## Mu's instructions and their table-driven translation

See http://akkartik.name/akkartik-convivial-20200607.pdf for the complete
story. In brief: Mu is a statement-oriented language. Blocks consist of flat
lists of instructions. Instructions can have inputs after the operation, and
outputs to the left of a '<-'. Inputs and outputs must be variables. They can't
include nested expressions. Variables can be literals ('n'), or live in a
register ('var/reg') or in memory ('var') at some 'stack-offset' from the 'ebp'
register. Outputs must be registers. To modify a variable in memory, pass it in
by reference as an input. (Inputs are more precisely called 'inouts'.)
Conversely, registers that are just read from must not be passed as inputs.

The following chart shows all the instruction forms supported by Mu, along with
the SubX instruction they're translated to.

## Integer instructions

These instructions use the general-purpose registers.

var/eax <- increment              => "40/increment-eax"
var/ecx <- increment              => "41/increment-ecx"
var/edx <- increment              => "42/increment-edx"
var/ebx <- increment              => "43/increment-ebx"
var/esi <- increment              => "46/increment-esi"
var/edi <- increment              => "47/increment-edi"
increment var                     => "ff 0/subop/increment *(ebp+" var.stack-offset ")"
increment *var/reg                => "ff 0/subop/increment *" reg

var/eax <- decrement              => "48/decrement-eax"
var/ecx <- decrement              => "49/decrement-ecx"
var/edx <- decrement              => "4a/decrement-edx"
var/ebx <- decrement              => "4b/decrement-ebx"
var/esi <- decrement              => "4e/decrement-esi"
var/edi <- decrement              => "4f/decrement-edi"
decrement var                     => "ff 1/subop/decrement *(ebp+" var.stack-offset ")"
decrement *var/reg                => "ff 1/subop/decrement *" reg

var/reg <- add var2/reg2          => "01/add-to %" reg " " reg2 "/r32"
var/reg <- add var2               => "03/add *(ebp+" var2.stack-offset ") " reg "/r32"
var/reg <- add *var2/reg2         => "03/add *" reg2 " " reg "/r32"
add-to var1, var2/reg             => "01/add-to *(ebp+" var1.stack-offset ") " reg "/r32"
add-to *var1/reg1, var2/reg2      => "01/add-to *" reg1 " " reg2 "/r32"
var/eax <- add n                  => "05/add-to-eax " n "/imm32"
var/reg <- add n                  => "81 0/subop/add %" reg " " n "/imm32"
add-to var, n                     => "81 0/subop/add *(ebp+" var.stack-offset ") " n "/imm32"
add-to *var/reg, n                => "81 0/subop/add *" reg " " n "/imm32"

var/reg <- subtract var2/reg2     => "29/subtract-from %" reg " " reg2 "/r32"
var/reg <- subtract var2          => "2b/subtract *(ebp+" var2.stack-offset ") " reg "/r32"
var/reg <- subtract *var2/reg2    => "2b/subtract *" reg2 "
/*
 * otr.c
 *
 * Copyright (C) 2012 - 2014 James Booth <boothj5@gmail.com>
 *
 * This file is part of Profanity.
 *
 * Profanity is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Profanity 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Profanity.  If not, see <http://www.gnu.org/licenses/>.
 *
 * In addition, as a special exception, the copyright holders give permission to
 * link the code of portions of this program with the OpenSSL library under
 * certain conditions as described in each individual source file, and
 * distribute linked combinations including the two.
 *
 * You must obey the GNU General Public License in all respects for all of the
 * code used other than OpenSSL. If you modify file(s) with this exception, you
 * may extend this exception to your version of the file(s), but you are not
 * obligated to do so. If you do not wish to do so, delete this exception
 * statement from your version. If you delete this exception statement from all
 * source files in the program, then also delete it here.
 *
 */

#include <libotr/proto.h>
#include <libotr/privkey.h>
#include <libotr/message.h>
#include <libotr/sm.h>
#include <glib.h>

