oracle(1)

NAME

oracle - server for the SPHINX password manager

SYNOPSIS

oracle [init]

DESCRIPTION

The SPHINX protocol only makes sense if the server (called oracle) is somewhere else than where you type your password, pwdsphinx comes with a server implemented in python3 which you can host off-site from your usual desktop/smartphone.

The server can be started simply by running oracle it does not take any parameters.

CONFIGURATION

The server can be configured by any of the following files:

•   /etc/sphinx/config

•   ~/.sphinxrc

•   ~/.config/sphinx/config

•   ./sphinx.cfg

Files are parsed in this order, this means global settings can be overridden by per-user and per-directory settings.

The server can be configured by changing the variables in the [server] section of the config file.

The address is the IP address on which the server is listening, default is localhost - you might want to change that.

The port where the server is listening is by default 2355. Another recommended values is to use port 433 which is allowed by most firewalls while 2355 is not.

ssl_key and ssl_cert must be specified, they point at a traditional TLS certificate and secret key file. It is recommended to not use self-signed certs, but to use certs that signed by CAs that are recognized widely by browsers and other TLS clients.

datadir specifies the data directory where all the device “secrets” are stored, this defaults to “data/” in the current directory. You might want to back up this directory from time to time to an encrypted medium.

verbose enables logging to standard output.

timeout sets the timeout for any connection the server keeps open.

max_kids sets the number maximum requests handled in parallel. The timeout config variable makes sure that all handlers are recycled in predictable time.

rl_decay specifies the number of seconds after which a ratelimit level decays to an easier difficulty.

rl_threshold increase the difficulty of ratelimit puzzles if not decaying.

rl_gracetime gracetime in seconds added to the expected time to solve a rate-limiting puzzle.

ltsigkey a path pointing at a long-term signature private key. This can be generated by running oracle init.

Initializing an oracle

Given a configuration, the oracle can generate its own long-term signature key. To do so, simply run oracle init and it will store the private key at the location pointed by the ltsigkey configuration value. This operation will also output the public key, at the same location as the private key, but with a .pub extension. Furthermore the public key is also displayed as a Base64 encoded string on the standard output.

SECURITY CONSIDERATIONS

The configuration values max_kids and timeout can be used to tune how many requests are served in parallel and how long each request is allowed to take before it gets killed. An attacker might be able to run a denial-of-service attack against your server, by keeping all max_kids connections “occupied”.

Since the server does only know about failed authorizations for management operations, but not about correctness of master passwords for get requests, there is no way to mitigate master password bruteforce attempts aside from ratelimiting. By tuning the configuration variables starting with rl_ it is possible to configure this. If you have clients that have less than 1G RAM, it might be possible to increase the difficulty to the maximum level where those devices will not be able to solve the ratelimting puzzles. Rate-limiting in general should not be noticeable, only if dozens of get requests are served to the same record. At the highest level the solution should take about 20-40 seconds (depending on your cpu).

REPORTING BUGS

https://github.com/stef/pwdsphinx/issues/

AUTHOR

Written by Stefan Marsiske.

COPYRIGHT

Copyright © 2024 Stefan Marsiske. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

sphinx(1), getpwd(1)