mirror of
https://github.com/SagerNet/sing-box.git
synced 2024-10-18 07:52:48 +00:00
358 lines
10 KiB
Go
358 lines
10 KiB
Go
// Copyright (c) 2018, Open Systems AG. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the LICENSE file in the root of the source
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// tree.
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package ja3
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import (
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"encoding/binary"
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"strconv"
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)
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const (
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// Constants used for parsing
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recordLayerHeaderLen int = 5
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handshakeHeaderLen int = 6
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randomDataLen int = 32
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sessionIDHeaderLen int = 1
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cipherSuiteHeaderLen int = 2
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compressMethodHeaderLen int = 1
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extensionsHeaderLen int = 2
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extensionHeaderLen int = 4
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sniExtensionHeaderLen int = 5
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ecExtensionHeaderLen int = 2
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ecpfExtensionHeaderLen int = 1
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versionExtensionHeaderLen int = 1
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signatureAlgorithmsExtensionHeaderLen int = 2
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contentType uint8 = 22
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handshakeType uint8 = 1
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sniExtensionType uint16 = 0
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sniNameDNSHostnameType uint8 = 0
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ecExtensionType uint16 = 10
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ecpfExtensionType uint16 = 11
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versionExtensionType uint16 = 43
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signatureAlgorithmsExtensionType uint16 = 13
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// Versions
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// The bitmask covers the versions SSL3.0 to TLS1.2
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tlsVersionBitmask uint16 = 0xFFFC
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tls13 uint16 = 0x0304
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// GREASE values
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// The bitmask covers all GREASE values
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GreaseBitmask uint16 = 0x0F0F
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// Constants used for marshalling
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dashByte = byte(45)
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commaByte = byte(44)
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)
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// parseSegment to populate the corresponding ClientHello object or return an error
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func (j *ClientHello) parseSegment(segment []byte) error {
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// Check if we can decode the next fields
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if len(segment) < recordLayerHeaderLen {
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return &ParseError{LengthErr, 1}
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}
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// Check if we have "Content Type: Handshake (22)"
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contType := uint8(segment[0])
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if contType != contentType {
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return &ParseError{errType: ContentTypeErr}
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}
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// Check if TLS record layer version is supported
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tlsRecordVersion := uint16(segment[1])<<8 | uint16(segment[2])
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if tlsRecordVersion&tlsVersionBitmask != 0x0300 && tlsRecordVersion != tls13 {
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return &ParseError{VersionErr, 1}
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}
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// Check that the Handshake is as long as expected from the length field
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segmentLen := uint16(segment[3])<<8 | uint16(segment[4])
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if len(segment[recordLayerHeaderLen:]) < int(segmentLen) {
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return &ParseError{LengthErr, 2}
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}
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// Keep the Handshake messege, ignore any additional following record types
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hs := segment[recordLayerHeaderLen : recordLayerHeaderLen+int(segmentLen)]
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err := j.parseHandshake(hs)
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return err
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}
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// parseHandshake body
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func (j *ClientHello) parseHandshake(hs []byte) error {
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// Check if we can decode the next fields
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if len(hs) < handshakeHeaderLen+randomDataLen+sessionIDHeaderLen {
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return &ParseError{LengthErr, 3}
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}
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// Check if we have "Handshake Type: Client Hello (1)"
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handshType := uint8(hs[0])
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if handshType != handshakeType {
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return &ParseError{errType: HandshakeTypeErr}
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}
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// Check if actual length of handshake matches (this is a great exclusion criterion for false positives,
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// as these fields have to match the actual length of the rest of the segment)
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handshakeLen := uint32(hs[1])<<16 | uint32(hs[2])<<8 | uint32(hs[3])
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if len(hs[4:]) != int(handshakeLen) {
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return &ParseError{LengthErr, 4}
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}
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// Check if Client Hello version is supported
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tlsVersion := uint16(hs[4])<<8 | uint16(hs[5])
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if tlsVersion&tlsVersionBitmask != 0x0300 && tlsVersion != tls13 {
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return &ParseError{VersionErr, 2}
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}
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j.Version = tlsVersion
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// Check if we can decode the next fields
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sessionIDLen := uint8(hs[38])
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if len(hs) < handshakeHeaderLen+randomDataLen+sessionIDHeaderLen+int(sessionIDLen) {
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return &ParseError{LengthErr, 5}
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}
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// Cipher Suites
