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Hamdi Allam dff24e9fca
op-txproxy: external validating proxy for conditional transactions (#42) 
* txpool svc

* change mod github path

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2024-09-30 13:43:34 -07:00

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op-txproxy

A supplemental passthrough proxy for some execution engine endpoints. This proxy does not forward all rpc traffic and only exposes a specific set of endpoints. Operationally, the public ingress proxy should only re-route requests for these endpoints.

stateDiagram-v2
    proxyd --> txproxy: intercepted methods
    proxyd --> backend: unintercepted methods
    txproxy --> backend

Setup

Install go 1.21

make build
./bin/op-txproxy --help

Endpoints

eth_sendRawTransactionConditional

An outcome of how to integrate this spec safely for permissionless 4337 bundler participation. This solution in the design doc proposal requires a validating proxy that can be horizontally scaled and pre-emptively reject invalid conditional transaction. The implemented endpoint covers these objectives:

  1. Auth. preemptively put in place to enable a variety of auth policies (allowlist, rate limits, etc).

    The caller authenticates themselves with any valid ECDSA-secp256k1 key, like an Ethereum key. The computed signature is over the EIP-191 hash of the request body (up to the 5MB request body limit).

    With the signature and signing address, the request is authenticated via the X-Optimism-Signature header of the request with the value <public key address>: <signature>.

  2. Rate Limits. global rate limits on the endpoint are applied here.

  3. Rejection Switch. this proxy can be rolled with a flag/env switch to reject conditional transaction without needing to interrupt the execution engine.

  4. Basic Validation. stateless validation is done in the endpoint to reject invalid conditional transactions and apply additional restricts on the usage (only 4337 entrypoint tx target support).

  5. Metrics. performance of this endpoint can be observed in order to inform adjustments to rate limits, shutoff, or auth policies to implement.