Implements most of #297 to the point I'm fine closing it. The solution
implemented is distinct than originally designed, yet much simpler.
Since we have a fully-linear view of created transactions, we don't have to
per-output track operating costs incurred by that output. We can track it
across the entire Serai system, without hooking into the Eventuality system.
Also updates documentation.
Replaces plan IDs with key + ID, letting the coordinator determine the sessions
for the plans.
Properly scopes which plan IDs are set on which tributaries, and ensures we
have the necessary tributaries at time of handling.
* Revert "Correct the prior documented TOCTOU"
This reverts commit d50fe87801.
* Correct the prior documented TOCTOU
d50fe87801 edited the challenge for the Batch to
fix it. This won't produce Batch n+1 until Batch n is successfully published
and verified. It's an alternative strategy able to be reviewed, with a much
smaller impact to scope.
Now, if a malicious validator set publishes a malicious `Batch` at the last
moment, it'll cause all future `Batch`s signed by the next validator set to
require a bool being set (yet they never will set it).
This will prevent the handover.
The only overhead is having two distinct `batch_message` calls on-chain.
Renames Update to SignedBatch.
Checks Batch equality via a hash of the InInstructions. That prevents needing
to keep the Batch in node state or TX introspect.
Prior, we only supported a single Tributary per network, and spawned a task to
handled Processor messages per Tributary. Now, we handle Processor messages per
network, yet we still only supported a single Tributary in that handling
function.
Now, when we handle a message, we load the Tributary which is relevant. Once we
know it, we ensure we have it (preventing race conditions), and then proceed.
We do need work to check if we should have a Tributary, or if we're not
participating. We also need to check if a Tributary has been retired, meaning
we shouldn't handle any transactions related to them, and to clean up retired
Tributaries.
* Design and document a multisig rotation flow
* Make Scanner::eventualities a HashMap so it's per-key
* Don't drop eventualities, always follow through on them
Technical improvements made along the way.
* Start creating an isolate object to manage multisigs, which doesn't require being a signer
Removes key from SubstrateBlock.
* Move Scanner/Scheduler under multisigs
* Move Batch construction into MultisigManager
* Clarify "should" in Multisig Rotation docs
* Add block_number to MultisigManager, as it controls the scanner
* Move sign_plans into MultisigManager
Removes ThresholdKeys from prepare_send.
* Make SubstrateMutable an alias for MultisigManager
* Rewrite Multisig Rotation
The prior scheme had an exploit possible where funds were sent to the old
multisig, then burnt on Serai to send from the new multisig, locking liquidity
for 6 hours. While a fee could be applied to stragglers, to make this attack
unprofitable, the newly described scheme avoids all this.
* Add mini
mini is a miniature version of Serai, emphasizing Serai's nature as a
collection of independent clocks. The intended use is to identify race
conditions and prove protocols are comprehensive regarding when certain clocks
tick.
This uses loom, a prior candidate for evaluating the processor/coordinator as
free of race conditions (#361).
* Use mini to prove a race condition in the current multisig rotation docs, and prove safety of alternatives
Technically, the prior commit had mini prove the race condition.
The docs currently say the activation block of the new multisig is the block
after the next Batch's. If the two next Batches had already entered the
mempool, prior to set_keys being called, the second next Batch would be
expected to contain the new key's data yet fail to as the key wasn't public
when the Batch was actually created.
The naive solution is to create a Batch, publish it, wait until it's included,
and only then scan the next block. This sets a bound of
`Batch publication time < block time`. Optimistically, we can publish a Batch
in 24s while our shortest block time is 2m. Accordingly, we should be fine with
the naive solution which doesn't take advantage of throughput. #333 may
significantly change latency however and require an algorithm whose throughput
exceeds the rate of blocks created.
In order to re-introduce parallelization, enabling throughput, we need to
define a safe range of blocks to scan without Serai ordering the first one.
mini demonstrates safety of scanning n blocks Serai hasn't acknowledged, so
long as the first is scanned before block n+1 is (shifting the n-block window).
The docs will be updated next, to reflect this.
