trezor-firmware/firmware/stellar.c

/*
 * This file is part of the TREZOR project.
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Stellar signing workflow:
 *  1. Client sends a StellarSignTx method to the device with transaction header information
 *  2. Device confirms transaction details with the user and requests first operation
 *  3. Client sends protobuf message with details about the operation to sign
 *  4. Device confirms operation with user
 *  5a. If there are more operations in the transaction, device responds with StellarTxOpRequest. Go to 3
 *  5b. If the operation is the last one, device responds with StellarSignedTx
 */

#include <stdbool.h>
#include <time.h>
#include "messages.h"
#include "messages.pb.h"
#include "stellar.h"
#include "bip32.h"
#include "crypto.h"
#include "layout2.h"
#include "gettext.h"
#include "bignum.h"
#include "oled.h"
#include "base32.h"
#include "storage.h"
#include "fsm.h"
#include "protect.h"
#include "util.h"
#include "layout2.h"
#include "fonts.h"
#include "memzero.h"

static bool stellar_signing = false;
static StellarTransaction stellar_activeTx;

/*
 * Starts the signing process and parses the transaction header
 */
void stellar_signingInit(StellarSignTx *msg)
{
    memset(&stellar_activeTx, 0, sizeof(StellarTransaction));
    stellar_signing = true;
    // Initialize signing context
    sha256_Init(&(stellar_activeTx.sha256_ctx));

    // Calculate sha256 for network passphrase
    // max length defined in messages.options
    uint8_t network_hash[32];
    sha256_Raw((uint8_t *)msg->network_passphrase, strnlen(msg->network_passphrase, 1024), network_hash);

    uint8_t tx_type_bytes[4] = { 0x00, 0x00, 0x00, 0x02 };

    // Copy some data into the active tx
    stellar_activeTx.num_operations = msg->num_operations;

    // Start building what will be signed:
    // sha256 of:
    //  sha256(network passphrase)
    //  4-byte unsigned big-endian int type constant (2 for tx)
    //  remaining bytes are operations added in subsequent messages
    stellar_hashupdate_bytes(network_hash, sizeof(network_hash));
    stellar_hashupdate_bytes(tx_type_bytes, sizeof(tx_type_bytes));

    // Public key comes from deriving the specified account path
    HDNode *node = stellar_deriveNode(msg->address_n, msg->address_n_count);
    if (!node) {
        // TODO: bail on error
        return;
    }
    memcpy(&(stellar_activeTx.signing_pubkey), node->public_key + 1, sizeof(stellar_activeTx.signing_pubkey));

    stellar_activeTx.address_n_count = msg->address_n_count;
    // todo: fix sizeof check
    memcpy(&(stellar_activeTx.address_n), &(msg->address_n), sizeof(stellar_activeTx.address_n));

    // Hash: public key
    stellar_hashupdate_address(node->public_key + 1);

    // Hash: fee
    stellar_hashupdate_uint32(msg->fee);

    // Hash: sequence number
    stellar_hashupdate_uint64(msg->sequence_number);

    // Timebounds are only present if timebounds_start or timebounds_end is non-zero
    uint8_t has_timebounds = (msg->timebounds_start > 0 || msg->timebounds_end > 0);
    if (has_timebounds) {
        // Hash: the "has timebounds?" boolean
        stellar_hashupdate_bool(true);

        // Timebounds are sent as uint32s since that's all we can display, but they must be hashed as
        // 64-bit values
        stellar_hashupdate_uint32(0);
        stellar_hashupdate_uint32(msg->timebounds_start);

        stellar_hashupdate_uint32(0);
        stellar_hashupdate_uint32(msg->timebounds_end);
    }
    // No timebounds, hash a false boolean
    else {
        stellar_hashupdate_bool(false);
    }

    // Hash: memo
    stellar_hashupdate_uint32(msg->memo_type);
    switch (msg->memo_type) {
        // None, nothing else to do
        case 0:
            break;
        // Text: 4 bytes (size) + up to 28 bytes
        case 1:
            stellar_hashupdate_string((unsigned char*)&(msg->memo_text), strnlen(msg->memo_text, 28));
            break;
        // ID (8 bytes, uint64)
        case 2:
            stellar_hashupdate_uint64(msg->memo_id);
            break;
        // Hash and return are the same data structure (32 byte tx hash)
        case 3:
        case 4:
            stellar_hashupdate_bytes(msg->memo_hash.bytes, msg->memo_hash.size);
            break;
        default:
            break;
    }

    // Hash: number of operations
    stellar_hashupdate_uint32(msg->num_operations);

    // Determine what type of network this transaction is for
    if (strncmp("Public Global Stellar Network ; September 2015", msg->network_passphrase, 1024) == 0) {
        stellar_activeTx.network_type = 1;
    }
    else if (strncmp("Test SDF Network ; September 2015", msg->network_passphrase, 1024) == 0) {
        stellar_activeTx.network_type = 2;
    }
    else {
        stellar_activeTx.network_type = 3;
    }
}

bool stellar_confirmSourceAccount(bool has_source_account, char *str_account)
{
    if (!has_source_account) {
        stellar_hashupdate_bool(false);
        return true;
    }

    // Convert account string to public key bytes
    uint8_t bytes[32];
    if (!stellar_getAddressBytes(str_account, bytes)) {
        return false;
    }

    const char **str_addr_rows = stellar_lineBreakAddress(bytes);

    stellar_layoutTransactionDialog(
        _("Op src account OK?"),
        NULL,
        str_addr_rows[0],
        str_addr_rows[1],
        str_addr_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash: source account
    stellar_hashupdate_address(bytes);

    return true;
}

bool stellar_confirmCreateAccountOp(StellarCreateAccountOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(0);

    // Validate new account and convert to bytes
    uint8_t new_account_bytes[STELLAR_KEY_SIZE];
    if (!stellar_getAddressBytes(msg->new_account, new_account_bytes)) {
        stellar_signingAbort(_("Invalid destination account"));
        return false;
    }

    const char **str_addr_rows = stellar_lineBreakAddress(new_account_bytes);

    // Amount being funded
    char str_amount_line[32];
    char str_amount[32];
    stellar_format_stroops(msg->starting_balance, str_amount, sizeof(str_amount));

    strlcpy(str_amount_line, _("With "), sizeof(str_amount_line));
    strlcat(str_amount_line, str_amount, sizeof(str_amount_line));
    strlcat(str_amount_line, _(" XLM"), sizeof(str_amount_line));

    stellar_layoutTransactionDialog(
        _("Create account: "),
        str_addr_rows[0],
        str_addr_rows[1],
        str_addr_rows[2],
        str_amount_line
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash: address
    stellar_hashupdate_address(new_account_bytes);
    // Hash: starting amount
    stellar_hashupdate_uint64(msg->starting_balance);

    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmPaymentOp(StellarPaymentOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(1);

    // Validate destination account and convert to bytes
    uint8_t destination_account_bytes[STELLAR_KEY_SIZE];
    if (!stellar_getAddressBytes(msg->destination_account, destination_account_bytes)) {
        stellar_signingAbort(_("Invalid destination account"));
        return false;
    }

    const char **str_addr_rows = stellar_lineBreakAddress(destination_account_bytes);

