networking.c revision 290001 
1#include <config.h>
2#include "networking.h"
3#include "ntp_debug.h"
4
5
6/* Send a packet */
7int
8sendpkt (
9	SOCKET rsock,
10	sockaddr_u *dest,
11	struct pkt *pkt,
12	int len
13	)
14{
15	int cc;
16
17#ifdef DEBUG
18	if (debug > 2) {
19		printf("sntp sendpkt: Packet data:\n");
20		pkt_output(pkt, len, stdout);
21	}
22#endif
23	TRACE(1, ("sntp sendpkt: Sending packet to %s ...\n",
24		  sptoa(dest)));
25
26	cc = sendto(rsock, (void *)pkt, len, 0, &dest->sa,
27		    SOCKLEN(dest));
28	if (cc == SOCKET_ERROR) {
29		msyslog(LOG_ERR, "Send to %s failed, %m",
30			sptoa(dest));
31		return FALSE;
32	}
33	TRACE(1, ("Packet sent.\n"));
34
35	return TRUE;
36}
37
38
39/* Receive raw data */
40int
41recvdata(
42	SOCKET		rsock,
43	sockaddr_u *	sender,
44	void *		rdata,
45	int		rdata_length
46	)
47{
48	GETSOCKNAME_SOCKLEN_TYPE slen;
49	int recvc;
50
51	slen = sizeof(*sender);
52	recvc = recvfrom(rsock, rdata, rdata_length, 0,
53			 &sender->sa, &slen);
54	if (recvc < 0)
55		return recvc;
56#ifdef DEBUG
57	if (debug > 2) {
58		printf("Received %d bytes from %s:\n", recvc, sptoa(sender));
59		pkt_output((struct pkt *)rdata, recvc, stdout);
60	}
61#endif
62	return recvc;
63}
64
65/* Parsing from a short 'struct pkt' directly is bound to create
66 * coverity warnings. These are hard to avoid, as the formal declaration
67 * does not reflect the true layout in the presence of autokey extension
68 * fields. Parsing and skipping the extension fields of a received packet
69 * until there's only the MAC left is better done in this separate
70 * function.
71 */
72static void*
73skip_efields(
74	u_int32 *head,	/* head of extension chain 	*/
75	u_int32 *tail	/* tail/end of extension chain	*/
76	)
77{
78
79	u_int nlen;	/* next extension length */
80	while ((tail - head) > 6) {
81		nlen = ntohl(*head++) & 0xffff;
82		nlen = (nlen + 3) >> 2;
83		if (nlen > (u_int)(tail - head) || nlen < 4)
84			return NULL;	/* Blooper! Inconsistent! */
85		head += nlen;
86	}
87	return head;
88}
89
90/*
91** Check if it's data for us and whether it's useable or not.
92**
93** If not, return a failure code so we can delete this server from our list
94** and continue with another one.
95*/
96int
97process_pkt (
98	struct pkt *rpkt,
99	sockaddr_u *sender,
100	int pkt_len,
101	int mode,
102	struct pkt *spkt,
103	const char * func_name
104	)
105{
106	u_int		key_id;
107	struct key *	pkt_key;
108	int		is_authentic;
109	int		mac_size;
110	u_int		exten_len;
111	u_int32 *       exten_end;
112	u_int32 *       packet_end;
113	l_fp		sent_xmt;
114	l_fp		resp_org;
115
116	// key_id = 0;
117	pkt_key = NULL;
118	is_authentic = (HAVE_OPT(AUTHENTICATION)) ? 0 : -1;
119
120	/*
121	 * Parse the extension field if present. We figure out whether
122	 * an extension field is present by measuring the MAC size. If
123	 * the number of words following the packet header is 0, no MAC
124	 * is present and the packet is not authenticated. If 1, the
125	 * packet is a crypto-NAK; if 3, the packet is authenticated
126	 * with DES; if 5, the packet is authenticated with MD5; if 6,
127	 * the packet is authenticated with SHA. If 2 or 4, the packet
128	 * is a runt and discarded forthwith. If greater than 6, an
129	 * extension field is present, so we subtract the length of the
130	 * field and go around again.
131	 */
132	if (pkt_len < (int)LEN_PKT_NOMAC || (pkt_len & 3) != 0) {
133		msyslog(LOG_ERR,
134			"%s: Incredible packet length: %d.  Discarding.",
135			func_name, pkt_len);
136		return PACKET_UNUSEABLE;
137	}
138	/* Note: pkt_len must be a multiple of 4 at this point! */
139	packet_end = (u_int32*)((char*)rpkt + pkt_len);
140	exten_end = skip_efields(rpkt->exten, packet_end);
141	if (NULL == exten_end) {
142		msyslog(LOG_ERR,
143			"%s: Missing extension field.  Discarding.",
144			func_name);
145		return PACKET_UNUSEABLE;
146	}
147	/* get size of MAC in cells; can be zero */
148	exten_len = (u_int)(packet_end - exten_end);
149
150	/* deduce action required from remaining length */
151	switch (exten_len) {
152
153	case 0:	/* no MAC at all */
154		break;
155
156	case 1:	/* crypto NAK */
157		key_id = ntohl(*exten_end);
158		printf("Crypto NAK = 0x%08x\n", key_id);
159		break;
160
161	case 3: /* key ID + 3DES MAC -- unsupported! */
162		msyslog(LOG_ERR,
163			"%s: Key ID + 3DES MAC is unsupported.  Discarding.",
164			func_name);
165		return PACKET_UNUSEABLE;
166
167	case 5:	/* key ID + MD5 MAC */
168	case 6:	/* key ID + SHA MAC */
169		/*
170		** Look for the key used by the server in the specified
171		** keyfile and if existent, fetch it or else leave the
172		** pointer untouched
173		*/
174		key_id = ntohl(*exten_end);
175		get_key(key_id, &pkt_key);
176		if (!pkt_key) {
177			printf("unrecognized key ID = 0x%08x\n", key_id);
178			break;
179		}
180		/*
181		** Seems like we've got a key with matching keyid.
