Crypto.h

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#pragma once
 
#include <mbedtls/gcm.h>
 
#include <cstddef>
#include <cstdint>
 
namespace cdc::core {

class GcmContext {
public:
    GcmContext() { mbedtls_gcm_init(&ctx_); }
    ~GcmContext() { mbedtls_gcm_free(&ctx_); }
    GcmContext(const GcmContext&) = delete;
    GcmContext& operator=(const GcmContext&) = delete;
    GcmContext(GcmContext&&) = delete;
    GcmContext& operator=(GcmContext&&) = delete;
    mbedtls_gcm_context* get() { return &ctx_; }
private:
    mbedtls_gcm_context ctx_;
};

inline bool aesGcm256Seal(const uint8_t key[32],
                          const uint8_t* iv, size_t ivLen,
                          const uint8_t* aad, size_t aadLen,
                          const uint8_t* pt, size_t ptLen,
                          uint8_t* ctOut, uint8_t tagOut[16]) {
    GcmContext gcm;
    int rc = mbedtls_gcm_setkey(gcm.get(), MBEDTLS_CIPHER_ID_AES, key, 256);
    if (rc == 0) {
        rc = mbedtls_gcm_crypt_and_tag(
            gcm.get(), MBEDTLS_GCM_ENCRYPT, ptLen,
            iv, ivLen,
            aad, aadLen,
            pt, ctOut,
            16, tagOut);
    }
    return rc == 0;
}

inline bool aesGcm256Open(const uint8_t key[32],
                          const uint8_t* iv, size_t ivLen,
                          const uint8_t* aad, size_t aadLen,
                          const uint8_t* ct, size_t ctLen,
                          const uint8_t tag[16], uint8_t* ptOut) {
    GcmContext gcm;
    int rc = mbedtls_gcm_setkey(gcm.get(), MBEDTLS_CIPHER_ID_AES, key, 256);
    if (rc == 0) {
        rc = mbedtls_gcm_auth_decrypt(
            gcm.get(), ctLen,
            iv, ivLen,
            aad, aadLen,
            tag, 16,
            ct, ptOut);
    }
    return rc == 0;
}
 
} // namespace cdc::core