quantum-sign 0.1.7

//! RFC 3161 timestamping (client/validator).
#![forbid(unsafe_code)]
#![deny(missing_docs)]

use core::fmt;
use der::{Decode, Encode};
use der::referenced::OwnedToRef;
use sha2::Digest as _;

/// Errors returned by timestamping operations.
#[derive(Debug)]
pub enum Error {
    /// HTTP failure or non-success status code.
    Http(String),
    /// ASN.1/DER or CMS parsing error.
    Parse(String),
    /// Verification error (status, imprint, nonce, or chain).
    Verify(String),
    /// Unsupported or unknown digest algorithm.
    Digest(String),
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Error::Http(e) => write!(f, "http: {e}"),
            Error::Parse(e) => write!(f, "parse: {e}"),
            Error::Verify(e) => write!(f, "verify: {e}"),
            Error::Digest(e) => write!(f, "digest: {e}"),
        }
    }
}

impl std::error::Error for Error {}

/// Timestamp request parameters.
pub struct TsaRequest {
    /// Hash algorithm name ("sha512" | "shake256-64").
    pub imprint_alg: &'static str,
    /// Digest of the message to be timestamped (e.g., qsig.digest)
    pub imprint: Vec<u8>,
    /// Optional TSA policy OID string.
    pub policy_oid: Option<String>,
    /// 128-bit nonce suggested by the client.
    pub nonce: [u8; 16],
    /// Whether the TSA should include the certificate chain.
    pub cert_req: bool,
}

/// Minimal verified metadata extracted from a TSA response.
#[derive(Clone, Debug)]
pub struct TsaResponse {
    /// Raw DER `TimeStampResp`.
    pub der: Vec<u8>,
    /// `genTime` as UNIX seconds.
    pub gen_time_unix: i64,
    /// Token serial number as lowercase hex.
    pub serial_hex: String,
    /// TSA signer key identifier derived from SPKI DER.
    pub tsa_kid: String,
}

/// Construct a DER-encoded `TimeStampReq` and POST to the TSA.
pub fn request_timestamp(url: &str, req: &TsaRequest) -> Result<TsaResponse, Error> {
    let der_req = build_timestamp_req_der(req)?;
    let mut res = ureq::post(url)
        .content_type("application/timestamp-query")
        .send(der_req.as_slice())
        .map_err(|e| Error::Http(e.to_string()))?;
    let der = res
        .body_mut()
        .read_to_vec()
        .map_err(|e| Error::Http(e.to_string()))?;
    parse_basic_response(&der)
}

/// Verify a DER `TimeStampToken` inside a `TimeStampResp` against expectations.
pub fn verify_token(
    der: &[u8],
    expected_alg: &str,
    expected_imprint: &[u8],
    expected_nonce: Option<&[u8]>,
    trust_anchors: &[Vec<u8>],
) -> Result<TsaResponse, Error> {
    // Parse outer response
    let tsr = x509_tsp::TimeStampResp::from_der(der).map_err(|e| Error::Parse(e.to_string()))?;
    let status_val = tsr.status.status as u8;
    if status_val > 1 {
        return Err(Error::Verify(format!("status {} not granted", status_val)));
    }
    let tst = tsr
        .time_stamp_token
        .ok_or_else(|| Error::Parse("missing token".into()))?;
    let tst_der = tst.to_der().map_err(|e| Error::Parse(e.to_string()))?;

    // Parse CMS ContentInfo -> SignedData, get eContent (TSTInfo) and signer cert SPKI
    let sd = cms::content_info::ContentInfo::from_der(&tst_der)
        .map_err(|e| Error::Parse(format!("cms: {e}")))?;
    let (tst_info_der, signer_spki, serial_hex, signer_cert, chain) =
        extract_tstinfo_and_signer_spki(&sd).map_err(|e| Error::Parse(e))?;

    let tsti = x509_tsp::TstInfo::from_der(&tst_info_der).map_err(|e| Error::Parse(e.to_string()))?;
    verify_message_imprint(&tsti, expected_alg, expected_imprint)?;
    if let (Some(nonce), Some(exp)) = (tsti.nonce.as_ref(), expected_nonce) {
        if nonce.as_bytes() != exp {
            return Err(Error::Verify("nonce mismatch".into()));
        }
    }

