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psbt: remove UTXO sanity check to allow fix for CVE

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As described in CVE-2020-14199 it is unsafe to only rely on witness
UTXO information when signing. Hardware wallets fixed this by also
requiring the full non-witness UTXO to be present for a witness input.
To be compatible with those newer hardware wallet firmware, we need to
remove the sanity checks that disallowed setting witness and non-witness
UTXOs at the same time.
See https://github.com/bitcoin/bitcoin/pull/19215 for comparison which
removed the sanity checks in Bitcoin Core.
This commit is contained in:
Oliver Gugger 2020-07-20 15:02:02 +02:00
parent 4649e4b73b
commit c5f199e40f
No known key found for this signature in database
GPG key ID: 8E4256593F177720
2 changed files with 8 additions and 11 deletions
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16
psbt/partial_input.go
View file

@ -49,19 +49,13 @@ func NewPsbtInput(nonWitnessUtxo *wire.MsgTx,
} }
// IsSane returns true only if there are no conflicting values in the Psbt // IsSane returns true only if there are no conflicting values in the Psbt
// PInput. It checks that witness and non-witness utxo entries do not both // PInput. For segwit v0 no checks are currently implemented.
// exist, and that witnessScript entries are only added to witness inputs.
func (pi *PInput) IsSane() bool { func (pi *PInput) IsSane() bool {
if pi.NonWitnessUtxo != nil && pi.WitnessUtxo != nil { // TODO(guggero): Implement sanity checks for segwit v1. For segwit v0
return false // it is unsafe to only rely on the witness UTXO so we don't check that
} // only one is set anymore.
if pi.WitnessUtxo == nil && pi.WitnessScript != nil { // See https://github.com/bitcoin/bitcoin/pull/19215.
return false
}
if pi.WitnessUtxo == nil && pi.FinalScriptWitness != nil {
return false
}
return true return true
} }

3
psbt/psbt_test.go
View file

@ -161,6 +161,9 @@ func TestReadInvalidPsbt(t *testing.T) {
} }
func TestSanityCheck(t *testing.T) { func TestSanityCheck(t *testing.T) {
// TODO(guggero): Remove when checks for segwit v1 are implemented.
t.Skip("Skipping PSBT sanity checks for segwit v0.")
// Test strategy: // Test strategy:
// 1. Create an invalid PSBT from a serialization // 1. Create an invalid PSBT from a serialization
// Then ensure that the sanity check fails. // Then ensure that the sanity check fails.