    // To: G...
    char str_to[32];
    strlcpy(str_to, _("To: "), sizeof(str_to));
    strlcat(str_to, str_addr_rows[0], sizeof(str_to));

    char str_asset_row[32];
    memset(str_asset_row, 0, sizeof(str_asset_row));
    stellar_format_asset(&(msg->asset), str_asset_row, sizeof(str_asset_row));

    char str_pay_amount[32];
    char str_amount[32];
    stellar_format_stroops(msg->amount, str_amount, sizeof(str_amount));

    strlcpy(str_pay_amount, _("Pay "), sizeof(str_pay_amount));
    strlcat(str_pay_amount, str_amount, sizeof(str_pay_amount));

    stellar_layoutTransactionDialog(
        str_pay_amount,
        str_asset_row,
        str_to,
        str_addr_rows[1],
        str_addr_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash destination
    stellar_hashupdate_address(destination_account_bytes);
    // asset
    stellar_hashupdate_asset(&(msg->asset));
    // amount (even though amount is signed it doesn't matter for hashing)
    stellar_hashupdate_uint64(msg->amount);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmPathPaymentOp(StellarPathPaymentOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(2);

    // Validate destination account and convert to bytes
    uint8_t destination_account_bytes[STELLAR_KEY_SIZE];
    if (!stellar_getAddressBytes(msg->destination_account, destination_account_bytes)) {
        stellar_signingAbort(_("Invalid destination account"));
        return false;
    }
    const char **str_dest_rows = stellar_lineBreakAddress(destination_account_bytes);

    // To: G...
    char str_to[32];
    strlcpy(str_to, _("To: "), sizeof(str_to));
    strlcat(str_to, str_dest_rows[0], sizeof(str_to));

    char str_send_asset[32];
    char str_dest_asset[32];
    stellar_format_asset(&(msg->send_asset), str_send_asset, sizeof(str_send_asset));
    stellar_format_asset(&(msg->destination_asset), str_dest_asset, sizeof(str_dest_asset));

    char str_pay_amount[32];
    char str_amount[32];
    stellar_format_stroops(msg->destination_amount, str_amount, sizeof(str_amount));

    strlcpy(str_pay_amount, _("Path Pay "), sizeof(str_pay_amount));
    strlcat(str_pay_amount, str_amount, sizeof(str_pay_amount));

    // Confirm what the receiver will get
    /*
    Path Pay 100
    JPY (G1234ABCDEF)
    To: G....
    ....
    ....
    */
    stellar_layoutTransactionDialog(
        str_pay_amount,
        str_dest_asset,
        str_to,
        str_dest_rows[1],
        str_dest_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Confirm what the sender is using to pay
    char str_source_amount[32];
    char str_source_number[32];
    stellar_format_stroops(msg->send_max, str_source_number, sizeof(str_source_number));

    strlcpy(str_source_amount, _("Pay Using "), sizeof(str_source_amount));
    strlcat(str_source_amount, str_source_number, sizeof(str_source_amount));

    stellar_layoutTransactionDialog(
        str_source_amount,
        str_send_asset,
        NULL,
        _("This is the amount debited"),
        _("from your account.")
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }
    // Note: no confirmation for intermediate steps since they don't impact the user

    // Hash send asset
    stellar_hashupdate_asset(&(msg->send_asset));
    // send max (signed vs. unsigned doesn't matter wrt hashing)
    stellar_hashupdate_uint64(msg->send_max);
    // destination account
    stellar_hashupdate_address(destination_account_bytes);
    // destination asset
    stellar_hashupdate_asset(&(msg->destination_asset));
    // destination amount
    stellar_hashupdate_uint64(msg->destination_amount);

    // paths are stored as an array so hash the number of elements as a uint32
    stellar_hashupdate_uint32(msg->paths_count);
    for (uint8_t i=0; i < msg->paths_count; i++) {
        stellar_hashupdate_asset(&(msg->paths[i]));
    }

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmManageOfferOp(StellarManageOfferOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(3);

    // New Offer / Delete #123 / Update #123
    char str_offer[32];
    if (msg->offer_id == 0) {
        strlcpy(str_offer, _("New Offer"), sizeof(str_offer));
    }
    else {
        char str_offer_id[20];
        stellar_format_uint64(msg->offer_id, str_offer_id, sizeof(str_offer_id));

        if (msg->amount == 0) {
            strlcpy(str_offer, _("Delete #"), sizeof(str_offer));
        }
        else {
            strlcpy(str_offer, _("Update #"), sizeof(str_offer));
        }

        strlcat(str_offer, str_offer_id, sizeof(str_offer));
    }

    char str_selling[32];
    char str_sell_amount[32];
    char str_selling_asset[32];

    stellar_format_asset(&(msg->selling_asset), str_selling_asset, sizeof(str_selling_asset));
    stellar_format_stroops(msg->amount, str_sell_amount, sizeof(str_sell_amount));

    /*
     Sell 200
     XLM (Native Asset)
    */
    strlcpy(str_selling, _("Sell "), sizeof(str_selling));
    strlcat(str_selling, str_sell_amount, sizeof(str_selling));

    char str_buying[32];
    char str_buying_asset[32];
    char str_price[17];

    stellar_format_asset(&(msg->buying_asset), str_buying_asset, sizeof(str_buying_asset));
    stellar_format_price(msg->price_n, msg->price_d, str_price, sizeof(str_price));

    /*
     For 0.675952 Per
     USD (G12345678)
     */
    strlcpy(str_buying, _("For "), sizeof(str_buying));
    strlcat(str_buying, str_price, sizeof(str_buying));
    strlcat(str_buying, _(" Per"), sizeof(str_buying));

    stellar_layoutTransactionDialog(
        str_offer,
        str_selling,
        str_selling_asset,
        str_buying,
        str_buying_asset
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash selling asset
    stellar_hashupdate_asset(&(msg->selling_asset));
    // buying asset
    stellar_hashupdate_asset(&(msg->buying_asset));
    // amount to sell (signed vs. unsigned doesn't matter wrt hashing)
    stellar_hashupdate_uint64(msg->amount);
    // numerator
    stellar_hashupdate_uint32(msg->price_n);
    // denominator
    stellar_hashupdate_uint32(msg->price_d);
    // offer ID
    stellar_hashupdate_uint64(msg->offer_id);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmCreatePassiveOfferOp(StellarCreatePassiveOfferOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(4);

    // New Offer / Delete #123 / Update #123
    char str_offer[32];
    if (msg->amount == 0) {
        strlcpy(str_offer, _("Delete Passive Offer"), sizeof(str_offer));
    }
    else {
        strlcpy(str_offer, _("New Passive Offer"), sizeof(str_offer));
    }

    char str_selling[32];
    char str_sell_amount[32];
    char str_selling_asset[32];

    stellar_format_asset(&(msg->selling_asset), str_selling_asset, sizeof(str_selling_asset));
    stellar_format_stroops(msg->amount, str_sell_amount, sizeof(str_sell_amount));

    /*
     Sell 200
     XLM (Native Asset)
    */
    strlcpy(str_selling, _("Sell "), sizeof(str_selling));
    strlcat(str_selling, str_sell_amount, sizeof(str_selling));

    char str_buying[32];
    char str_buying_asset[32];
    char str_price[17];

    stellar_format_asset(&(msg->buying_asset), str_buying_asset, sizeof(str_buying_asset));
    stellar_format_price(msg->price_n, msg->price_d, str_price, sizeof(str_price));

