PAM Integration

Motivation

For Yocto 1.1 we are working to ensure that PAM (Pluggable Authentication Module) support is consistent and enabled in recipes where it is applicable.

Common configure files

For convenience, list common configure files here:

common-auth

 auth	[success=1 default=ignore]	pam_unix.so nullok_secure
 auth	requisite			pam_deny.so
 auth	required			pam_permit.so

common-account

 account [success=1 new_authtok_reqd=done default=ignore]        pam_unix.so 
 account requisite                       pam_deny.so
 account required                        pam_permit.so

common-password

 password        [success=1 default=ignore]      pam_unix.so obscure sha512
 password        requisite                       pam_deny.so
 password        required                        pam_permit.so

common-session

 session [default=1]                     pam_permit.so
 session requisite                       pam_deny.so
 session required                        pam_permit.so
 session required        pam_unix.so 

common-session-noninteractive

 session [default=1]                     pam_permit.so
 session requisite                       pam_deny.so
 session required                        pam_permit.so
 session required        pam_unix.so 

Recipes with PAM support

The following recipes were identified to have PAM support (some already implemented) on 2011-06-27:

at

• Open issue:
  • It can't be ran by a non-root user, error message is:

Can't signal atd (permission denied)

• Simple ways to verify 'at':

$ at now
$ echo "$msg_to_print" >> /tmp/at_test
$ < ctrl+D >
$ cat /tmp/at_test    # Verify if the message has been there 

• /etc/pam.d/atd - not installed by default, copy it from source code and replace '@include' with appropriate 'module-type include':

auth       required    pam_env.so
auth       include     common-auth
account    include     common-account
session    include     common-session-noninteractive
session    required    pam_limits.so

• test pam plugins
  • pam_env.so

modify /etc/pam.d/atd

auth       required    pam_env.so    debug

modify /etc/security/pam_env.conf, add a test entry such as:

MYNAME          DEFAULT="test-at"

log in /var/log/auth.log:

Jul 11 08:41:22 qemux86 atd[678]: pam_env(atd:setcred): pam_putenv("MYNAME=test-at")

• • pam_limits.so

add line to /etc/security/limits.conf

root    -       nofile  3

'at' job failed, log in /var/log/auth.log:

Jul 11 08:49:42 qemux86 atd[699]: pam_env(atd:setcred): Unable to open config file: /etc/security/pam_env.conf: Too many open files

modify the line:

root    -       nofile  4

'at' job successed, log in /var/log/auth.log:

Jul 11 08:59:59 qemux86 atd[738]: pam_unix(atd:session): session opened for user root by (uid=0)                      
Jul 11 08:59:59 qemux86 atd[738]: pam_unix(atd:session): session closed for user root

consolekit

Consolekit provides a pam plugin module pam_ck_connector.so and not the package that use pam. Drop it.

cronie

• Open issue:
  • Can't run 'crontab' command with non-root user, error message is:

You (test-pam) are not allowed to access to (crontab) because of pam configuration.
Jul 12 02:36:14 qemux86 unix_chkpwd[768]: could not obtain user info (test-pam)

• /etc/pam.d/crond:

account    required   pam_access.so
account    include    password-auth
session    required   pam_loginuid.so
session    include    password-auth
auth       include    password-auth

• /etc/pam.d/password-auth:

auth        required      pam_env.so
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so
account     required      pam_unix.so
account     sufficient    pam_localuser.so
account     sufficient    pam_succeed_if.so uid < 500 quiet
account     required      pam_permit.so
password    requisite     pam_cracklib.so try_first_pass retry=3 type=
password    sufficient    pam_unix.so sha512 shadow nullok try_first_pass use_authtok
password    required      pam_deny.so
session     optional      pam_keyinit.so revoke
session     required      pam_limits.so
-session     optional      pam_systemd.so
session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session     required      pam_unix.so

• test commands:

crontab -e    # establish a crontab jobs and check if it works
crontab -l    # list crontab jobs for current user

• test pam plugins

Verified, test ways and the logs/results please refer to other packages:

• • pam_env.so
  • pam_access.so
  • pam_unix.so
  • pam_permit.so
  • pam_keyinit.so

• • pam_localuser.so

copy '/etc/passwd' to '/tmp/passwd' and delete the entry for 'root'; modify /etc/pam.d/password-auth:

account     requisite    pam_localuser.so file=/tmp/passwd debug

log in /var/log/auth.log:

Jul 12 02:58:51 qemux86 crontab: pam_localuser(crond:account): set filename to "/tmp/passwd"
Jul 12 02:58:51 qemux86 crontab: pam_localuser(crond:account): checking "daemon:x:1:1:daemon:/usr/sbin:/bin/sh "
Jul 12 02:58:51 qemux86 crontab: pam_localuser(crond:account): checking "bin:x:2:2:bin:/bin:/bin/sh "
...

