open-bamboo-networking/src/signing.cpp

// Classifies, signs, and wraps outbound MQTT payloads.
// Only {"print":{...}} messages receive an envelope; all others pass through.
// Envelope: {"header":{"cert_id":"...","payload_len":N,"sign_alg":"RSA_SHA256",
//            "sign_string":"...","sign_ver":"v1.0"},"print":{...sorted keys...}}

#include "obn/signing.hpp"
#include "obn/config.hpp"
#include "obn/json_lite.hpp"
#include "obn/log.hpp"

#include <openssl/bio.h>
#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>
#include <openssl/x509.h>

#include <cctype>
#include <chrono>
#include <cstdint>
#include <cstdio>
#include <memory>
#include <stdexcept>
#include <string>
#include <vector>

namespace obn::signing {

namespace {

struct PkeyDel { void operator()(EVP_PKEY*     p) const { EVP_PKEY_free(p); } };
struct MdDel   { void operator()(EVP_MD_CTX*   p) const { EVP_MD_CTX_free(p); } };
struct CtxDel  { void operator()(EVP_PKEY_CTX* p) const { EVP_PKEY_CTX_free(p); } };
struct X509Del { void operator()(X509*         p) const { X509_free(p); } };
struct BnDel   { void operator()(BIGNUM*       p) const { BN_free(p); } };

static constexpr const char kSignAlg[] = "RSA_SHA256";
static constexpr const char kSignVer[] = "v1.0";

// Resolve the key file path: obn.conf slicer_key_pem, or
// config_dir/slicer_key.pem when empty.
static std::string resolve_key_path()
{
    const auto& cfg = obn::config::current().slicer_key_pem;
    if (!cfg.empty()) return cfg;
    return obn::config::path_in_dir("slicer_key.pem");
}

// Reads a whole file into a string. "" on any failure. `path` is an absolute
// or config-relative path already resolved by the caller.
static std::string read_pem_file(const std::string& path)
{
    if (path.empty()) return {};
    std::FILE* f = std::fopen(path.c_str(), "rb");
    if (!f) return {};
    std::string out;
    char buf[4096];
    std::size_t n;
    while ((n = std::fread(buf, 1, sizeof(buf), f)) > 0)
        out.append(buf, n);
    std::fclose(f);
    return out;
}

} // namespace

std::string slicer_cert_pem()
{
    const auto& cfg = obn::config::current().slicer_cert_pem;
    return read_pem_file(cfg.empty() ? obn::config::path_in_dir("slicer_cert.pem")
                                     : cfg);
}

std::string slicer_crl_pem()
{
    const auto& cfg = obn::config::current().slicer_crl_pem;
    return read_pem_file(cfg.empty() ? obn::config::path_in_dir("slicer_crl.pem")
                                     : cfg);
}

namespace {

// Leaf of slicer_cert.pem (first PEM block). nullptr when absent/unparseable.
static std::unique_ptr<X509, X509Del> load_slicer_leaf_cert()
{
    const std::string pem = slicer_cert_pem();
    if (pem.empty()) return nullptr;
    BIO* bio = ::BIO_new_mem_buf(pem.data(), static_cast<int>(pem.size()));
    if (!bio) return nullptr;
    X509* cert = ::PEM_read_bio_X509(bio, nullptr, nullptr, nullptr);
    ::BIO_free(bio);
    return std::unique_ptr<X509, X509Del>(cert);
}

static std::string leaf_serial_hex_lower(X509* cert)
{
    const ASN1_INTEGER* sn = ::X509_get_serialNumber(cert);
    if (!sn) return {};
    std::unique_ptr<BIGNUM, BnDel> bn(::ASN1_INTEGER_to_BN(sn, nullptr));
    if (!bn) return {};
    char* hex = ::BN_bn2hex(bn.get());
    if (!hex) return {};
    std::string serial(hex);
    ::OPENSSL_free(hex);
    for (char& c : serial)
        c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
    // Wire form uses an even number of hex digits (byte-aligned).
    if (serial.size() % 2)
        serial.insert(serial.begin(), '0');
    return serial;
}

static std::string leaf_issuer_rfc2253(X509* cert)
{
    X509_NAME* name = ::X509_get_issuer_name(cert);
    if (!name) return {};
    BIO* bio = ::BIO_new(::BIO_s_mem());
    if (!bio) return {};
    if (::X509_NAME_print_ex(bio, name, 0, XN_FLAG_RFC2253) < 0) {
        ::BIO_free(bio);
        return {};
    }
    char* data = nullptr;
    const long len = ::BIO_get_mem_data(bio, &data);
    std::string issuer;
    if (data && len > 0)
        issuer.assign(data, static_cast<std::size_t>(len));
    ::BIO_free(bio);
    return issuer;
}

