Block diagram
This page hosts a formal specification of tls_client_hello using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
meta:
id: tls_client_hello
xref:
rfc: 5246 # TLS 1.2
wikidata: Q206494 # TLS
license: MIT
endian: be
seq:
- id: version
type: version
- id: random
type: random
- id: session_id
type: session_id
- id: cipher_suites
type: cipher_suites
- id: compression_methods
type: compression_methods
- id: extensions
type: extensions
if: _io.eof == false
types:
version:
seq:
- id: major
type: u1
- id: minor
type: u1
random:
seq:
- id: gmt_unix_time
type: u4
- id: random
size: 28
session_id:
seq:
- id: len
type: u1
- id: sid
size: len
cipher_suites:
seq:
- id: len
type: u2
- id: cipher_suites
type: u2
repeat: expr
repeat-expr: len/2
compression_methods:
seq:
- id: len
type: u1
- id: compression_methods
size: len
extensions:
seq:
- id: len
type: u2
- id: extensions
type: extension
repeat: eos
extension:
seq:
- id: type
type: u2
- id: len
type: u2
- id: body
size: len
type:
switch-on: type
cases:
0: sni
16: alpn
sni:
seq:
- id: list_length
type: u2
- id: server_names
type: server_name
repeat: eos
server_name:
seq:
- id: name_type
type: u1
- id: length
type: u2
- id: host_name
size: length
alpn:
seq:
- id: ext_len
type: u2
- id: alpn_protocols
type: protocol
repeat: eos
protocol:
seq:
- id: strlen
type: u1
- id: name
size: strlen