Merge branch 'feature/starttls' of https://github.com/RichardPoole42/sslsplit into feature/autossl

opts.c

@@ -123,7 +123,7 @@ opts_has_ssl_spec(opts_t *opts)
 	proxyspec_t *p = opts->spec;
 
 	while (p) {
-		if (p->ssl)
+		if (p->ssl || p->tlspeek)
 			return 1;
 		p = p->next;
 	}
@@ -284,18 +284,27 @@ proxyspec_parse(int *argc, char **argv[], const char *natengine)
 				if (!strcmp(**argv, "tcp")) {
 					spec->ssl = 0;
 					spec->http = 0;
+					spec->tlspeek = 0;
 				} else
 				if (!strcmp(**argv, "ssl")) {
 					spec->ssl = 1;
 					spec->http = 0;
+					spec->tlspeek = 0;
 				} else
 				if (!strcmp(**argv, "http")) {
 					spec->ssl = 0;
 					spec->http = 1;
+					spec->tlspeek = 0;
 				} else
 				if (!strcmp(**argv, "https")) {
 					spec->ssl = 1;
 					spec->http = 1;
+					spec->tlspeek = 0;
+				} else
+				if (!strcmp(**argv, "genericstarttls")) {
+					spec->ssl = 0;
+					spec->http = 0;
+					spec->tlspeek = 1;
 				} else {
 					fprintf(stderr, "Unknown connection "
 					                "type '%s'\n", **argv);
@@ -459,9 +468,10 @@ proxyspec_str(proxyspec_t *spec)
 			return NULL;
 		}
 	}
-	if (asprintf(&s, "[%s]:%s %s %s %s", lhbuf, lpbuf,
+	if (asprintf(&s, "[%s]:%s %s %s %s %s", lhbuf, lpbuf,
 	             (spec->ssl ? "ssl" : "tcp"),
 	             (spec->http ? "http" : "plain"),
+	             (spec->tlspeek ? "peeking" : ""),
 	             (spec->natengine ? spec->natengine : cbuf)) < 0) {
 		s = NULL;
 	}

opts.h

@@ -39,6 +39,7 @@
 typedef struct proxyspec {
 	unsigned int ssl : 1;
 	unsigned int http : 1;
+	unsigned int tlspeek: 1;
 	struct sockaddr_storage listen_addr;
 	socklen_t listen_addrlen;
 	/* connect_addr and connect_addrlen are set: static mode;

pxyconn.c

@@ -128,6 +128,8 @@ typedef struct pxy_conn_ctx {
 	unsigned int ocsp_denied : 1;                /* 1 if OCSP was denied */
 	unsigned int enomem : 1;                       /* 1 if out of memory */
 	unsigned int sni_peek_retries : 6;       /* max 64 SNI parse retries */
+	unsigned int looking_for_client_hello : 1; /* 1 if waiting for hello */
+	unsigned int pending_ssl_upgrade : 1; /* 1 if ssl upgrade in progress */
 
 	/* server name indicated by client in SNI TLS extension */
 	char *sni;
@@ -198,6 +200,10 @@ pxy_conn_ctx_new(proxyspec_t *spec, opts_t *opts,
 	memset(ctx, 0, sizeof(pxy_conn_ctx_t));
 	ctx->spec = spec;
 	ctx->opts = opts;
+	ctx->looking_for_client_hello = spec->tlspeek;
+	if (OPTS_DEBUG(opts)) {
+		log_dbg_printf("looking status is %d\n", ctx->looking_for_client_hello);
+	}
 	ctx->fd = fd;
 	ctx->thridx = pxy_thrmgr_attach(thrmgr, &ctx->evbase, &ctx->dnsbase);
 	ctx->thrmgr = thrmgr;
@@ -1505,6 +1511,50 @@ deny:
 	}
 }
 
