xref: /openbsd/usr.sbin/tcpdump/print-ipsec.c (revision 5dea098c) 
1 /*	$OpenBSD: print-ipsec.c,v 1.27 2021/11/29 18:50:16 tb Exp $	*/
2 
3 /*
4  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999
5  *      The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that: (1) source code distributions
9  * retain the above copyright notice and this paragraph in its entirety, (2)
10  * distributions including binary code include the above copyright notice and
11  * this paragraph in its entirety in the documentation or other materials
12  * provided with the distribution, and (3) all advertising materials mentioning
13  * features or use of this software display the following acknowledgement:
14  * ``This product includes software developed by the University of California,
15  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
16  * the University nor the names of its contributors may be used to endorse
17  * or promote products derived from this software without specific prior
18  * written permission.
19  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
20  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
21  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
22  *
23  * Format and print IPsec (ESP/AH) packets.
24  *      By Tero Kivinen <kivinen@ssh.fi>, Tero Mononen <tmo@ssh.fi>,
25  *         Tatu Ylonen <ylo@ssh.fi> and Timo J. Rinne <tri@ssh.fi>
26  *         in co-operation with SSH Communications Security, Espoo, Finland
27  */
28 
29 #include <sys/time.h>
30 #include <sys/socket.h>
31 
32 #include <netinet/in.h>
33 #include <netinet/ip.h>
34 #include <netinet/ip6.h>
35 #include <netinet/ip_var.h>
36 #include <netinet/udp.h>
37 #include <netinet/udp_var.h>
38 #include <netinet/tcp.h>
39 
40 #include <stdio.h>
41 #include <stdlib.h>
42 #include <string.h>
43 #include <unistd.h>
44 
45 #include "addrtoname.h"
46 #include "interface.h"
47 #include "extract.h"		    /* must come after interface.h */
48 
49 #include <openssl/evp.h>
50 #include <ctype.h>
51 
52 /*
53  * IPsec/ESP header
54  */
55 struct esp_hdr {
56 	u_int esp_spi;
57 	u_int esp_seq;
58 };
59 
60 static int espinit = 0;
61 static int espauthlen = 12;
62 static EVP_CIPHER_CTX *ctx;
63 
64 int
65 esp_init (char *espspec)
66 {
67 	const EVP_CIPHER *evp;
68 	char *p, *espkey, s[3], name[1024];
69 	u_char *key;
70 	int i, klen, len;
71 
72 	evp = EVP_aes_128_cbc();	/* default */
73 	espkey = espspec;
74 	if ((p = strchr(espspec, ':')) != NULL) {
75 		len = p - espspec;
76 		if (len >= sizeof(name))
77 			error("espalg too long");
78 		memcpy(name, espspec, len);
79 		name[len] = '\0';
80 		espkey = p + 1;
81 
82 		/* strip auth alg */
83 		espauthlen = 0;
84 		if ((p = strstr(name, "-hmac96")) != NULL) {
85 			espauthlen = 12;
86 			*p = '\0';
87 		}
88 		OpenSSL_add_all_algorithms();
89 		if ((evp = EVP_get_cipherbyname(name)) == NULL)
90 			error("espalg `%s' not supported", name);
91 	}
92 	klen = EVP_CIPHER_key_length(evp);
93 	if (strlen(espkey) != klen * 2)
94 		error("espkey size mismatch, %d bytes needed", klen);
95 	if ((key = malloc(klen)) == NULL)
96 		error("malloc failed");
97 	for (i = 0; i < klen; i++) {
98 		s[0] = espkey[2*i];
99 		s[1] = espkey[2*i + 1];
100 		s[2] = 0;
101 		if (!isxdigit((unsigned char)s[0]) ||
102 		    !isxdigit((unsigned char)s[1])) {
103 			free(key);
104 			error("espkey must be specified in hex");
105 		}
106 		key[i] = strtoul(s, NULL, 16);
107 	}
108 	if ((ctx = EVP_CIPHER_CTX_new()) == NULL) {
109 		free(key);
110 		error("espkey init failed");
111 	}
112 	if (!EVP_CipherInit(ctx, evp, key, NULL, 0)) {
113 		EVP_CIPHER_CTX_free(ctx);
114 		free(key);
115 		error("espkey init failed");
116 	}
117 	free(key);
118 	espinit = 1;
119 	return (0);
120 }
121 
122 void
123 esp_decrypt (const u_char *bp, u_int len, const u_char *bp2)
124 {
125 	const struct ip *ip;
126 	u_char *data, pad, nh;
127 	int blocksz;
128 
129 	ip = (const struct ip *)bp2;
130 
131 	blocksz = EVP_CIPHER_CTX_block_size(ctx);
132 
133 	/* Skip fragments and short packets */
134 	if (ntohs(ip->ip_off) & 0x3fff)
135 		return;
136 	if (snapend - bp < len) {
137 		printf(" [|esp]");
138 		return;
139 	}
140 	/*
141 	 * Skip ESP header and ignore authentication trailer.
