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psbt: validate pubkeys in MuSig2 pubnonce/partial sig deserialization
Public commit record
100/100 · Strong
What the developer wrote
Authored by tboy1337
psbt: validate pubkeys in MuSig2 pubnonce/partial sig deserialization
Add validation for pubkeys in MuSig2 pubnonce and partial signature deserialization to prevent crashes with invalid curve points.
- Validate aggregate and participant pubkeys in PSBT MuSig2 fields
- Add comprehensive test coverage for invalid pubkey rejection
- Ensure proper error handling during PSBT deserialization
✓ Specific, descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context✓ Explains rationale or failure mode✓ Mentions testing or verification✓ Names security-relevant behavior explicitly
What changed, and why it matters
This commit fixes a bug in Bitcoin Core's handling of partially signed Bitcoin transactions (PSBTs) that use the MuSig2 multi-signature scheme. Previously, when reading certain MuSig2 fields, the code accepted invalid public keys (points that are not valid on the Bitcoin elliptic curve). The fix adds checks that reject these invalid keys during deserialization, turning potential crashes or undefined behavior into clean error messages. The commit also adds test cases with deliberately bad keys to confirm they are rejected.
Recommended action
Apply the patch. Ensure all nodes or services that process untrusted PSBTs are upgraded, since malformed MuSig2 fields could previously reach code paths that assume valid public keys. Review any other MuSig2 deserialization sites for similar missing validity checks.
Security signals we found
01
Input validation gap in deserialization of cryptographic public keys
02
Potential crash or undefined behavior from invalid secp256k1 curve points
03
MuSig2 PSBT fields previously deserialized without full validity checks
04
Patch adds explicit CPubKey::IsFullyValid() checks and throws on failure
05
New negative test vectors added for invalid aggregate and participant pubkeys
Evidence from the diff
In src/psbt.h, DeserializeMuSig2ParticipantDataIdentifier now calls CPubKey::IsFullyValid() on both the aggregate pubkey and the participant pubkey immediately after constructing them from raw bytes. If either key is not a fully valid secp256k1 public key, an std::ios_base::failure is thrown. This prevents downstream code from operating on malformed curve points. The functional test data in test/functional/data/rpc_psbt.json is extended with four new invalid PSBT vectors that expect the new error strings: two for invalid participant pubkeys and two for invalid aggregate pubkeys.
Changed components
src/psbt.hBitcoin Core PSBT deserializationMuSig2 participant data identifier parsingInspect captured patch +23 / −0
diff --git a/src/psbt.h b/src/psbt.h
index 9d7fc05b..d96295ea 100644
--- a/src/psbt.h
+++ b/src/psbt.h
@@ -243,7 +243,14 @@ void DeserializeMuSig2ParticipantDataIdentifier(Stream& skey, CPubKey& agg_pub,
skey >> std::as_writable_bytes(std::span{part_pubkey_bytes}) >> std::as_writable_bytes(std::span{agg_pubkey_bytes});
agg_pub.Set(agg_pubkey_bytes.begin(), agg_pubkey_bytes.end());
+ if (!agg_pub.IsFullyValid()) {
+ throw std::ios_base::failure("musig2 aggregate pubkey is invalid");
+ }
+
part_pub.Set(part_pubkey_bytes.begin(), part_pubkey_bytes.end());
+ if (!part_pub.IsFullyValid()) {
+ throw std::ios_base::failure("musig2 participant pubkey is invalid");
+ }
if (!skey.empty()) {
skey >> leaf_hash;
diff --git a/test/functional/data/rpc_psbt.json b/test/functional/data/rpc_psbt.json
index 752fce55..abc09d52 100644
--- a/test/functional/data/rpc_psbt.json
+++ b/test/functional/data/rpc_psbt.json
@@ -106,6 +106,22 @@
[
"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",
"Size of value was not the stated size"
+ ],
+ [
+ "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",
+ "musig2 participant pubkey is invalid"
+ ],
+ [
+ "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",
+ "musig2 participant pubkey is invalid"
+ ],
+ [
+ "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",
+ "musig2 aggregate pubkey is invalid"
+ ],
+ [
+ "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",
+ "musig2 aggregate pubkey is invalid"
]
],
"valid" : [
Risk score
Our methodology →Why this scored 60/100
Human-validated context
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