Make rand a dev-dependency by TheBlueMatt · Pull Request #353 · lightningdevkit/rust-lightning

TheBlueMatt · 2019-07-19T03:57:20Z

This moves the two places we called rand in regular operation into parameters, making rand a dev-dependency and (hopefully) fully supporting WASM. There's still a few things to do tomorrow, but this is 95% there.

TheBlueMatt · 2019-07-19T03:57:53Z

Alternative to #352.

elichai · 2019-07-19T18:23:18Z

Looks cool :)
if you want you use use this opportunity to replace the rand crate with a smaller one because you only use the fill_bytes anyway so there's no need to import and compile all of the different random sources you can just import rand_os for example (which is 10th the size of rand)

TheBlueMatt · 2019-07-19T19:11:57Z

I think for portability (eg hardware wallets or possible mobile devices or other embedding) reasons we probably don't want to use rand at all.

elichai · 2019-07-19T19:24:29Z

I meant in the dev dependencies

TheBlueMatt · 2019-07-19T20:41:11Z

Should be ready for review now.

elichai

Other than the things I commented ACK 2a1813b

fuzz/fuzz_targets/peer_crypt_target.rs

elichai · 2019-07-19T21:02:09Z

fuzz/fuzz_targets/peer_crypt_target.rs

+	};

 	let mut crypter = if get_slice!(1)[0] != 0 {
 		let their_pubkey = match PublicKey::from_slice(get_slice!(33)) {


This will fail a lot.
Every time the first byte won't be 0x02 or 0x03 it will fail.

Maybe add a function that generates a Secret Key and creates a Public Key from it.
or hard code 0x02 and randomize the other 32 bytes. (the first one will at least guarantee success)

Yea, this test isnt really great, but its also testing very small surface area, so Im not gonna worry too much about it.

Edit: As you told me before, get_slice!() doesn't use randomness.
So maybe using 0x02/0x03 as the first byte and the rest from the provided data should cover most errors.

elichai · 2019-07-19T21:07:02Z

src/ln/functional_tests.rs

@@ -1309,7 +1308,8 @@ fn do_channel_reserve_test(test_recv: bool) {
 		let secp_ctx = Secp256k1::new();
 		let session_priv = SecretKey::from_slice(&{


Same.
You can use SecretKey::new(&mut Rng)

src/ln/peer_handler.rs

ariard

I'm just a bit skeptical about starting_time in the KeysManager interface. That's said that just our own KeysManager and I'm pretty sure users will come with their own KeysInterface, but we should be at least more clear on seed storage requirements.

Just slightly review the changes on the fuzzing tests.

ariard · 2019-07-23T01:57:22Z

src/chain/keysinterface.rs

+	/// starting_time isn't strictly required to actually be a time, but it must absolutely,
+	/// without a doubt, be unique to this instance. ie if you start multiple times with the same
+	/// seed, starting_time must be unique to each run. Thus, the easiest way to achieve this is to
+	/// simply use the current time (with very high precision).


Hmmm isn't this change making starting time part of user channel keys ? And now he would have to backup the provided current time, maybe with nanos precision, that's not great.. Furthermore I understand why you want a unique seed + nonce for every lightning instance but not for multiple run of the same instance. You want to be able to derive channel_keys again

Reading this whole interface again, IMO we should do better to explain to the user what he need to reliably backup his funds.

Cleaned up the comment. Is it better now?

Well I would add a last sentence like "You MUST backup the seed. Your seed is needed to recover outpoints closing the channel (destination_key, shutdown_pubkey). The seed alone can't recover in-channel funds, so you MUST backup individual channel too. Starting time reason is to get new ephemeral key data but can't help you to know channel state."

Should we also ask user to backup software version in case we update our derivation scheme?

Ehh, dont really want to commit to a versioning scheme just yet, updated the docs to indicate that we will have something in the future, but for now, expect funds loss when upgrading.

Okay, seems good for me, that's clear enough for users they are on their own here!

src/chain/keysinterface.rs

ariard · 2019-07-23T02:29:12Z

fuzz/fuzz_targets/full_stack_target.rs

 		//
 		// 0c007d - connect a block with one transaction of len 125
-		// 02000000013f00000000000000000000000000000000000000000000000000000000000000000000000000000080020001000000000000220020e2000000000000000000000000000000000000000000000000000000000000006cc10000000000001600142e0000000000000000000000000000000000000005000020 - the commitment transaction for channel 3f00000000000000000000000000000000000000000000000000000000000000
+		// 02000000013f0000000000000000000000000000000000000000000000000000000000000000000000000000008002000100000000000022002090000000000000000000000000000000000000000000000000000000000000006cc10000000000001600145c0000000000000000000000000000000000000005000020 - the commitment transaction for channel 3f00000000000000000000000000000000000000000000000000000000000000


Quick git blame would point towards me with a2b6a76, IIRC with this one, I've added few connect blocks more to hit delay of passing failures backaward. This test has passed the travis, does it the mix of our changes which breaks it ?

