George Michael


An attempt to use images in WP-Polls

Recently we needed to make a poll with images in WordPress.
On our system we only had WP-Polls installed and we decided to go along with it despite its drawbacks.

Drawbacks of using WP-Polls:

  • Does not support polls with images directly.
  • Does not allow you to configure ‘Poll Options’ per poll.
    For example, either all polls are logged by username or none is.

WP-Polls

In any case, we only needed one poll for a very specific task so we decided to ignore those limitations and see what we could do with the current vanilla code of WP-Polls ( WP-Polls 2.73.8 (retrieved on 2017 Dec 18) (1 download) ).

What we did was the following:

A: We configured the system to only allow registered users to vote and set the vote logging to be per username

B: We modified the templates below to receive the poll answers as URIs for images.

Voting Form Body:

<li><input type="%POLL_CHECKBOX_RADIO%" id="poll-answer-%POLL_ANSWER_ID%" name="poll_%POLL_ID%" value="%POLL_ANSWER_ID%" /> <label for="poll-answer-%POLL_ANSWER_ID%"><img src="%POLL_ANSWER%" />%POLL_ANSWER%</label></li>

Result Body:
Displayed When The User HAS NOT Voted

<li><img src="%POLL_ANSWER%" />%POLL_ANSWER% <small>(%POLL_ANSWER_PERCENTAGE%%, %POLL_ANSWER_VOTES% Votes)</small><div class="pollbar" style="width: %POLL_ANSWER_IMAGEWIDTH%%" title="%POLL_ANSWER_TEXT% (%POLL_ANSWER_PERCENTAGE%% | %POLL_ANSWER_VOTES% Votes)"></div></li>

Result Body:
Displayed When The User HAS Voted

<li><img src="%POLL_ANSWER%" /><strong><i>%POLL_ANSWER% <small>(%POLL_ANSWER_PERCENTAGE%%, %POLL_ANSWER_VOTES% Votes)</small></i></strong><div class="pollbar" style="width: %POLL_ANSWER_IMAGEWIDTH%%" title="You Have Voted For This Choice - %POLL_ANSWER_TEXT% (%POLL_ANSWER_PERCENTAGE%% | %POLL_ANSWER_VOTES% Votes)"></div></li>

These two changes produced the following result:

Vote for the best filter

  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-14.jpg (36%, 23 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-11.jpg (30%, 19 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-15.jpg (23%, 15 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-10.jpg (8%, 5 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-13.jpg (2%, 1 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-08.jpg (2%, 1 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-12.jpg (0%, 0 Votes)
  • http://bytefreaks.net/wp-content/uploads/2017/06/Wooden-Spoon-Carving-With-Mat-Holloway-09.jpg (0%, 0 Votes)

Total Voters: 64

Loading ... Loading ...

We did not fiddle with the CCS of the site to make the polls look better or anything as it was OK for the scenario that we cared about.


Windows XP: Extend evaluation period (Not a permanent solution)

Recently, an old machine running Windows XP SP3 had its hard disk replaced, since then the OS decided that the license was not valid and considered itself to be in a trial/evaluation 30 days period.
Since the activation/validation services of Windows XP got discontinued we could not reactivate the current setup using the internet.
We tried a few times to activate via phone but it failed as well..

Temporary Solution (mitigating the problem)

To give us some time to think about a solution, whenever Windows XP would say that the evaluation period was expired, we would boot into safe mode and then run this command rundll32.exe syssetup,SetupOobeBnk (in cmd.exe or in the Run option that is in the Start menu) that allows you to reset the evaluation period for up to 4 times (and if used properly will give you 150 days in total to find a solution).

Actual Solution

In the end, we used the installation CD to downgrade the installation using the repair option, then we tried the telephone activation again and it worked!
Although Windows XP was not complaining any more, that caused us some problems with the antivirus, as a shared system library (DLL) that was replaced was not compatible with the antivirus.
To resolve this issue, we booted the machine using a GNU/Linux live CD and replaced the library (DLL) from a backup that was in the old disk.

