incorporate response creation and sending from adsuck

1 files changed, 276 insertions, 8 deletions

diff --git a/src/receive.c b/src/receive.c
index eb5fdb2..59697d3 100644
--- a/src/receive.c
+++ b/src/receive.c
@@ -14,16 +14,20 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+/* for strdup() */
+#define _POSIX_C_SOURCE 200809L
+#include <string.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <err.h>
 
 #include <netinet/in.h>
-
 #include <arpa/inet.h>
 
 #include <ldns/ldns.h>
 
+#define MAXLINE 256
 #define INBUF_SIZE 4096
 #define PORT 53
 
@@ -56,7 +60,7 @@ void
 printpacket(ldns_pkt *pkt)
 {
 	char			*str = ldns_pkt2str(pkt);
-	
+
 	if (str) {
 		printf("%s", str);
 		LDNS_FREE(str);
@@ -64,16 +68,17 @@ printpacket(ldns_pkt *pkt)
 		warnx("could not convert packet to string");
 }
 
-void receive_and_print(int so) {
+ldns_pkt *
+receive_and_print(int so) {
 	uint8_t			inbuf[INBUF_SIZE];
 	ssize_t			nb;
 	ldns_status		status;
 	ldns_pkt		*query_pkt;
-	
+
 	nb = recvfrom(so, inbuf, INBUF_SIZE, 0, &paddr, &plen);
 	if (nb == -1) {
 		if (errno == EINTR || errno == EAGAIN)
-			return;
+			return NULL;
 		else
 			err(EXIT_FAILURE, "recvfrom");
 	}
@@ -81,23 +86,286 @@ void receive_and_print(int so) {
 	status = ldns_wire2pkt(&query_pkt, inbuf, (size_t)nb);
 	if (status != LDNS_STATUS_OK) {
 		warnx("bad packet: %s", ldns_get_errorstr_by_id(status));
-		return;
+		return NULL;
 	} else {
 		puts("received packet:");
 		printpacket(query_pkt);
 	}
 
