KExp15 (Р 1323565.1.017) key wrapping mechanism uses GOST
cryptography algorithms. KEK is 32+8+32=72 bytes long.

    Kenc || IV || Kauth = KEK
    KExp15(Kenc, Kauth, IV, CEK) = Kuznechik-CTR(
        Kenc, CEK || Kuznechik-CMAC(Kauth, IV || CEK), IV=IV)

=> RFC 7801, Kuznechik, GOST R 34.12-2015 
CMAC (OMAC1) is described in GOST R 34.13-2015.