Warning: Downgrading the system using the installation CD most probably re-enabled old exploits and hacks making the system less secure.
Keep this information in mind as you cannot re-apply the updates to the system not even the security updates any more.


Reasons I got involved in Computer Science and Informatics

  • From a young age, I found it very interesting
  • I have a good friend that supported me all the way
  • It is fun and challenging!
  • There are so many different topics, once you get bored of one you can skip to the next
  • There are new topics and challenges almost every day
  • It is something that you can teach yourself (especially nowadays that there is so much free material online)

Viber Desktop on Fedora 27 64bit: Viber cannot connect to the internet (OpenSSL error)

After updating our GNU/Linux distribution from Fedora 26 to Fedora 27, and maybe updating Viber Desktop client as well, Viber stopped working. To be more precise it could not connect to the internet any more. (Note: we used the RPM package of Viber Desktop to install Viber on our Fedora system).

Solution for the OpenSSL issue – Create a symbolic link to the missing library in the libraries folder of Viber

#Make sure all necessary packages are installed
sudo dnf install openssl openssl-devel;
#Create a symbolic link from the system installed libssl shared object to the Viber installation folder
sudo ln -s /usr/lib64/libssl.so.10 /opt/viber/lib/libssl.so;

Explanation and details – Optional Reading

To find the installation folder of Viber, we used the following command:

find / -iname viber 2>/dev/null;

that led us to the installation location of Viber which was /opt/viber/Viber.

Executing the binary in a terminal gave us the following errors

$ /opt/viber/Viber
 Qt WebEngine ICU data not found at /opt/viber/resources. Trying parent directory...
 Qt WebEngine resources not found at /opt/viber/resources. Trying parent directory...
 Qt WebEngine ICU data not found at /opt/viber/resources. Trying parent directory...
 Qt WebEngine resources not found at /opt/viber/resources. Trying parent directory...
 qt.network.ssl: QSslSocket: cannot resolve CRYPTO_num_locks
 qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_id_callback
 qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_locking_callback
 qt.network.ssl: QSslSocket: cannot resolve ERR_free_strings
 qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_cleanup
 qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_init
 qt.network.ssl: QSslSocket: cannot resolve sk_new_null
 qt.network.ssl: QSslSocket: cannot resolve sk_push
 qt.network.ssl: QSslSocket: cannot resolve sk_free
 qt.network.ssl: QSslSocket: cannot resolve sk_num
 qt.network.ssl: QSslSocket: cannot resolve sk_pop_free
 qt.network.ssl: QSslSocket: cannot resolve sk_value
 qt.network.ssl: QSslSocket: cannot resolve SSL_library_init
 qt.network.ssl: QSslSocket: cannot resolve SSL_load_error_strings
 qt.network.ssl: QSslSocket: cannot resolve SSL_get_ex_new_index
 qt.network.ssl: QSslSocket: cannot resolve SSLv23_client_method
 qt.network.ssl: QSslSocket: cannot resolve SSLv23_server_method
 qt.network.ssl: QSslSocket: cannot resolve X509_STORE_CTX_get_chain
 qt.network.ssl: QSslSocket: cannot resolve OPENSSL_add_all_algorithms_noconf
 qt.network.ssl: QSslSocket: cannot resolve OPENSSL_add_all_algorithms_conf
 qt.network.ssl: QSslSocket: cannot resolve SSLeay
 qt.network.ssl: QSslSocket: cannot resolve SSLeay_version
 qt.network.ssl: Incompatible version of OpenSSL
 qt.network.ssl: QSslSocket: cannot call unresolved function SSLv23_client_method
 qt.network.ssl: QSslSocket: cannot call unresolved function SSL_library_init
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 qt.network.ssl: QSslSocket: cannot call unresolved function SSLv23_client_method
 qt.network.ssl: QSslSocket: cannot call unresolved function SSL_library_init
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 qt.network.ssl: QSslSocket: cannot call unresolved function SSLv23_client_method
 qt.network.ssl: QSslSocket: cannot call unresolved function SSL_library_init

