FS#8742 - security flaw on console login - any username is denied directly without asking for password
Attached to Project:
Arch Linux
Opened by Jan M. (funkyou) - Friday, 23 November 2007, 10:34 GMT
Last edited by Tom Killian (tomk) - Friday, 30 November 2007, 11:51 GMT
Opened by Jan M. (funkyou) - Friday, 23 November 2007, 10:34 GMT
Last edited by Tom Killian (tomk) - Friday, 30 November 2007, 11:51 GMT
|
Details
When i login into a virtual terminal and specify an user
that is not available on my machine, the login is denied
immediately after entering the username.
Isnt the login supposed to take every username at first (even if it doesnt exist) and print out the "Password:" anyway before finally denying the login when i entered a password for the non-existant user? I consider this as a security issue, because with a little knowledge about myself it would be easier for a local attacker to compromise my system, because its easy to find out which users exist on my machine... (and thats a start, sure there a passords, but its a start...) More details here: http://bbs.archlinux.org/viewtopic.php?id=40246 |
This task depends upon
Closed by Tom Killian (tomk)
Friday, 30 November 2007, 11:51 GMT
Reason for closing: Fixed
Additional comments about closing: Fixed in shadow 4.0.18.2-1
Friday, 30 November 2007, 11:51 GMT
Reason for closing: Fixed
Additional comments about closing: Fixed in shadow 4.0.18.2-1
Have you possibly done any research into this? PAM is not my forte, but I don't see any glaring differences when compared to an ubuntu box here, besides the nullok_secure stuff which is debian specific.
Ideas?
This is the only message i get when specifying a nonexistant user:
login[4780]: FAILED LOGIN (1) on 'vc/1' FOR `UNKNOWN', User not known to the underlying authentication module
login[4780]: FAILED LOGIN (2) on 'vc/1' FOR `UNKNOWN', User not known to the underlying authentication module
login[4865]: FAILED LOGIN (3) on 'vc/1' FOR `UNKNOWN', User not known to the underlying authentication module
login[4865]: FAILED LOGIN (4) on 'vc/1' FOR `UNKNOWN', User not known to the underlying authentication module
Its the same message that appears when trying it without any username (just pressing enter)
I'll try to look some more into this, but i have zero experience with pam...
password required pam_unix.so md5 shadow use_authtok
Rebootet (just to be sure), but still no go and the same message in the logs
Just for completeness, here is how my /etc/pam.d/login looks now:
#%PAM-1.0
auth required pam_securetty.so
auth requisite pam_nologin.so
auth required pam_unix.so nullok
auth required pam_tally.so onerr=succeed file=/var/log/faillog
# use this to lockout accounts for 10 minutes after 3 failed attempts
#auth required pam_tally.so deny=2 unlock_time=600 onerr=succeed file=/var/log/faillog
account required pam_access.so
account required pam_time.so
account required pam_unix.so
#password required pam_cracklib.so difok=2 minlen=8 dcredit=2 ocredit=2 retry=3
password required pam_unix.so md5 shadow use_authtok
session required pam_unix.so
session required pam_env.so
session required pam_motd.so
session required pam_limits.so
session optional pam_mail.so dir=/var/spool/mail standard
session optional pam_lastlog.so
Tpowa, could you fix this asap? It's pretty important. If not then one of us can get to it, thanks to TomK
While on the topic, I just peeked and we have like 5 dead patches in CVS - can you remove those too?