+	return query_pkt;
+}
+
+int
+send_response(int so, const char *hostname, ldns_pkt *respkt, uint16_t id)
+{
+	size_t			answer_size;
+	ldns_status		status;
+	uint8_t			*outbuf = NULL;
+	int			rv = 1;
+
+	if (hostname == NULL || respkt == NULL) {
+		warnx("send_response: invalid parameters");
+		return (0);
+	}
+
+	ldns_pkt_set_id(respkt, id);
+	status = ldns_pkt2wire(&outbuf, respkt, &answer_size);
+	if (status != LDNS_STATUS_OK)
+		warnx("can't create answer: %s",
+		      ldns_get_errorstr_by_id(status));
+	else {
+		puts("response packet:");
+		printpacket(respkt);
+
+		if (sendto(so, outbuf, answer_size, 0, &paddr, plen) == -1)
+			warn("send_response: sendto");
+		else {
+			rv = 0;
+
+			printf("send_response: resolved %s", hostname);
+		}
+	}
+
+	if (outbuf)
+		LDNS_FREE(outbuf);
+
+	return (rv);
+}
+
+char *
+hostnamefrompkt(ldns_pkt *pkt, ldns_rr **qrr)
+{
+	ldns_rr			*query_rr;
+	ldns_buffer		*out = NULL;
+	ldns_rdf		*rdf;
+	char			*ret = NULL;
+
+	if (pkt == NULL)
+		return (NULL);
+
+	query_rr = ldns_rr_list_rr(ldns_pkt_question(pkt), 0);
+	if (query_rr == NULL) {
+		warnx("hostnamefrompkt invalid parameters");
+		goto done;
+	}
+
+	out = ldns_buffer_new(LDNS_MAX_DOMAINLEN);
+	if (out == NULL) {
+		warnx("no memory for out buffer");
+		goto done;
+	}
+
+	rdf = ldns_rr_owner(query_rr);
+	if (ldns_rdf2buffer_str_dname(out, rdf) != LDNS_STATUS_OK) {
+		warnx("can't get hostname");
+		goto done;
+	}
+
+	ret = strdup((char *)ldns_buffer_begin(out));
+	if (ret == NULL) {
+		warn("no memory for hostname");
+		goto done;
+	}
+
+	if (qrr)
+		*qrr = query_rr;
+done:
+	if (out)
+		ldns_buffer_free(out);
+
+	return (ret);
+}
+
+int
+spoofquery(int so, const char *hostname, ldns_rr *query_rr, u_int16_t id)
+{
+	ldns_status		status;
+	ldns_rr_list		*answer_an = NULL;
+	ldns_rr_list		*answer_ns = NULL;
+	ldns_rr_list		*answer_ad = NULL;
+	ldns_rr_list		*answer_qr = NULL;
+	ldns_pkt		*answer_pkt = NULL;
+	ldns_rr			*myrr = NULL, *myaurr = NULL, *myasrr = NULL;
+	ldns_rdf		*prev = NULL;
+	char			buf[MAXLINE * 2];
+	uint8_t			*outbuf = NULL;
+	int			rv = 1;
+	const char	        *ipaddr = "127.0.0.1";
+
+	/* answer section */
+	answer_an = ldns_rr_list_new();
+	if (answer_an == NULL)
+		goto unwind;
+
+	/* authority section */
+	answer_ns = ldns_rr_list_new();
+	if (answer_ns == NULL)
+		goto unwind;
+
+	/* if we have an ip spoof it there */
+	if (ipaddr) {
+		/* an */
+		snprintf(buf, sizeof buf, "%s\t%d\tIN\tA\t%s",
+			 hostname, 259200, ipaddr);
+		status = ldns_rr_new_frm_str(&myrr, buf, 0, NULL, &prev);
+		if (status != LDNS_STATUS_OK) {
+			fprintf(stderr, "can't create answer section: %s\n",
+				ldns_get_errorstr_by_id(status));
+			goto unwind;
+		}
+		ldns_rr_list_push_rr(answer_an, myrr);
+		ldns_rdf_deep_free(prev);
+		prev = NULL;
+
+		/* ns */
+		snprintf(buf, sizeof buf, "%s\t%d\tIN\tNS\t%s.",
+			 hostname, 259200, "localhost");
+		status = ldns_rr_new_frm_str(&myaurr, buf, 0, NULL, &prev);
+		if (status != LDNS_STATUS_OK) {
+			fprintf(stderr, "can't create authority section: %s\n",
+				ldns_get_errorstr_by_id(status));
+			goto unwind;
+		}
+		ldns_rr_list_push_rr(answer_ns, myaurr);
+		ldns_rdf_deep_free(prev);
+		prev = NULL;
+	} else {
+		snprintf(buf, sizeof buf, "%s\t3600\tIN\tSOA\t%s root.%s %s",
+			 hostname,
+			 hostname,
+			 hostname,
+			 "2 3600 900 3600000 3600");
+		status = ldns_rr_new_frm_str(&myaurr, buf, 0, NULL, &prev);
