crypto: intent signing for TransactionData

[joyqvq]

What is Intent Signing

1. Intent Signing is a new scheme that defines what data the signature is committed to. The intent itself is a domain separator to the data being signed (not only for user signatures, but also for authority signatures). This is to avoid the serialization of the type tag, which is a Rust specific struct name (this is not friendly to other languages).

• In the case of a user transaction, we use one byte u8 to representation the intent scope TransactionData instead of the entire path:

export const TRANSACTION_DATA_TYPE_TAG = Array.from('TransactionData::').map(
  (e) => e.charCodeAt(0)
);

3. The IntentMessage struct is the Intent itself and the generic value (in the case of user transaction, this is the struct TransactionData). Specifically, the intent serializes to three u8 bytes where they represented IntentScope, Version and AppId.

• In Rust

pub struct IntentMessage<T> {
    pub intent: Intent,
    pub value: T,
}

pub struct Intent {
    scope: IntentScope,
    version: IntentVersion,
    app_id: AppId,
}

• In Typescript:

// See: sui/crates/sui-types/src/intent.rs 
// This is currently hardcoded with [IntentScope::TransactionData = 0, Version::V0 = 0, AppId::Sui = 0]
const INTENT_BYTES = [0, 0, 0];

Client Facing Changes

1. To construct a signature

   • In Rust, use Signature::new_secure(intent_message, signer)

   • In Typescript, construct dataToSign using BCS serialized IntentMessage<TransactionData>. This means the signature needs to be committed to the intent bytes and the BCS serialized TransactionData, note that there is no TYPE_TAG anymore.

     const INTENT_BYTES = [0, 0, 0];
     const txBytes = bcs.ser('TransactionData', tx, size).toBytes();
     const intentMessage = new Uint8Array(INTENT_BYTES.length + dataBytes.length);
     intentMessage.set(INTENT_BYTES);
     intentMessage.set(txBytes, INTENT_BYTES.length);        
     dataToSign = new Base64DataBuffer(intentMessage);
     const sig = await this.signData(dataToSign);
     

2. To execute the transaction, use this endpoint The params are described below:

tx_bytes : <Base64> - BCS serialized transaction data bytes, as base-64 encoded string. Note that there is no TYPE_TAG serialized as part of the serialization. 
signature : <Base64> - `flag || signature || pubkey` bytes, as base-64 encoded string, signature is committed to the intent message of the transaction data, as base-64 encoded string.
request_type : <ExecuteTransactionRequestType> - The request type

Changes in this PR

• SenderSignedData now contains IntentMessage<TransactionData> instead of TransactionData (this accounts for majority of LOC here that are trivial to review)
• executeTransaction and executeTransactionSerializedSig RPC now takes in tx_bytes as BCS serialized transaction data without type tag, and the signature should be committed to IntentMessage.
• keystore.sign is now keystore.sign_secure on IntentMessage<TransactionData> instead of TransactionData
• typescript now serialize TransactionData without the type tag (version gated) and append INTENT_BYTES.
• TransactionData::from_signable_bytes(tx_bytes) is replaced by bcs::from_bytes(tx_bytes). This eliminates the type tag and its dep on BCSSignable rust trait

[github-actions]

💳 Wallet Extension has been built, you can download the packaged extension here: https://github.com/MystenLabs/sui/actions/runs/3623059503#artifacts

[github-actions]

💳 Wallet Extension has been built, you can download the packaged extension here: https://github.com/MystenLabs/sui/actions/runs/3658596476#artifacts

[github-actions]

💳 Wallet Extension has been built, you can download the packaged extension here: https://github.com/MystenLabs/sui/actions/runs/3659140538#artifacts

[patrickkuo]

This file has been removed

[github-actions]

💳 Wallet Extension has been built, you can download the packaged extension here: https://github.com/MystenLabs/sui/actions/runs/3659196288#artifacts

[patrickkuo]

LGTM

[github-actions]

💳 Wallet Extension has been built, you can download the packaged extension here: https://github.com/MystenLabs/sui/actions/runs/3660018696#artifacts