    /*
     For 0.675952 Per
     USD (G12345678)
     */
    strlcpy(str_buying, _("For "), sizeof(str_buying));
    strlcat(str_buying, str_price, sizeof(str_buying));
    strlcat(str_buying, _(" Per"), sizeof(str_buying));

    stellar_layoutTransactionDialog(
        str_offer,
        str_selling,
        str_selling_asset,
        str_buying,
        str_buying_asset
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash selling asset
    stellar_hashupdate_asset(&(msg->selling_asset));
    // buying asset
    stellar_hashupdate_asset(&(msg->buying_asset));
    // amount to sell (signed vs. unsigned doesn't matter wrt hashing)
    stellar_hashupdate_uint64(msg->amount);
    // numerator
    stellar_hashupdate_uint32(msg->price_n);
    // denominator
    stellar_hashupdate_uint32(msg->price_d);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmSetOptionsOp(StellarSetOptionsOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(5);

    // Something like Set Inflation Destination
    char str_title[32];
    char rows[4][32];
    int row_idx = 0;
    memset(rows, 0, sizeof(rows));

    // Inflation destination
    stellar_hashupdate_bool(msg->has_inflation_destination_account);
    if (msg->has_inflation_destination_account) {
        strlcpy(str_title, _("Set Inflation Destination"), sizeof(str_title));

        // Validate account and convert to bytes
        uint8_t inflation_destination_account_bytes[STELLAR_KEY_SIZE];
        if (!stellar_getAddressBytes(msg->inflation_destination_account, inflation_destination_account_bytes)) {
            stellar_signingAbort(_("Invalid inflation destination account"));
            return false;
        }
        const char **str_addr_rows = stellar_lineBreakAddress(inflation_destination_account_bytes);

        stellar_layoutTransactionDialog(
            str_title,
            NULL,
            str_addr_rows[0],
            str_addr_rows[1],
            str_addr_rows[2]
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return false;
        }

        // address
        stellar_hashupdate_address(inflation_destination_account_bytes);
    }

    // Clear flags
    stellar_hashupdate_bool(msg->has_clear_flags);
    if (msg->has_clear_flags) {
        strlcpy(str_title, _("Clear Flag(s)"), sizeof(str_title));

        // Auth required
        if (msg->clear_flags & 0x01) {
            strlcpy(rows[row_idx], _("AUTH_REQUIRED"), sizeof(rows[row_idx]));
            row_idx++;
        }
        // Auth revocable
        if (msg->clear_flags & 0x02) {
            strlcpy(rows[row_idx], _("AUTH_REVOCABLE"), sizeof(rows[row_idx]));
            row_idx++;
        }

        stellar_layoutTransactionDialog(
            str_title,
            rows[0],
            rows[1],
            rows[2],
            rows[3]
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return false;
        }
        memset(rows, 0, sizeof(rows));
        row_idx = 0;

        // Hash flags
        stellar_hashupdate_uint32(msg->clear_flags);
    }

    // Set flags
    stellar_hashupdate_bool(msg->has_set_flags);
    if (msg->has_set_flags) {
        strlcpy(str_title, _("Set Flag(s)"), sizeof(str_title));

        // Auth required
        if (msg->set_flags & 0x01) {
            strlcpy(rows[row_idx], _("AUTH_REQUIRED"), sizeof(rows[row_idx]));
            row_idx++;
        }
        // Auth revocable
        if (msg->set_flags & 0x02) {
            strlcpy(rows[row_idx], _("AUTH_REVOCABLE"), sizeof(rows[row_idx]));
            row_idx++;
        }

        stellar_layoutTransactionDialog(
            str_title,
            rows[0],
            rows[1],
            rows[2],
            rows[3]
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return false;
        }
        memset(rows, 0, sizeof(rows));
        row_idx = 0;

        // Hash flags
        stellar_hashupdate_uint32(msg->set_flags);
    }

    // Account thresholds
    bool show_thresholds_confirm = false;
    row_idx = 0;
    stellar_hashupdate_bool(msg->has_master_weight);
    if (msg->has_master_weight) {
        char str_master_weight[10+1];
        show_thresholds_confirm = true;
        stellar_format_uint32(msg->master_weight, str_master_weight, sizeof(str_master_weight));
        strlcpy(rows[row_idx], _("Master Weight: "), sizeof(rows[row_idx]));
        strlcat(rows[row_idx], str_master_weight, sizeof(rows[row_idx]));
        row_idx++;

        // Hash master weight
        stellar_hashupdate_uint32(msg->master_weight);
    }

    stellar_hashupdate_bool(msg->has_low_threshold);
    if (msg->has_low_threshold) {
        char str_low_threshold[10+1];
        show_thresholds_confirm = true;
        stellar_format_uint32(msg->low_threshold, str_low_threshold, sizeof(str_low_threshold));
        strlcpy(rows[row_idx], _("Low: "), sizeof(rows[row_idx]));
        strlcat(rows[row_idx], str_low_threshold, sizeof(rows[row_idx]));
        row_idx++;

        // Hash low threshold
        stellar_hashupdate_uint32(msg->low_threshold);
    }
    stellar_hashupdate_bool(msg->has_medium_threshold);
    if (msg->has_medium_threshold) {
        char str_med_threshold[10+1];
        show_thresholds_confirm = true;
        stellar_format_uint32(msg->medium_threshold, str_med_threshold, sizeof(str_med_threshold));
        strlcpy(rows[row_idx], _("Medium: "), sizeof(rows[row_idx]));
        strlcat(rows[row_idx], str_med_threshold, sizeof(rows[row_idx]));
        row_idx++;

        // Hash medium threshold
        stellar_hashupdate_uint32(msg->medium_threshold);
    }
    stellar_hashupdate_bool(msg->has_high_threshold);
    if (msg->has_high_threshold) {
        char str_high_threshold[10+1];
        show_thresholds_confirm = true;
        stellar_format_uint32(msg->high_threshold, str_high_threshold, sizeof(str_high_threshold));
        strlcpy(rows[row_idx], _("High: "), sizeof(rows[row_idx]));
        strlcat(rows[row_idx], str_high_threshold, sizeof(rows[row_idx]));
        row_idx++;

        // Hash high threshold
        stellar_hashupdate_uint32(msg->high_threshold);
    }

    if (show_thresholds_confirm) {
        strlcpy(str_title, _("Account Thresholds"), sizeof(str_title));
        stellar_layoutTransactionDialog(
            str_title,
            rows[0],
            rows[1],
            rows[2],
            rows[3]
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return false;
        }
        memset(rows, 0, sizeof(rows));
        row_idx = 0;
    }

    // Home domain
    stellar_hashupdate_bool(msg->has_home_domain);
    if (msg->has_home_domain) {
        strlcpy(str_title, _("Home Domain"), sizeof(str_title));

