PAM tweaks to enable login with blank password from console on CentOS 7.6.1810 Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) 2019 Community Moderator Election Results Why I closed the “Why is Kali so hard” questionPAM login permission deniedpam: action on (unsuccessful) loginHowto Tell if a System authenticate with password only or through PAMUnable to login with password as well as otp in pam moduleUsing pam_listfile.so with radius authenticationUse multiple PAM login methods at once?How to local user login(PAM) with MySQL?PAM: Sequences in Linux Login Password Being Flagged UnexpectedlyPAM: Authentication failure, with valid passwordsetting sudo password different from login password

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PAM tweaks to enable login with blank password from console on CentOS 7.6.1810



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
2019 Community Moderator Election Results
Why I closed the “Why is Kali so hard” questionPAM login permission deniedpam: action on (unsuccessful) loginHowto Tell if a System authenticate with password only or through PAMUnable to login with password as well as otp in pam moduleUsing pam_listfile.so with radius authenticationUse multiple PAM login methods at once?How to local user login(PAM) with MySQL?PAM: Sequences in Linux Login Password Being Flagged UnexpectedlyPAM: Authentication failure, with valid passwordsetting sudo password different from login password



.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








0















I am writing an application that forces the user to change his password after the first login. I set a blank password for this admin user with 



passwd -d admin


and verified that no password was set in /etc/shadow



# grep admin /etc/shadow
admin::17834:0:99999:7:::


However, my attempts to login from the console (not ssh) all fail. Can one or more rules in /etc/pam.d/* be tweaked to allow this login? I had once built a debug version of pam and replaced the default library with it (in a custom ISO) to understand which rules were being invoked but it generated humongous amount of log messages.



UPDATE:
I (force-)installed a PAM RPM built with debugging enabled and captured all logs pertinent to a login attempt from the console:



[pam_item.c:pam_set_item(31)] called
[pam_delay.c:_pam_start_timer(42)] starting timer...
[pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(201)] returning userprompt=(null)
[pam_item.c:pam_get_user(281)] called.
[misc_conv.c:misc_conv(279)] allocating empty response structure array.
[misc_conv.c:misc_conv(288)] entering conversation function.
[misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.
[misc_conv.c:read_string(203)] we got some user input
[pam_item.c:pam_set_item(31)] called
[pam_item.c:pam_get_user(380)] completed
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
[pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Error in service module
[pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=3 retval=3
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_item.c:pam_get_user(281)] called.
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
[pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
[pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
[pam_dispatch.c:_pam_dispatch_aux(100)] skipping substack handler
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
[pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=25 retval=25
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
[pam_delay.c:pam_fail_delay(150)] largest = 0
[pam_delay.c:pam_fail_delay(153)] resetting largest delay
[pam_item.c:pam_get_user(281)] called.
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
[pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
[pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_unix_auth.c:pam_sm_authenticate(112)] called.
[support.c:_set_ctrl(139)] called.
[support.c:_set_ctrl(146)] IAMROOT
[support.c:_set_ctrl(279)] done.
[pam_item.c:pam_get_user(281)] called.
[support.c:_unix_blankpasswd(680)] called
[support.c:_unix_read_password(888)] called
[pam_item.c:pam_get_item(179)] called.
[misc_conv.c:misc_conv(279)] allocating empty response structure array.
[misc_conv.c:misc_conv(288)] entering conversation function.
[misc_conv.c:read_string(136)] called with echo='OFF', prompt='Password: '.
[misc_conv.c:read_string(203)] we got some user input
[pam_item.c:pam_set_item(31)] called
[pam_item.c:pam_get_item(179)] called.
[pam_unix_auth.c:pam_sm_authenticate(175)] user=admin, password=[]
[support.c:_unix_verify_password(730)] called
[support.c:_unix_verify_password(734)] setting delay
[pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
[pam_delay.c:pam_fail_delay(150)] largest = 2000000
[support.c:_unix_verify_password(741)] locating user's record
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
[support.c:_unix_verify_password(755)] running helper binary
[support.c:_unix_run_helper_binary(544)] called.
[passverify.c:verify_pwd_hash(74)] called
[passverify.c:verify_pwd_hash(84)] user has empty password - access denied
[passverify.c:verify_pwd_hash(133)] done [7].
[support.c:_unix_run_helper_binary(662)] returning 7
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(206)] returning tty=tty1
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[support.c:_unix_verify_password(867)] done [7].
[pam_unix_auth.c:pam_sm_authenticate(181)] recording return code for next time [7]
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_unix_auth.c:pam_sm_authenticate(181)] done. [Authentication failure]
[pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Authentication failure
[pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-3 cached_retval=7 retval=7
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
[pam_delay.c:pam_fail_delay(150)] largest = 2000000
[pam_item.c:pam_get_user(281)] called.
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_get_data(123)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_data.c:pam_set_data(70)] called
[pam_data.c:_pam_locate_data(46)] called
[pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(206)] returning tty=tty1
[pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
[pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-4 cached_retval=25 retval=25
[pam_item.c:pam_set_item(31)] called
[pam_item.c:pam_set_item(31)] called
[pam_delay.c:_pam_await_timer(90)] waiting?...
[pam_delay.c:_pam_compute_delay(76)] random number: base=2000000 -> ans=1674256