• • pam_succeed_if.so

account requisite pam_succeed_if.so uid > 500 debug

log in /var/log/auth.log:

Jul 12 03:14:14 qemux86 crontab: pam_succeed_if(crond:account): 'uid' resolves to '0'
Jul 12 03:14:14 qemux86 crontab: pam_succeed_if(crond:account): requirement "uid > 500" not met by user "root"

• • pam_loginuid.so

TBD

• • pam_systemd.so

no this module

dropbear

• • For supporting pam in dropbear, we need two steps:
  • Add configuration "--enable-pam"
  • Add patches to open macro definition for supporting in option.h

--- a/ptions.h  2011-07-12 11:32:34.165333202 +0800
+++ b/options.h.new     2011-07-12 11:33:25.757332986 +0800
@@ -149,9 +149,9 @@
  * but there's an interface via a PAM module - don't bother using it otherwise.
  * You can't enable both PASSWORD and PAM. */
-#define ENABLE_SVR_PASSWORD_AUTH
+//#define ENABLE_SVR_PASSWORD_AUTH
 /* PAM requires ./configure --enable-pam */
-/*#define ENABLE_SVR_PAM_AUTH*/
+#define ENABLE_SVR_PAM_AUTH
 #define ENABLE_SVR_PUBKEY_AUTH
 /* Wether to ake public key options in authorized_keys file into account */

• • Test result(dropbeat only support simple authentication, account and auth)
    • Server(account)

(server ip:192.168.7.2)
$touch /etc/pam.d/sshd
account  required     pam_access.so
$vi /etc/security/access.conf
- : root : ALL

• • • Client

$ssh username@server-ip
(Disallow access)

• • • Server(auth)

$vi /etc/pam.d/sshd
 auth include common-auth
$vi /etc/pam.d/common-auth
#auth   [success=1 default=ignore]      pam_unix.so nullok_secure
auth    [success=0 default=ignore]      pam_unix.so debug

• • • Client

$ssh username@server-ip
(Disallow access)

gnome-keyring

• gnome-keyring can't call configuration file like "/etc/pam.d/gnome-keyring" because it is called by other program like "gnome-screensave" and "gdm". If we want test "pam_gnome_keyring.so", we need write .bb files to cross-compile gnome-screensave or gdm.

openssh

• • Absent configuration /etc/pam.d/sshd, we need to add patches. After adding this file, it can support pam function through simple test.
  • Test Result
    • Configuration of sshd

auth       include      common-auth
account    required     pam_nologin.so
account    include      common-account
password   include      common-password
session    optional     pam_keyinit.so force revoke
session    include      common-session
session    required     pam_loginuid.so

• • • auth include common-auth --Server

$echo 'UsePAM no' >>/etc/ssh/sshd_config
$vi /etc/ssh/sshd_config
 PermitEmptyPasswords yes 

Other is as same as sudo

• • • log information

Jul 12 11:16:21 qemux86 sshd[650]: pam_unix(sshd:session): session opened for user test by (uid=0)

• • • account required pam_nologin.so --Server

$touch /etc/nologin

• • • Client

$ssh username@server-ip
(Disallow accession)

• • • log information --Server

Jul 13 01:43:48 qemux86 sshd[672]: Accepted keyboard-interactive/pam for yxf from 192.168.7.1 port 59877 ssh2
Jul 13 01:43:48 qemux86 sshd[672]: fatal: PAM: pam_setcred(): Failure setting user credentia

• • • account include common-account --Server

$vi /etc/ssh/sshd_config
 PermitEmptyPasswords no
$vi /etc/pam.d/common-account 
 #account [success=1 new_authtok_reqd=done default=ignore]        pam_unix.so
 account [success=0 new_authtok_reqd=done default=ignore]        pam_unix.so

• • • Client

$ssh username@server-ip
(Disallow accession)

• • • log information

Jul 13 02:11:24 qemux86 sshd[752]: Failed password for root from 192.168.7.1 port 53784 ssh2

• • • password include common-password

$vi /etc/pam.d/common-password
 password        [success=1 default=ignore]      pam_unix.so obscure sha512 

It's no use for sshd, So no test result for this item

• • • session optional pam_keyinit.so force revoke --Server

No action

• • • Client

$ssh username@server-ip

• • • log information

Jul 13 07:28:18 qemux86 sshd[1132]: pam_keyinit(sshd:session): OPEN 1
Jul 13 07:28:18 qemux86 sshd[1132]: pam_keyinit(sshd:session): UID:1000 [0]  GID:1000 [0]
Jul 13 07:28:18 qemux86 sshd[1132]: pam_keyinit(sshd:session): JOIN = 236576375