From the error we could see that the application was trying to access the functions SSLv23_client_method and SSL_library_init and it could not find them.
It was obvious that the missing functions were related to the SSL protocol, so we executed the following to make sure all necessary OpenSSL packages were installed.

sudo dnf install openssl openssl-devel;

After that we tried Viber again and gave us the same error.
So we made the assumption that Viber could not ‘see’ the installation of OpenSSL.
Then we decided to use the following command to:

  1. find all shared objects (shared libraries) of OpenSSL on our system,
  2. list all of the available functions in each shared library and
  3. identify the ones that contain the SSLv23_client_method method.
find / -iname libssl.so* -print -exec sh -c 'nm -D "$1" | grep SSLv23_client_method' _ {} \; 2>/dev/null;

Executing the command yielded the following results:

$ find / -iname libssl.so* -print -exec sh -c 'nm -D "$1" | grep SSLv23_client_method' _ {} \; 2>/dev/null;
 /usr/lib/libssl.so
 /usr/lib/libssl.so.1.1
 /usr/lib/libssl.so.10
 00027880 T SSLv23_client_method
 /usr/lib/libssl.so.1.0.2m
 00027880 T SSLv23_client_method
 /usr/lib/libssl.so.1.1.0g
 /usr/lib64/libssl.so
 /usr/lib64/libssl.so.1.1
 /usr/lib64/libssl.so.10
 000000000002dd10 T SSLv23_client_method
 /usr/lib64/libssl.so.1.0.2m
 000000000002dd10 T SSLv23_client_method
 /usr/lib64/libssl.so.1.1.0g
 /opt/viber/lib/libssl.so

From the results two libraries in the lib64 folder got our interest, so we executed ls -l on both to check them out:

$ ls -l /usr/lib64/libssl.so.10 /usr/lib64/libssl.so.1.0.2m;
lrwxrwxrwx. 1 root root 16 Nov 13 13:52 /usr/lib64/libssl.so.10 -> libssl.so.1.0.2m
-rwxr-xr-x. 1 root root 448640 Nov 13 13:52 /usr/lib64/libssl.so.1.0.2m

As you can see in the results, the two files that got us interested were in end the same file so we decided to use /usr/lib64/libssl.so.10 whose name was not tight to a minor distribution version of the library and would automatically link to any minor updates in the future.

After examining the Viber installation folder in /opt/viber/, we saw that there was a lib folder there with no SSL libraries available (even though all the QT and networking libraries were there already):

$ ls /opt/viber/lib/
libicudata.so.52 libQt5Gui.so.5 libQt5Qml.so.5 libQt5WebEngine.so.5
libicui18n.so.52 libQt5Location.so.5 libQt5QuickControls2.so.5 libQt5WebEngineWidgets.so.5
libicuuc.so.52 libQt5MultimediaQuick_p.so.5 libQt5Quick.so.5 libQt5WebSockets.so.5
libpng12.so.0 libQt5Multimedia.so.5 libQt5QuickTemplates2.so.5 libQt5Widgets.so.5
libqgsttools_p.so.1 libQt5MultimediaWidgets.so.5 libQt5QuickWidgets.so.5 libQt5XcbQpa.so.5
libqrencode.so libQt5Network.so.5 libQt5Sql.so.5
libQt5Concurrent.so.5 libQt5OpenGL.so.5 libQt5Svg.so.5 libxcb-xinerama.so.0
libQt5Core.so.5 libQt5Positioning.so.5 libQt5WebChannel.so.5
libQt5DBus.so.5 libQt5PrintSupport.so.5 libQt5WebEngineCore.so.5

Examining our OS, we saw that in the rest of the locations were the QT libraries were installed there was a copy of the libssl as well.
So we decided to make a soft symbolic link of the /usr/lib64/libssl.so.10 shared library in the Viber libraries folder.
We did two tests:

  1. Creating a symbolic link named libssl.so.10 failed.
  2. Creating a symbolic link name libssl.so succeeded and solved the issue!

