#include <config.h>
#include "networking.h"
#include "ntp_debug.h"
/* Send a packet */
int
sendpkt (
SOCKET rsock,
sockaddr_u *dest,
struct pkt *pkt,
int len
)
{
int cc;
#ifdef DEBUG
if (debug > 2) {
printf("sntp sendpkt: Packet data:\n");
pkt_output(pkt, len, stdout);
}
#endif
TRACE(1, ("sntp sendpkt: Sending packet to %s ...\n",
sptoa(dest)));
cc = sendto(rsock, (void *)pkt, len, 0, &dest->sa,
SOCKLEN(dest));
if (cc == SOCKET_ERROR) {
msyslog(LOG_ERR, "sendpkt: sendto(%s) failed: %m",
sptoa(dest));
return FALSE;
}
TRACE(1, ("Packet sent.\n"));
return TRUE;
}
/* Receive raw data */
int
recvdata(
SOCKET rsock,
sockaddr_u * sender,
void * rdata,
int rdata_length
)
{
GETSOCKNAME_SOCKLEN_TYPE slen;
int recvc;
slen = sizeof(*sender);
recvc = recvfrom(rsock, rdata, rdata_length, 0,
&sender->sa, &slen);
if (recvc < 0)
return recvc;
#ifdef DEBUG
if (debug > 2) {
printf("Received %d bytes from %s:\n", recvc, sptoa(sender));
pkt_output((struct pkt *)rdata, recvc, stdout);
}
#endif
return recvc;
}
/* Parsing from a short 'struct pkt' directly is bound to create
* coverity warnings. These are hard to avoid, as the formal declaration
* does not reflect the true layout in the presence of autokey extension
* fields. Parsing and skipping the extension fields of a received packet
* until there's only the MAC left is better done in this separate
* function.
*/
static void*
skip_efields(
u_int32 *head, /* head of extension chain */
u_int32 *tail /* tail/end of extension chain */
)
{
u_int nlen; /* next extension length */
while ((tail - head) > 6) {
nlen = ntohl(*head) & 0xffff;
++head;
nlen = (nlen + 3) >> 2;
if (nlen > (u_int)(tail - head) || nlen < 4)
return NULL; /* Blooper! Inconsistent! */
head += nlen;
}
return head;
}
/*
** Check if it's data for us and whether it's useable or not.
**
** If not, return a failure code so we can delete this server from our list
** and continue with another one.
*/
int
process_pkt (
struct pkt *rpkt,
sockaddr_u *sender,
int pkt_len,
int mode,
struct pkt *spkt,
const char * func_name
)
{
u_int key_id;
struct key * pkt_key;
int is_authentic;
int mac_size;
u_int exten_len;
u_int32 * exten_end;
u_int32 * packet_end;
l_fp sent_xmt;
l_fp resp_org;
// key_id = 0;
pkt_key = NULL;
is_authentic = (HAVE_OPT(AUTHENTICATION)) ? 0 : -1;
/*
* Parse the extension field if present. We figure out whether
* an extension field is present by measuring the MAC size. If
* the number of words following the packet header is 0, no MAC
* is present and the packet is not authenticated. If 1, the
* packet is a crypto-NAK; if 3, the packet is authenticated
* with DES; if 5, the packet is authenticated with MD5; if 6,
* the packet is authenticated with SHA. If 2 or 4, the packet
* is a runt and discarded forthwith. If greater than 6, an
* extension field is present, so we subtract the length of the
* field and go around again.
*/
if (pkt_len < (int)LEN_PKT_NOMAC || (pkt_len & 3) != 0) {
msyslog(LOG_ERR,
"%s: Incredible packet length: %d. Discarding.",
func_name, pkt_len);
return PACKET_UNUSEABLE;
}
/* HMS: the following needs a bit of work */
/* Note: pkt_len must be a multiple of 4 at this point! */
packet_end = (void*)((char*)rpkt + pkt_len);
exten_end = skip_efields(rpkt->exten, packet_end);
if (NULL == exten_end) {
msyslog(LOG_ERR,
"%s: Missing extension field. Discarding.",
func_name);
return PACKET_UNUSEABLE;
}
/* get size of MAC in cells; can be zero */
exten_len = (u_int)(packet_end - exten_end);
/* deduce action required from remaining length */
switch (exten_len) {
case 0: /* no Legacy MAC */
break;
case 1: /* crypto NAK */
/* Only if the keyID is 0 and there were no EFs */
key_id = ntohl(*exten_end);
printf("Crypto NAK = 0x%08x from %s\n", key_id, stoa(sender));
break;
case 3: /* key ID + 3DES MAC -- unsupported! */
msyslog(LOG_ERR,
"%s: Key ID + 3DES MAC is unsupported. Discarding.",
func_name);
return PACKET_UNUSEABLE;
case 5: /* key ID + MD5 MAC */
case 6: /* key ID + SHA MAC */
/*
** Look for the key used by the server in the specified
** keyfile and if existent, fetch it or else leave the
** pointer untouched
*/
key_id = ntohl(*exten_end);
get_key(key_id, &pkt_key);
if (!pkt_key) {
printf("unrecognized key ID = 0x%08x\n", key_id);
break;