• • • Client( the same session as the above "client" )

$exit

• • • log information

Jul 13 07:34:47 qemux86 sshd[1132]: pam_keyinit(sshd:session): CLOSE 1,236576375,1
Jul 13 07:34:47 qemux86 sshd[1132]: pam_keyinit(sshd:session): REVOKE 236576375
Jul 13 07:34:47 qemux86 sshd[1132]: pam_keyinit(sshd:session): UID:1000 [0]  GID:1000 [0]

• • • session include common-session --Server

$vi /etc/pam.d/common-session
 #session [default=1] pam_permit.so
 session [default=0] pam_permit.so

• • • Client

$ssh username@server-ip
(Disallow accession)

• • • log information

Jul 13 05:53:35 qemux86 sshd[960]: error: PAM: pam_open_session(): Permission denied
Jul 13 05:53:35 qemux86 sshd[960]: Received disconnect from 192.168.7.1: 11: disconnected by user

• • • session required pam_loginuid.so --Server(Record user´s login uid to the process attribute)

No action

• • • Client

$ssh username@server-ip

• • • log information

Jul 13 06:31:32 qemux86 sshd[1028]: pam_warn(sshd:session): function=[pam_sm_open_session] service=[sshd] terminal=[ssh] user=[yxf] ruser= [<unknown>] rhost=[ubuntuwindriver.local] 
Jul 13 06:31:32 qemux86 sshd[1028]: pam_unix(sshd:session): session opened for user yxf by (uid=0)

polkit

Polkit includes four binaries. Only pkexec depends on pam. So I use pkexec to make pam test. Pkexec allows an authorized user to execute PROGRAM as another user. If username is not specified, then the program will be executed as the administrative super user, root.

• Pam configuration file of polkit

%PAM-1.0
auth       include      common-auth
account    include      common-account
password   include      common-password
session    include      common-session

• Test Reult
  • • Normally pkexec can call pam modules from the above configuration file

$ pkexec cat /var/log/auth.log 
 ==== AUTHENTICATING FOR org.freedesktop.policykit.exec ===
 Authentication is needed to run `/bin/cat' as the super user
 Authenticating as: root
 Password: <---Input root password and press key "Enter"

Jul 14 22:13:18 emenlow polkitd(authority=local): Registered Authentication Agent for unix-process:2466:778527 (system bus name :1.10 [pkexec  cat /var/log/auth.log], 
object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8)
Jul 14 22:13:18 emenlow polkit-agent-helper-1[2501]: PAM pam_parse: expecting non-zero; [... default=ignore]
Jul 14 22:13:18 emenlow polkit-agent-helper-1[2501]: PAM pam_parse: expecting non-zero; [... default=ignore]
Jul 14 22:13:21 emenlow polkitd(authority=local): Unregistered Authentication Agent for unix-process:2466:778527 (system bus name :1.10,
object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8) (disconnected from bus)
Jul 14 22:13:21 emenlow polkitd(authority=local): Operator of unix-process:2466:778527 FAILED to authenticate to gain authorization for action
org.freedesktop.policykit.exec for unix-process:2466:778527 [sh] (owned by unix-user:yxf)
Jul 14 22:14:37 emenlow polkitd(authority=local): Registered Authentication Agent for unix-process:2466:778527 (system bus name :1.11 [pkexec 
cat /var/log/auth.log], object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8)
Jul 14 22:16:08 emenlow polkitd(authority=local): Operator of unix-process:2466:778527 successfully authenticated as unix-user:root to gain 
ONE-SHOT authorization for action org.freedesktop.policykit.exec for unix-process:2466:778527 [sh] (owned by unix-user:yxf)
Jul 14 22:16:08 emenlow pkexec: pam_unix(polkit-1:session): session opened for user root by root(uid=500)
Jul 14 22:16:08 emenlow pkexec[2507]: yxf: Executing command [USER=root] [TTY=/dev/pts/0] [CWD=/] [COMMAND=/bin/cat /var/log/auth.log]
Jul 14 22:16:08 emenlow polkitd(authority=local): Unregistered Authentication Agent for unix-process:2466:778527 (system bus name :1.11, 
object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8) (disconnected from bus)

• • • auth include common-auth

$vi /etc/pam.d/common-auth
 #auth    [success=1 default=ignore]      pam_unix.so nullok_secure
 auth    [success=0 default=ignore]      pam_unix.so nullok_secure

$ pkexec cat /var/log/auth.log 
==== AUTHENTICATING FOR org.freedesktop.policykit.exec ===
Authentication is needed to run `/bin/cat' as the super user
Authenticating as: root
Password: 
polkit-agent-helper-1: pam_authenticate failed: Permission denied
Error: Permission denied
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized

This incident has been reported.

log information in /var/log/auth.log

Jul 14 22:23:24 emenlow pkexec[2515]: yxf: Error executing command as another user: Not authorized [USER=root] [TTY=/dev/pts/0] [CWD=/] [COMMAND=/bin/cat /var/log/auth.log]

• • • account include common-account

$ vi /etc/pam.d/common-account
#account [success=1 new_authtok_reqd=done default=ignore]        pam_unix.so
account [success=0 new_authtok_reqd=done default=ignore]        pam_unix.so

$ pkexec cat /var/log/auth.log 
==== AUTHENTICATING FOR org.freedesktop.policykit.exec ===
Authentication is needed to run `/bin/cat' as the super user
Authenticating as: root
Password: 
polkit-agent-helper-1: pam_acct_mgmt failed: Permission denied
Error: Permission denied
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized

log information in /var/log/auth.log

Jul 14 22:29:12 emenlow pkexec[2523]: yxf: Error executing command as another user: Not authorized [USER=root] [TTY=/dev/pts/0] [CWD=/] [COMMAND=/bin/cat /var/log/auth.log]

• • • password include common-password

It is no use for polkit. So I don't test it

• • • session include common-session

$ vi /etc/pam.d/common-session
#session [default=1]                     pam_permit.so
session [default=0]                     pam_permit.so

$ pkexec cat /var/log/auth.log 
==== AUTHENTICATING FOR org.freedesktop.policykit.exec ===
Authentication is needed to run `/bin/cat' as the super user
Authenticating as: root
Password: 
==== AUTHENTICATION COMPLETE ===
pam_open_session() failed: Permission denied

log information in /var/log/auth.log

Jul 14 22:35:51 emenlow polkitd(authority=local): Unregistered Authentication Agent for unix-process:2466:778527 (system bus name :1.17, 
object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8)

screen

screen use pam to authenticate users during unlock terminal. Its configure file screen comes from Fedora and replace system-auth with common-auth

 #%PAM-1.0
 auth       include      common-auth

First start screen:

 root@qemux86:/etc/pam.d# screen

it will show some information about screen, just press Space or Enter and it will give a screen terminal:

 root@qemux86:/etc/pam.d# 

then press "Ctrl+a x" will lock the screen terminal and show:

 Screen used by root <root>.
 Password:

In another root terminal, clear the root's password:

 password -d root

modify one line in common-auth

 auth	[success=1 default=ignore]	pam_unix.so nullok_secure

with

 auth	[success=1 default=ignore]	pam_unix.so debug

option nullok_secure will allow users who has blank password login, after remove it these users are not allowed to login.

Back to the screen terminal, press <Enter>(because root's password is blank now) will fail:

 Screen used by root <root>.
 Password:
 Screen used by root <root>.
 Password:

then modify the line in common-auth with

 auth	[success=1 default=ignore]	pam_unix.so nullok_secure debug

On the screen terminal press <Enter> again it unlock the terminal.

the log in /var/log/auth.log:

 Jul 11 14:14:14 qemux86 screen: pam_unix(screen:auth): authentication failure; logname=root uid=0 euid=0 tty= ruser= rhost=  user=root

shadow

chage

/etc/pam.d/chage: need patch to replace system-auth to common-auth

 #%PAM-1.0
 auth		sufficient	pam_rootok.so
 account	required	pam_permit.so
 password	include		common-auth

• test pam_rootok.so

add the only option for pam_rootok.so

 auth		sufficient	pam_rootok.so debug

run command chage as root:

 root@qemux86:/etc/pam.d# chage -m 10  test

log info in /var/log/message shows pam_rootok.so return success:

 Jul 12 06:55:18 qemux86 authpriv.debug chage[575]: pam_rootok(chage:auth): root check succeeded
 Jul 12 06:55:18 qemux86 authpriv.info chage[575]: changed password expiry for test

• test pam_unix.so

the content of common-auth are shown at section "Common configure files"

comment the pam_rootok.so line, because it will make pam return success:

 #auth		sufficient	pam_rootok.so

and modify the pam_unix.so line in common-auth:

 auth	[success=1 default=ignore]	pam_unix.so debug

run commands:

 root@qemux86:/etc/pam.d# passwd -d root 
 root@qemux86:/etc/pam.d# chfn -f testself test # test is a unprivileged user
 Password: 
 chfn: PAM authentication failed

log in /var/log/message:

