[Bitcoin-development] Bitcoin Core trial balloon: splitting blockchain engine and wallet

Jeff Garzik jgarzik at bitpay.com
Fri Feb 21 06:50:35 UTC 2014

RE "doesn't buy you anything"   Today, when unlocked, plaintext
private keys reside in the same address space as the blockchain engine
(BCE).  Process separation increases the difficulty of accessing key
data from the BCE, even presuming a normal, no-chroot, same-uid,
parent-child process relationship.  The attack surface is clearly
changed from "one buffer overflow can touch this data."

Regardless, the split makes sense given existing modularity and coding
directions.  I wouldn't micro-focus on the "sandbox" word.

On Fri, Feb 21, 2014 at 1:27 AM, Mike Hearn <mike at plan99.net> wrote:
> Bear in mind a separate process doesn't buy you anything without a sandbox,
> and those are expensive (in terms of complexity).
> On 21 Feb 2014 11:40, "Jeff Garzik" <jgarzik at bitpay.com> wrote:
>> [Meta: "Bitcoin Core" is the newfangled branding of bitcoind /
>> Bitcoin-Qt reference implementation, in case you wondering.]
>> Several sites, including BitPay, use bitcoind outside the standard
>> role of wallet software.  bitcoind can be used purely for payment
>> network access and management.  I call this the "border router" role.
>> Upcoming version 0.9 will feature the ability to disable the bitcoind
>> wallet at compile time or runtime. This permits a more optimized
>> border router profile, reducing process size by 40-200MB according to
>> some reports.
>> Recent IRC discussion have floated a rough proposal for a wallet
>> next-step:  Running the Bitcoin Core wallet as a separate process, a
>> separate binary, from the blockchain engine.  The wallet process would
>> communicate with the blockchain engine using existing RPC and P2P
>> channels, becoming a real SPV client.  This accomplishes a
>> longstanding security goal of sandboxing away wallet keys and
>> sensitive data from the network-exposed P2P engine, in a separate
>> process, among other benefits.
>> Simple forking was explored a bit.  I did some hacking in that
>> direction, as it seemed potentially lightweight and somewhat easy to
>> me: https://github.com/jgarzik/bitcoin/tree/fork  fork+pipe is fine
>> for Linux and OSX/BSD.  However, Windows requires an exec-like
>> solution to create a new process.  MSDN does give us a Unix-pipe-like
>> solution:
>> http://msdn.microsoft.com/en-us/library/edze9h7e%28v=vs.80%29.aspx
>>  Others pointed to boost interprocess communication APIs, which come
>> with their own set of caveats.  Such a solution would involve a brand
>> new IPC protocol, and lots of brand new glue code.
>> Separate programs seems better.  Windows forces us to achieve process
>> separation via exec-like method.  We already have IPC: RPC + P2P.
>> Modern OS's make localhost sockets just about as fast as other IPCs
>> methods.  Linux, at least, employs zero-copy for localhost sockets in
>> many situations, similar to the kernel's pipe tricks.
>> Pieter has been working on headers-first sync:
>> https://github.com/bitcoin/bitcoin/pull/2964  Moving along this
>> wallet/blockchain engine split requires upping the review&test
>> bandwidth on Pieter's PRs, such as
>> https://github.com/bitcoin/bitcoin/pull/3514
>> Unsure how much of the separate-binary discussion Gavin saw, so cc'd
>> for emphasis.
>> --
>> Jeff Garzik
>> Bitcoin core developer and open source evangelist
>> BitPay, Inc.      https://bitpay.com/
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Jeff Garzik
Bitcoin core developer and open source evangelist
BitPay, Inc.      https://bitpay.com/

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