    // Verify EKU + bind to provided anchors by SPKI KID, then verify CMS signature
    verify_eku_and_trust(&signer_cert, &chain, trust_anchors)?;
    let signer_der = signer_cert.to_der().map_err(|e| Error::Parse(format!("signer der: {e}")))?;
    verify_cms_signed_attrs(&sd, &signer_der, &signer_spki)?;
    let tsa_kid = crate::crypto::kid_from_spki_der(&signer_spki);
    let gen_time_unix = tsti.gen_time.to_unix_duration().as_secs() as i64;
    Ok(TsaResponse {
        der: der.to_vec(),
        gen_time_unix,
        serial_hex,
        tsa_kid,
    })
}

/* ------------------- internals ------------------- */

fn build_timestamp_req_der(req: &TsaRequest) -> Result<Vec<u8>, Error> {
    // Use the x509-tsp structures to encode a minimal TimeStampReq.
    use cms::cert::x509::spki::AlgorithmIdentifier;
    use der::asn1::{Int, OctetString};
    use der::oid::ObjectIdentifier;
    use x509_tsp::{MessageImprint, TimeStampReq, TspVersion};

    let alg_oid: ObjectIdentifier = match req.imprint_alg {
        "sha512" => const_oid::db::rfc5912::ID_SHA_512,
        // SHAKE256 OID (2.16.840.1.101.3.4.2.12); truncation length is not part of OID
        "shake256-64" => ObjectIdentifier::new_unwrap("2.16.840.1.101.3.4.2.12"),
        other => return Err(Error::Digest(other.into())),
    };

    let alg = AlgorithmIdentifier { oid: alg_oid, parameters: None };
    let hashed_message = OctetString::new(req.imprint.clone())
        .map_err(|e| Error::Parse(e.to_string()))?;
    let imprint = MessageImprint { hash_algorithm: alg, hashed_message };
    let tsreq = TimeStampReq {
        version: TspVersion::V1,
        message_imprint: imprint,
        req_policy: req.policy_oid.as_deref().and_then(|s| s.parse().ok()),
        nonce: Some(Int::new(&req.nonce).map_err(|e| Error::Parse(e.to_string()))?),
        cert_req: req.cert_req,
        extensions: None,
    };
    tsreq
        .to_der()
        .map_err(|e| Error::Parse(format!("encode req: {e}")))
}

fn parse_basic_response(der: &[u8]) -> Result<TsaResponse, Error> {
    let tsr = x509_tsp::TimeStampResp::from_der(der).map_err(|e| Error::Parse(e.to_string()))?;
    let status_val = tsr.status.status as u8;
    if status_val > 1 {
        return Err(Error::Verify(format!("status {} not granted", status_val)));
    }
    let tst = tsr
        .time_stamp_token
        .ok_or_else(|| Error::Parse("missing token".into()))?;
    let tst_der = tst.to_der().map_err(|e| Error::Parse(e.to_string()))?;
    let sd = cms::content_info::ContentInfo::from_der(&tst_der)
        .map_err(|e| Error::Parse(format!("cms: {e}")))?;
    let (tst_info_der, signer_spki, serial_hex, _signer_cert, _chain) =
        extract_tstinfo_and_signer_spki(&sd).map_err(|e| Error::Parse(e))?;
    let tsti = x509_tsp::TstInfo::from_der(&tst_info_der).map_err(|e| Error::Parse(e.to_string()))?;
    let gen_time_unix = tsti.gen_time.to_unix_duration().as_secs() as i64;
    let tsa_kid = crate::crypto::kid_from_spki_der(&signer_spki);
    Ok(TsaResponse {
        der: der.to_vec(),
        gen_time_unix,
        serial_hex,
        tsa_kid,
    })
}

fn extract_tstinfo_and_signer_spki(
    ci: &cms::content_info::ContentInfo,
) -> Result<(Vec<u8>, Vec<u8>, String, x509_cert::Certificate, Vec<x509_cert::Certificate>), String> {
    use cms::cert::CertificateChoices;
    use cms::signed_data::{EncapsulatedContentInfo, SignedData};

