480 lines
14 KiB
C++
480 lines
14 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#include "td/mtproto/TlsInit.h"
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#include "td/utils/as.h"
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#include "td/utils/BigNum.h"
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#include "td/utils/common.h"
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#include "td/utils/crypto.h"
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#include "td/utils/logging.h"
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#include "td/utils/Random.h"
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#include "td/utils/Span.h"
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#include "td/utils/Time.h"
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#include <algorithm>
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#include <cstring>
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namespace td {
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namespace mtproto {
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void Grease::init(MutableSlice res) {
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Random::secure_bytes(res);
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for (auto &c : res) {
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c = static_cast<char>((c & 0xF0) + 0x0A);
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}
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for (size_t i = 1; i < res.size(); i += 2) {
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if (res[i] == res[i - 1]) {
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res[i] ^= 0x10;
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}
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}
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}
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class TlsHello {
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public:
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struct Op {
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enum class Type { String, Random, Zero, Domain, Grease, Key, BeginScope, EndScope };
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Type type;
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int length;
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int seed;
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std::string data;
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static Op string(Slice str) {
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Op res;
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res.type = Type::String;
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res.data = str.str();
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return res;
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}
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static Op random(int length) {
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Op res;
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res.type = Type::Random;
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res.length = length;
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return res;
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}
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static Op zero(int length) {
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Op res;
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res.type = Type::Zero;
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res.length = length;
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return res;
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}
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static Op domain() {
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Op res;
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res.type = Type::Domain;
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return res;
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}
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static Op grease(int seed) {
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Op res;
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res.type = Type::Grease;
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res.seed = seed;
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return res;
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}
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static Op begin_scope() {
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Op res;
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res.type = Type::BeginScope;
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return res;
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}
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static Op end_scope() {
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Op res;
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res.type = Type::EndScope;
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return res;
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}
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static Op key() {
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Op res;
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res.type = Type::Key;
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return res;
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}
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};
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static const TlsHello &get_default() {
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static TlsHello result = [] {
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TlsHello res;
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res.ops_ = {
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Op::string("\x16\x03\x01\x02\x00\x01\x00\x01\xfc\x03\x03"),
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Op::zero(32),
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Op::string("\x20"),
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Op::random(32),
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Op::string("\x00\x22"),
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Op::grease(0),
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Op::string("\x13\x01\x13\x02\x13\x03\xc0\x2b\xc0\x2f\xc0\x2c\xc0\x30\xcc\xa9\xcc\xa8\xc0\x13\xc0\x14\x00\x9c"
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"\x00\x9d\x00\x2f\x00\x35\x00\x0a\x01\x00\x01\x91"),
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Op::grease(2),
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Op::string("\x00\x00\x00\x00"),
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Op::begin_scope(),
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Op::begin_scope(),
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Op::string("\x00"),
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Op::begin_scope(),
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Op::domain(),
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Op::end_scope(),
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Op::end_scope(),
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Op::end_scope(),
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Op::string("\x00\x17\x00\x00\xff\x01\x00\x01\x00\x00\x0a\x00\x0a\x00\x08"),
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Op::grease(4),
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Op::string(
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"\x00\x1d\x00\x17\x00\x18\x00\x0b\x00\x02\x01\x00\x00\x23\x00\x00\x00\x10\x00\x0e\x00\x0c\x02\x68\x32\x08"
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"\x68\x74\x74\x70\x2f\x31\x2e\x31\x00\x05\x00\x05\x01\x00\x00\x00\x00\x00\x0d\x00\x14\x00\x12\x04\x03\x08"
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"\x04\x04\x01\x05\x03\x08\x05\x05\x01\x08\x06\x06\x01\x02\x01\x00\x12\x00\x00\x00\x33\x00\x2b\x00\x29"),
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Op::grease(4),
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Op::string("\x00\x01\x00\x00\x1d\x00\x20"),
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Op::key(),
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Op::string("\x00\x2d\x00\x02\x01\x01\x00\x2b\x00\x0b\x0a"),
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Op::grease(6),
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Op::string("\x03\x04\x03\x03\x03\x02\x03\x01\x00\x1b\x00\x03\x02\x00\x02"),
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Op::grease(3),
