components/wpa_supplicant/src/crypto/sha256-tlsprf.c (ESP-IDF)

/* * TLS PRF P_SHA256 * Copyright (c) 2011, Jouni Malinen <j@w1.fi> * * This software may be distributed under the terms of the BSD license. * See README for more details. */ #include "includes.h" #include "common.h" #include "sha256.h" /** * tls_prf_sha256 - Pseudo-Random Function for TLS v1.2 (P_SHA256, RFC 5246) * @secret: Key for PRF * @secret_len: Length of the key in bytes * @label: A unique label for each purpose of the PRF * @seed: Seed value to bind into the key * @seed_len: Length of the seed * @out: Buffer for the generated pseudo-random key * @outlen: Number of bytes of key to generate * Returns: 0 on success, -1 on failure. * * This function is used to derive new, cryptographically separate keys from a * given key in TLS. This PRF is defined in RFC 2246, Chapter 5. */ int tls_prf_sha256(const u8 *secret, size_t secret_len, const char *label, const u8 *seed, size_t seed_len, u8 *out, size_t outlen) { size_t clen; u8 A[SHA256_MAC_LEN]; u8 P[SHA256_MAC_LEN]; size_t pos; const unsigned char *addr[3]; size_t len[3]; addr[0] = A; len[0] = SHA256_MAC_LEN; addr[1] = (unsigned char *) label; len[1] = os_strlen(label); addr[2] = seed; len[2] = seed_len; /* * RFC 5246, Chapter 5 * A(0) = seed, A(i) = HMAC(secret, A(i-1)) * P_hash = HMAC(secret, A(1) + seed) + HMAC(secret, A(2) + seed) + .. * PRF(secret, label, seed) = P_SHA256(secret, label + seed) */ if (hmac_sha256_vector(secret, secret_len, 2, &addr[1], &len[1], A) < 0) return -1; pos = 0; while (pos < outlen) { if (hmac_sha256_vector(secret, secret_len, 3, addr, len, P) < 0 || hmac_sha256(secret, secret_len, A, SHA256_MAC_LEN, A) < 0) return -1; clen = outlen - pos; if (clen > SHA256_MAC_LEN) clen = SHA256_MAC_LEN; os_memcpy(out + pos, P, clen); pos += clen; } return 0; }