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mail encryption

 

 

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cloos at jhcloos

Jan 29, 2008, 11:57 AM

Post #26 of 30 (602 views)
Permalink
Re: mail encryption [In reply to]

The server side of doing this is easy. The client side (both MUA and
user :) may not be.

I suggest doing the encryption at the MTA rather than at the injection.

Use the same methods the various anti-virus, anti-spam, et al systems do
to interact with your MTA. That may be milters for sendmail or postfix,
a content-filter, or something else. Have your filter encrypt each mail
which is to be locally delivered to the recipient's public key.

This will be agnostic to IMAP, POP or any other delivery mechanism.

Then, you have to configure the users' MUAs to support the PK system you
chose (s/mime and openpgp are the obvious options) and train your users
to enter their secret key's passphrase to read their mail.

It would help to have some type of agent or keymanager running, if the
MUA doesn't itself have such support, to save the users from having to
enter the passphrase for each mail.

You might also want to look into a smart card solution, where the key is
on the card rather than on the workstation. There are some which have
the USB keydrive form factor, but most look like flash card readers.

You also can choose to encrypt only locally originated mail.

Having the decryption done on the workstation, even if the encryption
is done on a server, may not be what you -- or your CEO and CFO -- were
envisioning, but it can be done with relative ease.

To have the IMAP server do the decryption is also possible. The
passphrase for the secret key would have to match the IMAP password,
and you'd have to pass it in the clear (as in LOGIN "user" "pass") so
that the daemon could use it to access the secret key. And while it may
be enough security to cover your stated threat model (simple curiosity),
it is only mildly secure, and could lead to future problems were the
users to start relying on it to be really secure. (The false sense of
security problem.) Hacking dbmail's imapd to support that shouldn't be
*too* difficult. But I'd still do the encryption at the MTA.

The important thing to keep in mind when ecrypting on the server is that
you can't be certain that there isn't a backchannel or other munging
which would make it easier to brute-force to resulting cypher text.
A classic attack is to reduce the entropy used to create the session key
(most pki schemes create a random session key, use that with a symmetric
cypher such as AES to encrypt the document, and then encrypt just the
session key with the PK algorithm; this is done because RSA et al are
*slow* compared to AES et al) which significanly reduces the time and
effort required to recover the session key. Again, if your threat model
is just to avoid the curious, that isn't a problem. But you have to
make sure your management understands that they can't go out and claim
their email is secure against threats like corporate or government
espionage. Or even disgruntled (ex-)employees.

And, finally, you may want to invest in some kind of true random number
generator for the server to be sure you don't deplete /dev/random and
DOS the incoming mail.

-JimC
--
James Cloos <cloos [at] jhcloos> OpenPGP: 1024D/ED7DAEA6
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sim at compulab

Jan 29, 2008, 10:28 PM

Post #27 of 30 (598 views)
Permalink
Re: mail encryption [In reply to]

What I am looking for is a way to convince management that someone doing
maintenance on the database will not be able to read all their email.
They understand the intrinsic insecurity of email. They are just trying
to avoid passive intrusion as opposed to active intrusion. One example
is that my system admin, without trying to read anybodys email, was
trying to learn how the tables work, so he opened the tables in a MySQL
viewer and looked at what data was in each table. He wasn't _actively
trying_ to read email, but while doing it he did read email.

However, the 2 requirements are that they can read the message on the
client without having to jump through hoops and that they don't have to
tell everyone who sends them a message that they have to send it
encrypted. Without those 2 things they are going to stay with regular
POP email (not dbmail POP, which still keeps the mails in the database
until cleanup, if I understand correctly).

James Cloos idea of doing the encryption at the MTA is a great idea that
I hadn't thought about. I'm going to investigate the possibility.

Sim


-------- Original Message --------
Subject: [Dbmail] mail encryption
From: Dave Logan <davel [at] dsp-services>
To: DBMail mailinglist <dbmail [at] dbmail>
Date: Tuesday, January 29, 2008 07:08:02 PM
> So, I'm just throwing this out there, are you looking for
> true encryption, or just an obfuscation? For example could
> you do a rot13 or something equivalent? Sure it's not real
> security, and it's easily enough worked around, i.e.
> instead of searching for 'salary' I'd search for the rot13
> value of 'salary'. But maybe it's an extra step that would
> make them (the management) feel more secure. And isn't that
> what this is really about?
> dave
>
>

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casper at bcx

Jan 30, 2008, 3:35 AM

Post #28 of 30 (600 views)
Permalink
Re: mail encryption [In reply to]

Hi Sim,

I think your management is coercing you to do something a lot op the
techies on this mailinglist wouldn't want to implement, simply because
from the technical point of view it has no added value. (except the
perceived value by your management)

If your management is this paranoia about confident emails they receive,
why are you letting them store mail on the server? Wouldn't old-school
POP reduce the 'risks' significantly? That way the security of their
local email is *their* problem. The perceived risks are smaller (while
they in fact they are far larger)

This is the same problem my grandmother had with electronic cash. She
couldn't be convinced that having money on a bankaccount was more safe
than having it on her. The best you can do for your management is
explaining it to them.

As to accidental reading of emails:
- Your mail database will grow fast, with lots of data and not much
information. I don't do an accidental select * from `dbmail_messageblks`
as it gives me too much records to be able to process.
- The messageblk field is a blob. My database editor doesn't show me
data in blob's by default (as it is binary data)
- WHERE `messageblk` LIKE '%salary%' does not count as accidental
reading of mail.

