1 #include <config.h>
2 #include "networking.h"
3 #include "ntp_debug.h"
4
5
6 /* Send a packet */
7 int
sendpkt(SOCKET rsock,sockaddr_u * dest,struct pkt * pkt,int len)8 sendpkt (
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 */
40 int
recvdata(SOCKET rsock,sockaddr_u * sender,void * rdata,int rdata_length)41 recvdata(
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 */
72 static void*
skip_efields(u_int32 * head,u_int32 * tail)73 skip_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 */
96 int
process_pkt(struct pkt * rpkt,sockaddr_u * sender,int pkt_len,int mode,struct pkt * spkt,const char * func_name)97 process_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 = (void*)((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(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