[pam_delay.c:_pam_await_timer(114)] will wait 1674256 usec
[pam_delay.c:_pam_reset_timer(27)] setting pamh->fail_delay.set to FALSE
[pam_delay.c:_pam_await_timer(126)] waiting done
[pam_auth.c:pam_authenticate(39)] pam_authenticate exit
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(196)] returning user=admin
[pam_item.c:pam_set_item(31)] called
[pam_auth.c:pam_authenticate(18)] pam_authenticate called
[pam_item.c:pam_set_item(31)] called
[pam_item.c:pam_set_item(31)] called
[pam_delay.c:_pam_start_timer(42)] starting timer...
[pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
[pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
[pam_item.c:pam_get_item(179)] called.
[pam_item.c:pam_get_item(201)] returning userprompt=(null)
[pam_item.c:pam_get_user(281)] called.
[misc_conv.c:misc_conv(279)] allocating empty response structure array.
[misc_conv.c:misc_conv(288)] entering conversation function.
[misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.


Looking at the source, a check in modules/pam_unix/passverify.c (must be pam_unix.so) is tripping






authentication pam







share|improve this question






























    0















    I am writing an application that forces the user to change his password after the first login. I set a blank password for this admin user with 



    passwd -d admin


    and verified that no password was set in /etc/shadow



    # grep admin /etc/shadow
    admin::17834:0:99999:7:::


    However, my attempts to login from the console (not ssh) all fail. Can one or more rules in /etc/pam.d/* be tweaked to allow this login? I had once built a debug version of pam and replaced the default library with it (in a custom ISO) to understand which rules were being invoked but it generated humongous amount of log messages.



    UPDATE:
    I (force-)installed a PAM RPM built with debugging enabled and captured all logs pertinent to a login attempt from the console:



    [pam_item.c:pam_set_item(31)] called
    [pam_delay.c:_pam_start_timer(42)] starting timer...
    [pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(201)] returning userprompt=(null)
    [pam_item.c:pam_get_user(281)] called.
    [misc_conv.c:misc_conv(279)] allocating empty response structure array.
    [misc_conv.c:misc_conv(288)] entering conversation function.
    [misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.
    [misc_conv.c:read_string(203)] we got some user input
    [pam_item.c:pam_set_item(31)] called
    [pam_item.c:pam_get_user(380)] completed
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
    [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Error in service module
    [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=3 retval=3
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_item.c:pam_get_user(281)] called.
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
    [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
    [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
    [pam_dispatch.c:_pam_dispatch_aux(100)] skipping substack handler
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
    [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=25 retval=25
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
    [pam_delay.c:pam_fail_delay(150)] largest = 0
    [pam_delay.c:pam_fail_delay(153)] resetting largest delay
    [pam_item.c:pam_get_user(281)] called.
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
    [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
    [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_unix_auth.c:pam_sm_authenticate(112)] called.
    [support.c:_set_ctrl(139)] called.
    [support.c:_set_ctrl(146)] IAMROOT
    [support.c:_set_ctrl(279)] done.
    [pam_item.c:pam_get_user(281)] called.
    [support.c:_unix_blankpasswd(680)] called
    [support.c:_unix_read_password(888)] called
    [pam_item.c:pam_get_item(179)] called.
    [misc_conv.c:misc_conv(279)] allocating empty response structure array.
    [misc_conv.c:misc_conv(288)] entering conversation function.
    [misc_conv.c:read_string(136)] called with echo='OFF', prompt='Password: '.
    [misc_conv.c:read_string(203)] we got some user input
    [pam_item.c:pam_set_item(31)] called
    [pam_item.c:pam_get_item(179)] called.
    [pam_unix_auth.c:pam_sm_authenticate(175)] user=admin, password=[]
    [support.c:_unix_verify_password(730)] called
    [support.c:_unix_verify_password(734)] setting delay
    [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
    [pam_delay.c:pam_fail_delay(150)] largest = 2000000
    [support.c:_unix_verify_password(741)] locating user's record
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
    [support.c:_unix_verify_password(755)] running helper binary
    [support.c:_unix_run_helper_binary(544)] called.
    [passverify.c:verify_pwd_hash(74)] called
    [passverify.c:verify_pwd_hash(84)] user has empty password - access denied
    [passverify.c:verify_pwd_hash(133)] done [7].
    [support.c:_unix_run_helper_binary(662)] returning 7
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(206)] returning tty=tty1
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [support.c:_unix_verify_password(867)] done [7].
    [pam_unix_auth.c:pam_sm_authenticate(181)] recording return code for next time [7]
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_unix_auth.c:pam_sm_authenticate(181)] done. [Authentication failure]
    [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Authentication failure
    [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-3 cached_retval=7 retval=7
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
    [pam_delay.c:pam_fail_delay(150)] largest = 2000000
    [pam_item.c:pam_get_user(281)] called.
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_get_data(123)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_data.c:pam_set_data(70)] called
    [pam_data.c:_pam_locate_data(46)] called
    [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(206)] returning tty=tty1
    [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
    [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-4 cached_retval=25 retval=25
    [pam_item.c:pam_set_item(31)] called
    [pam_item.c:pam_set_item(31)] called
    [pam_delay.c:_pam_await_timer(90)] waiting?...
    [pam_delay.c:_pam_compute_delay(76)] random number: base=2000000 -> ans=1674256

