BOLT12: don't allow zero-amount offers.

And enhance some of our quotes to use `...` at the start to link them.
As they were, we didn't notice when a new requirement appeared in the
middle.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Author: rustyrussell

Makefile

@@ -33,7 +33,7 @@ CCANDIR := ccan
 
 # Where we keep the BOLT RFCs
 BOLTDIR := ../bolts/
-DEFAULT_BOLTVERSION := 7153bed9705d7493065d9b818d25b282ef0a7c5e
+DEFAULT_BOLTVERSION := 311119388a46dfa859da3d2eda0ca836cfc5f078
 # Can be overridden on cmdline.
 BOLTVERSION := $(DEFAULT_BOLTVERSION)
 

common/bolt12.c

@@ -227,7 +227,17 @@ struct tlv_offer *offer_decode(const tal_t *ctx,
 	}
 
 	/* BOLT #12:
-	 *
+	 *...
+	 *   - if `offer_amount` is set and is not greater than zero:
+	 *     - MUST NOT respond to the offer.
+	 */
+	if (offer->offer_amount && *offer->offer_amount == 0) {
+		*fail = tal_strdup(ctx, "Offer contains a zero amount");
+		return tal_free(offer);
+	}
+
+	/* BOLT #12:
+	 *...
 	 *   - if `offer_currency` is set and `offer_amount` is not set:
 	 *     - MUST NOT respond to the offer.
 	 */
@@ -237,7 +247,7 @@ struct tlv_offer *offer_decode(const tal_t *ctx,
 	}
 
 	/* BOLT #12:
-	 *
+	 *...
 	 *   - if neither `offer_issuer_id` nor `offer_paths` are set:
 	 *     - MUST NOT respond to the offer.
 	 */
@@ -247,6 +257,7 @@ struct tlv_offer *offer_decode(const tal_t *ctx,
 	}
 
 	/* BOLT #12:
+	 *...
 	 *   - if `num_hops` is 0 in any `blinded_path` in `offer_paths`:
 	 *     - MUST NOT respond to the offer.
 	 */

common/test/run-bolt12-encode-test.c

@@ -429,6 +429,8 @@ int main(int argc, char *argv[])
 	/* BOLT #12:
 	 *   - if `offer_amount` is set and `offer_description` is not set:
 	 *     - MUST NOT respond to the offer.
+	 *   - if `offer_amount` is set and is not greater than zero:
+	 *     - MUST NOT respond to the offer.
 	 *   - if `offer_currency` is set and `offer_amount` is not set:
 	 *     - MUST NOT respond to the offer.
 	 *   - if neither `offer_issuer_id` nor `offer_paths` are set:
@@ -438,8 +440,18 @@ int main(int argc, char *argv[])
 	print_invalid_offer(offer, "Missing offer_description and offer_amount");
 	offer->offer_description = tal_utf8(tmpctx, "Test vectors");
 
+	offer->offer_amount = tal(offer, u64);
+	*offer->offer_amount = 0;
+	print_invalid_offer(offer, "Zero offer_amount");
+	offer->offer_amount = tal_free(offer->offer_amount);
+
 	offer->offer_currency = tal_utf8(offer, "USD");
 	print_invalid_offer(offer, "Missing offer_amount with offer_currency");
+
+	offer->offer_amount = tal(offer, u64);
+	*offer->offer_amount = 0;
+	print_invalid_offer(offer, "Zero offer_amount with currency");
+	offer->offer_amount = tal_free(offer->offer_amount);
 	offer->offer_currency = NULL;
 
 	offer->offer_issuer_id = NULL;

common/test/run-bolt12-format-string-test.c

@@ -128,6 +128,7 @@ int main(int argc, char *argv[])
 	 *     - SHOULD omit `offer_chains`, implying that bitcoin is only chain.
 	 *   - if a specific minimum `offer_amount` is required for successful payment:
 	 *     - MUST set `offer_amount` to the amount expected (per item).
+	 *     - MUST set `offer_amount` greater than zero.
 	 *     - if the currency for `offer_amount` is that of all entries in `chains`:
 	 *       - MUST specify `offer_amount` in multiples of the minimum lightning-payable unit
 	 *         (e.g. milli-satoshis for bitcoin).

devtools/bolt12-cli.c

@@ -95,6 +95,7 @@ static bool print_offer_amount(const struct bitcoin_blkid *chains,
 	/* BOLT #12:
 	 * - if a specific minimum `offer_amount` is required for successful payment:
 	 *   - MUST set `offer_amount` to the amount expected (per item).
+	 *   - MUST set `offer_amount` greater than zero.
 	 *   - if the currency for `offer_amount` is that of all entries in `chains`:
 	 *     - MUST specify `offer_amount` in multiples of the minimum lightning-payable unit
 	 *       (e.g. milli-satoshis for bitcoin).
@@ -150,6 +151,10 @@ static bool print_offer_amount(const struct bitcoin_blkid *chains,
 		       currency);
 	}
 
+	if (amount == 0) {
+		printf(" *** INVALID zero offer_amount");
+		ok = false;
+	}
 	return ok;
 }