[Swan] IKEv2 PAM auth failure - how it's done properly?
Mirsad Goran Todorovac
mirsad.todorovac at alu.unizg.hr
Sat Jan 22 10:39:10 EET 2022
Hello Paul,
I have unsuccessfully tried libpam-pkcs11 but it seems to require a card
slot and it didn't work with NSS.
I have succeeded to enable pam_url with SSL on my local web server to
call my CGI-BIN script.
However, I couldn't make it to work with PAM.
However, there seems to be a problem with the default /etc/pam.d/pluto
with libreswan-4.6. It is including system-auth, but system-auth does
not exist in my Debian server's /etc/pam.d . It seems to be sort of a
RedHat thing.
The file is:
% cat /etc/pam.d/pluto
#%PAM-1.0
# Regular System auth
auth include system-auth
#
# Google Authenticator with Regular System auth in combined prompt mode
# (OTP is added to the password at the password prompt without separator)
# auth required pam_google_authenticator.so forward_pass
# auth include system-auth use_first_pass
#
# Common
account required pam_nologin.so
auth sufficient pam_pkcs11.so
account include system-auth
password include system-auth
session optional pam_keyinit.so debug force revoke
session include system-auth
session required pam_loginuid.so
The /etc/pam.d/test for pam_url also calls system-auth:
# cat /etc/pam.d/test
#%PAM-1.0
auth required pam_env.so
auth sufficient /lib64/security/pam_url.so debug
config=/etc/pam_url.conf
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.so
account include system-auth
password include system-auth
session optional pam_keyinit.so revoke
session required pam_limits.so
It seems to be made for local users.
I am going to paste a working system-auth from the web, but it is rather
cumbersome :-P
I feel really confused, as I see none of functions in pam_authenticate
return "yes" or "no". Maybe I was wrong to take it literally.
I have succeeded to make the script be called from pamtester and to
return "200 OK" in case the username is in the permitted access file,
and "400 Bad Request" if it is not.
However, pamtester treats both of these cases as "Authentication failure":
root at domac:/home/admin/mtodorov/build/pam_url# pamtester -v test user1
authenticate
pamtester: invoking pam_start(test, user1, ...)
pamtester: performing operation - authenticate
161.53.235.3 - - [22/Jan/2022:09:35:45 +0100] "POST /cgi-bin/myauth.php
HTTP/2.0" 200 134 "-" "pam_url/0.3.3"
pamtester: Authentication failure
root at domac:/home/admin/mtodorov/build/pam_url# pamtester -v test
notexisting authenticate
pamtester: invoking pam_start(test, notexisting, ...)
pamtester: performing operation - authenticate
161.53.235.3 - - [22/Jan/2022:09:35:58 +0100] "POST /cgi-bin/myauth.php
HTTP/2.0" 400 125 "-" "pam_url/0.3.3"
pamtester: Authentication failure
root at domac:/home/admin/mtodorov/build/pam_url#
I feel like I'm out of options.
pam_url/pam_url.c has this:
if( CURLE_OK != curl_easy_perform(eh) )
goto curl_error;
// No errors
free(post);
curl_easy_cleanup(eh);
curl_global_cleanup();
return PAM_SUCCESS;
so the "200 OK" should be sufficient to authorize, but something
spurious seems to be happening.
I hope I can be given an idea, as I feel I ran out of options.
Kind regards,
Mirsad
On 1/21/2022 5:03 PM, Paul Wouters wrote:
> to use pam, you create or modify /etc/pam.d/pluto
>
> For example, you could change this file to use pam_url as the pam
> module and then run your own REST http server that will receive the
> authorization name and you can write you own code to respond with
> either “yes” or “no”.
>
> This part is not libreswan specific, and you can test your pam module
> using pam_tester and specifying the “pluto” method that will then use
> /etc/pam.d/pluto to perform the check to your backend. Once pam_tester
> works, libreswan should work too.
