| /* Utility functions from ogslib imported to TTCN-3 |
| * |
| * (C) 2019 Harald Welte <laforge@gnumonks.org> |
| * All rights reserved. |
| * |
| * Released under the terms of GNU General Public License, Version 2 or |
| * (at your option) any later version. |
| * |
| * SPDX-License-Identifier: GPL-2.0-or-later |
| */ |
| |
| module LTE_CryptoFunctions { |
| |
| import from General_Types all; |
| import from Misc_Helpers all; |
| |
| import from S1AP_Types all; |
| import from S1AP_PDU_Descriptions all; |
| |
| import from NAS_EPS_Types all; |
| import from NAS_Templates all; |
| |
| /********************************************************************************* |
| * low-level API (external C/C++ code) |
| *********************************************************************************/ |
| |
| external function f_snow_3g_f8(in OCT16 key, in integer count, in integer bearer, |
| in boolean is_downlink, in octetstring data) return octetstring; |
| |
| external function f_snow_3g_f9(in OCT16 key, in integer count, in integer fresh, |
| in boolean is_downlink, in octetstring data) return OCT4; |
| |
| external function f_kdf_kasme(in OCT16 ck, in OCT16 ik, in OCT3 plmn_id, |
| in OCT6 sqn, in OCT6 ak) return OCT32; |
| |
| external function f_kdf_nas_int(in integer alg_id, in OCT32 kasme) return OCT32; |
| external function f_kdf_nas_enc(in integer alg_id, in OCT32 kasme) return OCT32; |
| |
| external function f_kdf_enb(in OCT16 kasme, in integer ul_count) return OCT32; |
| |
| external function f_kdf_nh(in OCT16 kasme, in OCT32 sync_inp) return OCT32; |
| |
| /********************************************************************************* |
| * mid-level API |
| *********************************************************************************/ |
| |
| function f_nas_mac_calc(NAS_ALG_INT alg, octetstring k_nas_int, integer seq_nr, |
| integer bearer, boolean is_downlink, octetstring data) return OCT4 { |
| select (alg) { |
| case (NAS_ALG_IP_EIA0) { |
| return '00000000'O; |
| } |
| case (NAS_ALG_IP_EIA1) { |
| return f_snow_3g_f9(k_nas_int, seq_nr, bearer, is_downlink, data); |
| } |
| case else { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("Unsupported EIA: ", alg)); |
| return '00000000'O; /* never reached */ |
| } |
| } |
| } |
| |
| function f_nas_encrypt(NAS_ALG_ENC alg, octetstring k_nas_enc, integer count, |
| integer bearer, boolean is_downlink, inout octetstring data) { |
| select (alg) { |
| case (NAS_ALG_ENC_EEA0) { } |
| case (NAS_ALG_ENC_EEA1) { |
| f_snow_3g_f8(k_nas_enc, count, bearer, is_downlink, data); |
| } |
| case else { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("Unsupported EEA: ", alg)); |
| } |
| } |
| } |
| |
| |
| /********************************************************************************* |
| * high-level API (full NAS encapsulation/decapsulation) |
| *********************************************************************************/ |
| |
| type record NAS_UE_State { |
| NAS_Role role, /* ATS implements UE or MME role? */ |
| |
| NAS_ALG_INT alg_int, /* NAS Integrity Protection Algorithm */ |
| octetstring k_nas_int, /* NAS Integrity Protection Key */ |
| NAS_ALG_ENC alg_enc, /* NAS Encryption Algorithm */ |