// Parsed once: MQTT cert_id = serial+issuer; HTTP = issuer:serial.
struct AppCertIds {
    std::string mqtt;
    std::string http;
};

static const AppCertIds& app_cert_ids()
{
    static const AppCertIds ids = []() -> AppCertIds {
        auto cert = load_slicer_leaf_cert();
        if (!cert) return {};
        const std::string serial = leaf_serial_hex_lower(cert.get());
        const std::string issuer = leaf_issuer_rfc2253(cert.get());
        if (serial.empty() || issuer.empty()) return {};
        AppCertIds out;
        out.mqtt = serial + issuer;
        out.http = issuer + ":" + serial;
        return out;
    }();
    return ids;
}

} // namespace

// cert_id identifies the slicer's registered signing certificate on Bambu's
// backend. Derived from the leaf of slicer_cert.pem:
//   lowercase_hex(serial) + issuer_RFC2253  (no separator).
const std::string& slicer_cert_id()
{
    return app_cert_ids().mqtt;
}

// HTTP x-bbl-app-certification-id: issuer_RFC2253 + ":" + serial.lower(),
// from the same leaf parse as slicer_cert_id().
const std::string& app_certification_id()
{
    return app_cert_ids().http;
}

namespace {

static std::unique_ptr<EVP_PKEY, PkeyDel> load_pkey()
{
    std::string path = resolve_key_path();
    if (path.empty()) return nullptr;

    std::FILE* f = std::fopen(path.c_str(), "r");
    if (!f) return nullptr;

    EVP_PKEY* raw = PEM_read_PrivateKey(f, nullptr, nullptr, nullptr);
    std::fclose(f);

    return std::unique_ptr<EVP_PKEY, PkeyDel>(raw);
}

EVP_PKEY* slicer_pkey()
{
    static const std::unique_ptr<EVP_PKEY, PkeyDel> key = load_pkey();
    return key.get();
}


// RSA-PKCS#1 v1.5 + SHA-256 over `data`, returned as base64.
std::string rsa_sha256_sign_b64(EVP_PKEY* pkey,
                                 const unsigned char* data, std::size_t len)
{
    if (!pkey) return {};
    std::unique_ptr<EVP_MD_CTX, MdDel> ctx(EVP_MD_CTX_new());
    if (!ctx) throw std::runtime_error("signing: EVP_MD_CTX_new failed");
    if (EVP_DigestSignInit(ctx.get(), nullptr, EVP_sha256(), nullptr, pkey) != 1)
        throw std::runtime_error("signing: EVP_DigestSignInit failed");
    if (EVP_DigestSignUpdate(ctx.get(), data, len) != 1)
        throw std::runtime_error("signing: EVP_DigestSignUpdate failed");
    std::size_t siglen = 0;
    if (EVP_DigestSignFinal(ctx.get(), nullptr, &siglen) != 1 || siglen == 0)
        throw std::runtime_error("signing: EVP_DigestSignFinal (size query) failed");
    std::vector<unsigned char> sig(siglen);
    if (EVP_DigestSignFinal(ctx.get(), sig.data(), &siglen) != 1)
        throw std::runtime_error("signing: EVP_DigestSignFinal failed");
    return base64_encode(sig.data(), siglen);
}

// Raw RSA PKCS#1 v1.5 signature over `data` — the data IS the signed message,
// NOT its hash. Unlike rsa_sha256_sign_b64, no digest is applied and no
// DigestInfo is prepended: the encoded block is 00 01 FF..FF 00 || data.
// Returned as base64.
std::string rsa_pkcs1_sign_raw_b64(EVP_PKEY* pkey,
                                   const unsigned char* data, std::size_t len)
{
    if (!pkey) return {};
    std::unique_ptr<EVP_PKEY_CTX, CtxDel> ctx(EVP_PKEY_CTX_new(pkey, nullptr));
    if (!ctx) throw std::runtime_error("signing: EVP_PKEY_CTX_new failed");
    if (EVP_PKEY_sign_init(ctx.get()) != 1)
        throw std::runtime_error("signing: EVP_PKEY_sign_init failed");
    if (EVP_PKEY_CTX_set_rsa_padding(ctx.get(), RSA_PKCS1_PADDING) != 1)
        throw std::runtime_error("signing: set_rsa_padding failed");
    std::size_t siglen = 0;
    if (EVP_PKEY_sign(ctx.get(), nullptr, &siglen, data, len) != 1 || siglen == 0)
        throw std::runtime_error("signing: EVP_PKEY_sign (size query) failed");
    std::vector<unsigned char> sig(siglen);
    if (EVP_PKEY_sign(ctx.get(), sig.data(), &siglen, data, len) != 1)
        throw std::runtime_error("signing: EVP_PKEY_sign failed");
    return base64_encode(sig.data(), siglen);
}

