matter-commissioning 0.1.0

//! Certification Declaration verifier implementation.
//!
//! The verifier performs five checks in order:
//!
//! 1. CMS `SignedData` DER parse via the `cms` crate.
//! 2. Structural validation: a single `SignerInfo`, attached
//!    encapsulated content.
//! 3. ECDSA-P256 / SHA-256 signature verification against each
//!    trusted root's public key; accept on first match.
//! 4. Decode the inner CD TLV via `parse_inner_cd_tlv` (M6.4.3 T30
//!    fills the helper).
//! 5. Cross-check declared VID + PID against the expected pair
//!    supplied by the caller (typically sourced from the verified DAC
//!    subject).
//!
//! The trust store ([`CdSigningRoots`]) holds SEC1-uncompressed P-256
//! public keys for each trusted CSA signing root. Production callers
//! build the store via [`CdSigningRoots::from_pem`]; tests and
//! examples use the bundled CSA-test root via
//! [`CdSigningRoots::with_csa_test_roots`].

#![forbid(unsafe_code)]

use crate::attestation::{AttestationError, ProductId, VendorId};

/// Bundled PEM-encoded `SubjectPublicKeyInfo` for the synthetic
/// CSA-test CD signing root generated by `xtask capture-cd`. The
/// matching private key lives in `test-vectors/commissioning/cd/` and
/// signs the fixture CDs the verifier tests consume.
const CSA_TEST_CD_SIGNING_ROOT_PEM: &[u8] =
    include_bytes!("./csa_cd_signing_roots/csa-test-cd-signing-root.pem");

/// Trusted CSA Certification Declaration signing roots.
///
/// Built from production roots via [`Self::from_cert_der`] (X.509 CD
/// signing certificates, as published by the CSA DCL) or
/// [`Self::from_pem`] (bare `SubjectPublicKeyInfo` PEMs), or seeded with
/// the bundled synthetic CSA-test root via
/// [`Self::with_csa_test_roots`].
///
/// Internally stores each trusted root as a SEC1-uncompressed P-256
/// public key (65 bytes: `0x04 || X || Y`) so signature verification
/// can call `ring::signature::UnparsedPublicKey` directly without
/// re-parsing.
#[derive(Debug, Clone)]
pub struct CdSigningRoots {
    /// SEC1-uncompressed P-256 public keys (65 bytes each) for each
    /// trusted root.
    public_keys: Vec<Vec<u8>>,
}

impl CdSigningRoots {
    /// Build a trust store seeded with the bundled synthetic CSA-test
    /// CD signing root.
    ///
    /// **Tests and examples only — do not use in production.** Real
    /// commissioners supply CSA-published roots via
    /// [`Self::from_pem`].
    ///
    /// The bundled PEM is a compile-time constant, so parsing it should
    /// never fail at runtime; if it ever does (e.g. someone replaces
    /// the file with garbage), the store is returned empty rather than
    /// panicking, and the verifier will reject every signature with
    /// [`AttestationError::CertificationDeclarationSignatureInvalid`].
    #[must_use]
    pub fn with_csa_test_roots() -> Self {
        let pk = parse_pem_public_key(CSA_TEST_CD_SIGNING_ROOT_PEM).ok();
        Self {
            public_keys: pk.into_iter().collect(),
        }
    }

    /// Build a trust store from PEM-encoded P-256
    /// `SubjectPublicKeyInfo` blobs (one per trusted CSA signing
    /// root).
    ///
    /// # Errors
    ///
    /// Returns [`AttestationError::CertificationDeclarationMalformed`]
    /// if any input fails to parse. An empty slice returns an empty
    /// trust store.
    pub fn from_pem(pems: &[&[u8]]) -> Result<Self, AttestationError> {
        let mut public_keys = Vec::with_capacity(pems.len());
        for raw in pems {
            let pk = parse_pem_public_key(raw)?;
            public_keys.push(pk);
        }
        Ok(Self { public_keys })
    }

    /// Build a trust store from X.509 **certificate** DER blobs (one per
    /// trusted CSA CD signing root), extracting each certificate's P-256
    /// subject public key.
    ///
    /// This is the ingestion path for real-world CD signing roots: the CSA
    /// Distributed Compliance Ledger — and the `connectedhomeip`
    /// `credentials/production/cd-certs/` mirror of it — publish the roots as
    /// X.509 certificates, not as the bare `SubjectPublicKeyInfo` PEMs that
    /// [`Self::from_pem`] consumes. There are several distinct CSA CD signing
    /// keys, so a real commissioner typically loads the whole directory.
    ///
    /// The certificate is treated purely as a trust anchor: only its subject
    /// public key is extracted. No signature, validity-window, or chain checks
    /// are performed — the operator vouches for the roots by supplying them
    /// (exactly as [`Self::from_pem`] trusts the keys it is given).
    ///
    /// # Errors
    ///
    /// Returns [`AttestationError::CertificationDeclarationMalformed`] if any
    /// input fails to parse as an X.509 certificate, or does not carry a
    /// 65-byte SEC1-uncompressed P-256 public key.
    pub fn from_cert_der(certs: &[&[u8]]) -> Result<Self, AttestationError> {
        use x509_parser::prelude::{FromDer, X509Certificate};

        let mut public_keys = Vec::with_capacity(certs.len());
        for der in certs {
            let (_, cert) = X509Certificate::from_der(der)
                .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
            let pk = cert.public_key().subject_public_key.data.as_ref().to_vec();
            // CD signatures are ECDSA-P256; the trust root must carry a
            // SEC1-uncompressed P-256 point (`0x04` || X || Y, 65 bytes).
            if pk.len() != 65 || pk[0] != 0x04 {
                return Err(AttestationError::CertificationDeclarationMalformed);
            }
            public_keys.push(pk);
        }
        Ok(Self { public_keys })
    }

