127df3f5dSRui Paulo /* 227df3f5dSRui Paulo * Redistribution and use in source and binary forms, with or without 327df3f5dSRui Paulo * modification, are permitted provided that: (1) source code 427df3f5dSRui Paulo * distributions retain the above copyright notice and this paragraph 527df3f5dSRui Paulo * in its entirety, and (2) distributions including binary code include 627df3f5dSRui Paulo * the above copyright notice and this paragraph in its entirety in 727df3f5dSRui Paulo * the documentation or other materials provided with the distribution. 827df3f5dSRui Paulo * THIS SOFTWARE IS PROVIDED ``AS IS'' AND 927df3f5dSRui Paulo * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT 1027df3f5dSRui Paulo * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 1127df3f5dSRui Paulo * FOR A PARTICULAR PURPOSE. 1227df3f5dSRui Paulo * 1327df3f5dSRui Paulo * Functions for signature and digest verification. 1427df3f5dSRui Paulo * 1527df3f5dSRui Paulo * Original code by Hannes Gredler (hannes@juniper.net) 1627df3f5dSRui Paulo */ 1727df3f5dSRui Paulo 18*3c602fabSXin LI #define NETDISSECT_REWORKED 1927df3f5dSRui Paulo #ifdef HAVE_CONFIG_H 2027df3f5dSRui Paulo #include "config.h" 2127df3f5dSRui Paulo #endif 2227df3f5dSRui Paulo 2327df3f5dSRui Paulo #include <tcpdump-stdinc.h> 2427df3f5dSRui Paulo 2527df3f5dSRui Paulo #include <string.h> 2627df3f5dSRui Paulo 2727df3f5dSRui Paulo #include "interface.h" 2827df3f5dSRui Paulo #include "signature.h" 2927df3f5dSRui Paulo 3027df3f5dSRui Paulo #ifdef HAVE_LIBCRYPTO 3127df3f5dSRui Paulo #include <openssl/md5.h> 3227df3f5dSRui Paulo #endif 3327df3f5dSRui Paulo 3427df3f5dSRui Paulo const struct tok signature_check_values[] = { 3527df3f5dSRui Paulo { SIGNATURE_VALID, "valid"}, 3627df3f5dSRui Paulo { SIGNATURE_INVALID, "invalid"}, 3727df3f5dSRui Paulo { CANT_CHECK_SIGNATURE, "unchecked"}, 3827df3f5dSRui Paulo { 0, NULL } 3927df3f5dSRui Paulo }; 4027df3f5dSRui Paulo 4127df3f5dSRui Paulo 4227df3f5dSRui Paulo #ifdef HAVE_LIBCRYPTO 4327df3f5dSRui Paulo /* 4427df3f5dSRui Paulo * Compute a HMAC MD5 sum. 4527df3f5dSRui Paulo * Taken from rfc2104, Appendix. 4627df3f5dSRui Paulo */ 47*3c602fabSXin LI USES_APPLE_DEPRECATED_API 4827df3f5dSRui Paulo static void 49*3c602fabSXin LI signature_compute_hmac_md5(const uint8_t *text, int text_len, unsigned char *key, 50*3c602fabSXin LI unsigned int key_len, uint8_t *digest) 5127df3f5dSRui Paulo { 5227df3f5dSRui Paulo MD5_CTX context; 5327df3f5dSRui Paulo unsigned char k_ipad[65]; /* inner padding - key XORd with ipad */ 5427df3f5dSRui Paulo unsigned char k_opad[65]; /* outer padding - key XORd with opad */ 5527df3f5dSRui Paulo unsigned char tk[16]; 5627df3f5dSRui Paulo int i; 5727df3f5dSRui Paulo 5827df3f5dSRui Paulo /* if key is longer than 64 bytes reset it to key=MD5(key) */ 5927df3f5dSRui Paulo if (key_len > 64) { 6027df3f5dSRui Paulo 6127df3f5dSRui Paulo MD5_CTX tctx; 6227df3f5dSRui Paulo 6327df3f5dSRui Paulo MD5_Init(&tctx); 6427df3f5dSRui Paulo MD5_Update(&tctx, key, key_len); 6527df3f5dSRui Paulo MD5_Final(tk, &tctx); 6627df3f5dSRui Paulo 6727df3f5dSRui Paulo key = tk; 6827df3f5dSRui Paulo key_len = 16; 6927df3f5dSRui Paulo } 7027df3f5dSRui Paulo 7127df3f5dSRui Paulo /* 7227df3f5dSRui Paulo * the HMAC_MD5 transform looks like: 7327df3f5dSRui Paulo * 7427df3f5dSRui Paulo * MD5(K XOR opad, MD5(K XOR ipad, text)) 7527df3f5dSRui Paulo * 7627df3f5dSRui Paulo * where K is an n byte key 7727df3f5dSRui Paulo * ipad is the byte 0x36 repeated 64 times 