dovecot - Mar 2017 - Dovecot 2.2.27 proxy - enforcing per client IP connection limits

Hi,

mail_max_userip_connections is only enforced at the backend level. The setting
has no effect on proxy. If you want to force the limit then you can only do it
in the backend.

Sami
> On 9 Mar 2017, at 12.05, Adi Pircalabu <adi at ddns.com.au> wrote:
> 
> Quick follow-up: updated the proxies to 2.2.28, but I still couldn't
find a way to limit the inbound IMAP connections per IP & username. I know
"mail_max_userip_connections" limit works for the mail stores, but it
doesn't seem to have any effect on the proxies. I'm using a mix of
Dovecot & Courier-IMAP servers as backends.
> Basically I need to find a way to enforce the maximum limit for the
username<>remoteip so that, if I have:
> ESTCONNS=`doveadm -f flow proxy list | grep "username=usern at
domain.com.proto=imap" | wc -l`
> $ESTCONNS is lower or equal than the configured limit.
> The proxies are configured as per
https://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy to forward the
password to the remote server using MySQL. In dovecot-sql.conf.ext I have:
> password_query = SELECT NULL AS password, 'Y' as nopassword, host,
email as email, 'any-cert' as 'starttls', 'Y' AS proxy
FROM mailbox WHERE email = '%u' AND disabled_smtpauth=0
> 
> At the moment the only way I can limit the number of established
connections per source IP address on the Dovecot proxies is using iptables,
which isn't what I want.
> Where else can I look?
> 
> Adi Pircalabu, System Administrator
> DDNS, a Total Internet Company
> 159 Barkly Avenue, Burnley, Vic 3121, T +61 3 9815 6868
> 
> On 08/03/17 12:32, Adi Pircalabu wrote:
>> Hi,
>> Trying to keep abusive/buggy IMAP clients at bay on a number of Dovecot
proxy servers, I've reconfigured them to use
"mail_max_userip_connections = 50" in the "protocol imap"
section, followed by restarting Dovecot. Yet, I'm still seeing 160+
established connections from a single IP address for the same email account. Am
I missing anything?
>> # 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
>> # Pigeonhole version 0.4.16 (fed8554)
>> # OS: Linux 2.6.32-642.4.2.el6.x86_64 x86_64 CentOS release 6.8 (Final)
>> auth_cache_negative_ttl = 5 mins
>> auth_cache_size = 16 M
>> auth_cache_ttl = 18 hours
>> default_client_limit = 6120
>> default_process_limit = 500
>> managesieve_notify_capability = mailto
>> managesieve_sieve_capability = fileinto reject envelope
encoded-character vacation subaddress comparator-i;ascii-numeric relational
regex imap4flags copy include variables body enotify environment mailbox date
index ihave duplicate mime foreverypart extracttext imapflags notify
>> mbox_write_locks = fcntl
>> namespace inbox {
>>   inbox = yes
>>   location >>   mailbox Drafts {
>>     special_use = \Drafts
>>   }
>>   mailbox Junk {
>>     special_use = \Junk
>>   }
>>   mailbox Sent {
>>     special_use = \Sent
>>   }
>>   mailbox "Sent Messages" {
>>     special_use = \Sent
>>   }
>>   mailbox Trash {
>>     special_use = \Trash
>>   }
>>   prefix >> }
>> passdb {
>>   args = /etc/dovecot/dovecot-sql.conf.ext
>>   driver = sql
>> }
>> plugin {
>>   sieve = file:~/sieve;active=~/.dovecot.sieve
>>   sieve_extensions = +notify +imapflags
>> }
>> protocols = imap pop3 lmtp sieve
>> service auth {
>>   client_limit = 6120
>> }
>> service imap-login {
>>   process_limit = 2048
>>   process_min_avail = 20
>>   service_count = 0
>>   vsz_limit = 256 M
>> }
>> service imap {
>>   process_limit = 2048
>> }
>> service managesieve-login {
>>   inet_listener sieve {
>>     port = 4190
>>   }
>>   service_count = 0
>>   vsz_limit = 128 M
>> }
>> service managesieve {
>>   process_limit = 1024
>> }
>> service pop3 {
>>   process_limit = 1024
>> }
>> [...]
>> protocol imap {
>>   imap_capability = IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE
>>   mail_max_userip_connections = 50
>> }

Thanks,

I thought this might be the case. Is there any solution to enforce this 
on the proxy? If not, will a feature request be considered anytime soon? 
I see the proxies as the first line of defense against IMAP "abuse"
and
I think it's consistent having the same configurable option available on 
both backends and the proxies.