The command that we used was the following:

sudo ln -s /usr/lib64/libssl.so.10 /opt/viber/lib/libssl.so;

After performing this step, Viber was working again as expected!

$ sudo ln -s /usr/lib64/libssl.so.10 /opt/viber/lib/libssl.so;
 $ /opt/viber/Viber
 Qt WebEngine ICU data not found at /opt/viber/resources. Trying parent directory...
 Qt WebEngine resources not found at /opt/viber/resources. Trying parent directory...
 Qt WebEngine ICU data not found at /opt/viber/resources. Trying parent directory...
 Qt WebEngine resources not found at /opt/viber/resources. Trying parent directory...
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 QQuickItem: Cannot set activeFocusOnTab to false once item is the active focus item.
 qml: type=""
 qml: type=""
 qrc:/QML/Feed/FeedView.qml:98:5: QML ListViewEx: Binding loop detected for property "bottomMargin"
 QObject: Cannot create children for a parent that is in a different thread.
 (Parent is QObject(0x7f3f5f970520), parent's thread is QThread(0x4191210), current thread is QThread(0x515f5b0)
 Invalid SOS parameters for sequential JPEG

Success!


Android Studio – No space left on device 1

Recently we tried to install some packages from the Android SDK through Android Studio 3.0.1 and we got the error that the PC ran out of space while downloading the necessary packages and could not perform the operation.

Full Error Log:

To install:
- Google APIs Intel x86 Atom System Image (system-images;android-27;google_apis;x86)
Preparing "Install Google APIs Intel x86 Atom System Image (revision: 2)".
Downloading https://dl.google.com/android/repository/sys-img/google_apis/x86-27_r02.zip
An error occurred while preparing SDK package Google APIs Intel x86 Atom System Image: Cannot download 'https://dl.google.com/android/repository/sys-img/google_apis/x86-27_r02.zip': No space left on device
, response: 200 OK.
"Install Google APIs Intel x86 Atom System Image (revision: 2)" failed.
Failed packages:
- Google APIs Intel x86 Atom System Image (system-images;android-27;google_apis;x86)

Although the disk had a lot of free space, we got this error because the /tmp partition on our GNU/Linux Fedora 27 workstation was too small (~4GB).

$ df -h;
Filesystem Size Used Avail Use% Mounted on
devtmpfs 3.9G 0 3.9G 0% /dev
tmpfs 3.9G 107M 3.8G 3% /dev/shm
tmpfs 3.9G 1.9M 3.9G 1% /run
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/mapper/fedora-root 50G 35G 12G 75% /
tmpfs 3.9G 2.1M 3.9G 1% /tmp
/dev/sdb1 477M 179M 269M 41% /boot
/dev/mapper/fedora-home 178G 37G 132G 22% /home
tmpfs 794M 16K 794M 1% /run/user/42
tmpfs 794M 9.2M 785M 2% /run/user/1000

/tmp was not explicitly set so it was automatically configured to have half of the size of the RAM.
We didn’t not want to change the download path for the Java environment (and hence Android Studio and Android SDK tools) as after leaving the tmpfs folder it could mean that we would have to manually maintain the new path and clean it up. So we ended up in temporarily increasing the size of /tmp partition which did the trick and the virtual device was installed successfully.

Solution – temporarily increase the size of the /tmp partition:

The command we used to increase the size of the /tmp partition on Fedora 27 was the following:

sudo mount -o remount,size=8G,noatime /tmp;

After executing we, it we immediately saw that the results were applied without the need for a restart or any other operation and we could proceed to use the PC as normal.

