hsm: Unifying the client creation and adding client capabilities

We had a number of entry points into the HSM, all with different
behavior, so this is my attempt at unifying the way we handle
clients. Every client, except master, now takes the same path entry
point to the HSM and we use capability bit flags to indicate whether
the client is allowed to execute a set of operations.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

hsmd/capabilities.h

@@ -0,0 +1,7 @@
+#ifndef LIGHTNING_HSMD_CAPABILITIES_H
+#define LIGHTNING_HSMD_CAPABILITIES_H
+
+#define HSM_CAP_ECDH 1
+#define HSM_CAP_SIGN_GOSSIP 2
+
+#endif /* LIGHTNING_HSMD_CAPABILITIES_H */

hsmd/hsm.c

@@ -25,6 +25,7 @@
 #include <common/withdraw_tx.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <hsmd/capabilities.h>
 #include <hsmd/client.h>
 #include <hsmd/gen_hsm_client_wire.h>
 #include <hsmd/gen_hsm_wire.h>
@@ -51,6 +52,9 @@ struct client {
 
 	struct pubkey id;
 	struct io_plan *(*handle)(struct io_conn *, struct daemon_conn *);
+
+	/* What is this client allowed to ask for? */
+	u64 capabilities;
 };
 
 static void node_key(struct privkey *node_privkey, struct pubkey *node_id)
@@ -77,6 +81,7 @@ static void node_key(struct privkey *node_privkey, struct pubkey *node_id)
 
 static struct client *new_client(struct daemon_conn *master,
 				 const struct pubkey *id,
+				 const u64 capabilities,
 				 struct io_plan *(*handle)(struct io_conn *,
 							   struct daemon_conn *),
 				 int fd)
@@ -85,6 +90,7 @@ static struct client *new_client(struct daemon_conn *master,
 	c->id = *id;
 	c->handle = handle;
 	c->master = master;
+	c->capabilities = capabilities;
 	daemon_conn_init(c, &c->dc, fd, handle, NULL);
 
 	/* Free the connection if we exit everything. */
@@ -216,6 +222,62 @@ static struct io_plan *handle_channel_update_sig(struct io_conn *conn,
 	return daemon_conn_read_next(conn, dc);
 }
 
+static bool check_client_capabilities(struct client *client,
+				      enum hsm_client_wire_type t)
+{
+	switch (t) {
+	case WIRE_HSM_ECDH_REQ:
+		return (client->capabilities & HSM_CAP_ECDH) != 0;
+
+	case WIRE_HSM_CANNOUNCEMENT_SIG_REQ:
+	case WIRE_HSM_CUPDATE_SIG_REQ:
+		return (client->capabilities & HSM_CAP_SIGN_GOSSIP) != 0;
+
+	case WIRE_HSM_ECDH_RESP:
+	case WIRE_HSM_CANNOUNCEMENT_SIG_REPLY:
+	case WIRE_HSM_CUPDATE_SIG_REPLY:
+		break;
+	}
+	return false;
+}
+
+static struct io_plan *handle_client(struct io_conn *conn,
+				     struct daemon_conn *dc)
+{
+	struct client *c = container_of(dc, struct client, dc);
+	enum hsm_client_wire_type t = fromwire_peektype(dc->msg_in);
+
+	/* Before we do anything else, is this client allowed to do
+	 * what he asks for? */
+	if (!check_client_capabilities(c, t)) {
+		daemon_conn_send(c->master,
+				 take(towire_hsmstatus_client_bad_request(
+				     c, &c->id, dc->msg_in)));
+		return io_close(conn);
+	}
+
+	/* Now actually go and do what the client asked for */
+	switch (t) {
+	case WIRE_HSM_ECDH_REQ:
+		return handle_ecdh(conn, dc);
+	case WIRE_HSM_CANNOUNCEMENT_SIG_REQ:
+		return handle_cannouncement_sig(conn, dc);
+	case WIRE_HSM_CUPDATE_SIG_REQ:
+		return handle_channel_update_sig(conn, dc);
+
+	case WIRE_HSM_ECDH_RESP:
+	case WIRE_HSM_CANNOUNCEMENT_SIG_REPLY:
+	case WIRE_HSM_CUPDATE_SIG_REPLY:
+		break;
+	}
+
+	daemon_conn_send(c->master,
+			 take(towire_hsmstatus_client_bad_request(c,
+								  &c->id,
+								  dc->msg_in)));
+	return io_close(conn);
+}
+
 static struct io_plan *handle_channeld(struct io_conn *conn,
 				       struct daemon_conn *dc)
 {
@@ -418,6 +480,25 @@ static void init_hsm(struct daemon_conn *master, const u8 *msg)
 	send_init_response(master);
 }
 
