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authorGlenn Willen <gwillen@nerdnet.org>2018-10-26 15:31:41 -0700
committerGlenn Willen <gwillen@nerdnet.org>2018-11-01 12:14:21 -0700
commit565500508aa5df0011109ebf375ba71b693fc7de (patch)
treee87abd87ce2a1362e91e99b3cf56b8e0eb066669 /src/script
parent0f5bda2bd941686620ef0eb90bd7ed973cc7ef73 (diff)
Refactor PSBTInput signing to enforce invariant
Refactor the process of PSBTInput signing to enforce the invariant that a PSBTInput always has _either_ a witness_utxo or a non_witness_utxo, never both. This simplifies the logic of SignPSBTInput slightly, since it no longer has to deal with the "both" case. When calling it, we now give it, in order of preference: (1) whichever of the utxo fields was already present in the PSBT we received, or (2) if neither, the non_witness_utxo field, which is just a copy of the input transaction, which we get from the wallet. SignPSBTInput no longer has to remove one of the two fields; instead, it will check if we have a witness signature, and if so, it will replace the non_witness_utxo with the witness_utxo (which is smaller, as it is just a copy of the output being spent.) Add PSBTInput::IsSane checks in two more places, which checks for both utxo fields being present; we will now give an RPC error early on if we are supplied such a malformed PSBT to fill in. Also add a check to FillPSBT, to avoid touching any input that is already signed. (This is now redundant, since we should no longer potentially harm an already-signed input, but it's harmless.) fixes #14473
Diffstat (limited to 'src/script')
-rw-r--r--src/script/sign.cpp30
1 files changed, 13 insertions, 17 deletions
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 1e481dd541..69ee08ffd7 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -260,15 +260,19 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
// Get UTXO
bool require_witness_sig = false;
CTxOut utxo;
+
+ // Verify input sanity, which checks that at most one of witness or non-witness utxos is provided.
+ if (!input.IsSane()) {
+ return false;
+ }
+
if (input.non_witness_utxo) {
// If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
- if (input.non_witness_utxo->GetHash() != tx.vin[index].prevout.hash) return false;
- // If both witness and non-witness UTXO are provided, verify that they match. This check shouldn't
- // matter, as the PSBT deserializer enforces only one of both is provided, and the only way both
- // can be present is when they're added simultaneously by FillPSBT (in which case they always match).
- // Still, check in order to not rely on callers to enforce this.
- if (!input.witness_utxo.IsNull() && input.non_witness_utxo->vout[tx.vin[index].prevout.n] != input.witness_utxo) return false;
- utxo = input.non_witness_utxo->vout[tx.vin[index].prevout.n];
+ COutPoint prevout = tx.vin[index].prevout;
+ if (input.non_witness_utxo->GetHash() != prevout.hash) {
+ return false;
+ }
+ utxo = input.non_witness_utxo->vout[prevout.n];
} else if (!input.witness_utxo.IsNull()) {
utxo = input.witness_utxo;
// When we're taking our information from a witness UTXO, we can't verify it is actually data from
@@ -287,18 +291,10 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
if (require_witness_sig && !sigdata.witness) return false;
input.FromSignatureData(sigdata);
+ // If we have a witness signature, use the smaller witness UTXO.
if (sigdata.witness) {
- assert(!utxo.IsNull());
input.witness_utxo = utxo;
- }
-
- // If both UTXO types are present, drop the unnecessary one.
- if (input.non_witness_utxo && !input.witness_utxo.IsNull()) {
- if (sigdata.witness) {
- input.non_witness_utxo = nullptr;
- } else {
- input.witness_utxo.SetNull();
- }
+ input.non_witness_utxo = nullptr;
}
return sig_complete;