shithub: musw

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implemented per-packet HMAC to avoid MITM tampering.

--- a/dat.h

+++ b/dat.h

@@ -46,7 +46,7 @@

 enum {

 	ProtocolID	= 0x5753554d,	/* MUSW */

-	Framehdrsize	= 4+1+4+4+2,

+	Framehdrsize	= 4+1+4+4+2+MD5dlen,

 	MTU		= 1024

 };

@@ -147,6 +147,7 @@

 	u32int seq;

 	u32int ack;

 	u16int len;

+	uchar sig[MD5dlen];

 	uchar data[];

 };

@@ -177,3 +178,5 @@

 	Universe *u;

 	Party *prev, *next;

 };

+

+#pragma varargck type "Φ" Frame*

--- /dev/null

+++ b/fmt.c

@@ -1,0 +1,25 @@

+#include <u.h>

+#include <libc.h>

+#include <ip.h>

+#include <mp.h>

+#include <libsec.h>

+#include <thread.h>

+#include <draw.h>

+#include <geometry.h>

+#include "dat.h"

+#include "fns.h"

+

+int

+Φfmt(Fmt *f)

+{

+	int n, i;

+	Frame *frame;

+

+	frame = va_arg(f->args, Frame*);

+

+	n = fmtprint(f, "id %x type %ud seq %ud ack %ud len %ud sig ",

+		frame->id, frame->type, frame->seq, frame->ack, frame->len);

+	for(i = 0; i < MD5dlen; i++)

+		n += fmtprint(f, "%2.2x", frame->sig[i]);

+	return n;

+}

--- a/fns.h

+++ b/fns.h

@@ -53,4 +53,11 @@

 NetConn *newnetconn(NCState, Udphdr*);

 void delnetconn(NetConn*);

 Frame *newframe(Frame*, u8int, u32int, u32int, u16int, uchar*);

+void signframe(Frame*, ulong);

+int verifyframe(Frame*, ulong);

 void delframe(Frame*);

+

+/*

+ * fmt

+ */

+int Φfmt(Fmt*);

--- a/mkfile

+++ b/mkfile

@@ -15,6 +15,7 @@

 	universe.$O\

 	sprite.$O\

 	net.$O\

+	fmt.$O\

 HFILES=\

 	dat.h\

--- a/musw.c

+++ b/musw.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <bio.h>

 #include <thread.h>

 #include <draw.h>

@@ -164,6 +166,7 @@

 	frame = newframe(nil, NCinput, 0, 0, sizeof(kdown), nil);

 	pack(frame->data, frame->len, "k", kdown);

+	signframe(frame, netconn.dh.priv);

 	sendp(egress, frame);

 }

@@ -241,9 +244,8 @@

 		if(debug){

 			rport = frame->udp.rport[0]<<8 | frame->udp.rport[1];

 			lport = frame->udp.lport[0]<<8 | frame->udp.lport[1];

-			fprint(2, "%I!%ud ← %I!%ud | rcvd type %ud seq %ud ack %ud len %ud\n",

-				frame->udp.laddr, lport, frame->udp.raddr, rport,

-				frame->type, frame->seq, frame->ack, frame->len);

+			fprint(2, "%I!%ud → %I!%ud | rcvd %Φ\n",

+				frame->udp.laddr, lport, frame->udp.raddr, rport, frame);

 		}

 	}

 	closeioproc(io);

@@ -267,7 +269,7 @@

 				unpack(frame->data, frame->len, "kk", &netconn.dh.p, &netconn.dh.g);

 				newf = newframe(frame, NCdhx, 0, 0, sizeof(ulong), nil);

-	

+

 				netconn.dh.sec = truerand();

 				pack(newf->data, newf->len, "k", dhgenkey(netconn.dh.g, netconn.dh.sec, netconn.dh.p));

 				sendp(egress, newf);

@@ -274,7 +276,7 @@

 				if(debug)

 					fprint(2, "\tsent pubkey %ld\n", dhgenkey(netconn.dh.g, netconn.dh.sec, netconn.dh.p));

-	

+

 				break;

 			case NSdhx:

 				unpack(frame->data, frame->len, "k", &netconn.dh.pub);

@@ -281,7 +283,7 @@

 				netconn.state = NCSConnected;

 				if(debug)

-					fprint(2, "\trecvd pubkey %ld\n", netconn.dh.pub);

+					fprint(2, "\trcvd pubkey %ld\n", netconn.dh.pub);

 				netconn.dh.priv = dhgenkey(netconn.dh.pub, netconn.dh.sec, netconn.dh.p);

 				break;

