Files
mautrix-telegram/pkg/gotd/crypto/srp/new_hash.go
T
2025-06-27 20:03:37 -07:00

55 lines
1.9 KiB
Go

package srp
import (
"io"
"math/big"
"github.com/go-faster/errors"
)
// computeXV computes following numbers
//
// `x = PH2(password, salt1, salt2)`
// `v = pow(g, x) mod p`
//
// TDLib uses terms `clientSalt` for `salt1` and `serverSalt` for `salt2`.
func (s SRP) computeXV(password, clientSalt, serverSalt []byte, g, p *big.Int) (x, v *big.Int) {
// `x = PH2(password, salt1, salt2)`
x = new(big.Int).SetBytes(s.secondary(password, clientSalt, serverSalt))
// `v = pow(g, x) mod p`
v = new(big.Int).Exp(g, x, p)
return x, v
}
// NewHash computes new user password hash using parameters from server.
//
// See https://core.telegram.org/api/srp#setting-a-new-2fa-password.
//
// TDLib implementation:
// See https://github.com/tdlib/td/blob/fa8feefed70d64271945e9d5fd010b957d93c8cd/td/telegram/PasswordManager.cpp#L57.
//
// TDesktop implementation:
// See https://github.com/telegramdesktop/tdesktop/blob/v3.4.8/Telegram/SourceFiles/core/core_cloud_password.cpp#L68.
func (s SRP) NewHash(password []byte, i Input) (hash, newSalt []byte, _ error) {
// Generate a new new_password_hash using the KDF algorithm specified in the new_settings,
// just append 32 sufficiently random bytes to the salt1, first. Proceed as for checking passwords with SRP,
// just stop at the generation of the v parameter, and use it as new_password_hash:
p := new(big.Int).SetBytes(i.P)
if err := checkInput(i.G, p); err != nil {
return nil, nil, errors.Wrap(err, "validate algo")
}
// Make a copy.
newClientSalt := append([]byte(nil), i.Salt1...)
newClientSalt = append(newClientSalt, make([]byte, 32)...)
// ... append 32 sufficiently random bytes to the salt1 ...
if _, err := io.ReadFull(s.random, newClientSalt[len(newClientSalt)-32:]); err != nil {
return nil, nil, err
}
_, v := s.computeXV(password, newClientSalt, i.Salt2, big.NewInt(int64(i.G)), p)
// As usual in big endian form, padded to 2048 bits.
padded, _ := s.pad256FromBig(v)
return padded[:], newClientSalt, nil
}