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Strategies for protecting IMAP (e.g. MFA)
by Kees van Vloten 14 Nov '21

14 Nov '21

Apart from a really nice firewall firehol also supplies a good set of ip-blacklists. For public exposure of email ports, I am using the combination of firehol-firewall, firehol-blacklist, fail2ban and a whitelist based on geo-ip. The mail-client ports exposed are 993 and 465, because starttls is considered flawed nowadays: https://nostarttls.secvuln.info/) Full access from any IP (except firehol-blacklist and fail2ban) is possible over VPN (openvpn) with MFA (privacyidea). Privacyidea also supplies a mobile-app compatible with a.o. TOTP and HOTP but it provides a more secure way of enrollment (2-step). Thanks for pointing at crowdsec.net, will see if it can tighten security further in cooperation with the above. - Kees On 14-11-2021 11:33, infoomatic wrote: > I will throw in a few interesting projects which have kept my small > servers safe: > > *) firehol.org > > *) crowdsec.net > > *) www.fail2ban.org > > Have a look at those interesting projects! > > > On 13.11.21 22:16, Tyler Montney wrote: >> With the world of ransomware as it is today (aka attacks seem more >> vicious and commonplace), anything I expose to WAN must have >> additional protection. I've seen a few posts to this list on it. The >> only thing that helped was that Dovecot supports OAuth. Through OAuth >> I figure I could implement MFA. However, I'd have to host my own >> identity server. From there, Thunderbird supports OAuth so that should >> work. >> >> Since this is getting increasingly complicated, I wanted to ask before >> going further. What do you all do? Any recommendations?

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Re: Strategies for protecting IMAP (e.g. MFA)
by Marc 14 Nov '21

14 Nov '21

Don't use email addresses as login ;) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -. F1 Outsourcing Development Sp. z o.o. Poland t: +48 (0)12 4207 835 e: marc(a)f1-outsourcing.eu

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IPv4/v6 based access checking and logging
by Lefteris Tsintjelis 13 Nov '21

13 Nov '21

Hi, I am currently using postfix/dovecot with postfix admin and I track the last login date already by using this: https://doc.dovecot.org/configuration_manual/lastlogin_plugin/ Besides last login date, I would like to also implement IPv4 and IPv6 last login tracking also and if possible, IP based login checking. Is post-login scripting the best most efficient way to go? Regards, Lefteris

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2.3.17 update breaks dsync over tcps: Received invalid SSL certificate unable to get certificate CRL
by Salatiel Filho 12 Nov '21

12 Nov '21

Hi, I have updated dovecot from 2.3.16 (working flawless ) to 2.3.17 ( both Centos8 - community repo ) . Now dsync does not work anymore, logs shows: dovecot[30398]: doveadm(vmail): Error: Disconnected from remote: Received invalid SSL certificate: unable to get certificate CRL: /CN=imap.signed.with.my.own.ca(check ssl_client_ca_* settings?) I have a certificate signed by my "own CA". Both hosts trust my CA, and as I told previously, the configuration works just fine on 2.3.16. I really was not expecting that a minor update would break things, but 2.3.17 appears to have broken the setup for some people here in the maillists. Is there a workaround for this? I have tried to set ssl_require_crl = no , but nothing changed. I have: service doveadm { inet_listener { port = 26 ssl = yes } } ssl = required ssl_ca = </etc/ssl/certs/mail-cluster-communication_ca.pem ssl_cert = </etc/ssl/certs/mail-cluster-communication.crt ssl_key = # hidden, use -P to show it Thanks! Atenciosamente/Kind regards, Salatiel

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after replication with compression quotas are wrong
by Arnaud Abélard 12 Nov '21

