Fail channel in case of high-S remote signature reception #807
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cfromknecht
reviewed
Oct 26, 2020
02-peer-protocol.md
Outdated
| @@ -388,7 +388,8 @@ The sender MUST set: | |||
| - `signature` to the valid signature, using its `funding_pubkey` for the initial commitment transaction, as defined in [BOLT #3](03-transactions.md#commitment-transaction). | |||
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| The recipient: | |||
| - if `signature` is incorrect: | |||
| - if `signature` is incorrect OR non-compliant with LOW-S-standard rule<sup>[LOWS](https://github.com/bitcoin/bitcoin/pull/6769)</sup>: | |||
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Ack. Sometimes you just gotta repeat yourself. |
See CVE-2020-26895 for context.
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Updated c93d772 with nit fix. |
t-bast
reviewed
Nov 2, 2020
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Merging according to spec meeting decision. |
SomberNight
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May 27, 2024
The low-S rule for ecdsa signatures is mandated by Bitcoin Core policy/standardness (though not by consensus). If we get signatures from untrusted sources, we should mandate they obey the policy rules. (e.g. from LN peers) Note that we normalize the signatures in the sig format conversion methods (DER <-> (r,s) <-> sig64). The BOLTs treat high-S signatures as invalid, and this changes our behaviour to that. (previously we would silently normalize the S value) see bitcoin/bitcoin#6769 see lightning/bolts#807
ahmedbodi
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Aug 28, 2024
The low-S rule for ecdsa signatures is mandated by Bitcoin Core policy/standardness (though not by consensus). If we get signatures from untrusted sources, we should mandate they obey the policy rules. (e.g. from LN peers) Note that we normalize the signatures in the sig format conversion methods (DER <-> (r,s) <-> sig64). The BOLTs treat high-S signatures as invalid, and this changes our behaviour to that. (previously we would silently normalize the S value) see bitcoin/bitcoin#6769 see lightning/bolts#807
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See CVE-2020-26895 for context.
Note, the requirement is on every remote signature reception instead of a global note. We make this a reception requirement, which doesn't prevent implementation to harden by normalizing to low-S at transactions broadcasting.