        // Split home domain if longer than 22 characters
        int home_domain_len = strnlen(msg->home_domain, 32);
        if (home_domain_len > 22) {
            strlcpy(rows[0], msg->home_domain, 22);
            strlcpy(rows[1], msg->home_domain + 21, sizeof(rows[1]));
        }
        else {
            strlcpy(rows[0], msg->home_domain, sizeof(rows[0]));
        }

        stellar_layoutTransactionDialog(
            str_title,
            rows[0],
            rows[1],
            NULL,
            NULL
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return false;
        }
        memset(rows, 0, sizeof(rows));
        row_idx = 0;

        stellar_hashupdate_string((unsigned char*)&(msg->home_domain), strnlen(msg->home_domain, 32));
    }

    // Signer
    stellar_hashupdate_bool(msg->has_signer_type);
    if (msg->has_signer_type) {
        if (msg->signer_weight > 0) {
            strlcpy(str_title, _("Add Signer: "), sizeof(str_title));
        }
        else {
            strlcpy(str_title, _("REMOVE Signer: "), sizeof(str_title));
        }

        // Format weight as a string
        char str_weight[16];
        stellar_format_uint32(msg->signer_weight, str_weight, sizeof(str_weight));
        char str_weight_row[32];
        strlcpy(str_weight_row, _("Weight: "), sizeof(str_weight_row));
        strlcat(str_weight_row, str_weight, sizeof(str_weight_row));

        // 0 = account, 1 = pre-auth, 2 = hash(x)
        char str_signer_type[16];
        bool needs_hash_confirm = false;
        if (msg->signer_type == 0) {
            strlcpy(str_signer_type, _("account"), sizeof(str_signer_type));
            strlcat(str_title, str_signer_type, sizeof(str_title));

            const char **str_addr_rows = stellar_lineBreakAddress(msg->signer_key.bytes);
            stellar_layoutTransactionDialog(
                str_title,
                str_weight_row,
                str_addr_rows[0],
                str_addr_rows[1],
                str_addr_rows[2]
            );
            if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
                stellar_signingAbort(_("User canceled"));
                return false;
            }
        }
        if (msg->signer_type == 1) {
            needs_hash_confirm = true;
            strlcpy(str_signer_type, _("pre-auth hash"), sizeof(str_signer_type));
            strlcat(str_title, str_signer_type, sizeof(str_title));

            stellar_layoutTransactionDialog(
                str_title,
                str_weight_row,
                NULL,
                _("(confirm hash on next"),
                _("screen)")
            );
            if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
                stellar_signingAbort(_("User canceled"));
                return false;
            }
        }
        if (msg->signer_type == 2) {
            needs_hash_confirm = true;
            strlcpy(str_signer_type, _("hash(x)"), sizeof(str_signer_type));
            strlcat(str_title, str_signer_type, sizeof(str_title));

            stellar_layoutTransactionDialog(
                str_title,
                str_weight_row,
                NULL,
                _("(confirm hash on next"),
                _("screen)")
            );
            if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
                stellar_signingAbort(_("User canceled"));
                return false;
            }
        }

        // Extra confirmation step for hash signers
        if (needs_hash_confirm) {
            data2hex(msg->signer_key.bytes +  0, 8, rows[row_idx++]);
            data2hex(msg->signer_key.bytes +  8, 8, rows[row_idx++]);
            data2hex(msg->signer_key.bytes + 16, 8, rows[row_idx++]);
            data2hex(msg->signer_key.bytes + 24, 8, rows[row_idx++]);

            stellar_layoutTransactionDialog(
                _("Confirm Hash"),
                rows[0],
                rows[1],
                rows[2],
                rows[3]
            );
            if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
                stellar_signingAbort(_("User canceled"));
                return false;
            }
            memset(rows, 0, sizeof(rows));
            row_idx = 0;
        }

        // Hash: signer type
        stellar_hashupdate_uint32(msg->signer_type);
        // key
        stellar_hashupdate_bytes(msg->signer_key.bytes, msg->signer_key.size);
        // weight
        stellar_hashupdate_uint32(msg->signer_weight);
    }

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmChangeTrustOp(StellarChangeTrustOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(6);

    // Add Trust: USD
    char str_title[32];
    if (msg->limit == 0) {
        strlcpy(str_title, _("DELETE Trust: "), sizeof(str_title));
    }
    else {
        strlcpy(str_title, _("Add Trust: "), sizeof(str_title));
    }
    strlcat(str_title, msg->asset.code, sizeof(str_title));

    // Amount: MAX (or a number)
    char str_amount_row[32];
    strlcpy(str_amount_row, _("Amount: "), sizeof(str_amount_row));

    if (msg->limit == 9223372036854775807) {
        strlcat(str_amount_row, _("[Maximum]"), sizeof(str_amount_row));
    }
    else {
        char str_amount[32];
        stellar_format_stroops(msg->limit, str_amount, sizeof(str_amount));
        strlcat(str_amount_row, str_amount, sizeof(str_amount_row));
    }

    // Validate destination account and convert to bytes
    uint8_t asset_issuer_bytes[STELLAR_KEY_SIZE];
    if (!stellar_getAddressBytes(msg->asset.issuer, asset_issuer_bytes)) {
        stellar_signingAbort(_("User canceled"));
        fsm_sendFailure(Failure_FailureType_Failure_ProcessError, _("Invalid asset issuer"));
        return false;
    }

    // Display full issuer address
    const char **str_addr_rows = stellar_lineBreakAddress(asset_issuer_bytes);

    stellar_layoutTransactionDialog(
        str_title,
        str_amount_row,
        str_addr_rows[0],
        str_addr_rows[1],
        str_addr_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash: asset
    stellar_hashupdate_asset(&(msg->asset));
    // limit
    stellar_hashupdate_uint64(msg->limit);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmAllowTrustOp(StellarAllowTrustOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(7);

    // Add Trust: USD
    char str_title[32];
    if (msg->is_authorized) {
        strlcpy(str_title, _("Allow Trust of"), sizeof(str_title));
    }
    else {
        strlcpy(str_title, _("REVOKE Trust of"), sizeof(str_title));
    }

    // Asset code
    char str_asset_row[32];
    strlcpy(str_asset_row, msg->asset_code, sizeof(str_asset_row));

    // Validate account and convert to bytes
    uint8_t trusted_account_bytes[STELLAR_KEY_SIZE];
    if (!stellar_getAddressBytes(msg->trusted_account, trusted_account_bytes)) {
        stellar_signingAbort(_("Invalid trusted account"));
        return false;
    }

    const char **str_trustor_rows = stellar_lineBreakAddress(trusted_account_bytes);

    // By: G...
    char str_by[32];
    strlcpy(str_by, _("By: "), sizeof(str_by));
    strlcat(str_by, str_trustor_rows[0], sizeof(str_by));

    stellar_layoutTransactionDialog(
        str_title,
        str_asset_row,
        str_by,
        str_trustor_rows[1],
        str_trustor_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash: trustor account (the account being allowed to access the asset)
    stellar_hashupdate_address(trusted_account_bytes);
    // asset type
    stellar_hashupdate_uint32(msg->asset_type);
    // asset code
    if (msg->asset_type == 1) {
        char code4[4+1];
        memset(code4, 0, sizeof(code4));
        strlcpy(code4, msg->asset_code, sizeof(code4));
        stellar_hashupdate_bytes((uint8_t *)code4, 4);
    }
    if (msg->asset_type == 2) {
        char code12[12+1];
        memset(code12, 0, sizeof(code12));
        strlcpy(code12, msg->asset_code, sizeof(code12));
        stellar_hashupdate_bytes((uint8_t *)code12, 12);
    }
    // is authorized
    stellar_hashupdate_bool(msg->is_authorized);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmAccountMergeOp(StellarAccountMergeOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(8);