// Returns "print", "liveview" (only for prepare commands), or empty if neither.
std::string signable_root_key(const std::string& payload) noexcept
{
    const char* p   = payload.data();
    const char* end = p + payload.size();
    while (p < end && (*p == ' ' || *p == '\t' || *p == '\r' || *p == '\n')) ++p;
    if (p >= end || *p != '{') return {};
    ++p;
    while (p < end && (*p == ' ' || *p == '\t' || *p == '\r' || *p == '\n')) ++p;
    if (p >= end || *p != '"') return {};
    ++p;
    const char* kstart = p;
    while (p < end && *p != '"') ++p;
    if (p >= end) return {};
    std::string key(kstart, p - kstart);
    if (key == "print") return key;
    if (key == "liveview") {
        if (payload.find("\"prepare\"") != std::string::npos) return key;
    }
    return {};
}

// The one field each command carries as device-cert ciphertext
// (research/10.03): project_file's model url, gcode_line's raw G-code,
// prepare's liveview ttcode.
// project_file's `param` is the plate path the firmware reads in cleartext;
// encrypting (and dropping) it makes the printer fail with 0500-4003
// (cannot parse file).
const char* encrypted_field_for(const obn::json::Object& obj)
{
    auto cmd = obj.find("command");
    if (cmd == obj.end() || !cmd->second.is_string()) return nullptr;
    const std::string c = cmd->second.as_string();
    if (c == "project_file") return "url";
    if (c == "gcode_line")   return "param";
    if (c == "prepare")      return "ttcode";
    return nullptr;
}

// Applies device-cert field encryption to the parsed `print` object in place:
// adds `<field>_enc` (RSA). On a secured printer (`developer_mode == false`)
// the cleartext field is then DROPPED, because secured firmware reads only
// *_enc and rejects a message carrying both (gcode_line -> err 84033545
// "mqtt message verify failed"; research/§10.3). When `developer_mode == true`
// the cleartext is kept, because Developer Mode firmware ignores *_enc and
// reads the cleartext instead. The caller derives `developer_mode` per printer
// from push_status print.fun bit 29 (Agent::developer_mode_effective).
// Idempotent when `*_enc` already exists. Without a device key (or when RSA
// fails) logs ERROR and leaves the cleartext.
void encrypt_print_fields(obn::json::Object& obj, EVP_PKEY* device_pub,
                          bool developer_mode)
{
    const char* field = encrypted_field_for(obj);
    if (!field) return;
    const std::string enc_key = std::string(field) + "_enc";
    auto it = obj.find(field);
    if (it == obj.end() || !it->second.is_string() || obj.count(enc_key)) return;
    if (!device_pub) {
        OBN_ERROR("no device public key; leaving %s cleartext "
                  "(printer will reject if secured)", field);
        return;
    }
    std::string enc_err;
    std::string enc = rsa_pkcs1v15_encrypt_b64(device_pub, it->second.as_string(),
                                               &enc_err);
    if (enc.empty()) {
        OBN_ERROR("RSA encrypt of '%s' failed: %s; leaving cleartext",
                  field, enc_err.empty() ? "unknown" : enc_err.c_str());
        return;
    }
    obj[enc_key] = obn::json::Value(std::move(enc));
    if (!developer_mode)
        obj.erase(it);
}

// Builds the command dump ({...sorted keys...}) after optional field encryption.
// Uses json_lite, whose Object type is std::map, so dump() already sorts keys.
std::string build_command_dump(const std::string& root_key,
                               const std::string& payload,
                               EVP_PKEY*          device_pub,
                               bool               developer_mode)
{
    auto root = obn::json::parse(payload);
    if (!root) return {};
    const obn::json::Value& cmd = root->find(root_key.c_str());
    if (cmd.kind() != obn::json::Value::Kind::Object) return {};
    obn::json::Object obj = cmd.as_object(); // copy for mutation
    encrypt_print_fields(obj, device_pub, developer_mode);
    return obn::json::Value(std::move(obj)).dump();
}