7827df3f5dSRui Paulo * opad is the byte 0x5c repeated 64 times 7927df3f5dSRui Paulo * and text is the data being protected 8027df3f5dSRui Paulo */ 8127df3f5dSRui Paulo 8227df3f5dSRui Paulo /* start out by storing key in pads */ 8327df3f5dSRui Paulo memset(k_ipad, 0, sizeof k_ipad); 8427df3f5dSRui Paulo memset(k_opad, 0, sizeof k_opad); 8527df3f5dSRui Paulo memcpy(k_ipad, key, key_len); 8627df3f5dSRui Paulo memcpy(k_opad, key, key_len); 8727df3f5dSRui Paulo 8827df3f5dSRui Paulo /* XOR key with ipad and opad values */ 8927df3f5dSRui Paulo for (i=0; i<64; i++) { 9027df3f5dSRui Paulo k_ipad[i] ^= 0x36; 9127df3f5dSRui Paulo k_opad[i] ^= 0x5c; 9227df3f5dSRui Paulo } 9327df3f5dSRui Paulo 9427df3f5dSRui Paulo /* 9527df3f5dSRui Paulo * perform inner MD5 9627df3f5dSRui Paulo */ 9727df3f5dSRui Paulo MD5_Init(&context); /* init context for 1st pass */ 9827df3f5dSRui Paulo MD5_Update(&context, k_ipad, 64); /* start with inner pad */ 9927df3f5dSRui Paulo MD5_Update(&context, text, text_len); /* then text of datagram */ 10027df3f5dSRui Paulo MD5_Final(digest, &context); /* finish up 1st pass */ 10127df3f5dSRui Paulo 10227df3f5dSRui Paulo /* 10327df3f5dSRui Paulo * perform outer MD5 10427df3f5dSRui Paulo */ 10527df3f5dSRui Paulo MD5_Init(&context); /* init context for 2nd pass */ 10627df3f5dSRui Paulo MD5_Update(&context, k_opad, 64); /* start with outer pad */ 10727df3f5dSRui Paulo MD5_Update(&context, digest, 16); /* then results of 1st hash */ 10827df3f5dSRui Paulo MD5_Final(digest, &context); /* finish up 2nd pass */ 10927df3f5dSRui Paulo } 110*3c602fabSXin LI USES_APPLE_RST 11127df3f5dSRui Paulo #endif 11227df3f5dSRui Paulo 11327df3f5dSRui Paulo #ifdef HAVE_LIBCRYPTO 11427df3f5dSRui Paulo /* 11527df3f5dSRui Paulo * Verify a cryptographic signature of the packet. 11627df3f5dSRui Paulo * Currently only MD5 is supported. 11727df3f5dSRui Paulo */ 11827df3f5dSRui Paulo int 119*3c602fabSXin LI signature_verify(netdissect_options *ndo, 120*3c602fabSXin LI const u_char *pptr, u_int plen, u_char *sig_ptr) 12127df3f5dSRui Paulo { 122*3c602fabSXin LI uint8_t rcvsig[16]; 123*3c602fabSXin LI uint8_t sig[16]; 12427df3f5dSRui Paulo unsigned int i; 12527df3f5dSRui Paulo 12627df3f5dSRui Paulo /* 12727df3f5dSRui Paulo * Save the signature before clearing it. 12827df3f5dSRui Paulo */ 12927df3f5dSRui Paulo memcpy(rcvsig, sig_ptr, sizeof(rcvsig)); 13027df3f5dSRui Paulo memset(sig_ptr, 0, sizeof(rcvsig)); 13127df3f5dSRui Paulo 132*3c602fabSXin LI if (!ndo->ndo_sigsecret) { 13327df3f5dSRui Paulo return (CANT_CHECK_SIGNATURE); 13427df3f5dSRui Paulo } 13527df3f5dSRui Paulo 136*3c602fabSXin LI signature_compute_hmac_md5(pptr, plen, (unsigned char *)ndo->ndo_sigsecret, 137*3c602fabSXin LI strlen(ndo->ndo_sigsecret), sig); 13827df3f5dSRui Paulo 13927df3f5dSRui Paulo if (memcmp(rcvsig, sig, sizeof(sig)) == 0) { 14027df3f5dSRui Paulo return (SIGNATURE_VALID); 14127df3f5dSRui Paulo 14227df3f5dSRui Paulo } else { 14327df3f5dSRui Paulo 14427df3f5dSRui Paulo for (i = 0; i < sizeof(sig); ++i) { 145*3c602fabSXin LI ND_PRINT((ndo, "%02x", sig[i])); 14627df3f5dSRui Paulo } 14727df3f5dSRui Paulo 14827df3f5dSRui Paulo return (SIGNATURE_INVALID); 14927df3f5dSRui Paulo } 15027df3f5dSRui Paulo } 15127df3f5dSRui Paulo #endif 15227df3f5dSRui Paulo 15327df3f5dSRui Paulo /* 15427df3f5dSRui Paulo * Local Variables: 15527df3f5dSRui Paulo * c-style: whitesmith 15627df3f5dSRui Paulo * c-basic-offset: 4 15727df3f5dSRui Paulo * End: 15827df3f5dSRui Paulo */ 159