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cs := hs[handshakeHeaderLen+randomDataLen+sessionIDHeaderLen+int(sessionIDLen):]
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// Check if we can decode the next fields
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if len(cs) < cipherSuiteHeaderLen {
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return &ParseError{LengthErr, 6}
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}
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csLen := uint16(cs[0])<<8 | uint16(cs[1])
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numCiphers := int(csLen / 2)
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cipherSuites := make([]uint16, 0, numCiphers)
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// Check if we can decode the next fields
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if len(cs) < cipherSuiteHeaderLen+int(csLen)+compressMethodHeaderLen {
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return &ParseError{LengthErr, 7}
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}
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for i := 0; i < numCiphers; i++ {
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cipherSuite := uint16(cs[2+i<<1])<<8 | uint16(cs[3+i<<1])
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cipherSuites = append(cipherSuites, cipherSuite)
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}
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j.CipherSuites = cipherSuites
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// Check if we can decode the next fields
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compressMethodLen := uint16(cs[cipherSuiteHeaderLen+int(csLen)])
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if len(cs) < cipherSuiteHeaderLen+int(csLen)+compressMethodHeaderLen+int(compressMethodLen) {
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return &ParseError{LengthErr, 8}
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}
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// Extensions
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exs := cs[cipherSuiteHeaderLen+int(csLen)+compressMethodHeaderLen+int(compressMethodLen):]
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err := j.parseExtensions(exs)
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return err
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}
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// parseExtensions of the handshake
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func (j *ClientHello) parseExtensions(exs []byte) error {
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// Check for no extensions, this fields header is nonexistent if no body is used
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if len(exs) == 0 {
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return nil
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}
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// Check if we can decode the next fields
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if len(exs) < extensionsHeaderLen {
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return &ParseError{LengthErr, 9}
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}
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exsLen := uint16(exs[0])<<8 | uint16(exs[1])
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exs = exs[extensionsHeaderLen:]
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// Check if we can decode the next fields
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if len(exs) < int(exsLen) {
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return &ParseError{LengthErr, 10}
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}
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var sni []byte
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var extensions, ellipticCurves []uint16
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var ellipticCurvePF []uint8
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var versions []uint16
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var signatureAlgorithms []uint16
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for len(exs) > 0 {
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// Check if we can decode the next fields
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if len(exs) < extensionHeaderLen {
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return &ParseError{LengthErr, 11}
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}
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exType := uint16(exs[0])<<8 | uint16(exs[1])
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exLen := uint16(exs[2])<<8 | uint16(exs[3])
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// Ignore any GREASE extensions
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extensions = append(extensions, exType)
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// Check if we can decode the next fields
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if len(exs) < extensionHeaderLen+int(exLen) {
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return &ParseError{LengthErr, 12}
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}
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sex := exs[extensionHeaderLen : extensionHeaderLen+int(exLen)]
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switch exType {
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case sniExtensionType: // Extensions: server_name
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// Check if we can decode the next fields
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if len(sex) < sniExtensionHeaderLen {
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return &ParseError{LengthErr, 13}
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}
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sniType := uint8(sex[2])
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sniLen := uint16(sex[3])<<8 | uint16(sex[4])
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sex = sex[sniExtensionHeaderLen:]
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// Check if we can decode the next fields
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if len(sex) != int(sniLen) {
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return &ParseError{LengthErr, 14}
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}
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switch sniType {
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case sniNameDNSHostnameType:
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sni = sex
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default:
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return &ParseError{errType: SNITypeErr}
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}
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case ecExtensionType: // Extensions: supported_groups
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// Check if we can decode the next fields
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if len(sex) < ecExtensionHeaderLen {
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return &ParseError{LengthErr, 15}
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}
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ecsLen := uint16(sex[0])<<8 | uint16(sex[1])
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numCurves := int(ecsLen / 2)
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ellipticCurves = make([]uint16, 0, numCurves)
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sex = sex[ecExtensionHeaderLen:]
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// Check if we can decode the next fields
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if len(sex) != int(ecsLen) {
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return &ParseError{LengthErr, 16}
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}
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for i := 0; i < numCurves; i++ {
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ecType := uint16(sex[i*2])<<8 | uint16(sex[1+i*2])
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ellipticCurves = append(ellipticCurves, ecType)
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}
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case ecpfExtensionType: // Extensions: ec_point_formats
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// Check if we can decode the next fields
