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

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

[Jeff Garzik]

[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/

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

[Mike Hearn]

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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@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/
>
>
> ------------------------------------------------------------------------------
> Managing the Performance of Cloud-Based Applications
> Take advantage of what the Cloud has to offer - Avoid Common Pitfalls.
> Read the Whitepaper.
>
> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>

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

[Wladimir]

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On Fri, Feb 21, 2014 at 7:27 AM, Mike Hearn <mike@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).
>
Sandboxing in user space is complex, agreed,

The most straightforward way would be to run the blockchain daemon as a
system service (with its own uid/gid and set of Apparmor/SELinux
restrictions) and the wallet daemon as the user.

This would also allow sharing one blockchain daemon between multiple users
and wallet processes (not necessarily on the same machine), something I've
wanted to be able to do for a long time.

Wladimir

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

[William Yager]

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Running the network part of the core as a system service might make sense for server implementations, but it’s a pain in the rear for most users. 

That said, I think segregating the two processes is a great idea. Let’s just try to avoid some complicated scheme that involves necessarily running things under multiple users.

Will

On Feb 21, 2014, at 0:43, Wladimir <laanwj@gmail.com> wrote:

> The most straightforward way would be to run the blockchain daemon as a system service (with its own uid/gid and set of Apparmor/SELinux restrictions) and the wallet daemon as the user.


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

[Wladimir]

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On Fri, Feb 21, 2014 at 7:50 AM, William Yager <will.yager@gmail.com> wrote:

> Running the network part of the core as a system service might make sense
> for server implementations, but it’s a pain in the rear for most users.
>

Come on, making it a possibility doesn't affect other kinds of use cases in
any way. Are you just arguing for the sake of arguing?

Wladimir

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

[Dustin D. Trammell]

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On Fri, 2014-02-21 at 07:43 +0100, Wladimir wrote:
> The most straightforward way would be to run the blockchain daemon as
> a system service (with its own uid/gid and set of Apparmor/SELinux
> restrictions) and the wallet daemon as the user.

This assumes you as a user have the rights to do so.  This would be
preferred, but in some cases may not be possible.  Perhaps it should be
optional?

> This would also allow sharing one blockchain daemon between multiple
> users and wallet processes (not necessarily on the same machine),
> something I've wanted to be able to do for a long time.

Agreed (:

-- 
Dustin D. Trammell
dtrammell@dustintrammell.com
http://www.dustintrammell.com

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

[Wladimir]

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On Sat, Feb 22, 2014 at 2:09 AM, Dustin D. Trammell <
dtrammell@dustintrammell.com> wrote:

> On Fri, 2014-02-21 at 07:43 +0100, Wladimir wrote:
> > The most straightforward way would be to run the blockchain daemon as
> > a system service (with its own uid/gid and set of Apparmor/SELinux
> > restrictions) and the wallet daemon as the user.
>
> This assumes you as a user have the rights to do so.  This would be
> preferred, but in some cases may not be possible.  Perhaps it should be
> optional?
>

No! I'm proposing that we force everyone to do it. Using all means
necessary. There should be regular audits that everyone is running the
software exactly in my configuration, and if not, a special task force will
take care that spankings are carried out on the spot.

Repeated offenders will lose their BitLicense.
</s>

Please stop kicking this dead horse. It was just a random idea. Maybe a way
how Linux distributions could structure it, but it may or may not apply in
your case. And that's fine, this is free software development, you can do
whatever you want!

Let's try to bring this discussion back to its original intention: for
anyone that wants to concretely help this along, please help reviewing and
testing the pull requests that jgarzik mentions.

Wladimir
BTW: All of those patches are helpful for monolithic-bitcoind as well as
they (lay the groundwork for) speeding up block synchronization.

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

[James Hartig]

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Setting aside all security benefits (which the user can obviously choose to
implement or ignore), a major benefit here is being able to have multiple
wallets use the same blockchain process. I have 3 different bitcoind
processes running on the same server to utilize multiple wallets. Using
them serially isn't an option in my case. Also, peers can run the cheaper
process instead of having the wallet functionality which isn't even used.

On the security front, this doesn't seem to be any less secure and it gives
the user the flexibility to make it as secure as they feel comfortable. If
they want to run them both as the same user with no SELinux or file
protections (this isn't stopping or encouraging that) they're already doing
that now with bitcoind, albeit with possibly a larger attack surface.

Thanks,
--
James Hartig
Software Engineer @ Grooveshark.com
http://twitter.com/jameshartig





On Sat, Feb 22, 2014 at 1:53 AM, Wladimir <laanwj@gmail.com> wrote:

>
> On Sat, Feb 22, 2014 at 2:09 AM, Dustin D. Trammell <
> dtrammell@dustintrammell.com> wrote:
>
>> On Fri, 2014-02-21 at 07:43 +0100, Wladimir wrote:
>> > The most straightforward way would be to run the blockchain daemon as
>> > a system service (with its own uid/gid and set of Apparmor/SELinux
>> > restrictions) and the wallet daemon as the user.
>>
>> This assumes you as a user have the rights to do so.  This would be
>> preferred, but in some cases may not be possible.  Perhaps it should be
>> optional?
>>
>
> No! I'm proposing that we force everyone to do it. Using all means
> necessary. There should be regular audits that everyone is running the
> software exactly in my configuration, and if not, a special task force will
> take care that spankings are carried out on the spot.
>
> Repeated offenders will lose their BitLicense.
> </s>
>
> Please stop kicking this dead horse. It was just a random idea. Maybe a
> way how Linux distributions could structure it, but it may or may not apply
> in your case. And that's fine, this is free software development, you can
> do whatever you want!
>
> Let's try to bring this discussion back to its original intention: for
> anyone that wants to concretely help this along, please help reviewing and
> testing the pull requests that jgarzik mentions.
>
> Wladimir
> BTW: All of those patches are helpful for monolithic-bitcoind as well as
> they (lay the groundwork for) speeding up block synchronization.
>
>
>
> ------------------------------------------------------------------------------
> Managing the Performance of Cloud-Based Applications
> Take advantage of what the Cloud has to offer - Avoid Common Pitfalls.
> Read the Whitepaper.
>
> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>
>

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

[Jeff Garzik]

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@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@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/
>>
>>
>> ------------------------------------------------------------------------------
>> Managing the Performance of Cloud-Based Applications
>> Take advantage of what the Cloud has to offer - Avoid Common Pitfalls.
>> Read the Whitepaper.
>>
>> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development



-- 
Jeff Garzik
Bitcoin core developer and open source evangelist
BitPay, Inc.      https://bitpay.com/

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

[Mike Hearn]

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I'm not sure it does really - typical C/C++ exploits let you run arbitrary
code, at which point you can quite easily ptrace the other process and do
whatever you want with it, or read /proc/pid/mem etc. But process
separation is certainly a prerequisite for sandboxing so I'm not arguing
against such a change, just pointing out that it requires some work to
really get the benefits. Also an SPV Bitcoin Core would obviously be of
tremendous utility all by itself ...


On Fri, Feb 21, 2014 at 12:20 PM, Jeff Garzik <jgarzik@bitpay.com> wrote:

> 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@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@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/
> >>
> >>
> >>
> ------------------------------------------------------------------------------
> >> Managing the Performance of Cloud-Based Applications
> >> Take advantage of what the Cloud has to offer - Avoid Common Pitfalls.
> >> Read the Whitepaper.
> >>
> >>
> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk
> >> _______________________________________________
> >> Bitcoin-development mailing list
> >> Bitcoin-development@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>
>
>
> --
> Jeff Garzik
> Bitcoin core developer and open source evangelist
> BitPay, Inc.      https://bitpay.com/
>

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

[Peter Todd]

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On Fri, Feb 21, 2014 at 04:11:06PM +0530, Mike Hearn wrote:
> On Fri, Feb 21, 2014 at 12:20 PM, Jeff Garzik <jgarzik@bitpay.com> wrote:
> 
> > 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.
>
> I'm not sure it does really - typical C/C++ exploits let you run arbitrary
> code, at which point you can quite easily ptrace the other process and do
> whatever you want with it, or read /proc/pid/mem etc. But process
> separation is certainly a prerequisite for sandboxing so I'm not arguing
> against such a change, just pointing out that it requires some work to
> really get the benefits. Also an SPV Bitcoin Core would obviously be of
> tremendous utility all by itself ...

The seccomp mechanism would work well here - it's a syscall whitelister,
which makes ptrace useless, among other things. Used by Chrome as of v23
to sandbox the renderers.

We'd probably need to use it with chroot and whitelist the open() call
so that the existing code can create new blockfiles and do whatever
leveldb does.

-- 
'peter'[:-1]@petertodd.org
000000000000000112c53364597954e79cc38f1ba7826a6420ad22a6f3be2932

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

[Dustin D. Trammell]

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On Fri, 2014-02-21 at 01:09 -0500, Jeff Garzik wrote:
> 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.

PLEASE.

For those of us that prefer the reference software and also manage
multiple wallets, having to store a copy of the blockchain for each one
eats up disk space quite quickly.  If I could run a local blockchain
server (or a local network one, even) and then have whichever wallet I
start up use that instead of maintain its own copy of the blockchain, my
world would be much, much happier.

Sandboxing keys and sensitive wallet data away from the attack surface
introduced by the network interfaces into another separate process is
also a good security move.  Don't forget to sanitize your IPC inputs (:

Thanks,

-- 
Dustin D. Trammell
dtrammell@dustintrammell.com
http://www.dustintrammell.com

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

[Jeff Garzik]

On Fri, Feb 21, 2014 at 8:04 PM, Dustin D. Trammell
<dtrammell@dustintrammell.com> wrote:
> For those of us that prefer the reference software and also manage
> multiple wallets, having to store a copy of the blockchain for each one
> eats up disk space quite quickly.  If I could run a local blockchain
> server (or a local network one, even) and then have whichever wallet I
> start up use that instead of maintain its own copy of the blockchain, my
> world would be much, much happier.

You mean running multiple wallets simultaneously?  Agreed.

Multiple wallets, used serially, works fine today.  I manage multiple
wallets using symlink replacement.

-- 
Jeff Garzik
Bitcoin core developer and open source evangelist
BitPay, Inc.      https://bitpay.com/