>
> Paul
>
> Sent using a virtual keyboard on a phone
>
>> On Jan 21, 2022, at 10:44, Mirsad Goran Todorovac
>> <mirsad.todorovac at alu.unizg.hr> wrote:
>>
>>
>>
>> Hello Paul, Manfred,
>>
>> SO far I have located the lines in the source, but I am unable to
>> decypher what these meant to do:
>>
>> pluto/pam-conv.c:
>> 143 what = "pam_start";
>> 144 retval = pam_start("pluto", arg->name, &conv, &pamh);
>> 145 if (retval != PAM_SUCCESS)
>> 146 break;
>> 147 dbg_pam_step(arg, what);
>> 148
>> 149 /* Send the remote host address to PAM */
>> 150 what = "pam_set_item";
>> 151 address_buf rhb;
>> 152 retval = pam_set_item(pamh, PAM_RHOST,
>> str_address(&arg->rhost, &rhb));
>> 153 if (retval != PAM_SUCCESS)
>> 154 break;
>> 155 dbg_pam_step(arg, what);
>> 156
>> 157 /* Two factor authentication - Check that the
>> user is valid,
>> 158 * and then check if they are permitted access
>> 159 */
>> 160 what = "pam_authenticate";
>> 161 retval = pam_authenticate(pamh, PAM_SILENT); /*
>> is user really user? */
>> 162 if (retval != PAM_SUCCESS)
>> 163 break;
>> 164 dbg_pam_step(arg, what);
>> 165
>> 166 what = "pam_acct_mgmt";
>> 167 retval = pam_acct_mgmt(pamh, 0); /* permitted
>> access? */
>> 168 if (retval != PAM_SUCCESS)
>> 169 break;
>> 170 dbg_pam_step(arg, what);
>> 171
>> 172 /* success! */
>> 173 pam_end(pamh, PAM_SUCCESS);
>> 174 return true;
>>
>> From this it appears that the username should be on the PAM side, and
>> not in the ipsec.secret (5) file.
>> But I don't know which file yet. I think that I am rather certain
>> that it shouldn't mess with /etc/passwd, for it doesn't allow spaces
>> in usernames, does it?
>>
>> Mirsad
>>
>> On 21.1.2022. 16:00, Mirsad Goran Todorovac wrote:
>>>
>>> On 21.1.2022. 15:08, Paul Wouters wrote:
>>>
>>>> Hello,
>>>>>> I have installed the IKEv2 VPN connection at my colleague's laptop and he disappointingly noticed that there is no password authentication in addition to certificate.
>>>>>> This is also akward because we would have to change all certificates if i.e. one laptop configured for the Faculty VPN was lost or stolen. :-(
>>>>> I don't think this is right. The certificate system (in general, not libreswan's specifically) is explicitly designed so that you don't have to do that.
>>>>> Ref CRL (Certificate Revocation List).
>>>> Exactly. You only need to revoke the laptop certificate. The CA certificate is on the laptop too but not the CA certificate’s private key, only the public key.
>>>>
>>>> An additional password adds little security assuming there is already a login password, an automatic screen lock after a few minutes and whole disk encryption with a password.
>>>>
>>>> The libreswan pam option for IKEv2 is only meant for the server to check authorization of the client ID (usually a cert), not authentication. This is so you can temporary lock out a user without (irrevocably) revoking their certificate. This is often used when a customer hasn’t paid their bill for instance, or could be used if a laptop is missing but most likely will be found again.
>>>
>>> 1. I agree this opportunity to temporary disable the login with a
>>> certificate would be practical. I have generated the certificates as
>>> proposed on the link:
>>> https://libreswan.org/wiki/VPN_server_for_remote_clients_using_IKEv2#Example_certificate_generation_with_certutil
>>>
>>> export PARM='--keyUsage digitalSignature,keyEncipherment
>>> --extKeyUsage serverAuth,clientAuth'
>>> certutil -S -c "GRF-UNIZG CA" -n "laptop-marko.grf.hr" -s
>>> "O=GRF-UNIZG,CN=laptop-marko.grf.hr" -k rsa -g 4096 -v 12 -d
>>> sql:${HOME}/tmpdb -t ",," ${PARM} -8 "laptop-marko.grf.hr"
>>> pk12util -o laptop-marko.grf.hr.p12 -n "laptop-marko.grf.hr" -d
>>> sql:${HOME}/tmpdb/
>>>
>>> I have imported the cert into Windows 10 certificate manager in the
>>> "Local Machine" keystore.
>>>
>>> I can't seem to understand how to revoke such a local certificate.
>>> It is not generated by Letsencrypt or Sectigo, so where does ipsec
>>> check for revocation lists?
>>>
>>> However, once it is revoked, the damage is done. I can't make it
>>> alive again, can I? So, there is a justified question:
>>>
>>> 2. Can I get a pointer to the username/password file for the
>>> certificates? I don't know if it should be in
>>> /etc/ipsec.d/hostname.secrets, and what is the syntax considering
>>> that the username contains spaces when expanded by certificate check
>>> facility of I think pluto.
>>>
>>> As the username is as it appears in the pluto log, what is the
>>> location and syntax of the password file? And who would provide
>>> password? Windows 10 client or else?
