15b9c547cSRui Paulo /* 2*85732ac8SCy Schubert * HMAC-SHA256 KDF (RFC 5295) and HKDF-Expand(SHA256) (RFC 5869) 3*85732ac8SCy Schubert * Copyright (c) 2014-2017, Jouni Malinen <j@w1.fi> 45b9c547cSRui Paulo * 55b9c547cSRui Paulo * This software may be distributed under the terms of the BSD license. 65b9c547cSRui Paulo * See README for more details. 75b9c547cSRui Paulo */ 85b9c547cSRui Paulo 95b9c547cSRui Paulo #include "includes.h" 105b9c547cSRui Paulo 115b9c547cSRui Paulo #include "common.h" 125b9c547cSRui Paulo #include "sha256.h" 135b9c547cSRui Paulo 145b9c547cSRui Paulo 155b9c547cSRui Paulo /** 165b9c547cSRui Paulo * hmac_sha256_kdf - HMAC-SHA256 based KDF (RFC 5295) 175b9c547cSRui Paulo * @secret: Key for KDF 185b9c547cSRui Paulo * @secret_len: Length of the key in bytes 19*85732ac8SCy Schubert * @label: A unique label for each purpose of the KDF or %NULL to select 20*85732ac8SCy Schubert * RFC 5869 HKDF-Expand() with arbitrary seed (= info) 215b9c547cSRui Paulo * @seed: Seed value to bind into the key 225b9c547cSRui Paulo * @seed_len: Length of the seed 235b9c547cSRui Paulo * @out: Buffer for the generated pseudo-random key 245b9c547cSRui Paulo * @outlen: Number of bytes of key to generate 255b9c547cSRui Paulo * Returns: 0 on success, -1 on failure. 265b9c547cSRui Paulo * 275b9c547cSRui Paulo * This function is used to derive new, cryptographically separate keys from a 28*85732ac8SCy Schubert * given key in ERP. This KDF is defined in RFC 5295, Chapter 3.1.2. When used 29*85732ac8SCy Schubert * with label = NULL and seed = info, this matches HKDF-Expand() defined in 30*85732ac8SCy Schubert * RFC 5869, Chapter 2.3. 315b9c547cSRui Paulo */ 325b9c547cSRui Paulo int hmac_sha256_kdf(const u8 *secret, size_t secret_len, 335b9c547cSRui Paulo const char *label, const u8 *seed, size_t seed_len, 345b9c547cSRui Paulo u8 *out, size_t outlen) 355b9c547cSRui Paulo { 365b9c547cSRui Paulo u8 T[SHA256_MAC_LEN]; 375b9c547cSRui Paulo u8 iter = 1; 385b9c547cSRui Paulo const unsigned char *addr[4]; 395b9c547cSRui Paulo size_t len[4]; 405b9c547cSRui Paulo size_t pos, clen; 415b9c547cSRui Paulo 425b9c547cSRui Paulo addr[0] = T; 435b9c547cSRui Paulo len[0] = SHA256_MAC_LEN; 44*85732ac8SCy Schubert if (label) { 455b9c547cSRui Paulo addr[1] = (const unsigned char *) label; 465b9c547cSRui Paulo len[1] = os_strlen(label) + 1; 47*85732ac8SCy Schubert } else { 48*85732ac8SCy Schubert addr[1] = (const u8 *) ""; 49*85732ac8SCy Schubert len[1] = 0; 50*85732ac8SCy Schubert } 515b9c547cSRui Paulo addr[2] = seed; 525b9c547cSRui Paulo len[2] = seed_len; 535b9c547cSRui Paulo addr[3] = &iter; 545b9c547cSRui Paulo len[3] = 1; 555b9c547cSRui Paulo 565b9c547cSRui Paulo if (hmac_sha256_vector(secret, secret_len, 3, &addr[1], &len[1], T) < 0) 575b9c547cSRui Paulo return -1; 585b9c547cSRui Paulo 595b9c547cSRui Paulo pos = 0; 605b9c547cSRui Paulo for (;;) { 615b9c547cSRui Paulo clen = outlen - pos; 625b9c547cSRui Paulo if (clen > SHA256_MAC_LEN) 635b9c547cSRui Paulo clen = SHA256_MAC_LEN; 645b9c547cSRui Paulo os_memcpy(out + pos, T, clen); 655b9c547cSRui Paulo pos += clen; 665b9c547cSRui Paulo 675b9c547cSRui Paulo if (pos == outlen) 685b9c547cSRui Paulo break; 695b9c547cSRui Paulo 705b9c547cSRui Paulo if (iter == 255) { 715b9c547cSRui Paulo os_memset(out, 0, outlen); 72325151a3SRui Paulo os_memset(T, 0, SHA256_MAC_LEN); 735b9c547cSRui Paulo return -1; 745b9c547cSRui Paulo } 755b9c547cSRui Paulo iter++; 765b9c547cSRui Paulo 775b9c547cSRui Paulo if (hmac_sha256_vector(secret, secret_len, 4, addr, len, T) < 0) 785b9c547cSRui Paulo { 795b9c547cSRui Paulo os_memset(out, 0, outlen); 80325151a3SRui Paulo os_memset(T, 0, SHA256_MAC_LEN); 815b9c547cSRui Paulo return -1; 825b9c547cSRui Paulo } 835b9c547cSRui Paulo } 845b9c547cSRui Paulo 85325151a3SRui Paulo os_memset(T, 0, SHA256_MAC_LEN); 865b9c547cSRui Paulo return 0; 875b9c547cSRui Paulo } 88