Xpra’s authentication modules can be useful for: * securing socket connections * making the unix domain socket accessible to other users safely * using the proxy server
For more information on the different types of connections, see network. For more generic security information, please see security considerations
SSL mode can also be used for authentication using certificates (see #1252)
When using SSH to connect to a server, encryption and authentication can be skipped: by default the unix domain sockets used by ssh do not use authentication.
Xpra supports many authentication modules. Some of these modules require extra dependencies.
Here is the full list:Module | Result | Purpose |
---|---|---|
allow | always allows the user to login, the username used is the one supplied by the client | dangerous / only for testing |
none | always allows the user to login, the username used is the one the server is running as | dangerous / only for testing |
fail | always fails authentication, no password required | useful for testing |
reject | always fails authentication, pretends to ask for a password | useful for testing |
env | matches against an environment variable (XPRA_PASSWORD by default) |
alternative to file module |
password | matches against a password given as a module option, ie: auth=password:value=mysecret |
alternative to file module |
multifile | matches usernames and passwords against an authentication file | proxy: see password-file below |
file | compares the password against the contents of a password file, see password-file below | simple password authentication |
pam | linux PAM authentication | Linux system authentication |
win32 | win32security authentication | MS Windows system authentication |
sys |
system authentication | virtual module which will choose win32 or pam authentication automatically |
sqlite | sqlite database authentication | #1488 |
capability | matches values in the capabilities supplied by the client | #3575 |
peercred | SO_PEERCRED authentication |
#1524 |
tcp hosts | TCP Wrapper | #1730 |
exec | Delegates to an external command | #1690 |
kerberos-password | Uses kerberos to authenticate a username + password | #1691 |
kerberos-ticket | Uses a kerberos ticket to authenticate a client | #1691 |
gss_auth | Uses a GSS ticket to authenticate a client | #1691 |
keycloak | Uses a keycloak token to authenticate a client | #3334 |
ldap | Uses ldap via python-ldap | #1791 |
ldap3 | Uses ldap via python-ldap3 | #1791 |
u2f | Universal 2nd Factor | #1789 |
Starting with version 4.0, the preferred way of specifying authentication is within the socket option itself.
ie for starting a seamless server with a TCP
socket protected by a password stored in a file:
xpra start --start=xterm -d auth
--bind-tcp=0.0.0.0:10000,auth=file:filename=password.txt
So that multiple sockets can use different authentication modules, and those modules can more easily be chained:
xpra start --start=xterm -d auth \
--bind-tcp=0.0.0.0:10000,auth=hosts,auth=file:filename=password.txt --bind
--bind-tcp=0.0.0.0:10001,auth=sys
XPRA_PASSWORD=mysecret xpra start --bind-tcp=0.0.0.0:10000,auth=env
SOME_OTHER_ENV_VAR_NAME=mysecret xpra start --bind-tcp=0.0.0.0:10000,auth=env:name=SOME_OTHER_ENV_VAR_NAME
xpra start --bind-tcp=0.0.0.0:10000,auth=password:value=mysecret
xpra start --bind-tcp=0.0.0.0:10000,auth=file:filename=/path/to/mypasswordfile.txt
xpra start --bind-tcp=0.0.0.0:10000,auth=sqlite:filename=/path/to/userlist.sdb
The syntax with older versions used a dedicated switch for each socket type: * --auth=MODULE
for unix domain sockets and named pipes * --tcp-auth=MODULE
for TCP sockets * --vsock-auth=MODULE
for vsock (#983) etc
file
module, the password-file contains a single password, the whole file is the password (including any trailing newline characters). To write a password to a file without the trailing newline character, you can use echo -n "thepassword" > password.txt
multifile
, the password-file contains a list of authentication values, see proxy server - this module is deprecated in favour of the sqlite
module which is much easier to configurexpra attach tcp://username:password@host:port/
for connecting to the TCP
socket and specifying the password only:
xpra attach tcp://:password@host:port/
Since the username is ignored, it can also be replaced with any string of your liking, ie ‘foobar’:
xpra attach tcp://foobar:password@host:port/
Only the following modules will make use of both the username and password to authenticate against their respective backend: kerberos-password
, ldap
, ldap3
, sys
(pam
and win32
), sqlite
, multifile
and u2f
. In this case, using an invalid username will cause the authentication to fail.
The username is usually more relevant when authenticating against a proxy server (see authentication details there).
challenge-handlers
option, by default the client will try the following handlers in the specified order: uri
(whatever password may have been specified in the connection string), file
(if the password-file
option was used), env
(if the environment variable is present), kerberos
, gss
, keycloak
, u2f
and finally prompt
xpra info
pam
, win32
, kerberos-password
, ldap
and ldap3
) require the actual password to be sent across to perform the authentication on the server - they therefore use the weak xor
hashing, which is insecurexor
hashing so that the password is protected during the exchange: the system will refuse to send a xor
hashed password unencryptedauth
debug logging may leak some authentication information