This repository hosts the smart contracts (program) on Solana network to support ZetaChain cross-chain functionality. Specifically, it consists of a single program deployed (to be deployed; show address here) which allows the following two actions:
- Users on Solana network can send SOL or selected SPL tokens to the program to deposit into ZetaChain and optionally invoke a ZetaChain EVM contract.
- Allows contracts on ZetaChain EVM to withdraw SOL and SPL tokens to users on Solana;
- (TO DO) In the withdraw above, optionally allow a contract on ZetaChain EVM to withdraw SOL/SPL tokens and call a user specified contract (program) with parameters.
Anyone can deposit and remote invoke ZetaChain contracts.
Only ZetaChain TSS account can make withdraw or withdrawAndCall transactions on the program. The ZetaChain TSS account is a collection of Observer/KeySigners which uses ECDSA TSS (Threshold Signature Scheme) to sign outbound transactions. The TSS address will appear in this program a single ECDSA secp256k1 address; but it does not have a single private key, rather its private key consists of multiple key shares and they collectively sign a message in a KeySign MPC ceremony. The program authenticates via verifying the TSS signature and is authorized by ZetaChain to perform outbound transactions as part of ZetaChain cross-chain machinery.
The ZetaChain TSS is on ECDSA secp256k1 curve; But Solana native digital signature scheme is EdDSA Ed25519 curve. Therefore the program uses custom logic to verify the TSS ECDSA signature (like alternative authentication in smart contract wallet); the native transaction signer (fee payer on Solana) does not carry authorization and it's only used to build the transaction and pay tx fees. There are no restrictions on who the native transaction signer/fee payer is. The following code excerpt is for authenticating TSS signature in the contract itself, using the Rust secp256k1 library bundled with solana:
protocol-contracts-solana/programs/protocol-contracts-solana/src/lib.rs
Lines 116 to 121 in 01eeb97
The function recover_eth_address
is implemented in the gateway program:
protocol-contracts-solana/programs/protocol-contracts-solana/src/lib.rs
Lines 180 to 196 in 01eeb97
The TSS signature is a ECDSA secp256k1 signature; its public key therefore address
(Ethereum compatible hashing from pubkey) is therefore verifiable using the secp256k1_recover
function. Alternatively, Solana runtime also privides a program to provide this verification service
via CPI; see proposal 48
which might be more cost efficient.
In both withdraw
and withdrawAndCall
instructions,
the ECDSA signed message_hash must commit to the
nonce
, amount
, and to
address. See the
check in these instructions like:
protocol-contracts-solana/programs/protocol-contracts-solana/src/lib.rs
Lines 110 to 114 in 01eeb97
nonce
in the signature prevents replay of the TSS ECDSA signed message.
Also (to be added in #6) a chain id of Solana
should be added to the commitment of the message hash, so that the signature cannot be replayed on other blockchains
that potentially uses similar authentication (say in TON).
Prerequisites: a recent version of rust
compiler
and cargo
package manger must be installed. The program
is built with the anchor
framework so it needs to be
installed as well; see installation
Please install compatible Solana tools and anchor-cli before build, otherwise the program will not be built successfully
$ solana-install init 1.18.15
$ cargo install --git https://github.com/coral-xyz/anchor --tag v0.30.0 anchor-cli --locked
To show the installed versions of the tools
$ cargo-build-sbf --version
solana-cargo-build-sbf 1.18.15
platform-tools v1.41
rustc 1.75.0
$ anchor --version
anchor-cli 0.30.0
To build (this will require at least 2GB disk space)
$ anchor build
To run the tests
$ anchor test
The Gateway program derive a PDA (Program Derived Address)
with seeds b"meta"
and canonical bump.
This PDA account/address actually holds the SOL
balance of the Gateway program.
For SPL tokens, the program stores the SPL token
in PDA derived ATAs. For each SPL token (different mint
account), the program creates ATA from PDA and the Mint
(standard way of deriving ATA in Solana SPL program).
The PDA account itself is a data account that holds Gateway program state, namely the following data types
protocol-contracts-solana/programs/protocol-contracts-solana/src/lib.rs
Lines 271 to 275 in 01eeb97
The nonce
is incremented on each successful withdraw transaction,
and it's used to prevent replay of signed ECDSA messages.
The tss_address
is the TSS address of ZetaChain (20Bytes,
Ethereum style). authority
is the one who can update
the TSS address stored in PDA account.
The initialize
instruction sets nonce to 0.