}
/*
** Seems like we've got a key with matching keyid.
**
** Generate a md5sum of the packet with the key from our
** keyfile and compare those md5sums.
*/
mac_size = exten_len << 2;
if (!auth_md5(rpkt, pkt_len - mac_size,
mac_size - 4, pkt_key)) {
is_authentic = FALSE;
break;
}
/* Yay! Things worked out! */
is_authentic = TRUE;
TRACE(1, ("sntp %s: packet from %s authenticated using key id %d.\n",
func_name, stoa(sender), key_id));
break;
default:
msyslog(LOG_ERR,
"%s: Unexpected extension length: %d. Discarding.",
func_name, exten_len);
return PACKET_UNUSEABLE;
}
switch (is_authentic) {
case -1: /* unknown */
break;
case 0: /* not authentic */
return SERVER_AUTH_FAIL;
break;
case 1: /* authentic */
break;
default: /* error */
break;
}
/* Check for server's ntp version */
if (PKT_VERSION(rpkt->li_vn_mode) < NTP_OLDVERSION ||
PKT_VERSION(rpkt->li_vn_mode) > NTP_VERSION) {
msyslog(LOG_ERR,
"%s: Packet shows wrong version (%d)",
func_name, PKT_VERSION(rpkt->li_vn_mode));
return SERVER_UNUSEABLE;
}
/* We want a server to sync with */
if (PKT_MODE(rpkt->li_vn_mode) != mode &&
PKT_MODE(rpkt->li_vn_mode) != MODE_PASSIVE) {
msyslog(LOG_ERR,
"%s: mode %d stratum %d", func_name,
PKT_MODE(rpkt->li_vn_mode), rpkt->stratum);
return SERVER_UNUSEABLE;
}
/* Stratum is unspecified (0) check what's going on */
if (STRATUM_PKT_UNSPEC == rpkt->stratum) {
char *ref_char;
TRACE(1, ("%s: Stratum unspecified, going to check for KOD (stratum: %d)\n",
func_name, rpkt->stratum));
ref_char = (char *) &rpkt->refid;
TRACE(1, ("%s: Packet refid: %c%c%c%c\n", func_name,
ref_char[0], ref_char[1], ref_char[2], ref_char[3]));
/* If it's a KOD packet we'll just use the KOD information */
if (ref_char[0] != 'X') {
if (strncmp(ref_char, "DENY", 4) == 0)
return KOD_DEMOBILIZE;
if (strncmp(ref_char, "RSTR", 4) == 0)
return KOD_DEMOBILIZE;
if (strncmp(ref_char, "RATE", 4) == 0)
return KOD_RATE;
/*
** There are other interesting kiss codes which
** might be interesting for authentication.
*/
}
}
/* If the server is not synced it's not really useable for us */
if (LEAP_NOTINSYNC == PKT_LEAP(rpkt->li_vn_mode)) {
msyslog(LOG_ERR,
"%s: %s not in sync, skipping this server",
func_name, stoa(sender));
return SERVER_UNUSEABLE;
}
/*
* Decode the org timestamp and make sure we're getting a response
* to our last request, but only if we're not in broadcast mode.
*/
if (MODE_BROADCAST == mode)
return pkt_len;
if (!L_ISEQU(&rpkt->org, &spkt->xmt)) {
NTOHL_FP(&rpkt->org, &resp_org);
NTOHL_FP(&spkt->xmt, &sent_xmt);
msyslog(LOG_ERR,
"%s response org expected to match sent xmt",
stoa(sender));
msyslog(LOG_ERR, "resp org: %s", prettydate(&resp_org));
msyslog(LOG_ERR, "sent xmt: %s", prettydate(&sent_xmt));
return PACKET_UNUSEABLE;
}
return pkt_len;
}