
debug1: Connecting to xx.xx.xx.xx [xx.xx.xx.xx] port 22.
debug1: Connection established.
debug1: identity file /**/spv_id_rsa.key type -1
debug1: identity file /**/spv_id_rsa.key-cert type -1
debug1: Remote protocol version 2.0, remote software version WeOnlyDo 2.0.6
debug1: no match: WeOnlyDo 2.0.6
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.5p1-DAM_1.2
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes256-cbc hmac-md5 none
debug1: kex: client->server aes256-cbc hmac-md5 none
debug1: sending SSH2_MSG_KEXDH_INIT
debug1: expecting SSH2_MSG_KEXDH_REPLY
debug1: Host 'xx.xx.xx.xx' is known and matches the RSA host key.
debug1: Found key in ~/.ssh/known_hosts:8
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /**/spv_id_rsa.key
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: Sending subsystem: sftp
Connected to xx.xx.xx.xx.
sftp>

Answer 1

SSH客户端和服务器在几个地方尝试并同意一个通用实现。我知道的两个是加密和压缩。服务器和客户端生成可用选项的列表，然后在两个列表中选择最佳的可用选项。

如果列表中没有可接受的选项，则它将失败，并显示错误消息。我从这里的调试输出中猜测出来，但是看起来唯一的加密服务器选项是“ aes256-cbc hmac-
md5 none”。

JSch不执行hmac-md5，并且由于Java策略文件而禁用了aes256-cbc。您可以尝试的两件事是…

1. 要增加服务器上可用的加密库，请在客户端上安装不受限制的策略文件，并从站点启用aes256-cbc（确保已声明禁用该消息，这些策略文件非常容易安装在错误的JVM上） ：

对于JDK
1.6：http
:
//www.oracle.com/technetwork/java/javase/downloads/jce-6-download-429243.html

对于JDK
1.7：http
:
//www.oracle.com/technetwork/java/javase/downloads/jce-7-download-432124.html

对于JDK
1.8：http
:
//www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html

1. 或尝试禁用加密。

如果您可以访问服务器，则第一个是理想的选择（请相信aes128-cbc具有足够的加密功能），但是第二个非常容易，可以快速验证该理论。