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Op::string("\x00\x01\x00\x00\x15")};
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res.grease_size_ = 7;
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return res;
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}();
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return result;
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}
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Span<Op> get_ops() const {
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return ops_;
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}
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size_t get_grease_size() const {
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return grease_size_;
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}
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private:
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std::vector<Op> ops_;
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size_t grease_size_;
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};
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class TlsHelloContext {
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public:
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TlsHelloContext(size_t grease_size, std::string domain) : grease_(grease_size, '\0'), domain_(std::move(domain)) {
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Grease::init(grease_);
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}
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char get_grease(size_t i) const {
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CHECK(i < grease_.size());
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return grease_[i];
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}
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size_t get_grease_size() const {
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return grease_.size();
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}
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Slice get_domain() const {
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return domain_;
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}
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private:
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std::string grease_;
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std::string domain_;
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};
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class TlsHelloCalcLength {
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public:
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void do_op(const TlsHello::Op &op, const TlsHelloContext *context) {
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if (status_.is_error()) {
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return;
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}
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using Type = TlsHello::Op::Type;
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switch (op.type) {
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case Type::String:
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size_ += op.data.size();
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break;
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case Type::Random:
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if (op.length <= 0 || op.length > 1024) {
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return on_error(Status::Error("Invalid random length"));
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}
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size_ += op.length;
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break;
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case Type::Zero:
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if (op.length <= 0 || op.length > 1024) {
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return on_error(Status::Error("Invalid zero length"));
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}
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size_ += op.length;
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break;
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case Type::Domain:
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CHECK(context);
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size_ += context->get_domain().size();
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break;
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case Type::Grease:
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CHECK(context);
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if (op.seed < 0 || static_cast<size_t>(op.seed) >= context->get_grease_size()) {
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return on_error(Status::Error("Invalid grease seed"));
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}
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size_ += 2;
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break;
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case Type::Key:
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size_ += 32;
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break;
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case Type::BeginScope:
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size_ += 2;
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scope_offset_.push_back(size_);
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break;
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case Type::EndScope: {
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if (scope_offset_.empty()) {
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return on_error(Status::Error("Unbalanced scopes"));
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}
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auto begin_offset = scope_offset_.back();
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scope_offset_.pop_back();
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auto end_offset = size_;
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auto size = end_offset - begin_offset;
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if (size >= (1 << 14)) {
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return on_error(Status::Error("Scope is too big"));
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}
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break;
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}
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default:
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UNREACHABLE();
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}
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}
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Result<size_t> finish() {
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if (size_ > 515) {
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on_error(Status::Error("Too long for zero padding"));
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}
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if (size_ < 11 + 32) {
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on_error(Status::Error("Too small for hash"));
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}
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int zero_pad = 515 - static_cast<int>(size_);
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using Op = TlsHello::Op;
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do_op(Op::begin_scope(), nullptr);
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do_op(Op::zero(zero_pad), nullptr);
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do_op(Op::end_scope(), nullptr);
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if (!scope_offset_.empty()) {
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on_error(Status::Error("Unbalanced scopes"));
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}
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TRY_STATUS(std::move(status_));
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return size_;
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}
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private:
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size_t size_{0};
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Status status_;
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std::vector<size_t> scope_offset_;