    // Parse SignedData from ContentInfo content
    let signed: SignedData = SignedData::from_der(&ci.content.to_der().map_err(|e| e.to_string())?)
        .map_err(|e| format!("signed_data: {e}"))?;
    let EncapsulatedContentInfo { econtent, .. } = signed.encap_content_info;
    let tsti_der_any = econtent.ok_or_else(|| "missing econtent".to_string())?;

    // Derive SPKI DER from the first embedded certificate (best-effort)
    let mut serial_hex = String::new();
    let mut all = Vec::<x509_cert::Certificate>::new();
    if let Some(certs) = &signed.certificates {
        for i in 0..certs.0.len() {
            let ch = certs.0.get(i).ok_or_else(|| "bad certset".to_string())?;
            if let CertificateChoices::Certificate(cert) = ch {
                serial_hex = hex::encode(cert.tbs_certificate.serial_number.as_bytes());
                all.push(cert.clone());
            }
        }
    }
    if all.is_empty() {
        return Err("no certificates present".into());
    }
    let signer_cert = all[0].clone();
    let signer_spki = signer_cert
        .tbs_certificate
        .subject_public_key_info
        .to_der()
        .map_err(|e| e.to_string())?;
    Ok((tsti_der_any.value().to_vec(), signer_spki, serial_hex, signer_cert, all))
}

fn verify_message_imprint(
    tsti: &x509_tsp::TstInfo,
    expected_alg: &str,
    expected_imprint: &[u8],
) -> Result<(), Error> {
    let oid = tsti.message_imprint.hash_algorithm.oid;
    let ok = match expected_alg {
        "sha512" => oid == const_oid::db::rfc5912::ID_SHA_512,
        "shake256-64" => oid == const_oid::ObjectIdentifier::new_unwrap("2.16.840.1.101.3.4.2.12"),
        other => return Err(Error::Digest(other.into())),
    };
    if !ok {
        return Err(Error::Verify("hash alg mismatch".into()));
    }
    let got = tsti.message_imprint.hashed_message.as_bytes();
    if got != expected_imprint {
        return Err(Error::Verify("messageImprint mismatch".into()));
    }
    Ok(())
}

// (Removed unused verify_chain_and_eku to minimize dead code.)

fn verify_cms_signed_attrs(
    ci: &cms::content_info::ContentInfo,
    _signer_cert_der: &[u8],
    spki_der: &[u8],
) -> Result<(), Error> {
    // Parse SignedData from ContentInfo
    let signed_data: cms::signed_data::SignedData = cms::signed_data::SignedData::from_der(
        &ci.content
            .to_der()
            .map_err(|e| Error::Parse(format!("content der: {e}")))?,
    )
    .map_err(|e| Error::Parse(format!("signed_data: {e}")))?;
    let si = signed_data
        .signer_infos
        .0
        .get(0)
        .ok_or_else(|| Error::Parse("no SignerInfo".into()))?;
    let attrs = si
        .signed_attrs
        .as_ref()
        .ok_or_else(|| Error::Parse("missing signedAttrs".into()))?;
    let attrs_der = attrs
        .to_der()
        .map_err(|e| Error::Parse(format!("attrs der: {e}")))?;
    let sig = si.signature.as_bytes();

    // Map algorithms
    let sig_oid = si.signature_algorithm.oid;
    let dig_oid = si.digest_alg.oid;
    use pkcs8::spki::SubjectPublicKeyInfoRef;


    use ecdsa::signature::Verifier as _;
    let spki = SubjectPublicKeyInfoRef::try_from(spki_der).map_err(|e| Error::Parse(e.to_string()))?;
    let spki_alg = spki.algorithm.oid;
    let spki_key_bytes = spki.subject_public_key.raw_bytes();

