104 lines
2.8 KiB
Go
104 lines
2.8 KiB
Go
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package socks5
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"net"
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"net/netip"
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)
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// See https://datatracker.ietf.org/doc/html/rfc1928#section-6
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func (c *socksConn) encodeFailedResponse(writer io.Writer, socksVersion byte, reply replyCode) {
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_, err := writer.Write([]byte{
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socksVersion,
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byte(reply),
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0, // RSV byte
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// TODO do we need to set the bind addr type to 0??
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})
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if err != nil {
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c.logger.Warnf("failed writing failed response: %s", err)
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}
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}
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// See https://datatracker.ietf.org/doc/html/rfc1928#section-6
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func (c *socksConn) encodeSuccessResponse(writer io.Writer, socksVersion byte,
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reply replyCode, bindAddrType addrType, bindAddress string,
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bindPort uint16) (err error) {
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bindData, err := encodeBindData(bindAddrType, bindAddress, bindPort)
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if err != nil { // TODO encode with below block if this changes
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return err
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}
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const initialPacketLength = 3
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capacity := initialPacketLength + len(bindData)
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packet := make([]byte, initialPacketLength, capacity)
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packet[0] = socksVersion
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packet[1] = byte(reply)
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packet[2] = 0 // RSV byte
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packet = append(packet, bindData...)
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_, err = writer.Write(packet)
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if err != nil {
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c.logger.Warnf("failed writing success response: %s", err)
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}
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return nil
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}
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var (
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ErrIPVersionUnexpected = errors.New("ip version is unexpected")
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ErrDomainNameTooLong = errors.New("domain name is too long")
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)
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func encodeBindData(addrType addrType, address string, port uint16) (
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data []byte, err error) {
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capacity := bindDataLength(addrType, address)
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data = make([]byte, 0, capacity)
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data = append(data, byte(addrType))
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switch addrType {
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case ipv4, ipv6:
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ip, err := netip.ParseAddr(address)
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if err != nil {
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return nil, fmt.Errorf("parsing IP address: %w", err)
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}
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switch {
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case addrType == ipv4 && !ip.Is4():
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return nil, fmt.Errorf("%w: expected IPv4 for %s", ErrIPVersionUnexpected, ip)
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case addrType == ipv6 && !ip.Is6():
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return nil, fmt.Errorf("%w: expected IPv6 for %s", ErrIPVersionUnexpected, ip)
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}
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data = append(data, ip.AsSlice()...)
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case domainName:
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const maxDomainNameLength = 255
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if len(address) > maxDomainNameLength {
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return nil, fmt.Errorf("%w: %s", ErrDomainNameTooLong, address)
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}
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data = append(data, byte(len(address)))
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data = append(data, []byte(address)...)
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default:
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panic(fmt.Sprintf("unsupported address type %d", addrType))
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}
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data = binary.BigEndian.AppendUint16(data, port)
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return data, nil
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}
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func bindDataLength(addrType addrType, address string) (maxLength int) {
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maxLength++ // address type
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switch addrType {
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case ipv4:
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maxLength += net.IPv4len
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case domainName:
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maxLength++ // domain name length
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maxLength += len([]byte(address))
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case ipv6:
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maxLength += net.IPv6len
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default:
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panic("unsupported address type: " + fmt.Sprint(addrType))
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}
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maxLength += 2 // port
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return maxLength
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}
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