    /// Number of trusted roots in the store.
    #[must_use]
    pub fn len(&self) -> usize {
        self.public_keys.len()
    }

    /// Returns `true` if no trusted roots have been loaded.
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.public_keys.is_empty()
    }

    /// Internal accessor — borrow the raw 65-byte SEC1 uncompressed
    /// public-key bytes for each trusted root, for the verifier's
    /// signature-check loop.
    fn keys(&self) -> &[Vec<u8>] {
        &self.public_keys
    }
}

/// Verify a Certification Declaration extracted from
/// `attestation_elements` (Matter Core Spec §6.3.1) against a trust
/// store and an expected VID / PID pair.
///
/// Performs five checks in order:
///
/// 1. CMS `SignedData` DER parse via the `cms` crate.
/// 2. Structural validation: a single `SignerInfo`, attached
///    encapsulated content.
/// 3. ECDSA-P256 / SHA-256 signature verification against each
///    trusted root in `trust`; accept on first match.
/// 4. Decode the inner CD TLV.
/// 5. Cross-check declared VID + PID against `expected_vid` /
///    `expected_pid` (sourced from the verified DAC chain by the
///    caller). Per Matter Core Spec §6.2.3, when the CD carries both
///    `dac_origin_vendor_id` (tag 9) and `dac_origin_product_id`
///    (tag 10), those override fields are compared instead of the CD's
///    own `vendor_id` / `product_id_array`.
///
/// # Errors
///
/// - [`AttestationError::CertificationDeclarationMalformed`] — the
///   CMS DER failed to parse or did not match the expected shape.
/// - [`AttestationError::CertificationDeclarationSignatureInvalid`] —
///   no trusted root accepts the signature.
/// - [`AttestationError::CertificationDeclarationTlvMalformed`] —
///   inner CD TLV missing required fields or malformed.
/// - [`AttestationError::CertificationDeclarationVidMismatch`] —
///   declared VID does not equal `expected_vid`.
/// - [`AttestationError::CertificationDeclarationPidMismatch`] —
///   declared PID list does not contain `expected_pid`.
#[allow(
    clippy::similar_names,
    reason = "the `expected_vid`/`expected_pid` pair mirrors the public-API \
     vocabulary used elsewhere in this crate (VendorId/ProductId); \
     renaming would obscure intent at the call site."
)]
pub fn verify_certification_declaration(
    cd_bytes: &[u8],
    expected_vid: VendorId,
    expected_pid: ProductId,
    trust: &CdSigningRoots,
) -> Result<(), AttestationError> {
    use cms::content_info::ContentInfo;
    use cms::signed_data::SignedData;
    use der::asn1::OctetString;
    use der::{Decode, DecodeValue, Encode, Header, SliceReader, Tag as DerTag};

    // 1. Parse the outer ContentInfo.
    let content_info = ContentInfo::from_der(cd_bytes)
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
    // ContentInfo.content is an Any wrapping SignedData; re-encode and
    // decode to convert.
    let signed_data_der = content_info
        .content
        .to_der()
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
    let signed_data = SignedData::from_der(&signed_data_der)
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;

    // 2. Validate shape: exactly one SignerInfo and attached content.
    if signed_data.signer_infos.0.len() != 1 {
        return Err(AttestationError::CertificationDeclarationMalformed);
    }
    let signer = signed_data
        .signer_infos
        .0
        .iter()
        .next()
        .ok_or(AttestationError::CertificationDeclarationMalformed)?;

    // 3. Extract the signed content (the inner CD TLV bytes).
    //
    // `EncapsulatedContentInfo.econtent` is typed `Option<Any>` where
    // the Any wraps an OCTET STRING. We decode the OCTET STRING from
    // the Any's body and copy its bytes — this is the eContent value
    // (the inner CD TLV) the signer signed.
    let econtent = signed_data
        .encap_content_info
        .econtent
        .as_ref()
        .ok_or(AttestationError::CertificationDeclarationMalformed)?;
    // `Any` does not expose its raw value bytes directly; re-encode it
    // then peel off the OCTET STRING tag+length to read the inner
    // bytes via `OctetString::decode_value`.
    let econtent_der = econtent
        .to_der()
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
    let mut reader = SliceReader::new(&econtent_der)
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
    let header = Header::decode(&mut reader)
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
    if header.tag != DerTag::OctetString {
        return Err(AttestationError::CertificationDeclarationMalformed);
    }
    let octet_string = OctetString::decode_value(&mut reader, header)
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;
    let content_bytes = octet_string.as_bytes().to_vec();

    // 4. Extract the signature bytes.
    let sig = signer.signature.as_bytes();

    // 5. Verify ECDSA-P256 / SHA-256 against each trusted root.
    let mut accepted = false;
    for key in trust.keys() {
        if verify_ecdsa_p256_sha256(key, &content_bytes, sig).is_ok() {
            accepted = true;
            break;
        }
    }
    if !accepted {
        return Err(AttestationError::CertificationDeclarationSignatureInvalid);
    }

