add support for using the proxy protocol v1 when proxying too

This is symmetrical to the support for *incoming* requests.  The
new regress case uses this to proxy to itself using the proxy-protocol
v1.

Fixes #31

gmid.conf.5

@@ -11,7 +11,7 @@
 .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-.Dd June 28, 2024
+.Dd August 3, 2024
 .Dt GMID.CONF 5
 .Os
 .Sh NAME
@@ -521,6 +521,10 @@ Refer to the
 .Xr tls_config_parse_protocols 3
 function for the valid protocol string values.
 By default, both TLSv1.2 and TLSv1.3 are enabled.
+.It Ic proxy-v1
+Use the proxy protocol v1.
+If supported by the remote server, this is useful to propagate the
+information about the originating IP address and port.
 .It Ic relay-to Ar host Op Cm port Ar port
 Relay the request to the given
 .Ar host

gmid.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, 2021, 2022, 2023 Omar Polo <op@omarpolo.com>
+ * Copyright (c) 2020-2024 Omar Polo <op@omarpolo.com>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -168,6 +168,7 @@ struct proxy {
 	size_t		 keylen;
 	char		*reqca_path;
 	X509_STORE	*reqca;
+	int		 proxy;	/* use the proxy protocol */
 
 	TAILQ_ENTRY(proxy) proxies;
 };

parse.y

@@ -519,6 +519,9 @@ proxy_opt	: CERT string {
 				yyerror("invalid protocols string \"%s\"", $2);
 			free($2);
 		}
+		| PROXYV1 {
+			proxy->proxy = 1;
+		}
 		| RELAY_TO string proxy_port {
 			if (strlcpy(proxy->host, $2, sizeof(proxy->host))
 			    >= sizeof(proxy->host))

proxy.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2022, 2023 Omar Polo <op@omarpolo.com>
+ * Copyright (c) 2021-2024 Omar Polo <op@omarpolo.com>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -237,6 +237,11 @@ proxy_enqueue_req(struct client *c)
 	if (c->proxybev == NULL)
 		fatal("can't allocate bufferevent");
 
+	evb = EVBUFFER_OUTPUT(c->proxybev);
+
+	if (p->notls && p->proxy)
+		evbuffer_add(evb, c->buf.data, c->buf.len);
+
 	if (!p->notls) {
 		event_set(&c->proxybev->ev_read, c->pfd, EV_READ,
 		    proxy_tls_readcb, c->proxybev);
@@ -251,7 +256,6 @@ proxy_enqueue_req(struct client *c)
 
 	serialize_iri(&c->iri, iribuf, sizeof(iribuf));
 
-	evb = EVBUFFER_OUTPUT(c->proxybev);
 	evbuffer_add_printf(evb, "%s\r\n", iribuf);
 
 	bufferevent_enable(c->proxybev, EV_READ|EV_WRITE);
@@ -287,6 +291,40 @@ proxy_handshake(int fd, short event, void *d)
 	proxy_enqueue_req(c);
 }
 
+static ssize_t
+proxy_read_cb(struct tls *ctx, void *buf, size_t buflen, void *cb_arg)
+{
+	struct client	*c = cb_arg;
+	ssize_t		 ret;
+
+	ret = read(c->pfd, buf, buflen);
+	if (ret == -1 && errno == EAGAIN)
+		ret = TLS_WANT_POLLIN;
+	return ret;
+}
+
+static ssize_t
+proxy_write_cb(struct tls *ctx, const void *buf, size_t len, void *cb_arg)
+{
+	struct client	*c = cb_arg;
+	ssize_t		 ret;
+	size_t		 left;
+
+	while ((left = c->buf.len - c->buf.read_pos) > 0) {
+		ret = write(c->pfd, c->buf.data + c->buf.read_pos, left);
+		if (ret == -1 && errno == EAGAIN)
+			return (TLS_WANT_POLLOUT);
+		if (ret <= 0)
+			return (ret);
+		c->buf.read_pos += ret;
+	}
+
+	ret = write(c->pfd, buf, len);
+	if (ret == -1 && errno == EAGAIN)
+		ret = TLS_WANT_POLLOUT;
+	return (ret);
+}
+
 static int
 proxy_setup_tls(struct client *c)
 {
@@ -323,7 +361,8 @@ proxy_setup_tls(struct client *c)
 
 	if (*(hn = p->sni) == '\0')
 		hn = p->host;
-	if (tls_connect_socket(c->proxyctx, c->pfd, hn) == -1)
+	if (tls_connect_cbs(c->proxyctx, proxy_read_cb, proxy_write_cb, c, hn)
+	    == -1)
 		goto err;
 
 	c->proxyevset = 1;

regress/lib.sh

@@ -14,6 +14,7 @@ run_test() {
 	host="$REGRESS_HOST"
 	port=10965
 	proxy_port=10966
+	proxy=
 	config_common="log syslog off"
 	hdr=
 	body=
@@ -72,7 +73,7 @@ server "$server_name" {
 	cert "$PWD/localhost.pem"
 	key  "$PWD/localhost.key"
 	root "$PWD/testdata"
-	listen on $host port $port
+	listen on $host port $port $proxy
 	$2
 }
 EOF

regress/regress

@@ -69,6 +69,7 @@ run_test test_ipv4_addr
 run_test test_ipv6_addr need_ipv6
 run_test test_ipv6_server need_ipv6
 run_test test_high_prefork
+run_test test_proxy_protocol_v1
 
