When an AMM account is deleted, the owner directory entries must be
deleted in order to ensure consistent ledger state.
* When deleting AMM account:
* Clean up AMM owner dir, linking AMM account and AMM object
* Delete trust lines to AMM
* Disallow `CheckCreate` to AMM accounts
* AMM cannot cash a check
* Constrain entries in AuthAccounts array to be accounts
* AuthAccounts is an array of objects for the AMMBid transaction
* SetTrust (TrustSet): Allow on AMM only for LP tokens
* If the destination is an AMM account and the trust line doesn't
exist, then:
* If the asset is not the AMM LP token, then fail the tx with
`tecNO_PERMISSION`
* If the AMM is in empty state, then fail the tx with `tecAMM_EMPTY`
* This disallows trustlines to AMM in empty state
* Add AMMID to AMM root account
* Remove lsfAMM flag and use sfAMMID instead
* Remove owner dir entry for ltAMM
* Add `AMMDelete` transaction type to handle amortized deletion
* Limit number of trust lines to delete on final withdraw + AMMDelete
* Put AMM in empty state when LPTokens is 0 upon final withdraw
* Add `tfTwoAssetIfEmpty` deposit option in AMM empty state
* Fail all AMM transactions in AMM empty state except special deposit
* Add `tecINCOMPLETE` to indicate that not all AMM trust lines are
deleted (i.e. partial deletion)
* This is handled in Transactor similar to deleted offers
* Fail AMMDelete with `tecINTERNAL` if AMM root account is nullptr
* Don't validate for invalid asset pair in AMMDelete
* AMMWithdraw deletes AMM trust lines and AMM account/object only if the
number of trust lines is less than max
* Current `maxDeletableAMMTrustLines` = 512
* Check no directory left after AMM trust lines are deleted
* Enable partial trustline deletion in AMMWithdraw
* Add `tecAMM_NOT_EMPTY` to fail any transaction that expects an AMM in
empty state
* Clawback considerations
* Disallow clawback out of AMM account
* Disallow AMM create if issuer can claw back
This patch applies to the AMM implementation in #4294.
Acknowledgements:
Richard Holland and Nik Bougalis for responsibly disclosing this issue.
Bug Bounties and Responsible Disclosures:
We welcome reviews of the project code and urge researchers to
responsibly disclose any issues they may find.
To report a bug, please send a detailed report to:
bugs@xrpl.org
Signed-off-by: Manoj Doshi <mdoshi@ripple.com>
- Add support for all transaction types and ledger object types to gRPC
implementation of tx and account_tx.
- Create common handlers for tx and account_tx.
- Remove mutex and abort() from gRPC server. JobQueue is stopped before
gRPC server, with all coroutines executed to completion, so no need for
synchronization.
The XRP Ledger utilizes an account model. Unlike systems based on a UTXO
model, XRP Ledger accounts are first-class objects. This design choice
allows the XRP Ledger to offer rich functionality, including the ability
to own objects (offers, escrows, checks, signer lists) as well as other
advanced features, such as key rotation and configurable multi-signing
without needing to change a destination address.
The trade-off is that accounts must be stored on ledger. The XRP Ledger
applies reserve requirements, in XRP, to protect the shared global ledger
from growing excessively large as the result of spam or malicious usage.
Prior to this commit, accounts had been permanent objects; once created,
they could never be deleted.
This commit introduces a new amendment "DeletableAccounts" which, if
enabled, will allow account objects to be deleted by executing the new
"AccountDelete" transaction. Any funds remaining in the account will
be transferred to an account specified in the deletion transaction.
The amendment changes the mechanics of account creation; previously
a new account would have an initial sequence number of 1. Accounts
created after the amendment will have an initial sequence number that
is equal to the ledger in which the account was created.
Accounts can only be deleted if they are not associated with any
obligations (like RippleStates, Escrows, or PayChannels) and if the
current ledger sequence number exceeds the account's sequence number
by at least 256 so that, if recreated, the account can be protected
from transaction replay.
The lsfDepositAuth flag limits the AccountIDs that can deposit into
the account that has the flag set. The original design only
allowed deposits to complete if the account with the flag set also
signed the transaction that caused the deposit.
The DepositPreauth ledger type allows an account with the
lsfDepositAuth flag set to preauthorize additional accounts.
This preauthorization allows them to sign deposits as well. An
account can add DepositPreauth objects to the ledger (and remove
them as well) using the DepositPreauth transaction.
