NZCP.sol

An implementation of the NZ COVID Pass spec in Solidity.

Features

• Verifies NZCP pass and returns the credential subject (givenName, familyName, dob)
• Reverts transaction if pass is invalid.
• To save gas, the full pass URI is not passed into the contract, but merely the ToBeSigned value.
  • ToBeSigned value is enough to cryptographically prove that the pass is valid.
  • The definition of ToBeSigned can be found here: https://datatracker.ietf.org/doc/html/rfc8152#section-4.4

Assumptions

• The NZ Ministry of Health is never going to sign any malformed CBOR
  • This assumption relies on the internal implementation of https://mycovidrecord.nz
• The NZ Ministry of Health is never going to sign any pass that is not active
  • This assumption relies on the internal implementation of https://mycovidrecord.nz
• The NZ Ministry of Health is never going to change the private-public key pair used to sign the pass
  • This assumption relies on trusting the NZ Ministry of Health not to leak their private key

Privacy implications

When you call NZCP.readCredSubjExample/NZCP.readCredSubjLive function as part of a transaction, your pass gets stored on blockchain as calldata. This allows 3rd parties to read your COVID pass and reconstruct your NZCP QR code, effectively making your pass public. This is bad since your pass could be then used by anyone. Never verify live passes as part of a transaction on a deployed version of this contract.

Contrary to using NZCP.readCredSubjExample/NZCP.readCredSubjLive function as part of a transaction, using it as merely a view function (e.g. when calling it via "Read Contract" feature on Etherscan) is fine since execution of a view function happens off-chain.

Please note that the limitations above make any practical use of this contract on live passes to be dangerous.

Usage

• Prepare ToBeSigned value and the rs array by calling getToBeSignedAndRs from jslib/nzcp.js on your pass URI
• Call either nzcp.readCredSubjExample(ToBeSigned, rs) or nzcp.readCredSubjLive(ToBeSigned, rs) to verify your pass and get the credential subject

Requirements

• Install Hardhat

Building

• Run make to build the project
• You can build without the live pass verification or without the example pass verification by supplying DFLAGS environment variable into the make command.
  • make DFLAGS=-DEXPORT_EXAMPLE_FUNCS to build only example pass verification
  • make DFLAGS=-DEXPORT_LIVE_FUNCS to build only live pass verification

Tests

• Create .env file in the root directory of the project
• Populate it with at least 1 live pass URI.
  • Use .env.example as a reference.
• Run make test

Deploying

• Populate .env with ALCHEMY_API_KEY and ROPSTEN_PRIVATE_KEY
• Run make deploy DFLAGS=-DEXPORT_EXAMPLE_FUNCS NETWORK=hardhat to test deploying
• Run make deploy DFLAGS=-DEXPORT_EXAMPLE_FUNCS NETWORK=ropsten to deploy on Ropsten testnet
  • WARNING: Please don't deploy live pass verification to any remote network, as because executing the verify function as part of a transaction will result in the pass getting stored as calldata on the blockchain and effectively being public.

Gas Usage

Running tests consumes 1429033 gas units (optimizer enabled, 1000 runs)

Deployed version of the contract

Ropsten testnet: https://ropsten.etherscan.io/address/0x14ffb19a685bb8ec4b925604280f7e441a343af9 (example passes only)

• Test readCredSubjExample with the arguments:
  • ToBeSigned: 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
  • rs: [0xD2E07B1DD7263D833166BDBB4F1A093837A905D7ECA2EE836B6B2ADA23C23154,0xFBA88A529F675D6686EE632B09EC581AB08F72B458904BB3396D10FA66D11477]

• Test verifySignExample with the arguments:
  • messageHash: 0x271CE33D671A2D3B816D788135F4343E14BC66802F8CD841FAAC939E8C11F3EE
  • rs: [0xD2E07B1DD7263D833166BDBB4F1A093837A905D7ECA2EE836B6B2ADA23C23154,0xFBA88A529F675D6686EE632B09EC581AB08F72B458904BB3396D10FA66D11477]

Audits

N/A