* Fix Multisig Rotation
I believe this is finally good enough to be final.
1) Fixes the race condition present in the prior document, as demonstrated by
mini.
`Batch`s for block `n` and `n+1`, may have been in the mempool when a
multisig's activation block was set to `n`. This would cause a potentially
distinct `Batch` for `n+1`, despite `n+1` already having a signed `Batch`.
2) Tightens when UIs should use the new multisig to prevent eclipse attacks,
and protection against `Batch` publication delays.
3) Removes liquidity fragmentation by tightening flow/handling of latency.
4) Several clarifications and documentation of reasoning.
5) Correction of "prior multisig" to "all prior multisigs" regarding historical
verification, with explanation why.
* Clarify terminology in mini
Synchronizes it from my original thoughts on potential schema to the design
actually created.
* Remove most of processor's README for a reference to docs/processor
This does drop some misc commentary, though none too beneficial. The section on
scanning, deemed sufficiently beneficial, has been moved to a document and
expanded on.
* Update scanner TODOs in line with new docs
* Correct documentation on Bitcoin::Block::time, and Block::time
* Make the scanner in MultisigManager no longer public
* Always send ConfirmKeyPair, regardless of if in-set
* Cargo.lock changes from a prior commit
* Add a policy document on defining a Canonical Chain
I accidentally committed a version of this with a few headers earlier, and this
is a proper version.
* Competent MultisigManager::new
* Update processor's comments
* Add mini to copied files
* Re-organize Scanner per multisig rotation document
* Add RUST_LOG trace targets to e2e tests
* Have the scanner wait once it gets too far ahead
Also bug fixes.
* Add activation blocks to the scanner
* Split received outputs into existing/new in MultisigManager
* Select the proper scheduler
* Schedule multisig activation as detailed in documentation
* Have the Coordinator assert if multiple `Batch`s occur within a block
While the processor used to have ack_up_to_block, enabling skips in the block
acked, support for this was removed while reworking it for multiple multisigs.
It should happen extremely infrequently.
While it would still be beneficial to have, if multiple `Batch`s could occur
within a block (with the complexity here not being worth adding that ban as a
policy), multiple `Batch`s were blocked for DoS reasons.
* Schedule payments to the proper multisig
* Correct >= to <
* Use the new multisig's key for change on schedule
* Don't report External TXs to prior multisig once deprecated
* Forward from the old multisig to the new one at all opportunities
* Move unfulfilled payments in queue from prior to new multisig
* Create MultisigsDb, splitting it out of MainDb
Drops the call to finish_signing from the Signer. While this will cause endless
re-attempts, the Signer will still consider them completed and drop them,
making this an O(n) cost at boot even if we did nothing from here.
The MultisigManager should call finish_signing once the Scanner completes the
Eventuality.
* Don't check Scanner-emitted completions, trust they are completions
Prevents needing to use async code to mark the completion and creates a
fault-free model. The current model, on fault, would cause a lack of marked
completion in the signer.
* Fix a possible panic in the processor
A shorter-chain reorg could cause this assert to trip. It's fixed by
de-duplicating the data, as the assertion checked consistency. Without the
potential for inconsistency, it's unnecessary.
* Document why an existing TODO isn't valid
* Change when we drop payments for being to the change address
The earlier timing prevents creating Plans solely to the branch address,
causing the payments to be dropped, and the TX to become an effective
aggregation TX.
* Extensively document solutions to Eventualities being potentially created after having already scanned their resolutions
* When closing, drop External/Branch outputs which don't cause progress
* Properly decide if Change outputs should be forward or not when closing
This completes all code needed to make the old multisig have a finite lifetime.
* Commentary on forwarding schemes
* Provide a 1 block window, with liquidity fragmentation risks, due to latency
On Bitcoin, this will be 10 minutes for the relevant Batch to be confirmed. On
Monero, 2 minutes. On Ethereum, ~6 minutes.
Also updates the Multisig Rotation document with the new forwarding plan.
