102 lines
2.3 KiB
Go
102 lines
2.3 KiB
Go
package varsig
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import (
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"encoding/binary"
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"fmt"
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)
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// DiscriminatorECDSA is the value specifying an ECDSA signature.
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const DiscriminatorECDSA = Discriminator(0xec)
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// ECDSACurve are values that specify which ECDSA curve is used when
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// generating the signature.
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type ECDSACurve uint64
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// Constants describing the values for each specific ECDSA curve that can
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// be encoded into a Varsig.
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const (
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CurveSecp256k1 = ECDSACurve(0xe7)
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CurveP256 = ECDSACurve(0x1200)
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CurveP384 = ECDSACurve(0x1201)
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CurveP521 = ECDSACurve(0x1202)
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)
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func decodeECDSACurve(r BytesReader) (ECDSACurve, error) {
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u, err := binary.ReadUvarint(r)
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if err != nil {
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return 0, err
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}
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switch curve := ECDSACurve(u); curve {
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case CurveSecp256k1, CurveP256, CurveP384, CurveP521:
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return curve, nil
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default:
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return 0, fmt.Errorf("%w: %x", ErrUnknownECDSACurve, u)
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}
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}
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var _ Varsig = ECDSAVarsig{}
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// ECDSAVarsig is a varsig that encodes the parameters required to describe
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// an ECDSA signature.
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type ECDSAVarsig struct {
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varsig
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curve ECDSACurve
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hashAlg Hash
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}
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// NewECDSAVarsig creates and validates an ECDSA varsig with the provided
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// curve, hash algorithm and payload encoding.
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func NewECDSAVarsig(curve ECDSACurve, hashAlgorithm Hash, payloadEncoding PayloadEncoding) ECDSAVarsig {
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return ECDSAVarsig{
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varsig: varsig{
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disc: DiscriminatorECDSA,
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payEnc: payloadEncoding,
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},
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curve: curve,
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hashAlg: hashAlgorithm,
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}
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}
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// Curve returns the elliptic curve used to generate the ECDSA signature.
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func (v ECDSAVarsig) Curve() ECDSACurve {
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return v.curve
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}
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// Hash returns the value describing the hash algorithm used to hash
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// the payload content before the signature is generated.
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func (v ECDSAVarsig) Hash() Hash {
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return v.hashAlg
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}
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// Encode returns the encoded byte format of the ECDSAVarsig.
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func (v ECDSAVarsig) Encode() []byte {
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buf := v.encode()
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buf = binary.AppendUvarint(buf, uint64(v.curve))
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buf = binary.AppendUvarint(buf, uint64(v.hashAlg))
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buf = append(buf, EncodePayloadEncoding(v.payEnc)...)
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return buf
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}
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func decodeECDSA(r BytesReader) (Varsig, error) {
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curve, err := decodeECDSACurve(r)
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if err != nil {
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return nil, err
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}
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hashAlg, err := DecodeHashAlgorithm(r)
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if err != nil {
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return nil, err
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}
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payEnc, err := DecodePayloadEncoding(r)
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if err != nil {
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return nil, err
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}
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return NewECDSAVarsig(curve, hashAlg, payEnc), nil
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}
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