+static void pass_client_hsmfd(struct daemon_conn *master, const u8 *msg)
+{
+	int fds[2];
+	u64 capabilities;
+	struct pubkey id;
+
+	if (!fromwire_hsmctl_client_hsmfd(msg, NULL, &id, &capabilities))
+		master_badmsg(WIRE_HSMCTL_CLIENT_HSMFD, msg);
+
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) != 0)
+		status_failed(STATUS_FAIL_INTERNAL_ERROR, "creating fds: %s", strerror(errno));
+
+	new_client(master, &id, capabilities, handle_client, fds[0]);
+	daemon_conn_send(master,
+			 take(towire_hsmctl_client_hsmfd_reply(master)));
+	daemon_conn_send_fd(master, fds[1]);
+}
+
+
 static void pass_hsmfd_ecdh(struct daemon_conn *master, const u8 *msg)
 {
 	int fds[2];
@@ -432,7 +513,7 @@ static void pass_hsmfd_ecdh(struct daemon_conn *master, const u8 *msg)
 
 	/* This is gossipd, so we use our own id */
 	node_key(NULL, &id);
-	new_client(master, &id, handle_ecdh, fds[0]);
+	new_client(master, &id, HSM_CAP_ECDH, handle_ecdh, fds[0]);
 	daemon_conn_send(master,
 			 take(towire_hsmctl_hsmfd_ecdh_fd_reply(master)));
 	daemon_conn_send_fd(master, fds[1]);
@@ -451,7 +532,7 @@ static void pass_hsmfd_channeld(struct daemon_conn *master, const u8 *msg)
 		status_failed(STATUS_FAIL_INTERNAL_ERROR,
 			      "creating fds: %s", strerror(errno));
 
-	new_client(master, &id, handle_channeld, fds[0]);
+	new_client(master, &id, HSM_CAP_ECDH | HSM_CAP_SIGN_GOSSIP, handle_channeld, fds[0]);
 	daemon_conn_send(master,
 			 take(towire_hsmctl_hsmfd_channeld_reply(master)));
 	daemon_conn_send_fd(master, fds[1]);
@@ -661,6 +742,9 @@ static struct io_plan *control_received_req(struct io_conn *conn,
 	case WIRE_HSMCTL_INIT:
 		init_hsm(master, master->msg_in);
 		return daemon_conn_read_next(conn, master);
+	case WIRE_HSMCTL_CLIENT_HSMFD:
+		pass_client_hsmfd(master, master->msg_in);
+		return daemon_conn_read_next(conn, master);
 	case WIRE_HSMCTL_HSMFD_ECDH:
 		pass_hsmfd_ecdh(master, master->msg_in);
 		return daemon_conn_read_next(conn, master);
@@ -684,6 +768,7 @@ static struct io_plan *control_received_req(struct io_conn *conn,
 		return daemon_conn_read_next(conn, master);
 
 	case WIRE_HSMCTL_INIT_REPLY:
+	case WIRE_HSMCTL_CLIENT_HSMFD_REPLY:
 	case WIRE_HSMCTL_HSMFD_ECDH_FD_REPLY:
 	case WIRE_HSMCTL_HSMFD_CHANNELD_REPLY:
 	case WIRE_HSMCTL_SIGN_FUNDING_REPLY:

hsmd/hsm_wire.csv

@@ -14,6 +14,14 @@ hsmctl_init_reply,,node_id,struct pubkey
 hsmctl_init_reply,,peer_seed,struct secret
 hsmctl_init_reply,,bip32,struct ext_key
 
+# Get a new HSM FD, with the specified capabilities
+hsmctl_client_hsmfd,9
+hsmctl_client_hsmfd,,pubkey,struct pubkey # Which identity to report for requests
+hsmctl_client_hsmfd,,capabilities,u64
+
+# No content, just an fd.
+hsmctl_client_hsmfd_reply,109
+
 # ECDH returns an fd (for gossipd to do handshake)
 hsmctl_hsmfd_ecdh,3