[Pkg-shadow-devel] Bug#495831: Bug#495831: Entering non-existant username at login prompt causes error message

[Tim Rørstrøm]

On Thursday 21 August 2008 06:58:19 you wrote:
> Quoting Tim Rørstrøm (timroerstroem at gmail.com):
> > Package: login
> > Version: 1:4.1.1-3
> > Severity: grave
> > Tags: security
> > Justification: user security hole
> >
> > At the console login prompt, entering a username which does not exist on
> > the system, will immediately show an error message, thus revealing that
> > the username is in fact non-existant on the system. This dramatically
> > reduces the time it would take to brute-force your way into a user's
> > account.
>
> Could you please send the content of /etc/pam.d/login ?

Attached
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#
# The PAM configuration file for the Shadow `login' service
#

# Enforce a minimal delay in case of failure (in microseconds).
# (Replaces the `FAIL_DELAY' setting from login.defs)
# Note that other modules may require another minimal delay. (for example,
# to disable any delay, you should add the nodelay option to pam_unix)
auth       optional   pam_faildelay.so  delay=3000000

# Outputs an issue file prior to each login prompt (Replaces the
# ISSUE_FILE option from login.defs). Uncomment for use
# auth       required   pam_issue.so issue=/etc/issue

# Disallows root logins except on tty's listed in /etc/securetty
# (Replaces the `CONSOLE' setting from login.defs)
# Note that it is included as a "requisite" module. No password prompts will
# be displayed if this module fails to avoid having the root password
# transmitted on unsecure ttys.
# You can change it to a "required" module if you think it permits to
# guess valid user names of your system (invalid user names are considered
# as possibly being root).
auth       requisite  pam_securetty.so

# Disallows other than root logins when /etc/nologin exists
# (Replaces the `NOLOGINS_FILE' option from login.defs)
auth       requisite  pam_nologin.so

# This module parses environment configuration file(s)
# and also allows you to use an extended config
# file /etc/security/pam_env.conf.
# 
# parsing /etc/environment needs "readenv=1"
session       required   pam_env.so readenv=1
# locale variables are also kept into /etc/default/locale in etch
# reading this file *in addition to /etc/environment* does not hurt
session       required   pam_env.so readenv=1 envfile=/etc/default/locale

# Standard Un*x authentication.
@include common-auth

# This allows certain extra groups to be granted to a user
# based on things like time of day, tty, service, and user.
# Please edit /etc/security/group.conf to fit your needs
# (Replaces the `CONSOLE_GROUPS' option in login.defs)
auth       optional   pam_group.so

# Uncomment and edit /etc/security/time.conf if you need to set
# time restrainst on logins.
# (Replaces the `PORTTIME_CHECKS_ENAB' option from login.defs
# as well as /etc/porttime)
# account    requisite  pam_time.so

# Uncomment and edit /etc/security/access.conf if you need to
# set access limits.
# (Replaces /etc/login.access file)
# account  required       pam_access.so

# Sets up user limits according to /etc/security/limits.conf
# (Replaces the use of /etc/limits in old login)
session    required   pam_limits.so

# Prints the last login info upon succesful login
# (Replaces the `LASTLOG_ENAB' option from login.defs)
session    optional   pam_lastlog.so

# Prints the motd upon succesful login
# (Replaces the `MOTD_FILE' option in login.defs)
session    optional   pam_motd.so

# Prints the status of the user's mailbox upon succesful login
# (Replaces the `MAIL_CHECK_ENAB' option from login.defs). 
#
# This also defines the MAIL environment variable
# However, userdel also needs MAIL_DIR and MAIL_FILE variables
# in /etc/login.defs to make sure that removing a user 
# also removes the user's mail spool file.
# See comments in /etc/login.defs
session    optional   pam_mail.so standard

# SELinux needs to intervene at login time to ensure that the process
# starts in the proper default security context.
# Uncomment the following line to enable SELinux
# session required pam_selinux.so multiple

# Standard Un*x account and session
@include common-account
@include common-session
@include common-password