112 lines
2.7 KiB
Go
112 lines
2.7 KiB
Go
package handshake
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import (
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"encoding/binary"
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"github.com/pion/dtls/v2/pkg/protocol"
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"github.com/pion/dtls/v2/pkg/protocol/extension"
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)
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// MessageServerHello is sent in response to a ClientHello
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// message when it was able to find an acceptable set of algorithms.
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// If it cannot find such a match, it will respond with a handshake
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// failure alert.
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//
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// https://tools.ietf.org/html/rfc5246#section-7.4.1.3
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type MessageServerHello struct {
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Version protocol.Version
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Random Random
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SessionID []byte // TODO 添加anylink支持
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CipherSuiteID *uint16
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CompressionMethod *protocol.CompressionMethod
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Extensions []extension.Extension
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}
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const messageServerHelloVariableWidthStart = 2 + RandomLength
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// Type returns the Handshake Type
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func (m MessageServerHello) Type() Type {
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return TypeServerHello
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}
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// Marshal encodes the Handshake
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func (m *MessageServerHello) Marshal() ([]byte, error) {
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if m.CipherSuiteID == nil {
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return nil, errCipherSuiteUnset
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} else if m.CompressionMethod == nil {
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return nil, errCompressionMethodUnset
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}
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out := make([]byte, messageServerHelloVariableWidthStart)
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out[0] = m.Version.Major
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out[1] = m.Version.Minor
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rand := m.Random.MarshalFixed()
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copy(out[2:], rand[:])
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// out = append(out, 0x00) // SessionID
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// TODO 添加SessionID
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out = append(out, byte(len(m.SessionID))) // SessionID
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out = append(out, m.SessionID...)
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out = append(out, []byte{0x00, 0x00}...)
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binary.BigEndian.PutUint16(out[len(out)-2:], *m.CipherSuiteID)
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out = append(out, byte(m.CompressionMethod.ID))
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extensions, err := extension.Marshal(m.Extensions)
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if err != nil {
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return nil, err
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}
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return append(out, extensions...), nil
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}
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// Unmarshal populates the message from encoded data
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func (m *MessageServerHello) Unmarshal(data []byte) error {
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if len(data) < 2+RandomLength {
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return errBufferTooSmall
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}
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m.Version.Major = data[0]
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m.Version.Minor = data[1]
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var random [RandomLength]byte
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copy(random[:], data[2:])
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m.Random.UnmarshalFixed(random)
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currOffset := messageServerHelloVariableWidthStart
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currOffset += int(data[currOffset]) + 1 // SessionID
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if len(data) < (currOffset + 2) {
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return errBufferTooSmall
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}
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m.CipherSuiteID = new(uint16)
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*m.CipherSuiteID = binary.BigEndian.Uint16(data[currOffset:])
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currOffset += 2
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if len(data) < currOffset {
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return errBufferTooSmall
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}
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if compressionMethod, ok := protocol.CompressionMethods()[protocol.CompressionMethodID(data[currOffset])]; ok {
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m.CompressionMethod = compressionMethod
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currOffset++
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} else {
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return errInvalidCompressionMethod
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}
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if len(data) <= currOffset {
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m.Extensions = []extension.Extension{}
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return nil
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}
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extensions, err := extension.Unmarshal(data[currOffset:])
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if err != nil {
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return err
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}
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m.Extensions = extensions
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return nil
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}
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