    match (spki_alg, sig_oid, dig_oid) {
        // ECDSA P-256 / SHA-256
        (o, s, d)
            if o == const_oid::db::rfc5912::ID_EC_PUBLIC_KEY
                && s == const_oid::db::rfc5912::ECDSA_WITH_SHA_256
                && d == const_oid::db::rfc5912::ID_SHA_256 =>
        {
            let vk = p256::ecdsa::VerifyingKey::from_sec1_bytes(spki_key_bytes)
                .map_err(|e| Error::Verify(format!("p256 sec1: {e}")))?;
            let sig = p256::ecdsa::Signature::from_der(sig).map_err(|e| Error::Verify(format!("p256 sig: {e}")))?;
            vk.verify(&attrs_der, &sig).map_err(|_| Error::Verify("ecdsa p256 sha256".into()))
        }
        // ECDSA P-384 / SHA-384
        (o, s, d)
            if o == const_oid::db::rfc5912::ID_EC_PUBLIC_KEY
                && s == const_oid::db::rfc5912::ECDSA_WITH_SHA_384
                && d == const_oid::db::rfc5912::ID_SHA_384 =>
        {
            let vk = p384::ecdsa::VerifyingKey::from_sec1_bytes(spki_key_bytes)
                .map_err(|e| Error::Verify(format!("p384 sec1: {e}")))?;
            let sig = p384::ecdsa::Signature::from_der(sig).map_err(|e| Error::Verify(format!("p384 sig: {e}")))?;
            vk.verify(&attrs_der, &sig).map_err(|_| Error::Verify("ecdsa p384 sha384".into()))
        }
        // RSA PKCS#1 v1.5 / SHA-512
        // RSA-PSS with indicated digest
        (o, s, d)
            if o == const_oid::db::rfc5912::RSA_ENCRYPTION
                && s == const_oid::db::rfc5912::ID_RSASSA_PSS =>
        {
            use rsa::pss::{Signature as RsaPssSignature, VerifyingKey};
            use pkcs8::DecodePublicKey;
            let pk = rsa::RsaPublicKey::from_public_key_der(spki_der)
                .map_err(|e| Error::Verify(format!("rsa spki: {e}")))?;
            let rsig = RsaPssSignature::try_from(sig).map_err(|_| Error::Verify("rsa-pss sig parse".into()))?;
            let ok = if d == const_oid::db::rfc5912::ID_SHA_512 {
                VerifyingKey::<sha2::Sha512>::new_with_salt_len(pk.clone(), sha2::Sha512::output_size())
                    .verify(&attrs_der, &rsig)
                    .is_ok()
            } else if d == const_oid::db::rfc5912::ID_SHA_384 {
                VerifyingKey::<sha2::Sha384>::new_with_salt_len(pk.clone(), sha2::Sha384::output_size())
                    .verify(&attrs_der, &rsig)
                    .is_ok()
            } else if d == const_oid::db::rfc5912::ID_SHA_256 {
                VerifyingKey::<sha2::Sha256>::new_with_salt_len(pk.clone(), sha2::Sha256::output_size())
                    .verify(&attrs_der, &rsig)
                    .is_ok()
            } else {
                // Fallback to common set
                VerifyingKey::<sha2::Sha512>::new_with_salt_len(pk.clone(), sha2::Sha512::output_size())
                    .verify(&attrs_der, &rsig)
                    .is_ok()
                    || VerifyingKey::<sha2::Sha384>::new_with_salt_len(pk.clone(), sha2::Sha384::output_size())
                        .verify(&attrs_der, &rsig)
                        .is_ok()
                    || VerifyingKey::<sha2::Sha256>::new_with_salt_len(pk.clone(), sha2::Sha256::output_size())
                        .verify(&attrs_der, &rsig)
                        .is_ok()
            };
            if ok { Ok(()) } else { Err(Error::Verify("rsa-pss verify failed".into())) }
        }
        (o, s, d) if o == const_oid::db::rfc5912::RSA_ENCRYPTION && s == const_oid::db::rfc5912::RSA_ENCRYPTION => {
            // Some TSAs publish RSA signatures with digest OIDs that can vary by profile; try indicated digest first,
            // then fall back to the common set {SHA-512, SHA-384, SHA-256} to accommodate chain differences.
            use rsa::pkcs1v15::{Signature as RsaSignature, VerifyingKey};
            use pkcs8::DecodePublicKey;
            let pk = rsa::RsaPublicKey::from_public_key_der(spki_der)
                .map_err(|e| Error::Verify(format!("rsa spki: {e}")))?;
            let rsig = RsaSignature::try_from(sig).map_err(|_| Error::Verify("rsa sig parse".into()))?;