---
Adi Pircalabu

On 14-03-2017 20:17, Sami Ketola wrote:
> Hi,
> 
> mail_max_userip_connections is only enforced at the backend level. The
> setting has no effect on proxy. If you want to force the limit then
> you can only do it in the backend.
> 
> Sami
> 
>> On 9 Mar 2017, at 12.05, Adi Pircalabu <adi at ddns.com.au>
wrote:
>> 
>> Quick follow-up: updated the proxies to 2.2.28, but I still
couldn't
>> find a way to limit the inbound IMAP connections per IP & username.
I
>> know "mail_max_userip_connections" limit works for the mail
stores,
>> but it doesn't seem to have any effect on the proxies. I'm
using a mix
>> of Dovecot & Courier-IMAP servers as backends.
>> Basically I need to find a way to enforce the maximum limit for the 
>> username<>remoteip so that, if I have:
>> ESTCONNS=`doveadm -f flow proxy list | grep 
>> "username=usern at domain.com.proto=imap" | wc -l`
>> $ESTCONNS is lower or equal than the configured limit.
>> The proxies are configured as per 
>> https://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy to 
>> forward the password to the remote server using MySQL. In 
>> dovecot-sql.conf.ext I have:
>> password_query = SELECT NULL AS password, 'Y' as nopassword,
host,
>> email as email, 'any-cert' as 'starttls', 'Y'
AS proxy FROM mailbox
>> WHERE email = '%u' AND disabled_smtpauth=0
>> 
>> At the moment the only way I can limit the number of established 
>> connections per source IP address on the Dovecot proxies is using 
>> iptables, which isn't what I want.
>> Where else can I look?
>> 
>> Adi Pircalabu, System Administrator
>> DDNS, a Total Internet Company
>> 159 Barkly Avenue, Burnley, Vic 3121, T +61 3 9815 6868
>> 
>> On 08/03/17 12:32, Adi Pircalabu wrote:
>>> Hi,
>>> Trying to keep abusive/buggy IMAP clients at bay on a number of 
>>> Dovecot proxy servers, I've reconfigured them to use 
>>> "mail_max_userip_connections = 50" in the "protocol
imap" section,
>>> followed by restarting Dovecot. Yet, I'm still seeing 160+ 
>>> established connections from a single IP address for the same email
>>> account. Am I missing anything?
>>> # 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
>>> # Pigeonhole version 0.4.16 (fed8554)
>>> # OS: Linux 2.6.32-642.4.2.el6.x86_64 x86_64 CentOS release 6.8 
>>> (Final)
>>> auth_cache_negative_ttl = 5 mins
>>> auth_cache_size = 16 M
>>> auth_cache_ttl = 18 hours
>>> default_client_limit = 6120
>>> default_process_limit = 500
>>> managesieve_notify_capability = mailto
>>> managesieve_sieve_capability = fileinto reject envelope 
>>> encoded-character vacation subaddress comparator-i;ascii-numeric 
>>> relational regex imap4flags copy include variables body enotify 
>>> environment mailbox date index ihave duplicate mime foreverypart 
>>> extracttext imapflags notify
>>> mbox_write_locks = fcntl
>>> namespace inbox {
>>>   inbox = yes
>>>   location >>>   mailbox Drafts {
>>>     special_use = \Drafts
>>>   }
>>>   mailbox Junk {
>>>     special_use = \Junk
>>>   }
>>>   mailbox Sent {
>>>     special_use = \Sent
>>>   }
>>>   mailbox "Sent Messages" {
>>>     special_use = \Sent
>>>   }
>>>   mailbox Trash {
>>>     special_use = \Trash
>>>   }
>>>   prefix >>> }
>>> passdb {
>>>   args = /etc/dovecot/dovecot-sql.conf.ext
>>>   driver = sql
>>> }
>>> plugin {
>>>   sieve = file:~/sieve;active=~/.dovecot.sieve
>>>   sieve_extensions = +notify +imapflags
>>> }
>>> protocols = imap pop3 lmtp sieve
>>> service auth {
>>>   client_limit = 6120
>>> }
>>> service imap-login {
>>>   process_limit = 2048
>>>   process_min_avail = 20
>>>   service_count = 0
>>>   vsz_limit = 256 M
>>> }
>>> service imap {
>>>   process_limit = 2048
>>> }
>>> service managesieve-login {
>>>   inet_listener sieve {
>>>     port = 4190
>>>   }
>>>   service_count = 0
>>>   vsz_limit = 128 M
>>> }
>>> service managesieve {
>>>   process_limit = 1024
>>> }
>>> service pop3 {
>>>   process_limit = 1024
>>> }
>>> [...]
>>> protocol imap {
>>>   imap_capability = IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE
IDLE
>>>   mail_max_userip_connections = 50
>>> }

On 16 Mar 2017, at 0.14, Adi Pircalabu <adi at ddns.com.au>
wrote:
> 
> I thought this might be the case. Is there any solution to enforce this on
the proxy? If not, will a feature request be considered anytime soon? I see the
proxies as the first line of defense against IMAP "abuse" and I think
it's consistent having the same configurable option available on both
backends and the proxies.
No plans to support enforcing at proxy level. One problem here is that there are
no guarantees that the connections even end up in the same proxies, although I
guess if your load balancer does IP stickiness that could work well enough.

Hi,

It would be quite hard to enforce a limit at the proxy level since the proxies
do not share any information. Currently I do not know any way of enforcing a
limit at the proxies already.

