JP Abgrall | 53f17a9 | 2014-02-12 14:02:41 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Redistribution and use in source and binary forms, with or without |
| 3 | * modification, are permitted provided that: (1) source code |
| 4 | * distributions retain the above copyright notice and this paragraph |
| 5 | * in its entirety, and (2) distributions including binary code include |
| 6 | * the above copyright notice and this paragraph in its entirety in |
| 7 | * the documentation or other materials provided with the distribution. |
| 8 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND |
| 9 | * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT |
| 10 | * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| 11 | * FOR A PARTICULAR PURPOSE. |
| 12 | * |
| 13 | * Functions for signature and digest verification. |
| 14 | * |
| 15 | * Original code by Hannes Gredler (hannes@juniper.net) |
| 16 | */ |
| 17 | |
| 18 | #ifndef lint |
| 19 | static const char rcsid[] _U_ = |
| 20 | "@(#) $Header: /tcpdump/master/tcpdump/signature.c,v 1.2 2008-09-22 20:22:10 guy Exp $ (LBL)"; |
| 21 | #endif |
| 22 | |
| 23 | #ifdef HAVE_CONFIG_H |
| 24 | #include "config.h" |
| 25 | #endif |
| 26 | |
| 27 | #include <tcpdump-stdinc.h> |
| 28 | |
| 29 | #include <string.h> |
| 30 | |
| 31 | #include "interface.h" |
| 32 | #include "signature.h" |
| 33 | |
| 34 | #ifdef HAVE_LIBCRYPTO |
| 35 | #include <openssl/md5.h> |
| 36 | #endif |
| 37 | |
| 38 | const struct tok signature_check_values[] = { |
| 39 | { SIGNATURE_VALID, "valid"}, |
| 40 | { SIGNATURE_INVALID, "invalid"}, |
| 41 | { CANT_CHECK_SIGNATURE, "unchecked"}, |
| 42 | { 0, NULL } |
| 43 | }; |
| 44 | |
| 45 | |
| 46 | #ifdef HAVE_LIBCRYPTO |
| 47 | /* |
| 48 | * Compute a HMAC MD5 sum. |
| 49 | * Taken from rfc2104, Appendix. |
| 50 | */ |
| 51 | USES_APPLE_DEPRECATED_API |
| 52 | static void |
| 53 | signature_compute_hmac_md5(const u_int8_t *text, int text_len, unsigned char *key, |
| 54 | unsigned int key_len, u_int8_t *digest) |
| 55 | { |
| 56 | MD5_CTX context; |
| 57 | unsigned char k_ipad[65]; /* inner padding - key XORd with ipad */ |
| 58 | unsigned char k_opad[65]; /* outer padding - key XORd with opad */ |
| 59 | unsigned char tk[16]; |
| 60 | int i; |
| 61 | |
| 62 | /* if key is longer than 64 bytes reset it to key=MD5(key) */ |
| 63 | if (key_len > 64) { |
| 64 | |
| 65 | MD5_CTX tctx; |
| 66 | |
| 67 | MD5_Init(&tctx); |
| 68 | MD5_Update(&tctx, key, key_len); |
| 69 | MD5_Final(tk, &tctx); |
| 70 | |
| 71 | key = tk; |
| 72 | key_len = 16; |
| 73 | } |
| 74 | |
| 75 | /* |
| 76 | * the HMAC_MD5 transform looks like: |
| 77 | * |
| 78 | * MD5(K XOR opad, MD5(K XOR ipad, text)) |
| 79 | * |
| 80 | * where K is an n byte key |
| 81 | * ipad is the byte 0x36 repeated 64 times |
| 82 | * opad is the byte 0x5c repeated 64 times |
| 83 | * and text is the data being protected |
| 84 | */ |
| 85 | |
| 86 | /* start out by storing key in pads */ |
| 87 | memset(k_ipad, 0, sizeof k_ipad); |
| 88 | memset(k_opad, 0, sizeof k_opad); |
| 89 | memcpy(k_ipad, key, key_len); |
| 90 | memcpy(k_opad, key, key_len); |
| 91 | |
| 92 | /* XOR key with ipad and opad values */ |
| 93 | for (i=0; i<64; i++) { |
| 94 | k_ipad[i] ^= 0x36; |
| 95 | k_opad[i] ^= 0x5c; |
| 96 | } |
| 97 | |
| 98 | /* |
| 99 | * perform inner MD5 |
| 100 | */ |
| 101 | MD5_Init(&context); /* init context for 1st pass */ |
| 102 | MD5_Update(&context, k_ipad, 64); /* start with inner pad */ |
| 103 | MD5_Update(&context, text, text_len); /* then text of datagram */ |
| 104 | MD5_Final(digest, &context); /* finish up 1st pass */ |
| 105 | |
| 106 | /* |
| 107 | * perform outer MD5 |
| 108 | */ |
| 109 | MD5_Init(&context); /* init context for 2nd pass */ |
| 110 | MD5_Update(&context, k_opad, 64); /* start with outer pad */ |
| 111 | MD5_Update(&context, digest, 16); /* then results of 1st hash */ |
| 112 | MD5_Final(digest, &context); /* finish up 2nd pass */ |
| 113 | } |
| 114 | USES_APPLE_RST |
| 115 | #endif |
| 116 | |
| 117 | #ifdef HAVE_LIBCRYPTO |
| 118 | /* |
| 119 | * Verify a cryptographic signature of the packet. |
| 120 | * Currently only MD5 is supported. |
| 121 | */ |
| 122 | int |
| 123 | signature_verify (const u_char *pptr, u_int plen, u_char *sig_ptr) |
| 124 | { |
| 125 | u_int8_t rcvsig[16]; |
| 126 | u_int8_t sig[16]; |
| 127 | unsigned int i; |
| 128 | |
| 129 | /* |
| 130 | * Save the signature before clearing it. |
| 131 | */ |
| 132 | memcpy(rcvsig, sig_ptr, sizeof(rcvsig)); |
| 133 | memset(sig_ptr, 0, sizeof(rcvsig)); |
| 134 | |
| 135 | if (!sigsecret) { |
| 136 | return (CANT_CHECK_SIGNATURE); |
| 137 | } |
| 138 | |
| 139 | signature_compute_hmac_md5(pptr, plen, (unsigned char *)sigsecret, |
| 140 | strlen(sigsecret), sig); |
| 141 | |
| 142 | if (memcmp(rcvsig, sig, sizeof(sig)) == 0) { |
| 143 | return (SIGNATURE_VALID); |
| 144 | |
| 145 | } else { |
| 146 | |
| 147 | for (i = 0; i < sizeof(sig); ++i) { |
| 148 | (void)printf("%02x", sig[i]); |
| 149 | } |
| 150 | |
| 151 | return (SIGNATURE_INVALID); |
| 152 | } |
| 153 | } |
| 154 | #endif |
| 155 | |
| 156 | /* |
| 157 | * Local Variables: |
| 158 | * c-style: whitesmith |
| 159 | * c-basic-offset: 4 |
| 160 | * End: |
| 161 | */ |