| opaque(1) | simple command-line frontend for libopaque | opaque(1) |
opaque - simple command-line frontend for libopaque
Create new OPAQUE records
Create new opaque record - offline
echo -n password | opaque init idU idS 3>export_key [4<skS] >record
Initiate new online registration
echo -n password | opaque register >msg 3>ctx
Respond to new online registration request
opaque respond <msg >rpub 3>rsec [4<skS]
Finalize online registration
opaque finalize idU idS <ctx 4<rpub 3>export_key >record
Complete online record
opaque store <rec 3<rsec >record
Server portion of online registration
socat | opaque server-reg 3>record [4<skS]
User portion of online registration
socat | opaque user-reg idU idS 3< <(echo -n password) 4>export_key
Run OPAQUE
Server portion of OPAQUE session
socat | opaque server idU idS context 3<record 4>shared_key
User portion of OPAQUE session
socat | opaque user idU idS context 3< <(echo -n password) 4>export_key 5>shared_key [6<pkS]
The OPAQUE protocol is an asymmetric password-authenticated key-exchange. Essentially it allows a client to establish a shared secret with a server based on only having a password. The client doesn’t need to store any state. The protocol has two phases:
The initialization only needs to be executed once, the key-exchange can be executed as many times as necessary.
Initializing OPAQUE (registration) can be done either online or offline. The online variant has the benefit that the server never learns anything about the users password, with the drawback that this requires 3 messages to be exchanged by the client and the server.
The offline initialization is much easier, however either the user learns the servers secret, or the server learns the users password. The latter might be useful if some organisation wants to enforce some password quality rules and check those upon registration. The drawback is that either way, some sensitive information leaks to the other party.
echo -n password | ./opaque init user server >record 3>export_key
On the server:
socat tcp-l:23523,reuseaddr,fork system:"bash -c \'opaque server-reg user server 3>record\'"
On the client:
socat tcp:127.0.0.1:23523 exec:'bash -c \"opaque user-reg user server 3< <(echo -n password) 4>export_key\"'
On the server:
s6-tcpserver 127.0.0.1 23523 bash -c 'opaque server-reg user server 3>record'
On the client:
s6-tcpclient 127.0.0.1 23523 bash -c "opaque user-reg user server <&6 >&7 3< <(echo -n password) 4>export_key"
It’s possible to do all 4 steps seperately, in case you cannot connect to the server directly, then:
The user initiates with:
echo -n password | opaque register >msg 3>ctx
The server gets msg and responds with rpub, while keeping rsec secret:
cat msg | opaque respond >rpub 3>rsec
The user receives rpub and creates stub record and optionally uses the export key to encrypt more data:
cat ctx | opaque finalize user server 4<rpub >record 3>export_key
the server finalizes the record by completing the stub record from the client:
cat rec | opaque store user server >record 3<rsec
On the server:
s6-tcpserver 127.0.0.1 23523 bash -c './opaque server user server context 3<record 4>shared_secret'
On the client:
s6-tcpclient 127.0.0.1 23523 bash -c "./opaque user user server context <&6 >&7 3< <(echo -n password) 4>export_key 5>shared_secret"
On the server:
socat tcp-l:23523,reuseaddr,fork system:"bash -c \'./opaque server user server context 3<record 4>shared_secret\'"
On the client:
socat tcp:127.0.0.1:23523 exec:'bash -c \"./opaque user user server context 3< <(echo -n password) 4>export_key 5>shared_secret\"'
https://github.com/stef/libopaque/issues/
Written by Stefan Marsiske.
Copyright © 2023 Stefan Marsiske. License LGPLv3+: GNU Lesser GPL version 3 or later <https://gnu.org/licenses/lgpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
https://ctrlc.hu/~stef/blog/tags/opaque/
socat(1), tcpserver(1)