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package extension
import (
"encoding/binary"
"github.com/pion/dtls/v2/pkg/crypto/hash"
"github.com/pion/dtls/v2/pkg/crypto/signature"
"github.com/pion/dtls/v2/pkg/crypto/signaturehash"
)
const (
supportedSignatureAlgorithmsHeaderSize = 6
)
// SupportedSignatureAlgorithms allows a Client/Server to
// negotiate what SignatureHash Algorithms they both support
//
// https://tools.ietf.org/html/rfc5246#section-7.4.1.4.1
type SupportedSignatureAlgorithms struct {
SignatureHashAlgorithms []signaturehash.Algorithm
}
// TypeValue returns the extension TypeValue
func (s SupportedSignatureAlgorithms) TypeValue() TypeValue {
return SupportedSignatureAlgorithmsTypeValue
}
// Marshal encodes the extension
func (s *SupportedSignatureAlgorithms) Marshal() ([]byte, error) {
out := make([]byte, supportedSignatureAlgorithmsHeaderSize)
binary.BigEndian.PutUint16(out, uint16(s.TypeValue()))
binary.BigEndian.PutUint16(out[2:], uint16(2+(len(s.SignatureHashAlgorithms)*2)))
binary.BigEndian.PutUint16(out[4:], uint16(len(s.SignatureHashAlgorithms)*2))
for _, v := range s.SignatureHashAlgorithms {
out = append(out, []byte{0x00, 0x00}...)
out[len(out)-2] = byte(v.Hash)
out[len(out)-1] = byte(v.Signature)
}
return out, nil
}
// Unmarshal populates the extension from encoded data
func (s *SupportedSignatureAlgorithms) Unmarshal(data []byte) error {
if len(data) <= supportedSignatureAlgorithmsHeaderSize {
return errBufferTooSmall
} else if TypeValue(binary.BigEndian.Uint16(data)) != s.TypeValue() {
return errInvalidExtensionType
}
algorithmCount := int(binary.BigEndian.Uint16(data[4:]) / 2)
if supportedSignatureAlgorithmsHeaderSize+(algorithmCount*2) > len(data) {
return errLengthMismatch
}
for i := 0; i < algorithmCount; i++ {
supportedHashAlgorithm := hash.Algorithm(data[supportedSignatureAlgorithmsHeaderSize+(i*2)])
supportedSignatureAlgorithm := signature.Algorithm(data[supportedSignatureAlgorithmsHeaderSize+(i*2)+1])
if _, ok := hash.Algorithms()[supportedHashAlgorithm]; ok {
if _, ok := signature.Algorithms()[supportedSignatureAlgorithm]; ok {
s.SignatureHashAlgorithms = append(s.SignatureHashAlgorithms, signaturehash.Algorithm{
Hash: supportedHashAlgorithm,
Signature: supportedSignatureAlgorithm,
})
}
}
}
return nil
}
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