serai/processor/README.md

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Processor (#259) * Initial work on a message box * Finish message-box (untested) * Expand documentation * Embed the recipient in the signature challenge Prevents a message from A -> B from being read as from A -> C. * Update documentation by bifurcating sender/receiver * Panic on receiving an invalid signature If we've received an invalid signature in an authenticated system, a service is malicious, critically faulty (equivalent to malicious), or the message layer has been compromised (or is otherwise critically faulty). Please note a receiver who handles a message they shouldn't will trigger this. That falls under being critically faulty. * Documentation and helper methods SecureMessage::new and SecureMessage::serialize. Secure Debug for MessageBox. * Have SecureMessage not be serialized by default Allows passing around in-memory, if desired, and moves the error from decrypt to new (which performs deserialization). Decrypt no longer has an error since it panics if given an invalid signature, due to this being intranet code. * Explain and improve nonce handling Includes a missing zeroize call. * Rebase to latest develop Updates to transcript 0.2.0. * Add a test for the MessageBox * Export PrivateKey and PublicKey * Also test serialization * Add a key_gen binary to message_box * Have SecureMessage support Serde * Add encrypt_to_bytes and decrypt_from_bytes * Support String ser via base64 * Rename encrypt/decrypt to encrypt_bytes/decrypt_to_bytes * Directly operate with values supporting Borsh * Use bincode instead of Borsh By staying inside of serde, we'll support many more structs. While bincode isn't canonical, we don't need canonicity on an authenticated, internal system. * Turn PrivateKey, PublicKey into structs Uses Zeroizing for the PrivateKey per #150. * from_string functions intended for loading from an env * Use &str for PublicKey from_string (now from_str) The PrivateKey takes the String to take ownership of its memory and zeroize it. That isn't needed with PublicKeys. * Finish updating from develop * Resolve warning * Use ZeroizingAlloc on the key_gen binary * Move message-box from crypto/ to common/ * Move key serialization functions to ser * add/remove functions in MessageBox * Implement Hash on dalek_ff_group Points * Make MessageBox generic to its key Exposes a &'static str variant for internal use and a RistrettoPoint variant for external use. * Add Private to_string as deprecated Stub before more competent tooling is deployed. * Private to_public * Test both Internal and External MessageBox, only use PublicKey in the pub API * Remove panics on invalid signatures Leftover from when this was solely internal which is now unsafe. * Chicken scratch a Scanner task * Add a write function to the DKG library Enables writing directly to a file. Also modifies serialize to return Zeroizing<Vec<u8>> instead of just Vec<u8>. * Make dkg::encryption pub * Remove encryption from MessageBox * Use a 64-bit block number in Substrate We use a 64-bit block number in general since u32 only works for 120 years (with a 1 second block time). As some chains even push the 1 second threshold, especially ones based on DAG consensus, this becomes potentially as low as 60 years. While that should still be plenty, it's not worth wondering/debating. Since Serai uses 64-bit block numbers elsewhere, this ensures consistency. * Misc crypto lints * Get the scanner scratch to compile * Initial scanner test * First few lines of scheduler * Further work on scheduler, solidify API * Define Scheduler TX format * Branch creation algorithm * Document when the branch algorithm isn't perfect * Only scanned confirmed blocks * Document Coin * Remove Canonical/ChainNumber from processor The processor should be abstracted from canonical numbers thanks to the coordinator, making this unnecessary. * Add README documenting processor flow * Use Zeroize on substrate primitives * Define messages from/to the processor * Correct over-specified versioning * Correct build re: in_instructions::primitives * Debug/some serde in crypto/ * Use a struct for ValidatorSetInstance * Add a processor key_gen task Redos DB handling code. * Replace trait + impl with wrapper struct * Add a key confirmation flow to the key gen task * Document concerns on key_gen * Start on a signer task * Add Send to FROST traits * Move processor lib.rs to main.rs Adds a dummy main to reduce clippy dead_code warnings. * Further flesh out main.rs * Move the DB trait to AsRef<[u8]> * Signer task * Remove a panic in bitcoin when there's insufficient funds Unchecked underflow. * Have Monero's mine_block mine one block, not 10 It was initially a nicety to deal with the 10 block lock. C::CONFIRMATIONS should be used for that instead. * Test signer * Replace channel expects with log statements The expects weren't problematic and had nicer code. They just clutter test output. * Remove the old wallet file It predates the coordinator design and shouldn't be