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      1 /*
      2  * SHA1-based PRF
      3  * Copyright (c) 2003-2005, Jouni Malinen <j (at) w1.fi>
      4  *
      5  * This software may be distributed under the terms of the BSD license.
      6  * See README for more details.
      7  */
      8 
      9 #include "includes.h"
     10 
     11 #include "common.h"
     12 #include "sha1.h"
     13 #include "crypto.h"
     14 
     15 
     16 /**
     17  * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
     18  * @key: Key for PRF
     19  * @key_len: Length of the key in bytes
     20  * @label: A unique label for each purpose of the PRF
     21  * @data: Extra data to bind into the key
     22  * @data_len: Length of the data
     23  * @buf: Buffer for the generated pseudo-random key
     24  * @buf_len: Number of bytes of key to generate
     25  * Returns: 0 on success, -1 of failure
     26  *
     27  * This function is used to derive new, cryptographically separate keys from a
     28  * given key (e.g., PMK in IEEE 802.11i).
     29  */
     30 int sha1_prf(const u8 *key, size_t key_len, const char *label,
     31 	     const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
     32 {
     33 	u8 counter = 0;
     34 	size_t pos, plen;
     35 	u8 hash[SHA1_MAC_LEN];
     36 	size_t label_len = os_strlen(label) + 1;
     37 	const unsigned char *addr[3];
     38 	size_t len[3];
     39 
     40 	addr[0] = (u8 *) label;
     41 	len[0] = label_len;
     42 	addr[1] = data;
     43 	len[1] = data_len;
     44 	addr[2] = &counter;
     45 	len[2] = 1;
     46 
     47 	pos = 0;
     48 	while (pos < buf_len) {
     49 		plen = buf_len - pos;
     50 		if (plen >= SHA1_MAC_LEN) {
     51 			if (hmac_sha1_vector(key, key_len, 3, addr, len,
     52 					     &buf[pos]))
     53 				return -1;
     54 			pos += SHA1_MAC_LEN;
     55 		} else {
     56 			if (hmac_sha1_vector(key, key_len, 3, addr, len,
     57 					     hash))
     58 				return -1;
     59 			os_memcpy(&buf[pos], hash, plen);
     60 			break;
     61 		}
     62 		counter++;
     63 	}
     64 
     65 	return 0;
     66 }
     67