12 Nov '21

Hello, We are very long time happy dovecot users (since 2008 at least). We have around 90k mailboxes and since we had to move away from our NAS storage to a ceph storage I jumped on the opportunity to enable compression with the zlib plugin and dovecot's replication mecanism. We are using debian's dovecot 2.2.27 packages on production and our new server is running dovecot's own ce-2.3.17 packages. On the production server everything works fine but on the new server, replicated mailboxes' quota is all wrong: on production: # doveadm quota get -u dummy-c-1 Quota name Type Value Limit % Quota Utilisateur STORAGE 660026 976563 67 Quota Utilisateur MESSAGE 8651 - 0 on new server: doveadm quota get -u dummy-c-1 Quota name Type Value Limit % Quota Utilisateur STORAGE 1125251 976563 115 Quota Utilisateur MESSAGE 16646 - 0 If I add all the S flag from the filenames n both servers I get exactly the same usage, which is coherent with the quota on the production server: # find . -type f | grep 'S=' | awk -F'S=' '{print $2}' | awk -F',' '{print $1}' | awk -F':' '{print $1}' | paste -sd+ | bc -l 675865938 And I have exactly the same amountof mails on the two server, the replication works as expected, no unwanted duplication of mails occurs. Of course, I've tried to ask dovecot to recalculate quotas with doveadm quota recalc -u <username>, but it doesn't fix the problem. What am I missing? Thanks, Arnaud PS: Here is my doveconf -n output: # 2.3.17 (e2aa53df5b): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.17 (054dddfa) # OS: Linux 4.19.0-18-amd64 x86_64 Debian 10.11 # Hostname: gromel-test auth_cache_size = 10 k auth_verbose = yes disable_plaintext_auth = no doveadm_password = # hidden, use -P to show it hostname = gromel1.univ-nantes.prive lda_mailbox_autosubscribe = yes listen = * log_timestamp = "%Y-%m-%d %H:%M:%S " login_trusted_networks = (...) mail_gid = 5000 mail_location = maildir:%h mail_plugins = quota zlib notify replication mail_privileged_group = vmail mail_uid = 5000 maildir_stat_dirs = yes maildir_very_dirty_syncs = yes managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext namespace { inbox = yes location = prefix = INBOX. separator = . type = private } passdb { args = /etc/dovecot/dovecot-ldap.conf driver = ldap } plugin { quota = maildir:Quota Utilisateur quota_exceeded_message = Cet utilisateur a dépassé son quota, votre message n'a pu lui être livré. quota_full_tempfail = yes quota_rule = *:storage=1000M quota_rule2 = INBOX.Trash:storage=+100M sieve = ~/dovecot.sieve sieve_dir = ~/sieve sieve_extensions = -vacation sieve_global_dir = /var/lib/dovecot/sieve/global/ sieve_max_redirects = 1 zlib_save = gz zlib_save_level = 6 } postmaster_address = postmaster@<snip> protocols = imap pop3 sieve replication_max_conns = 50 service auth { client_limit = 49452 unix_listener auth-userdb { group = vmail mode = 0600 user = vmail } user = root } service dict { unix_listener dict { mode = 0600 user = vmail } } service doveadm { inet_listener { port = 12345 } } service imap-login { process_min_avail = 8 service_count = 0 user = mail } service imap { executable = imap process_limit = 16384 vsz_limit = 2 G } service managesieve-login { inet_listener sieve { port = 4190 } process_min_avail = 8 service_count = 0 user = mail vsz_limit = 2 G } service managesieve { drop_priv_before_exec = yes process_limit = 16384 } service pop3-login { process_min_avail = 8 service_count = 0 user = mail } service pop3 { drop_priv_before_exec = yes process_limit = 16384 } ssl = no userdb { args = /etc/dovecot/dovecot-ldap.conf driver = ldap } verbose_proctitle = yes protocol imap { mail_max_userip_connections = 50 mail_plugins = quota zlib notify replication imap_quota zlib } protocol pop3 { mail_plugins = quota zlib notify replication } protocol sieve { mail_max_userip_connections = 10 } protocol lda { mail_plugins = quota zlib notify replication sieve zlib } -- Arnaud Abélard Responsable pôle Système et Stockage Service Infrastructures DSIN Université de Nantes -

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2.3.17: Panic on LMTP deliveries
by Michael Glaus 12 Nov '21

