Chapter 29: Security
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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SSH2
SSH2 Description
The C4/c CMTS Secure Shell Protocol version 2 (SSH2) server provides a secure in-band management connection from a
remote client to manage the C4/c CMTS. The system management tools available with SSH services are:
Terminal service for interactive CLI and single-command execution
SFTP service for file transfer
Port Forwarding service for tunneling of insecure TCP connections, such as Telnet
SSH clients include the OpenSSH suite, PuTTY suite, and Vandyke Software SecureFX™ and SecureCRT™ applications.
SSH Protocol Architecture
The server only supports SSH version 2. The server is not backward compatible with SSH version 1 clients. The SSH protocol
involves three layers:
SSH-Transport layer implementing server authentication, confidentiality, and integrity over a TCP connection
SSH-UserAuth layer providing client user authentication
SSH-Connection layer multiplexing simultaneous sessions over a single SSH-Transport TCP connection
SSH-Transport Highlights
During the establishment of the SSH-Transport layer, the server is authenticated with the client using public key
authentication. The server only supports the DSA PEM-formatted server (aka, host) key type. A private server key must be
configured before the server can be started. Regarding key exchange, the server only supports the diffie-hellman-group1-
sha1 method. The server also supports key re-exchange (aka, rekeying). For message confidentiality, the server supports
these configurable encryption ciphers: 3des aes arcfour blowfish cast. For message integrity, the server supports these
fixed MAC hash functions: md5 md5-96 sha1 sha1-96.