verifier

Attestation Verifier

The attestation verifier verifies attestations provided by the attestation server containing a secp256k1 public key and signs the response using its own secp256k1 key. Intended to be run inside an enclave to provide cheap attestation verification services.

Once the attestation of the verifier is verified on-chain (very expensive), it enables other enclaves, including other verifiers, to get verified by submitting a simple ECDSA signature from the verifier instead (very cheap). The process essentially extends the chain of trust of the attestation verifier enclave instead of trying to verify the full attestation of the other enclave again.

Build

cargo build --release

Reproducible builds

Reproducible builds can be done using Nix. The monorepo provides a Nix flake which includes this project and can be used to trigger builds:

nix build -v .#<flavor>.attestation.verifier.<output>

Supported flavors:

• gnu
• musl

Supported outputs:

• default, same as compressed
• uncompressed
• compressed, using upx

Test

cargo test

Usage

$ ./target/release/oyster-attestation-verifier --help
Usage: oyster-attestation-verifier --secp256k1-secret <SECP256K1_SECRET> --secp256k1-public <SECP256K1_PUBLIC> --ip <IP> --port <PORT>

Options:
      --secp256k1-secret <SECP256K1_SECRET>
          path to secp256k1 private key file (e.g. /app/secp256k1.sec)
      --secp256k1-public <SECP256K1_PUBLIC>
          path to secp256k1 public key file (e.g. /app/secp256k1.pub)
  -i, --ip <IP>
          server ip (e.g. 127.0.0.1)
  -p, --port <PORT>
          server port (e.g. 1400)
  -h, --help
          Print help
  -V, --version
          Print version

Endpoints

The attestation verifier exposes two verification endpoints which expect the attestation in one of two formats - raw and hex. The formats match the two endpoints of the attestation server and the response of the server can just be sent to the verifier as is.

Raw

Endpoint

/verify/raw

Example

$ curl <attestation_server_ip:attestation_server_port>/attestation/raw -vs | curl -H "Content-Type: application/octet-stream" --data-binary @- <attestation_verifier_ip:attestation_verifier_port>/verify/raw -vs
*   Trying <attestation_server_ip:attestation_server_port>...
* Connected to <attestation_server_ip> (<attestation_server_ip>) port <attestation_server_port> (#0)
> GET /attestation/raw HTTP/1.1
> Host: <attestation_server_ip:attestation_server_port>
> User-Agent: curl/7.81.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-type: application/octet-stream
< content-length: 4468
< date: Sun, 07 Apr 2024 06:36:44 GMT
< 
{ [2682 bytes data]
* Connection #0 to host <attestation_server_ip> left intact
*   Trying <attestation_verifier_ip:attestation_verifier_port>...
* Connected to <attestation_verifier_ip> (<attestation_verifier_ip>) port <attestation_verifier_port> (#0)
> POST /verify/raw HTTP/1.1
> Host: <attestation_verifier_ip:attestation_verifier_port>
> User-Agent: curl/7.81.0
> Accept: */*
> Content-Type: application/octet-stream
> Content-Length: 4468
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-length: 799
< content-type: application/json
< date: Sun, 07 Apr 2024 06:36:44 GMT
< 
* Connection #0 to host <attestation_verifier_ip> left intact
{"signature":"15383a7af2c33e80eba2637c9e3fb0c246ecedfbb183879f9dc9b18d25635b3871212cfab51db0fd75dded5be870febe19226c92d38425c37689fb7c1e86f74f1c","image_id":"3fe8419454c44a36782f2b9a307cad84ee8c226e0351cb0861c50fb6b13a3a3e","timestamp_ms":1738845553218,"public_key":"435ed75cf1be0c58b97d372b153ad4e43101895e481e7dd7d27519605e859f34d7b5491586faa887257178bbb6daa1e212f35aa2a60308cd76df5db522abb139","user_data":"12345678","verifier_public_key":"60b77877f624b4eaf776a6afef1dd727f969c7557b88b05cc27c51366eafd72a2328b054bd2f6cec47b3b82b61bbfc898b5b32d604446ebf59e50195345a8d98"}