 Jul 12 07:53:16 qemux86 authpriv.notice chfn[673]: pam_unix(chfn:auth): authentication failure; logname=root uid=0 euid=0 tty= ruser= rhost=  user=root

chfn

/etc/pam.d/chfn

 auth	    sufficient	pam_rootok.so
 auth       include      common-auth
 account    include      common-account
 session    include      common-session

add option debug to pam_rootok.so

 auth	    sufficient	pam_rootok.so debug

• pam_rootok.so

run command chfn as root:

 root@qemux86:/etc/pam.d# chfn -f testyayay test

log info in /var/log/message shows pam_rootok.so return success:

 Jul 12 07:22:59 qemux86 authpriv.debug chfn[638]: pam_rootok(chfn:auth): root check succeeded
 Jul 12 07:22:59 qemux86 authpriv.info chfn[638]: changed user 'test' information

• pam_unix.so

please refer to chage test steps.

chgpasswd

/etc/pam.d/chgpasswd(need patch)

 #%PAM-1.0
 auth		sufficient	pam_rootok.so
 account	required	pam_permit.so
 password	include		system-auth

test pam_rootok.so and pam_unix.so(common-auth) refer to test steps in chage

chpasswd

/etc/pam.d/chpasswd

 password   include      common-password

common-password are listed before, we change the pam_unix.so option:

 password	[success=1 default=ignore]	pam_unix.so  audit

commands to test:

 root@qemux86:/etc/pam.d# chpasswd
 test:
 Press Ctrl+d, the follow are terminal output:
 No password supplied
 No password supplied
 No password supplied
 chpasswd: (user test) pam_chauthtok() failed, error:
 Authentication token manipulation error
 chpasswd: (line 1, user test) password not changed

syslog info:

 Jul 15 04:53:39 qemux86 authpriv.notice chpasswd[844]: pam_warn(chpasswd:auth): function=[pam_sm_authenticate] service=[chpasswd] terminal=[<unknown>] user=[root] ruser=[<unknown>] rhost=[<unknown>]
 Jul 15 04:53:39 qemux86 authpriv.notice chpasswd[844]: pam_warn(chpasswd:account): function=[pam_sm_acct_mgmt] service=[chpasswd] terminal=[<unknown>] user=[root] ruser=[<unknown>] rhost=[<unknown>]
 Jul 15 04:53:41 qemux86 authpriv.debug chpasswd[844]: pam_unix(chpasswd:chauthtok): username [test] obtained
 Jul 15 04:53:41 qemux86 authpriv.debug chpasswd[844]: pam_unix(chpasswd:chauthtok): username [test] obtained
 Jul 15 04:53:41 qemux86 authpriv.debug chpasswd[844]: pam_unix(chpasswd:chauthtok): bad authentication token
 Jul 15 04:53:41 qemux86 authpriv.debug chpasswd[844]: pam_unix(chpasswd:chauthtok): bad authentication token
 Jul 15 04:53:41 qemux86 authpriv.debug chpasswd[844]: pam_unix(chpasswd:chauthtok): bad authentication token
 Jul 15 04:53:41 qemux86 authpriv.notice chpasswd[844]: pam_unix(chpasswd:chauthtok): new password not acceptable

chsh

/etc/pam.d/chsh

 auth       required   pam_shells.so
 auth       sufficient      pam_rootok.so
 auth       include      common-auth
 account    include      common-account
 session    include      common-session

• pam_shells.so

pam_shells only allows access to the system if the users shell is listed in /etc/shells.It also checks if /etc/shells is a plain file and not world writable.

check /etc/shells first:

 qemux86:~$ ls -l /etc/shells 
 -rw-r--r--    1 root     root           109 Jul 12 06:05 /etc/shells
 qemux86:~$ cat /etc/shells
 # /etc/shells: valid login shells
 /bin/sh
 /bin/ash
 /bin/bash
 /bin/dash
 /bin/ksh
 /usr/bin/ksh
 /usr/bin/screen
 qemux86:~$ 

login as a unprivileged user, the correct process is:

 qemux86:~$ chsh -s /bin/ash
 Password: <-- Enter password here
 qemux86:~$ 

syslog info:

 Jul 15 06:15:18 qemux86 authpriv.debug chsh[1283]: pam_rootok(chsh:auth): root check failed
 Jul 15 06:15:21 qemux86 authpriv.info chsh[1283]: changed user 'test' shell to '/bin/ash'

now remove /bin/ash from /etc/shells, then run the same command:

 qemux86:~$ chsh -s /bin/ash
 Password: <-- Enter password here
 chsh: /bin/ash is an invalid shell.
 qemux86:~$ 

if you make /etc/shells is writable to all people, chsh will fail with syslog info:

 Jul 15 05:38:38 qemux86 authpriv.err chsh[1091]: pam_shells(chsh:auth): /etc/shells is either world writable or not a normal file