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void on_error(Status error) {
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if (status_.is_ok()) {
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status_ = std::move(error);
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}
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}
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};
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class TlsHelloStore {
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public:
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explicit TlsHelloStore(MutableSlice dest) : data_(dest), dest_(dest) {
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}
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void do_op(const TlsHello::Op &op, const TlsHelloContext *context) {
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using Type = TlsHello::Op::Type;
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switch (op.type) {
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case Type::String:
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dest_.copy_from(op.data);
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dest_.remove_prefix(op.data.size());
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break;
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case Type::Random:
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Random::secure_bytes(dest_.substr(0, op.length));
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dest_.remove_prefix(op.length);
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break;
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case Type::Zero:
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std::memset(dest_.begin(), 0, op.length);
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dest_.remove_prefix(op.length);
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break;
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case Type::Domain: {
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CHECK(context);
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auto domain = context->get_domain();
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dest_.copy_from(domain);
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dest_.remove_prefix(domain.size());
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break;
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}
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case Type::Grease: {
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CHECK(context)
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auto grease = context->get_grease(op.seed);
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dest_[0] = grease;
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dest_[1] = grease;
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dest_.remove_prefix(2);
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break;
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}
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case Type::Key: {
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BigNum mod = BigNum::from_hex("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed").move_as_ok();
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BigNumContext big_num_context;
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auto key = dest_.substr(0, 32);
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while (true) {
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Random::secure_bytes(key);
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key[31] = static_cast<char>(key[31] & 127);
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BigNum x = BigNum::from_binary(key);
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BigNum y = get_y2(x, mod, big_num_context);
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if (is_quadratic_residue(y)) {
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for (int i = 0; i < 3; i++) {
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x = get_double_x(x, mod, big_num_context);
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}
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key.copy_from(x.to_le_binary(32));
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break;
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}
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}
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dest_.remove_prefix(32);
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break;
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}
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case Type::BeginScope:
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scope_offset_.push_back(get_offset());
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dest_.remove_prefix(2);
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break;
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case Type::EndScope: {
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CHECK(!scope_offset_.empty());
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auto begin_offset = scope_offset_.back();
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scope_offset_.pop_back();
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auto end_offset = get_offset();
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size_t size = end_offset - begin_offset - 2;
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CHECK(size < (1 << 14));
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data_[begin_offset] = static_cast<char>((size >> 8) & 0xff);
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data_[begin_offset + 1] = static_cast<char>(size & 0xff);
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break;
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}
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default:
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UNREACHABLE();
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}
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}
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void finish(Slice secret, int32 unix_time) {
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int zero_pad = 515 - static_cast<int>(get_offset());
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using Op = TlsHello::Op;
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do_op(Op::begin_scope(), nullptr);
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do_op(Op::zero(zero_pad), nullptr);
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do_op(Op::end_scope(), nullptr);
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auto hash_dest = data_.substr(11, 32);
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hmac_sha256(secret, data_, hash_dest);
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int32 old = as<int32>(hash_dest.substr(28).data());
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as<int32>(hash_dest.substr(28).data()) = old ^ unix_time;
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CHECK(dest_.empty());
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}
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private:
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MutableSlice data_;
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MutableSlice dest_;
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std::vector<size_t> scope_offset_;
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static BigNum get_y2(BigNum &x, const BigNum &mod, BigNumContext &big_num_context) {
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// returns y = x^3 + 486662 * x^2 + x
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BigNum y = x.clone();
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BigNum coef = BigNum::from_decimal("486662").move_as_ok();
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BigNum::mod_add(y, y, coef, mod, big_num_context);
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BigNum::mod_mul(y, y, x, mod, big_num_context);
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BigNum one = BigNum::from_decimal("1").move_as_ok();
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BigNum::mod_add(y, y, one, mod, big_num_context);
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BigNum::mod_mul(y, y, x, mod, big_num_context);
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return y;
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}
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static BigNum get_double_x(BigNum &x, const BigNum &mod, BigNumContext &big_num_context) {