    // 6. Decode the inner CD TLV and cross-check VID / PID.
    //
    // Matter Core Spec §6.2.3: when the CD carries the optional
    // `dac_origin_vendor_id` (tag 9) AND `dac_origin_product_id`
    // (tag 10), the commissioner MUST validate the DAC/PAI subject
    // VID/PID against THOSE origin fields, not the CD's own
    // `vendor_id` / `product_id_array`. This supports CDs issued for a
    // PAA/PAI scoped to a different vendor than the device's own VID
    // (e.g. white-label / contract-manufactured products).
    //
    // Decision on partial presence: the spec treats `dac_origin_*` as a
    // both-or-neither pair. We trigger the override only when BOTH are
    // present; if exactly one is present we ignore the override and fall
    // back to the standard fields (the safe, conservative reading — a
    // half-specified override is not a valid §6.2.3 override).
    let parsed = parse_inner_cd_tlv(&content_bytes)?;
    if let (Some(origin_vid), Some(origin_pid)) =
        (parsed.dac_origin_vendor_id, parsed.dac_origin_product_id)
    {
        // Override path: bind the DAC against the dac_origin_* fields.
        if origin_vid != expected_vid {
            return Err(AttestationError::CertificationDeclarationVidMismatch {
                declared: origin_vid,
                expected: expected_vid,
            });
        }
        if origin_pid != expected_pid {
            return Err(AttestationError::CertificationDeclarationPidMismatch(
                expected_pid,
            ));
        }
    } else {
        // Standard path: bind against vendor_id / product_id_array.
        if parsed.vendor_id != expected_vid {
            return Err(AttestationError::CertificationDeclarationVidMismatch {
                declared: parsed.vendor_id,
                expected: expected_vid,
            });
        }
        if !parsed.product_ids.contains(&expected_pid) {
            return Err(AttestationError::CertificationDeclarationPidMismatch(
                expected_pid,
            ));
        }
    }

    Ok(())
}

/// Decoded view of the inner Certification Declaration TLV — the
/// subset the verifier cross-checks today. T30 fleshes out the parser.
#[derive(Debug)]
struct ParsedCd {
    /// Vendor ID (Matter Core Spec §6.3.1 tag 1).
    vendor_id: VendorId,
    /// Product ID list (tag 2 — at least one element required).
    product_ids: Vec<ProductId>,
    /// `dac_origin_vendor_id` (Matter Core Spec §6.3.1 tag 9, optional).
    ///
    /// When present (together with [`Self::dac_origin_product_id`]), the
    /// commissioner MUST validate the DAC/PAI subject VID against THIS
    /// value rather than [`Self::vendor_id`] (Matter Core Spec §6.2.3).
    dac_origin_vendor_id: Option<VendorId>,
    /// `dac_origin_product_id` (Matter Core Spec §6.3.1 tag 10, optional).
    ///
    /// The PID counterpart to [`Self::dac_origin_vendor_id`]; see its docs.
    dac_origin_product_id: Option<ProductId>,
}

/// Decode the inner CD TLV per Matter Core Spec §6.3.1: an anonymous
/// outer structure with context-tagged fields including tag 1
/// (`vendor_id`, u16), tag 2 (`product_id_array`, array of u16), and the
/// optional override fields tag 9 (`dac_origin_vendor_id`, u16) and tag
/// 10 (`dac_origin_product_id`, u16).
///
/// All other context-tagged fields (`format_version`, `device_type_id`,
/// `certificate_id`, `security_level`, `security_information`,
/// `version_number`, `certification_type`, `authorized_paa_list`) and
/// any future-extension fields are forward-compat ignored — the verifier
/// only needs VID + PID (and the optional `dac_origin_*` overrides) for
/// cross-checking against the DAC subject.
fn parse_inner_cd_tlv(tlv: &[u8]) -> Result<ParsedCd, AttestationError> {
    use matter_codec::{ContainerKind, Element, Tag, TlvReader, Value};

    let mut reader = TlvReader::new(tlv);
    match reader
        .next()
        .map_err(|_| AttestationError::CertificationDeclarationTlvMalformed)?
    {
        Some(Element::ContainerStart {
            tag: Tag::Anonymous,
            kind: ContainerKind::Structure,
        }) => {}
        _ => return Err(AttestationError::CertificationDeclarationTlvMalformed),
    }

    let mut vid: Option<VendorId> = None;
    let mut pids: Vec<ProductId> = Vec::new();
    let mut origin_vendor: Option<VendorId> = None;
    let mut origin_product: Option<ProductId> = None;

    loop {
        match reader
            .next()
            .map_err(|_| AttestationError::CertificationDeclarationTlvMalformed)?
        {
            None => return Err(AttestationError::CertificationDeclarationTlvMalformed),
            Some(Element::ContainerEnd) => break,
            Some(Element::Scalar {
                tag: Tag::Context(1),
                value: Value::Uint(v),
            }) => {
                if vid.is_some() {
                    return Err(AttestationError::CertificationDeclarationTlvMalformed);
                }
                let v16 = u16::try_from(v)
                    .map_err(|_| AttestationError::CertificationDeclarationTlvMalformed)?;
                vid = Some(VendorId::new(v16));
            }
            Some(Element::ContainerStart {
                tag: Tag::Context(2),
                kind: ContainerKind::Array,
            }) => {
                if !pids.is_empty() {
                    return Err(AttestationError::CertificationDeclarationTlvMalformed);
                }
                loop {
                    match reader
                        .next()
                        .map_err(|_| AttestationError::CertificationDeclarationTlvMalformed)?
                    {
                        None => return Err(AttestationError::CertificationDeclarationTlvMalformed),
                        Some(Element::ContainerEnd) => break,
                        Some(Element::Scalar {
                            tag: Tag::Anonymous,
                            value: Value::Uint(p),
                        }) => {
                            let p16 = u16::try_from(p).map_err(|_| {
                                AttestationError::CertificationDeclarationTlvMalformed
                            })?;
                            pids.push(ProductId::new(p16));
                        }
                        // Inside the array, unknown shapes are a structural error
                        // (the spec says product IDs are u16). But be lenient on
                        // tagged-not-anonymous in case future M6.x extensions land.
                        Some(_) => {}
                    }
                }
            }
            // dac_origin_vendor_id (tag 9) — optional override; see §6.2.3.
            Some(Element::Scalar {
                tag: Tag::Context(9),
                value: Value::Uint(v),
            }) => {
                if origin_vendor.is_some() {
                    return Err(AttestationError::CertificationDeclarationTlvMalformed);
                }
                let v16 = u16::try_from(v)
                    .map_err(|_| AttestationError::CertificationDeclarationTlvMalformed)?;
                origin_vendor = Some(VendorId::new(v16));
            }
            // dac_origin_product_id (tag 10) — optional override; see §6.2.3.
            Some(Element::Scalar {
                tag: Tag::Context(10),
                value: Value::Uint(p),
            }) => {
                if origin_product.is_some() {
                    return Err(AttestationError::CertificationDeclarationTlvMalformed);
                }
                let p16 = u16::try_from(p)
                    .map_err(|_| AttestationError::CertificationDeclarationTlvMalformed)?;
                origin_product = Some(ProductId::new(p16));
            }
            // Forward-compat: ignore other context-tagged scalars / containers.
            Some(_) => {}
        }
    }