• pam_rootok.so

modify pam_rootok.so item:

 auth       required     pam_rootok.so debug

then unprivileged users can't change their shell.

 qemux86:~$ chsh -s /bin/ash
 Password: 
 chsh: PAM authentication failed
 qemux86:~$ 

syslog info:

 Jul 15 06:43:14 qemux86 authpriv.debug chsh[1350]: pam_rootok(chsh:auth): root check failed

• pam_unix.so
  • pam_unix in common-auth: please refer to sudo tests
  • pam_unix in common-account and common-password don't have test point.

groupadd

/etc/pam.d/groupadd(need patch)

 #%PAM-1.0
 auth            sufficient      pam_rootok.so
 account         required        pam_permit.so
 password        include         system-auth(common-password)

• pam_rootok

please refer to chage tests

• pam_unix.so in common-password doesn't has test point

groupdel

/etc/pam.d/groupdel(need patch)

 #%PAM-1.0
 auth            sufficient      pam_rootok.so
 account         required        pam_permit.so
 password        include         system-auth(common-password)

• pam_rootok

please refer to chage tests

groupmems

/etc/pam.d/groupmems

 #%PAM-1.0
 auth            sufficient      pam_rootok.so
 account         required        pam_permit.so
 password        include         system-auth(common-password)

• pam_rootok:

refer to chage tests

• pam_unix in common-password doesn't has test point

groupmod

/etc/pam.d/groupmod

1. %PAM-1.0

auth sufficient pam_rootok.so account required pam_permit.so password include common-password

• pam_rootok

refer to chage tests

• pam_unix: FIXME

login

/etc/pam.d/login

 auth       optional   pam_faildelay.so  delay=3000000
 auth       [success=ok ignore=ignore user_unknown=ignore default=die]  pam_securetty.so
 auth       requisite  pam_nologin.so
 session       required   pam_env.so readenv=1
 session       required   pam_env.so readenv=1 envfile=/etc/default/locale
 auth       include      common-auth
 auth       optional   pam_group.so
 session    required   pam_limits.so                                      
 session    optional   pam_lastlog.so                                     
 session    optional   pam_motd.so                              
 session    optional   pam_mail.so standard                    
                                                             
 account    include      common-account                        
 password   include      common-password                       
 session    include      common-session

newusers

/etc/pam.d/newusers

 password   include      common-password

• pam_unix

modify the pam_unix item in common-password

 password        [success=1 default=ignore]      pam_unix.so debug 

run command:

 root@qemux86:~# newusers
 a::::::
 No password supplied
 No password supplied
 No password supplied
 newusers: (user a) pam_chauthtok() failed, error:
 Authentication token manipulation error
 newusers: (line 1, user a) password not changed

syslog info:

 Jul 15 09:50:17 qemux86 authpriv.debug newusers[1560]: pam_unix(newusers:chauthtok): username [a] obtained
 Jul 15 09:50:17 qemux86 authpriv.debug newusers[1560]: pam_unix(newusers:chauthtok): username [a] obtained
 Jul 15 09:50:17 qemux86 authpriv.debug newusers[1560]: pam_unix(newusers:chauthtok): bad authentication token
 Jul 15 09:50:17 qemux86 authpriv.debug newusers[1560]: pam_unix(newusers:chauthtok): bad authentication token
 Jul 15 09:50:17 qemux86 authpriv.debug newusers[1560]: pam_unix(newusers:chauthtok): bad authentication token
 Jul 15 09:50:17 qemux86 authpriv.notice newusers[1560]: pam_unix(newusers:chauthtok): new password not acceptable

passwd

/etc/pam.d/passwd

 password   include      common-password

• pam_unix in common-password

modify the item to make password length not less than 4 characters:

 password        [success=1 default=ignore]      pam_unix.so minlen=4 debug

run test commands:

 qemux86:~$ passwd
 Changing password for test.
 (current) UNIX password: <-- input 123 here
 Enter new UNIX password: 
 Retype new UNIX password: 
 You must choose a longer password
 Enter new UNIX password: <-- input 1234 here
 Retype new UNIX password: 
 passwd: password updated successfully
 qemux86:~$ 

syslog doesn't has detail informatiaon

 Jul 17 02:00:39 qemux86 authpriv.debug passwd[1649]: pam_unix(passwd:chauthtok): username [test] obtained
 Jul 17 02:00:41 qemux86 authpriv.debug passwd[1649]: pam_unix(passwd:chauthtok): username [test] obtained
 Jul 17 02:00:49 qemux86 authpriv.notice passwd[1649]: pam_unix(passwd:chauthtok): password changed for test

su

/etc/pam.d/su

useradd

/etc/pam.d/useradd(need patch)