@@ -288,6 +290,12 @@

 			}

 			break;

 		case NCSConnected:

+			if(verifyframe(frame, netconn.dh.priv) != 0){

+				if(debug)

+					fprint(2, "\tbad signature\n");

+				goto discard;

+			}

+

 			switch(frame->type){

 			case NSsimstate:

 				unpack(frame->data, frame->len, "PdPdP",

@@ -297,6 +305,7 @@

 				break;

 			case NSnudge:

 				newf = newframe(frame, NCnudge, 0, 0, 0, nil);

+				signframe(newf, netconn.dh.priv);

 				sendp(egress, newf);

@@ -308,7 +317,7 @@

 			break;

 		}

 discard:

-		free(frame);

+		delframe(frame);

 	}

 }

@@ -332,9 +341,8 @@

 		if(debug){

 			rport = frame->udp.rport[0]<<8 | frame->udp.rport[1];

 			lport = frame->udp.lport[0]<<8 | frame->udp.lport[1];

-			fprint(2, "%I!%ud → %I!%ud | sent type %ud seq %ud ack %ud len %ud\n",

-				frame->udp.laddr, lport, frame->udp.raddr, rport,

-				frame->type, frame->seq, frame->ack, frame->len);

+			fprint(2, "%I!%ud → %I!%ud | sent %Φ\n",

+				frame->udp.laddr, lport, frame->udp.raddr, rport, frame);

 		}

 		free(frame);

@@ -438,6 +446,7 @@

 	GEOMfmtinstall();

 	fmtinstall('I', eipfmt);

+	fmtinstall(L'Φ', Φfmt);

 	ARGBEGIN{

 	case 'd':

 		debug++;

--- a/muswd.c

+++ b/muswd.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <thread.h>

 #include <draw.h>

 #include <geometry.h>

@@ -46,7 +48,7 @@

 	ncpe = conns+nconns;

-	for(ncp = conns; ncp < conns+nconns; ncp++)

+	for(ncp = conns; ncp < ncpe; ncp++)

 		if(*ncp == nc){

 			memmove(ncp, ncp+1, sizeof(NetConn*)*(ncpe-ncp-1));

 			nconns--;

@@ -77,9 +79,8 @@

 		if(debug){

 			rport = frame->udp.rport[0]<<8 | frame->udp.rport[1];

 			lport = frame->udp.lport[0]<<8 | frame->udp.lport[1];

-			fprint(2, "%I!%ud ← %I!%ud | rcvd type %ud seq %ud ack %ud len %ud\n",

-				frame->udp.laddr, lport, frame->udp.raddr, rport,

-				frame->type, frame->seq, frame->ack, frame->len);

+			fprint(2, "%I!%ud → %I!%ud | rcvd %Φ\n",

+				frame->udp.laddr, lport, frame->udp.raddr, rport, frame);

 		}

 	}

 	closeioproc(io);

@@ -103,13 +104,13 @@

 			if(frame->type == NChi){

 				nc = newnetconn(NCSConnecting, &frame->udp);

 				putconn(nc);

-	

+

 				newf = newframe(frame, NShi, 0, 0, 2*sizeof(ulong), nil);

-	

+

 				dhgenpg(&nc->dh.p, &nc->dh.g);

 				pack(newf->data, newf->len, "kk", nc->dh.p, nc->dh.g);

 				sendp(egress, newf);

-	

+

 				if(debug)

 					fprint(2, "\tsent p %ld g %ld\n", nc->dh.p, nc->dh.g);

 			}else

@@ -124,10 +125,10 @@

 				nc->state = NCSConnected;

 				if(debug)

-					fprint(2, "\trecvd pubkey %ld\n", nc->dh.pub);

+					fprint(2, "\trcvd pubkey %ld\n", nc->dh.pub);

 				newf = newframe(frame, NSdhx, 0, 0, sizeof(ulong), nil);

-	

+

 				nc->dh.sec = truerand();

 				nc->dh.priv = dhgenkey(nc->dh.pub, nc->dh.sec, nc->dh.p);

 				pack(newf->data, newf->len, "k", dhgenkey(nc->dh.g, nc->dh.sec, nc->dh.p));

@@ -140,6 +141,12 @@

 			}

 			break;

 		case NCSConnected:

+			if(verifyframe(frame, nc->dh.priv) != 0){

+				if(debug)