    let vendor_id = vid.ok_or(AttestationError::CertificationDeclarationTlvMalformed)?;
    if pids.is_empty() {
        // product_id_array required to be non-empty per spec §6.3.1.
        return Err(AttestationError::CertificationDeclarationTlvMalformed);
    }
    Ok(ParsedCd {
        vendor_id,
        product_ids: pids,
        dac_origin_vendor_id: origin_vendor,
        dac_origin_product_id: origin_product,
    })
}

/// Parse a PEM-encoded `SubjectPublicKeyInfo` for a P-256 public key
/// and return the SEC1 uncompressed point (65 bytes:
/// `0x04 || X || Y`) suitable for `ring`'s
/// `UnparsedPublicKey<ECDSA_P256_SHA256_FIXED>`.
///
/// Strips the `-----BEGIN PUBLIC KEY-----` / `-----END PUBLIC KEY-----`
/// armor, base64-decodes the body, and slices the trailing 65 bytes of
/// the DER (the SEC1 uncompressed point inside the SPKI's `BIT
/// STRING`). The point's `0x04` marker byte is checked here; ring's
/// `UnparsedPublicKey` rejects any malformed point at signature-verify
/// time as a second line of defense.
fn parse_pem_public_key(pem: &[u8]) -> Result<Vec<u8>, AttestationError> {
    use base64::Engine;

    const HEADER: &str = "-----BEGIN PUBLIC KEY-----";
    const FOOTER: &str = "-----END PUBLIC KEY-----";

    let pem_str = std::str::from_utf8(pem)
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;

    let header_start = pem_str
        .find(HEADER)
        .ok_or(AttestationError::CertificationDeclarationMalformed)?;
    let body_start = header_start + HEADER.len();
    let footer_start = pem_str
        .find(FOOTER)
        .ok_or(AttestationError::CertificationDeclarationMalformed)?;
    if footer_start <= body_start {
        return Err(AttestationError::CertificationDeclarationMalformed);
    }

    // Strip all whitespace from the base64 body.
    let body: String = pem_str[body_start..footer_start]
        .chars()
        .filter(|c| !c.is_whitespace())
        .collect();

    let der = base64::engine::general_purpose::STANDARD
        .decode(body.as_bytes())
        .map_err(|_| AttestationError::CertificationDeclarationMalformed)?;

    // Extract the SEC1 uncompressed point from the SubjectPublicKeyInfo.
    // The structure for a P-256 SPKI is exactly 91 bytes:
    //   30 59                        SEQUENCE (89)
    //   30 13                          SEQUENCE (19)
    //     06 07 2A 86 48 CE 3D 02 01   OID ecPublicKey
    //     06 08 2A 86 48 CE 3D 03 01 07 OID prime256v1
    //   03 42 00                       BIT STRING (66 bytes, 0 unused bits)
    //   04 XX...XX                     SEC1 uncompressed point (65 bytes)
    //                                  starting with 0x04
    //
    // The SEC1 point is the last 65 bytes. We validate the marker byte
    // and let `ring::UnparsedPublicKey::new` reject malformed bytes
    // later if the prefix is corrupt.
    if der.len() < 65 {
        return Err(AttestationError::CertificationDeclarationMalformed);
    }
    let point = &der[der.len() - 65..];
    if point[0] != 0x04 {
        return Err(AttestationError::CertificationDeclarationMalformed);
    }
    Ok(point.to_vec())
}

