core-lightning/wire/fromwire.c

#include "utils.h"
#include "wire.h"
#include <bitcoin/preimage.h>
#include <bitcoin/pubkey.h>
#include <bitcoin/shadouble.h>
#include <ccan/build_assert/build_assert.h>
#include <ccan/endian/endian.h>
#include <ccan/mem/mem.h>
#include <ccan/tal/str/str.h>
#include <type_to_string.h>

/* Sets *cursor to NULL and returns NULL when extraction fails. */
static const void *fail_pull(const u8 **cursor, size_t *max)
{
	*cursor = NULL;
	*max = 0;
	return NULL;
}

const u8 *fromwire(const u8 **cursor, size_t *max, void *copy, size_t n)
{
	const u8 *p = *cursor;

	if (*max < n) {
		/* Just make sure we don't leak uninitialized mem! */
		if (copy)
			memset(copy, 0, n);
		return fail_pull(cursor, max);
	}
	*cursor += n;
	*max -= n;
	if (copy)
		memcpy(copy, p, n);
	return memcheck(p, n);
}

int fromwire_peektype(const u8 *cursor)
{
	be16 be_type;
	size_t max = tal_count(cursor);

	fromwire(&cursor, &max, &be_type, sizeof(be_type));
	if (!cursor)
		return -1;
	return be16_to_cpu(be_type);
}

u8 fromwire_u8(const u8 **cursor, size_t *max)
{
	u8 ret;

	if (!fromwire(cursor, max, &ret, sizeof(ret)))
		return 0;
	return ret;
}

u16 fromwire_u16(const u8 **cursor, size_t *max)
{
	be16 ret;

	if (!fromwire(cursor, max, &ret, sizeof(ret)))
		return 0;
	return be16_to_cpu(ret);
}

u32 fromwire_u32(const u8 **cursor, size_t *max)
{
	be32 ret;

	if (!fromwire(cursor, max, &ret, sizeof(ret)))
		return 0;
	return be32_to_cpu(ret);
}

u64 fromwire_u64(const u8 **cursor, size_t *max)
{
	be64 ret;

	if (!fromwire(cursor, max, &ret, sizeof(ret)))
		return 0;
	return be64_to_cpu(ret);
}

bool fromwire_bool(const u8 **cursor, size_t *max)
{
	u8 ret;

	if (!fromwire(cursor, max, &ret, sizeof(ret)))
		return false;
	if (ret != 0 && ret != 1)
		fail_pull(cursor, max);
	return ret;
}

void fromwire_pubkey(const u8 **cursor, size_t *max, struct pubkey *pubkey)
{
	u8 der[PUBKEY_DER_LEN];

	if (!fromwire(cursor, max, der, sizeof(der)))
		return;

	/* FIXME: Handing dummy keys through here is dumb.
	 * See towire_gossip_resolve_channel_reply --RR */
	if (!memeqzero(der, sizeof(der))
	    && !pubkey_from_der(der, sizeof(der), pubkey))
		fail_pull(cursor, max);
}

void fromwire_privkey(const u8 **cursor, size_t *max, struct privkey *privkey)
{
	fromwire(cursor, max, privkey->secret, sizeof(privkey->secret));
}

void fromwire_secp256k1_ecdsa_signature(const u8 **cursor,
				size_t *max, secp256k1_ecdsa_signature *sig)
{
	u8 compact[64];

	if (!fromwire(cursor, max, compact, sizeof(compact)))
		return;

	if (secp256k1_ecdsa_signature_parse_compact(secp256k1_ctx, sig, compact)
	    != 1)
		fail_pull(cursor, max);
}

void fromwire_channel_id(const u8 **cursor, size_t *max,
			 struct channel_id *channel_id)
{
	fromwire(cursor, max, channel_id, sizeof(*channel_id));
}

void fromwire_short_channel_id(const u8 **cursor, size_t *max,
			       struct short_channel_id *short_channel_id)
{
	be32 txnum = 0;
	u8 outnum;

	short_channel_id->blocknum = fromwire_u32(cursor, max);
	/* Pulling 3 bytes off wire is tricky; they're big-endian. */
	fromwire(cursor, max, (char *)&txnum + 1, 3);
	short_channel_id->txnum = be32_to_cpu(txnum);
	fromwire(cursor, max, &outnum, 1);
	short_channel_id->outnum = outnum;
}

void fromwire_sha256(const u8 **cursor, size_t *max, struct sha256 *sha256)
{
	fromwire(cursor, max, sha256, sizeof(*sha256));
}

void fromwire_sha256_double(const u8 **cursor, size_t *max,
			    struct sha256_double *sha256d)
{
	fromwire_sha256(cursor, max, &sha256d->sha);
}

void fromwire_preimage(const u8 **cursor, size_t *max, struct preimage *preimage)
{
	fromwire(cursor, max, preimage, sizeof(*preimage));
}

void fromwire_ipv6(const u8 **cursor, size_t *max, struct ipv6 *ipv6)
{
	fromwire(cursor, max, ipv6, sizeof(*ipv6));
}

void fromwire_u8_array(const u8 **cursor, size_t *max, u8 *arr, size_t num)
{
	fromwire(cursor, max, arr, num);
}

void fromwire_pad(const u8 **cursor, size_t *max, size_t num)
{
	fromwire(cursor, max, NULL, num);
}

static char *fmt_short_channel_id(const tal_t *ctx,
				  const struct short_channel_id *id)
{
	return tal_fmt(ctx, "%u/%u/%u", id->blocknum, id->txnum, id->outnum);
}
REGISTER_TYPE_TO_STRING(short_channel_id, fmt_short_channel_id);
REGISTER_TYPE_TO_HEXSTR(channel_id);

/* BOLT #2:
 *
 * This message introduces the `channel-id` to identify the channel, which is
 * derived from the funding transaction by combining the `funding-txid` and
 * the `funding-output-index` using big-endian exclusive-OR
 * (ie. `funding-output-index` alters the last two bytes).
 */
void derive_channel_id(struct channel_id *channel_id,
		       struct sha256_double *txid, u16 txout)
{
	BUILD_ASSERT(sizeof(*channel_id) == sizeof(*txid));
	memcpy(channel_id, txid, sizeof(*channel_id));
	channel_id->id[sizeof(*channel_id)-2] ^= txout >> 8;
	channel_id->id[sizeof(*channel_id)-1] ^= txout;
}