used. * Rename tests/scan.rs to tests/scanner.rs * Add a wallet test Complements the recently removed wallet file by adding a test for the scanner, scheduler, and signer together. * Work on a run function Triggers a clippy ICE. * Resolve clippy ICE The issue was the non-fully specified lambda in signer. * Add KeyGenEvent and KeyGenOrder Needed so we get KeyConfirmed messages from the key gen task. While we could've read the CoordinatorMessage to see that, routing through the key gen tasks ensures we only handle it once it's been successfully saved to disk. * Expand scanner test * Clarify processor documentation * Have the Scanner load keys on boot/save outputs to disk * Use Vec<u8> for Block ID Much more flexible. * Panic if we see the same output multiple times * Have the Scanner DB mark itself as corrupt when doing a multi-put This REALLY should be a TX. Since we don't have a TX API right now, this at least offers detection. * Have DST'd DB keys accept AsRef<[u8]> * Restore polling all signers Writes a custom future to do so. Also loads signers on boot using what the scanner claims are active keys. * Schedule OutInstructions Adds a data field to Payment. Also cleans some dead code. * Panic if we create an invalid transaction Saves the TX once it's successfully signed so if we do panic, we have a copy. * Route coordinator messages to their respective signer Requires adding key to the SignId. * Send SignTransaction orders for all plans * Add a timer to retry sign_plans when prepare_send fails * Minor fmt'ing * Basic Fee API * Move the change key into Plan * Properly route activation_number * Remove ScannerEvent::Block It's not used under current designs * Nicen logs * Add utilities to get a block's number * Have main issue AckBlock Also has a few misc lints. * Parse instructions out of outputs * Tweak TODOs and remove an unwrap * Update Bitcoin max input/output quantity * Only read one piece of data from Monero Due to output randomization, it's infeasible. * Embed plan IDs into the TXs they create We need to stop attempting signing if we've already signed a protocol. Ideally, any one of the participating signers should be able to provide a proof the TX was successfully signed. We can't just run a second signing protocol though as a single malicious signer could complete the TX signature, and publish it, yet not complete the secondary signature. The TX itself has to be sufficient to show that the TX matches the plan. This is done by embedding the ID, so matching addresses/amounts plans are distinguished, and by allowing verification a TX actually matches a set of addresses/amounts. For Monero, this will need augmenting with the ephemeral keys (or usage of a static seed for them). * Don't use OP_RETURN to encode the plan ID on Bitcoin We can use the inputs to distinguih identical-output plans without issue. * Update OP_RETURN data access It's not required to be the last output. * Add Eventualities to Monero An Eventuality is an effective equivalent to a SignableTransaction. That is declared not by the inputs it spends, yet the outputs it creates. Eventualities are also bound to a 32-byte RNG seed, enabling usage of a hash-based identifier in a SignableTransaction, allowing multiple SignableTransactions with the same output set to have different Eventualities. In order to prevent triggering the burning bug, the RNG seed is hashed with the planned-to-be-used inputs' output keys. While this does bind to them, it's only loosely bound. The TX actually created may use different inputs entirely if a forgery is crafted (which requires no brute forcing). Binding to the key images would provide a strong binding, yet would require knowing the key images, which requires active communication with the spend key. The purpose of this is so a multisig can identify if a Transaction the entire group planned has been executed by a subset of the group or not. Once a plan is created, it can have an Eventuality made. The Eventuality's extra is able to be inserted into a HashMap, so all new on-chain transactions can be trivially checked as potential candidates. Once a potential candidate is found, a check involving ECC ops can be performed. While this is arguably a DoS vector, the underlying Monero blockchain would need to be spammed with transactions to trigger it. Accordingly, it becomes a Monero blockchain DoS vector, when this code is written on the premise of the Monero blockchain functioning. Accordingly, it is considered handled. If a forgery does match, it must have created the exact same outputs the multisig would've. Accordingly, it's argued the multisig shouldn't mind. This entire suite of code is only necessary due to the lack of outgoing view keys, yet it's able to avoid an interactive protocol to communicate key images on every single received output. While this could be locked to the multisig feature, there's no practical benefit to doing so. * Add support for encoding Monero address to instructions * Move Serai's Monero address encoding into serai-client