kdf: add key derivation functions
generic sha code from git://w1.fi/hostap.git commit
5ea93947ca67ba83529798b806a15b247cdb2e93 which also happens
to be the source of our milenage code.
Related: SYS#5324
Change-Id: Ibf2e49edada944d91ceba62bd0d6b6ce69261fcd
diff --git a/src/gsm/kdf/sha256.c b/src/gsm/kdf/sha256.c
new file mode 100644
index 0000000..4f8b6cc
--- /dev/null
+++ b/src/gsm/kdf/sha256.c
@@ -0,0 +1,156 @@
+/*
+ * SHA-256 hash implementation and interface functions
+ * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See README and COPYING for more details.
+ */
+
+
+#include "common.h"
+#include "sha256.h"
+#include "crypto.h"
+
+
+/**
+ * hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104)
+ * @key: Key for HMAC operations
+ * @key_len: Length of the key in bytes
+ * @num_elem: Number of elements in the data vector
+ * @addr: Pointers to the data areas
+ * @len: Lengths of the data blocks
+ * @mac: Buffer for the hash (32 bytes)
+ */
+void hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem,
+ const u8 *addr[], const size_t *len, u8 *mac)
+{
+ unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
+ unsigned char tk[32];
+ const u8 *_addr[6];
+ size_t _len[6], i;
+
+ if (num_elem > 5) {
+ /*
+ * Fixed limit on the number of fragments to avoid having to
+ * allocate memory (which could fail).
+ */
+ return;
+ }
+
+ /* if key is longer than 64 bytes reset it to key = SHA256(key) */
+ if (key_len > 64) {
+ sha256_vector(1, &key, &key_len, tk);
+ key = tk;
+ key_len = 32;
+ }
+
+ /* the HMAC_SHA256 transform looks like:
+ *
+ * SHA256(K XOR opad, SHA256(K XOR ipad, text))
+ *
+ * where K is an n byte key
+ * ipad is the byte 0x36 repeated 64 times
+ * opad is the byte 0x5c repeated 64 times
+ * and text is the data being protected */
+
+ /* start out by storing key in ipad */
+ os_memset(k_pad, 0, sizeof(k_pad));
+ os_memcpy(k_pad, key, key_len);
+ /* XOR key with ipad values */
+ for (i = 0; i < 64; i++)
+ k_pad[i] ^= 0x36;
+
+ /* perform inner SHA256 */
+ _addr[0] = k_pad;
+ _len[0] = 64;
+ for (i = 0; i < num_elem; i++) {
+ _addr[i + 1] = addr[i];
+ _len[i + 1] = len[i];
+ }
+ sha256_vector(1 + num_elem, _addr, _len, mac);
+
+ os_memset(k_pad, 0, sizeof(k_pad));
+ os_memcpy(k_pad, key, key_len);
+ /* XOR key with opad values */
+ for (i = 0; i < 64; i++)
+ k_pad[i] ^= 0x5c;
+
+ /* perform outer SHA256 */
+ _addr[0] = k_pad;
+ _len[0] = 64;
+ _addr[1] = mac;
+ _len[1] = SHA256_MAC_LEN;
+ sha256_vector(2, _addr, _len, mac);
+}
+
+
+/**
+ * hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104)
+ * @key: Key for HMAC operations
+ * @key_len: Length of the key in bytes
+ * @data: Pointers to the data area
+ * @data_len: Length of the data area
+ * @mac: Buffer for the hash (20 bytes)
+ */
+void hmac_sha256(const u8 *key, size_t key_len, const u8 *data,
+ size_t data_len, u8 *mac)
+{
+ hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac);
+}
+
+
+/**
+ * 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
+ *
+ * This function is used to derive new, cryptographically separate keys from a
+ * given key.
+ */
+void 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)
+{
+ 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];
+
+ 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 * 8);
+ pos = 0;
+ while (pos < buf_len) {
+ plen = buf_len - pos;
+ WPA_PUT_LE16(counter_le, counter);
+ if (plen >= SHA256_MAC_LEN) {
+ hmac_sha256_vector(key, key_len, 4, addr, len,
+ &buf[pos]);
+ pos += SHA256_MAC_LEN;
+ } else {
+ hmac_sha256_vector(key, key_len, 4, addr, len, hash);
+ os_memcpy(&buf[pos], hash, plen);
+ break;
+ }
+ counter++;
+ }
+}