Function get_channel_seed

tools/hsmtool.c:112–145

Taken from hsmd. */

/* Taken from hsmd. */
static void get_channel_seed(struct secret *channel_seed, struct node_id *peer_id,
                             u64 dbid, struct secret *hsm_secret)
{
	struct secret channel_base;
	u8 input[sizeof(peer_id->k) + sizeof(dbid)];
	/*~ Again, "per-peer" should be "per-channel", but Hysterical Raisins */
	const char *info = "per-peer seed";

	/*~ We use the DER encoding of the pubkey, because it's platform
	 * independent.  Since the dbid is unique, however, it's completely
	 * unnecessary, but again, existing users can't be broken. */
	/* FIXME: lnd has a nicer BIP32 method for deriving secrets which we
	 * should migrate to. */
	hkdf_sha256(&channel_base, sizeof(struct secret), NULL, 0,
	            hsm_secret, sizeof(*hsm_secret),
	            /*~ Initially, we didn't support multiple channels per
	             * peer at all: a channel had to be completely forgotten
	             * before another could exist.  That was slightly relaxed,
	             * but the phrase "peer seed" is wired into the seed
	             * generation here, so we need to keep it that way for
	             * existing clients, rather than using "channel seed". */
	             "peer seed", strlen("peer seed"));
	memcpy(input, peer_id->k, sizeof(peer_id->k));
	BUILD_ASSERT(sizeof(peer_id->k) == PUBKEY_CMPR_LEN);
	/*~ For all that talk about platform-independence, note that this
	 * field is endian-dependent!  But let's face it, little-endian won.
	 * In related news, we don't support EBCDIC or middle-endian. */
	memcpy(input + PUBKEY_CMPR_LEN, &dbid, sizeof(dbid));

	hkdf_sha256(channel_seed, sizeof(*channel_seed),
	            input, sizeof(input),
	            &channel_base, sizeof(channel_base),
	            info, strlen(info));
}

/* We detect an encrypted hsm_secret as a hsm_secret which is 73-bytes long. */
static bool hsm_secret_is_encrypted(const char *hsm_secret_path)