/// Verify an ECDSA-P256 / SHA-256 signature against a SEC1-uncompressed
/// P-256 public key.
///
/// CMS `SignerInfo.signature` carries ECDSA signatures as a DER
/// `ECDSA-Sig-Value` (SEQUENCE of r, s) — confirmed against a real
/// CSA-signed CD (Tapo P110M, M6.6.5 validation), and matching chip's
/// `CMS_Sign`. A raw fixed-form (r||s, exactly 64 bytes) signature is
/// also accepted for compatibility with the historical local test
/// fixtures generated by `xtask capture-cd`.
///
/// Maps any verification failure to
/// [`AttestationError::CertificationDeclarationSignatureInvalid`] —
/// the caller (the per-root loop in
/// [`verify_certification_declaration`]) only cares whether *some*
/// trusted root accepted the signature, not which one rejected it.
fn verify_ecdsa_p256_sha256(
    public_key: &[u8],
    msg: &[u8],
    sig: &[u8],
) -> Result<(), AttestationError> {
    use ring::signature::{UnparsedPublicKey, ECDSA_P256_SHA256_ASN1, ECDSA_P256_SHA256_FIXED};
    let asn1 = UnparsedPublicKey::new(&ECDSA_P256_SHA256_ASN1, public_key);
    if asn1.verify(msg, sig).is_ok() {
        return Ok(());
    }
    if sig.len() == 64 {
        let fixed = UnparsedPublicKey::new(&ECDSA_P256_SHA256_FIXED, public_key);
        if fixed.verify(msg, sig).is_ok() {
            return Ok(());
        }
    }
    Err(AttestationError::CertificationDeclarationSignatureInvalid)
}

#[cfg(test)]
mod tests {
    // The CD test helpers pair `dac_origin_vid`/`dac_origin_pid` and
    // `origin_vid`/`origin_pid` (and VendorId/ProductId locals) by design —
    // the near-identical names mirror the spec field pairs. Same carve-out
    // as `tests/support/mod.rs`.
    #![allow(clippy::similar_names)]

    use super::*;

    #[test]
    #[allow(clippy::unwrap_used, clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn verify_accepts_der_encoded_ecdsa_signature() {
        // CMS `SignerInfo.signature` carries ECDSA signatures as a DER
        // `ECDSA-Sig-Value` (SEQUENCE of r, s) — confirmed on a real
        // CSA-signed CD (Tapo P110M, M6.6.5 validation: 70-byte `0x30 44 …`).
        // chip's `CMS_Sign` emits the same (`ConvertECDSASignatureRawToDER`).
        use ring::rand::SystemRandom;
        use ring::signature::{EcdsaKeyPair, KeyPair, ECDSA_P256_SHA256_ASN1_SIGNING};

        let rng = SystemRandom::new();
        let pkcs8 = EcdsaKeyPair::generate_pkcs8(&ECDSA_P256_SHA256_ASN1_SIGNING, &rng).unwrap();
        let kp = EcdsaKeyPair::from_pkcs8(&ECDSA_P256_SHA256_ASN1_SIGNING, pkcs8.as_ref(), &rng)
            .unwrap();
        let msg = b"certification declaration content";
        let sig = kp.sign(&rng, msg).unwrap(); // DER-encoded ECDSA-Sig-Value
        let pk = kp.public_key().as_ref();

        verify_ecdsa_p256_sha256(pk, msg, sig.as_ref())
            .expect("DER-encoded CMS signature must verify");
    }

    #[test]
    fn with_csa_test_roots_loads_bundled_root() {
        let trust = CdSigningRoots::with_csa_test_roots();
        assert_eq!(trust.len(), 1);
        assert!(!trust.is_empty());
    }

    #[test]
    #[allow(clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn parse_pem_public_key_extracts_65_byte_sec1_point() {
        const PEM: &[u8] = include_bytes!("./csa_cd_signing_roots/csa-test-cd-signing-root.pem");
        let key = parse_pem_public_key(PEM).expect("happy path parses");
        assert_eq!(key.len(), 65, "SEC1 uncompressed P-256 point");
        assert_eq!(key[0], 0x04, "uncompressed-point marker byte");
    }

    #[test]
    #[allow(clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn parse_pem_public_key_rejects_garbage() {
        let err = parse_pem_public_key(b"not a PEM").expect_err("garbage rejected");
        assert!(matches!(
            err,
            AttestationError::CertificationDeclarationMalformed
        ));
    }

    #[test]
    #[allow(clippy::unwrap_used)] // Test-code carve-out: see CLAUDE.md.
    fn from_pem_empty_input_yields_empty_trust_store() {
        let trust = CdSigningRoots::from_pem(&[]).unwrap();
        assert!(trust.is_empty());
        assert_eq!(trust.len(), 0);
    }

    #[test]
    #[allow(clippy::unwrap_used, clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn from_cert_der_extracts_p256_pubkey_from_x509_cert() {
        // Real-world CD signing roots (CSA DCL / connectedhomeip
        // `credentials/production/cd-certs/`) are X.509 certificates, not bare
        // SubjectPublicKeyInfo PEMs. `from_cert_der` must extract the cert's
        // P-256 subject public key. We synthesise a self-signed P-256 cert with
        // a known key and assert the extracted SEC1 point matches it byte-for-byte.
        use matter_cert::test_support::{build_x509_der, TestCertFields};
        use matter_cert::{
            DistinguishedName, DnAttribute, Extensions, MatterTime, PublicKey, Signature,
        };
        use ring::rand::SystemRandom;
        use ring::signature::{EcdsaKeyPair, KeyPair, ECDSA_P256_SHA256_ASN1_SIGNING};

        let rng = SystemRandom::new();
        let pkcs8 = EcdsaKeyPair::generate_pkcs8(&ECDSA_P256_SHA256_ASN1_SIGNING, &rng).unwrap();
        let kp = EcdsaKeyPair::from_pkcs8(&ECDSA_P256_SHA256_ASN1_SIGNING, pkcs8.as_ref(), &rng)
            .unwrap();
        let expected = kp.public_key().as_ref().to_vec(); // 65-byte SEC1 uncompressed
        let pk = PublicKey::from_slice(&expected).unwrap();

        let dn = DistinguishedName::new(vec![DnAttribute::CommonName(
            "Test CD Signing Key (synthetic)".into(),
        )]);
        let der = build_x509_der(
            TestCertFields {
                serial: vec![0x01],
                issuer: dn.clone(),
                not_before: MatterTime::from_unix_secs(1_700_000_000),
                not_after: MatterTime::NO_EXPIRY,
                subject: dn,
                public_key: pk,
                extensions: Extensions::default(),
                signature: Signature::new([0u8; 64]),
            },
            pkcs8.as_ref(), // self-signed
        )
        .expect("synthetic CD signing cert builds");

        let trust = CdSigningRoots::from_cert_der(&[&der]).expect("cert parses");
        assert_eq!(trust.len(), 1);
        assert_eq!(
            trust.public_keys[0], expected,
            "extracted SEC1 public key must match the cert's subject key"
        );
    }