// Escapes backslash and double-quote for embedding inside a JSON string
// literal whose surrounding quotes are managed by the caller.
static std::string json_str_escape(const std::string& s)
{
    std::string out;
    out.reserve(s.size());
    for (char c : s) {
        if (c == '\\' || c == '"') out += '\\';
        out += c;
    }
    return out;
}

// Emits {"header":…,"<root_key>":dump} ONLY — trailing siblings in the input
// payload are not carried. See the invariant comment at to_sign (maybe_sign)
// below, locked by test_trailing_sibling_reconstruction in tests/signing_test.cpp.
// Builds the complete signed envelope JSON string.
std::string build_envelope(const std::string& to_sign,
                           const std::string& sig_b64,
                           const std::string& root_key,
                           const std::string& dump)
{
    std::string out;
    out.reserve(to_sign.size() + sig_b64.size() + 200);
    out += "{\"header\":{\"cert_id\":\"";
    out += json_str_escape(slicer_cert_id());
    out += "\",\"payload_len\":";
    out += std::to_string(to_sign.size());
    out += ",\"sign_alg\":\"";
    out += kSignAlg;
    out += "\",\"sign_string\":\"";
    out += json_str_escape(sig_b64);
    out += "\",\"sign_ver\":\"";
    out += kSignVer;
    out += "\"},\"" + root_key + "\":";
    out += dump;
    out += '}';
    return out;
}

} // namespace

bool would_sign(const std::string& payload_json)
{
    return !signable_root_key(payload_json).empty() && slicer_pkey() != nullptr;
}

bool slicer_signing_key_present()
{
    return slicer_pkey() != nullptr;
}

std::string maybe_sign(const std::string& payload_json, EVP_PKEY* device_pub,
                       bool developer_mode)
{
    const std::string root_key = signable_root_key(payload_json);
    if (root_key.empty()) return payload_json;

    EVP_PKEY* pkey = slicer_pkey();
    if (!pkey) return payload_json;

    const std::string dump =
        build_command_dump(root_key, payload_json, device_pub, developer_mode);
    if (dump.empty()) return payload_json; // malformed; pass through

    // SINGLE-ROOT WRAPPER INVARIANT (locked by test_trailing_sibling_reconstruction
    // in tests/signing_test.cpp): to_sign is exactly {"<root_key>":<dump>} —
    // family key first, single root, never sorted at the root level; the dump
    // here is byte-identical to the dump build_envelope emits (it receives the
    // same string), so payload_len == bytes signed == wire bytes.
    // A payload with trailing siblings (e.g. {"print":...,"user_id":...}) currently
    // DROPS the sibling — pinned, not fixed (research/10.04 Signing consensus;
    // diverges from the #72/farm consensus, which signs envelope-minus-header
    // including user_id).
    const std::string to_sign = "{\"" + root_key + "\":" + dump + "}";

    const std::string sig_b64 = rsa_sha256_sign_b64(
        pkey,
        reinterpret_cast<const unsigned char*>(to_sign.data()), to_sign.size());

    return build_envelope(to_sign, sig_b64, root_key, dump);
}

std::string sign_bytes(const std::string& data)
{
    EVP_PKEY* pkey = slicer_pkey();
    if (!pkey) {
        const auto& d = obn::config::dir();
        throw std::runtime_error(
            "signing: no key loaded; set slicer_key_pem in obn.conf "
            "or place slicer_key.pem in the config directory ("
            + (d.empty() ? "<not set>" : d) + ")");
    }
    return rsa_sha256_sign_b64(
        pkey,
        reinterpret_cast<const unsigned char*>(data.data()), data.size());
}

std::string device_security_sign()
{
    EVP_PKEY* pkey = slicer_pkey();
    // Degrade gracefully when no slicer key is configured (same as maybe_sign):
    // return empty so the caller omits the header rather than crashing the
    // cloud-connect/print path. The header is only enforced on signed writes.
    if (!pkey) return {};
    // The proprietary plugin signs the *current* time in milliseconds (as a
    // decimal string) with a raw RSA PKCS#1 v1.5 signature — no hash. The
    // cloud recovers the timestamp from the signature and checks it is recent
    // (replay protection).
    const auto ms = std::chrono::duration_cast<std::chrono::milliseconds>(
                        std::chrono::system_clock::now().time_since_epoch()).count();
    const std::string ts = std::to_string(ms);
    return rsa_pkcs1_sign_raw_b64(
        pkey,
        reinterpret_cast<const unsigned char*>(ts.data()), ts.size());
}