>>>
>>> Jan 20 09:45:03.533787: | PAM: #1: PAM-process completed for user
>>> 'CN=pc-mtodorov.alu.hr, O=ALU-UNIZG' with result FAILURE
>>>
>>> This would be a great feature to have.
>>> However, the manual ipsec.conf (5) only says this:
>>>
>>> pam-authorize
>>>
>>> IKEv1 supports PAM authorization via XAUTH using xauthby=pam.
>>> IKEv2 does not support receiving a plaintext username and
>>> password. Libreswan does not yet support EAP authentication
>>> methods for IKE. The pam-authorize=yes option performs an
>>> authorization call via PAM, but only includes the remote ID (not
>>> username or password). This allows for backends to disallow an
>>> ID based on non-password situations, such as "user disabled" or
>>> "user over quota". See also xauthby=pam
>>>
>>> It is not clear to me which file should provide remote ID list with
>>> permissions? And the syntax.
>>>
>>> My current /etc/pam.d/pluto looks like this:
>>>
>>> root at domac:~# cat /etc/pam.d/pluto
>>> #%PAM-1.0
>>> auth required pam_unix.so
>>> auth required pam_nologin.so
>>> account required pam_unix.so
>>> password required pam_unix.so
>>> session required pam_unix.so
>>> session required pam_loginuid.so
>>> root at domac:~#
>>>
>>> The 4.6 distribution original did not work for me either: it said
>>> simply this:
>>>
>>> Jan 20 09:07:48.551340: "MYCONN-ikev2-cp"[4] 193.198.186.218 #2:
>>> IKEv2 FAILED during pam_authenticate with 'Permission denied' for
>>> state #2, MYCONN-ikev2-cp[4] user=CN=pc-mtodorov.alu.hr, O=ALU-UNIZG.
>>> Jan 20 09:07:48.551600: | PAM: #2: PAM-process completed for user
>>> 'CN=pc-mtodorov.alu.hr, O=ALU-UNIZG' with result FAILURE
>>> Jan 20 09:07:48.552834: | processing signal PLUTO_SIGCHLD
>>> Jan 20 09:07:48.552890: | waitpid returned pid 2652 (exited with
>>> status 1)
>>> Jan 20 09:07:48.552903: | suspend: restoring MD at 0x55f56d8e5aa8 from
>>> state #2 (server_fork_sigchld_handler() +224 programs/pluto/ser
>>> ver_fork.c)
>>> Jan 20 09:07:48.552928: | #2 waited 0.010288 for 'pamauth' fork()
>>> Jan 20 09:07:48.552941: "MYCONN-ikev2-cp"[4] 193.198.186.218 #2:
>>> PAM: authentication of user 'CN=pc-mtodorov.alu.hr, O=ALU-UNIZG'
>>> FAILED after 0.01074 seconds
>>>
>>> I would love this feature to work on my VPN server. Libreswan team
>>> is very motivational for experimenting. As I said before, I felt
>>> moved by the all-inclusive code of conduct for the project :-)
>>>
>>>> The next version of libreswan will add EAPTLS authentication, so windows won’t require administrative rights to add the IKEv2 connection. Once that it is, perhaps another EAP method - mschapv2 - will be added that does add a user / password method that can be used without certificates.
>>> This sounds great. Looking forward to testing it :-)
>>> Kind regards,
>>> Mirsad
>>> --
>>> Mirsad Todorovac
>>> CARNet system engineer
>>> Faculty of Graphic Arts | Academy of Fine Arts
>>> University of Zagreb
>>> Republic of Croatia, the European Union
>>> --
>>> CARNet sistem inženjer
>>> Grafički fakultet | Akademija likovnih umjetnosti
>>> Sveučilište u Zagrebu
>>>
>>> _______________________________________________
>>> Swan mailing list
>>> Swan at lists.libreswan.org
>>> https://lists.libreswan.org/mailman/listinfo/swan
>> --
>> Mirsad Todorovac
>> CARNet system engineer
>> Faculty of Graphic Arts | Academy of Fine Arts
>> University of Zagreb
>> Republic of Croatia, the European Union
>> --
>> CARNet sistem inženjer
>> Grafički fakultet | Akademija likovnih umjetnosti
>> Sveučilište u Zagrebu
>> _______________________________________________
>> Swan mailing list
>> Swan at lists.libreswan.org
>> https://lists.libreswan.org/mailman/listinfo/swan
--
Mirsad Goran Todorovac
CARNet sistem inženjer
Grafički fakultet | Akademija likovnih umjetnosti
Sveučilište u Zagrebu
--
CARNet system engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb, Republic of Croatia
tel. +385 (0)1 3711 451
mob. +385 91 57 88 355
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