182		**
183		** Generate a md5sum of the packet with the key from our
184		** keyfile and compare those md5sums.
185		*/
186		mac_size = exten_len << 2;
187		if (!auth_md5((char *)rpkt, pkt_len - mac_size,
188			      mac_size - 4, pkt_key)) {
189			is_authentic = FALSE;
190			break;
191		}
192		/* Yay! Things worked out! */
193		is_authentic = TRUE;
194		TRACE(1, ("sntp %s: packet from %s authenticated using key id %d.\n",
195			  func_name, stoa(sender), key_id));
196		break;
197
198	default:
199		msyslog(LOG_ERR,
200			"%s: Unexpected extension length: %d.  Discarding.",
201			func_name, exten_len);
202		return PACKET_UNUSEABLE;
203	}
204
205	switch (is_authentic) {
206
207	case -1:	/* unknown */
208		break;
209
210	case 0:		/* not authentic */
211		return SERVER_AUTH_FAIL;
212		break;
213
214	case 1:		/* authentic */
215		break;
216
217	default:	/* error */
218		break;
219	}
220
221	/* Check for server's ntp version */
222	if (PKT_VERSION(rpkt->li_vn_mode) < NTP_OLDVERSION ||
223		PKT_VERSION(rpkt->li_vn_mode) > NTP_VERSION) {
224		msyslog(LOG_ERR,
225			"%s: Packet shows wrong version (%d)",
226			func_name, PKT_VERSION(rpkt->li_vn_mode));
227		return SERVER_UNUSEABLE;
228	}
229	/* We want a server to sync with */
230	if (PKT_MODE(rpkt->li_vn_mode) != mode &&
231	    PKT_MODE(rpkt->li_vn_mode) != MODE_PASSIVE) {
232		msyslog(LOG_ERR,
233			"%s: mode %d stratum %d", func_name,
234			PKT_MODE(rpkt->li_vn_mode), rpkt->stratum);
235		return SERVER_UNUSEABLE;
236	}
237	/* Stratum is unspecified (0) check what's going on */
238	if (STRATUM_PKT_UNSPEC == rpkt->stratum) {
239		char *ref_char;
240
241		TRACE(1, ("%s: Stratum unspecified, going to check for KOD (stratum: %d)\n",
242			  func_name, rpkt->stratum));
243		ref_char = (char *) &rpkt->refid;
244		TRACE(1, ("%s: Packet refid: %c%c%c%c\n", func_name,
245			  ref_char[0], ref_char[1], ref_char[2], ref_char[3]));
246		/* If it's a KOD packet we'll just use the KOD information */
247		if (ref_char[0] != 'X') {
248			if (strncmp(ref_char, "DENY", 4) == 0)
249				return KOD_DEMOBILIZE;
250			if (strncmp(ref_char, "RSTR", 4) == 0)
251				return KOD_DEMOBILIZE;
252			if (strncmp(ref_char, "RATE", 4) == 0)
253				return KOD_RATE;
254			/*
255			** There are other interesting kiss codes which
256			** might be interesting for authentication.
257			*/
258		}
259	}
260	/* If the server is not synced it's not really useable for us */
261	if (LEAP_NOTINSYNC == PKT_LEAP(rpkt->li_vn_mode)) {
262		msyslog(LOG_ERR,
263			"%s: %s not in sync, skipping this server",
264			func_name, stoa(sender));
265		return SERVER_UNUSEABLE;
266	}
267
268	/*
269	 * Decode the org timestamp and make sure we're getting a response
270	 * to our last request, but only if we're not in broadcast mode.
271	 */
272	if (MODE_BROADCAST == mode)
273		return pkt_len;
274
275	if (!L_ISEQU(&rpkt->org, &spkt->xmt)) {
276		NTOHL_FP(&rpkt->org, &resp_org);
277		NTOHL_FP(&spkt->xmt, &sent_xmt);
278		msyslog(LOG_ERR,
279			"%s response org expected to match sent xmt",
280			stoa(sender));
281		msyslog(LOG_ERR, "resp org: %s", prettydate(&resp_org));
282		msyslog(LOG_ERR, "sent xmt: %s", prettydate(&sent_xmt));
283		return PACKET_UNUSEABLE;
284	}
285
286	return pkt_len;
287}
288