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HMAC source code

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/* * hmac.c For the sake of illustration we provide the following * sample code for the implementation of HMAC-MD5 as well * as some corresponding test vectors (the code is based * on MD5 code as described in [MD5]). * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA * * Copyright 2000 The FreeRADIUS server project */ /* ** Function: hmac_md5 */ #include #include "md5.h" #include "libradius.h" /* unsigned char* text; pointer to data stream int text_len; length of data stream unsigned char* key; pointer to authentication key int key_len; length of authentication key unsigned char* digest; caller digest to be filled in */ void lrad_hmac_md5(const unsigned char *text, int text_len, const unsigned char *key, int key_len, unsigned char *digest) { MD5_CTX context; unsigned char k_ipad[65]; /* inner padding - * key XORd with ipad */ unsigned char k_opad[65]; /* outer padding - * key XORd with opad */ unsigned char tk[16]; int i; /* if key is longer than 64 bytes reset it to key=MD5(key) */ if (key_len > 64) { MD5_CTX tctx; MD5Init(&tctx); MD5Update(&tctx, key, key_len); MD5Final(tk, &tctx); key = tk; key_len = 16; } /* * the HMAC_MD5 transform looks like: * * MD5(K XOR opad, MD5(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 pads */ memset( k_ipad, 0, sizeof(k_ipad)); memset( k_opad, 0, sizeof(k_opad)); memcpy( k_ipad, key, key_len); memcpy( k_opad, key, key_len); /* XOR key with ipad and opad values */ for (i = 0; i < 64; i++) { k_ipad[i] ^= 0x36; k_opad[i] ^= 0x5c; } /* * perform inner MD5 */ MD5Init(&context); /* init context for 1st * pass */ MD5Update(&context, k_ipad, 64); /* start with inner pad */ MD5Update(&context, text, text_len); /* then text of datagram */ MD5Final(digest, &context); /* finish up 1st pass */ /* * perform outer MD5 */ MD5Init(&context); /* init context for 2nd * pass */ MD5Update(&context, k_opad, 64); /* start with outer pad */ MD5Update(&context, digest, 16); /* then results of 1st * hash */ MD5Final(digest, &context); /* finish up 2nd pass */ } /* Test Vectors (Trailing '\0' of a character string not included in test): key = 0x0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b key_len = 16 bytes data = "Hi There" data_len = 8 bytes digest = 0x9294727a3638bb1c13f48ef8158bfc9d key = "Jefe" data = "what do ya want for nothing?" data_len = 28 bytes digest = 0x750c783e6ab0b503eaa86e310a5db738 key = 0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA key_len 16 bytes data = 0xDDDDDDDDDDDDDDDDDDDD... ..DDDDDDDDDDDDDDDDDDDD... ..DDDDDDDDDDDDDDDDDDDD... ..DDDDDDDDDDDDDDDDDDDD... ..DDDDDDDDDDDDDDDDDDDD data_len = 50 bytes digest = 0x56be34521d144c88dbb8c733f0e8b3f6 */ #ifdef TESTING /* * cc -DTESTING -I ../include/ hmac.c md5.c -o hmac * * ./hmac Jefe "what do ya want for nothing?" */ #include #include int main(int argc, char **argv) { unsigned char digest[16]; char *key; int key_len; char *text; int text_len; int i; key = argv[1]; key_len = strlen(key); text = argv[2]; text_len = strlen(text); lrad_hmac_md5(text, text_len, key, key_len, digest); for (i = 0; i < 16; i++) { printf("%02x", digest[i]); } printf("\n"); exit(0); return 0; } #endif

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