[Swan] IKEv2 PAM auth failure - how it's done properly?
Paul Wouters
paul at nohats.ca
Fri Jan 21 18:03:57 EET 2022
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.libreswan.org/pipermail/swan/attachments/20220121/edeb178f/attachment.htm>
More information about the Swan
mailing list