Fix handling of the local address in shell commands

Without this fix, using on-establish/disestablish/verify would cause a strange
zero port when a bind with a random port was used, and a segmentation fault with
dynamic binds.

4 files changed, 46 insertions, 8 deletions

diff --git a/src/fastd.c b/src/fastd.c
index 3c3d130..d82589e 100644
--- a/src/fastd.c
+++ b/src/fastd.c
@@ -261,13 +261,33 @@ static int bind_socket(fastd_context_t *ctx, const fastd_bind_address_t *addr, b
 	if (warn) {
 		if (addr->bindtodev)
 			pr_warn(ctx, "unable to bind to %B on `%s'", &addr->addr, addr->bindtodev);
-                else
+		else
 			pr_warn(ctx, "unable to bind to %B", &addr->addr);
 	}
 
 	return -1;
 }
 
+static bool set_bound_address(fastd_context_t *ctx, fastd_socket_t *sock) {
+	fastd_peer_address_t addr = {};
+	socklen_t len = sizeof(addr);
+
+	if (getsockname(sock->fd, &addr.sa, &len) < 0) {
+		pr_error_errno(ctx, "getsockname");
+		return false;
+	}
+
+	if (len > sizeof(addr)) {
+		pr_error(ctx, "getsockname: got strange long address");
+		return false;
+	}
+
+	sock->bound_addr = calloc(1, sizeof(addr));
+	*sock->bound_addr = addr;
+
+	return true;
+}
+
 static bool bind_sockets(fastd_context_t *ctx) {
 	unsigned i;
 
@@ -278,10 +298,15 @@ static bool bind_sockets(fastd_context_t *ctx) {
 		ctx->socks[i].fd = bind_socket(ctx, ctx->socks[i].addr, ctx->socks[i].fd < -1);
 
 		if (ctx->socks[i].fd >= 0) {
+			if (!set_bound_address(ctx, &ctx->socks[i])) {
+				fastd_socket_close(ctx, &ctx->socks[i]);
+				continue;
+			}
+
 			if (ctx->socks[i].addr->bindtodev)
-				pr_info(ctx, "successfully bound to %B on `%s'", &ctx->socks[i].addr->addr, ctx->socks[i].addr->bindtodev);
+				pr_info(ctx, "successfully bound to %B on `%s'", ctx->socks[i].bound_addr, ctx->socks[i].addr->bindtodev);
 			else
-				pr_info(ctx, "successfully bound to %B", &ctx->socks[i].addr->addr);
+				pr_info(ctx, "successfully bound to %B", ctx->socks[i].bound_addr);
 		}
 	}
 
@@ -302,8 +327,15 @@ fastd_socket_t* fastd_socket_open(fastd_context_t *ctx, fastd_peer_t *peer, int
 
 	sock->fd = fd;
 	sock->addr = NULL;
+	sock->bound_addr = NULL;
 	sock->peer = peer;
 
+	if (!set_bound_address(ctx, sock)) {
+		fastd_socket_close(ctx, sock);
+		free(sock);
+		return NULL;
+	}
+
 	return sock;
 }
 
@@ -799,7 +831,7 @@ static void handle_socket(fastd_context_t *ctx, fastd_socket_t *sock) {
 
 	fastd_peer_address_t recvaddr;
 	socklen_t recvaddrlen = sizeof(recvaddr);
-			
+
 	ssize_t len = recvfrom(sock->fd, buffer.data, buffer.len, 0, (struct sockaddr*)&recvaddr, &recvaddrlen);
 	if (len <= 0) {
 		if (len < 0 && errno != EINTR)
diff --git a/src/fastd.h b/src/fastd.h
index 9b1191a..9736e08 100644
--- a/src/fastd.h
+++ b/src/fastd.h
@@ -142,6 +142,7 @@ struct fastd_bind_address {
 struct fastd_socket {
 	int fd;
 	const fastd_bind_address_t *addr;
+	fastd_peer_address_t *bound_addr;
 	fastd_peer_t *peer;
 };
 
@@ -458,6 +459,11 @@ static inline void fastd_socket_close(fastd_context_t *ctx, fastd_socket_t *sock
 
 		sock->fd = -2;
 	}
+
+	if (sock->bound_addr) {
+		free(sock->bound_addr);
+		sock->bound_addr = NULL;
+	}
 }
 
 static inline bool timespec_after(const struct timespec *tp1, const struct timespec *tp2) {
diff --git a/src/peer.c b/src/peer.c
index 55f0467..f4d62e3 100644
--- a/src/peer.c
+++ b/src/peer.c
@@ -36,14 +36,14 @@ static inline void on_establish(fastd_context_t *ctx, const fastd_peer_t *peer)
 	if (!ctx->conf->on_establish)
 		return;
 
-	fastd_shell_exec(ctx, ctx->conf->on_establish, ctx->conf->on_establish_dir, peer, &peer->sock->addr->addr, &peer->address, NULL);
+	fastd_shell_exec(ctx, ctx->conf->on_establish, ctx->conf->on_establish_dir, peer, peer->sock->bound_addr, &peer->address, NULL);
 }
 
 static inline void on_disestablish(fastd_context_t *ctx, const fastd_peer_t *peer) {
 	if (!ctx->conf->on_disestablish)
 		return;
 
-	fastd_shell_exec(ctx, ctx->conf->on_disestablish, ctx->conf->on_disestablish_dir, peer, &peer->sock->addr->addr, &peer->address, NULL);
+	fastd_shell_exec(ctx, ctx->conf->on_disestablish, ctx->conf->on_disestablish_dir, peer, peer->sock->bound_addr, &peer->address, NULL);
 }
 
 static inline void free_socket(fastd_context_t *ctx, fastd_peer_t *peer) {
diff --git a/src/protocol_ec25519_fhmqvc.c b/src/protocol_ec25519_fhmqvc.c
index eea95e4..d0dad5b 100644
--- a/src/protocol_ec25519_fhmqvc.c
+++ b/src/protocol_ec25519_fhmqvc.c
@@ -627,7 +627,7 @@ static inline fastd_peer_t* add_temporary(fastd_context_t *ctx, fastd_socket_t *
 	/* Ugly hack */
 	peer->protocol_state->last_serial--;
 
-	if (!fastd_peer_verify_temporary(ctx, peer, &sock->addr->addr, address)) {
+	if (!fastd_peer_verify_temporary(ctx, peer, sock->bound_addr, address)) {
 		pr_debug(ctx, "ignoring handshake from %P[%I] (verification failed)", peer, address);
 		fastd_peer_delete(ctx, peer);
 		return NULL;
@@ -674,7 +674,7 @@ static void protocol_handshake_handle(fastd_context_t *ctx, fastd_socket_t *sock
 	}
 
 	if (fastd_peer_is_temporary(peer) && !temporary_added) {
-		if (!fastd_peer_verify_temporary(ctx, peer, &sock->addr->addr, address)) {
+		if (!fastd_peer_verify_temporary(ctx, peer, sock->bound_addr, address)) {
 			pr_debug(ctx, "ignoring handshake from %P[%I] (verification failed)", peer, address);
 			return;
 		}