Sami
> On 16 Mar 2017, at 7.14, Adi Pircalabu <adi at ddns.com.au> wrote:
> 
> Thanks,
> 
> I thought this might be the case. Is there any solution to enforce this on
the proxy? If not, will a feature request be considered anytime soon? I see the
proxies as the first line of defense against IMAP "abuse" and I think
it's consistent having the same configurable option available on both
backends and the proxies.
> 
> ---
> Adi Pircalabu
> 
> On 14-03-2017 20:17, Sami Ketola wrote:
>> Hi,
>> mail_max_userip_connections is only enforced at the backend level. The
>> setting has no effect on proxy. If you want to force the limit then
>> you can only do it in the backend.
>> Sami
>>> On 9 Mar 2017, at 12.05, Adi Pircalabu <adi at ddns.com.au>
wrote:
>>> Quick follow-up: updated the proxies to 2.2.28, but I still
couldn't find a way to limit the inbound IMAP connections per IP &
username. I know "mail_max_userip_connections" limit works for the
mail stores, but it doesn't seem to have any effect on the proxies. I'm
using a mix of Dovecot & Courier-IMAP servers as backends.
>>> Basically I need to find a way to enforce the maximum limit for the
username<>remoteip so that, if I have:
>>> ESTCONNS=`doveadm -f flow proxy list | grep "username=usern at
domain.com.proto=imap" | wc -l`
>>> $ESTCONNS is lower or equal than the configured limit.
>>> The proxies are configured as per
https://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy to forward the
password to the remote server using MySQL. In dovecot-sql.conf.ext I have:
>>> password_query = SELECT NULL AS password, 'Y' as
nopassword, host, email as email, 'any-cert' as 'starttls',
'Y' AS proxy FROM mailbox WHERE email = '%u' AND
disabled_smtpauth=0
>>> At the moment the only way I can limit the number of established
connections per source IP address on the Dovecot proxies is using iptables,
which isn't what I want.
>>> Where else can I look?
>>> Adi Pircalabu, System Administrator
>>> DDNS, a Total Internet Company
>>> 159 Barkly Avenue, Burnley, Vic 3121, T +61 3 9815 6868
>>> On 08/03/17 12:32, Adi Pircalabu wrote:
>>>> Hi,
>>>> Trying to keep abusive/buggy IMAP clients at bay on a number of
Dovecot proxy servers, I've reconfigured them to use
"mail_max_userip_connections = 50" in the "protocol imap"
section, followed by restarting Dovecot. Yet, I'm still seeing 160+
established connections from a single IP address for the same email account. Am
I missing anything?
>>>> # 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
>>>> # Pigeonhole version 0.4.16 (fed8554)
>>>> # OS: Linux 2.6.32-642.4.2.el6.x86_64 x86_64 CentOS release 6.8
(Final)
>>>> auth_cache_negative_ttl = 5 mins
>>>> auth_cache_size = 16 M
>>>> auth_cache_ttl = 18 hours
>>>> default_client_limit = 6120
>>>> default_process_limit = 500
>>>> managesieve_notify_capability = mailto
>>>> managesieve_sieve_capability = fileinto reject envelope
encoded-character vacation subaddress comparator-i;ascii-numeric relational
regex imap4flags copy include variables body enotify environment mailbox date
index ihave duplicate mime foreverypart extracttext imapflags notify
>>>> mbox_write_locks = fcntl
>>>> namespace inbox {
>>>>  inbox = yes
>>>>  location >>>>  mailbox Drafts {
>>>>    special_use = \Drafts
>>>>  }
>>>>  mailbox Junk {
>>>>    special_use = \Junk
>>>>  }
>>>>  mailbox Sent {
>>>>    special_use = \Sent
>>>>  }
>>>>  mailbox "Sent Messages" {
>>>>    special_use = \Sent
>>>>  }
>>>>  mailbox Trash {
>>>>    special_use = \Trash
>>>>  }
>>>>  prefix >>>> }
>>>> passdb {
>>>>  args = /etc/dovecot/dovecot-sql.conf.ext
>>>>  driver = sql
>>>> }
>>>> plugin {
>>>>  sieve = file:~/sieve;active=~/.dovecot.sieve
>>>>  sieve_extensions = +notify +imapflags
>>>> }
>>>> protocols = imap pop3 lmtp sieve
>>>> service auth {
>>>>  client_limit = 6120
>>>> }
>>>> service imap-login {
>>>>  process_limit = 2048
>>>>  process_min_avail = 20
>>>>  service_count = 0
>>>>  vsz_limit = 256 M
>>>> }
>>>> service imap {
>>>>  process_limit = 2048
>>>> }
>>>> service managesieve-login {
>>>>  inet_listener sieve {
>>>>    port = 4190
>>>>  }
>>>>  service_count = 0
>>>>  vsz_limit = 128 M
>>>> }
>>>> service managesieve {
>>>>  process_limit = 1024
>>>> }
>>>> service pop3 {
>>>>  process_limit = 1024
>>>> }
>>>> [...]
>>>> protocol imap {
>>>>  imap_capability = IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE
IDLE
>>>>  mail_max_userip_connections = 50
>>>> }