pkexec fails with ERROR:pkexec.c:138:pam_conversation_function: code should not be reached

[Vreixo Formoso]

pkexec fails with the error:

ERROR:pkexec.c:138:pam_conversation_function: code should not be reached

in up-to-date Ubuntu 11.10. I have taken a look to the source code and it seems related to the fake conversation function used when PAM is invoked (pkexec.c:160 in packaged sources -.orig-). In my system I have a fprint PAM module to authenticate, but it also fails after disabling it.
Policykit authentication other than pkexec seems to work properly. A look at polkitagenthelper-pam.c shows that a proper concersation function is used.
I guess a similar function could be used for pkexec, but I have not enough skills on pam/policykit to address this.

Thanks in advance
Vreixo

[Vreixo Formoso (metalpain2002)]

It seems only affected me, and I'm not using fprint now, so I'm not suffering this problem. No idea whether it is still an issue in new releases.

[mystercoco (mystercoco-gmail)]

I had the same problem, it looks like pexec is no more working on recent Ubuntu version.
It was generating a lot of crash windows at startup.

A quick and dirty fix (no more errors at least):
# sudo mv /usr/bin/pkexec /usr/bin/pkexec.old
# sudo ln -s /usr/bin/gksudo /usr/bin/pkexec

Sincerely

Technical Details:

ProblemType: Crash
Architecture: amd64
CrashCounter: 1
Date: Sat Nov 9 14:35:29 2013
DistroRelease: Ubuntu 13.10
ExecutablePath: /usr/bin/pkexec
ExecutableTimestamp: 1379527177
ProcCmdline: pkexec /usr/lib/update-notifier/package-system-locked
ProcCwd: /home/mystercoco
ProcEnviron:
 TERM=xterm
 SHELL=/bin/bash
 PATH=(custom, user)
 LANG=fr_FR.UTF-8
 LANGUAGE=fr_FR
 XDG_RUNTIME_DIR=<set>

[Doudz (sebastien-ramage)]

I got the same problem on Ubuntu 16.04, pkexec just doesn't work after entering password

Exemple :

pkexec gedit
**
ERROR:pkexec.c:138:pam_conversation_function: code should not be reached
Abandon

[Sami Kantoluoto (sami-kantoluoto)]

I'm also having the problem on Ubuntu 16.04 with kerberos authentication.

[Marc Neiger (marc-i)]

I 'm now having this problem on 16.04 (Mint 18.1), I suspect it may be related to adding ldap and sssd caching, but it's unclear.

[Dario CIPRUT (dciprut)]

Same problem on 16.04 LTS (Ubuntu Xenial). No clue except i am using pam_mount.

[InfoLibre (david-vantyghem)]

Same error when lauching Synaptic (synaptic-pkexec), since I added my Linux Mint MATE 18.2 computer into a Windows 2003 domain with realm (kerberos, sssd).

[InfoLibre (david-vantyghem)]

In fact, the problem doesn't appear since I added my Linux Mint MATE 18.2 computer into a Windows domain but since I added pam_mount in /etc/pam.d/common-session :

session optional pam_mount.so

If I remove this line, it works again.

[InfoLibre (david-vantyghem)]

I found a (bad ?) solution. I keep pam_mount in /etc/pam.d/common-session file :

session optional pam_mount.so

and I add user="" in /etc/security/pam_mount.conf.xml file :

<volume
 fstype="cifs" server="2008-STD" path="Users/Administrateur/Desktop/Dossier partagé pour test"
 mountpoint="/home/%(USER)/Bureau/Dossier test"
 options="sec=krb5,cruid=%(USERUID),uid=%(USERUID)"
 user=""
/>

And it works !???

[InfoLibre (david-vantyghem)]

I posted a bug report on https://sourceforge.net/p/pam-mount/bugs/123/

[InfoLibre (david-vantyghem)]

Finally, I add the name of the user that can mount the shared folder and it works :

<volume
 fstype="cifs" server="2008-STD" path="Users/Administrateur/Desktop/Dossier partagé pour test"
 mountpoint="/home/%(USER)/Bureau/Dossier test"
 options="sec=krb5,cruid=%(USERUID),uid=%(USERUID)"
 user="<name>@<domain>"
/>

With <name> is the Windows user name and <domain> is the Active Directory domain name.

(I tried with user="%(USER)" but it doesn't work at all)

[Marc Neiger (marc-i)]

I have the very same problem using LDAP authentication (not Windows active directory.
I have a few user="*" but user="" would disable the mount, wouldn't it?

[Marc Neiger (marc-i)]

Each line now has user="*" or uses extended user control and the problem disappeared.
Thanks