 #%PAM-1.0
 auth            sufficient      pam_rootok.so
 account         required        pam_permit.so
 password        include         system-auth(common-password)

• pam_rootok

refer to chage tests

• pam_unix in common-password： FIXME

userdel

/etc/pam.d/userdel(need patch)

 #%PAM-1.0
 auth            sufficient      pam_rootok.so
 account         required        pam_permit.so
 password        include         system-auth(common-password)

• pam_rootok

refer to chage tests

• pam_unix in common-password:

no test point

usermod

/etc/pam.d/usermod(need patch)

 #%PAM-1.0
 auth            sufficient      pam_rootok.so
 account         required        pam_permit.so
 password        include         system-auth(common-password)

• pam_rootok

refer to chage tests

• pam_unix in common-password： FIXME

sudo

• /etc/pam.d/sudo comes from Fedora, and replace system-auth with common-auth

 #%PAM-1.0
 auth       include      common-auth
 account    include      common-account
 password   include      common-password
 session    required     pam_keyinit.so revoke
 session    required     pam_limits.so

and content of common-auth has been show above.

• test pam plugins
  • pam_unix.so

modify common-auth:

 auth    [success=1 default=ignore]      pam_unix.so debug

then unpriviledge user can NOT run sudo with blank password

 qemux86:~$ sudo rm /test
 Password:
 Sorry, try again.
 Password:
 Sorry, try again.
 Password:
 Sorry, try again.
 sudo: 3 incorrect password attempts
 qemux86:~$ sudo rm /test
 qemux86:~$

log in /var/log/auth.log:

 Jul  8 16:39:04 qemux86 sudo: pam_unix(sudo:auth): authentication failure; logname=test-pam uid=0 euid=0 tty=/dev/pts/1 ruser=test-pam rhost=  user=test-pam
 Jul  8 16:39:14 qemux86 sudo: test-pam : 3 incorrect password attempts ; TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm /test
 Jul  8 16:39:31 qemux86 sudo: pam_warn(sudo:account): function=[pam_sm_acct_mgmt] service=[sudo] terminal=[/dev/pts/1] user=[test-pam] ruser=[test-pam] rhost=[<unknown>]
 Jul  8 16:39:31 qemux86 sudo: test-pam : TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm /test

• • pam_deny.so

mv line

 auth    requisite                       pam_deny.so

to the head of file, unprivilege user can NOT sudo any more:

 qemux86:~$ sudo rm /test
 Sorry, try again.
 Sorry, try again.
 Sorry, try again.
 sudo: 3 incorrect password attempts
 qemux86:~$

log in /var/log/auth.log:

 Jul  7 14:03:29 qemux86 sudo: test-pam : 3 incorrect password attempts ; TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm /test

• • pam_permit.so

comment this line

 auth    required                        pam_permit.so

sudo will fail without ask user to enter password:

 qemux86:~$ sudo rm /test
 Sorry, try again.
 Sorry, try again.
 Sorry, try again.
 sudo: 3 incorrect password attempts
 qemux86:~$

log in /var/log/auth.log:

 Jul  7 12:43:22 qemux86 sudo: test-pam : 3 incorrect password attempts ; TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm -f /test

• • pam_limits.so

add line to /etc/security/limits.conf

 *        -       nofile       3

then sudo will fail:

 qemux86:~$ sudo rm /test
 Inconsistency detected by ld.so: dl-deps.c: 622: _dl_map_object_deps: Assertion `nlist > 1' failed!

modify the line:

 *        -       nofile       4
 qemux86:~$ sudo rm /test
 qemux86:~$

log in /var/log/auth.log:

 Jul  8 14:24:41 qemux86 sudo: pam_warn(sudo:account): function=[pam_sm_acct_mgmt] service=[sudo] terminal=[/dev/pts/1] user=[test-pam] ruser=[test-pam] rhost=[<unknown>]
 Jul  8 14:24:41 qemux86 sudo: test-pam : TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm /test
 Jul  8 14:24:41 qemux86 sudo: pam_limits(sudo:session): reading settings from '/etc/security/limits.conf'
 Jul  8 14:24:41 qemux86 sudo: pam_limits(sudo:session): process_limit: processing - nofile 3 for DEFAULT
 Jul  8 14:24:50 qemux86 sudo: test-pam : TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm /test
 Jul  8 14:24:50 qemux86 sudo: pam_limits(sudo:session): reading settings from '/etc/security/limits.conf'
 Jul  8 14:24:50 qemux86 sudo: pam_limits(sudo:session): process_limit: processing - nofile 4 for DEFAULT

• • pam_keyinit

add option debug

 session    optional     pam_keyinit.so revoke debug

log shows pam_keyinit was called:

