XEP-0257 specifies a protocol for clients to store and manage client side certificates. When a client presents a stored client side certificate during the TLS handshake, it can log in without supplying a password (using SASL EXTERNAL). This makes it possible to have multiple devices accessing an account, without any of them needing to know the password, and makes it easier to revoke access for a single device.
Each user can add their own certificates. These do not need to be signed by a trusted CA, yet they do need to be valid at the time of logging in and they should include an subjectAltName with otherName “id-on-xmppAddr” with the JID of the user.
To generate your own certificate with a “id-on-xmppAddr”
attribute using the command line openssl
tool, first create
a file called client.cnf
with contents:
[req] prompt = no
x509_extensions = v3_extensions
req_extensions = v3_extensions
distinguished_name = distinguished_name
[v3_extensions]
extendedKeyUsage = clientAuth
keyUsage = digitalSignature,keyEncipherment
basicConstraints = CA:FALSE
subjectAltName = @subject_alternative_name
[subject_alternative_name]
otherName.0 =
1.3.6.1.5.5.7.8.5;FORMAT:UTF8,UTF8:hamlet@shakespeare.lit
[distinguished_name]
commonName = Your Name
emailAddress = hamlet@shakespeare.lit
Replace the values for otherName.0
and
commonName
and emailAddress
with your own
values. The JID in otherName.0
can either be a full JID or
a bare JID, in the former case, the client can only use the resource
specified in the resource. There are many other fields you can add,
however, for SASL EXTERNAL, they will have no meaning. You can add more
JIDs as otherName.1
, otherName.2
,
etc.
Create a private key (as an example, a 4096 bits RSA key):
openssl genrsa -out client.key 4096
Create the certificate request:
openssl req -key client.key -new -out client.req -config client.cnf -extensions v3_extensions
Sign it yourself:
openssl x509 -req -days 365 -in client.req -signkey client.key -out client.crt -extfile client.cnf -extensions v3_extensions
The 365 means the certificate will be valid for a year starting now.
The client.key
must be kept secret, and
is only needed by clients connecting using this certificate. The
client.crt
file contains the certificate that should be
sent to the server using XEP-0257, and is also needed by clients
connecting to the server. The client.req
file is not needed
anymore.
(None yet)
0.9 | Works |
0.8 | Untested. Probably doesn’t. |
(None?)
Possible options to add to the configuration:
With the plugin installer in Prosody 0.12 you can use:
sudo prosodyctl install --server=https://modules.prosody.im/rocks/ mod_client_certs
For earlier versions see the documentation for installing 3rd party modules