142 	 * For decryption we need at least 2 blocks: IV and
143 	 * one cipher block.
144 	 */
145 	if (len < sizeof(struct esp_hdr) + espauthlen + 2 * blocksz) {
146 		printf(" [|esp]");
147 		return;
148 	}
149 
150 	data = (char *)bp;
151 	data += sizeof(struct esp_hdr);
152 	len -= sizeof(struct esp_hdr);
153 	len -= espauthlen;
154 
155 	/* the first block contains the IV */
156 	if (!EVP_CipherInit(ctx, NULL, NULL, data, 0))
157 		return;
158 
159 	len -= blocksz;
160 	data += blocksz;
161 
162 	/* decrypt remaining payload */
163 	if (!EVP_Cipher(ctx, data, data, len))
164 		return;
165 
166 	nh = data[len - 1];
167 	pad = data[len - 2];
168 
169 	/* verify padding */
170 	if (pad + 2 > len)
171 		return;
172 	if (data[len - 3]  != pad)
173 		return;
174 	if (vflag > 1)
175 		printf(" pad %d", pad);
176 	len -= (pad + 2);
177 	printf(": ");
178 	switch (nh) {
179 	case IPPROTO_TCP:
180 		tcp_print(data, len, bp2);
181 		break;
182 	case IPPROTO_UDP:
183 		udp_print(data, len, bp2);
184 		break;
185 	case IPPROTO_IPV6:
186 		ip6_print(data, len);
187 		break;
188 	case IPPROTO_IPV4:
189 		ip_print(data, len);
190 		break;
191 	case IPPROTO_ICMP:
192 		icmp_print(data, len, bp2);
193 		break;
194 	case IPPROTO_ICMPV6:
195 		icmp6_print(data, len, bp2);
196 		break;
197 	default:
198 		printf("ip-proto-%d %d", nh, len);
199 		break;
200 	}
201 	if (vflag)
202 		printf(" (esp)");
203 }
204 
205 void
206 esp_print (const u_char *bp, u_int len, const u_char *bp2)
207 {
208 	const struct esp_hdr *esp;
209 
210 	if (len < sizeof(struct esp_hdr)) {
211 		printf("[|esp]");
212 		return;
213 	}
214 	esp = (const struct esp_hdr *)bp;
215 
216 	printf("esp spi 0x%08x seq %u len %d",
217 	    ntohl(esp->esp_spi), ntohl(esp->esp_seq), len);
218 
219 	if (espinit)
220 		esp_decrypt(bp, len, bp2);
221 }
222 
223 /*
224  * IPsec/AH header
225  */
226 struct ah_hdr {
227 	u_char  ah_nxt_hdr;
228 	u_char  ah_pl_len;
229 	u_short ah_reserved;
230 	u_int   ah_spi;
231 	u_int   ah_seq;
232 };
233 
234 void
235 ah_print (const u_char *bp, u_int len, const u_char *bp2)
236 {
237 	const struct ip *ip;
238 	const struct ah_hdr *ah;
239 	u_int pl_len = len;
240 	const struct ip6_hdr *ip6;
241 
242 	ip = (const struct ip *)bp2;
243 	if (ip->ip_v == 6) {
244 		ip6 = (const struct ip6_hdr *)bp2;
245 		printf("ah %s > %s", ip6addr_string(&ip6->ip6_src),
246 		    ip6addr_string(&ip6->ip6_dst));
