ESP-IDF
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Outline
#include "includes.h"
#include "common.h"
#include "sha256.h"
#include "crypto.h"
sha256_prf(const u8 *, size_t, const char *, const u8 *, size_t, u8 *, size_t)
sha256_prf_bits(const u8 *, size_t, const char *, const u8 *, size_t, u8 *, size_t)
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SourceVuESP-IDF Framework and ExamplesESP-IDFcomponents/wpa_supplicant/src/crypto/sha256-prf.c
 
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/* * SHA256-based PRF (IEEE 802.11r) * Copyright (c) 2003-2016, 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" #include "crypto.h" /** * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2) * @key: Key for PRF * @key_len: Length of the key in bytes * @label: A unique label for each purpose of the PRF * @data: Extra data to bind into the key * @data_len: Length of the data * @buf: Buffer for the generated pseudo-random key * @buf_len: 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. *//* ... */ int sha256_prf(const u8 *key, size_t key_len, const char *label, const u8 *data, size_t data_len, u8 *buf, size_t buf_len) { return sha256_prf_bits(key, key_len, label, data, data_len, buf, buf_len * 8); }{ ... } /** * sha256_prf_bits - IEEE Std 802.11-2012, 11.6.1.7.2 Key derivation function * @key: Key for KDF * @key_len: Length of the key in bytes * @label: A unique label for each purpose of the PRF * @data: Extra data to bind into the key * @data_len: Length of the data * @buf: Buffer for the generated pseudo-random key * @buf_len: Number of bits 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. If the requested buf_len is not divisible by eight, the least * significant 1-7 bits of the last octet in the output are not part of the * requested output. *//* ... */ int sha256_prf_bits(const u8 *key, size_t key_len, const char *label, const u8 *data, size_t data_len, u8 *buf, size_t buf_len_bits) { u16 counter = 1; size_t pos, plen; u8 hash[SHA256_MAC_LEN]; const u8 *addr[4]; size_t len[4]; u8 counter_le[2], length_le[2]; size_t buf_len = (buf_len_bits + 7) / 8; addr[0] = counter_le; len[0] = 2; addr[1] = (u8 *) label; len[1] = os_strlen(label); addr[2] = data; len[2] = data_len; addr[3] = length_le; len[3] = sizeof(length_le); WPA_PUT_LE16(length_le, buf_len_bits); pos = 0; while (pos < buf_len) { plen = buf_len - pos; WPA_PUT_LE16(counter_le, counter); if (plen >= SHA256_MAC_LEN) { if (hmac_sha256_vector(key, key_len, 4, addr, len, &buf[pos]) < 0) return -1; pos += SHA256_MAC_LEN; }{...} else { if (hmac_sha256_vector(key, key_len, 4, addr, len, hash) < 0) return -1; os_memcpy(&buf[pos], hash, plen); pos += plen; break; }{...} counter++; }{...} /* * Mask out unused bits in the last octet if it does not use all the * bits. *//* ... */ if (buf_len_bits % 8) { u8 mask = 0xff << (8 - buf_len_bits % 8); buf[pos - 1] &= mask; }{...} forced_memzero(hash, sizeof(hash)); return 0; }{ ... }
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