* Implement transaction forwarding from old multisig to new multisig
Identifies a fault where Branch outputs which shouldn't be dropped may be, if
another output fulfills their next step. Locking Branch fulfillment down to
only Branch outputs is not done in this commit, but will be in the next.
* Only let Branch outputs fulfill branches
* Update TODOs
* Move the location of handling signer events to avoid a race condition
* Avoid a deadlock by using a RwLock on a single txn instead of two txns
* Move Batch ID out of the Scanner
* Increase from one block of latency on new keys activation to two
For Monero, this offered just two minutes when our latency to publish a Batch
is around a minute already. This does increase the time our liquidity can be
fragmented by up to 20 minutes (Bitcoin), yet it's a stupid attack only
possible once a week (when we rotate). Prioritizing normal users' transactions
not being subject to forwarding is more important here.
Ideally, we'd not do +2 blocks yet plus `time`, such as +10 minutes, making
this agnostic of the underlying network's block scheduling. This is a
complexity not worth it.
* Split MultisigManager::substrate_block into multiple functions
* Further tweaks to substrate_block
* Acquire a lock on all Scanner operations after calling ack_block
Gives time to call register_eventuality and initiate signing.
* Merge sign_plans into substrate_block
Also ensure the Scanner's lock isn't prematurely released.
* Use a HashMap to pass to-be-forwarded instructions, not the DB
* Successfully determine in ClosingExisting
* Move from 2 blocks of latency when rotating to 10 minutes
Superior as noted in 6d07af92ce10cfd74c17eb3400368b0150eb36d7, now trivial to
implement thanks to prior commit.
* Add note justifying measuring time in blocks when rotating
* Implement delaying of outputs received early to the new multisig per specification
* Documentation on why Branch outputs don't have the race condition concerns Change do
Also ensures 6 hours is at least N::CONFIRMATIONS, for sanity purposes.
* Remove TODO re: sanity checking Eventualities
We sanity check the Plan the Eventuality is derived from, and the Eventuality
is handled moments later (in the same file, with a clear call path). There's no
reason to add such APIs to Eventualities for a sanity check given that.
* Add TODO(now) for TODOs which must be done in this branch
Also deprecates a pair of TODOs to TODO2, and accepts the flow of the Signer
having the Eventuality.
* Correct errors in potential/future flow descriptions
* Accept having a single Plan Vec
Per the following code consuming it, there's no benefit to bifurcating it by
key.
* Only issue sign_transaction on boot for the proper signer
* Only set keys when participating in their construction
* Misc progress
Only send SubstrateBlockAck when we have a signer, as it's only used to tell
the Tributary of what Plans are being signed in response to this block.
Only immediately sets substrate_signer if session is 0.
On boot, doesn't panic if we don't have an active key (as we wouldn't if only
joining the next multisig). Continues.
* Correctly detect and set retirement block
Modifies the retirement block from first block meeting requirements to block
CONFIRMATIONS after.
Adds an ack flow to the Scanner's Confirmed event and Block event to accomplish
this, which may deadlock at this time (will be fixed shortly).
Removes an invalid await (after a point declared unsafe to use await) from
MultisigsManager::next_event.
* Remove deadlock in multisig_completed and document alternative
The alternative is simpler, albeit less efficient. There's no reason to adopt
it now, yet perhaps if it benefits modeling?
* Handle the final step of retirement, dropping the old key and setting new to existing
* Remove TODO about emitting a Block on every step
If we emit on NewAsChange, we lose the purpose of the NewAsChange period.
The only concern is if we reach ClosingExisting, and nothing has happened, then
all coins will still be in the old multisig until something finally does. This
isn't a problem worth solving, as it's latency under exceptional dead time.
* Add TODO about potentially not emitting a Block event for the reitrement block
* Restore accidentally deleted CI file
* Pair of slight tweaks
* Add missing if statement
* Disable an assertion when testing
One of the test flows currently abuses the Scanner in a way triggering it.
Eventualities need to be binding not just to a plan, yet to the execution of
the plan (the outputs). Bitcoin's Eventuality definition short-cutted this
under a honest multisig assumption, causing the following issue:
If multisig n+1 is verifying multisig n's actions, as detailed in
multi-multisig's document on multisig rotation, it'll check no outstanding
eventualities exist. If we solely bind to the plan, a malicious multisig n
could steal outbound payments yet cause the plan to be marked as successfully
completed.