            // inner helper to try a digest
            fn try_rsa<D>(pk: &rsa::RsaPublicKey, msg: &[u8], sig: &RsaSignature) -> bool
            where
                D: sha2::digest::Digest + const_oid::AssociatedOid,
            {
                let vk = VerifyingKey::<D>::new_unprefixed(pk.clone());
                vk.verify(msg, sig).is_ok()
            }

            let ok = if d == const_oid::db::rfc5912::ID_SHA_512 {
                try_rsa::<sha2::Sha512>(&pk, &attrs_der, &rsig)
            } else if d == const_oid::db::rfc5912::ID_SHA_384 {
                try_rsa::<sha2::Sha384>(&pk, &attrs_der, &rsig)
            } else if d == const_oid::db::rfc5912::ID_SHA_256 {
                try_rsa::<sha2::Sha256>(&pk, &attrs_der, &rsig)
            } else {
                // Unknown digest OID: attempt the common set in order
                try_rsa::<sha2::Sha512>(&pk, &attrs_der, &rsig)
                    || try_rsa::<sha2::Sha384>(&pk, &attrs_der, &rsig)
                    || try_rsa::<sha2::Sha256>(&pk, &attrs_der, &rsig)
            };
            if ok { Ok(()) } else { Err(Error::Verify("rsa pkcs1 verify failed".into())) }
        }
        // RSA PKCS#1 v1.5 / SHA-384
        // These RSA cases are covered by the generic RSA handler above
        _ => Err(Error::Verify("unsupported CMS algorithm".into())),
    }
}

fn verify_eku_and_trust(
    signer: &x509_cert::Certificate,
    chain: &[x509_cert::Certificate],
    trust: &[Vec<u8>],
) -> Result<(), Error> {
    use const_oid::db::rfc5280::ID_KP_TIME_STAMPING;
    use x509_cert::ext::pkix::ExtendedKeyUsage;
    use const_oid::AssociatedOid as _;

    // Check EKU for id-kp-timeStamping
    let mut has_eku = false;
    if let Some(exts) = signer.tbs_certificate.extensions.as_ref() {
        for ext in exts {
            if ext.extn_id == ExtendedKeyUsage::OID {
                let eku = ExtendedKeyUsage::from_der(ext.extn_value.as_bytes())
                    .map_err(|e| Error::Parse(format!("eku: {e}")))?;
                if eku.0.iter().any(|oid| *oid == ID_KP_TIME_STAMPING) {
                    has_eku = true;
                    break;
                }
            }
        }
    }
    // Some TSA chains put EKU on the issuing CA. Accept if any embedded chain cert has the EKU.
    if !has_eku {
        for c in chain {
            if let Some(exts) = c.tbs_certificate.extensions.as_ref() {
                for ext in exts {
                    if ext.extn_id == ExtendedKeyUsage::OID {
                        let eku = ExtendedKeyUsage::from_der(ext.extn_value.as_bytes())
                            .map_err(|e| Error::Parse(format!("eku: {e}")))?;
                        if eku.0.iter().any(|oid| *oid == ID_KP_TIME_STAMPING) {
                            has_eku = true;
                            break;
                        }
                    }
                }
            }
            if has_eku { break; }
        }
    }
    if !has_eku {
        return Err(Error::Verify("timeStamping EKU not found on signer or issuing CA".into()));
    }

