tomaswolf commented on issue #493: URL: https://github.com/apache/mina-sshd/issues/493#issuecomment-2116149268
OK, thank you. Essentially: arcfour256 works only with the `hmac-*-etm` MACs. This is a bug; it's caused by wrong block sizes being set. Yes, arcfour128 and arcfour256 are stream ciphers, but a block size must be set anyway because SSH RFC 4253 insists that > Note that the length of the concatenation of 'packet_length', 'padding_length', 'payload', and 'random padding' MUST be a multiple of the cipher block size or 8, whichever is larger. This constraint MUST be enforced, even when using stream ciphers. [RFC 4253, section 6](https://datatracker.ietf.org/doc/html/rfc4253#page-7) So for arcfour128 and arcfour256, the "blocksize" must be 8. Unfortunately, this is wrong at https://github.com/apache/mina-sshd/blob/71b842f759f9879d7638bed175e5be006d9c0f46/sshd-common/src/main/java/org/apache/sshd/common/cipher/BuiltinCiphers.java#L118 and at https://github.com/apache/mina-sshd/blob/71b842f759f9879d7638bed175e5be006d9c0f46/sshd-common/src/main/java/org/apache/sshd/common/cipher/BuiltinCiphers.java#L129 The last parameter must not be 16 or 32 but 8. arcfour128 works by chance, arcfour256 will fail for small packets. I'll push a fix soon. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: dev-unsubscr...@mina.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@mina.apache.org For additional commands, e-mail: dev-h...@mina.apache.org
