dovecot-SASL for Postfix: EXTERNAL does not work.
Hello.
I am not subscribed and new here, so first of all i want to thank you for dovecot. I personally do not use it in "production" (yet), but it is my sole point of interaction for testing the little MUA i maintain for quite some years. I also have used its code for affirmation purposes. (Interesting that OAUTHBEARER treats hostname and port as optional. I currently do OAUTHBEARER.)
So then i stumbled over GSSAPI not being usable anymore with the latest release, but it seems there is an ML thread with a fix. I have not tried it, i reverted to the last release here, though.
When i implemented EXTERNAL authentication last year i could not figure out how to make postfix+dovecot-SASL work with it. First of all i had to switch configs back and forth, but in the meantime i learned a very nice trick: if i use two password databases
passdb { driver = passwd-file mechanisms = external args = /etc/dovecot/pass-external.db override_fields = nopassword } passdb { driver = passwd-file args = /etc/dovecot/pass.db } userdb { driver = passwd }
which are effectively the same except that one does not have passwords while the other has, i can use EXTERNAL (with and without additional user-via-protocol in combination with auth_ssl_username_from_cert=yes and it just works!
Whereas EXTERNAL works just fine for IMAP and POP3 it does not for SMTP. Last year when i did it i saw a postfix ML thread in action, so i have not looked further into that. Looking again with things unchanged in the postfix 3.5 that they mentioned by then i think, i now posted to the postfix list myself yesterday [1], and it turned out that postfix seems incapable to do something about it, because the dovecot auth protocol does not offer the possibility to specify a valid-user-certificate-seen flag as well as pass the username from the certificate. (Or even pass the entire certificate as a base64 string, less postfix CA, .. or whatever.)
[1] https://marc.info/?l=postfix-users&m=159785887710910&w=2
What is really terrible with the current situation is that postfix announces the EXTERNAL, with Wietse Venema saying
Short summary: Postfix does not implement a single iota of SASL AUTH support. Postfix simply propagates the names of mechanisms that the backend (Cyrus or Dovecot) claims to support, and Postfix proxies requests and responses between the remote SMTP client and the SASL backend. Postfix has no idea what SASL mechanisms are, including EXTERNAL. It just proxies stuff.
If Dovecot claims to support SASL EXTERNAL but does not handle it, that that is a bit of a WTF.
It would be tremendous to have true EXTERNAL support all through, i personally really like EXTERNAL, i would rather have some password-protected crytographically secured certificates in my local store, and have client certificates in all the IoT devices, than have to mess around with the OAUTH that the major players press forward, for example.
Thanks, and Ciao from Germany,
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
Hello and good evening.
Sorry for responding so late, it is midsummer and i spend as much time as possible on the outside (bicycle, mostly). (Just one more day, then 10 degrees colder!!)
I Cc: Wietse Venema, because i quote a message of him. (this is "set quote-add-cc" here.)
Aki Tuomi wrote in 84881193.5398.1597934431687@appsuite-dev-gw2.open-xchange.com:
The dovecot mail archive removed your HTML message :) (And given code like
<div> </div> <div> </div> <div> Hello. </div> <div> </div> <div> I am not subscribed and new here, so first of all i want to thank </div> <div> you for dovecot. I personally do not use it in "production" </div>
it was right in doing so :-)
||On 20/08/2020 17:28 Steffen Nurpmeso <[1]steffen@sdaoden.eu[/1]> wrote: ... ||What is really terrible with the current situation is that postfix | ||announces the EXTERNAL, with Wietse Venema saying
It seems he has read the dovecot documentation again in the meantime, different to me :(, so i have to apologise for saying
|[1], and it turned out that postfix seems incapable to do |something about it, because the dovecot auth protocol does not |offer the possibility to specify a valid-user-certificate-seen |flag as well as pass the username from the certificate. (Or even |pass the entire certificate as a base64 string, less postfix CA, |.. or whatever.)
because Wietse Venema now says
Wietse Venema wrote in
4BXSTk189nzJrP3@spike.porcupine.org:
...
