nexmon – Blame information for rev 1

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1 office 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 #define NETDISSECT_REWORKED
19 #ifdef HAVE_CONFIG_H
20 #include "config.h"
21 #endif
22  
23 #include <tcpdump-stdinc.h>
24  
25 #include <string.h>
26  
27 #include "interface.h"
28 #include "signature.h"
29  
30 #ifdef HAVE_LIBCRYPTO
31 #include <openssl/md5.h>
32 #endif
33  
34 const struct tok signature_check_values[] = {
35 { SIGNATURE_VALID, "valid"},
36 { SIGNATURE_INVALID, "invalid"},
37 { CANT_CHECK_SIGNATURE, "unchecked"},
38 { 0, NULL }
39 };
40  
41  
42 #ifdef HAVE_LIBCRYPTO
43 /*
44 * Compute a HMAC MD5 sum.
45 * Taken from rfc2104, Appendix.
46 */
47 USES_APPLE_DEPRECATED_API
48 static void
49 signature_compute_hmac_md5(const uint8_t *text, int text_len, unsigned char *key,
50 unsigned int key_len, uint8_t *digest)
51 {
52 MD5_CTX context;
53 unsigned char k_ipad[65]; /* inner padding - key XORd with ipad */
54 unsigned char k_opad[65]; /* outer padding - key XORd with opad */
55 unsigned char tk[16];
56 int i;
57  
58 /* if key is longer than 64 bytes reset it to key=MD5(key) */
59 if (key_len > 64) {
60  
61 MD5_CTX tctx;
62  
63 MD5_Init(&tctx);
64 MD5_Update(&tctx, key, key_len);
65 MD5_Final(tk, &tctx);
66  
67 key = tk;
68 key_len = 16;
69 }
70  
71 /*
72 * the HMAC_MD5 transform looks like:
73 *
74 * MD5(K XOR opad, MD5(K XOR ipad, text))
75 *
76 * where K is an n byte key
77 * ipad is the byte 0x36 repeated 64 times
78 * opad is the byte 0x5c repeated 64 times
79 * and text is the data being protected
80 */
81  
82 /* start out by storing key in pads */
83 memset(k_ipad, 0, sizeof k_ipad);
84 memset(k_opad, 0, sizeof k_opad);
85 memcpy(k_ipad, key, key_len);
86 memcpy(k_opad, key, key_len);
87  
88 /* XOR key with ipad and opad values */
89 for (i=0; i<64; i++) {
90 k_ipad[i] ^= 0x36;
91 k_opad[i] ^= 0x5c;
92 }
93  
94 /*
95 * perform inner MD5
96 */
97 MD5_Init(&context); /* init context for 1st pass */
98 MD5_Update(&context, k_ipad, 64); /* start with inner pad */
99 MD5_Update(&context, text, text_len); /* then text of datagram */
100 MD5_Final(digest, &context); /* finish up 1st pass */
101  
102 /*
103 * perform outer MD5
104 */
105 MD5_Init(&context); /* init context for 2nd pass */
106 MD5_Update(&context, k_opad, 64); /* start with outer pad */
107 MD5_Update(&context, digest, 16); /* then results of 1st hash */
108 MD5_Final(digest, &context); /* finish up 2nd pass */
109 }
110 USES_APPLE_RST
111 #endif
112  
113 #ifdef HAVE_LIBCRYPTO
114 /*
115 * Verify a cryptographic signature of the packet.
116 * Currently only MD5 is supported.
117 */
118 int
119 signature_verify(netdissect_options *ndo,
120 const u_char *pptr, u_int plen, u_char *sig_ptr)
121 {
122 uint8_t rcvsig[16];
123 uint8_t sig[16];
124 unsigned int i;
125  
126 /*
127 * Save the signature before clearing it.
128 */
129 memcpy(rcvsig, sig_ptr, sizeof(rcvsig));
130 memset(sig_ptr, 0, sizeof(rcvsig));
131  
132 if (!ndo->ndo_sigsecret) {
133 return (CANT_CHECK_SIGNATURE);
134 }
135  
136 signature_compute_hmac_md5(pptr, plen, (unsigned char *)ndo->ndo_sigsecret,
137 strlen(ndo->ndo_sigsecret), sig);
138  
139 if (memcmp(rcvsig, sig, sizeof(sig)) == 0) {
140 return (SIGNATURE_VALID);
141  
142 } else {
143  
144 for (i = 0; i < sizeof(sig); ++i) {
145 ND_PRINT((ndo, "%02x", sig[i]));
146 }
147  
148 return (SIGNATURE_INVALID);
149 }
150 }
151 #endif
152  
153 /*
154 * Local Variables:
155 * c-style: whitesmith
156 * c-basic-offset: 4
157 * End:
158 */