#include "otr/otr.h"
#include "otr/otrlib.h"
#include "log.h"
#include "roster_list.h"
#include "contact.h"
#include "ui/ui.h"
#include "config/preferences.h"
#include "chat_session.h"

#define PRESENCE_ONLINE 1
#define PRESENCE_OFFLINE 0
#define PRESENCE_UNKNOWN -1

static OtrlUserState user_state;
static OtrlMessageAppOps ops;
static char *jid;
static gboolean data_loaded;
static GHashTable *smp_initiators;

OtrlUserState
otr_userstate(void)
{
    return user_state;
}

OtrlMessageAppOps *
otr_messageops(void)
{
    return &ops;
}

GHashTable *
otr_smpinitators(void)
{
    return smp_initiators;
}

// ops callbacks
static OtrlPolicy
cb_policy(void *opdata, ConnContext *context)
{
    return otrlib_policy();
}

static int
cb_is_logged_in(void *opdata, const char *accountname,
    const char *protocol, const char *recipient)
{
    PContact contact = roster_get_contact(recipient);

    // not in roster
    if (contact == NULL) {
        return PRESENCE_ONLINE;
    }

    // not subscribed
    if (p_contact_subscribed(contact) == FALSE) {
        return PRESENCE_ONLINE;
    }

    // subscribed
    if (g_strcmp0(p_contact_presence(contact), "offline") == 0) {
        return PRESENCE_OFFLINE;
    } else {
        return PRESENCE_ONLINE;
    }
}

static void
cb_inject_message(void *opdata, const char *accountname,
    const char *protocol, const char *recipient, const char *message)
{
    message_send_chat(recipient, message);
}

static void
cb_write_fingerprints(void *opdata)
{
    gcry_error_t err = 0;

    gchar *data_home = xdg_get_data_home();
    GString *basedir = g_string_new(data_home);
    free(data_home);

    gchar *account_dir = str_replace(jid, "@", "_at_");
    g_string_append(basedir, "/profanity/otr/");
    g_string_append(basedir, account_dir);
    g_string_append(basedir, "/");
    free(account_dir);

    GString *fpsfilename = g_string_new(basedir->str);
    g_string_append(fpsfilename, "fingerprints.txt");
    err = otrl_privkey_write_fingerprints(user_state, fpsfilename->str);
    if (!err == GPG_ERR_NO_ERROR) {
        log_error("Failed to write fingerprints file");
        cons_show_error("Failed to create fingerprints file");
    }
    g_string_free(basedir, TRUE);
    g_string_free(fpsfilename, TRUE);
}

static void
cb_gone_secure(void *opdata, ConnContext *context)
{
    ui_gone_secure(context->username, otr_is_trusted(context->username));
}

char *
otr_libotr_version(void)
{
    return OTRL_VERSION;
}

char *
otr_start_query(void)
{
    return otrlib_start_query();
}

void
otr_init(void)
{
    log_info("Initialising OTR");
    OTRL_INIT;

    ops.policy = cb_policy;
    ops.is_logged_in = cb_is_logged_in;
    ops.inject_message = cb_inject_message;
    ops.write_fingerprints = cb_write_fingerprints;
    ops.gone_secure = cb_gone_secure;

    otrlib_init_ops(&ops);
    otrlib_init_timer();
    smp_initiators = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_free);

    data_loaded = FALSE;
}

void
otr_shutdown(void)
{
    if (jid != NULL) {
        free(jid);
    }
}

void
otr_poll(void)
{
    otrlib_poll();
}

void
otr_on_connect(ProfAccount *account)
{
    if (jid != NULL) {
        free(jid);
    }
    jid = strdup(account->jid);
    log_info("Loading OTR key for %s", jid);

    gchar *data_home = xdg_get_data_home();
    GString *basedir = g_string_new(data_home);
    free(data_home);

    gchar *account_dir = str_replace(jid, "@", "_at_");
    g_string_append(basedir, "/profanity/otr/");
    g_string_append(basedir, account_dir);
    g_string_append(basedir, "/");
    free(account_dir);

    if (!mkdir_recursive(basedir->str)) {
        log_error("Could not create %s for account %s.", basedir->str, jid);
        cons_show_error("Could not create %s for account %s.", basedir->str, jid);
        g_string_free(basedir, TRUE);
        return;
    }

    user_state = otrl_userstate_create();

    gcry_error_t err = 0;