| octetstring k_nas_enc, /* NAS Encryption Key */ |
| integer rx_count, /* frame counter (ATS rx side) */ |
| integer tx_count /* frame counter (ATS tx side) */ |
| }; |
| |
| template (value) NAS_UE_State t_NAS_UE_State(NAS_Role role) := { |
| role := role, |
| alg_int := NAS_ALG_IP_EIA0, |
| k_nas_int := ''O, |
| alg_enc := NAS_ALG_ENC_EEA0, |
| k_nas_enc := ''O, |
| rx_count := 0, |
| tx_count := 0 |
| }; |
| |
| type enumerated NAS_Role { |
| NAS_ROLE_UE, /* ATS implements/emulates UE */ |
| NAS_ROLE_MME /* ATS implements/emulates MME */ |
| }; |
| type enumerated NAS_ALG_INT { |
| NAS_ALG_IP_EIA0, /* no integrity protection */ |
| NAS_ALG_IP_EIA1, /* SNOW-3G F9 based */ |
| NAS_ALG_IP_EIA2, /* AES based */ |
| NAS_ALG_IP_EIA3 /* ZUC */ |
| }; |
| type enumerated NAS_ALG_ENC { |
| NAS_ALG_ENC_EEA0, /* no encryption */ |
| NAS_ALG_ENC_EEA1, /* SNOW-3G F8 based */ |
| NAS_ALG_ENC_EEA2, /* AES based */ |
| NAS_ALG_ENC_EEA3 /* ZUC */ |
| }; |
| |
| /* port between individual per-connection components and this translator */ |
| type port S1AP_NAS_Conn_PT message { |
| inout S1AP_PDU, PDU_NAS_EPS; |
| } with { extension "internal" }; |
| |
| /* determine if a received (from the IUT) message is downlink or not */ |
| private function f_rx_is_downlink(in NAS_UE_State nus) return boolean |
| { |
| if (nus.role == NAS_ROLE_UE) { |
| return true; |
| } else { |
| return false; |
| } |
| } |
| |
| /* determine if a message transmitted to the IUT message is downlink or not */ |
| private function f_tx_is_downlink(in NAS_UE_State nus) return boolean |
| { |
| return not f_rx_is_downlink(nus); |
| } |
| |
| private function f_nas_check_ip(inout NAS_UE_State nus, |
| in PDU_NAS_EPS_SecurityProtectedNASMessage secp_nas) return boolean |
| { |
| var octetstring data_with_seq := int2oct(secp_nas.sequenceNumber, 1) & secp_nas.nAS_Message; |
| var OCT4 exp_mac := f_nas_mac_calc(nus.alg_int, nus.k_nas_int, nus.rx_count, 0, |
| f_rx_is_downlink(nus), data_with_seq); |
| if (exp_mac != secp_nas.messageAuthenticationCode) { |
| setverdict(fail, "Received NAS MAC ", secp_nas.messageAuthenticationCode, |
| " doesn't match expected MAC ", exp_mac, ": ", secp_nas); |
| return false; |
| } |
| return true; |
| } |
| |
| /* try to decapsulate (MAC verify, decrypt) NAS message */ |
| function f_nas_try_decaps(inout NAS_UE_State nus, PDU_NAS_EPS nas) return PDU_NAS_EPS |
| { |
| var PDU_NAS_EPS_SecurityProtectedNASMessage secp_nas; |
| |
| /* transparently pass through any non-protected NAS */ |
| if (not match(nas, tr_NAS_EMM_SecurityProtected)) { |
| return nas; |
| } |
| |
| /* process any security-protected NAS */ |
| secp_nas := nas.ePS_messages.ePS_MobilityManagement.pDU_NAS_EPS_SecurityProtectedNASMessage; |
| select (secp_nas.securityHeaderType) { |
| case ('0011'B) { /* IP with new EPS security context */ |
| nus.rx_count := 0; |
| nus.alg_int := NAS_ALG_IP_EIA1; /* FIXME: from decoded inner message! */ |
| if (not f_nas_check_ip(nus, secp_nas)) { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "f_nas_check_ip() failed"); |
| } |
| return dec_PDU_NAS_EPS(secp_nas.nAS_Message); |
| } |
| case ('0001'B) { /* IP only */ |