+int
+pxy_conn_check_and_upgrade(pxy_conn_ctx_t *ctx)
+{
+	struct evbuffer *inbuf;
+	struct evbuffer_iovec vec_out[1];
+	if (OPTS_DEBUG(ctx->opts)) {
+		log_dbg_printf("Checking for a client hello\n");
+	}
+	/* peek the buffer */
+	inbuf = bufferevent_get_input(ctx->src.bev);
+	if(evbuffer_peek(inbuf, 1024, 0, vec_out, 1)) {
+		if(ssl_tls_clienthello_identify(vec_out->iov_base, &(vec_out->iov_len))) {
+			if (OPTS_DEBUG(ctx->opts)) {
+				log_dbg_printf("Found a clienthello in midstream\n");
+			}
+			ctx->dst.ssl = pxy_dstssl_create(ctx);
+			if(!ctx->dst.ssl) {
+				log_err_printf("Error creating SSL for upgrade\n");
+				return 0;
+			}
+			ctx->dst.bev = bufferevent_openssl_filter_new(ctx->evbase, ctx->dst.bev, ctx->dst.ssl, BUFFEREVENT_SSL_CONNECTING, 0);
+			bufferevent_setcb(ctx->dst.bev, pxy_bev_readcb, pxy_bev_writecb, pxy_bev_eventcb, ctx);
+			bufferevent_enable(ctx->dst.bev, EV_READ|EV_WRITE);
+			if(!ctx->dst.bev) {
+				return 0;
+			}
+			if( OPTS_DEBUG(ctx->opts)) {
+				log_err_printf("Replaced dst bufferevent, new one is %p\n", ctx->dst.bev);
+			}
+
+			ctx->spec->ssl = 1;
+			ctx->looking_for_client_hello = 0;
+			ctx->pending_ssl_upgrade = 1;
+			return 1;
+		} else {
+			if (OPTS_DEBUG(ctx->opts)) {
+				log_dbg_printf("checked buffer, no client hello found\n");
+			}
+			return 0;
+		}
+	}
+	return 0;
+}
+
 void
 pxy_conn_terminate_free(pxy_conn_ctx_t *ctx)
 {
@@ -1544,6 +1594,12 @@ pxy_bev_readcb(struct bufferevent *bev, void *arg)
 		exit(EXIT_FAILURE);
 	}
 
+	if(ctx->looking_for_client_hello) {
+		if(pxy_conn_check_and_upgrade(ctx)) {
+			return;
+		}
+	}
+
 	struct evbuffer *inbuf = bufferevent_get_input(bev);
 	if (other->closed) {
 		evbuffer_drain(inbuf, evbuffer_get_length(inbuf));
@@ -1772,8 +1828,21 @@ pxy_bev_eventcb(struct bufferevent *bev, short events, void *arg)
 				return;
 			}
 		}
-		ctx->src.bev = pxy_bufferevent_setup(ctx, ctx->fd,
-		                                     ctx->src.ssl);
+		if(ctx->pending_ssl_upgrade) {
+			if (OPTS_DEBUG(ctx->opts)) {
+				log_dbg_printf("completing ssl upgrade\n");
+			}
+			ctx->src.bev = bufferevent_openssl_filter_new(ctx->evbase,
+			                               ctx->src.bev, ctx->src.ssl,
+			        BUFFEREVENT_SSL_ACCEPTING, BEV_OPT_DEFER_CALLBACKS);
+			bufferevent_setcb(ctx->src.bev, pxy_bev_readcb,
+			                  pxy_bev_writecb, pxy_bev_eventcb, ctx);
+			bufferevent_enable(ctx->src.bev, EV_READ|EV_WRITE);
+			ctx->pending_ssl_upgrade = 0;
+		} else {
+			ctx->src.bev = pxy_bufferevent_setup(ctx, ctx->fd,
+			                                     ctx->src.ssl);
+		}
 		if (!ctx->src.bev) {
 			if (ctx->src.ssl) {
 				SSL_free(ctx->src.ssl);