In the Netherlands, intentional reading of an email not sent to you is
prohibited by law. Email is considered mail under the postal law. This
might be the same with you, and it probably is the best way to keep mail
safe.

As pointed out email is never safe.
The dutch company DigiNotar http://www.diginotar.com/ (there must be
many more, this is just a company I know) provides safe transfer of
documents and other such services. (we get our monthly salary statement
from our accountant sent with it)


Good luck!



On Wed, 2008-01-30 at 08:28 +0200, Sim Zacks wrote:

> What I am looking for is a way to convince management that someone doing
> maintenance on the database will not be able to read all their email.
> They understand the intrinsic insecurity of email. They are just trying
> to avoid passive intrusion as opposed to active intrusion. One example
> is that my system admin, without trying to read anybodys email, was
> trying to learn how the tables work, so he opened the tables in a MySQL
> viewer and looked at what data was in each table. He wasn't _actively
> trying_ to read email, but while doing it he did read email.
>
> However, the 2 requirements are that they can read the message on the
> client without having to jump through hoops and that they don't have to
> tell everyone who sends them a message that they have to send it
> encrypted. Without those 2 things they are going to stay with regular
> POP email (not dbmail POP, which still keeps the mails in the database
> until cleanup, if I understand correctly).
>
> James Cloos idea of doing the encryption at the MTA is a great idea that
> I hadn't thought about. I'm going to investigate the possibility.
>
> Sim
>
>
> -------- Original Message --------
> Subject: [Dbmail] mail encryption
> From: Dave Logan <davel [at] dsp-services>
> To: DBMail mailinglist <dbmail [at] dbmail>
> Date: Tuesday, January 29, 2008 07:08:02 PM
> > So, I'm just throwing this out there, are you looking for
> > true encryption, or just an obfuscation? For example could
> > you do a rot13 or something equivalent? Sure it's not real
> > security, and it's easily enough worked around, i.e.
> > instead of searching for 'salary' I'd search for the rot13
> > value of 'salary'. But maybe it's an extra step that would
> > make them (the management) feel more secure. And isn't that
> > what this is really about?
> > dave
> >
> >
>
> _______________________________________________
> DBmail mailing list
> DBmail [at] dbmail
> https://mailman.fastxs.nl/mailman/listinfo/dbmail


mike at mobrien

Feb 4, 2008, 1:56 PM

Post #29 of 30 (593 views)
Permalink
Re: mail encryption [In reply to]

If anyone has any specific needs for a keybase while doing development work
for DBMail, ask and you shall receive. :o)

I should have added earlier that we do have Global PGP keyservers for
'public use' in both the sks and pks regimes as well as the developer
servers in all three regimes (PGP LDAP plus PKS and SKS hkp://) -
sks.keyerver.ca 11371 has a globaly syncronized key base of around 2.53
million ... dbmail.keyserver.ca 11371 sounded kinda nice as a a dedicated
DBMail keyserver :o).


Cheers.
Mike

----- Original Message -----
From: "M. J. [Micheal] OBrien" <mike [at] mobrien>
To: "DBMail mailinglist" <dbmail [at] dbmail>
Sent: Tuesday, January 29, 2008 12:00 AM
Subject: Re: [Dbmail] mail encryption


> Following this thread made me think of a little development resource that
> might be helpful.
>
> I don't know if this helps anyone but I added dbmail to our open pgp
> keyserver cluster. These servers are really only intended for group use,
> like for example a group of all DBMail users. If you are looking for a
> list of every key on the planet, you won't find it here.
>
> hence: dbmail.keyserver.ca
> DBMail users' own keyserver.
> Might be OK for some people. :o)
>
> Learn more at: http://www.dbma.ca/keyserver/ or http://dbmail.keyserver.ca
> ldap://dbmail.keyserver.ca:11371 <http://dbmail.keyserver.ca>
> or
> ldap://keyserver.dbma.ca:11371 <http://keyserver.dbma.ca/>
>
> cheers,
> Mike
>
>
>
>
> Michael Monnerie wrote:
>> On Montag, 28. Januar 2008 Michael luich wrote:
>>
>>> The only REAL answer is to encrypt the message at it's
>>> source and decrypt it at it's destination. And this requires a lot
>>> more than Dbmail can handle alone.
>>>
>>
>> Yes, and it's called PGP or GnuPG. No reason to invent something new.
>>
>> mfg zmi
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> DBmail mailing list
>> DBmail [at] dbmail
>> https://mailman.fastxs.nl/mailman/listinfo/dbmail
>>
> _______________________________________________
> DBmail mailing list
> DBmail [at] dbmail
> https://mailman.fastxs.nl/mailman/listinfo/dbmail
>

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skraps at hushmail

Mar 27, 2012, 2:10 AM

Post #30 of 30 (191 views)
Permalink
Re: mail encryption [In reply to]

if you really wanted you could rewrite dbmail to take advantage of AES
features of mysql.

On 03/27/2012 at 5:03 AM, Reindl Harald wrote:Am 27.03.2012 10:52,
schrieb Pascal Longrais:
>
>
> Hello All,
>
> Is there some way/past experience to automatically crypt user
mail/mime content with tools like PGP?

dbmail is "only" IMAP/POP3/LMTP
mail transport is done by the MTA (postfix, exim....)

however, it does NOT make sense to gpg-crypt mails
on the server - this has to be done in the MUA
(thunderbird, outlook..)

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