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120 lines
5.5 KiB
Go
120 lines
5.5 KiB
Go
// Fingerprint of Chrome 112
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package client
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import (
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"encoding/binary"
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"math/rand"
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"github.com/cbeuw/Cloak/internal/common"
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)
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type Chrome struct{}
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func makeGREASE() []byte {
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// see https://tools.ietf.org/html/draft-davidben-tls-grease-01
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// This is exclusive to Chrome.
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var one [1]byte
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common.CryptoRandRead(one[:])
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sixteenth := one[0] % 16
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monoGREASE := sixteenth*16 + 0xA
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doubleGREASE := []byte{monoGREASE, monoGREASE}
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return doubleGREASE
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}
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func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
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makeSupportedGroups := func() []byte {
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suppGroupListLen := []byte{0x00, 0x08}
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ret := make([]byte, 2+8)
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copy(ret[0:2], suppGroupListLen)
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copy(ret[2:4], makeGREASE())
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copy(ret[4:], []byte{0x00, 0x1d, 0x00, 0x17, 0x00, 0x18})
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return ret
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}
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makeKeyShare := func(hidden []byte) []byte {
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ret := make([]byte, 43)
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ret[0], ret[1] = 0x00, 0x29 // length 41
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copy(ret[2:4], makeGREASE())
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ret[4], ret[5] = 0x00, 0x01 // length 1
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ret[6] = 0x00
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ret[7], ret[8] = 0x00, 0x1d // group x25519
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ret[9], ret[10] = 0x00, 0x20 // length 32
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copy(ret[11:43], hidden)
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return ret
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}
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shuffle := func(exts [][]byte) {
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var qword [8]byte
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common.CryptoRandRead(qword[:])
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seed := int64(binary.BigEndian.Uint64(qword[:]))
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rand.Seed(seed)
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rand.Shuffle(len(exts), func(i, j int) { exts[i], exts[j] = exts[j], exts[i] })
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}
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// extension length is always 403, and server name length is variable
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var ext [18][]byte
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ext[0] = addExtRec(makeGREASE(), nil) // First GREASE
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// Start shufflable extensions: https://chromestatus.com/feature/5124606246518784
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ext[1] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName)) // server name indication
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ext[2] = addExtRec([]byte{0x00, 0x17}, nil) // extended_master_secret
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ext[3] = addExtRec([]byte{0xff, 0x01}, []byte{0x00}) // renegotiation_info
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ext[4] = addExtRec([]byte{0x00, 0x0a}, makeSupportedGroups()) // supported groups
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ext[5] = addExtRec([]byte{0x00, 0x0b}, []byte{0x01, 0x00}) // ec point formats
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ext[6] = addExtRec([]byte{0x00, 0x23}, nil) // Session tickets
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ext[7] = addExtRec([]byte{0x00, 0x10}, decodeHex("000c02683208687474702f312e31")) // app layer proto negotiation
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ext[8] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00}) // status request
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ext[9] = addExtRec([]byte{0x00, 0x0d}, decodeHex("001004030804040105030805050108060601")) // Signature Algorithms
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ext[10] = addExtRec([]byte{0x00, 0x12}, nil) // signed cert timestamp
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ext[11] = addExtRec([]byte{0x00, 0x33}, makeKeyShare(keyShare)) // key share
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ext[12] = addExtRec([]byte{0x00, 0x2d}, []byte{0x01, 0x01}) // psk key exchange modes
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suppVersions := decodeHex("069A9A03040303") // 9A9A needs to be a GREASE
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copy(suppVersions[1:3], makeGREASE())
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ext[13] = addExtRec([]byte{0x00, 0x2b}, suppVersions) // supported versions
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ext[14] = addExtRec([]byte{0x00, 0x1b}, []byte{0x02, 0x00, 0x02}) // compress certificate
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ext[15] = addExtRec([]byte{0x44, 0x69}, decodeHex("0003026832")) // application settings
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// End shufflable extensions
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shuffle(ext[1:16])
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ext[16] = addExtRec(makeGREASE(), []byte{0x00}) // Last GREASE
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// len(ext[1]) + len(all other ext) + len(ext[17]) = 403
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// len(all other ext) = 175
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// len(ext[17]) = 228 - len(ext[1])
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// 2+2+len(padding) = 228 - len(ext[1])
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// len(padding) = 224 - len(ext[1])
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ext[17] = addExtRec([]byte{0x00, 0x15}, make([]byte, 224-len(ext[1]))) // padding
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var ret []byte
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for _, e := range ext {
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ret = append(ret, e...)
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}
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return ret
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}
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func (c *Chrome) composeClientHello(hd clientHelloFields) (ch []byte) {
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var clientHello [12][]byte
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clientHello[0] = []byte{0x01} // handshake type
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clientHello[1] = []byte{0x00, 0x01, 0xfc} // length 508
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clientHello[2] = []byte{0x03, 0x03} // client version
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clientHello[3] = hd.random // random
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clientHello[4] = []byte{0x20} // session id length 32
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clientHello[5] = hd.sessionId // session id
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clientHello[6] = []byte{0x00, 0x20} // cipher suites length 32
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clientHello[7] = append(makeGREASE(), decodeHex("130113021303c02bc02fc02cc030cca9cca8c013c014009c009d002f0035")...) // cipher suites
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clientHello[8] = []byte{0x01} // compression methods length 1
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clientHello[9] = []byte{0x00} // compression methods
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extensions := c.composeExtensions(hd.serverName, hd.x25519KeyShare)
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clientHello[10] = []byte{0x00, 0x00}
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binary.BigEndian.PutUint16(clientHello[10], uint16(len(extensions))) // extension length
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clientHello[11] = extensions
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var ret []byte
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for _, c := range clientHello {
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ret = append(ret, c...)
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}
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return ret
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}
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