How to verify an ETH signature on Solana?

Question

I am hoping to write a very simple program that accepts an ETH signature, ETH public key, and message --> determines if the signature is valid.

I found the following repo that looks to do what I want it to do, but I don't understand how it works... https://github.com/GuidoDipietro/solana-ed25519-secp256k1-sig-verification/tree/master

I am getting the ETH signature in the following format

{
  "input": {
    "keyNo": 1,
    "digest": "bcf83051a4d206c6e43d7eaa4c75429737ac0d5ee08ee68430443bd815e6ac05",
    "message": "010203"
  },
  "signature": {
    "raw": {
      "r": "93137bc7bfeaa86e26c6a9bbd6fb8acdf73ed5fd232cc2be1a0714f583f04d2e",
      "s": "7f5d7c2461daf8649587c3c510fce05a74146cbe79341427065d0d878d154a1b",
      "v": 27
    },
    "der": "304602210093137bc7bfeaa86e26c6a9bbd6fb8acdf73ed5fd232cc2be1a0714f583f04d2e02210080a283db9e25079b6a783c3aef031fa4469a702836148c14b97551054320f726",
    "ether": "0x93137bc7bfeaa86e26c6a9bbd6fb8acdf73ed5fd232cc2be1a0714f583f04d2e7f5d7c2461daf8649587c3c510fce05a74146cbe79341427065d0d878d154a1b1b"
  },
  "publicKey": "046ca7458b4c8c4f9a196094bda5f01ac1e588f6604bc2f7a58ba4d1fa3c3cb9102720bdb43f73972ea3dfc1c6ab8a6cb7d14114765eb76ff0fb2df34a5f7cab56",
  "etherAddress": "0x1aaBF638eC3c4A5C2D5cD14fd460Fee2c364c579"
}

and will pass some or all of these values to the program.

I found these two native program which could be helpful, but I don't understand how to use them: https://docs.solana.com/developing/runtime-facilities/programs#ed25519-program https://docs.solana.com/developing/runtime-facilities/programs#secp256k1-program

Any and all guidance will be hugely appreciated.

Answer 1

All of the information you need should be provided at the source code for the instruction: https://github.com/solana-labs/solana/blob/a099c7a0b8ac4281dbc6dd422d697e700c28a7d1/sdk/program/src/secp256k1_recover.rs#L399

With the signature and message, you can run:

     let recovered_pubkey = secp256k1_recover(
         // input.digest as bytes here
         // "v" here
         // concatenated bytes of "r" and "s" here
     )
     .map_err(|_| ProgramError::InvalidArgument)?;

And then compare the recovered_pubkey to the expected pubkey.