    // Validate account and convert to bytes
    uint8_t destination_account_bytes[STELLAR_KEY_SIZE];
    if (!stellar_getAddressBytes(msg->destination_account, destination_account_bytes)) {
        stellar_signingAbort(_("Invalid destination account"));
        return false;
    }

    const char **str_destination_rows = stellar_lineBreakAddress(destination_account_bytes);

    stellar_layoutTransactionDialog(
        _("Merge Account"),
        _("All XLM will be sent to:"),
        str_destination_rows[0],
        str_destination_rows[1],
        str_destination_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash: destination account
    stellar_hashupdate_address(destination_account_bytes);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmManageDataOp(StellarManageDataOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(10);

    char str_title[32];
    if (msg->has_value) {
        strlcpy(str_title, _("Set data value key:"), sizeof(str_title));
    }
    else {
        strlcpy(str_title, _("CLEAR data value key:"), sizeof(str_title));
    }

    // Confirm key
    const char **str_key_lines = split_message((const uint8_t*)(msg->key), strnlen(msg->key, 64), 16);

    stellar_layoutTransactionDialog(
        str_title,
        str_key_lines[0],
        str_key_lines[1],
        str_key_lines[2],
        str_key_lines[3]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Confirm value by displaying sha256 hash since this can contain non-printable characters
    if (msg->has_value) {
        strlcpy(str_title, _("Confirm sha256 of value:"), sizeof(str_title));

        char str_hash_digest[SHA256_DIGEST_STRING_LENGTH];
        sha256_Data(msg->value.bytes, msg->value.size, str_hash_digest);
        const char **str_hash_lines = split_message((const uint8_t*)str_hash_digest, sizeof(str_hash_digest), 16);

        stellar_layoutTransactionDialog(
            str_title,
            str_hash_lines[0],
            str_hash_lines[1],
            str_hash_lines[2],
            str_hash_lines[3]
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return false;
        }
    }

    // Hash: key
    stellar_hashupdate_string((unsigned char*)&(msg->key), strnlen(msg->key, 64));
    // value
    if (msg->has_value) {
        stellar_hashupdate_bool(true);
        // Variable opaque field is length + raw bytes
        stellar_hashupdate_uint32(msg->value.size);
        stellar_hashupdate_bytes(msg->value.bytes, msg->value.size);
    }
    else {
        stellar_hashupdate_bool(false);
    }

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

bool stellar_confirmBumpSequenceOp(StellarBumpSequenceOp *msg)
{
    if (!stellar_signing) return false;

    if (!stellar_confirmSourceAccount(msg->has_source_account, msg->source_account)) {
        stellar_signingAbort(_("Source account error"));
        return false;
    }

    // Hash: operation type
    stellar_hashupdate_uint32(11);

    char str_bump_to[20];
    stellar_format_uint64(msg->bump_to, str_bump_to, sizeof(str_bump_to));

    stellar_layoutTransactionDialog(
        _("Bump Sequence"),
        _("Set sequence to:"),
        str_bump_to,
        NULL,
        NULL
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return false;
    }

    // Hash: bump to
    stellar_hashupdate_uint64(msg->bump_to);

    // At this point, the operation is confirmed
    stellar_activeTx.confirmed_operations++;
    return true;
}

void stellar_signingAbort(const char *reason)
{
    if (!reason) {
        reason = _("Unknown error");
    }

    stellar_signing = false;
    fsm_sendFailure(Failure_FailureType_Failure_ProcessError, reason);
    layoutHome();
}

/**
 * Populates the fields of resp with the signature of the active transaction
 */
void stellar_fillSignedTx(StellarSignedTx *resp)
{
    // Finalize the transaction by hashing 4 null bytes representing a (currently unused) empty union
    stellar_hashupdate_uint32(0);

    // Add the public key for verification that the right account was used for signing
    memcpy(resp->public_key.bytes, stellar_activeTx.signing_pubkey, 32);
    resp->public_key.size = 32;
    resp->has_public_key = true;

    // Add the signature (note that this does not include the 4-byte hint since it can be calculated from the public key)
    uint8_t signature[64];
    // Note: this calls sha256_Final on the hash context
    stellar_getSignatureForActiveTx(signature);
    memcpy(resp->signature.bytes, signature, sizeof(signature));
    resp->signature.size = sizeof(signature);
    resp->has_signature = true;
}

bool stellar_allOperationsConfirmed()
{
    return stellar_activeTx.confirmed_operations == stellar_activeTx.num_operations;
}

/*
 * Calculates and sets the signature for the active transaction
 */
void stellar_getSignatureForActiveTx(uint8_t *out_signature)
{
    HDNode *node = stellar_deriveNode(stellar_activeTx.address_n, stellar_activeTx.address_n_count);

    // Signature is the ed25519 detached signature of the sha256 of all the bytes
    // that have been read so far
    uint8_t to_sign[32];
    sha256_Final(&(stellar_activeTx.sha256_ctx), to_sign);

    uint8_t signature[64];
    ed25519_sign(to_sign, sizeof(to_sign), node->private_key, node->public_key + 1, signature);

    memcpy(out_signature, signature, sizeof(signature));
}

/*
 * Returns number (representing stroops) formatted as XLM
 * For example, if number has value 1000000000 then it will be returned as "100.0"
 */
void stellar_format_stroops(uint64_t number, char *out, size_t outlen)
{
    bn_format_uint64(number, NULL, NULL, 7, 0, false, out, outlen);
}

/*
 * Formats a price represented as a uint32 numerator and uint32 denominator
 *
 * Note that there may be a loss of precision between the real price value and what
 * is shown to the user
 *
 * Smallest possible price is 1 / 4294967296 which is:
 *  0.00000000023283064365386962890625
 *
 * largest possible price is:
 *  4294967296
 */
void stellar_format_price(uint32_t numerator, uint32_t denominator, char *out, size_t outlen)
{
    memset(out, 0, outlen);

    // early exist for invalid denominator
    if (denominator == 0) {
        strlcpy(out, _("[Invalid Price]"), outlen);
        return;
    }

    int scale = 0;
    double dbl_value = (double)numerator / (double)denominator;

    // Multiply by 10 until the value is larger than the largest possible offer size
    // Largest possible offer size is UINT32_MAX (4294967296)
    while (dbl_value < UINT32_MAX) {
        dbl_value *= (double)10;
        scale++;
    }

    // Cast back to an integer
    uint64_t scaled_value = (uint64_t) dbl_value;

    // Format with bn_format_uint64
    bn_format_uint64(scaled_value, NULL, NULL, scale, 0, false, out, outlen);
}

/*
 * Returns a uint32 formatted as a string
 */
void stellar_format_uint32(uint32_t number, char *out, size_t outlen)
{
    bignum256 bn_number;
    bn_read_uint32(number, &bn_number);
    bn_format(&bn_number, NULL, NULL, 0, 0, false, out, outlen);
}

/*
 * Returns a uint64 formatted as a string
 */
void stellar_format_uint64(uint64_t number, char *out, size_t outlen)
{
    bn_format_uint64(number, NULL, NULL, 0, 0, false, out, outlen);
}