Hex

Endpoint

/attestation/hex

Example

$ curl <attestation_server_ip:attestation_server_port>/attestation/hex -vs | curl -H "Content-Type: text/plain" -d @- <attestation_verifier_ip:attestation_verifier_port>/verify/hex -vs
*   Trying <attestation_server_ip:attestation_server_port>...
* Connected to <attestation_server_ip> (<attestation_server_ip>) port <attestation_server_port> (#0)
> GET /attestation/hex HTTP/1.1
> Host: <attestation_server_ip:attestation_server_port>
> User-Agent: curl/7.81.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-type: text/plain; charset=utf-8
< content-length: 8936
< date: Sun, 07 Apr 2024 06:44:25 GMT
< 
{ [2681 bytes data]
* Connection #0 to host <attestation_server_ip> left intact
*   Trying <attestation_verifier_ip:attestation_verifier_port>...
* Connected to <attestation_verifier_ip> (<attestation_verifier_ip>) port <attestation_verifier_port> (#0)
> POST /verify/hex HTTP/1.1
> Host: <attestation_verifier_ip:attestation_verifier_port>
> User-Agent: curl/7.81.0
> Accept: */*
> Content-Type: text/plain
> Content-Length: 8936
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-length: 799
< content-type: application/json
< date: Sun, 07 Apr 2024 06:44:25 GMT
< 
* Connection #0 to host <attestation_verifier_ip> left intact
{"signature":"15383a7af2c33e80eba2637c9e3fb0c246ecedfbb183879f9dc9b18d25635b3871212cfab51db0fd75dded5be870febe19226c92d38425c37689fb7c1e86f74f1c","image_id":"3fe8419454c44a36782f2b9a307cad84ee8c226e0351cb0861c50fb6b13a3a3e","timestamp_ms":1738845553218,"public_key":"435ed75cf1be0c58b97d372b153ad4e43101895e481e7dd7d27519605e859f34d7b5491586faa887257178bbb6daa1e212f35aa2a60308cd76df5db522abb139","user_data":"12345678","verifier_public_key":"60b77877f624b4eaf776a6afef1dd727f969c7557b88b05cc27c51366eafd72a2328b054bd2f6cec47b3b82b61bbfc898b5b32d604446ebf59e50195345a8d98"}

Response format

{
    "signature": "...",
    "image_id": "...",
    "timestamp_ms": ...,
    "public_key": "...",
    "user_data": "...",
    "verifier_public_key": "..."
}

The verifier responds with JSON with the following fields:

• signature: signature provided by the verifier
• image_id: hash of PCRs encoded in the attestation
• timestamp_ms: timestamp that was encoded in the attestation
• public_key: public key that was encoded in the attestation
• user_data: user data that was encoded in the attestation
• verifier_public_key: public key of the verifier corresponding to the signature

Signature format

The verifier creates the signature as per the EIP-712 standard.

EIP-712 domain

struct EIP712Domain {
    string name = "marlin.oyster.AttestationVerifier",
    string version = "1",
}

The chainId, verifyingContract and salt fields are omitted because we do not see any significant replay concerns in allowing the signature to be verified on any contract on any chain.

Message struct

struct Attestation {
    bytes32 imageId;
    uint64 timestampMs;
    bytes publicKey;
    bytes userData;
}

Verification

It is designed to be verified by the following solidity code (taken from the AttestationVerifier contract):

    /// @notice EIP-712 domain separator
    bytes32 public constant DOMAIN_SEPARATOR = keccak256(
        abi.encode(
            keccak256("EIP712Domain(string name,string version)"),
            keccak256("marlin.oyster.AttestationVerifier"),
            keccak256("1")
        )
    );

    /// @notice EIP-712 typehash for attestation struct
    bytes32 public constant ATTESTATION_TYPEHASH =
        keccak256("Attestation(bytes32 imageId,uint64 timestampMs,bytes publicKey,bytes userData)");

    /// @notice Verifies a signed attestation using EIP-712 signatures
    /// @param _signature ECDSA signature of the attestation
    /// @param _attestation Attestation data structure to verify
    function verify(bytes calldata _signature, Attestation calldata _attestation) external view {
        bytes32 _hashStruct = keccak256(
            abi.encode(
                ATTESTATION_TYPEHASH,
                _attestation.imageId,
                _attestation.timestampMs,
                keccak256(_attestation.publicKey),
                keccak256(_attestation.userData)
            )
        );
        bytes32 _digest = keccak256(abi.encodePacked("\x19\x01", DOMAIN_SEPARATOR, _hashStruct));

        address _signer = ECDSA.recover(_digest, _signature);
        _ensureKeyVerified(bytes32(uint256(uint160(_signer))));
    }

License

This project is licensed under the GNU AGPLv3 or any later version. See LICENSE.txt.