    GString *keysfilename = g_string_new(basedir->str);
    g_string_append(keysfilename, "keys.txt");
    if (!g_file_test(keysfilename->str, G_FILE_TEST_IS_REGULAR)) {
        log_info("No private key file found %s", keysfilename->str);
        data_loaded = FALSE;
    } else {
        log_info("Loading OTR private key %s", keysfilename->str);
        err = otrl_privkey_read(user_state, keysfilename->str);
        if (!err == GPG_ERR_NO_ERROR) {
            g_string_free(basedir, TRUE);
            g_string_free(keysfilename, TRUE);
            log_error("Failed to load private key");
            return;
        } else {
            log_info("Loaded private key");
            data_loaded = TRUE;
        }
    }

    GString *fpsfilename = g_string_new(basedir->str);
    g_string_append(fpsfilename, "fingerprints.txt");
    if (!g_file_test(fpsfilename->str, G_FILE_TEST_IS_REGULAR)) {
        log_info("No fingerprints file found %s", fpsfilename->str);
        data_loaded = FALSE;
    } else {
        log_info("Loading fingerprints %s", fpsfilename->str);
        err = otrl_privkey_read_fingerprints(user_state, fpsfilename->str, NULL, NULL);
        if (!err == GPG_ERR_NO_ERROR) {
            g_string_free(basedir, TRUE);
            g_string_free(keysfilename, TRUE);
            g_string_free(fpsfilename, TRUE);
            log_error("Failed to load fingerprints");
            return;
        } else {
            log_info("Loaded fingerprints");
            data_loaded = TRUE;
        }
    }

    if (data_loaded) {
        cons_show("Loaded OTR private key for %s", jid);
    }

    g_string_free(basedir, TRUE);
    g_string_free(keysfilename, TRUE);
    g_string_free(fpsfilename, TRUE);
    return;
}

void
otr_keygen(ProfAccount *account)
{
    if (data_loaded) {
        cons_show("OTR key already generated.");
        return;
    }

    if (jid != NULL) {
        free(jid);
    }
    jid = strdup(account->jid);
    log_info("Generating OTR key for %s", jid);

    gchar *data_home = xdg_get_data_home();
    GString *basedir = g_string_new(data_home);
    free(data_home);

    gchar *account_dir = str_replace(jid, "@", "_at_");
    g_string_append(basedir, "/profanity/otr/");
    g_string_append(basedir, account_dir);
    g_string_append(basedir, "/");
    free(account_dir);

    if (!mkdir_recursive(basedir->str)) {
        log_error("Could not create %s for account %s.", basedir->str, jid);
        cons_show_error("Could not create %s for account %s.", basedir->str, jid);
        g_string_free(basedir, TRUE);
        return;
    }

    gcry_error_t err = 0;

    GString *keysfilename = g_string_new(basedir->str);
    g_string_append(keysfilename, "keys.txt");
    log_debug("Generating private key file %s for %s", keysfilename->str, jid);
    cons_show("Generating private key, this may take some time.");
    cons_show("Moving the mouse randomly around the screen may speed up the process!");
    ui_update();
    err = otrl_privkey_generate(user_state, keysfilename->str, account->jid, "xmpp");
    if (!err == GPG_ERR_NO_ERROR) {
        g_string_free(basedir, TRUE);
        g_string_free(keysfilename, TRUE);
        log_error("Failed to generate private key");
        cons_show_error("Failed to generate private key");
        return;
    }
    log_info("Private key generated");
    cons_show("");
    cons_show("Private key generation complete.");