 Jul  7 14:13:39 qemux86 sudo: pam_warn(sudo:account): function=[pam_sm_acct_mgmt] service=[sudo] terminal=[/dev/pts/1] user=[test-pam] ruser=[test-pam] rhost=[<unknown>]
 Jul  7 14:13:39 qemux86 sudo: test-pam : TTY=pts/1 ; PWD=/home/test-pam ; USER=root ; COMMAND=/bin/rm /test
 Jul  7 14:13:39 qemux86 sudo: pam_keyinit(sudo:session): OPEN 1
 Jul  7 14:13:39 qemux86 sudo: pam_keyinit(sudo:session): UID:0 [0]  GID:0 [1000]
 Jul  7 14:13:39 qemux86 sudo: pam_keyinit(sudo:session): GET SESSION = 143761918
 Jul  7 14:13:39 qemux86 sudo: pam_keyinit(sudo:session): GET SESSION = 669161571

according the source code pam_keyinit.c line 102 in function init_keyrings, the module return PAM_SUCCESS

util-linux

Three programs chfn chsh and login in util-linux will use libpam. Right now these programs are provided by package shadow. In util-linux.inc, EXTRA_OECONF has option "--disable-login-utils " which will disable to build them.

Drop it.

Notes

• mc: mc has remove package mcserv and dropped dependency on PAM already, but didn't remove checking security/pam_misc.h. Drop it. Official change log
• libcap: if pam exists, libcap will create a pam plugin pam_cap.so to add a new front end for the authentication function. Because it is not a application, remove it from list.
• libuser: pam is libuser's build dependency, so remove it too.
• The busybox login has a option to use pam, but we use tinylogin's login right now (tinylogin also provides the su command)
• gettext only has a example "hello-c++-kde" use pam under source code directory, and it doen't be compiled and only copied to destination. So omit gettext.
• sysvinit has a patch contrib/notify-pam-dead.patch for /sbin/init to use pam, but the whole contrib directory didn't take part in compilation. Drop it.

Identify upstream PAM patches to use

After checking the Fedora develop repository, the following packages may need patches(only libpam need to upgrade, other patches are pam related configure file but they are absent in poky):

• libpam: need update from current 1.1.3 to 1.1.4 Release Notes
• sudo: package sudo in Fedora provides /etc/pam.d/sudo and /etc/pam.d/sudo-i
  • /etc/pam.d/sudo (Yocto use common-auth instead of system-auth)

 #%PAM-1.0
 auth       include      system-auth
 account    include      system-auth
 password   include      system-auth
 session    optional     pam_keyinit.so revoke
 session    required     pam_limits.so

• screen: check Fedora screen.pam

• util-linux: check Fedora source file util-linux-remote.pamd

• at: check Fedora util-linux-remote.pamd

• cups: check Fedora cups-1.1.16-system-auth.patch

• openssh: check Fedora sshd.pam

PAM Unit Tests

We use unit test cases provided by libpam itself, a subdirectory with name "xtests" under libpam source code.

On build machine run

 bitbake libpam -c patch

to get the libpam source code Linux-PAM-1.1.4, and scp it to host(target) machine.

On the target machine under Linux-PAM-1.1.4, run

 ./configure
 make xtests

will get the test result of 28 unit test case. If you want to run sigle test case, go to subdirectory xtests and run (take tst-pam_time1 for example)

 ./run-xtests.sh . tst-pam_time1

Some unit test can NOT pass(15/28), they need some pam plugin libraies:

• tst-pam_access1
• tst-pam_access2
• tst-pam_access3
• tst-pam_access4
  • the tst-pam_access test cases need pam_access.so, install package pam-plugin-access will make them pass the test
• tst-pam_authsucceed
  • need pam_debug.so, install pam-plugin-debug to make it pass

• tst-pam_cracklib1
• tst-pam_cracklib2
  • need /lib/security/pam_cracklib.so, need build cracklib, and then libpam will check it and create pam-plugin-cracklib
  • need /usr/share/cracklib/pw_dict.pwd file, please run command on host machine:

   create-cracklib-dict /usr/share/cracklib/cracklib-small

• tst-pam_dispatch1
• tst-pam_dispatch2
• tst-pam_dispatch3
• tst-pam_dispatch4
  • need pam_debug.so, install pam-plugin-debug to make tst-pam_dispatch pass

• tst-pam_pwhistory1
  • need /lib/security/pam_pwhistory.so, install pam-plugin-pwhistory to make it pass

• tst-pam_substack2
  • need pam_debug.so, install pam-plugin-debug to make tst-pam_dispatch pass

• tst-pam_succeed_if1
  • install pam-plugin-succeed-if to make it pass

• tst-pam_time1
  • install pam-plugin-time to make it pass