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Don't possibly dereference bad signatures in OP_CHECKMULTISIG.

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We do all the preprocessing in one loop. Fixes a bug introduced a while ago to
handle invalid signatures. Found by more tests from bitcoind.
This commit is contained in:
Owain G. Ainsworth 2014-03-17 15:05:39 +00:00
parent c8332cc9a7
commit dab2a7cb0f
1 changed files with 15 additions and 8 deletions
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23
opcode.go
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@ -1819,6 +1819,11 @@ func opcodeCheckSigVerify(op *parsedOpcode, s *Script) error {
return err
}
type sig struct {
s *btcec.Signature
ht byte
}
// stack; sigs <numsigs> pubkeys <numpubkeys>
func opcodeCheckMultiSig(op *parsedOpcode, s *Script) error {
@ -1857,21 +1862,25 @@ func opcodeCheckMultiSig(op *parsedOpcode, s *Script) error {
nsig := int(numSignatures.Int64())
sigStrings := make([][]byte, nsig)
signatures := make([]*btcec.Signature, 0, nsig)
signatures := make([]sig, 0, nsig)
for i := range sigStrings {
sigStrings[i], err = s.dstack.PopByteArray()
if err != nil {
return err
}
var sig *btcec.Signature
if len(sigStrings[i]) == 0 {
continue
}
sig := sig{}
sig.ht = sigStrings[i][len(sigStrings[i])-1]
// skip off the last byte for hashtype
if s.der {
sig, err =
sig.s, err =
btcec.ParseDERSignature(
sigStrings[i][:len(sigStrings[i])-1],
btcec.S256())
} else {
sig, err =
sig.s, err =
btcec.ParseSignature(
sigStrings[i][:len(sigStrings[i])-1],
btcec.S256())
@ -1906,10 +1915,8 @@ func opcodeCheckMultiSig(op *parsedOpcode, s *Script) error {
for i := range signatures {
// check signatures.
success := false
// get hashtype from original byte string
hashType := sigStrings[i][len(sigStrings[i])-1]
hash := calcScriptHash(script, hashType, &s.tx, s.txidx)
hash := calcScriptHash(script, signatures[i].ht, &s.tx, s.txidx)
inner:
// Find first pubkey that successfully validates signature.
// we start off the search from the key that was successful
@ -1924,7 +1931,7 @@ func opcodeCheckMultiSig(op *parsedOpcode, s *Script) error {
}
}
success = ecdsa.Verify(pubKeys[curPk], hash,
signatures[i].R, signatures[i].S)
signatures[i].s.R, signatures[i].s.S)
if success {
break inner
}