+		if (status != LDNS_STATUS_OK) {
+			fprintf(stderr, "can't create authority section: %s\n",
+				ldns_get_errorstr_by_id(status));
+			goto unwind;
+		}
+		ldns_rr_list_push_rr(answer_ns, myaurr);
+		ldns_rdf_deep_free(prev);
+		prev = NULL;
+	}
+
+	/* question section */
+	answer_qr = ldns_rr_list_new();
+	if (answer_qr == NULL)
+		goto unwind;
+	ldns_rr_list_push_rr(answer_qr, ldns_rr_clone(query_rr));
+
+	/* additional section */
+	answer_ad = ldns_rr_list_new();
+	if (answer_ad == NULL)
+		goto unwind;
+	if (ipaddr) {
+		snprintf(buf, sizeof buf, "%s\t%d\tIN\tA\t%s",
+			 "localhost",
+			 259200,
+			 "127.0.0.1");
+		status = ldns_rr_new_frm_str(&myasrr, buf, 0, NULL, &prev);
+		if (status != LDNS_STATUS_OK) {
+			fprintf(stderr, "can't create additional section: %s\n",
+				ldns_get_errorstr_by_id(status));
+			goto unwind;
+		}
+		ldns_rr_list_push_rr(answer_ad, myasrr);
+		ldns_rdf_deep_free(prev);
+		prev = NULL;
+
+		/* V6 */
+		snprintf(buf, sizeof buf, "%s\t%d\tIN\tAAAA\t%s",
+			 "localhost",
+			 259200,
+			 "::1");
+		status = ldns_rr_new_frm_str(&myasrr, buf, 0, NULL, &prev);
+		if (status != LDNS_STATUS_OK) {
+			fprintf(stderr, "can't create additional section: %s\n",
+				ldns_get_errorstr_by_id(status));
+			goto unwind;
+		}
+		ldns_rr_list_push_rr(answer_ad, myasrr);
+		ldns_rdf_deep_free(prev);
+		prev = NULL;
+	}
+
+	/* actual packet */
+	answer_pkt = ldns_pkt_new();
+	if (answer_pkt == NULL)
+		goto unwind;
+
+	ldns_pkt_set_qr(answer_pkt, 1);
+	ldns_pkt_set_aa(answer_pkt, 1);
+	if (ipaddr == NULL)
+		ldns_pkt_set_rcode(answer_pkt, LDNS_RCODE_NXDOMAIN);
+
+	ldns_pkt_push_rr_list(answer_pkt, LDNS_SECTION_QUESTION, answer_qr);
+	ldns_pkt_push_rr_list(answer_pkt, LDNS_SECTION_ANSWER, answer_an);
+	ldns_pkt_push_rr_list(answer_pkt, LDNS_SECTION_AUTHORITY, answer_ns);
+	ldns_pkt_push_rr_list(answer_pkt, LDNS_SECTION_ADDITIONAL, answer_ad);
+
+	/* reply to caller */
+	if (send_response(so, hostname, answer_pkt, id))
+		warnx("send_response failed");
+
+unwind:
+	if (answer_pkt)
+		ldns_pkt_free(answer_pkt);
+	if (outbuf)
+		LDNS_FREE(outbuf);
+	if (answer_qr)
+		ldns_rr_list_free(answer_qr);
+	if (answer_an)
+		ldns_rr_list_free(answer_an);
+	if (answer_ns)
+		ldns_rr_list_free(answer_ns);
+	if (answer_ad)
+		ldns_rr_list_free(answer_ad);
+
+	return (rv);
+}
+
+int handle_query(int so) {
+	ldns_pkt *query_pkt;
+	ldns_rr  *query_rr;
+	uint16_t id;
+	int rv = 1;
+	char *hostname;
+
+	query_pkt = receive_and_print(so);
+	if (!query_pkt)
+		return 1;
+
+	hostname = hostnamefrompkt(query_pkt, &query_rr);
+	if (!hostname)
+		goto out_cleanup_pkt;
+
+	id = ldns_pkt_id(query_pkt);
+
+	rv = spoofquery(so, hostname, query_rr, id);
+
+	free(hostname);
+
+out_cleanup_pkt:
 	ldns_pkt_free(query_pkt);
+	return rv;
 }
 
 int main(int argc, char **argv) {
 	int so;
-	
+
 	if (geteuid())
 		errx(1, "need root privileges");
 
 	so = socket_create(PORT);
 
+	/*
+	 * The original adsuck program would additionally do many cool things
+	 * in main(), i.e. parse command line options, drop root privileges,
+	 * setup signal handlers, etc. We could incorporate some of this into
+	 * our program later. I omitted it for now for simplicity and to
+	 * ease porting to windoze if You guys want to do that (but don't
+	 * count on me in this matter).
+	 */
+
 	while (1)
-		receive_and_print(so);
+		handle_query(so);
 }