core-lightning/lightningd/hsm_control.c

#include "hsm_control.h"
#include "lightningd.h"
#include "subd.h"
#include <ccan/err/err.h>
#include <ccan/fdpass/fdpass.h>
#include <ccan/io/io.h>
#include <ccan/take/take.h>
#include <common/ecdh.h>
#include <common/json.h>
#include <common/json_helpers.h>
#include <common/jsonrpc_errors.h>
#include <common/param.h>
#include <common/status.h>
#include <common/utils.h>
#include <errno.h>
#include <hsmd/gen_hsm_wire.h>
#include <inttypes.h>
#include <lightningd/bitcoind.h>
#include <lightningd/hsm_control.h>
#include <lightningd/json.h>
#include <lightningd/jsonrpc.h>
#include <lightningd/log.h>
#include <lightningd/log_status.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <wally_bip32.h>
#include <wire/wire_sync.h>

static int hsm_get_fd(struct lightningd *ld,
		      const struct node_id *id,
		      u64 dbid,
		      int capabilities)
{
	int hsm_fd;
	u8 *msg;

	msg = towire_hsm_client_hsmfd(NULL, id, dbid, capabilities);
	if (!wire_sync_write(ld->hsm_fd, take(msg)))
		fatal("Could not write to HSM: %s", strerror(errno));

	msg = wire_sync_read(tmpctx, ld->hsm_fd);
	if (!fromwire_hsm_client_hsmfd_reply(msg))
		fatal("Bad reply from HSM: %s", tal_hex(tmpctx, msg));

	hsm_fd = fdpass_recv(ld->hsm_fd);
	if (hsm_fd < 0)
		fatal("Could not read fd from HSM: %s", strerror(errno));
	return hsm_fd;
}

int hsm_get_client_fd(struct lightningd *ld,
		      const struct node_id *id,
		      u64 dbid,
		      int capabilities)
{
	assert(dbid);

	return hsm_get_fd(ld, id, dbid, capabilities);
}

int hsm_get_global_fd(struct lightningd *ld, int capabilities)
{
	return hsm_get_fd(ld, &ld->id, 0, capabilities);
}

static unsigned int hsm_msg(struct subd *hsmd,
			    const u8 *msg, const int *fds UNUSED)
{
	/* We only expect one thing from the HSM that's not a STATUS message */
	struct node_id client_id;
	u8 *bad_msg;
	char *desc;

	if (!fromwire_hsmstatus_client_bad_request(tmpctx, msg, &client_id,
						   &desc, &bad_msg))
		fatal("Bad status message from hsmd: %s", tal_hex(tmpctx, msg));

	/* This should, of course, never happen. */
	log_broken(hsmd->log, "client %s %s (request %s)",
		   type_to_string(tmpctx, struct node_id, &client_id),
		   desc, tal_hex(tmpctx, bad_msg));
	return 0;
}

struct ext_key *hsm_init(struct lightningd *ld)
{
	u8 *msg;
	int fds[2];
	struct ext_key *bip32_base;

	/* We actually send requests synchronously: only status is async. */
	if (socketpair(AF_LOCAL, SOCK_STREAM, 0, fds) != 0)
		err(1, "Could not create hsm socketpair");

	ld->hsm = new_global_subd(ld, "lightning_hsmd",
				  hsm_wire_type_name,
				  hsm_msg,
				  take(&fds[1]), NULL);
	if (!ld->hsm)
		err(1, "Could not subd hsm");

	/* If hsm_secret is encrypted and the --encrypted-hsm startup option is
	 * not passed, don't let hsmd use the first 32 bytes of the cypher as the
	 * actual secret. */
	if (!ld->config.keypass) {
		struct stat st;
		if (stat("hsm_secret", &st) == 0 && st.st_size > 32)
			errx(1, "hsm_secret is encrypted, you need to pass the "
			        "--encrypted-hsm startup option.");
	}

	ld->hsm_fd = fds[0];
	if (!wire_sync_write(ld->hsm_fd, towire_hsm_init(tmpctx,
							 &chainparams->bip32_key_version,
							 chainparams,
							 ld->config.keypass,
							 IFDEV(ld->dev_force_privkey, NULL),
							 IFDEV(ld->dev_force_bip32_seed, NULL),
							 IFDEV(ld->dev_force_channel_secrets, NULL),
							 IFDEV(ld->dev_force_channel_secrets_shaseed, NULL))))
		err(1, "Writing init msg to hsm");

	bip32_base = tal(ld, struct ext_key);
	msg = wire_sync_read(tmpctx, ld->hsm_fd);
	if (!fromwire_hsm_init_reply(msg,
				     &ld->id, bip32_base)) {
		if (ld->config.keypass)
			errx(1, "Wrong password for encrypted hsm_secret.");
		errx(1, "HSM did not give init reply");
	}

	return bip32_base;
}

static struct command_result *json_getsharedsecret(struct command *cmd,
					   const char *buffer,
					   const jsmntok_t *obj UNNEEDED,
					   const jsmntok_t *params)
{
	struct pubkey *point;
	struct secret ss;
	struct json_stream *response;

	if (!param(cmd, buffer, params,
		   p_req("point", &param_pubkey, &point),
		   NULL))
		return command_param_failed();

	ecdh(point, &ss);
	response = json_stream_success(cmd);
	json_add_secret(response, "shared_secret", &ss);
	return command_success(cmd, response);
}

static const struct json_command getsharedsecret_command = {
	"getsharedsecret",
	"utility", /* FIXME: Or "crypto"?  */
	&json_getsharedsecret,
	"Compute the hash of the Elliptic Curve Diffie Hellman shared secret point from "
	"this node private key and an input {point}."
};
AUTODATA(json_command, &getsharedsecret_command);