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if len(sex) < ecpfExtensionHeaderLen {
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return &ParseError{LengthErr, 17}
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}
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ecpfsLen := uint8(sex[0])
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numPF := int(ecpfsLen)
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ellipticCurvePF = make([]uint8, numPF)
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sex = sex[ecpfExtensionHeaderLen:]
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// Check if we can decode the next fields
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if len(sex) != numPF {
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return &ParseError{LengthErr, 18}
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}
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for i := 0; i < numPF; i++ {
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ellipticCurvePF[i] = uint8(sex[i])
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}
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case versionExtensionType:
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if len(sex) < versionExtensionHeaderLen {
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return &ParseError{LengthErr, 19}
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}
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versionsLen := int(sex[0])
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for i := 0; i < versionsLen; i += 2 {
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versions = append(versions, binary.BigEndian.Uint16(sex[1:][i:]))
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}
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case signatureAlgorithmsExtensionType:
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if len(sex) < signatureAlgorithmsExtensionHeaderLen {
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return &ParseError{LengthErr, 20}
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}
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ssaLen := binary.BigEndian.Uint16(sex)
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for i := 0; i < int(ssaLen); i += 2 {
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signatureAlgorithms = append(signatureAlgorithms, binary.BigEndian.Uint16(sex[2:][i:]))
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}
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}
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exs = exs[4+exLen:]
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}
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j.ServerName = string(sni)
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j.Extensions = extensions
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j.EllipticCurves = ellipticCurves
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j.EllipticCurvePF = ellipticCurvePF
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j.Versions = versions
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j.SignatureAlgorithms = signatureAlgorithms
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return nil
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}
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// marshalJA3 into a byte string
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func (j *ClientHello) marshalJA3() {
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// An uint16 can contain numbers with up to 5 digits and an uint8 can contain numbers with up to 3 digits, but we
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// also need a byte for each separating character, except at the end.
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byteStringLen := 6*(1+len(j.CipherSuites)+len(j.Extensions)+len(j.EllipticCurves)) + 4*len(j.EllipticCurvePF) - 1
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byteString := make([]byte, 0, byteStringLen)
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// Version
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byteString = strconv.AppendUint(byteString, uint64(j.Version), 10)
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byteString = append(byteString, commaByte)
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// Cipher Suites
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if len(j.CipherSuites) != 0 {
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for _, val := range j.CipherSuites {
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if val&GreaseBitmask != 0x0A0A {
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continue
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}
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byteString = strconv.AppendUint(byteString, uint64(val), 10)
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byteString = append(byteString, dashByte)
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}
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// Replace last dash with a comma
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byteString[len(byteString)-1] = commaByte
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} else {
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byteString = append(byteString, commaByte)
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}
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// Extensions
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if len(j.Extensions) != 0 {
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for _, val := range j.Extensions {
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if val&GreaseBitmask != 0x0A0A {
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continue
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}
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byteString = strconv.AppendUint(byteString, uint64(val), 10)
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byteString = append(byteString, dashByte)
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}
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// Replace last dash with a comma
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byteString[len(byteString)-1] = commaByte
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} else {
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byteString = append(byteString, commaByte)
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}
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// Elliptic curves
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if len(j.EllipticCurves) != 0 {
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for _, val := range j.EllipticCurves {
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if val&GreaseBitmask != 0x0A0A {
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continue
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}
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byteString = strconv.AppendUint(byteString, uint64(val), 10)
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byteString = append(byteString, dashByte)
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}
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// Replace last dash with a comma
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byteString[len(byteString)-1] = commaByte
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} else {
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byteString = append(byteString, commaByte)
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}
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// ECPF
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if len(j.EllipticCurvePF) != 0 {
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for _, val := range j.EllipticCurvePF {
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byteString = strconv.AppendUint(byteString, uint64(val), 10)
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byteString = append(byteString, dashByte)
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}
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// Remove last dash
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byteString = byteString[:len(byteString)-1]
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}
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j.ja3ByteString = byteString
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}
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