ic-auth 0.2.10

Application authentication encoding and optional IC signature, token and local session machinery
Documentation 
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use super::{RootKeyPolicy, TokenVerificationError, binding, window};
use crate::canonical::{
    chain_key_batch_header_hash, chain_key_delegation_cert_hash, chain_key_derivation_path_hash,
};
use ic_auth_protocol_types::{
    ChainKeyAlgorithm, ChainKeyBatchWitnessStepV1, ChainKeyBatchWitnessV1, DelegationCert,
    RootProof,
};
use k256::ecdsa::{Signature, VerifyingKey, signature::hazmat::PrehashVerifier};
use sha2::{Digest, Sha256};

pub(super) fn verify(
    cert: &DelegationCert,
    root: &RootProof,
    policy: &RootKeyPolicy,
    now_ns: u64,
    max_future_skew_ns: u64,
) -> Result<(), TokenVerificationError> {
    let RootProof::IcChainKeyBatchSignatureV1(proof) = root;
    let header = &proof.header;
    let leaf = &proof.delegation_cert;
    let signature = &proof.signature;
    binding(header.schema_version == 1, "schema_version")?;
    binding(
        header.root_canister_id == policy.root_canister_id
            && leaf.root_canister_id == header.root_canister_id,
        "root_canister_id",
    )?;
    window(
        "root_key_policy",
        policy.valid_from_ns,
        policy.accept_until_ns,
        now_ns,
        max_future_skew_ns,
    )?;
    window(
        "batch",
        header.not_before_ns,
        header.expires_at_ns,
        now_ns,
        max_future_skew_ns,
    )?;
    window(
        "issuer_leaf",
        leaf.not_before_ns,
        leaf.expires_at_ns,
        now_ns,
        max_future_skew_ns,
    )?;
    binding(
        leaf.not_before_ns >= header.not_before_ns && leaf.expires_at_ns <= header.expires_at_ns,
        "leaf_batch_window",
    )?;
    binding(leaf.proof_epoch == header.proof_epoch, "proof_epoch")?;
    binding(
        leaf.registry_epoch == header.registry_epoch,
        "registry_epoch",
    )?;
    binding(leaf.registry_hash == header.registry_hash, "registry_hash")?;
    binding(
        leaf.issuer_canister_id == cert.issuer_pid,
        "issuer_canister_id",
    )?;
    binding(
        leaf.issuer_proof_algorithm == cert.issuer_proof_alg,
        "issuer_proof_algorithm",
    )?;
    binding(
        leaf.issuer_proof_binding_hash == cert.issuer_proof_binding_hash
            && leaf.issuer_proof_binding == cert.issuer_proof_binding,
        "issuer_proof_binding",
    )?;
    binding(
        leaf.max_token_ttl_ns == cert.max_token_ttl_ns,
        "max_token_ttl",
    )?;
    binding(leaf.audience == cert.aud, "leaf_audience")?;
    binding(leaf.grants == cert.grants, "leaf_grants")?;
    binding(
        leaf.not_before_ns == cert.not_before_ns && leaf.expires_at_ns == cert.expires_at_ns,
        "leaf_cert_window",
    )?;
    binding(
        header.algorithm == policy.algorithm && signature.algorithm == header.algorithm,
        "algorithm",
    )?;
    binding(
        header.key_id == policy.key_id && signature.key_id == header.key_id,
        "key_id",
    )?;
    binding(signature.public_key == policy.public_key, "root_public_key")?;
    binding(
        header.derivation_path_hash == policy.derivation_path_hash
            && chain_key_derivation_path_hash(&signature.derivation_path)?
                == header.derivation_path_hash,
        "derivation_path_hash",
    )?;
    binding(header.key_version == policy.key_version, "key_version")?;
    for (field, found, minimum) in [
        (
            "key_version",
            header.key_version,
            policy.min_accepted_key_version,
        ),
        (
            "proof_epoch",
            header.proof_epoch,
            policy.min_accepted_proof_epoch,
        ),
        (
            "registry_epoch",
            header.registry_epoch,
            policy.min_accepted_registry_epoch,
        ),
    ] {
        if found < minimum {
            return Err(TokenVerificationError::StaleAuthority { field });
        }
    }
    let ttl_ns = header.expires_at_ns - header.not_before_ns;
    if ttl_ns > policy.max_revocation_latency_ns {
        return Err(TokenVerificationError::TtlExceeded {
            target: "batch",
            ttl_ns,
            max_ttl_ns: policy.max_revocation_latency_ns,
        });
    }
    let leaf_hash = chain_key_delegation_cert_hash(leaf)?;
    if witness_root(leaf_hash, &proof.issuer_witness) != header.tree_root {
        return Err(TokenVerificationError::InvalidMerkleWitness);
    }
    // SEC1 parsing, scalar range validation and high-s detection belong to k256.
    let ChainKeyAlgorithm::EcdsaSecp256k1 = signature.algorithm;
    let key = VerifyingKey::from_sec1_bytes(&policy.public_key)
        .map_err(|_| TokenVerificationError::RootSignatureInvalid)?;
    let signature = Signature::from_slice(&signature.signature)
        .map_err(|_| TokenVerificationError::RootSignatureInvalid)?;
    if signature.normalize_s().is_some() {
        return Err(TokenVerificationError::HighSSignature);
    }
    key.verify_prehash(&chain_key_batch_header_hash(header)?, &signature)
        .map_err(|_| TokenVerificationError::RootSignatureInvalid)
}

fn witness_root(leaf: [u8; 32], witness: &ChainKeyBatchWitnessV1) -> [u8; 32] {
    witness.steps.iter().fold(leaf, |current, step| {
        let (left, right) = match step {
            ChainKeyBatchWitnessStepV1::LeftSibling(hash) => (*hash, current),
            ChainKeyBatchWitnessStepV1::RightSibling(hash) => (current, *hash),
        };
        let mut hasher = Sha256::new();
        hasher.update([1]);
        hasher.update(left);
        hasher.update(right);
        hasher.finalize().into()
    })
}