 # TODO: add test that uses only a TLSv1.2 or TLSv1.3
 # TODO: add a test that attempt to serve a non-regular file

regress/tests.sh

@@ -533,3 +533,32 @@ test_high_prefork() {
 	dont_check_server_alive=yes
 	kill "$(cat gmid.pid)" 2>/dev/null || true
 }
+
+test_proxy_protocol_v1() {
+	rm -f log
+	proxy=proxy-v1
+	gen_config '
+log access "'$PWD'/log"
+log style legacy' ''
+	set_proxy 'proxy-v1'
+	run
+
+	ggflags="-P localhost:$proxy_port -H localhost.local"
+
+	# This will generate two log entry: one for the "frontend"
+	# and one for the proxied request.  Both should have exactly
+	# the same IP and port.
+	fetch_hdr /
+	check_reply '20 text/gemini'
+
+	n=$(awk '{print $1}' log | uniq | wc -l)
+	if [ "$n" -ne 1 ]; then
+		# keep the log for post-mortem analysis
+		echo
+		echo "n is $n"
+		return 1
+	fi
+
+	rm -f log
+	return 0
+}

server.c

@@ -556,21 +556,23 @@ check_matching_certificate(X509_STORE *store, struct client *c)
 }
 
 static int
-proxy_socket(struct client *c, const char *host, const char *port)
+proxy_socket(struct client *c, struct proxy *p)
 {
 	struct addrinfo hints, *res, *res0;
 	int r, sock, save_errno;
 	const char *cause = NULL;
+	char to[NI_MAXHOST], to_port[NI_MAXSERV];
+	int err;
 
 	memset(&hints, 0, sizeof(hints));
 	hints.ai_family = AF_UNSPEC;
 	hints.ai_socktype = SOCK_STREAM;
 
 	/* XXX: asr_run? :> */
-	r = getaddrinfo(host, port, &hints, &res0);
+	r = getaddrinfo(p->host, p->port, &hints, &res0);
 	if (r != 0) {
 		log_warnx("getaddrinfo(\"%s\", \"%s\"): %s",
-		    host, port, gai_strerror(r));
+		    p->host, p->port, gai_strerror(r));
 		return -1;
 	}
 
@@ -595,10 +597,30 @@ proxy_socket(struct client *c, const char *host, const char *port)
 	}
 
 	if (sock == -1)
-		log_warn("can't connect to %s:%s: %s", host, port, cause);
+		log_warn("can't connect to %s:%s: %s", p->host, p->port, cause);
+
+	if (res && sock != -1 && p->proxy) {
+		err = getnameinfo(res->ai_addr, res->ai_addrlen,
+		    to, sizeof(to), to_port, sizeof(to_port),
+		    NI_NUMERICHOST|NI_NUMERICSERV);
+		if (err != 0) {
+			log_warnx("getnameinfo failed: %s", gai_strerror(err));
+			strlcpy(to, c->rhost, sizeof(to));
+			strlcpy(to_port, c->rserv, sizeof(to_port));
+		}
 
-	freeaddrinfo(res0);
+		r = snprintf(c->buf.data, sizeof(c->buf.data),
+		    "PROXY TCP%c %s %s %s %s\r\n",
+		    c->addr->ai_family == AF_INET ? '4' : '6',
+		    c->rhost, to, c->rserv, to_port);
+		if (r < 0 || (size_t)r >= sizeof(c->buf.data)) {
+			log_warnx("failed serialize info for the proxy protocol");
+			c->buf.data[0] = '\0';
+		} else
+			c->buf.len = r;
+	}
 
+	freeaddrinfo(res0);
 	return sock;
 }
 
@@ -618,7 +640,7 @@ apply_reverse_proxy(struct client *c)
 
 	log_debug("opening proxy connection for %s:%s", p->host, p->port);
 
-	if ((c->pfd = proxy_socket(c, p->host, p->port)) == -1) {
+	if ((c->pfd = proxy_socket(c, p)) == -1) {
 		start_reply(c, PROXY_ERROR, "proxy error");
 		return 1;
 	}