bool add_pop_headers(std::map<std::string, std::string>& headers)
{
    const std::string& cert_id  = app_certification_id();
    const std::string  sec_sign = device_security_sign();
    if (cert_id.empty() || sec_sign.empty()) return false;
    headers["x-bbl-app-certification-id"] = cert_id;
    headers["x-bbl-device-security-sign"] = sec_sign;
    return true;
}

// Blockwise RSA-PKCS#1 v1.5 encryption -> base64. Splits `plaintext` into
// <=kMaxChunk-byte pieces so the total ciphertext is a concatenation of
// key-sized blocks (matching the stock plugin's url_enc / param_enc form).
std::string rsa_pkcs1v15_encrypt_b64(EVP_PKEY* pub, const std::string& plaintext,
                                     std::string* err)
{
    if (!pub) {
        if (err) *err = "null public key";
        return {};
    }

    // PKCS#1 v1.5 max plaintext per block = RSA modulus bytes - 11.
    const int key_bytes = EVP_PKEY_size(pub); // ciphertext block size (e.g. 256)
    if (key_bytes <= 11) {
        if (err) *err = "RSA key too small";
        return {};
    }
    const std::size_t max_chunk = static_cast<std::size_t>(key_bytes - 11);

    std::unique_ptr<EVP_PKEY_CTX, CtxDel> ctx(EVP_PKEY_CTX_new(pub, nullptr));
    if (!ctx) {
        if (err) *err = "EVP_PKEY_CTX_new failed";
        return {};
    }
    if (EVP_PKEY_encrypt_init(ctx.get()) <= 0 ||
        EVP_PKEY_CTX_set_rsa_padding(ctx.get(), RSA_PKCS1_PADDING) <= 0) {
        char ebuf[256];
        ERR_error_string_n(ERR_peek_last_error(), ebuf, sizeof(ebuf));
        if (err) *err = std::string("encrypt init/padding failed: ") + ebuf;
        return {};
    }

    std::vector<unsigned char> out;
    const auto* p = reinterpret_cast<const unsigned char*>(plaintext.data());
    std::size_t remaining = plaintext.size();
    std::size_t offset    = 0;
    // A zero-length input still produces one block (the plugin never encrypts
    // empty fields, but keep the loop robust rather than emit nothing).
    do {
        const std::size_t chunk = remaining < max_chunk ? remaining : max_chunk;
        std::size_t block_len = 0;
        if (EVP_PKEY_encrypt(ctx.get(), nullptr, &block_len, p + offset, chunk) <= 0) {
            char ebuf[256];
            ERR_error_string_n(ERR_peek_last_error(), ebuf, sizeof(ebuf));
            if (err) *err = std::string("EVP_PKEY_encrypt size query failed: ") + ebuf;
            return {};
        }
        const std::size_t base = out.size();
        out.resize(base + block_len);
        if (EVP_PKEY_encrypt(ctx.get(), out.data() + base, &block_len,
                             p + offset, chunk) <= 0) {
            char ebuf[256];
            ERR_error_string_n(ERR_peek_last_error(), ebuf, sizeof(ebuf));
            if (err) *err = std::string("EVP_PKEY_encrypt failed: ") + ebuf;
            return {};
        }
        out.resize(base + block_len);
        offset    += chunk;
        remaining -= chunk;
    } while (remaining > 0);

    return base64_encode(out.data(), out.size());
}

static constexpr char kB64Tbl[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

std::string base64_encode(const unsigned char* data, std::size_t len)
{
    std::string out;
    out.reserve(((len + 2) / 3) * 4);
    for (std::size_t i = 0; i < len; i += 3) {
        std::uint32_t w = static_cast<std::uint32_t>(data[i]) << 16;
        if (i + 1 < len) w |= static_cast<std::uint32_t>(data[i + 1]) << 8;
        if (i + 2 < len) w |= static_cast<std::uint32_t>(data[i + 2]);
        out.push_back(kB64Tbl[(w >> 18) & 63]);
        out.push_back(kB64Tbl[(w >> 12) & 63]);
        out.push_back(i + 1 < len ? kB64Tbl[(w >> 6) & 63] : '=');
        out.push_back(i + 2 < len ? kB64Tbl[w & 63] : '=');
    }
    return out;
}