    GString *fpsfilename = g_string_new(basedir->str);
    g_string_append(fpsfilename, "fingerprints.txt");
    log_debug("Generating fingerprints file %s for %s", fpsfilename->str, jid);
    err = otrl_privkey_write_fingerprints(user_state, fpsfilename->str);
    if (!err == GPG_ERR_NO_ERROR) {
        g_string_free(basedir, TRUE);
        g_string_free(keysfilename, TRUE);
        log_error("Failed to create fingerprints file");
        cons_show_error("Failed to create fingerprints file");
        return;
    }
    log_info("Fingerprints file created");

    err = otrl_privkey_read(user_state, keysfilename->str);
    if (!err == GPG_ERR_NO_ERROR) {
        g_string_free(basedir, TRUE);
        g_string_free(keysfilename, TRUE);
        log_error("Failed to load private key");
        data_loaded = FALSE;
        return;
    }

    err = otrl_privkey_read_fingerprints(user_state, fpsfilename->str, NULL, NULL);
    if (!err == GPG_ERR_NO_ERROR) {
        g_string_free(basedir, TRUE);
        g_string_free(keysfilename, TRUE);
        log_error("Failed to load fingerprints");
        data_loaded = FALSE;
        return;
    }

    data_loaded = TRUE;

    g_string_free(basedir, TRUE);
    g_string_free(keysfilename, TRUE);
    g_string_free(fpsfilename, TRUE);
    return;
}

gboolean
otr_key_loaded(void)
{
    return data_loaded;
}

gboolean
otr_is_secure(const char * const recipient)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return FALSE;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return FALSE;
    } else {
        return TRUE;
    }
}

gboolean
otr_is_trusted(const char * const recipient)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return FALSE;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return TRUE;
    }

    if (context->active_fingerprint) {
        if (context->active_fingerprint->trust == NULL) {
            return FALSE;
        } else if (context->active_fingerprint->trust[0] == '\0') {
            return FALSE;
        } else {
            return TRUE;
        }
    }

    return FALSE;
}

void
otr_trust(const char * const recipient)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return;
    }

    if (context->active_fingerprint) {
        if (context->active_fingerprint->trust != NULL) {
            free(context->active_fingerprint->trust);
        }
        context->active_fingerprint->trust = strdup("trusted");
        cb_write_fingerprints(NULL);
    }

    return;
}

void
otr_untrust(const char * const recipient)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return;
    }

    if (context->active_fingerprint) {
        if (context->active_fingerprint->trust != NULL) {
            free(context->active_fingerprint->trust);
        }
        context->active_fingerprint->trust = NULL;
        cb_write_fingerprints(NULL);
    }

    return;
}

void
otr_smp_secret(const char * const recipient, const char *secret)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return;
    }

    // if recipient initiated SMP, send response, else initialise
    if (g_hash_table_contains(smp_initiators, recipient)) {
        otrl_message_respond_smp(user_state, &ops, NULL, context, (const unsigned char*)secret, strlen(secret));
        ui_otr_authenticating(recipient);
        g_hash_table_remove(smp_initiators, context->username);
    } else {
        otrl_message_initiate_smp(user_state, &ops, NULL, context, (const unsigned char*)secret, strlen(secret));
        ui_otr_authetication_waiting(recipient);
    }
}

void
otr_smp_question(const char * const recipient, const char *question, const char *answer)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return;
    }

    otrl_message_initiate_smp_q(user_state, &ops, NULL, context, question, (const unsigned char*)answer, strlen(answer));
    ui_otr_authetication_waiting(recipient);
}

void
otr_smp_answer(const char * const recipient, const char *answer)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context == NULL) {
        return;
    }

    if (context->msgstate != OTRL_MSGSTATE_ENCRYPTED) {
        return;
    }

    // if recipient initiated SMP, send response, else initialise
    otrl_message_respond_smp(user_state, &ops, NULL, context, (const unsigned char*)answer, strlen(answer));
}

void
otr_end_session(const char * const recipient)
{
    otrlib_end_session(user_state, recipient, jid, &ops);
}