By modifying the eventuality to also include the expected outputs, this is no
longer possible. Binding to the expected input is preserved in order to remain
binding to the plan (allowing two plans with the same output-set to co-exist).
Fixes where ram_scanned is updated in processor. The prior version, while safe,
would redo massive amounts of work during periods of inactivity. It also hit an
undocumented invariant where get_eventuality_completions assumes new blocks,
yet redone work wouldn't have new blocks.
Modifies Monero's generate_blocks to return the hashes of the generated blocks.
A commit made while testing moved them from network-key-indexed to
Substrate-key-indexed. Since Substrate keys have a fixed-length, fitting within
the Copy boundary, there's no reason for it to not use an array.
* restrict batch size to ~25kb
* add batch size check to node
* rate limit batches to 1 per serai block
* add support for multiple batches for block
* fix review comments
* Misc fixes
Doesn't yet update tests/processor until data flow is inspected.
* Move the block from SignId to ProcessorMessage::BatchPreprocesses
* Misc clean up
---------
Co-authored-by: Luke Parker <lukeparker5132@gmail.com>
By default, tokio-spawned worker panics will only kill the task, not the
program. Due to our extensive use of panicking on invariants, we should ensure
the program exits.
The Processor's coins folder referred to the networks it could process, as did
its Coin trait. This, and other similar cases throughout the codebase, have now
been corrected.
Also corrects dated documentation for a key pair is confirmed under the
validator-sets pallet.
This is a horrible impl which does a full ser of everything on every change.
It's just the minimal changes to resolve this TODO and able testnet deployment.
Due to the ordered message-queue, there's no benefit to multiple emissions as
there's no risk a completion will be missed. If it has yet to be read, sending
another which only be read after isn't helpful.
Simplifies code a decent bit.
This is technically over-agressive, as a dropped output will reduce the fee,
yet this edge case is so minor the flow for it to not be over-aggressive (over
a few fractions of a cent) is by no means worth it.
Fixes the crash causable by the WIP send_test.
It waited for CONFIRMATIONS + 1 confirmations, instead of CONFIRMATIONS
confirmations.
Also adds a lib interface to access the coin traits and its constants.
All uses were safe due to addresses being converted to script_pubkeys which
don't embed their network. The only risk of there being an issue is if a
future address spec did embed the net ID into the script_pubkey and that was
moved to.
This resolves the audit note and does offer that tightening.
* add mlsag
* fix last commit
* fix miner v1 txs
* fix non-miner v1 txs
* add borromean + fix mlsag
* add block hash calculations
* fix for the jokester that added unreduced scalars
to the borromean signature of
2368d846e671bf79a1f84c6d3af9f0bfe296f043f50cf17ae5e485384a53707b
* Add Borromean range proof verifying functionality
* Add MLSAG verifying functionality
* fmt & clippy :)
* update MLSAG, ss2_elements will always be 2
* Add MgSig proving
* Tidy block.rs
* Tidy Borromean, fix bugs in last commit, replace todo! with unreachable!
* Mark legacy EcdhInfo amount decryption as experimental
* Correct comments
* Write a new impl of the merkle algorithm
This one tries to be understandable.
* Only pull in things only needed for experimental when experimental
* Stop caching the Monero block hash now in processor that we have Block::hash
* Corrections for recent processor commit
* Use a clearer algorithm for the merkle
Should also be more efficient due to not shifting as often.
* Tidy Mlsag
* Remove verify_rct_* from Mlsag
Both methods were ports from Monero, overtly specific without clear
documentation. They need to be added back in, with documentation, or included
in a node which provides the necessary further context for them to be naturally
understandable.
* Move mlsag/mod.rs to mlsag.rs
This should only be a folder if it has multiple files.
* Replace EcdhInfo terminology
The ECDH encrypted the amount, yet this struct contained the encrypted amount,
not some ECDH.
