Slashdot Mirror
OpenSSH Has a New Cipher — Chacha20-poly1305 — from D.J. Bernstein
First time accepted submitter ConstantineM writes "Inspired by a recent Google initiative to adopt ChaCha20 and Poly1305 for TLS, OpenSSH developer Damien Miller has added a similar protocol to ssh, chacha20-poly1305@openssh.com, which is based on D. J. Bernstein algorithms that are specifically optimised to provide the highest security at the lowest computational cost, and not require any special hardware at doing so. Some further details are in his blog, and at undeadly. The source code of the protocol is remarkably simple — less than 100 lines of code!"
http://pastebin.com/3YaRWXFs
/var is meant for variable content. Such as the mail spool and tmp directory. Data on this filesystem often comes from external sources such as email. It is recommended for this file system to be mounted with noexecute flag to reduce the likelihood of a downloaded data to be executed.
Having binaries on /var means that this filesystem can not be mounted with this option and therefor reduces security a bit.
SSH extensions are all specified by ASCII names. Standard extensions have names like "shell", "x11", and "port-forward", while vendor-specific extensions use names like "foo@openssh.com" or "bar@putty.org" so there's no naming collision risk.
Because on production servers it is common to have var on it's own partition, and that is the filesystem that holds the logs, which an attacker can cause data to be written to. Also it has to be writable by the running services, and allowing services to write and execute new binaries is a step in many attacks. So it is a typical thing a sysadmin wants to do, to prevent executing code there.
That said, the distro I'm using puts the executables under /usr regardless of where the upstream developer wants them to go. That isn't a decision for the app, it is one for the distro.
The referenced source file has no actual implementation of the encryption in it, so claiming 100 lines is a bit silly...
Using their metric of excluding the function calls that do the real work, OpenSSL only needs one line of source code to encrypt a file:
#!/bin/bash
openssl enc -aes-256-cbc -salt -in somefile.txt -out somefile.txt.enc
That's how you do a try...finally block in C.