char *
otr_get_my_fingerprint(void)
{
    char fingerprint[45];
    otrl_privkey_fingerprint(user_state, fingerprint, jid, "xmpp");
    char *result = strdup(fingerprint);

    return result;
}

char *
otr_get_their_fingerprint(const char * const recipient)
{
    ConnContext *context = otrlib_context_find(user_state, recipient, jid);

    if (context != NULL) {
        Fingerprint *fingerprint = context->active_fingerprint;
        char readable[45];
        otrl_privkey_hash_to_human(readable, fingerprint->fingerprint);
        return strdup(readable);
    } else {
        return NULL;
    }
}

prof_otrpolicy_t
otr_get_policy(const char * const recipient)
{
    ProfAccount *account = accounts_get_account(jabber_get_account_name());
    // check contact specific setting
    if (g_list_find_custom(account->otr_manual, recipient, (GCompareFunc)g_strcmp0)) {
        account_free(account);
        return PROF_OTRPOLICY_MANUAL;
    }
    if (g_list_find_custom(account->otr_opportunistic, recipient, (GCompareFunc)g_strcmp0)) {
        account_free(account);
        return PROF_OTRPOLICY_OPPORTUNISTIC;
    }
    if (g_list_find_custom(account->otr_always, recipient, (GCompareFunc)g_strcmp0)) {
        account_free(account);
        return PROF_OTRPOLICY_ALWAYS;
    }

    // check default account setting
    if (account->otr_policy != NULL) {
        prof_otrpolicy_t result;
        if (g_strcmp0(account->otr_policy, "manual") == 0) {
            result = PROF_OTRPOLICY_MANUAL;
        }
        if (g_strcmp0(account->otr_policy, "opportunistic") == 0) {
            result = PROF_OTRPOLICY_OPPORTUNISTIC;
        }
        if (g_strcmp0(account->otr_policy, "always") == 0) {
            result = PROF_OTRPOLICY_ALWAYS;
        }
        account_free(account);
        return result;
    }
    account_free(account);

    // check global setting
    char *pref_otr_policy = prefs_get_string(PREF_OTR_POLICY);

    // pref defaults to manual
    prof_otrpolicy_t result = PROF_OTRPOLICY_MANUAL;

    if (strcmp(pref_otr_policy, "opportunistic") == 0) {
        result = PROF_OTRPOLICY_OPPORTUNISTIC;
    } else if (strcmp(pref_otr_policy, "always") == 0) {
        result = PROF_OTRPOLICY_ALWAYS;
    }

    prefs_free_string(pref_otr_policy);

    return result;
}

char *
otr_encrypt_message(const char * const to, const char * const message)
{
    char *newmessage = NULL;
    gcry_error_t err = otrlib_encrypt_message(user_state, &ops, jid, to, message, &newmessage);

    if (err != 0) {
        return NULL;
    } else {
        return newmessage;
    }
}

char *
otr_decrypt_message(const char * const from, const char * const message, gboolean *was_decrypted)
{
    char *decrypted = NULL;
    OtrlTLV *tlvs = NULL;

    int result = otrlib_decrypt_message(user_state, &ops, jid, from, message, &decrypted, &tlvs);

    // internal libotr message
    if (result == 1) {
        ConnContext *context = otrlib_context_find(user_state, from, jid);

        // common tlv handling
        OtrlTLV *tlv = otrl_tlv_find(tlvs, OTRL_TLV_DISCONNECTED);
        if (tlv) {

            if (context != NULL) {
                otrl_context_force_plaintext(context);
                ui_gone_insecure(from);
            }
        }

        // library version specific tlv handling
        otrlib_handle_tlvs(user_state, &ops, context, tlvs, smp_initiators);

        return NULL;

    // message was decrypted, return to user
    } else if (decrypted != NULL) {
        *was_decrypted = TRUE;
        return decrypted;

    // normal non OTR message
    } else {
        *was_decrypted = FALSE;
        return strdup(message);
    }
}

void
otr_free_message(char *message)
{
    otrl_message_free(message);
}