54 lines
2.1 KiB
Go
54 lines
2.1 KiB
Go
package wire
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import (
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"crypto/rand"
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"encoding/binary"
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"errors"
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"github.com/quic-go/quic-go/internal/protocol"
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)
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// ParseVersionNegotiationPacket parses a Version Negotiation packet.
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func ParseVersionNegotiationPacket(b []byte) (dest, src protocol.ArbitraryLenConnectionID, _ []protocol.Version, _ error) {
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n, dest, src, err := ParseArbitraryLenConnectionIDs(b)
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if err != nil {
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return nil, nil, nil, err
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}
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b = b[n:]
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if len(b) == 0 {
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//nolint:stylecheck
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return nil, nil, nil, errors.New("Version Negotiation packet has empty version list")
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}
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if len(b)%4 != 0 {
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//nolint:stylecheck
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return nil, nil, nil, errors.New("Version Negotiation packet has a version list with an invalid length")
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}
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versions := make([]protocol.Version, len(b)/4)
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for i := 0; len(b) > 0; i++ {
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versions[i] = protocol.Version(binary.BigEndian.Uint32(b[:4]))
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b = b[4:]
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}
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return dest, src, versions, nil
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}
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// ComposeVersionNegotiation composes a Version Negotiation
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func ComposeVersionNegotiation(destConnID, srcConnID protocol.ArbitraryLenConnectionID, versions []protocol.Version) []byte {
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greasedVersions := protocol.GetGreasedVersions(versions)
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expectedLen := 1 /* type byte */ + 4 /* version field */ + 1 /* dest connection ID length field */ + destConnID.Len() + 1 /* src connection ID length field */ + srcConnID.Len() + len(greasedVersions)*4
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buf := make([]byte, 1+4 /* type byte and version field */, expectedLen)
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_, _ = rand.Read(buf[:1]) // ignore the error here. It is not critical to have perfect random here.
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// Setting the "QUIC bit" (0x40) is not required by the RFC,
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// but it allows clients to demultiplex QUIC with a long list of other protocols.
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// See RFC 9443 and https://mailarchive.ietf.org/arch/msg/quic/oR4kxGKY6mjtPC1CZegY1ED4beg/ for details.
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buf[0] |= 0xc0
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// The next 4 bytes are left at 0 (version number).
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buf = append(buf, uint8(destConnID.Len()))
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buf = append(buf, destConnID.Bytes()...)
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buf = append(buf, uint8(srcConnID.Len()))
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buf = append(buf, srcConnID.Bytes()...)
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for _, v := range greasedVersions {
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buf = binary.BigEndian.AppendUint32(buf, uint32(v))
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}
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return buf
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}
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