Function sppp_chap_input

freebsd/net/if_spppsubr.c:3970–4188

* Handle incoming CHAP packets. */

 * Handle incoming CHAP packets.
 */
static void
sppp_chap_input(struct sppp *sp, struct mbuf *m)
{
	STDDCL;
	struct lcp_header *h;
	int len;
	u_char *value, *name, digest[AUTHKEYLEN], dsize;
	int value_len, name_len;
	MD5_CTX ctx;

	len = m->m_pkthdr.len;
	if (len < 4) {
		if (debug)
			log(LOG_DEBUG,
			    SPP_FMT "chap invalid packet length: %d bytes\n",
			    SPP_ARGS(ifp), len);
		return;
	}
	h = mtod (m, struct lcp_header*);
	if (len > ntohs (h->len))
		len = ntohs (h->len);

	switch (h->type) {
	/* challenge, failure and success are his authproto */
	case CHAP_CHALLENGE:
		value = 1 + (u_char*)(h+1);
		value_len = value[-1];
		name = value + value_len;
		name_len = len - value_len - 5;
		if (name_len < 0) {
			if (debug) {
				log(LOG_DEBUG,
				    SPP_FMT "chap corrupted challenge "
				    "<%s id=0x%x len=%d",
				    SPP_ARGS(ifp),
				    sppp_auth_type_name(PPP_CHAP, h->type),
				    h->ident, ntohs(h->len));
				sppp_print_bytes((u_char*) (h+1), len-4);
				log(-1, ">\n");
			}
			break;
		}

		if (debug) {
			log(LOG_DEBUG,
			    SPP_FMT "chap input <%s id=0x%x len=%d name=",
			    SPP_ARGS(ifp),
			    sppp_auth_type_name(PPP_CHAP, h->type), h->ident,
			    ntohs(h->len));
			sppp_print_string((char*) name, name_len);
			log(-1, " value-size=%d value=", value_len);
			sppp_print_bytes(value, value_len);
			log(-1, ">\n");
		}

		/* Compute reply value. */
		MD5Init(&ctx);
		MD5Update(&ctx, &h->ident, 1);