|Steffen Nurpmeso:
...
|> until SASL says it is done?!. How could EXTERNAL ever work like
|> that in a client/server->auth-server situation?
|
|There's a chicken and egg question in there somewhere.
|
|https://wiki1.dovecot.org/Authentication%20Protocol mentions
|two attributes that might be relevant, and that Postfix can send:
|
|secured
| Remote user has secured transport to auth client] (eg. localhost,
| SSL, TLS)
|
|valid-client-cert
| Remote user has presented a valid SSL certificate.
|
|But these are booleans. What protocol attribute would Postfix use
|to pass certificate name information (and which name, as there
|can be any number of them)?
|
| Wietse
| Wietse
--End of 4BXSTk189nzJrP3@spike.porcupine.org
I think i will spend some time tomorrow and try to do some coding with postfix. Let's see wether the immediate response of EXTERNAL can work with dovecot's SASL, even in conjunction with auth_ssl_username_from_cert=yes that is! Otherwise i think what he says here.
|You could try out dovecot submission service. It should work better
|with EXTERNAL.
For the internal test network this may really be an option. But for my web vm: ach, i am not an administrator, it is pain to get used to all that. In real life i use the DMA here, and external mail goes via my MUA through ssh only:
set mta=/usr/bin/ssh set mta-arguments='steffen@sdaoden.eu /usr/sbin/sendmail -t' set mta-argv0=ssh
That sendmail is postfix, then. And there is such a tremendous amount of noise in the logs of postfix and the lighttpd web server that are available easily from the network, it is terrible. Even with very rigid firewall rules, and things like postfix's error limits, junk command limit, record deadlines, timeouts, active sleeping in restrictions ... And for now i would not even know whether dovecot has equivalents, nor how to apply this correctly. These are all very capable and highly configurable applications. dovecot for example, i track the source for a couple of years, comes with 568 files changed, 26488 insertions(+), 6969 deletions(-) for my last update (v2.3.10.1 to v2.3.11.3). This is a lot.
Thank you. And Ciao! and good night from Germany,
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
On 21/08/2020 02:17 Steffen Nurpmeso steffen@sdaoden.eu wrote:
Hello and good evening.
Sorry for responding so late, it is midsummer and i spend as much time as possible on the outside (bicycle, mostly). (Just one more day, then 10 degrees colder!!)
I Cc: Wietse Venema, because i quote a message of him. (this is "set quote-add-cc" here.)
Aki Tuomi wrote in 84881193.5398.1597934431687@appsuite-dev-gw2.open-xchange.com:
The dovecot mail archive removed your HTML message :) (And given code like
<div> </div> <div> </div> <div> Hello. </div> <div> </div> <div> I am not subscribed and new here, so first of all i want to thank </div> <div> you for dovecot. I personally do not use it in "production" </div>
it was right in doing so :-)
||On 20/08/2020 17:28 Steffen Nurpmeso <[1]steffen@sdaoden.eu[/1]> wrote: ... ||What is really terrible with the current situation is that postfix | ||announces the EXTERNAL, with Wietse Venema saying
It seems he has read the dovecot documentation again in the meantime, different to me :(, so i have to apologise for saying
|[1], and it turned out that postfix seems incapable to do |something about it, because the dovecot auth protocol does not |offer the possibility to specify a valid-user-certificate-seen |flag as well as pass the username from the certificate. (Or even |pass the entire certificate as a base64 string, less postfix CA, |.. or whatever.)
because Wietse Venema now says
Wietse Venema wrote in 4BXSTk189nzJrP3@spike.porcupine.org: ... |Steffen Nurpmeso: ... |> until SASL says it is done?!. How could EXTERNAL ever work like |> that in a client/server->auth-server situation? | |There's a chicken and egg question in there somewhere. | |https://wiki1.dovecot.org/Authentication%20Protocol mentions |two attributes that might be relevant, and that Postfix can send: | |secured | Remote user has secured transport to auth client] (eg. localhost,
| SSL, TLS) | |valid-client-cert | Remote user has presented a valid SSL certificate. | |But these are booleans. What protocol attribute would Postfix use |to pass certificate name information (and which name, as there |can be any number of them)? | | Wietse | Wietse --End of 4BXSTk189nzJrP3@spike.porcupine.orgI think i will spend some time tomorrow and try to do some coding with postfix. Let's see wether the immediate response of EXTERNAL can work with dovecot's SASL, even in conjunction with auth_ssl_username_from_cert=yes that is! Otherwise i think what he says here.