/*
 * Breaks a 56 character address into 3 lines of lengths 16, 20, 20
 * This is to allow a small label to be prepended to the first line
 */
const char **stellar_lineBreakAddress(uint8_t *addrbytes)
{
    char str_fulladdr[56+1];
    static char rows[3][20+1];

    memset(rows, 0, sizeof(rows));

    // get full address string
    stellar_publicAddressAsStr(addrbytes, str_fulladdr, sizeof(str_fulladdr));

    // Break it into 3 lines
    strlcpy(rows[0], str_fulladdr + 0, 17);
    strlcpy(rows[1], str_fulladdr + 16, 21);
    strlcpy(rows[2], str_fulladdr + 16 + 20, 21);

    static const char *ret[3] = { rows[0], rows[1], rows[2] };
    return ret;
}

/*
 * Returns the asset formatted to fit in a single row
 *
 * Examples:
 *  XLM (Native Asset)
 *  MOBI (G123456789000)
 *  ALPHA12EXAMP (G0987)
 */
void stellar_format_asset(StellarAssetType *asset, char *str_formatted, size_t len)
{
    char str_asset_code[12 + 1];
    // truncated asset issuer, final length depends on length of asset code
    char str_asset_issuer_trunc[13 + 1];

    memset(str_formatted, 0, len);
    memset(str_asset_code, 0, sizeof(str_asset_code));
    memset(str_asset_issuer_trunc, 0, sizeof(str_asset_issuer_trunc));

    // Validate issuer account for non-native assets
    if (asset->type != 0 && !stellar_validateAddress(asset->issuer)) {
        stellar_signingAbort(_("Invalid asset issuer"));
        return;
    }

    // Native asset
    if (asset->type == 0) {
        strlcpy(str_formatted, _("XLM (native asset)"), len);
    }
    // 4-character custom
    if (asset->type == 1) {
        memcpy(str_asset_code, asset->code, 4);
        strlcpy(str_formatted, str_asset_code, len);

        // Truncate issuer to 13 chars
        memcpy(str_asset_issuer_trunc, asset->issuer, 13);
    }
    // 12-character custom
    if (asset->type == 2) {
        memcpy(str_asset_code, asset->code, 12);
        strlcpy(str_formatted, str_asset_code, len);

        // Truncate issuer to 5 characters
        memcpy(str_asset_issuer_trunc, asset->issuer, 5);
    }
    // Issuer is read the same way for both types of custom assets
    if (asset->type == 1 || asset->type == 2) {
        strlcat(str_formatted, _(" ("), len);
        strlcat(str_formatted, str_asset_issuer_trunc, len);
        strlcat(str_formatted, _(")"), len);
    }
}

size_t stellar_publicAddressAsStr(uint8_t *bytes, char *out, size_t outlen)
{
    // version + key bytes + checksum
    uint8_t keylen = 1 + 32 + 2;
    uint8_t bytes_full[keylen];
    bytes_full[0] = 6 << 3; // 'G'

    memcpy(bytes_full + 1, bytes, 32);

    // Last two bytes are the checksum
    uint16_t checksum = stellar_crc16(bytes_full, 33);
    bytes_full[keylen-2] = checksum & 0x00ff;
    bytes_full[keylen-1] = (checksum>>8) & 0x00ff;

    base32_encode(bytes_full, keylen, out, outlen, BASE32_ALPHABET_RFC4648);

    // Public key will always be 56 characters
    return 56;
}

/**
 * Stellar account string is a base32-encoded string that starts with "G"
 *
 * It decodes to the following format:
 *  Byte 0 - always 0x30 ("G" when base32 encoded), version byte indicating a public key
 *  Bytes 1-33 - 32-byte public key bytes
 *  Bytes 34-35 - 2-byte CRC16 checksum of the version byte + public key bytes (first 33 bytes)
 *
 * Note that the stellar "seed" (private key) also uses this format except the version byte
 * is 0xC0 which encodes to "S" in base32
 */
bool stellar_validateAddress(const char *str_address)
{
    bool valid = false;
    uint8_t decoded[STELLAR_ADDRESS_SIZE_RAW];

    if (strlen(str_address) != STELLAR_ADDRESS_SIZE) {
        return false;
    }

    // Check that it decodes correctly
    uint8_t *ret = base32_decode(str_address, STELLAR_ADDRESS_SIZE, decoded, sizeof(decoded), BASE32_ALPHABET_RFC4648);
    valid = (ret != NULL);

    // ... and that version byte is 0x30
    if (valid && decoded[0] != 0x30) {
        valid = false;
    }

    // ... and that checksums match
    uint16_t checksum_expected = stellar_crc16(decoded, 33);
    uint16_t checksum_actual = (decoded[34] << 8) | decoded[33]; // unsigned short (little endian)
    if (valid && checksum_expected != checksum_actual) {
        valid = false;
    }

    memzero(decoded, sizeof(decoded));
    return valid;
}

/**
 * Converts a string address (G...) to the 32-byte raw address
 */
bool stellar_getAddressBytes(char* str_address, uint8_t *out_bytes)
{
    uint8_t decoded[STELLAR_ADDRESS_SIZE_RAW];

    // Ensure address is valid
    if (!stellar_validateAddress(str_address)) return false;

    base32_decode(str_address, STELLAR_ADDRESS_SIZE, decoded, sizeof(decoded), BASE32_ALPHABET_RFC4648);

    // The 32 bytes with offset 1-33 represent the public key
    memcpy(out_bytes, &decoded[1], 32);

    memzero(decoded, sizeof(decoded));
    return true;
}

/*
 * CRC16 implementation compatible with the Stellar version
 * Ported from this implementation: http://introcs.cs.princeton.edu/java/61data/CRC16CCITT.java.html
 * Initial value changed to 0x0000 to match Stellar
 */
uint16_t stellar_crc16(uint8_t *bytes, uint32_t length)
{
    // Calculate checksum for existing bytes
    uint16_t crc = 0x0000;
    uint16_t polynomial = 0x1021;
    uint32_t i;
    uint8_t bit;
    uint8_t byte;
    uint8_t bitidx;
    uint8_t c15;

    for (i=0; i < length; i++) {
        byte = bytes[i];
        for (bitidx=0; bitidx < 8; bitidx++) {
            bit = ((byte >> (7 - bitidx) & 1) == 1);
            c15 = ((crc >> 15 & 1) == 1);
            crc <<= 1;
            if (c15 ^ bit) crc ^= polynomial;
        }
    }

    return crc & 0xffff;
}

/*
 * Derives the HDNode at the given index
 * Standard Stellar prefix is m/44'/148'/ and the default account is m/44'/148'/0'
 *
 * All paths must be hardened
 */
HDNode *stellar_deriveNode(uint32_t *address_n, size_t address_n_count)
{
    static CONFIDENTIAL HDNode node;
    const char *curve = "ed25519";

    // Device not initialized, passphrase request cancelled, or unsupported curve
    if (!storage_getRootNode(&node, curve, true)) {
        return 0;
    }
    // Failed to derive private key
    if (hdnode_private_ckd_cached(&node, address_n, address_n_count, NULL) == 0) {
        return 0;
    }

    hdnode_fill_public_key(&node);

    return &node;
}

void stellar_hashupdate_uint32(uint32_t value)
{
    // Ensure uint32 is big endian
#if BYTE_ORDER == LITTLE_ENDIAN
    REVERSE32(value, value);
#endif