| if (not f_nas_check_ip(nus, secp_nas)) { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "f_nas_check_ip() failed"); |
| } |
| return dec_PDU_NAS_EPS(secp_nas.nAS_Message); |
| } |
| case ('0010'B) { /* IP + ciphered */ |
| if (not f_nas_check_ip(nus, secp_nas)) { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "f_nas_check_ip() failed"); |
| } |
| f_nas_encrypt(nus.alg_enc, nus.k_nas_enc, nus.rx_count, 0, |
| f_rx_is_downlink(nus), secp_nas.nAS_Message); |
| return dec_PDU_NAS_EPS(secp_nas.nAS_Message); |
| } |
| case ('0100'B) { /* IP + ciphered; new EPS security context */ |
| nus.rx_count := 0; |
| if (not f_nas_check_ip(nus, secp_nas)) { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "f_nas_check_ip() failed"); |
| } |
| f_nas_encrypt(nus.alg_enc, nus.k_nas_enc, nus.rx_count, 0, |
| f_rx_is_downlink(nus), secp_nas.nAS_Message); |
| return dec_PDU_NAS_EPS(secp_nas.nAS_Message); |
| } |
| //case ('0101'B) { /* IP + partially ciphered */ } |
| //case ('1100'B) { /* Service Request Message */ } |
| case else { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("Implement SecHdrType for ", secp_nas)); |
| mtc.stop; /* make compiler happy about not returning. */ |
| } |
| } |
| } |
| |
| private function f_nas_determine_sec_hdr_t(boolean encrypt, boolean authenticate, boolean new_ctx) |
| return BIT4 |
| { |
| if (encrypt == false and authenticate == false and new_ctx == false) { |
| return '0000'B; |
| } else if (encrypt == false and authenticate == true and new_ctx == false) { |
| return '0001'B; |
| } else if (encrypt == false and authenticate == true and new_ctx == true) { |
| return '0011'B; |
| } else if (encrypt == true and authenticate == true and new_ctx == true) { |
| return '0100'B; |
| } else if (encrypt == true and authenticate == true and new_ctx == false) { |
| return '0010'B; |
| } else { |
| Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Invalid sec_hdr conditions"); |
| return '0000'B; /* never reached, make compiler happy */ |
| } |
| } |
| |
| /* encapsulate a NAS message (encrypt, MAC) */ |
| function f_nas_encaps(inout NAS_UE_State nus, PDU_NAS_EPS nas_in, boolean new_ctx := false) |
| return PDU_NAS_EPS |
| { |
| var boolean encrypt := false; |
| var boolean authenticate := false; |
| if (nus.alg_int != NAS_ALG_IP_EIA0) { |
| authenticate := true; |
| } |
| if (nus.alg_enc != NAS_ALG_ENC_EEA0) { |
| encrypt := true; |
| } |
| |
| if (encrypt == false and authenticate == false) { |
| return nas_in; |
| } |
| |
| if (new_ctx) { |
| nus.tx_count := 0; |
| } |
| |
| var BIT4 sec_hdr_t := f_nas_determine_sec_hdr_t(encrypt, authenticate, new_ctx); |
| var octetstring nas_enc := enc_PDU_NAS_EPS(nas_in); |
| if (encrypt) { |
| f_nas_encrypt(nus.alg_enc, nus.k_nas_enc, nus.tx_count, 0, |
| f_tx_is_downlink(nus), nas_enc); |
| } |
| var PDU_NAS_EPS nas_out; |
| nas_out := valueof(ts_NAS_EMM_SecurityProtected(sec_hdr_t, nus.tx_count, nas_enc)); |
| if (authenticate) { |
| var OCT4 mac := f_nas_mac_calc(nus.alg_int, nus.k_nas_int, nus.tx_count, 0, |
| f_tx_is_downlink(nus), '00'O & nas_enc); |
| nas_out.ePS_messages.ePS_MobilityManagement.pDU_NAS_EPS_SecurityProtectedNASMessage.messageAuthenticationCode := mac; |
| } |
| return nas_out; |
| } |
| |
| } // namespace |