46 lines
1.2 KiB
C
46 lines
1.2 KiB
C
#include "secu_defs.h"
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/*!
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* Derive the kNASenc from kasme and perform truncate on the generated key to
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* reduce his size to 128 bits. Definition of the derivation function can
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* be found in 3GPP TS.33401 #A.7
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* @param[in] nas_alg_type NAS algorithm distinguisher
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* @param[in] nas_enc_alg_id NAS encryption/integrity algorithm identifier.
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* Possible values are:
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* - 0 for EIA0 algorithm (Null Integrity Protection algorithm)
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* - 1 for 128-EIA1 SNOW 3G
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* - 2 for 128-EIA2 AES
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* @param[in] kasme Key for MME as provided by AUC
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* @param[out] knas Truncated ouput key as derived by KDF
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*/
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int derive_key_nas(algorithm_distinguisher_t nas_alg_type, uint8_t nas_enc_alg_id,
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uint8_t kasme[32], uint8_t knas[16])
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{
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uint8_t s[7];
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uint8_t knas_temp[32];
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/* FC */
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s[0] = 0x15;
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/* P0 = algorithm type distinguisher */
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s[1] = nas_alg_type & 0xFF;
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/* L0 = length(P0) = 1 */
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s[2] = 0x00;
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s[3] = 0x01;
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/* P1 */
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s[4] = nas_enc_alg_id;
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/* L1 = length(P1) = 1 */
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s[5] = 0x00;
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s[6] = 0x01;
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kdf(s, 7, kasme, 32, knas_temp, 32);
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/* Truncate the generate key to 128 bits */
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memcpy(knas, knas_temp, 16);
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return 0;
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}
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