Also corrects the types on the original EcdhInfo struct.
* Correct handling of commitment masks when scanning
* Route read_array through read_raw_vec
* Misc lint
* Make a proper RctType enum
No longer caches RctType in the RctSignatures as well.
* Replace Vec<Bulletproofs> with Bulletproofs
Monero uses aggregated range proofs, so there's only ever one Bulletproof. This
is enforced with a consensus rule as well, making this safe.
As for why Monero uses a vec, it's probably due to the lack of variadic typing
used. Its effectively an Option for them, yet we don't need an Option since we
do have variadic typing (enums).
* Add necessary checks to Eventuality re: supported protocols
* Fix for block 202612 and fix merkel root calculations
* MLSAG (de)serialisation fix
ss_2_elements will not always be 2 as rct type 1 transactions are not enforced to have one input
* Revert "MLSAG (de)serialisation fix"
This reverts commit 5e710e0c96.
here it checks number of MGs == number of inputs:
0a1eaf26f9/src/cryptonote_core/tx_verification_utils.cpp (L60-59)
and here it checks for RctTypeFull number of MGs == 1:
0a1eaf26f9/src/ringct/rctSigs.cpp (L1325)
so number of inputs == 1
so ss_2_elements == 2
* update `MlsagAggregate` comment
* cargo update
Resolves a yanked crate
* Move location of serai-client in Cargo.toml
---------
Co-authored-by: Luke Parker <lukeparker5132@gmail.com>
Provides a DST, and associated metadata as beneficial.
Also utilizes MuSig's context to session-bind. Since set_keys_messages also
binds to set, this is semi-redundant, yet that's appreciated.
When we receive messages, we're provided with a message ID we can use to
prevent handling an item multiple times. That doesn't prevent us from *sending*
an item multiple times though. Thanks to the UID system, we can now not send if
already present.
Alternatively, we can remove the ordered message ID for just the UID, allowing
duplicates to be sent without issue, and handled on the receiving end.
When a Substrate block occurs, the coordinator is expected to emit
SubstrateBlock. This causes the processor to begin a variety of plans. The
processor now emits SubstrateBlockAck, explicitly listing all plan IDs, before
starting signing.
This lets the coordinator provide a SubstrateBlock transaction, and with it,
recognize all plan IDs as valid.
Prior, we would've had to have a spotty algorithm based upon the upcoming
Preprocess messages, or if we immediately provided the SubstrateBlock
transaction, then wait for the processor to inform us of the contained plans.
This creates an explicitly proper async flow not reliant on waiting for data
availability.
Alternatively, we could've replaced Preprocess with (Block, Vec<Preprocess>).
This would've been more efficient, yet also clunky due to the multiple usages
of the Preprocess message.
There is the ability to cause state bloat by flooding Tributary.
KeyGen/Sign specifically shouldn't allow bloat since we check the
commitments/preprocesses/shares for validity. Accordingly, any invalid data
(such as bloat) should be detected.
It was posssible to place bloat after the valid data. Doing so would be
considered a valid KeyGen/Sign message, yet could add up to 50k kB per sign.
[0; 32] is a magic for no block has been set yet due to this being the first
key pair. If [0; 32] is the latest finalized block, the processor determines
an activation block based on timestamps.
This doesn't use an Option for ergonomic reasons.
It originally wasn't an enum so software which had yet to update before an
integration wouldn't error (as now enums are strictly typed). The strict typing
is preferable though.
SubstrateBlock's provision of the most recently acknowledged block has
equivalent information with the same latency. Accordingly, there's no need for
it.
Clearly establishes why consistency is guaranteed from a Rust borrow-checker
mindset. While there are plenty of... 'violations', they're clearly explained.
Hopefully, this method of thinking helps promote/ensure consistency in the
future.
The signing set should be the first group to submit preprocesses to Tributary.
Re-attempts shouldn't be once every 30s, yet n blocks since the last relevant
message.
Removes the use of an async task/channel in the signer (and Substrate signer).
Also removes the need to be able to get the time from a coin's block, which was
a fragile system marked with a TODO already.