|You could try out dovecot submission service. It should work better
|with EXTERNAL.For the internal test network this may really be an option. But for my web vm: ach, i am not an administrator, it is pain to get used to all that. In real life i use the DMA here, and external mail goes via my MUA through ssh only:
set mta=/usr/bin/ssh set mta-arguments='steffen@sdaoden.eu /usr/sbin/sendmail -t' set mta-argv0=ssh
That sendmail is postfix, then. And there is such a tremendous amount of noise in the logs of postfix and the lighttpd web server that are available easily from the network, it is terrible. Even with very rigid firewall rules, and things like postfix's error limits, junk command limit, record deadlines, timeouts, active sleeping in restrictions ... And for now i would not even know whether dovecot has equivalents, nor how to apply this correctly. These are all very capable and highly configurable applications. dovecot for example, i track the source for a couple of years, comes with 568 files changed, 26488 insertions(+), 6969 deletions(-) for my last update (v2.3.10.1 to v2.3.11.3). This is a lot.
Thank you. And Ciao! and good night from Germany,
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
I was trying to suggest that you could try dovecot submission server. It might work better with EXTERNAL authentication.
Aki
Aki Tuomi wrote in
1907575568.4364.1597984769802@appsuite-dev-gw1.open-xchange.com:
|> On 21/08/2020 02:17 Steffen Nurpmeso steffen@sdaoden.eu wrote:
...
|> Wietse Venema wrote in
|> 4BXSTk189nzJrP3@spike.porcupine.org:
|> ...
|>|Steffen Nurpmeso:
|> ...
|>|> until SASL says it is done?!. How could EXTERNAL ever work like
|>|> that in a client/server->auth-server situation?
...
|>|https://wiki1.dovecot.org/Authentication%20Protocol mentions
|>|two attributes that might be relevant, and that Postfix can send:
|>|
|>|secured
|>| Remote user has secured transport to auth client] (eg. localhost,
|>| SSL, TLS)
|>|
|>|valid-client-cert
|>| Remote user has presented a valid SSL certificate.
|>|
|>|But these are booleans. What protocol attribute would Postfix use
|>|to pass certificate name information (and which name, as there
|>|can be any number of them)?
...
|I was trying to suggest that you could try dovecot submission server.
|It might work better with EXTERNAL authentication.
Ok, thanks. Yes, i just faked it for my tests, carrying over the IMAP/POP3 communication. (I use your output as a template and do stuff like
smtp_script smtp -Ssmtp-config=-all,starttls,externanon \
-Stls-config-pairs=Certificate=client-pair.pem
{ smtp_ehlo && printf '\001STARTTLS \003 220 2.0.0 Ready to start TLS ' && smtp_ehlo 0 && printf '\001 AUTH EXTERNAL = ' && smtp_auth_ok && smtp_go; } | ../net-test -U -s .t.sh > "${MBOX}" 2>&1 check auth-7 0 "${MBOX}" '4294967295 0'
you know. Terrible this does not work for GSSAPI, i am about to ask the MIT people to add two pseudo credentials, one which always works and one which does not, so that automatic testing is possible at all, and via unpriviledged account!)
But wouldn't this be an improvement, extending the protocol so that it announces a fingerprint checksum digest, which then can be used in return to report client certificate fingerprints to the dovecot auth server? Like that even client certificate verification could be handled by dovecot auth, aka via SASL, and administrators would have to take care for one user database only?
Other than that i say Ciao from Germany!