247 	} else
248 		printf("ah %s > %s",
249 	    	    ipaddr_string(&ip->ip_src), ipaddr_string(&ip->ip_dst));
250 
251 	if (pl_len < sizeof(struct ah_hdr)) {
252 		printf("[|ah]");
253 		return;
254 	}
255 	ah = (const struct ah_hdr *)bp;
256 
257 	printf(" spi 0x%08x seq %u len %d",
258 	    ntohl(ah->ah_spi), ntohl(ah->ah_seq), len);
259 
260 	if (vflag) {
261 	        printf(" [ ");
262 
263 	        pl_len = (ah->ah_pl_len + 2) << 2; /* RFC2402, sec 2.2 */
264 
265 		if (len <= pl_len) {
266 		        printf("truncated");
267 			goto out;
268 		}
269 
270 		switch (ah->ah_nxt_hdr) {
271 
272 		case IPPROTO_IPIP: /* Tunnel Mode, IP-in-IP */
273 		        ip_print(bp + pl_len, len - pl_len);
274 			break;
275 
276 	        case IPPROTO_ICMP: /* From here and down; Transport mode */
277 		        icmp_print(bp + pl_len, len - pl_len,
278 				  (const u_char *) ip);
279 			break;
280 
281 	        case IPPROTO_ICMPV6:
282 		        icmp6_print(bp + pl_len, len - pl_len,
283 				  (const u_char *) ip);
284 			break;
285 
286 	        case IPPROTO_TCP:
287 		        tcp_print(bp + pl_len, len - pl_len,
288 				  (const u_char *) ip);
289 			break;
290 
291 	        case IPPROTO_UDP:
292 		        udp_print(bp + pl_len, len - pl_len,
293 				  (const u_char *) ip);
294 			break;
295 
296 		case IPPROTO_ESP:
297 		        esp_print(bp + pl_len, len - pl_len,
298 				  (const u_char *) ip);
299 			break;
300 
301 		case IPPROTO_AH:
302 		        ah_print(bp + pl_len, len - pl_len,
303 				 (const u_char *) ip);
304 			break;
305 
306 		default:
307 		        printf("ip-proto-%d len %d",
308 			    ah->ah_nxt_hdr, len - pl_len);
309 		}
310 out:
311 		printf(" ]");
312 	}
313 
314 }
315 
316 struct ipcomp_hdr {
317 	u_char  ipcomp_nxt_hdr;
318 	u_char	ipcomp_flags;
319 	u_short	ipcomp_cpi;
320 };
321 
322 void
323 ipcomp_print (const u_char *bp, u_int len, const u_char *bp2)
324 {
325 	const struct ip *ip;
326 	const struct ipcomp_hdr *ipc;
327 	u_int plen = len;
328 
329 	ip = (const struct ip *)bp2;
330 
331 	printf("ipcomp %s > %s",
332 	    ipaddr_string(&ip->ip_src),
333 	    ipaddr_string(&ip->ip_dst));
334 
335 	if (plen < sizeof(struct ipcomp_hdr)) {
336 		printf("[|ipcomp]");
337 		return;
338 	}
339 	ipc = (const struct ipcomp_hdr *)bp;
340 
341 	printf(" cpi 0x%04X flags %x next %x",
342 	    ntohs(ipc->ipcomp_cpi), ipc->ipcomp_flags, ipc->ipcomp_nxt_hdr);
343 }
344