Dovecot proxy: authentication best practices

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Dovecot proxy: authentication best practices

William Edwards
Hi!

I have a few questions regarding Dovecot proxy:

1.
1.1 If I understand correctly, setting 'nopassword' in the proxy passdb file, authentication is completely up to the destination host. Setting 'nopassword' in no way means the proxy becomes an open relay. Is this correct?
1.2 Are there any security implications when using 'nopassword' on the proxy?

2.
2.1 I would like to avoid having to store all users in a passdb file on the proxy. I would much rather specify a domain for which Dovecot proxy will route all users to a specific host. Is there a way to let Dovecot proxy route to a destination host based on domain, so individual users don't have to be specified in the proxy passdb?
2.2 Is it correct that userdb does not have any effect on proxying and it can be left out of the config? Source: https://dovecot.org/pipermail/dovecot/2013-October/093138.html (point 2)

Met vriendelijke groeten,

William Edwards
T. 040 - 711 44 96



 
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Re: Dovecot proxy: authentication best practices

Aki Tuomi-3

On 27/12/2019 16:02 William Edwards <[hidden email]> wrote:


Hi!

I have a few questions regarding Dovecot proxy:

1.
1.1 If I understand correctly, setting 'nopassword' in the proxy passdb file, authentication is completely up to the destination host. Setting 'nopassword' in no way means the proxy becomes an open relay. Is this correct?

You still control where it proxies to.
1.2 Are there any security implications when using 'nopassword' on the proxy?

As long as its really a proxy, probably no.
2.
2.1 I would like to avoid having to store all users in a passdb file on the proxy. I would much rather specify a domain for which Dovecot proxy will route all users to a specific host. Is there a way to let Dovecot proxy route to a destination host based on domain, so individual users don't have to be specified in the proxy passdb?
2.2 Is it correct that userdb does not have any effect on proxying and it can be left out of the config? Source: https://dovecot.org/pipermail/dovecot/2013-October/093138.html (point 2)
userdb is ignored on proxies. For your usecase try following

passdb {
  driver = passwd-file
  args = username_format=%Ld /etc/dovecot/domains.passwd
}

and into domains.passwd

domain.com::::::: nopassword proxy host=host1

colon count might be wrong
Met vriendelijke groeten,

William Edwards
T. 040 - 711 44 96
---
Aki Tuomi
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Re[2]: Dovecot proxy: authentication best practices

William Edwards
Hi Aki,

> 1.1 If I understand correctly, setting 'nopassword' in the proxy passdb file, authentication is completely up to the destination host. Setting 'nopassword' in no way means the proxy becomes an open relay. Is this correct?
> You still control where it proxies to.
> 1.2 Are there any security implications when using 'nopassword' on the proxy?
> As long as its really a proxy, probably no.

Ok, so assuming proper authentication is configured on the destination host, the answer to 1.1 is 'yes' and the answer to 1.2 is 'no'.

> userdb is ignored on proxies. For your usecase try following
> and into domains.passwd

Ah, yes, of course. I forgot Dovecot supports multiple passdb backends. I have added the domains.passwd backend as a fallback.

Thanks!

Met vriendelijke groeten,

William Edwards
T. 040 - 711 44 96



 

----- Original Message -----

From: Aki Tuomi ([hidden email])
Date: 12/27/19 17:42
To: William Edwards ([hidden email]), dovecot ([hidden email])
Subject: Re: Dovecot proxy: authentication best practices


On 27/12/2019 16:02 William Edwards <[hidden email]> wrote:


Hi!

I have a few questions regarding Dovecot proxy:

1.
1.1 If I understand correctly, setting 'nopassword' in the proxy passdb file, authentication is completely up to the destination host. Setting 'nopassword' in no way means the proxy becomes an open relay. Is this correct?

You still control where it proxies to.
1.2 Are there any security implications when using 'nopassword' on the proxy?

As long as its really a proxy, probably no.
2.
2.1 I would like to avoid having to store all users in a passdb file on the proxy. I would much rather specify a domain for which Dovecot proxy will route all users to a specific host. Is there a way to let Dovecot proxy route to a destination host based on domain, so individual users don't have to be specified in the proxy passdb?
2.2 Is it correct that userdb does not have any effect on proxying and it can be left out of the config? Source: https://dovecot.org/pipermail/dovecot/2013-October/093138.html (point 2)
userdb is ignored on proxies. For your usecase try following

passdb {
  driver = passwd-file
  args = username_format=%Ld /etc/dovecot/domains.passwd
}

and into domains.passwd

domain.com::::::: nopassword proxy host=host1

colon count might be wrong
Met vriendelijke groeten,

William Edwards
T. 040 - 711 44 96
---
Aki Tuomi