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
On 21/08/2020 17:56 Steffen Nurpmeso steffen@sdaoden.eu wrote:
Aki Tuomi wrote in 1907575568.4364.1597984769802@appsuite-dev-gw1.open-xchange.com: |> On 21/08/2020 02:17 Steffen Nurpmeso steffen@sdaoden.eu wrote: ... |> Wietse Venema wrote in |> 4BXSTk189nzJrP3@spike.porcupine.org: |> ... |>|Steffen Nurpmeso: |> ... |>|> until SASL says it is done?!. How could EXTERNAL ever work like |>|> that in a client/server->auth-server situation? ... |>|https://wiki1.dovecot.org/Authentication%20Protocol mentions |>|two attributes that might be relevant, and that Postfix can send: |>| |>|secured |>| Remote user has secured transport to auth client] (eg. localhost,
|>| SSL, TLS) |>| |>|valid-client-cert |>| Remote user has presented a valid SSL certificate. |>| |>|But these are booleans. What protocol attribute would Postfix use |>|to pass certificate name information (and which name, as there |>|can be any number of them)? ... |I was trying to suggest that you could try dovecot submission server.
|It might work better with EXTERNAL authentication.Ok, thanks. Yes, i just faked it for my tests, carrying over the IMAP/POP3 communication. (I use your output as a template and do stuff like
smtp_script smtp -Ssmtp-config=-all,starttls,externanon \ -Stls-config-pairs=Certificate=client-pair.pem { smtp_ehlo && printf '\001STARTTLS \003 220 2.0.0 Ready to start TLS ' && smtp_ehlo 0 && printf '\001 AUTH EXTERNAL = ' && smtp_auth_ok && smtp_go; } | ../net-test -U -s .t.sh > "${MBOX}" 2>&1 check auth-7 0 "${MBOX}" '4294967295 0'
you know. Terrible this does not work for GSSAPI, i am about to ask the MIT people to add two pseudo credentials, one which always works and one which does not, so that automatic testing is possible at all, and via unpriviledged account!)
But wouldn't this be an improvement, extending the protocol so that it announces a fingerprint checksum digest, which then can be used in return to report client certificate fingerprints to the dovecot auth server? Like that even client certificate verification could be handled by dovecot auth, aka via SASL, and administrators would have to take care for one user database only?
Other than that i say Ciao from Germany!
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
On 21/08/2020 17:56 Steffen Nurpmeso steffen@sdaoden.eu wrote:
Aki Tuomi wrote in 1907575568.4364.1597984769802@appsuite-dev-gw1.open-xchange.com: |> On 21/08/2020 02:17 Steffen Nurpmeso steffen@sdaoden.eu wrote: ... |> Wietse Venema wrote in |> 4BXSTk189nzJrP3@spike.porcupine.org: |> ... |>|Steffen Nurpmeso: |> ... |>|> until SASL says it is done?!. How could EXTERNAL ever work like |>|> that in a client/server->auth-server situation? ... |>|https://wiki1.dovecot.org/Authentication%20Protocol mentions |>|two attributes that might be relevant, and that Postfix can send: |>| |>|secured |>| Remote user has secured transport to auth client] (eg. localhost,
|>| SSL, TLS) |>| |>|valid-client-cert |>| Remote user has presented a valid SSL certificate. |>| |>|But these are booleans. What protocol attribute would Postfix use |>|to pass certificate name information (and which name, as there |>|can be any number of them)? ... |I was trying to suggest that you could try dovecot submission server.
|It might work better with EXTERNAL authentication.Ok, thanks. Yes, i just faked it for my tests, carrying over the IMAP/POP3 communication. (I use your output as a template and do stuff like
smtp_script smtp -Ssmtp-config=-all,starttls,externanon \ -Stls-config-pairs=Certificate=client-pair.pem { smtp_ehlo && printf '\001STARTTLS \003 220 2.0.0 Ready to start TLS ' && smtp_ehlo 0 && printf '\001 AUTH EXTERNAL = ' && smtp_auth_ok && smtp_go; } | ../net-test -U -s .t.sh > "${MBOX}" 2>&1 check auth-7 0 "${MBOX}" '4294967295 0'
you know. Terrible this does not work for GSSAPI, i am about to ask the MIT people to add two pseudo credentials, one which always works and one which does not, so that automatic testing is possible at all, and via unpriviledged account!)