12 Nov '21

Hello Since the doevcot update to 2.3.17 i get a panic if a mail is delivered with lmtp. In the logs i get these messages: lmtp(rcpt(a)example.com)<21067><AtxaKh+hi2FLUgAAwujwpQ>: Error: lmtp-server: conn 10.0.0.105:52981 [1]: rcpt rcpt(a)example.com: duplicate db: User rcpt(a)example.com doesn't have home dir set, disabling duplicate database lmtp(rcpt(a)example.com)<21067><AtxaKh+hi2FLUgAAwujwpQ>: Panic: file imem.c: line 65 (i_strconcat): assertion failed: (str1 != NULL) lmtp(rcpt(a)example.com)<21067><AtxaKh+hi2FLUgAAwujwpQ>: Fatal: master: service(lmtp): child 21067 killed with signal 6 (core dumped) In the running config userdb does not return the field “home” and therefor a user does not have a “mail_home” only a “mail_location”. If i change the config to provide a “mail_home” it works, but due to the directory structure i can not change this yet. Best regards Michael Glaus Junior System Administrator -- Hostpoint AG Neue Jonastrasse 60 | 8640 Rapperswil-Jona | Schweiz michael.glaus(a)hostpoint.ch | www.hostpoint.ch

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Userdb problem
by Erwan David 11 Nov '21

11 Nov '21

Hello I am trying to move authentication from ldap to passwdfile. Autentication works, but clients do not find the mails. With ldap I have : root@email:~ # doveadm auth login erwan xxxxx passdb: erwan auth succeeded extra fields: user=erwan userdb extra fields: erwan home=/var/db/mailboxes/erwan /var/db/mailboxes/erwan=/var/db/mailboxes/erwan uid=587 gid=587 auth_mech=PLAIN With passwdfile I get root@email:~ # doveadm auth login erwan xxxxx passdb: erwan auth succeeded extra fields: user=erwan userdb extra fields: erwan home=/var/db/mailboxes/erwan,uid=587,gid=587 uid=587 gid=587 auth_mech=PLAIN The only difference is this "/var/db/mailboxes/erwan=/var/db/mailboxes/erwan" (which is the place where email is stored). What is the problem with this ? auth configuration is : passdb { driver = passwd-file args = scheme=SHA512-CRYPT username_format=%n /usr/local/etc/dovecot/users } userdb { driver = passwd-file args = username_format=%n /usr/local/etc/dovecot/users # Default fields that can be overridden by passwd-file #default_fields = quota_rule=*:storage=1G default_fields = home=/var/db/mailboxes/%n,uid=587,gid=587 # Override fields from passwd-file #override_fields = home=/home/virtual/%u override_fields = home=/var/db/mailboxes/%n,uid=587,gid=587 }

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Question about sieves
by João Silva 10 Nov '21

10 Nov '21

Hi I'm having a problem related to Dovecot (version 2.2.36) sieves and I'm not finding information. I'm calling a sieve with 90-sieve.conf: imapsieve_mailbox2_name = * 90-sieve.conf: imapsieve_mailbox2_from = SPAM 90-sieve.conf: imapsieve_mailbox2_causes = COPY 90-sieve.conf: imapsieve_mailbox2_before = file:/etc/dovecot/sieve/learn-ham.sieve The SPAM folder have a autoexpunge set. From the log analysis I have a very strong suspect that the sieve is being called when the mails from the Spam folder are expunged, is that possible? Is any other imapsieve_mailbox2_causes that could be used to prevent that? Thanks

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dovecot: 2.3.16 -> 2.3.17_1
by Elise 10 Nov '21

10 Nov '21

Hi team, perhaps I do overlook something here, but after the update from 2.3.16 -> 2.3.17_1on startup Dovecot is generating error message: > doveconf: Fatal: execvp(/usr/local/sbin/dovecot) failed: Argument list too long > /usr/local/etc/rc.d/dovecot: WARNING: failed to start dovecot As a temporary solution I currently hashed out SSL in dovecot.conf and receive e-mail again. Can you tell how to fix? Thanks! /elise

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Dovecot Proxy with OAuth2 Setting Question
by UMETSU HARUYASU(梅津　晴康) 08 Nov '21

08 Nov '21

Hi I'm setting up a Dovecot Proxy Server to access Gmail. But It doesn’t work. I tried to configure Dovecot without proxy authentication. passdb { driver = static args = nopasssword=y proxy=y proxy_mech=xoauth2 ... } It works fine. So far so good. But with proxy authentication It does not work. Many clients don't support Oauth2, so Dovecot needs to authenticate for them. Please tell me how to set up Dovecot Proxy with OAuth2. Reference https://doc.dovecot.org/configuration_manual/authentication/oauth2/ Dovecot 2.3.8 HAL Pyoco

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