Started code for automatically defining src ip/mac for packets

4 files changed, 77 insertions, 10 deletions

diff --git a/Makefile b/Makefile
index 01dfb0a..e911bec 100644
--- a/Makefile
+++ b/Makefile
@@ -7,4 +7,4 @@ dist-clean:
 	rm -f mactelnet
 
 mactelnet: config.h main.c udp.h udp.c mactelnet.c mactelnet.h console.c console.h
-	gcc -g -o mactelnet -lcrypto main.c udp.c mactelnet.c console.c
+	gcc -g -o mactelnet -lcrypto main.c udp.c mactelnet.c console.c devices.c
diff --git a/devices.c b/devices.c
new file mode 100644
index 0000000..14ba5c4
--- /dev/null
+++ b/devices.c
@@ -0,0 +1,49 @@
+#include <stdlib.h>
+#include <string.h>
+#include <malloc.h>
+#include <unistd.h>
+#include <netinet/in.h>
+#include <sys/ioctl.h>
+#include <net/if.h>
+
+int getDeviceIndex(int sockfd, unsigned char *deviceName) {
+	struct ifreq ifr;
+
+	strncpy(ifr.ifr_name, deviceName, 16);
+	if (ioctl(sockfd, SIOCGIFINDEX, &ifr) != 0) {
+		return -1;
+	}
+
+	return ifr.ifr_ifindex;
+}
+
+int getDeviceIp(const int sockfd, const unsigned char *deviceName, struct sockaddr_in *ip) {
+	struct ifconf ifc;
+	struct ifreq *ifr;
+	int i,numDevices;
+
+	memset(&ifc, 0, sizeof(ifc));
+	if (ioctl(sockfd, SIOCGIFCONF, &ifc) != 0) {
+		return -1;
+	}
+
+	if ((ifr = malloc(ifc.ifc_len * 2)) == NULL) {
+		perror("malloc");
+		exit(1);
+	}
+
+	ifc.ifc_req = ifr;
+
+	if (ioctl(sockfd, SIOCGIFCONF, &ifc) != 0) {
+                return -1;
+        }
+
+	numDevices = ifc.ifc_len / sizeof(struct ifreq);
+	for (i = 0; i < numDevices; ++i) {
+		if (strcmp(ifr[i].ifr_name, deviceName) == 0) {
+			memcpy(ip, &(ifr[i].ifr_addr), sizeof(ip));
+			return 1;
+		}
+	}
+	return -1;
+}
diff --git a/devices.h b/devices.h
new file mode 100644
index 0000000..69ba246
--- /dev/null
+++ b/devices.h
@@ -0,0 +1,2 @@
+extern int getDeviceIndex(int sockfd, unsigned char *deviceName);
+extern int getDeviceIp(const int sockfd, const unsigned char *deviceName, struct sockaddr_in *ip);
diff --git a/main.c b/main.c
index bde22c1..60dbd3c 100644
--- a/main.c
+++ b/main.c
@@ -28,6 +28,7 @@
 #include "mactelnet.h"
 #include "udp.h"
 #include "console.h"
+#include "devices.h"
 #include "config.h"
 
 int sockfd;
@@ -146,15 +147,16 @@ int main (int argc, char **argv) {
 	struct sockaddr_in si_me;
 	char buff[1500];
 	int plen = 0;
+	int deviceIndex;
 
-	if (argc < 3) {
-		fprintf(stderr, "Usage: %s <MAC> <username> <password>\n", argv[0]);
+	if (argc < 4) {
+		fprintf(stderr, "Usage: %s <ifname> <MAC> <username> <password>\n", argv[0]);
 		return 1;
 	}
 
-	strncpy(dst, argv[1], 17);
-	strncpy(username, argv[2], 254);
-	strncpy(password, argv[3], 254);
+	strncpy(dst, argv[2], 17);
+	strncpy(username, argv[3], 254);
+	strncpy(password, argv[4], 254);
 
 	srand(time(NULL));
 
@@ -164,15 +166,29 @@ int main (int argc, char **argv) {
 	// Receive regular udp packets with this socket
 	insockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 
-	// Initialize receiving socket
+	deviceIndex = getDeviceIndex(sockfd, argv[1]);
+	if (deviceIndex < 0) {
+		fprintf(stderr, "Device %s not found.\n", argv[1]);
+		return 1;
+	}
+
+	// Even though we talk to the server without IP address, it makes it much
+	// easier to read packets when we use our real ip as the sender ip.
+	// This way we can listen to normal UDP traffic on port 20561
+	result = getDeviceIp(sockfd, argv[1], &si_me);
+	if (result < 0) {
+		fprintf(stderr, "Cannot determine IP of device %s\n", argv[1]);
+		return 1;
+	}
+
+	// Initialize receiving socket on the device chosen
 	memset((char *) &si_me, 0, sizeof(si_me));
 	si_me.sin_family = AF_INET;
 	si_me.sin_port = htons(20561);
-	si_me.sin_addr.s_addr = htonl(INADDR_ANY);
 
 	// Bind to udp port
 	if (bind(insockfd, (struct sockaddr *)&si_me, sizeof(si_me))==-1) {
-		fprintf(stderr, "Error binding to port 20561\n");
+		fprintf(stderr, "Error binding to %s:20561\n", inet_ntoa(si_me.sin_addr));
 		return 1;
 	}
 
@@ -182,7 +198,7 @@ int main (int argc, char **argv) {
 	printf("Connecting to %s...\n", dst);
 
 	plen = initPacket(data, MT_PTYPE_SESSIONSTART, src, dst, sessionkey, 0);
-	result = sendCustomUDP(sockfd, src, dst, "213.236.240.252", 20561, "255.255.255.255", 20561, data, plen);
+	result = sendCustomUDP(sockfd, src, dst, inet_ntoa(si_me.sin_addr), 20561, "255.255.255.255", 20561, data, plen);
 	if (DEBUG)
 		printf("Plen = %d, Send result: %d\n", plen, result);
 	if (DEBUG)