    // Byte values must be hashed as big endian
    uint8_t data[4];
    data[3] = (value >> 24) & 0xFF;
    data[2] = (value >> 16) & 0xFF;
    data[1] = (value >> 8)  & 0xFF;
    data[0] = value         & 0xFF;

    stellar_hashupdate_bytes(data, sizeof(data));
}

void stellar_hashupdate_uint64(uint64_t value)
{
    // Ensure uint64 is big endian
#if BYTE_ORDER == LITTLE_ENDIAN
    REVERSE64(value, value);
#endif

    // Byte values must be hashed as big endian
    uint8_t data[8];
    data[7] = (value >> 56) & 0xFF;
    data[6] = (value >> 48) & 0xFF;
    data[5] = (value >> 40) & 0xFF;
    data[4] = (value >> 32) & 0xFF;
    data[3] = (value >> 24) & 0xFF;
    data[2] = (value >> 16) & 0xFF;
    data[1] = (value >> 8)  & 0xFF;
    data[0] = value         & 0xFF;

    stellar_hashupdate_bytes(data, sizeof(data));
}

void stellar_hashupdate_bool(bool value)
{
    if (value) {
        stellar_hashupdate_uint32(1);
    }
    else {
        stellar_hashupdate_uint32(0);
    }
}

void stellar_hashupdate_string(uint8_t *data, size_t len)
{
    // Hash the length of the string
    stellar_hashupdate_uint32((uint32_t)len);

    // Hash the raw bytes of the string
    stellar_hashupdate_bytes(data, len);

    // If len isn't a multiple of 4, add padding bytes
    int remainder = len % 4;
    uint8_t null_byte[1] = { 0x00 };
    if (remainder) {
        while (remainder < 4) {
            stellar_hashupdate_bytes(null_byte, 1);
            remainder++;
        }
    }
}

void stellar_hashupdate_address(uint8_t *address_bytes)
{
    // First 4 bytes of an address are the type. There's only one type (0)
    stellar_hashupdate_uint32(0);

    // Remaining part of the address is 32 bytes
    stellar_hashupdate_bytes(address_bytes, 32);
}

/*
 * Note about string handling below: this field is an XDR "opaque" field and not a typical string,
 * so if "TEST" is the asset code then the hashed value needs to be 4 bytes and not include the null
 * at the end of the string
 */
void stellar_hashupdate_asset(StellarAssetType *asset)
{
    stellar_hashupdate_uint32(asset->type);

    // For non-native assets, validate issuer account and convert to bytes
    uint8_t issuer_bytes[STELLAR_KEY_SIZE];
    if (asset->type != 0 && !stellar_getAddressBytes(asset->issuer, issuer_bytes)) {
        stellar_signingAbort(_("Invalid asset issuer"));
        return;
    }

    // 4-character asset code
    if (asset->type == 1) {
        char code4[4+1];
        memset(code4, 0, sizeof(code4));
        strlcpy(code4, asset->code, sizeof(code4));

        stellar_hashupdate_bytes((uint8_t *)code4, 4);
        stellar_hashupdate_address(issuer_bytes);
    }

    // 12-character asset code
    if (asset->type == 2) {
        char code12[12+1];
        memset(code12, 0, sizeof(code12));
        strlcpy(code12, asset->code, sizeof(code12));

        stellar_hashupdate_bytes((uint8_t *)code12, 12);
        stellar_hashupdate_address(issuer_bytes);
    }
}

void stellar_hashupdate_bytes(uint8_t *data, size_t len)
{
    sha256_Update(&(stellar_activeTx.sha256_ctx), data, len);
}

/*
 * Displays a summary of the overall transaction
 */
void stellar_layoutTransactionSummary(StellarSignTx *msg)
{
    char str_lines[5][32];
    memset(str_lines, 0, sizeof(str_lines));

    char str_fee[12];
    char str_num_ops[12];

    // Will be set to true for some large hashes that don't fit on one screen
    uint8_t needs_memo_hash_confirm = 0;

    // Format the fee
    stellar_format_stroops(msg->fee, str_fee, sizeof(str_fee));

    strlcpy(str_lines[0], _("Fee: "), sizeof(str_lines[0]));
    strlcat(str_lines[0], str_fee, sizeof(str_lines[0]));
    strlcat(str_lines[0], _(" XLM"), sizeof(str_lines[0]));

    // add in numOperations
    stellar_format_uint32(msg->num_operations, str_num_ops, sizeof(str_num_ops));

    strlcat(str_lines[0], _(" ("), sizeof(str_lines[0]));
    strlcat(str_lines[0], str_num_ops, sizeof(str_lines[0]));
    if (msg->num_operations == 1) {
        strlcat(str_lines[0], _(" op)"), sizeof(str_lines[0]));
    } else {
        strlcat(str_lines[0], _(" ops)"), sizeof(str_lines[0]));
    }

    // Display full address being used to sign transaction
    const char **str_addr_rows = stellar_lineBreakAddress(stellar_activeTx.signing_pubkey);

    stellar_layoutTransactionDialog(
        str_lines[0],
        _("Signing with:"),
        str_addr_rows[0],
        str_addr_rows[1],
        str_addr_rows[2]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return;
    }

    // Reset lines for displaying memo
    memset(str_lines, 0, sizeof(str_lines));

    // Memo: none
    if (msg->memo_type == 0) {
        strlcpy(str_lines[0], _("[No Memo Set]"), sizeof(str_lines[0]));
        strlcpy(str_lines[1], _("Important:"), sizeof(str_lines[0]));
        strlcpy(str_lines[2], _("Many exchanges require"), sizeof(str_lines[0]));
        strlcpy(str_lines[3], _("a memo when depositing."), sizeof(str_lines[0]));
    }
    // Memo: text
    if (msg->memo_type == 1) {
        strlcpy(str_lines[0], _("Memo (TEXT)"), sizeof(str_lines[0]));

        // Split 28-character string into two lines of 19 / 9
        // todo: word wrap method?
        strlcpy(str_lines[1], (const char*)msg->memo_text, 19 + 1);
        strlcpy(str_lines[2], (const char*)(msg->memo_text + 19), 9 + 1);
    }
    // Memo: ID
    if (msg->memo_type == 2) {
        strlcpy(str_lines[0], _("Memo (ID)"), sizeof(str_lines[0]));
        stellar_format_uint64(msg->memo_id, str_lines[1], sizeof(str_lines[1]));
    }
    // Memo: hash
    if (msg->memo_type == 3) {
        needs_memo_hash_confirm = 1;
        strlcpy(str_lines[0], _("Memo (HASH)"), sizeof(str_lines[0]));
    }
    // Memo: return
    if (msg->memo_type == 4) {
        needs_memo_hash_confirm = 1;
        strlcpy(str_lines[0], _("Memo (RETURN)"), sizeof(str_lines[0]));
    }

    if (needs_memo_hash_confirm) {
        data2hex(msg->memo_hash.bytes +  0, 8, str_lines[1]);
        data2hex(msg->memo_hash.bytes +  8, 8, str_lines[2]);
        data2hex(msg->memo_hash.bytes + 16, 8, str_lines[3]);
        data2hex(msg->memo_hash.bytes + 24, 8, str_lines[4]);
    }

    stellar_layoutTransactionDialog(
        str_lines[0],
        str_lines[1],
        str_lines[2],
        str_lines[3],
        str_lines[4]
    );
    if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
        stellar_signingAbort(_("User canceled"));
        return;
    }