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// returns x_2 = (x^2 - 1)^2/(4*y^2)
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BigNum denominator = get_y2(x, mod, big_num_context);
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BigNum coef = BigNum::from_decimal("4").move_as_ok();
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BigNum::mod_mul(denominator, denominator, coef, mod, big_num_context);
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BigNum numerator;
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BigNum::mod_mul(numerator, x, x, mod, big_num_context);
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BigNum one = BigNum::from_decimal("1").move_as_ok();
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BigNum::mod_sub(numerator, numerator, one, mod, big_num_context);
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BigNum::mod_mul(numerator, numerator, numerator, mod, big_num_context);
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BigNum::mod_inverse(denominator, denominator, mod, big_num_context);
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BigNum::mod_mul(numerator, numerator, denominator, mod, big_num_context);
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return numerator;
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}
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static bool is_quadratic_residue(const BigNum &a) {
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// 2^255 - 19
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BigNum mod = BigNum::from_hex("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed").move_as_ok();
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// (mod - 1) / 2 = 2^254 - 10
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BigNum pow = BigNum::from_hex("3ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff6").move_as_ok();
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BigNumContext context;
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BigNum r;
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BigNum::mod_exp(r, a, pow, mod, context);
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return r.to_decimal() == "1";
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}
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size_t get_offset() const {
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return data_.size() - dest_.size();
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}
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};
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class TlsObfusaction {
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public:
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static std::string generate_header(std::string domain, Slice secret, int32 unix_time) {
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CHECK(!domain.empty());
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CHECK(secret.size() == 16);
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auto &hello = TlsHello::get_default();
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TlsHelloContext context(hello.get_grease_size(), std::move(domain));
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TlsHelloCalcLength calc_length;
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for (auto &op : hello.get_ops()) {
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calc_length.do_op(op, &context);
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}
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auto length = calc_length.finish().move_as_ok();
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std::string data(length, '\0');
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TlsHelloStore storer(data);
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for (auto &op : hello.get_ops()) {
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storer.do_op(op, &context);
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}
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storer.finish(secret, unix_time);
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return data;
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}
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};
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void TlsInit::send_hello() {
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auto hello =
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TlsObfusaction::generate_header(username_, password_, static_cast<int32>(Time::now() + server_time_difference_));
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hello_rand_ = hello.substr(11, 32);
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fd_.output_buffer().append(hello);
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state_ = State::WaitHelloResponse;
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}
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Status TlsInit::wait_hello_response() {
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auto it = fd_.input_buffer().clone();
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for (auto first : {Slice("\x16\x03\x03"), Slice("\x14\x03\x03\x00\x01\x01\x17\x03\x03")}) {
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if (it.size() < first.size() + 2) {
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return Status::OK();
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}
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std::string got_first(first.size(), '\0');
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it.advance(first.size(), got_first);
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if (first != got_first) {
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return Status::Error("First part of response to hello is invalid");
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}
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uint8 tmp[2];
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it.advance(2, MutableSlice(tmp, 2));
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size_t skip_size = (tmp[0] << 8) + tmp[1];
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if (it.size() < skip_size) {
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return Status::OK();
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}
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it.advance(skip_size);
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}
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auto response = fd_.input_buffer().cut_head(it.begin().clone()).move_as_buffer_slice();
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auto response_rand_slice = response.as_slice().substr(11, 32);
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auto response_rand = response_rand_slice.str();
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std::fill(response_rand_slice.begin(), response_rand_slice.end(), '\0');
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std::string hash_dest(32, '\0');
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hmac_sha256(password_, PSLICE() << hello_rand_ << response.as_slice(), hash_dest);
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if (hash_dest != response_rand) {
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return td::Status::Error("Response hash mismatch");
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}
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stop();
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return Status::OK();
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}
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Status TlsInit::loop_impl() {
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switch (state_) {
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case State::SendHello:
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send_hello();
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break;
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case State::WaitHelloResponse:
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TRY_STATUS(wait_hello_response());
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break;
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}
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return Status::OK();
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}
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} // namespace mtproto
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} // namespace td
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