diff --git a/src/crypto/sha256-kdf.c b/src/crypto/sha256-kdf.c new file mode 100644 index 000000000..d8a1beb32 --- /dev/null +++ b/src/crypto/sha256-kdf.c @@ -0,0 +1,76 @@ +/* + * HMAC-SHA256 KDF (RFC 5295) + * Copyright (c) 2014, Jouni Malinen + * + * 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" + + +/** + * hmac_sha256_kdf - HMAC-SHA256 based KDF (RFC 5295) + * @secret: Key for KDF + * @secret_len: Length of the key in bytes + * @label: A unique label for each purpose of the KDF + * @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 ERP. This KDF is defined in RFC 5295, Chapter 3.1.2. + */ +int hmac_sha256_kdf(const u8 *secret, size_t secret_len, + const char *label, const u8 *seed, size_t seed_len, + u8 *out, size_t outlen) +{ + u8 T[SHA256_MAC_LEN]; + u8 iter = 1; + const unsigned char *addr[4]; + size_t len[4]; + size_t pos, clen; + + addr[0] = T; + len[0] = SHA256_MAC_LEN; + addr[1] = (const unsigned char *) label; + len[1] = os_strlen(label) + 1; + addr[2] = seed; + len[2] = seed_len; + addr[3] = &iter; + len[3] = 1; + + if (hmac_sha256_vector(secret, secret_len, 3, &addr[1], &len[1], T) < 0) + return -1; + + pos = 0; + for (;;) { + clen = outlen - pos; + if (clen > SHA256_MAC_LEN) + clen = SHA256_MAC_LEN; + os_memcpy(out + pos, T, clen); + pos += clen; + + if (pos == outlen) + break; + + if (iter == 255) { + os_memset(out, 0, outlen); + return -1; + } + iter++; + + if (hmac_sha256_vector(secret, secret_len, 4, addr, len, T) < 0) + { + os_memset(out, 0, outlen); + return -1; + } + } + + return 0; +} diff --git a/src/crypto/sha256.h b/src/crypto/sha256.h index 7596a5221..b15f51158 100644 --- a/src/crypto/sha256.h +++ b/src/crypto/sha256.h @@ -1,6 +1,6 @@ /* * SHA256 hash implementation and interface functions - * Copyright (c) 2003-2013, Jouni Malinen + * Copyright (c) 2003-2014, Jouni Malinen * * This software may be distributed under the terms of the BSD license. * See README for more details. @@ -23,5 +23,8 @@ void sha256_prf_bits(const u8 *key, size_t key_len, const char *label, void 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); +int hmac_sha256_kdf(const u8 *secret, size_t secret_len, + const char *label, const u8 *seed, size_t seed_len, + u8 *out, size_t outlen); #endif /* SHA256_H */