Bug 498465 - adduser created user with the next available UID for ALL domains but should do from LOCAL only
adduser created user with the next available UID for ALL domains but should d...
Product: Fedora
Classification: Fedora
Component: shadow-utils (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Peter Vrabec
Fedora Extras Quality Assurance
Depends On:
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Reported: 2009-04-30 11:57 EDT by Michal Nowak
Modified: 2014-06-09 07:55 EDT (History)
4 users (show)

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Doc Type: Bug Fix
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Last Closed: 2010-06-28 08:17:32 EDT
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Description Michal Nowak 2009-04-30 11:57:31 EDT
Description of problem:

sssd_test:x:11005:11005:SSSD 1 test user:/home/sssd_test:/bin/bash

So the next created user is this one:


but it should be some thing like:


This prevented SSSD from letting me login to local sshd instance:

dhcp-lab-124 ~ # ssh localhost -l validlocaluser@LEGACYLOCAL
validlocaluser@LEGACYLOCAL@localhost's password: 
Permission denied, please try again.
validlocaluser@LEGACYLOCAL@localhost's password: 
Permission denied, please try again.
validlocaluser@LEGACYLOCAL@localhost's password: 

Because it honors only UID within range ~500-~5000.

sgallagh said on this: 
"I think we just found a limitation of the shadow-utils adduser function. It created the user with the next available UID for ALL domains"

Version-Release number of selected component (if applicable):


How reproducible:


Actual results:

UID/GID from ALL range

Expected results:

UID/GID from LOCAL range

Additional info:


Believe sgallagh can explain this issue much deeper than me when necessary.
Comment 1 Stephen Gallagher 2009-04-30 12:15:33 EDT
What we discovered was that adduser will create a user whose userid is one greater than the highest UID returned by any domain in the NSS passwd databases.

This poses a problem in an SSSD-enabled world, where we have distinct ranges for what constitutes a valid NSS domain. For example, users 500-10000 might be reserved for /etc/passwd, users 10001-30000 might be reserved for NIS and 30001-100000 might be reserved for LDAP users.

If an admin creates a new userID in such a system, allowing it to choose the default, it would naturally pick a UID in the range of the highest UID domain.

Furthermore, this is a problem in a non-SSSD world where LDAP or NIS is in play, because if the remote server does not enable full enumeration, it's possible for adduser to create a new user whose UID matches that of a network user who has simply not been queried before on the machine.

The appropriate behaviour (in my opinion) would be to either disallow automatic UID generation entirely (or at least warn loudly), or else restrict it to only the contents of /etc/passwd.
Comment 2 Peter Vrabec 2009-05-04 08:52:15 EDT
I suggest to use UID_MIN/UID_MAX and GID_MIN/GID_MAX variables in /etc/login.defs.

# useradd -u 10300 velky
# id velky
uid=10300(velky) gid=10300(velky) groups=10300(velky)
# vim /etc/login.defs
"set up UID_MAX and GID_MAX"
# useradd maly
# id maly
uid=525(maly) gid=525(maly) groups=525(maly)

Are you fine with this solution? 
What should be the range for local users?
Comment 3 Peter Vrabec 2009-05-07 05:02:58 EDT
hey Stephen, it would be good to push this now in early stage of F12. I would also change lower UID limit from 500 to 1000, as it is in other distros/upstream. But there is need for some consensus. Maybe email on fedora-devel.
Comment 4 Bug Zapper 2009-06-09 10:54:01 EDT
This bug appears to have been reported against 'rawhide' during the Fedora 11 development cycle.
Changing version to '11'.

More information and reason for this action is here:
Comment 5 Bug Zapper 2010-04-27 10:01:52 EDT
This message is a reminder that Fedora 11 is nearing its end of life.
Approximately 30 (thirty) days from now Fedora will stop maintaining
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Comment 6 Bug Zapper 2010-06-28 08:17:32 EDT
Fedora 11 changed to end-of-life (EOL) status on 2010-06-25. Fedora 11 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

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