    // Bind to trust: accept if signer SPKI KID or any cert in chain matches any trust anchor SPKI KID
    let mut trusted_kids = std::collections::BTreeSet::new();
    let mut trust_certs: Vec<x509_cert::Certificate> = Vec::new();
    for blob in trust {
        // try parse as X.509 cert, else assume SPKI DER
        let kid = if let Ok(cert) = x509_cert::Certificate::from_der(blob) {
            let spki = cert
                .tbs_certificate
                .subject_public_key_info
                .to_der()
                .map_err(|e| Error::Parse(format!("spki: {e}")))?;
            crate::crypto::kid_from_spki_der(&spki)
        } else {
            crate::crypto::kid_from_spki_der(blob)
        };
        trusted_kids.insert(kid);
        if let Ok(cert) = x509_cert::Certificate::from_der(blob) {
            trust_certs.push(cert);
        }
    }
    let signer_spki = signer
        .tbs_certificate
        .subject_public_key_info
        .to_der()
        .map_err(|e| Error::Parse(format!("spki: {e}")))?;
    let signer_kid = crate::crypto::kid_from_spki_der(&signer_spki);
    if trusted_kids.contains(&signer_kid) {
        return Ok(());
    }
    for c in chain {
        let spki = c
            .tbs_certificate
            .subject_public_key_info
            .to_der()
            .map_err(|e| Error::Parse(format!("spki: {e}")))?;
        let kid = crate::crypto::kid_from_spki_der(&spki);
        if trusted_kids.contains(&kid) {
            return Ok(());
        }
    }
    // Try verifying the TSA signer certificate signature against any trusted certificate (ECDSA only)
    if let Some(()) = verify_signer_cert_with_trust(&signer, &trust_certs).ok() {
        return Ok(());
    }
    Err(Error::Verify("TSA chain not anchored in provided trust".into()))
}

fn verify_signer_cert_with_trust(
    signer: &x509_cert::Certificate,
    trust_certs: &[x509_cert::Certificate],
) -> Result<(), Error> {
    use const_oid::db::rfc5912 as oids;
    // Determine signature alg on subject cert
    let sig_oid = signer.signature_algorithm.oid;
    let tbs_der = signer
        .tbs_certificate
        .to_der()
        .map_err(|e| Error::Parse(format!("tbs der: {e}")))?;

    for issuer in trust_certs {
        let spki = &issuer.tbs_certificate.subject_public_key_info;
        // Only ECDSA issuers supported here
        if spki.algorithm.oid != oids::ID_EC_PUBLIC_KEY {
            continue;
        }
        let curve = spki
            .algorithm
            .owned_to_ref()
            .parameters_oid()
            .ok();
        let pk_bytes = spki
            .subject_public_key
            .raw_bytes()
            .to_vec();

        // ECDSA with SHA-256 (P-256)
        if sig_oid == oids::ECDSA_WITH_SHA_256 && curve == Some(oids::SECP_256_R_1) {
            use ecdsa::signature::DigestVerifier;
            let vk = p256::ecdsa::VerifyingKey::from_sec1_bytes(&pk_bytes)
                .map_err(|_| Error::Verify("invalid issuer P-256 key".into()))?;
            let sig_der = signer
                .signature
                .as_bytes()
                .ok_or_else(|| Error::Verify("missing signature bytes".into()))?;
            let sig = p256::ecdsa::Signature::from_der(sig_der)
                .map_err(|_| Error::Verify("invalid ECDSA P-256 signature".into()))?;
            let ok = vk
                .verify_digest(sha2::Sha256::new().chain_update(&tbs_der), &sig)
                .is_ok();
            if ok {
                return Ok(());
            }
        }
        // ECDSA with SHA-384 (P-384)
        if sig_oid == oids::ECDSA_WITH_SHA_384 && curve == Some(const_oid::db::rfc5912::SECP_384_R_1) {
            use ecdsa::signature::DigestVerifier;
            let vk = p384::ecdsa::VerifyingKey::from_sec1_bytes(&pk_bytes)
                .map_err(|_| Error::Verify("invalid issuer P-384 key".into()))?;
            let sig_der = signer
                .signature
                .as_bytes()
                .ok_or_else(|| Error::Verify("missing signature bytes".into()))?;
            let sig = p384::ecdsa::Signature::from_der(sig_der)
                .map_err(|_| Error::Verify("invalid ECDSA P-384 signature".into()))?;
            let ok = vk
                .verify_digest(sha2::Sha384::new().chain_update(&tbs_der), &sig)
                .is_ok();
            if ok {
                return Ok(());
            }
        }
    }
    Err(Error::Verify("could not validate signer cert against trust (ECDSA)".into()))
}