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TlsInit: better X25519 key generation.

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GitOrigin-RevId: b7efb4bfd1d285a54292e5733c855d7693419af1
This commit is contained in:
levlam 2019-08-22 23:09:49 +03:00
parent 2e8ec529e9
commit d02f0ffba9
2 changed files with 54 additions and 5 deletions
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6
benchmark/check_tls.cpp
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@ -21,6 +21,8 @@
#include <map>
static td::BigNumContext context;
static bool is_quadratic_residue(const td::BigNum &a) {
// 2^255 - 19
td::BigNum mod =
@ -29,13 +31,12 @@ static bool is_quadratic_residue(const td::BigNum &a) {
td::BigNum pow =
td::BigNum::from_hex("3ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff6").move_as_ok();
static td::BigNumContext context;
td::BigNum r;
td::BigNum::mod_exp(r, a, pow, mod, context);
td::BigNum one = td::BigNum::from_decimal("1").move_as_ok();
td::BigNum::mod_add(r, r, one, mod, context);
std::string result = r.to_decimal();
td::string result = r.to_decimal();
CHECK(result == "0" || result == "1" || result == "2");
return result == "2";
}
@ -64,7 +65,6 @@ td::Result<TlsInfo> test_tls(const td::string &url) {
};
auto add_key = [&] {
td::string key(32, '\0');
td::BigNumContext context;
td::BigNum mod =
td::BigNum::from_hex("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed").move_as_ok();
while (true) {

53
td/mtproto/TlsInit.cpp
View File

@ -7,6 +7,7 @@
#include "td/mtproto/TlsInit.h"
#include "td/utils/as.h"
#include "td/utils/BigNum.h"
#include "td/utils/common.h"
#include "td/utils/crypto.h"
#include "td/utils/logging.h"
@ -35,7 +36,7 @@ void Grease::init(MutableSlice res) {
class TlsHello {
public:
struct Op {
enum class Type { String, Random, Zero, Domain, Grease, BeginScope, EndScope };
enum class Type { String, Random, Zero, Domain, Grease, Key, BeginScope, EndScope };
Type type;
int length;
int seed;
@ -80,6 +81,11 @@ class TlsHello {
res.type = Type::EndScope;
return res;
}
static Op key() {
Op res;
res.type = Type::Key;
return res;
}
};
static const TlsHello &get_default() {
@ -112,7 +118,7 @@ class TlsHello {
"\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"),
Op::grease(4),
Op::string("\x00\x01\x00\x00\x1d\x00\x20"),
Op::random(32),
Op::key(),
Op::string("\x00\x2d\x00\x02\x01\x01\x00\x2b\x00\x0b\x0a"),
Op::grease(6),
Op::string("\x03\x04\x03\x03\x03\x02\x03\x01\x00\x1b\x00\x03\x02\x00\x02"),
@ -193,6 +199,9 @@ class TlsHelloCalcLength {
}
size_ += 2;
break;
case Type::Key:
size_ += 32;
break;
case Type::BeginScope:
size_ += 2;
scope_offset_.push_back(size_);
@ -280,6 +289,33 @@ class TlsHelloStore {
dest_.remove_prefix(2);
break;
}
case Type::Key: {
BigNum mod = BigNum::from_hex("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed").move_as_ok();
BigNumContext big_num_context;
auto key = dest_.substr(0, 32);
while (true) {
Random::secure_bytes(key);
key[31] = static_cast<char>(key[31] & 127);
BigNum x = BigNum::from_le_binary(key);
if (!is_quadratic_residue(x)) {
continue;
}
BigNum y = x.clone();
BigNum coef = BigNum::from_decimal("486662").move_as_ok();
BigNum::mod_add(y, y, coef, mod, big_num_context);
BigNum::mod_mul(y, y, x, mod, big_num_context);
BigNum one = BigNum::from_decimal("1").move_as_ok();
BigNum::mod_add(y, y, one, mod, big_num_context);
BigNum::mod_mul(y, y, x, mod, big_num_context);
// y = x^3 + 486662 * x^2 + x
if (is_quadratic_residue(y)) {
break;
}
}
dest_.remove_prefix(32);
break;
}
case Type::BeginScope:
scope_offset_.push_back(get_offset());
dest_.remove_prefix(2);
@ -319,6 +355,19 @@ class TlsHelloStore {
MutableSlice dest_;
std::vector<size_t> scope_offset_;
static bool is_quadratic_residue(const BigNum &a) {
// 2^255 - 19
BigNum mod = BigNum::from_hex("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed").move_as_ok();
// (mod - 1) / 2 = 2^254 - 10
BigNum pow = BigNum::from_hex("3ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff6").move_as_ok();
BigNumContext context;
BigNum r;
BigNum::mod_exp(r, a, pow, mod, context);
return r.to_decimal() == "1";
}
size_t get_offset() const {
return data_.size() - dest_.size();
}