    #[test]
    #[allow(clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn from_cert_der_rejects_non_certificate_bytes() {
        let err = CdSigningRoots::from_cert_der(&[b"not a certificate"])
            .expect_err("garbage DER rejected");
        assert!(matches!(
            err,
            AttestationError::CertificationDeclarationMalformed
        ));
    }

    #[test]
    fn parse_inner_cd_tlv_extracts_vendor_id_and_pid_list() {
        // Test-code carve-out: see CLAUDE.md.
        #![allow(clippy::unwrap_used, clippy::expect_used)]
        use matter_codec::{Tag, TlvWriter};
        let mut buf = Vec::new();
        let mut w = TlvWriter::new(&mut buf);
        w.start_structure(Tag::Anonymous).unwrap();
        w.put_uint(Tag::Context(0), 1).unwrap(); // format_version
        w.put_uint(Tag::Context(1), 0xFFF1).unwrap(); // vendor_id
        w.start_array(Tag::Context(2)).unwrap();
        w.put_uint(Tag::Anonymous, 0x8001).unwrap();
        w.put_uint(Tag::Anonymous, 0x8002).unwrap();
        w.end_container().unwrap(); // close array
        w.end_container().unwrap(); // close struct

        let parsed = parse_inner_cd_tlv(&buf).expect("happy path decodes");
        assert_eq!(parsed.vendor_id, VendorId::new(0xFFF1));
        assert_eq!(
            parsed.product_ids,
            vec![ProductId::new(0x8001), ProductId::new(0x8002)]
        );
    }

    #[test]
    fn parse_inner_cd_tlv_ignores_forward_compat_fields() {
        // Test-code carve-out: see CLAUDE.md.
        #![allow(clippy::unwrap_used, clippy::expect_used)]
        use matter_codec::{Tag, TlvWriter};
        // Hand-roll a CD with tag 0 (format_version), tag 1 (vid), tag 2 (pids),
        // tag 3 (device_type_id), tag 4 (certificate_id utf8), tag 5..8 (security_*,
        // version_number, certification_type), AND a fake tag 99 (future field).
        let mut buf = Vec::new();
        let mut w = TlvWriter::new(&mut buf);
        w.start_structure(Tag::Anonymous).unwrap();
        w.put_uint(Tag::Context(0), 1).unwrap();
        w.put_uint(Tag::Context(1), 0xFFF1).unwrap();
        w.start_array(Tag::Context(2)).unwrap();
        w.put_uint(Tag::Anonymous, 0x8001).unwrap();
        w.end_container().unwrap();
        w.put_uint(Tag::Context(3), 0x0100).unwrap();
        w.put_utf8(Tag::Context(4), "CSA-ID").unwrap();
        w.put_uint(Tag::Context(5), 0).unwrap();
        w.put_uint(Tag::Context(6), 0).unwrap();
        w.put_uint(Tag::Context(7), 1).unwrap();
        w.put_uint(Tag::Context(8), 0).unwrap();
        w.put_uint(Tag::Context(99), 0xDEAD).unwrap(); // unknown future field
        w.end_container().unwrap();

        let parsed = parse_inner_cd_tlv(&buf).expect("forward-compat decode");
        assert_eq!(parsed.vendor_id, VendorId::new(0xFFF1));
        assert_eq!(parsed.product_ids, vec![ProductId::new(0x8001)]);
    }

    #[test]
    fn parse_inner_cd_tlv_rejects_missing_vid() {
        // Test-code carve-out: see CLAUDE.md.
        #![allow(clippy::unwrap_used, clippy::expect_used)]
        use matter_codec::{Tag, TlvWriter};
        let mut buf = Vec::new();
        let mut w = TlvWriter::new(&mut buf);
        w.start_structure(Tag::Anonymous).unwrap();
        // No tag 1 (vendor_id).
        w.start_array(Tag::Context(2)).unwrap();
        w.put_uint(Tag::Anonymous, 0x8001).unwrap();
        w.end_container().unwrap();
        w.end_container().unwrap();

        let err = parse_inner_cd_tlv(&buf).expect_err("missing vid rejected");
        assert!(matches!(
            err,
            AttestationError::CertificationDeclarationTlvMalformed
        ));
    }

    #[test]
    fn parse_inner_cd_tlv_rejects_garbage() {
        // Test-code carve-out: see CLAUDE.md.
        #![allow(clippy::unwrap_used, clippy::expect_used)]
        let err = parse_inner_cd_tlv(&[0xFF]).expect_err("garbage rejected");
        assert!(matches!(
            err,
            AttestationError::CertificationDeclarationTlvMalformed
        ));
    }

