Secure the Solana Ecosystem (6) — Multi-Sig2
In the previous post, we discussed the implementation of the Multi-Sig. However, the implementation assumes that the signatures from multiple users can be collected at the same time off-chain. In this post, we introduce a more general Multi-sig program that allows users to sign fully on-chain.
2. Design Of Test Program
The multi-sig program allows valid signers to sign the proposer in separate and anyone can execute the proposer once it is approved (enough signatures are collected). All the test code can be found here.
3. Code Review
This program introduces two more structs and they are
TransactionAccount is designed for recording the account information used for the proposed transaction. Struct
Transaction is used to record the information of a proposal. Note that the attribute
signers is used to record the number of valid signatures.
is_initialized ensure the execution and the initialization can only be done once.
The program provides five different instructions. Instruction
AllocatePDA aims to create a unique PDA account, and uses it as the
multisig account. It will record all the valid signers' information. In instruction
InitializeMultisig, we set the number of signatures required to execute the instruction, and the array of valid signers' public keys as well. Instruction
CreateTransaction is used to create a proposal while signer can approve the proposal via the instruction
approve. Once the number of the approval reaches the threshold set in
multisig, the instruction
ExecuteTransaction can be invoked to execute the transaction.
To submit a proposal, users can invoke the instruction
createTransaction(). It takes three accounts, which are created
transaction account, the next two accounts are used by the target transaction. To prevent the account from being re-initialized by malicious users, we check the attribute
is_initialized (line 161-163). After that, we init the struct
TransactionAccount with specified data and serialize it into the data account(line 188).
Approve(), we first check whether the
Transaction account and the
multisig account are owned by the program. Note that accounts created from other programs may be used by malicious users here if there is no check. Next, we match the pubkey of the signer with the keys stored in
multisig account. If matched, it will validate your signature, and change the value to
ExecuteTransaction(), we count the number of valid signatures. If the number doesn't reach the threshold, the program will revert.
After that, we init the target
Instruction with specified attributes and invoke the instruction of the target program via the function
invoke_signed(). We finally set the attribute
did_execute to true in case the proposal is executed repeatedly.
We deployed the program on testnet and it can be find in the following link.
4. Send Transaction
After the deployment, we create the
multisig account first and set the
multisig account as the admin of the
config account when initialize the
config account. Related transactions are shown below, and the order is:
createMultisig()(in General-Multisig) -> Deploy PriviligeOwner program ->
Allocate() (in PrivligeOwner) ->
InitializeConfig() (in PrivligeOwner).
Next, we invoke instruction
InitializeMultisig(). We pass in four accounts and they are the
multisig account and three valid signer's accounts. We set the value of
m to 2, which means two of the three signers' signatures is required to execute privilege functions.
CreateTransaction(), we pass in the created
Transaction account, the pubkey of the target program (PrivilegeOwner) and the pubkey of the
config account (line 306 -line 307). Besides, we should also set the
_data to 3, which corresponds to the instruction
unlock() in PrivilegeOwner program.
For the first test, only one signer approves the created proposal. In this case,
ExecuteTransaction() fails as limited signatures are collected. The console prints the following output.
Another signer approves the created proposal and invokes
ExecuteTransaction(). The total number of signatures has reached to the threshold so that the proposal can be executed successfully.
In this article, we introduce the general implementation of the multisig in Solana. The implementation makes use of the feature of PDA, which enables the program to sign the transaction by PDA automatically when the number of valid signatures meets the requirement. Keep following, and we will share more in the upcoming posts.