Commit message: Ensure litlen isn't larger than our mailbox
CVE: CVE-2018-14351
CWE: CWE-20
Vulnerability description: An issue was discovered in Mutt before 1.10.1 and NeoMutt before 2018-07-16. imap/command.c mishandles a long IMAP status mailbox literal count size.

Project: neomutt

static void cmd_parse_status(struct ImapData *idata, char *s)
{
  char *value = NULL;
  struct Buffy *inc = NULL;
  struct ImapMbox mx;
  struct ImapStatus *status = NULL;
  unsigned int olduv, oldun;
  unsigned int litlen;
  short new = 0;
  short new_msg_count = 0;

  char *mailbox = imap_next_word(s);

  /* We need a real tokenizer. */
  if (imap_get_literal_count(mailbox, &litlen) == 0)
  {
    if (imap_cmd_step(idata) != IMAP_CMD_CONTINUE)
    {
       idata->status = IMAP_FATAL;
       return;
     }

    if (strlen(idata->buf) < litlen)
    {
      mutt_debug(1, "Error parsing STATUS mailbox\n");
      return;
    }

     mailbox = idata->buf;
     s = mailbox + litlen;
     *s = '\0';
    s++;
    SKIPWS(s);
  }
  else
  {
    s = imap_next_word(mailbox);
    *(s - 1) = '\0';
    imap_unmunge_mbox_name(idata, mailbox);
  }

  status = imap_mboxcache_get(idata, mailbox, 1);
  olduv = status->uidvalidity;
  oldun = status->uidnext;

  if (*s++ != '(')
  {
    mutt_debug(1, "Error parsing STATUS\n");
    return;
  }
  while (*s && *s != ')')
  {
    value = imap_next_word(s);

    errno = 0;
    const unsigned long ulcount = strtoul(value, &value, 10);
    if (((errno == ERANGE) && (ulcount == ULONG_MAX)) || ((unsigned int) ulcount != ulcount))
    {
      mutt_debug(1, "Error parsing STATUS number\n");
      return;
    }
    const unsigned int count = (unsigned int) ulcount;

    if (mutt_str_strncmp("MESSAGES", s, 8) == 0)
    {
      status->messages = count;
      new_msg_count = 1;
    }
    else if (mutt_str_strncmp("RECENT", s, 6) == 0)
      status->recent = count;
    else if (mutt_str_strncmp("UIDNEXT", s, 7) == 0)
      status->uidnext = count;
    else if (mutt_str_strncmp("UIDVALIDITY", s, 11) == 0)
      status->uidvalidity = count;
    else if (mutt_str_strncmp("UNSEEN", s, 6) == 0)
      status->unseen = count;

    s = value;
    if (*s && *s != ')')
      s = imap_next_word(s);
  }
  mutt_debug(3, "%s (UIDVALIDITY: %u, UIDNEXT: %u) %d messages, %d recent, %d unseen\n",
             status->name, status->uidvalidity, status->uidnext,
             status->messages, status->recent, status->unseen);

  /* caller is prepared to handle the result herself */
  if (idata->cmddata && idata->cmdtype == IMAP_CT_STATUS)
  {
    memcpy(idata->cmddata, status, sizeof(struct ImapStatus));
    return;
  }

  mutt_debug(3, "Running default STATUS handler\n");

  /* should perhaps move this code back to imap_buffy_check */
  for (inc = Incoming; inc; inc = inc->next)
  {
    if (inc->magic != MUTT_IMAP)
      continue;

    if (imap_parse_path(inc->path, &mx) < 0)
    {
      mutt_debug(1, "Error parsing mailbox %s, skipping\n", inc->path);
      continue;
    }

    if (imap_account_match(&idata->conn->account, &mx.account))
    {
      if (mx.mbox)
      {
        value = mutt_str_strdup(mx.mbox);
        imap_fix_path(idata, mx.mbox, value, mutt_str_strlen(value) + 1);
        FREE(&mx.mbox);
      }
      else
        value = mutt_str_strdup("INBOX");

      if (value && (imap_mxcmp(mailbox, value) == 0))
      {
        mutt_debug(3, "Found %s in buffy list (OV: %u ON: %u U: %d)\n", mailbox,
                   olduv, oldun, status->unseen);

        if (MailCheckRecent)
        {
          if (olduv && olduv == status->uidvalidity)
          {
            if (oldun < status->uidnext)
              new = (status->unseen > 0);
          }
          else if (!olduv && !oldun)
          {
            /* first check per session, use recent. might need a flag for this. */
            new = (status->recent > 0);
          }
          else
            new = (status->unseen > 0);
        }
        else
          new = (status->unseen > 0);

#ifdef USE_SIDEBAR
        if ((inc->new != new) || (inc->msg_count != status->messages) ||
            (inc->msg_unread != status->unseen))
        {
          mutt_menu_set_current_redraw(REDRAW_SIDEBAR);
        }
#endif
        inc->new = new;
        if (new_msg_count)
          inc->msg_count = status->messages;
        inc->msg_unread = status->unseen;

        if (inc->new)
        {
          /* force back to keep detecting new mail until the mailbox is
             opened */
          status->uidnext = oldun;
        }

        FREE(&value);
        return;
      }

      FREE(&value);
    }

    FREE(&mx.mbox);
  }
}