Bug 23877 - sshd leaks username information to remote clients
Summary: sshd leaks username information to remote clients
Keywords:
Status: CLOSED RAWHIDE
Alias: None
Product: Red Hat Linux
Classification: Retired
Component: openssh
Version: 7.1
Hardware: i386
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Nalin Dahyabhai
QA Contact:
URL:
Whiteboard: Florence Beta-3
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2001-01-12 15:35 UTC by Tim Waugh
Modified: 2008-05-01 15:37 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2001-01-18 05:04:47 UTC
Embargoed:


Attachments (Terms of Use)

Description Tim Waugh 2001-01-12 15:35:05 UTC
On a beta2 ssh server with users 'fred' and 'root', I see the following behaviour from a beta1 client:

$ ssh fred@server
Enter passphrase for DSA key '/home/twaugh/.ssh/id_dsa':
Password:
Password:
Received disconnect: 2: too many failed userauth_requests

(I don't know the password)

$ ssh madeupname@server
Enter passphrase for DSA key '/home/twaugh/.ssh/id_dsa':
Connection closed by 172.16.10.45

Eek!  Now I know that 'fred' is an allowed user on the server!

It _ought_ to ask me for my password regardless of whether the user exists or not.

Comment 1 Pekka Savola 2001-01-12 20:30:22 UTC
Hmm, how exactly did you do this?  Was ssh-agent concerned?

SSH beta2 -> beta2 goes:

* first, generate a DSA key with passphrase, insert it in authorized_keys2.
* root is the real acct

root@install5 .ssh]# ssh root@install5
Enter passphrase for DSA key '/root/.ssh/id_dsa': 
root@install5's password: 
Permission denied, please try again.
root@install5's password: 
Permission denied, please try again.
root@install5's password: 
Unable to find an authentication method

[root@install5 .ssh]# ssh blarg@install5    
Enter passphrase for DSA key '/root/.ssh/id_dsa': 
blarg@install5's password: 
Permission denied, please try again.
blarg@install5's password: 
Permission denied, please try again.
blarg@install5's password: 
Unable to find an authentication method

Or did you try this some other way?


Comment 2 Tim Waugh 2001-01-12 22:41:36 UTC
Here's a localhost-only how-to-repeat:

[root@cocobean /root]# ls .ssh
ls: .ssh: No such file or directory
[root@cocobean /root]# finger fred
finger: fred: no such user.
[root@cocobean /root]# rpm --verify openssh-server openssh
[root@cocobean /root]# rpm -q openssh-server openssh
openssh-server-2.3.0p1-9
openssh-2.3.0p1-9
[root@cocobean /root]# service sshd status
sshd (pid 871 453) is running...
[root@cocobean /root]# ssh fred@localhost
Connection closed by 127.0.0.1
[root@cocobean /root]# useradd tim
[root@cocobean /root]# ssh tim@localhost
Password: 

This is reproducible on all machines I've installed beta1/beta2 on now (three of them).

Comment 3 Pekka Savola 2001-01-12 23:32:46 UTC
Ok, RH patch openssh-2.3.0p1-auth2-pam.patch is at fault (at least) here.  If you disable KbdInteractiveAuthentication, 
this doesn't happen anymore.





Comment 4 Pekka Savola 2001-01-13 00:03:35 UTC
Note: it'd appear that OpenSSH CVS snapshots (http://bass.directhit.com/openssh_snap/) 
have this fixed, probably since Dec 20.


Comment 5 Glen Foster 2001-01-15 21:46:49 UTC
This defect is considered MUST-FIX for Florence Beta-3


Comment 6 Nalin Dahyabhai 2001-01-18 07:15:07 UTC
Hey, that's a bug in auth2-pam.c.  Fixed in openssh-2.3.0p1-10.


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