dmsg_protocol 0.4.0

Deterministic encoding, COSE document verification, and approval helpers for dMsg
Documentation 
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//! Binding checks complement (never replace) authentication of an ICP certificate.
use crate::*;
use candid::Principal;
use dmsg_types::*;

/// Return the single certified-tree path segment for an execution receipt.
///
/// The 54 bytes are `b"execution/" || account[12] || request[32]`, using raw IDs
/// rather than hex/Xid text. Use this expected path when verifying the IC witness.
pub fn execution_receipt_key(account: &AccountId, request: OpId) -> Vec<u8> {
    [
        b"execution/".as_slice(),
        account.as_slice(),
        request.as_slice(),
    ]
    .concat()
}

/// Verify an artifact and match it against an already authenticated execution receipt.
///
/// The caller must first authenticate the IC certificate, expected user canister,
/// requested account/request path, witness and leaf bytes. This function requires
/// schema 2, then matches issuer, signing-bytes SHA-256, public-key thumbprint
/// and raw-signature SHA-256. It does not independently check account ID,
/// request ID, origin, approval expiry or external application permissions.
///
/// # Errors
/// Propagates artifact verification errors; unsupported receipt schema or
/// mismatched bindings return `Error::IntegrityFailed`.
pub fn match_execution_receipt(
    artifact: &SignedArtifact,
    receipt: &ExecutionReceipt,
) -> Result<()> {
    ensure(receipt.schema == 2, Error::IntegrityFailed)?;
    let verified = verify_and_parse_artifact(artifact)?;
    ensure(
        verified.statement.issuer == receipt.issuer
            && sha256(&verified.signing_bytes()?) == receipt.to_be_signed_digest
            && thumbprint(&verified.key)? == receipt.public_key_fingerprint
            && sha256(verified.message.signature()) == receipt.signature_digest,
        Error::IntegrityFailed,
    )
}

/// Verify an attestation end to end as kept evidence: the artifact's
/// signature, the IC certificate of its execution receipt under a pinned
/// root and home at `execution/<account><request>`, and the receipt's
/// binding to the artifact, account and request. Returns the statement,
/// the receipt and the certificate time in Unix milliseconds.
///
/// It checks no freshness: a receipt proves what the account authorized
/// when it was certified, not that the device is still trusted.
///
/// # Errors
/// Artifact errors propagate; any certificate or binding mismatch returns
/// `Error::IntegrityFailed`.
pub fn verify_attestation(
    artifact: &SignedArtifact,
    receipt: &CertifiedBatch,
    account: &AccountId,
    request: OpId,
    trusted_home: Principal,
    trusted_ic_root_der: &[u8],
) -> Result<(Statement, ExecutionReceipt, u64)> {
    let statement = verify_artifact(artifact)?;
    let key = execution_receipt_key(account, request);
    let (value, at) = crate::authentication::verify_recorded_leaf(
        receipt,
        &key,
        trusted_home,
        trusted_ic_root_der,
    )?;
    let leaf: ExecutionReceipt = decode_canonical(&value)?;
    match_execution_receipt(artifact, &leaf)?;
    ensure(
        leaf.account_id == *account && leaf.request_id == request,
        Error::IntegrityFailed,
    )?;
    Ok((statement, leaf, at))
}