mirror of
https://github.com/lightningnetwork/lnd.git
synced 2024-11-19 18:10:34 +01:00
a20594b0bf
This commit modifies the encoding of signatures on the wire to use a fixed-size 64-byte format. This change is required as the current spec draft dictates that all signatures be encoded as `R` and `S` as 32-byte big-endian integers. With this, signatures are now always a _fixed_ size slice of bytes on the wire, which is nice to have. Fixes #83.
106 lines
3.2 KiB
Go
106 lines
3.2 KiB
Go
package lnwire
|
|
|
|
import (
|
|
"fmt"
|
|
|
|
"github.com/roasbeef/btcd/btcec"
|
|
)
|
|
|
|
// serializeSigToWire serializes a *Signature to [64]byte in the format
|
|
// specified by the Lightning RFC.
|
|
func serializeSigToWire(b *[64]byte, e *btcec.Signature) error {
|
|
|
|
// Serialize the signature with all the checks that entails.
|
|
sig := e.Serialize()
|
|
|
|
// Extract lengths of R and S. The DER representation is laid out as
|
|
// 0x30 <length> 0x02 <length r> r 0x02 <length s> s
|
|
// which means the length of R is the 4th byte and the length of S
|
|
// is the second byte after R ends. 0x02 signifies a length-prefixed,
|
|
// zero-padded, big-endian bigint. 0x30 sigifies a DER signature.
|
|
// See the Serialize() method for btcec.Signature for details.
|
|
rLen := uint8(sig[3])
|
|
sLen := uint8(sig[5+rLen])
|
|
|
|
// Check to make sure R and S can both fit into their intended buffers.
|
|
// We check S first because these code blocks decrement sLen and
|
|
// rLen in the case of a 33-byte 0-padded integer returned from
|
|
// Serialize() and rLen is used in calculating array indices for
|
|
// S. We can track this with additional variables, but it's more
|
|
// efficient to just check S first.
|
|
if sLen > 32 {
|
|
if (sLen > 33) || (sig[6+rLen] != 0x00) {
|
|
return fmt.Errorf("S is over 32 bytes long " +
|
|
"without padding")
|
|
} else {
|
|
sLen -= 1
|
|
copy(b[64-sLen:], sig[7+rLen:])
|
|
}
|
|
} else {
|
|
copy(b[64-sLen:], sig[6+rLen:])
|
|
}
|
|
|
|
// Do the same for R as we did for S
|
|
if rLen > 32 {
|
|
if (rLen > 33) || (sig[4] != 0x00) {
|
|
return fmt.Errorf("R is over 32 bytes long " +
|
|
"without padding")
|
|
} else {
|
|
rLen -= 1
|
|
copy(b[32-rLen:], sig[5:5+rLen])
|
|
}
|
|
} else {
|
|
copy(b[32-rLen:], sig[4:4+rLen])
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// deserializeSigFromWire deserializes a *Signature from [64]byte in the format
|
|
// specified by the Lightning RFC.
|
|
func deserializeSigFromWire(e **btcec.Signature, b [64]byte) error {
|
|
|
|
// Extract canonically-padded bigint representations from buffer
|
|
r := extractCanonicalPadding(b[0:32])
|
|
s := extractCanonicalPadding(b[32:64])
|
|
rLen := uint8(len(r))
|
|
sLen := uint8(len(s))
|
|
|
|
// Create a canonical serialized signature. DER format is:
|
|
// 0x30 <length> 0x02 <length r> r 0x02 <length s> s
|
|
sigBytes := make([]byte, 6+rLen+sLen, 6+rLen+sLen)
|
|
sigBytes[0] = 0x30 // DER signature magic value
|
|
sigBytes[1] = 4 + rLen + sLen // Length of rest of signature
|
|
sigBytes[2] = 0x02 // Big integer magic value
|
|
sigBytes[3] = rLen // Length of R
|
|
sigBytes[rLen+4] = 0x02 // Big integer magic value
|
|
sigBytes[rLen+5] = sLen // Length of S
|
|
copy(sigBytes[4:], r) // Copy R
|
|
copy(sigBytes[rLen+6:], s) // Copy S
|
|
|
|
// Parse the signature with strict checks.
|
|
sig, err := btcec.ParseDERSignature(sigBytes, btcec.S256())
|
|
if err != nil {
|
|
return err
|
|
}
|
|
*e = sig
|
|
return nil
|
|
}
|
|
|
|
// extractCanonicalPadding is a utility function to extract the canonical
|
|
// padding of a big-endian integer from the wire encoding (a 0-padded
|
|
// big-endian integer) such that it passes btcec.canonicalPadding test.
|
|
func extractCanonicalPadding(b []byte) []byte {
|
|
for i := 0; i < len(b); i++ {
|
|
// Found first non-zero byte.
|
|
if b[i] > 0 {
|
|
// If the MSB is set, we need zero padding.
|
|
if b[i]&0x80 == 0x80 {
|
|
return append([]byte{0x00}, b[i:]...)
|
|
} else {
|
|
return b[i:]
|
|
}
|
|
}
|
|
}
|
|
return []byte{0x00}
|
|
}
|