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[0.1] Reject offer_amount of 0 as invalid per BOLT 12 #4487

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Merged
TheBlueMatt merged 1 commit into from
Mar 17, 2026
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[0.1] Reject offer_amount of 0 as invalid per BOLT 12 #4487

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65 changes: 64 additions & 1 deletion lightning/src/offers/offer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -382,6 +382,9 @@ macro_rules! offer_builder_methods { (
pub fn build($($self_mut)* $self: $self_type) -> Result<Offer, Bolt12SemanticError> {
match $self.offer.amount {
Some(Amount::Bitcoin { amount_msats }) => {
if amount_msats == 0 {
$self.offer.amount = None;
}
Comment on lines +385 to +387

@vincenzopalazzo vincenzopalazzo Mar 17, 2026

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I am wondering if this is something that we want to do or return a Bolt12SemanticError::InvalidAmount from an API point of view?

@TheBlueMatt TheBlueMatt Mar 17, 2026

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Its an API change in the public API. IMO we should strongly avoid backporting API changes.

@vincenzopalazzo vincenzopalazzo Mar 17, 2026

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Its an API change in the public API. IMO we should strongly avoid backporting API changes.

Cool :) I was just pointing it out to make sure that we were not introducing it by mistake!

if amount_msats > MAX_VALUE_MSAT {
return Err(Bolt12SemanticError::InvalidAmount);
}
Expand Down Expand Up @@ -1158,11 +1161,12 @@ impl TryFrom<FullOfferTlvStream> for OfferContents {

let amount = match (currency, amount) {
(None, None) => None,
(None, Some(amount_msats)) if amount_msats > MAX_VALUE_MSAT => {
(None, Some(amount_msats)) if amount_msats == 0 || amount_msats > MAX_VALUE_MSAT => {
return Err(Bolt12SemanticError::InvalidAmount);
},
(None, Some(amount_msats)) => Some(Amount::Bitcoin { amount_msats }),
(Some(_), None) => return Err(Bolt12SemanticError::MissingAmount),
(Some(_), Some(0)) => return Err(Bolt12SemanticError::InvalidAmount),
(Some(iso4217_code), Some(amount)) => Some(Amount::Currency { iso4217_code, amount }),
};

Expand Down Expand Up @@ -1515,6 +1519,12 @@ mod tests {
Ok(_) => panic!("expected error"),
Err(e) => assert_eq!(e, Bolt12SemanticError::InvalidAmount),
}

// An amount of 0 is rejected per BOLT 12, so we map it to `None` instead.
match OfferBuilder::new(pubkey(42)).amount_msats(0).build() {
Ok(offer) => assert_eq!(offer.amount(), None),
Err(_) => panic!("expected offer"),
}
}

#[test]
Expand Down Expand Up @@ -1764,6 +1774,59 @@ mod tests {
Ok(_) => panic!("expected error"),
Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)),
}

// An offer with amount=0 must be rejected per BOLT 12.
let mut tlv_stream = offer.as_tlv_stream();
tlv_stream.0.amount = Some(0);
tlv_stream.0.currency = None;

let mut encoded_offer = Vec::new();
tlv_stream.write(&mut encoded_offer).unwrap();

match Offer::try_from(encoded_offer) {
Ok(_) => panic!("expected error"),
Err(e) => assert_eq!(
e,
Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)
),
}

// An offer with amount=0 and a currency must also be rejected.
let mut tlv_stream = offer.as_tlv_stream();
tlv_stream.0.amount = Some(0);
tlv_stream.0.currency = Some(b"USD");

let mut encoded_offer = Vec::new();
tlv_stream.write(&mut encoded_offer).unwrap();

match Offer::try_from(encoded_offer) {
Ok(_) => panic!("expected error"),
Err(e) => assert_eq!(
e,
Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)
),
}

// BOLT 12 test vectors: verify rejection of offers with amount=0 from their
// bech32 encoding (see bolt12/offers-test.json).
match "lno1pqqq5qqkyyp4he0fg7pqje62jmnq78cr0ashv4q06qql58tyd9rhp3t2wuyugtq".parse::<Offer>()
{
Ok(_) => panic!("expected error"),
Err(e) => assert_eq!(
e,
Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)
),
}

match "lno1qcp4256ypqqq5qqkyyp4he0fg7pqje62jmnq78cr0ashv4q06qql58tyd9rhp3t2wuyugtq"
.parse::<Offer>()
{
Ok(_) => panic!("expected error"),
Err(e) => assert_eq!(
e,
Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)
),
}
}

#[test]
Expand Down
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