Verify an incorporator receipt

import json
import os

import requests
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PublicKey
from cryptography.exceptions import InvalidSignature


def canonical_json(value) -> str:
    """RFC 8785 — JSON Canonicalization Scheme. Use the `rfc8785` library
    in production; the inline form below is illustrative."""
    return json.dumps(
        value,
        sort_keys=True,
        separators=(",", ":"),
        ensure_ascii=False,
    )


def fetch_public_key(livemode: bool) -> bytes:
    url = (
        "https://mattermode.com/keys/incorporator.pub"
        if livemode
        else "https://mattermode.com/keys/incorporator-test.pub"
    )
    res = requests.get(url, timeout=5)
    res.raise_for_status()
    return res.content


def validate_signer_scaffolding(receipt: dict) -> None:
    """New receipts carry signer_stakeholder_id + signer_basis; legacy receipts
    use the deprecated incorporator_identity field. Branch and assert the
    appropriate block is present."""
    if receipt.get("signer_stakeholder_id"):
        basis = receipt.get("signer_basis")
        if basis == "esra_consent" and not receipt.get("consent_record"):
            raise ValueError("esra_consent receipt missing consent_record")
        if basis == "ueta_electronic_agent" and not receipt.get("agent_authority"):
            raise ValueError("ueta_electronic_agent receipt missing agent_authority")
    elif not receipt.get("incorporator_identity"):
        raise ValueError(
            "Receipt has neither signer_stakeholder_id nor legacy incorporator_identity"
        )


def verify_receipt(receipt: dict) -> bool:
    # 1. Branch on signer_basis (or legacy fields) and assert the expected block is present.
    validate_signer_scaffolding(receipt)

    # 2. Recompute the canonical body. The signature itself must be excluded.
    rest = {k: v for k, v in receipt.items() if k != "signature"}
    canonical = canonical_json(rest).encode("utf-8")

    # 3. Verify the Ed25519 signature against the platform-witnessed public key.
    pem = fetch_public_key(receipt["livemode"])
    public_key = serialization.load_pem_public_key(pem)
    if not isinstance(public_key, Ed25519PublicKey):
        raise ValueError("Expected Ed25519 public key")

    signature = bytes.fromhex(receipt["signature"])

    try:
        public_key.verify(signature, canonical)
        return True
    except InvalidSignature:
        return False


# Usage
res = requests.get(
    "https://api.mattermode.com/v1/incorporator_receipts/rcp_8mY3pQrL",
    headers={
        "Authorization": f"Bearer {os.environ['MATTER_KEY']}",
        "Matter-Version": "2026-05-01",
    },
)
res.raise_for_status()
receipt = res.json()

if verify_receipt(receipt):
    print("Receipt verified")
    print(
        f"Founder: {receipt['signer_stakeholder_id']} "
        f"signed via {receipt['signer_basis']}"
    )
else:
    print("Receipt invalid")