From 6732fc7fde22d37a78318d350baaeb1c03158fab Mon Sep 17 00:00:00 2001 From: naughtyfox Date: Mon, 12 Nov 2018 20:46:00 +0300 Subject: Fix issue 4793 - M/N multisig transaction signature --- src/wallet/wallet2.cpp | 77 +++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 61 insertions(+), 16 deletions(-) (limited to 'src/wallet/wallet2.cpp') diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp index ebf857b78..8fcecb402 100644 --- a/src/wallet/wallet2.cpp +++ b/src/wallet/wallet2.cpp @@ -67,6 +67,7 @@ using namespace epee; #include "common/json_util.h" #include "memwipe.h" #include "common/base58.h" +#include "common/combinator.h" #include "common/dns_utils.h" #include "common/notify.h" #include "common/perf_timer.h" @@ -177,6 +178,20 @@ namespace return public_keys; } + + bool keys_intersect(const std::unordered_set& s1, const std::unordered_set& s2) + { + if (s1.empty() || s2.empty()) + return false; + + for (const auto& e: s1) + { + if (s2.find(e) != s2.end()) + return true; + } + + return false; + } } namespace @@ -6045,7 +6060,7 @@ bool wallet2::sign_multisig_tx(multisig_tx_set &exported_txs, std::vector multisig_signers; size_t n_multisig_txes = 0; + std::vector> ignore_sets; if (m_multisig && !m_transfers.empty()) { const crypto::public_key local_signer = get_multisig_signer_public_key(); size_t n_available_signers = 1; + + // At this step we need to define set of participants available for signature, + // i.e. those of them who exchanged with multisig info's for (const crypto::public_key &signer: m_multisig_signers) { if (signer == local_signer) continue; - multisig_signers.push_front(signer); for (const auto &i: m_transfers[0].m_multisig_info) { if (i.m_signer == signer) { - multisig_signers.pop_front(); multisig_signers.push_back(signer); ++n_available_signers; break; } } } - multisig_signers.push_back(local_signer); + // n_available_signers includes the transaction creator, but multisig_signers doesn't MDEBUG("We can use " << n_available_signers << "/" << m_multisig_signers.size() << " other signers"); - THROW_WALLET_EXCEPTION_IF(n_available_signers+1 < m_multisig_threshold, error::multisig_import_needed); - n_multisig_txes = n_available_signers == m_multisig_signers.size() ? m_multisig_threshold : 1; + THROW_WALLET_EXCEPTION_IF(n_available_signers < m_multisig_threshold, error::multisig_import_needed); + if (n_available_signers > m_multisig_threshold) + { + // If there more potential signers (those who exchanged with multisig info) + // than threshold needed some of them should be skipped since we don't know + // who will sign tx and who won't. Hence we don't contribute their LR pairs to the signature. + + // We create as many transactions as many combinations of excluded signers may be. + // For example, if we have 2/4 wallet and wallets are: A, B, C and D. Let A be + // transaction creator, so we need just 1 signature from set of B, C, D. + // Using "excluding" logic here we have to exclude 2-of-3 wallets. Combinations go as follows: + // BC, BD, and CD. We save these sets to use later and counting the number of required txs. + tools::Combinator c(std::vector(multisig_signers.begin(), multisig_signers.end())); + auto ignore_combinations = c.combine(multisig_signers.size() + 1 - m_multisig_threshold); + for (const auto& combination: ignore_combinations) + { + ignore_sets.push_back(std::unordered_set(combination.begin(), combination.end())); + } + + n_multisig_txes = ignore_sets.size(); + } + else + { + // If we have exact count of signers just to fit in threshold we don't exclude anyone and create 1 transaction + n_multisig_txes = 1; + } MDEBUG("We will create " << n_multisig_txes << " txes"); } @@ -7603,8 +7644,8 @@ void wallet2::transfer_selected_rct(std::vector() : ignore_sets.front(); + src.multisig_kLRki = get_multisig_composite_kLRki(idx, ignore_set, used_L, used_L); } else src.multisig_kLRki = rct::multisig_kLRki({rct::zero(), rct::zero(), rct::zero(), rct::zero()}); @@ -7666,7 +7707,7 @@ void wallet2::transfer_selected_rct(std::vector multisig_sigs; if (m_multisig) { - crypto::public_key ignore = m_multisig_threshold == m_multisig_signers.size() ? crypto::null_pkey : multisig_signers.front(); + auto ignore = ignore_sets.empty() ? std::unordered_set() : ignore_sets.front(); multisig_sigs.push_back({tx.rct_signatures, ignore, used_L, std::unordered_set(), msout}); if (m_multisig_threshold < m_multisig_signers.size()) @@ -7674,7 +7715,7 @@ void wallet2::transfer_selected_rct(std::vector new_used_L; size_t src_idx = 0; @@ -7682,7 +7723,7 @@ void wallet2::transfer_selected_rct(std::vector(), msout}); + multisig_sigs.push_back({ms_tx.rct_signatures, ignore_sets[ignore_index], new_used_L, std::unordered_set(), msout}); ms_tx.rct_signatures = tx.rct_signatures; THROW_WALLET_EXCEPTION_IF(cryptonote::get_transaction_hash(ms_tx) != cryptonote::get_transaction_hash(tx), error::wallet_internal_error, "Multisig txes differ by more than the signatures"); @@ -11265,7 +11306,7 @@ rct::multisig_kLRki wallet2::get_multisig_kLRki(size_t n, const rct::key &k) con return kLRki; } //---------------------------------------------------------------------------------------------------- -rct::multisig_kLRki wallet2::get_multisig_composite_kLRki(size_t n, const crypto::public_key &ignore, std::unordered_set &used_L, std::unordered_set &new_used_L) const +rct::multisig_kLRki wallet2::get_multisig_composite_kLRki(size_t n, const std::unordered_set &ignore_set, std::unordered_set &used_L, std::unordered_set &new_used_L) const { CHECK_AND_ASSERT_THROW_MES(n < m_transfers.size(), "Bad transfer index"); @@ -11276,8 +11317,9 @@ rct::multisig_kLRki wallet2::get_multisig_composite_kLRki(size_t n, const crypto size_t n_signers_used = 1; for (const auto &p: m_transfers[n].m_multisig_info) { - if (p.m_signer == ignore) + if (ignore_set.find(p.m_signer) != ignore_set.end()) continue; + for (const auto &lr: p.m_LR) { if (used_L.find(lr.m_L) != used_L.end()) @@ -11336,7 +11378,10 @@ cryptonote::blobdata wallet2::export_multisig() info[n].m_partial_key_images.push_back(ki); } - size_t nlr = m_multisig_threshold < m_multisig_signers.size() ? m_multisig_threshold - 1 : 1; + // Wallet tries to create as many transactions as many signers combinations. We calculate the maximum number here as follows: + // if we have 2/4 wallet with signers: A, B, C, D and A is a transaction creator it will need to pick up 1 signer from 3 wallets left. + // That means counting combinations for excluding 2-of-3 wallets (k = total signers count - threshold, n = total signers count - 1). + size_t nlr = tools::combinations_count(m_multisig_signers.size() - m_multisig_threshold, m_multisig_signers.size() - 1); for (size_t m = 0; m < nlr; ++m) { td.m_multisig_k.push_back(rct::skGen()); -- cgit v1.2.3