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schnorr: Zero internal bytes of big ints.

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This modifies the instances in the schnorr package that zero out big
ints that use a function to clear the internal memory used by the big
int since merely setting it to 0 does not do that.
This commit is contained in:
Dave Collins 2020-02-20 00:59:02 -06:00
parent 04272a79c4
commit 189fa7a4a3
No known key found for this signature in database
GPG Key ID: B8904D9D9C93D1F2
1 changed files with 14 additions and 3 deletions
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17
dcrec/secp256k1/schnorr/ecdsa.go
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@ -40,6 +40,17 @@ func zeroSlice(s []byte) {
}
}
// zeroBigInt zeroes the underlying memory used by the passed big integer. The
// big integer must not be used after calling this as it changes the internal
// state out from under it which can lead to unpredictable results.
func zeroBigInt(v *big.Int) {
words := v.Bits()
for i := 0; i < len(words); i++ {
words[i] = 0
}
v.SetInt64(0)
}
// GenerateKey generates a key using a random number generator, returning
// the private scalar and the corresponding public key points.
func GenerateKey(rand io.Reader) (priv []byte, x, y *big.Int, err error) {
@ -150,9 +161,9 @@ func schnorrSign(msg []byte, ps []byte, k []byte,
}
// Zero out the private key and nonce when we're done with it.
bigK.SetInt64(0)
zeroBigInt(bigK)
zeroSlice(k)
psBig.SetInt64(0)
zeroBigInt(psBig)
zeroSlice(ps)
return &Signature{Rpx, sBig}, nil
@ -165,7 +176,7 @@ func nonceRFC6979(privKey []byte, hash []byte, extra []byte, version []byte, ext
kBytes := k.Bytes()
defer zeroArray(&kBytes)
bigK := new(big.Int).SetBytes(kBytes[:])
defer bigK.SetInt64(0)
defer zeroBigInt(bigK)
nonce := bigIntToEncodedBytes(bigK)
return nonce[:]
}