certificate_cache.hpp

#pragma once
#include <vanetza/security/hashed_id.hpp>
#include <vanetza/security/v3/certificate.hpp>
#include <unordered_map>
#include <unordered_set>
 
namespace vanetza
{
namespace security
{
namespace v3
{
 
/**
 * CertificateCache stores validated v1.3.1 certificates for later lookup.
 * Required for checking messages' signatures containing only a certificate digest.
 */
class CertificateCache
{
public:
    /**
     * Lookup certificate based on given digest
     * \param digest certificate digest
     * \return certificate matching digest
     */
    const Certificate* lookup(const HashedId8& digest) const;
    const Certificate* lookup(const HashedId3& digest) const;
 
    /**
     * Store a (pre-validated) certificate in cache
     * \param cert certificate
     */
    void store(Certificate cert);
 
    size_t size() const { return m_storage.size(); }
 
    /**
     * Announce a station with a given certificate digest.
     * \param digest certificate digest
     * \return true if digest was not known before
     */
    bool announce(const HashedId8& digest);
 
    /**
     * Test if a certificate digest is already known, i.e. either
     * its certificate is stored or at least the digest has been announced.
     * \param digest certificate digest
     * \return true if digest is known
     */
    bool is_known(const HashedId8& digest) const;
 
private:
    using CertificateMap = std::unordered_map<HashedId8, Certificate>;
    using ShortDigestMap = std::unordered_map<HashedId3, CertificateMap::iterator>;
 
    // TODO add bounded capacity and automatic removal of expired certificates
    CertificateMap m_storage;
    ShortDigestMap m_short_digests;
    std::unordered_set<HashedId8> m_digests;
};
 
} // namespace v3
} // namespace security
} // namespace vanetza