libssh2是一个C 函数库，用来实现SSH2协议。
主要功能：
Key Exchange Methods: diffie-hellman-group1-sha1, diffie-hellman-group14-sha1, diffie-hellman-group-exchange-sha1
Hostkey Types: ssh-rsa, ssh-dss
Ciphers: aes256-cbc (rijndael-cbc@lysator.liu.se), aes192-cbc, aes128-cbc, 3des-cbc, blowfish-cbc, cast128-cbc, arcfour, none
Compression Schemes: zlib, none
MAC hashes: hmac-sha1, hmac-sha1-96, hmac-md5, hmac-md5-96, hmac-ripemd160 (hmac-ripemd160@openssh.com), none
Authentication: none, password, public-key, hostbased, keyboard-interactive
Channels: shell, exec (incl. SCP wrapper), direct-tcpip, subsystem
Global Requests: tcpip-forward
Channel Requests: x11, pty
Subsystems: sftp(version 3), publickey(version 2)
Thread-safe: just don't share handles simultaneously
Non-blocking: it can be used both blocking and non-blocking
Your sockets: the app hands over the socket, calls select() etc.
OpenSSL or gcrypt: builds with either
主页：http://www.libssh2.org/
来自:开源中国社区
