Red Hat Bugzilla – Bug 781203
SSO: Logged in with kerberos user id, asking smart card pin while unlocking a locked screen.
Last modified: 2016-11-17 14:24:36 EST
Description of problem:
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. This user is not in the /etc/passwd file, authentication is
configured with userDatabase to LDAP server, kerberos support enabled, the
KDC information is provided and smart card support is enabled.
Use smart card: ON
Enforce smart card: OFF
Log out behavior configured to: Ignore smart card removal
2. Login to desktop with Kerberos userid and password.
3. Kerberos credential issued successfully.
4. Insert an enrolled smartcard for the user and perform e-mail signing or encryption/decryption.
5. Lock the screen by selecting menu option System -> Lock Screen and leave the smartcard in the card reader.
6. Move the mouse, this request for a password.
7. Enter the correct kerberos password.
Smart card PIN is requested. Entering kerberos password again on the PIN prompt unlocks the locked screen.
Screen should be unlocked.
[root@dhcp231-57 ~]# cat /etc/pam.d/system-auth
# This file is auto-generated.
# User changes will be destroyed the next time authconfig is run.
auth required pam_env.so
auth [success=3 default=ignore] pam_succeed_if.so service notin login:gdm:xdm:kdm:xscreensaver:gnome-screensaver:kscreensaver quiet use_uid
auth [success=ok ignore=2 default=die] pam_pkcs11.so wait_for_card
auth optional pam_krb5.so use_first_pass no_subsequent_prompt
auth sufficient pam_permit.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 500 quiet
auth sufficient pam_krb5.so use_first_pass
auth sufficient pam_ldap.so use_first_pass
auth required pam_deny.so
account required pam_unix.so broken_shadow
account sufficient pam_succeed_if.so uid < 500 quiet
account [default=bad success=ok user_unknown=ignore] pam_ldap.so
account [default=bad success=ok auth_err=ignore user_unknown=ignore ignore=ignore] pam_krb5.so
account required pam_permit.so
password optional pam_pkcs11.so
password requisite pam_cracklib.so authtok_type=LDAP try_first_pass retry=3
password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok
password sufficient pam_krb5.so use_authtok
password sufficient pam_ldap.so use_authtok
password required pam_deny.so
session optional pam_keyinit.so revoke
session required pam_limits.so
session optional pam_mkhomedir.so
session [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session required pam_unix.so
session optional pam_krb5.so
session optional pam_ldap.so
This is not a gnome-screensaver bug. It's either a pam_pkcs11 bug or a pam_krb5 bug, but we fixed it in pam_pkcs11 several years ago, so it's probably pam_krb5 pkinit-y bug.
Basically pam_pkcs11 has something like:
/* bail if the user didn't log in with smart card */
if (getenv("PKCS11_LOGIN_TOKEN_NAME") is empty) return PAM_IGNORE;
So my guess is the second pam_krb5 line in the auth section is getting run and it's not ignoring the smartcard like it should.
Punting forward, as the underpinnings of this setup have changed and we're not making big changes in this area in EL5 at this point.
(In reply to Ray Strode [halfline] from comment #1)
> Basically pam_pkcs11 has something like:
> /* bail if the user didn't log in with smart card */
> if (getenv("PKCS11_LOGIN_TOKEN_NAME") is empty) return PAM_IGNORE;
> So my guess is the second pam_krb5 line in the auth section is getting run
> and it's not ignoring the smartcard like it should.
With that configuration, then, a "no_subsequent_prompt" option added to that second invocation should also disable any attempts to gather PINS or passwords for PKINIT credentials.
I slightly wonder why the no_subsequent_prompt option was needed when use_first_pass should have basically the same meaning.
However if I add this option in authconfig, should it be always added or only in case the smartcard authentication is enabled?
(In reply to Tomas Mraz from comment #6)
> I slightly wonder why the no_subsequent_prompt option was needed when
> use_first_pass should have basically the same meaning.
> However if I add this option in authconfig, should it be always added or
> only in case the smartcard authentication is enabled?
Only for the smart card case, please.
Distinguishing between a user's long-term password (which use_first_pass affects) and non-password information that we may have to ask for (smart card PINs, OTP values) is... well, kind of a mess when the PAM_AUTHTOK can be any of those things, so no_subsequent_prompt, in combination with use_first_pass/try_first_pass, lets you control whether or not the module will allow the library to trigger an additional prompt, and whether or not it will just hand back the PAM_AUTHTOK if it does.