serai-client is meant to be a single library enabling using Serai. While it was originally written as an RPC client for Serai, apps actually using Serai will primarily be sending transactions on connected networks. Sending those transactions require proper {In, Out}Instructions, including proper address encoding. Not only has address encoding been moved, yet the subxt client is now behind a feature. coin integrations have their own features, which are on by default. primitives are always exposed. * Reorganize file layout a bit, add feature flags to processor * Tidy up ETH Dockerfile * Add Bitcoin address encoding * Move Bitcoin::Address to serai-client's * Comment where tweaking needs to happen * Add an API to check if a plan was completed in a specific TX This allows any participating signer to submit the TX ID to prevent further signing attempts. Also performs some API cleanup. * Minimize FROST dependencies * Use a seeded RNG for key gen * Tweak keys from Key gen * Test proper usage of Branch/Change addresses Adds a more descriptive error to an error case in decoys, and pads Monero payments as needed. * Also test spending the change output * Add queued_plans to the Scheduler queued_plans is for payments to be issued when an amount appears, yet the amount is currently pre-fee. One the output is actually created, the Scheduler should be notified of the amount it was created with, moving from queued_plans to plans under the actual amount. Also tightens debug_asserts to asserts for invariants which may are at risk of being exclusive to prod. * Add missing tweak_keys call * Correct decoy selection height handling * Add a few log statements to the scheduler * Simplify test's get_block_number * Simplify, while making more robust, branch address handling in Scheduler * Have fees deducted from payments Corrects Monero's handling of fees when there's no change address. Adds a DUST variable, as needed due to 1_00_000_000 not being enough to pay its fee on Monero. * Add comment to Monero * Consolidate BTC/XMR prepare_send code These aren't fully consolidated. We'd need a SignableTransaction trait for that. This is a lot cleaner though. * Ban integrated addresses The reasoning why is accordingly documented. * Tidy TODOs/dust handling * Update README TODO * Use a determinisitic protocol version in Monero * Test rebuilt KeyGen machines function as expected * Use a more robust KeyGen entropy system * Add DB TXNs Also load entropy from env * Add a loop for processing messages from substrate Allows detecting if we're behind, and if so, waiting to handle the message * Set Monero MAX_INPUTS properly The previous number was based on an old hard fork. With the ring size having increased, transactions have since got larger. * Distinguish TODOs into TODO and TODO2s TODO2s are for after protonet * Zeroize secret share repr in ThresholdCore write * Work on Eventualities Adds serialization and stops signing when an eventuality is proven. * Use a more robust DB key schema * Update to {k, p}256 0.12 * cargo +nightly clippy * cargo update * Slight message-box tweaks * Update to recent Monero merge * Add a Coordinator trait for communication with coordinator * Remove KeyGenHandle for just KeyGen While KeyGen previously accepted instructions over a channel, this breaks the ack flow needed for coordinator communication. Now, KeyGen is the direct object with a handle() function for messages. Thankfully, this ended up being rather trivial for KeyGen as it has no background tasks. * Add a handle function to Signer Enables determining when it's finished handling a CoordinatorMessage and therefore creating an acknowledgement. * Save transactions used to complete eventualities * Use a more intelligent sleep in the signer * Emit SignedTransaction with the first ID *we can still get from our node* * Move Substrate message handling into the new coordinator recv loop * Add handle function to Scanner * Remove the plans timer Enables ensuring the ordring on the handling of plans. * Remove the outputs function which panicked if a precondition wasn't met The new API only returns outputs upon satisfaction of the precondition. * Convert SignerOrder::SignTransaction to a function * Remove the key_gen object from sign_plans * Refactor out get_fee/prepare_send into dedicated functions * Save plans being signed to the DB * Reload transactions being signed on boot * Stop reloading TXs being signed (and report it to peers) * Remove message-box from the processor branch We don't use it here yet. * cargo +nightly fmt * Move back common/zalloc * Update subxt to 0.27 * Zeroize ^1.5, not 1 * Update GitHub workflow * Remove usage of SignId in completed
2023-03-17 02:59:40 +00:00
# Processor
Add support for multiple multisigs to the processor (#377) * 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.
2023-09-25 13:48:15 +00:00
The Serai processor scans a specified external network, communicating with the
coordinator. For details on its exact messaging flow, and overall policies,
please view `docs/processor`.