--- /sys/src/libsec/port/tlshand.c
+++ /sys/src/libsec/port/tlshand.c
@@ -97,6 +97,7 @@ typedef struct Msg{
 			Bytes*	sid;
 			Ints*	ciphers;
 			Bytes*	compressors;
+			Ints*	sigAlgs;
 		} clientHello;
 		struct {
 			int version;
@@ -245,6 +246,19 @@ enum {
 	CompressionMax
 };
 
+// extensions
+enum {
+	ExtSigalgs = 0xd,
+};
+
+// signature algorithms
+enum {
+	RSA_PKCS1_SHA1   = 0x0201,
+	RSA_PKCS1_SHA256 = 0x0401,
+	RSA_PKCS1_SHA384 = 0x0501,
+	RSA_PKCS1_SHA512 = 0x0601
+};
+
 static Algs cipherAlgs[] = {
 	{"rc4_128", "md5", 2*(16+MD5dlen), TLS_RSA_WITH_RC4_128_MD5},
 	{"rc4_128", "sha1", 2*(16+SHA1dlen), TLS_RSA_WITH_RC4_128_SHA},
@@ -257,6 +271,11 @@ static uchar compressors[] = {
 	CompressionNull,
 };
 
+static int sigAlgs[] = {
+	RSA_PKCS1_SHA256,
+	RSA_PKCS1_SHA1,
+};
+
 static TlsConnection *tlsServer2(int ctl, int hand, uchar *cert, int ncert, int (*trace)(char*fmt, ...), PEMChain *chain);
 static TlsConnection *tlsClient2(int ctl, int hand, uchar *csid, int ncsid, int (*trace)(char*fmt, ...));
 
@@ -644,6 +663,8 @@ tlsClient2(int ctl, int hand, uchar *csid, int ncsid, int (*trace)(char*fmt, ...
 	m.u.clientHello.sid = makebytes(csid, ncsid);
 	m.u.clientHello.ciphers = makeciphers();
 	m.u.clientHello.compressors = makebytes(compressors,sizeof(compressors));
+	if(c->clientVersion >= TLS12Version)
+		m.u.clientHello.sigAlgs = makeints(sigAlgs, nelem(sigAlgs));
 	if(!msgSend(c, &m, AFlush))
 		goto Err;
 	msgClear(&m);
@@ -874,6 +895,19 @@ msgSend(TlsConnection *c, Msg *m, int act)
 		p[0] = n;
 		memmove(p+1, m->u.clientHello.compressors->data, n);
 		p += n+1;
+
+		if(m->u.clientHello.sigAlgs != nil) {
+			n = m->u.clientHello.sigAlgs->len;
+			put16(p, 6 + 2*n);   /* length of extensions */
+			put16(p+2, ExtSigalgs);
+			put16(p+4, 2 + 2*n); /* length of extension content */
+			put16(p+6, 2*n);     /* length of algorithm list */
+			p += 8;
+			for(i = 0; i < n; i++) {
+				put16(p, m->u.clientHello.sigAlgs->data[i]);
+				p += 2;
+			}
+		}
 		break;
 	case HServerHello:
 		put16(p, m->u.serverHello.version);
@@ -983,7 +1017,7 @@ static int
 msgRecv(TlsConnection *c, Msg *m)
 {
 	uchar *p;
-	int type, n, nn, i, nsid, nrandom, nciph;
+	int type, n, nn, nx, i, nsid, nrandom, nciph;
 
 	for(;;) {
 		p = tlsReadN(c, 4);
@@ -1101,7 +1135,40 @@ msgRecv(TlsConnection *c, Msg *m)
 		nn = p[0];
 		m->u.clientHello.compressors = newbytes(nn);
 		memmove(m->u.clientHello.compressors->data, p+1, nn);
+		p += nn + 1;
 		n -= nn + 1;
+
+		/* extensions */
+		if(n == 0)
+			break;
+		if(n < 2)
+			goto Short;
+		nx = get16(p);
+		p += 2;
+		n -= 2;
+		while(nx > 0){
+			if(n < nx || nx < 4)
+				goto Short;
+			i = get16(p);
+			nn = get16(p+2);
+			if(nx < nn+4)
+				goto Short;
+			nx -= nn+4;
+			p += 4;
+			n -= 4;
+			if(i == ExtSigalgs){
+				if(get16(p) != nn-2)
+					goto Short;
+				p += 2;
+				n -= 2;
+				nn -= 2;
+				m->u.clientHello.sigAlgs = newints(nn/2);
+				for(i = 0; i < nn; i += 2)
+					m->u.clientHello.sigAlgs->data[i >> 1] = get16(&p[i]);
+			}
+			p += nn;
+			n -= nn;
+		}
 		break;
 	case HServerHello:
 		if(n < 2)
@@ -1254,6 +1321,7 @@ msgClear(Msg *m)
 		freeints(m->u.clientHello.ciphers);
 		m->u.clientHello.ciphers = nil;
 		freebytes(m->u.clientHello.compressors);
+		freeints(m->u.clientHello.sigAlgs);
 		break;
 	case HServerHello:
 		freebytes(m->u.clientHello.sid);
@@ -1338,6 +1406,8 @@ msgPrint(char *buf, int n, Msg *m)
 		bs = bytesPrint(bs, be, "\tsid: ", m->u.clientHello.sid, "\n");
 		bs = intsPrint(bs, be, "\tciphers: ", m->u.clientHello.ciphers, "\n");
 		bs = bytesPrint(bs, be, "\tcompressors: ", m->u.clientHello.compressors, "\n");
+		if(m->u.clientHello.sigAlgs != nil)
+			bs = intsPrint(bs, be, "\tsigAlgs: ", m->u.clientHello.sigAlgs, "\n");
 		break;
 	case HServerHello:
 		bs = seprint(bs, be, "ServerHello\n");