ssl.c

@@ -1902,6 +1902,88 @@ out:
 	DBG_printf("%zd bytes unparsed\n", n);
 	return servername;
 }
+
+int
+ssl_tls_clienthello_identify(const unsigned char *buf, ssize_t *sz)
+{
+#ifdef DEBUG_SNI_PARSER
+#define DBG_printf(...) log_dbg_printf("SNI Parser: " __VA_ARGS__)
+#else /* !DEBUG_SNI_PARSER */
+#define DBG_printf(...) 
+#endif /* !DEBUG_SNI_PARSER */
+	const unsigned char *p = buf;
+	ssize_t n = *sz;
+
+	DBG_printf("buffer length %zd\n", n);
+
+	if (n < 1) {
+		*sz = -1;
+		goto out2;
+	}
+	DBG_printf("byte 0: %02x\n", *p);
+	/* first byte 0x80, third byte 0x01 is SSLv2 clientHello;
+	 * first byte 0x22, second byte 0x03 is SSLv3/TLSv1.x clientHello */
+	if (*p != 22) /* record type: handshake protocol */
+		goto out2;
+	p++; n--;
+
+	if (n < 2) {
+		*sz = -1;
+		goto out2;
+	}
+	DBG_printf("version: %02x %02x\n", p[0], p[1]);
+	if (p[0] != 3)
+		goto out2;
+	p += 2; n -= 2;
+
+	if (n < 2) {
+		*sz = -1;
+		goto out2;
+	}
+	DBG_printf("length: %02x %02x\n", p[0], p[1]);
+#ifdef DEBUG_SNI_PARSER
+	ssize_t recordlen = p[1] + (p[0] << 8);
+	DBG_printf("recordlen=%zd\n", recordlen);
+#endif /* DEBUG_SNI_PARSER */
+	p += 2; n -= 2;
+
+	if (n < 1) {
+		*sz = -1;
+		goto out2;
+	}
+	DBG_printf("message type: %i\n", *p);
+	if (*p != 1) /* message type: ClientHello */
+		goto out2;
+	p++; n--;
+
+	if (n < 3) {
+		*sz = -1;
+		goto out2;
+	}
+	DBG_printf("message len: %02x %02x %02x\n", p[0], p[1], p[2]);
+	ssize_t msglen = p[2] + (p[1] << 8) + (p[0] << 16);
+	DBG_printf("msglen=%zd\n", msglen);
+	if (msglen < 4)
+		goto out2;
+	p += 3; n -= 3;
+
+	if (n < msglen) {
+		*sz = -1;
+		goto out2;
+	}
+	n = msglen; /* only parse first message */
+
+	if (n < 2)
+		goto out2;
+	DBG_printf("clienthello version %02x %02x\n", p[0], p[1]);
+	if (p[0] != 3)
+		goto out2;
+	p += 2; n -= 2;
+	return 1;
+out2:
+	DBG_printf("%zd bytes unparsed\n", n);
+	return 0;
+}
 #endif /* !OPENSSL_NO_TLSEXT */
 
 /* vim: set noet ft=c: */

ssl.h

@@ -167,6 +167,8 @@ int ssl_is_ocspreq(const unsigned char *, size_t) NONNULL(1) WUNRES;
 #ifndef OPENSSL_NO_TLSEXT
 char * ssl_tls_clienthello_parse_sni(const unsigned char *, ssize_t *)
        NONNULL(1,2) MALLOC;
+int ssl_tls_clienthello_identify(const unsigned char *, ssize_t *)
+       NONNULL(1,2);
 #endif /* !OPENSSL_NO_TLSEXT */
 int ssl_dnsname_match(const char *, size_t, const char *, size_t)
     NONNULL(1,3) WUNRES;

sslsplit.1

@@ -332,6 +332,9 @@ SNI DNS lookup):
 .br
 \fBtcp\fP   \fIlistenaddr port\fP
 [\fInat-engine\fP|\fIfwdaddr port\fP]
+.br
+\fBgenericstarttls\fP \fIlistenaddr port\fP
+[\fInat-engine\fP|\fIfwdaddr port\fP]
 .ad
 .TP
 \fBhttps\fP
@@ -350,6 +353,11 @@ the removal of HPKP, HSTS and Alternate Protocol response headers.
 Plain TCP connection without SSL/TLS and without any lower level protocol
 decoding; decrypted connection content is treated as opaque stream of bytes
 and not modified.
+.TP
+\fBgenericstarttls\fP
+Plain TCP connection until an SSL client hello appears in the byte stream;
+then starts SSL/TLS interception.
+
 .TP
 .I listenaddr port
 IPv4 or IPv6 address and port or service name to listen on.  This is the