bool slicer_app_cert_usable()
{
    // app_cert_install needs the app certificate PEM + CRL only (no private
    // key). Defaults under config_dir count when obn.conf paths are empty.
    // Soft date/revocation issues still return true (firmware accepts expired
    // official CRLs); WARN once — Studio calls install_device_cert ~1 Hz.
    // The cert id is logged once on the first successful check for the same
    // reason.
    static bool warned_cert_dates = false;
    static bool warned_crl_dates = false;
    static bool warned_revoked = false;
    static bool logged_cert_id = false;

    const std::string pem = slicer_cert_pem();
    if (pem.empty()) return false;
    const std::string crl_pem = slicer_crl_pem();
    if (crl_pem.empty()) return false;

    BIO* bio = ::BIO_new_mem_buf(pem.data(), static_cast<int>(pem.size()));
    if (!bio) return false;
    X509* cert = ::PEM_read_bio_X509(bio, nullptr, nullptr, nullptr);
    ::BIO_free(bio);
    if (!cert) {
        OBN_ERROR("signing: slicer_cert.pem is not a valid X.509 certificate");
        return false;
    }

    // notBefore must be in the past; notAfter must be in the future.
    // X509_cmp_current_time: <0 if asn1_time is before now, >0 if after.
    const ASN1_TIME* not_before = ::X509_get0_notBefore(cert);
    const ASN1_TIME* not_after  = ::X509_get0_notAfter(cert);
    const bool not_yet = not_before && ::X509_cmp_current_time(not_before) > 0;
    const bool expired = !not_after || ::X509_cmp_current_time(not_after) < 0;
    if ((not_yet || expired) && !warned_cert_dates) {
        warned_cert_dates = true;
        OBN_WARN("signing: slicer app certificate is %s "
                 "(still usable for app_cert_install)",
                 expired ? "expired" : "not yet valid");
    }

    BIO* crl_bio = ::BIO_new_mem_buf(crl_pem.data(),
                                     static_cast<int>(crl_pem.size()));
    if (!crl_bio) {
        ::X509_free(cert);
        return false;
    }
    X509_CRL* crl = ::PEM_read_bio_X509_CRL(crl_bio, nullptr, nullptr, nullptr);
    ::BIO_free(crl_bio);
    if (!crl) {
        ::X509_free(cert);
        OBN_ERROR("signing: slicer_crl.pem is not a valid X.509 CRL");
        return false;
    }

    // lastUpdate (thisUpdate) must be in the past; nextUpdate, when present,
    // must be in the future. Missing nextUpdate is treated as still valid —
    // some CRLs omit it; request_app_cert_install still needs the PEM.
    // Official Bambu CRLs are often past nextUpdate; printer still accepts them.
    const ASN1_TIME* last_update = ::X509_CRL_get0_lastUpdate(crl);
    const ASN1_TIME* next_update = ::X509_CRL_get0_nextUpdate(crl);
    const bool crl_not_yet = last_update && ::X509_cmp_current_time(last_update) > 0;
    const bool crl_expired = next_update && ::X509_cmp_current_time(next_update) < 0;
    if ((crl_not_yet || crl_expired) && !warned_crl_dates) {
        warned_crl_dates = true;
        OBN_WARN("signing: slicer app CRL is %s "
                 "(still usable for app_cert_install; firmware ignores nextUpdate)",
                 crl_expired ? "expired" : "not yet valid");
    }

    // Soft-warn if this leaf appears on the CRL (still allow install).
    X509_REVOKED* revoked = nullptr;
    if (::X509_CRL_get0_by_cert(crl, &revoked, cert) == 1 && !warned_revoked) {
        warned_revoked = true;
        OBN_WARN("signing: slicer app certificate is revoked on slicer_crl.pem "
                 "(still usable for app_cert_install)");
    }

    ::X509_CRL_free(crl);
    ::X509_free(cert);

    if (!logged_cert_id) {
        logged_cert_id = true;
        const std::string& id = slicer_cert_id();
        if (id.empty())
            OBN_WARN("signing: slicer app certificate loaded but cert_id is empty");
        else
            OBN_INFO("signing: slicer app certificate id %s", id.c_str());
    }
    return true;
}

} // namespace obn::signing