    // Verify timebounds, if present
    memset(str_lines, 0, sizeof(str_lines));

    // Timebound: lower
    if (msg->timebounds_start || msg->timebounds_end) {
        time_t timebound;
        char str_timebound[32];
        const struct tm *tm;

        timebound = (time_t)msg->timebounds_start;
        strlcpy(str_lines[0], _("Valid from:"), sizeof(str_lines[0]));
        if (timebound) {
            tm = gmtime(&timebound);
            strftime(str_timebound, sizeof(str_timebound), "%F %T (UTC)", tm);
            strlcpy(str_lines[1], str_timebound, sizeof(str_lines[1]));
        }
        else {
            strlcpy(str_lines[1], _("[no restriction]"), sizeof(str_lines[1]));
        }

        // Reset for timebound_max
        memset(str_timebound, 0, sizeof(str_timebound));

        timebound = (time_t)msg->timebounds_end;
        strlcpy(str_lines[0], _("Valid from:"), sizeof(str_lines[0]));
        if (timebound) {
            tm = gmtime(&timebound);
            strftime(str_timebound, sizeof(str_timebound), "%F %T (UTC)", tm);
            strlcpy(str_lines[1], str_timebound, sizeof(str_lines[1]));
        }
        else {
            strlcpy(str_lines[1], _("[no restriction]"), sizeof(str_lines[1]));
        }
    }

    if (msg->timebounds_start || msg->timebounds_end) {
        stellar_layoutTransactionDialog(
            _("Confirm Time Bounds"),
            str_lines[0],
            str_lines[1],
            str_lines[2],
            str_lines[3]
        );
        if (!protectButton(ButtonRequest_ButtonRequestType_ButtonRequest_ProtectCall, false)) {
            stellar_signingAbort(_("User canceled"));
            return;
        }
    }
}

/*
 * Most basic dialog used for signing
 *  - Header indicating which key is being used for signing
 *  - 5 rows for content
 *  - Cancel / Next buttons
 *  - Warning message can appear between cancel/next buttons
 */
void stellar_layoutSigningDialog(const char *line1, const char *line2, const char *line3, const char *line4, const char *line5, uint32_t *address_n, size_t address_n_count, const char *warning, bool is_final_step)
{
    // Start with some initial padding and use these to track position as rendering moves down the screen
    int offset_x = 1;
    int offset_y = 1;
    int line_height = 9;

    HDNode *node = stellar_deriveNode(address_n, address_n_count);
    if (!node) {
        // TODO: bail on error
        return;
    }

    char str_pubaddr_truncated[12]; // G???? + null
    memset(str_pubaddr_truncated, 0, sizeof(str_pubaddr_truncated));

    layoutLast = layoutDialogSwipe;
    layoutSwipe();
    oledClear();

    // Load up public address
    char str_pubaddr[56+1];
    memset(str_pubaddr, 0, sizeof(str_pubaddr));
    stellar_publicAddressAsStr(node->public_key + 1, str_pubaddr, sizeof(str_pubaddr));
    memcpy(str_pubaddr_truncated, str_pubaddr, sizeof(str_pubaddr_truncated) - 1);

    // Header
    // Ends up as: Signing with GABCDEFGHIJKL
    char str_header[32];
    memset(str_header, 0, sizeof(str_header));
    strlcpy(str_header, _("Signing with "), sizeof(str_header));
    strlcat(str_header, str_pubaddr_truncated, sizeof(str_header));

    oledDrawString(offset_x, offset_y, str_header, FONT_STANDARD);
    offset_y += line_height;
    // Invert color on header
    oledInvert(0, 0, OLED_WIDTH, offset_y - 2);

    // Dialog contents begin
    if (line1) {
        oledDrawString(offset_x, offset_y, line1, FONT_STANDARD);
    }
    offset_y += line_height;
    if (line2) {
        oledDrawString(offset_x, offset_y, line2, FONT_STANDARD);
    }
    offset_y += line_height;
    if (line3) {
        oledDrawString(offset_x, offset_y, line3, FONT_STANDARD);
    }
    offset_y += line_height;
    if (line4) {
        oledDrawString(offset_x, offset_y, line4, FONT_STANDARD);
    }
    offset_y += line_height;
    if (line5) {
        oledDrawString(offset_x, offset_y, line5, FONT_STANDARD);
    }
    offset_y += line_height;

    // Cancel button
    oledDrawString(1, OLED_HEIGHT - 8, "\x15", FONT_STANDARD);
    oledDrawString(fontCharWidth(FONT_STANDARD, '\x15') + 3, OLED_HEIGHT - 8, "Cancel", FONT_STANDARD);
    oledInvert(0, OLED_HEIGHT - 9, fontCharWidth(FONT_STANDARD, '\x15') + oledStringWidth("Cancel", FONT_STANDARD) + 2, OLED_HEIGHT - 1);

    // Warnings (drawn centered between the buttons
    if (warning) {
        oledDrawStringCenter(OLED_HEIGHT - 8, warning, FONT_STANDARD);
    }

    // Next / sign button
    char str_next_label[8];
    if (is_final_step) {
        strlcpy(str_next_label, _("SIGN"), sizeof(str_next_label));
    }
    else {
        strlcpy(str_next_label, _("Next"), sizeof(str_next_label));
    }

    oledDrawString(OLED_WIDTH - fontCharWidth(FONT_STANDARD, '\x06') - 1, OLED_HEIGHT - 8, "\x06", FONT_STANDARD);
    oledDrawString(OLED_WIDTH - oledStringWidth(str_next_label, FONT_STANDARD) - fontCharWidth(FONT_STANDARD, '\x06') - 3, OLED_HEIGHT - 8, str_next_label, FONT_STANDARD);
    oledInvert(OLED_WIDTH - oledStringWidth(str_next_label, FONT_STANDARD) - fontCharWidth(FONT_STANDARD, '\x06') - 4, OLED_HEIGHT - 9, OLED_WIDTH - 1, OLED_HEIGHT - 1);

    oledRefresh();
}

/*
 * Main dialog helper method. Allows displaying 5 lines.
 * A title showing the account being used to sign is always displayed.
 */
void stellar_layoutTransactionDialog(const char *line1, const char *line2, const char *line3, const char *line4, const char *line5)
{
    char str_warning[16];
    memset(str_warning, 0, sizeof(str_warning));

    if (stellar_activeTx.network_type == 2) {
        // Warning: testnet
        strlcpy(str_warning, _("WRN:TN"), sizeof(str_warning));
    }
    if (stellar_activeTx.network_type == 3) {
        // Warning: private network
        strlcpy(str_warning, _("WRN:PN"), sizeof(str_warning));
    }

    stellar_layoutSigningDialog(
        line1,
        line2,
        line3,
        line4,
        line5,
        stellar_activeTx.address_n,
        stellar_activeTx.address_n_count,
        str_warning,
        false
    );
}