From: | Joe Conway <mail(at)joeconway(dot)com> |
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To: | Stephen Frost <sfrost(at)snowman(dot)net>, Ryan Lambert <ryan(at)rustprooflabs(dot)com> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Antonin Houska <ah(at)cybertec(dot)at>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, "Moon, Insung" <Moon_Insung_i3(at)lab(dot)ntt(dot)co(dot)jp>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS) |
Date: | 2019-07-10 11:27:47 |
Message-ID: | 4cd16419-7715-7627-9ea9-ae26f82780e5@joeconway.com |
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Lists: | pgsql-hackers |
On 7/9/19 10:06 PM, Stephen Frost wrote:
> Greetings,
>
> * Ryan Lambert (ryan(at)rustprooflabs(dot)com) wrote:
>> > What I think Tomas is getting at here is that we don't write a page only
>> > once.
>>
>> > A nonce of tableoid+pagenum will only be unique the first time we write
>> > out that page. Seems unlikely that we're only going to be writing these
>> > pages once though- what we need is a nonce that's unique for *every
>> > write* of the 8k page, isn't it? As every write of the page is going to
>> > be encrypting something new.
>>
>> > With sufficient randomness, we can at least be more likely to have a
>> > unique nonce for each 8K write. Including the LSN seems like it'd be a
>> > possible alternative.
>>
>> Agreed. I know little of the inner details about the LSN but what I read
>> in [1] sounds encouraging in addition to tableoid + pagenum.
>>
>> [1] https://www.postgresql.org/docs/current/datatype-pg-lsn.html
>
> Yes, but it's still something that we'd have to store somewhere- the
> actual LSN of the page is going to be in the 8K block.
>
> Unless we decide that we can pull the LSN *out* of the 8K block and
> store it unencrypted, and then store the *rest* of the block
> encrypted... That might also allow things like backup software to work
> on these encrypted data files for page-level backups without needing
> access to the key and that'd be pretty neat.
>
> Of course, as with anything, the more data you expose, the higher the
> overall risk that someone can figure out some meaning from it. Still,
> if the idea was that we'd use the LSN in this way, then it'd need to be
> stored unencrypted regardless...
I don't think we are going to be able to eliminate every possible
side-channel anyway -- this seems like a good compromise to me.
Joe
--
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