    #[test]
    fn parse_inner_cd_tlv_captures_dac_origin_fields() {
        // Test-code carve-out: see CLAUDE.md.
        #![allow(clippy::unwrap_used, clippy::expect_used)]
        let tlv = build_inner_cd_tlv(0xFFF1, 0x8001, Some(0x1234), Some(0x5678), &[0x8001]);
        let parsed = parse_inner_cd_tlv(&tlv).expect("decodes with dac_origin");
        assert_eq!(parsed.vendor_id, VendorId::new(0xFFF1));
        assert_eq!(parsed.product_ids, vec![ProductId::new(0x8001)]);
        assert_eq!(parsed.dac_origin_vendor_id, Some(VendorId::new(0x1234)));
        assert_eq!(parsed.dac_origin_product_id, Some(ProductId::new(0x5678)));
    }

    // ── Fix B — CD dac_origin override binding (Matter §6.2.3) ──────────────
    //
    // These tests sign a synthetic CD with the bundled CSA-test signing key
    // (which `CdSigningRoots::with_csa_test_roots()` trusts) and run it
    // through the public `verify_certification_declaration`, exercising the
    // dac_origin override path end-to-end:
    //
    //   - CD with dac_origin set + DAC matching the ORIGIN VID/PID (but NOT
    //     the CD's own vendor_id) → accepted.
    //   - CD with dac_origin set + DAC matching neither → rejected.
    //   - CD WITHOUT dac_origin → unchanged: compares vendor_id /
    //     product_id_array.

    /// PKCS#8 private key for the bundled CSA-test CD signing root. The
    /// matching public key is bundled in
    /// `csa_cd_signing_roots/csa-test-cd-signing-root.pem` and trusted by
    /// `CdSigningRoots::with_csa_test_roots()`.
    const CSA_TEST_CD_SIGNING_KEY_PKCS8: &[u8] = include_bytes!(
        "../../../../../test-vectors/commissioning/cd/csa-test-cd-signing-root.pkcs8.der"
    );

    /// Build the inner CD TLV per Matter Core Spec §6.3.1, optionally
    /// including the `dac_origin_*` override fields (tags 9 / 10).
    ///
    /// Mirrors `xtask/src/capture_cd.rs::build_inner_cd_tlv` but adds the
    /// optional tags 9/10 so the Fix B override path can be exercised.
    #[allow(clippy::unwrap_used)] // Test-code carve-out: see CLAUDE.md.
    fn build_inner_cd_tlv(
        vendor_id: u16,
        product_id: u16,
        dac_origin_vid: Option<u16>,
        dac_origin_pid: Option<u16>,
        product_id_array: &[u16],
    ) -> Vec<u8> {
        use matter_codec::{Tag, TlvWriter};
        let mut buf = Vec::new();
        {
            let mut w = TlvWriter::new(&mut buf);
            w.start_structure(Tag::Anonymous).unwrap();
            w.put_uint(Tag::Context(0), 1).unwrap(); // format_version
            w.put_uint(Tag::Context(1), u64::from(vendor_id)).unwrap(); // vendor_id
            w.start_array(Tag::Context(2)).unwrap(); // product_id_array
            let pids: Vec<u16> = if product_id_array.is_empty() {
                vec![product_id]
            } else {
                product_id_array.to_vec()
            };
            for p in pids {
                w.put_uint(Tag::Anonymous, u64::from(p)).unwrap();
            }
            w.end_container().unwrap();
            w.put_uint(Tag::Context(3), 0x0100).unwrap(); // device_type_id
            w.put_utf8(Tag::Context(4), "CSA00000000000000").unwrap(); // certificate_id
            w.put_uint(Tag::Context(5), 0).unwrap(); // security_level
            w.put_uint(Tag::Context(6), 0).unwrap(); // security_information
            w.put_uint(Tag::Context(7), 1).unwrap(); // version_number
            w.put_uint(Tag::Context(8), 0).unwrap(); // certification_type
            if let Some(v) = dac_origin_vid {
                w.put_uint(Tag::Context(9), u64::from(v)).unwrap();
            }
            if let Some(p) = dac_origin_pid {
                w.put_uint(Tag::Context(10), u64::from(p)).unwrap();
            }
            w.end_container().unwrap();
        }
        buf
    }

    /// Sign `content` (the inner CD TLV) into a CMS `SignedData`
    /// `ContentInfo` DER blob with the bundled CSA-test key, using the
    /// no-`signedAttrs` shape the verifier expects. Mirrors
    /// `xtask/src/capture_cd.rs::sign_into_cms`.
    #[allow(clippy::unwrap_used, clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn sign_into_cms(content: &[u8]) -> Vec<u8> {
        use cms::cert::IssuerAndSerialNumber;
        use cms::content_info::{CmsVersion, ContentInfo};
        use cms::signed_data::{
            EncapsulatedContentInfo, SignedData, SignerIdentifier, SignerInfo, SignerInfos,
        };
        use const_oid::ObjectIdentifier;
        use der::asn1::{Any, AnyRef, OctetString, SetOfVec};
        use der::{Encode, Tag as DerTag};
        use ring::rand::SystemRandom;
        use ring::signature::{EcdsaKeyPair, ECDSA_P256_SHA256_FIXED_SIGNING};
        use spki::AlgorithmIdentifierOwned;
        use x509_cert::name::RdnSequence;
        use x509_cert::serial_number::SerialNumber;

        const ID_DATA: ObjectIdentifier = ObjectIdentifier::new_unwrap("1.2.840.113549.1.7.1");
        const ID_SIGNED_DATA: ObjectIdentifier =
            ObjectIdentifier::new_unwrap("1.2.840.113549.1.7.2");
        const ID_SHA_256: ObjectIdentifier = ObjectIdentifier::new_unwrap("2.16.840.1.101.3.4.2.1");
        const ECDSA_WITH_SHA_256: ObjectIdentifier =
            ObjectIdentifier::new_unwrap("1.2.840.10045.4.3.2");