But wouldn't this be an improvement, extending the protocol so that it announces a fingerprint checksum digest, which then can be used in return to report client certificate fingerprints to the dovecot auth server? Like that even client certificate verification could be handled by dovecot auth, aka via SASL, and administrators would have to take care for one user database only?
Other than that i say Ciao from Germany!
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
Sorry for duplicate mail, I accidentically pressed too many keys... *sigh*
Anyways, I'm not sure if you understood my point, I ment, have you tried EXTERNAL auth with https://doc.dovecot.org/admin_manual/submission_server/ ?
Aki
(I removed Wietse Venema from Cc:.)
Aki Tuomi wrote in 1972528099.4900.1598022980955@appsuite-dev-gw1.open-xchange.com: ... |Sorry for duplicate mail, I accidentically pressed too many keys... *sigh*
Sure.
|Anyways, I'm not sure if you understood my point, I ment, have you
|tried EXTERNAL auth with https://doc.dovecot.org/admin_manual/submission\
|_server/ ?
No, i never did. I had to look into this, i do not think this is applicable? LMTP? The dovecot submission server, ok, as a frontend for postfix, this is what you mean? No, i have not done this yet. Start postfix on a different local port as a submission_relay_host= target, then start dovecot submission on :25, :587 and :465. I will try this out, thanks for the suggestion.
Ciao from Germany,
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
Just another reminder..
https://github.com/dovecot/core/pull/86
This will allow plugins to make 'capability' advertisements more dynamic..
On 2020-08-21 7:56 a.m., Steffen Nurpmeso wrote:
Aki Tuomi wrote in 1907575568.4364.1597984769802@appsuite-dev-gw1.open-xchange.com: |> On 21/08/2020 02:17 Steffen Nurpmeso steffen@sdaoden.eu wrote: ... |> Wietse Venema wrote in |> 4BXSTk189nzJrP3@spike.porcupine.org: |> ... |>|Steffen Nurpmeso: |> ... |>|> until SASL says it is done?!. How could EXTERNAL ever work like |>|> that in a client/server->auth-server situation? ... |>|https://wiki1.dovecot.org/Authentication%20Protocol mentions |>|two attributes that might be relevant, and that Postfix can send: |>| |>|secured |>| Remote user has secured transport to auth client] (eg. localhost,
|>| SSL, TLS) |>| |>|valid-client-cert |>| Remote user has presented a valid SSL certificate. |>| |>|But these are booleans. What protocol attribute would Postfix use |>|to pass certificate name information (and which name, as there |>|can be any number of them)? ... |I was trying to suggest that you could try dovecot submission server.
|It might work better with EXTERNAL authentication.Ok, thanks. Yes, i just faked it for my tests, carrying over the IMAP/POP3 communication. (I use your output as a template and do stuff like
smtp_script smtp -Ssmtp-config=-all,starttls,externanon \ -Stls-config-pairs=Certificate=client-pair.pem { smtp_ehlo && printf '\001STARTTLS \003 220 2.0.0 Ready to start TLS ' && smtp_ehlo 0 && printf '\001 AUTH EXTERNAL = ' && smtp_auth_ok && smtp_go; } | ../net-test -U -s .t.sh > "${MBOX}" 2>&1 check auth-7 0 "${MBOX}" '4294967295 0'
you know. Terrible this does not work for GSSAPI, i am about to ask the MIT people to add two pseudo credentials, one which always works and one which does not, so that automatic testing is possible at all, and via unpriviledged account!)
But wouldn't this be an improvement, extending the protocol so that it announces a fingerprint checksum digest, which then can be used in return to report client certificate fingerprints to the dovecot auth server? Like that even client certificate verification could be handled by dovecot auth, aka via SASL, and administrators would have to take care for one user database only?
Other than that i say Ciao from Germany!
--steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)
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participants (3)
-
Aki Tuomi
-
Michael Peddemors
-
Steffen Nurpmeso