    [pam_delay.c:_pam_await_timer(114)] will wait 1674256 usec
    [pam_delay.c:_pam_reset_timer(27)] setting pamh->fail_delay.set to FALSE
    [pam_delay.c:_pam_await_timer(126)] waiting done
    [pam_auth.c:pam_authenticate(39)] pam_authenticate exit
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(196)] returning user=admin
    [pam_item.c:pam_set_item(31)] called
    [pam_auth.c:pam_authenticate(18)] pam_authenticate called
    [pam_item.c:pam_set_item(31)] called
    [pam_item.c:pam_set_item(31)] called
    [pam_delay.c:_pam_start_timer(42)] starting timer...
    [pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
    [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
    [pam_item.c:pam_get_item(179)] called.
    [pam_item.c:pam_get_item(201)] returning userprompt=(null)
    [pam_item.c:pam_get_user(281)] called.
    [misc_conv.c:misc_conv(279)] allocating empty response structure array.
    [misc_conv.c:misc_conv(288)] entering conversation function.
    [misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.


    Looking at the source, a check in modules/pam_unix/passverify.c (must be pam_unix.so) is tripping






    authentication pam







    share|improve this question


























      0












      0








      0








      I am writing an application that forces the user to change his password after the first login. I set a blank password for this admin user with 



      passwd -d admin


      and verified that no password was set in /etc/shadow



      # grep admin /etc/shadow
      admin::17834:0:99999:7:::


      However, my attempts to login from the console (not ssh) all fail. Can one or more rules in /etc/pam.d/* be tweaked to allow this login? I had once built a debug version of pam and replaced the default library with it (in a custom ISO) to understand which rules were being invoked but it generated humongous amount of log messages.



      UPDATE:
      I (force-)installed a PAM RPM built with debugging enabled and captured all logs pertinent to a login attempt from the console:



      [pam_item.c:pam_set_item(31)] called
      [pam_delay.c:_pam_start_timer(42)] starting timer...
      [pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(201)] returning userprompt=(null)
      [pam_item.c:pam_get_user(281)] called.
      [misc_conv.c:misc_conv(279)] allocating empty response structure array.
      [misc_conv.c:misc_conv(288)] entering conversation function.
      [misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.
      [misc_conv.c:read_string(203)] we got some user input
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_get_user(380)] completed
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Error in service module
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=3 retval=3
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_item.c:pam_get_user(281)] called.
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
      [pam_dispatch.c:_pam_dispatch_aux(100)] skipping substack handler
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=25 retval=25
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
      [pam_delay.c:pam_fail_delay(150)] largest = 0
      [pam_delay.c:pam_fail_delay(153)] resetting largest delay
      [pam_item.c:pam_get_user(281)] called.
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_unix_auth.c:pam_sm_authenticate(112)] called.
      [support.c:_set_ctrl(139)] called.
      [support.c:_set_ctrl(146)] IAMROOT
      [support.c:_set_ctrl(279)] done.
      [pam_item.c:pam_get_user(281)] called.
      [support.c:_unix_blankpasswd(680)] called
      [support.c:_unix_read_password(888)] called
      [pam_item.c:pam_get_item(179)] called.
      [misc_conv.c:misc_conv(279)] allocating empty response structure array.
      [misc_conv.c:misc_conv(288)] entering conversation function.
      [misc_conv.c:read_string(136)] called with echo='OFF', prompt='Password: '.
      [misc_conv.c:read_string(203)] we got some user input
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_get_item(179)] called.
      [pam_unix_auth.c:pam_sm_authenticate(175)] user=admin, password=[]
      [support.c:_unix_verify_password(730)] called
      [support.c:_unix_verify_password(734)] setting delay
      [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
      [pam_delay.c:pam_fail_delay(150)] largest = 2000000
      [support.c:_unix_verify_password(741)] locating user's record
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [support.c:_unix_verify_password(755)] running helper binary
      [support.c:_unix_run_helper_binary(544)] called.
      [passverify.c:verify_pwd_hash(74)] called
      [passverify.c:verify_pwd_hash(84)] user has empty password - access denied
      [passverify.c:verify_pwd_hash(133)] done [7].
      [support.c:_unix_run_helper_binary(662)] returning 7
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(206)] returning tty=tty1
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [support.c:_unix_verify_password(867)] done [7].
      [pam_unix_auth.c:pam_sm_authenticate(181)] recording return code for next time [7]
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_unix_auth.c:pam_sm_authenticate(181)] done. [Authentication failure]
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Authentication failure
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-3 cached_retval=7 retval=7
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
      [pam_delay.c:pam_fail_delay(150)] largest = 2000000
      [pam_item.c:pam_get_user(281)] called.
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(206)] returning tty=tty1
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-4 cached_retval=25 retval=25
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_set_item(31)] called
      [pam_delay.c:_pam_await_timer(90)] waiting?...
      [pam_delay.c:_pam_compute_delay(76)] random number: base=2000000 -> ans=1674256

      [pam_delay.c:_pam_await_timer(114)] will wait 1674256 usec
      [pam_delay.c:_pam_reset_timer(27)] setting pamh->fail_delay.set to FALSE
      [pam_delay.c:_pam_await_timer(126)] waiting done
      [pam_auth.c:pam_authenticate(39)] pam_authenticate exit
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(196)] returning user=admin
      [pam_item.c:pam_set_item(31)] called
      [pam_auth.c:pam_authenticate(18)] pam_authenticate called
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_set_item(31)] called
      [pam_delay.c:_pam_start_timer(42)] starting timer...
      [pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(201)] returning userprompt=(null)
      [pam_item.c:pam_get_user(281)] called.
      [misc_conv.c:misc_conv(279)] allocating empty response structure array.
      [misc_conv.c:misc_conv(288)] entering conversation function.
      [misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.


      Looking at the source, a check in modules/pam_unix/passverify.c (must be pam_unix.so) is tripping






      authentication pam







      share|improve this question
















      I am writing an application that forces the user to change his password after the first login. I set a blank password for this admin user with 



      passwd -d admin


      and verified that no password was set in /etc/shadow



      # grep admin /etc/shadow
      admin::17834:0:99999:7:::


      However, my attempts to login from the console (not ssh) all fail. Can one or more rules in /etc/pam.d/* be tweaked to allow this login? I had once built a debug version of pam and replaced the default library with it (in a custom ISO) to understand which rules were being invoked but it generated humongous amount of log messages.



      UPDATE:
      I (force-)installed a PAM RPM built with debugging enabled and captured all logs pertinent to a login attempt from the console:



      [pam_item.c:pam_set_item(31)] called
      [pam_delay.c:_pam_start_timer(42)] starting timer...
      [pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(201)] returning userprompt=(null)
      [pam_item.c:pam_get_user(281)] called.
      [misc_conv.c:misc_conv(279)] allocating empty response structure array.
      [misc_conv.c:misc_conv(288)] entering conversation function.
      [misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.
      [misc_conv.c:read_string(203)] we got some user input
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_get_user(380)] completed
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Error in service module
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=3 retval=3
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_item.c:pam_get_user(281)] called.
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
      [pam_dispatch.c:_pam_dispatch_aux(100)] skipping substack handler
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=0 cached_retval=25 retval=25
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
      [pam_delay.c:pam_fail_delay(150)] largest = 0
      [pam_delay.c:pam_fail_delay(153)] resetting largest delay
      [pam_item.c:pam_get_user(281)] called.
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Success
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-1 cached_retval=0 retval=0
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_unix_auth.c:pam_sm_authenticate(112)] called.
      [support.c:_set_ctrl(139)] called.
      [support.c:_set_ctrl(146)] IAMROOT
      [support.c:_set_ctrl(279)] done.
      [pam_item.c:pam_get_user(281)] called.
      [support.c:_unix_blankpasswd(680)] called
      [support.c:_unix_read_password(888)] called
      [pam_item.c:pam_get_item(179)] called.
      [misc_conv.c:misc_conv(279)] allocating empty response structure array.
      [misc_conv.c:misc_conv(288)] entering conversation function.
      [misc_conv.c:read_string(136)] called with echo='OFF', prompt='Password: '.
      [misc_conv.c:read_string(203)] we got some user input
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_get_item(179)] called.
      [pam_unix_auth.c:pam_sm_authenticate(175)] user=admin, password=[]
      [support.c:_unix_verify_password(730)] called
      [support.c:_unix_verify_password(734)] setting delay
      [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
      [pam_delay.c:pam_fail_delay(150)] largest = 2000000
      [support.c:_unix_verify_password(741)] locating user's record
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [support.c:_unix_verify_password(755)] running helper binary
      [support.c:_unix_run_helper_binary(544)] called.
      [passverify.c:verify_pwd_hash(74)] called
      [passverify.c:verify_pwd_hash(84)] user has empty password - access denied
      [passverify.c:verify_pwd_hash(133)] done [7].
      [support.c:_unix_run_helper_binary(662)] returning 7
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(206)] returning tty=tty1
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [support.c:_unix_verify_password(867)] done [7].
      [pam_unix_auth.c:pam_sm_authenticate(181)] recording return code for next time [7]
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_unix_auth.c:pam_sm_authenticate(181)] done. [Authentication failure]
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: Authentication failure
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-3 cached_retval=7 retval=7
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_delay.c:pam_fail_delay(141)] setting delay to 2000000
      [pam_delay.c:pam_fail_delay(150)] largest = 2000000
      [pam_item.c:pam_get_user(281)] called.
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_get_data(123)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_data.c:pam_set_data(70)] called
      [pam_data.c:_pam_locate_data(46)] called
      [pam_modutil_getpwnam.c:pam_modutil_getpwnam(92)] success
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(206)] returning tty=tty1
      [pam_dispatch.c:_pam_dispatch_aux(114)] module returned: The return value should be ignored by PAM dispatch
      [pam_dispatch.c:_pam_dispatch_aux(198)] use_cached_chain=0 action=-4 cached_retval=25 retval=25
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_set_item(31)] called
      [pam_delay.c:_pam_await_timer(90)] waiting?...
      [pam_delay.c:_pam_compute_delay(76)] random number: base=2000000 -> ans=1674256

      [pam_delay.c:_pam_await_timer(114)] will wait 1674256 usec
      [pam_delay.c:_pam_reset_timer(27)] setting pamh->fail_delay.set to FALSE
      [pam_delay.c:_pam_await_timer(126)] waiting done
      [pam_auth.c:pam_authenticate(39)] pam_authenticate exit
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(196)] returning user=admin
      [pam_item.c:pam_set_item(31)] called
      [pam_auth.c:pam_authenticate(18)] pam_authenticate called
      [pam_item.c:pam_set_item(31)] called
      [pam_item.c:pam_set_item(31)] called
      [pam_delay.c:_pam_start_timer(42)] starting timer...
      [pam_handlers.c:_pam_init_handlers(342)] _pam_init_handlers called
      [pam_dispatch.c:_pam_dispatch_aux(106)] passing control to module...
      [pam_item.c:pam_get_item(179)] called.
      [pam_item.c:pam_get_item(201)] returning userprompt=(null)
      [pam_item.c:pam_get_user(281)] called.
      [misc_conv.c:misc_conv(279)] allocating empty response structure array.
      [misc_conv.c:misc_conv(288)] entering conversation function.
      [misc_conv.c:read_string(136)] called with echo='ON', prompt='lnxserver login: '.


      Looking at the source, a check in modules/pam_unix/passverify.c (must be pam_unix.so) is tripping






      authentication pam




      authentication pam






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 5 hours ago







      linuxfan

















      asked 11 hours ago









      linuxfanlinuxfan

      18913




      18913




















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