79 lines
1.9 KiB
Go
79 lines
1.9 KiB
Go
package extension
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import (
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"strings"
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"golang.org/x/crypto/cryptobyte"
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)
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const serverNameTypeDNSHostName = 0
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// ServerName allows the client to inform the server the specific
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// name it wishs to contact. Useful if multiple DNS names resolve
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// to one IP
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//
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// https://tools.ietf.org/html/rfc6066#section-3
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type ServerName struct {
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ServerName string
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}
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// TypeValue returns the extension TypeValue
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func (s ServerName) TypeValue() TypeValue {
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return ServerNameTypeValue
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}
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// Marshal encodes the extension
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func (s *ServerName) Marshal() ([]byte, error) {
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var b cryptobyte.Builder
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b.AddUint16(uint16(s.TypeValue()))
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b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddUint8(serverNameTypeDNSHostName)
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b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
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b.AddBytes([]byte(s.ServerName))
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})
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})
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})
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return b.Bytes()
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}
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// Unmarshal populates the extension from encoded data
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func (s *ServerName) Unmarshal(data []byte) error {
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val := cryptobyte.String(data)
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var extension uint16
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val.ReadUint16(&extension)
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if TypeValue(extension) != s.TypeValue() {
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return errInvalidExtensionType
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}
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var extData cryptobyte.String
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val.ReadUint16LengthPrefixed(&extData)
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var nameList cryptobyte.String
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if !extData.ReadUint16LengthPrefixed(&nameList) || nameList.Empty() {
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return errInvalidSNIFormat
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}
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for !nameList.Empty() {
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var nameType uint8
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var serverName cryptobyte.String
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if !nameList.ReadUint8(&nameType) ||
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!nameList.ReadUint16LengthPrefixed(&serverName) ||
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serverName.Empty() {
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return errInvalidSNIFormat
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}
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if nameType != serverNameTypeDNSHostName {
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continue
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}
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if len(s.ServerName) != 0 {
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// Multiple names of the same name_type are prohibited.
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return errInvalidSNIFormat
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}
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s.ServerName = string(serverName)
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// An SNI value may not include a trailing dot.
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if strings.HasSuffix(s.ServerName, ".") {
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return errInvalidSNIFormat
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}
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}
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return nil
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}
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