[WebRTC] Stop putting addresses in the cookie chunk.

When using AF_CONN addresses, don't put these in the COOKIE
chunk. For these addresses it is possible to reconstruct them
locally. Conceptually, addresses are something to be shared
with the peer, but in the case of AF_CONN this might not be
the case. Therefore, zero then out.

Thanks to Natalie Silvanovich of Google Project Zero for
finding and reporting the issue.

netwerk/sctp/src/netinet/sctp_input.c

@@ -2517,6 +2517,27 @@ sctp_handle_cookie_echo(struct mbuf *m, int iphlen, int offset,
 		/* cookie too small */
 		return (NULL);
 	}
+#if defined(__Userspace__)
+	/*
+	 * Recover the AF_CONN addresses within the cookie.
+	 * This needs to be done in the buffer provided for later processing
+	 * of the cookie and in the mbuf chain for HMAC validation.
+	 */
+	if ((cookie->addr_type == SCTP_CONN_ADDRESS) && (src->sa_family == AF_CONN)) {
+		struct sockaddr_conn *sconnp = (struct sockaddr_conn *)src;
+
+		memcpy(cookie->address, &sconnp->sconn_addr , sizeof(void *));
+		m_copyback(m, cookie_offset + offsetof(struct sctp_state_cookie, address),
+		           (int)sizeof(void *), (caddr_t)&sconnp->sconn_addr);
+	}
+	if ((cookie->laddr_type == SCTP_CONN_ADDRESS) && (dst->sa_family == AF_CONN)) {
+		struct sockaddr_conn *sconnp = (struct sockaddr_conn *)dst;
+
+		memcpy(cookie->laddress, &sconnp->sconn_addr , sizeof(void *));
+		m_copyback(m, cookie_offset + offsetof(struct sctp_state_cookie, laddress),
+		           (int)sizeof(void *), (caddr_t)&sconnp->sconn_addr);
+	}
+#endif
 	/*
 	 * split off the signature into its own mbuf (since it should not be
 	 * calculated in the sctp_hmac_m() call).

netwerk/sctp/src/netinet/sctp_output.c

@@ -6492,6 +6492,27 @@ sctp_send_initiate_ack(struct sctp_inpcb *inp, struct sctp_tcb *stcb,
 			  (uint8_t *)inp->sctp_ep.secret_key[(int)(inp->sctp_ep.current_secret_number)],
 			  SCTP_SECRET_SIZE, m_cookie, sizeof(struct sctp_paramhdr),
 			  (uint8_t *)signature, SCTP_SIGNATURE_SIZE);
+#if defined(__Userspace__)
+	/*
+	 * Don't put AF_CONN addresses on the wire, in case this is critical
+	 * for the application. However, they are protected by the HMAC and
+	 * need to be reconstructed before checking the HMAC.
+	 * Clearing is only done in the mbuf chain, since the local stc is
+	 * not used anymore.
+	 */
+	if (stc.addr_type == SCTP_CONN_ADDRESS) {
+		const void *p = NULL;
+
+		m_copyback(m_cookie, sizeof(struct sctp_paramhdr) + offsetof(struct sctp_state_cookie, address),
+		           (int)sizeof(void *), (caddr_t)&p);
+	}
+	if (stc.laddr_type == SCTP_CONN_ADDRESS) {
+		const void *p = NULL;
+
+		m_copyback(m_cookie, sizeof(struct sctp_paramhdr) + offsetof(struct sctp_state_cookie, laddress),
+		           (int)sizeof(void *), (caddr_t)&p);
+	}
+#endif
 	/*
 	 * We sifa 0 here to NOT set IP_DF if its IPv4, we ignore the return
 	 * here since the timer will drive a retranmission.