Probably? It doesn't really matter all that much.

ariard · 2019-07-23T02:40:54Z

src/ln/peer_channel_encryptor.rs

-		let mut key = [0u8; 32];
-		rng::fill_bytes(&mut key);
-
+	pub fn new_outbound(their_node_id: PublicKey, ephemeral_key: SecretKey) -> PeerChannelEncryptor {


This is part of our public interface, shouldn't this get its own comment, specially on what we require in term of entropy for the new parameter ephemeral_key ?

Oh I saw the comment in peer_handler, but maybe you could invite to read the one there!

peer_channel_encryptor is only exposed privately? Otherwise it would be a build failure due to lack of docs.

ariard · 2019-07-23T02:59:06Z

src/ln/peer_handler.rs

+		let high = if low == 0 {
+			self.peer_counter_high.fetch_add(1, Ordering::AcqRel)
+		} else {
+			self.peer_counter_high.load(Ordering::Acquire)


Oh that's interesting, it means on 32-bit platform, we have a 2^1024 monotonic counter right to use as sha-256 input for ephemeral key generation ?

Where'd you get 2^1024? 2 32-bit counters is a 64-bit counter.

You're right, I've screwed up my calculation

ariard · 2019-07-23T03:07:53Z

src/util/events.rs

 	PendingHTLCsForwardable {
-		/// The amount of time that should be waited prior to calling process_pending_htlc_forwards
+		/// The minimum amount of time that should be waited prior to calling
+		/// process_pending_htlc_forwards. To increase the effort required to correlate payments,


But if you're already on the payment path, you can already do decorrelation attacks with hashes ? You're trying to break what kind of analysis here ?

Hmm...I guess I haven't formalized it, but there's almost certainly some stuff you can learn if the timing is super, super consistent. eg you could learn the number of hops that something took just by looking at the timing. Hiding that at least somewhat or for individual payments.

I would argue if you're two spots on the same payment path, you can guess the number of hops by recomputing the per-hop fees between your A and your B given fees are public. Out-of-topic, as you said if user is willingly to wait shouldn't hurt.

Right, but a user could have a more privacy-conscious routing algorithm, and we don't want to reveal info unless we have to. I think its generally a good idea, but agreed more study and a formal threat model would be better.

They were only used for ensuring generated keys were globally unique (ie in case the user opened the same seed at a different time, we need generated keys to be globally unique). Instead, we let the user specify a time in secs/nanos, and provide a precise meaning for the user to understand.

This removes the bulk of our reliance on the rand crate in non-test envs, paving a way towards a syscall-less rust-lightning and WASM. Since this is a breaking change for full_stack_target (and several fuzz targets), go ahead and make other changes to make things more distinct.

This removes the last calls to rand outside of test and moves the dep to a dev-dependency, dropping our fuzz rng wrapper in the process.

TheBlueMatt added this to the 0.0.11 milestone Jul 19, 2019

TheBlueMatt changed the title ~~(WIP) Make rand a dev-dependency~~ Make rand a dev-dependency Jul 19, 2019

TheBlueMatt force-pushed the 2019-07-no-rand branch from 6625de1 to 2a1813b Compare July 19, 2019 20:41

elichai reviewed Jul 19, 2019

View reviewed changes

TheBlueMatt force-pushed the 2019-07-no-rand branch 3 times, most recently from 56b2398 to 630a3ba Compare July 22, 2019 21:38

ariard reviewed Jul 23, 2019

View reviewed changes

TheBlueMatt force-pushed the 2019-07-no-rand branch from 630a3ba to 8f487eb Compare July 23, 2019 16:25

TheBlueMatt added 6 commits July 23, 2019 14:29

Remove dangling link in fuzz/

d9043b5

Move travis fuzzing to 1.34.2 to get integer atomics

c50aa05

Update commitment tx to match actual tx (dunno when it broke)

1650992

Make rand a dev-dep by having the user randomize HTLC forward delay

bf7eeb1

This removes the last calls to rand outside of test and moves the dep to a dev-dependency, dropping our fuzz rng wrapper in the process.

TheBlueMatt force-pushed the 2019-07-no-rand branch from 8f487eb to bf7eeb1 Compare July 23, 2019 18:30

TheBlueMatt merged commit cd8f1de into lightningdevkit:master Jul 23, 2019

TheBlueMatt mentioned this pull request Jul 23, 2019

Replace randomness source #352

Closed

jkczyz mentioned this pull request Jan 31, 2020

Rust release support #471

Closed

		@@ -1309,7 +1308,8 @@ fn do_channel_reserve_test(test_recv: bool) {
		let secp_ctx = Secp256k1::new();
		let session_priv = SecretKey::from_slice(&{

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TheBlueMatt commented Jul 19, 2019

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