        let rng = SystemRandom::new();
        let key = EcdsaKeyPair::from_pkcs8(
            &ECDSA_P256_SHA256_FIXED_SIGNING,
            CSA_TEST_CD_SIGNING_KEY_PKCS8,
            &rng,
        )
        .expect("bundled CSA-test CD signing key loads");
        let signature = key.sign(&rng, content).expect("sign eContent");

        let econtent_any =
            Any::new(DerTag::OctetString, content.to_vec()).expect("Any(OctetString)");
        let encap = EncapsulatedContentInfo {
            econtent_type: ID_DATA,
            econtent: Some(econtent_any),
        };
        let sha256 = AlgorithmIdentifierOwned {
            oid: ID_SHA_256,
            parameters: None,
        };
        let digest_algorithms =
            SetOfVec::try_from(vec![sha256.clone()]).expect("digest_algorithms");
        let serial = SerialNumber::new(&[0x01]).expect("serial");
        let sid = SignerIdentifier::IssuerAndSerialNumber(IssuerAndSerialNumber {
            issuer: RdnSequence::default(),
            serial_number: serial,
        });
        let signature_octets =
            OctetString::new(signature.as_ref().to_vec()).expect("signature octets");
        let signer_info = SignerInfo {
            version: CmsVersion::V1,
            sid,
            digest_alg: sha256,
            signed_attrs: None,
            signature_algorithm: AlgorithmIdentifierOwned {
                oid: ECDSA_WITH_SHA_256,
                parameters: None,
            },
            signature: signature_octets,
            unsigned_attrs: None,
        };
        let signer_infos = SignerInfos(SetOfVec::try_from(vec![signer_info]).expect("signer set"));
        let signed_data = SignedData {
            version: CmsVersion::V1,
            digest_algorithms,
            encap_content_info: encap,
            certificates: None,
            crls: None,
            signer_infos,
        };
        let signed_data_der = signed_data.to_der().expect("SignedData der");
        let signed_data_any =
            Any::from(AnyRef::try_from(signed_data_der.as_slice()).expect("AnyRef"));
        let content_info = ContentInfo {
            content_type: ID_SIGNED_DATA,
            content: signed_data_any,
        };
        content_info.to_der().expect("ContentInfo der")
    }

    #[test]
    #[allow(clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn dac_origin_present_dac_matches_origin_is_accepted() {
        // CD's own vendor_id/product_id_array are 0xFFF1 / 0x8001, but
        // dac_origin says the DAC is scoped to 0x1234 / 0x5678. A DAC at
        // 0x1234 / 0x5678 must be accepted (bound to the origin fields),
        // even though it does NOT match the CD's own vendor_id.
        let tlv = build_inner_cd_tlv(0xFFF1, 0x8001, Some(0x1234), Some(0x5678), &[0x8001]);
        let cd = sign_into_cms(&tlv);
        let trust = CdSigningRoots::with_csa_test_roots();

        verify_certification_declaration(
            &cd,
            VendorId::new(0x1234),
            ProductId::new(0x5678),
            &trust,
        )
        .expect("DAC matching dac_origin VID/PID must be accepted");
    }

    #[test]
    #[allow(clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn dac_origin_present_dac_matches_neither_is_rejected() {
        // dac_origin = 0x1234/0x5678. A DAC at 0xFFF1/0x8001 (the CD's own
        // vendor_id/pid) must be REJECTED, because the override path binds
        // against dac_origin, not the CD's own fields.
        let tlv = build_inner_cd_tlv(0xFFF1, 0x8001, Some(0x1234), Some(0x5678), &[0x8001]);
        let cd = sign_into_cms(&tlv);
        let trust = CdSigningRoots::with_csa_test_roots();

        let err = verify_certification_declaration(
            &cd,
            VendorId::new(0xFFF1),
            ProductId::new(0x8001),
            &trust,
        )
        .expect_err("DAC not matching dac_origin must be rejected");
        assert!(
            matches!(
                err,
                AttestationError::CertificationDeclarationVidMismatch {
                    declared,
                    expected,
                } if declared == VendorId::new(0x1234) && expected == VendorId::new(0xFFF1)
            ),
            "expected VID mismatch against the dac_origin VID, got {err:?}"
        );
    }

    #[test]
    #[allow(clippy::expect_used)] // Test-code carve-out: see CLAUDE.md.
    fn no_dac_origin_uses_vendor_id_and_pid_array() {
        // Without dac_origin, the standard path compares against the CD's
        // own vendor_id / product_id_array (unchanged behaviour).
        let tlv = build_inner_cd_tlv(0xFFF1, 0x8001, None, None, &[0x8001, 0x8002]);
        let cd = sign_into_cms(&tlv);
        let trust = CdSigningRoots::with_csa_test_roots();

        // A PID present in the array is accepted.
        verify_certification_declaration(
            &cd,
            VendorId::new(0xFFF1),
            ProductId::new(0x8002),
            &trust,
        )
        .expect("DAC matching vendor_id and a member of product_id_array accepted");

        // A PID NOT in the array is rejected (still the standard path).
        let err = verify_certification_declaration(
            &cd,
            VendorId::new(0xFFF1),
            ProductId::new(0x9999),
            &trust,
        )
        .expect_err("PID outside product_id_array rejected");
        assert!(
            matches!(err, AttestationError::CertificationDeclarationPidMismatch(p)
                if p == ProductId::new(0x9999)),
            "expected PID mismatch, got {err:?}"
        );
    }
}