+					fprint(2, "\tbad signature\n");

+				goto discard;

+			}

+

 			switch(frame->type){

 			case NCinput:

 				unpack(frame->data, frame->len, "k", &kdown);

@@ -150,13 +157,13 @@

 				break;

 			case NCbuhbye:

 				popconn(nc);

-				free(nc);

+				delnetconn(nc);

 				break;

 			}

 			break;

 		}

 discard:

-		free(frame);

+		delframe(frame);

 	}

 }

@@ -180,9 +187,8 @@

 		if(debug){

 			rport = frame->udp.rport[0]<<8 | frame->udp.rport[1];

 			lport = frame->udp.lport[0]<<8 | frame->udp.lport[1];

-			fprint(2, "%I!%ud → %I!%ud | sent type %ud seq %ud ack %ud len %ud\n",

-				frame->udp.laddr, lport, frame->udp.raddr, rport,

-				frame->type, frame->seq, frame->ack, frame->len);

+			fprint(2, "%I!%ud → %I!%ud | sent %Φ\n",

+				frame->udp.laddr, lport, frame->udp.raddr, rport, frame);

 		}

 		free(frame);

@@ -334,6 +340,7 @@

 	GEOMfmtinstall();

 	fmtinstall('I', eipfmt);

+	fmtinstall(L'Φ', Φfmt);

 	addr = "udp!*!112";

 	ARGBEGIN{

 	case 'a':

--- a/net.c

+++ b/net.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <thread.h>

 #include <draw.h>

 #include <geometry.h>

@@ -69,6 +71,7 @@

 	Frame *f;

 	f = emalloc(sizeof(Frame)+len);

+	memset(f, 0, sizeof(Frame));

 	f->id = ProtocolID;

 	f->type = type;

 	if(pf != nil){

@@ -85,6 +88,40 @@

 		memmove(f->data, data, f->len);

 	return f;

+}

+

+void

+signframe(Frame *f, ulong key)

+{

+	uchar k[sizeof(ulong)];

+	uchar h[MD5dlen];

+	uchar msg[MTU];

+	int n;

+

+	k[0] = key; k[1] = key>>8; k[2] = key>>16; k[3] = key>>24;

+

+	memset(f->sig, 0, MD5dlen);

+	n = pack(msg, sizeof msg, "f", f);

+	hmac_md5(msg, n, k, sizeof k, h, nil);

+	memmove(f->sig, h, MD5dlen);

+}

+

+int

+verifyframe(Frame *f, ulong key)

+{

+	uchar k[sizeof(ulong)];

+	uchar h0[MD5dlen], h1[MD5dlen];

+	uchar msg[MTU];

+	int n;

+

+	k[0] = key; k[1] = key>>8; k[2] = key>>16; k[3] = key>>24;

+

+	memmove(h0, f->sig, MD5dlen);

+	memset(f->sig, 0, MD5dlen);

+	n = pack(msg, sizeof msg, "f", f);

+	hmac_md5(msg, n, k, sizeof k, h1, nil);

+	memmove(f->sig, h0, MD5dlen);

+	return memcmp(h0, h1, MD5dlen);

 }

 void

--- a/pack.c

+++ b/pack.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <draw.h>

 #include <geometry.h>

 #include "dat.h"

@@ -91,6 +93,7 @@

 			put4(p, F->seq), p += 4;

 			put4(p, F->ack), p += 4;

 			put2(p, F->len), p += 2;

+			memmove(p, F->sig, MD5dlen), p += MD5dlen;

 			if(p+F->len > e)

 				goto err;

@@ -161,6 +164,7 @@

 			F->seq = get4(p), p += 4;

 			F->ack = get4(p), p += 4;

 			F->len = get2(p), p += 2;

+			memmove(F->sig, p, MD5dlen), p += MD5dlen;

 			if(p+F->len > e)

 				goto err;

--- a/party.c

+++ b/party.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <draw.h>

 #include <geometry.h>

 #include "dat.h"

--- a/physics.c

+++ b/physics.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <draw.h>

 #include <geometry.h>

 #include "dat.h"

--- a/sprite.c

+++ b/sprite.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <draw.h>

 #include <geometry.h>

 #include "dat.h"

--- a/universe.c

+++ b/universe.c

@@ -1,6 +1,8 @@

 #include <u.h>

 #include <libc.h>

 #include <ip.h>

+#include <mp.h>

+#include <libsec.h>

 #include <draw.h>

 #include <geometry.h>

 #include "dat.h"