$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 3.9G 0 3.9G 0% /dev
tmpfs 3.9G 89M 3.8G 3% /dev/shm
tmpfs 3.9G 1.9M 3.9G 1% /run
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/mapper/fedora-root 50G 35G 12G 75% /
tmpfs 8.0G 2.0M 8.0G 1% /tmp
/dev/sdb1 477M 179M 269M 41% /boot
/dev/mapper/fedora-home 178G 37G 132G 22% /home
tmpfs 794M 16K 794M 1% /run/user/42
tmpfs 794M 6.9M 787M 1% /run/user/1000

The information for tmpfs we got it from: https://wiki.archlinux.org/index.php/Tmpfs

Full Correct Execution Log:

To install:
- Google APIs Intel x86 Atom System Image (system-images;android-27;google_apis;x86)
Preparing "Install Google APIs Intel x86 Atom System Image (revision: 2)".
Downloading https://dl.google.com/android/repository/sys-img/google_apis/x86-27_r02.zip
"Install Google APIs Intel x86 Atom System Image (revision: 2)" ready.
Installing Google APIs Intel x86 Atom System Image in /home/xeirwn/Android/Sdk/system-images/android-27/google_apis/x86
"Install Google APIs Intel x86 Atom System Image (revision: 2)" complete.
"Install Google APIs Intel x86 Atom System Image (revision: 2)" finished.


How to process tcpdump live data stream from a remote machine on a local WireShark

Recently we needed to process the results of a tcpdump command using the GUI version of WireShark on machine that did not have a window manager installed. That device was an embedded device, for which it did not make sense to even consider installing a window manager on it. So, in order to process the results of the tcpdump command we decided to use another machine that had a full working window manager installed and was able to operate the GUI version of WireShark.

For our solution to work some requirements were expected to be met by the embedded device (a.k.a. remote machine).

  1. tcpdump was installed on the remote machine
  2. ssh server was installed on the remote machine and allowed us to connect to it remotely
  3. there was a user that had remote ssh rights on the remote machine that also had the rights to execute tcpdump on the needed interfaces

Synopsis of our solution:

Just execute the following on the machine with the GUI (a.k.a. local machine)

mkfifo /tmp/board;
wireshark -k -i /tmp/board &
ssh [email protected] "tcpdump -s 0 -U -n -w - -i lo not port 22" > /tmp/board;

Explanation of our solution:

Following are the steps that we performed on the local machine to pipe the results of tcpdump on the remote machine on the wireshark on the local machine.

  1. First we created a named pipe as follows:
    mkfifo /tmp/board;
    You can name your pipe anyway you like and place it in any folder you wish. We used /tmp as our pipe is a temporary construct that we do not care to preserve across time/restarts.
  2. Then we started wireshark from a terminal so that we could pass as capture interface the named pipe we just created using the -i /tmp/board parameter. The -k parameter instructs wireshark to start the capture session immediately.
    wireshark -k -i /tmp/board &
    Since this operation was going to execute for a long time, we sent it to the background to release the terminal for further use by placing the & symbol at the end of the command.
  3. Finally, we started tcpdump over ssh on a board and redirected its output to our named pipe.
    ssh [email protected] "tcpdump -s 0 -U -n -w - -i lo not port 22" > /tmp/board;
    The parameters we used on tcpdump have the following effects:
    -s 0 instructs tcpdump to set the snapshot length of data from each packet to the default value of 262144 bytes.
    -U Since the -w option is not specified, make the printed packet output packet-buffered. Which means that it will print the description of the contents of each packet without waiting for the output buffer to get full.
    -n Does not convert host addresses to names. This can be used to avoid DNS lookups.
    -w - Write the raw packets to Standard Output rather than parsing them.
    -i lo Defines which interface to listen on. We wanted the loopback interface to listen to everything.
    not port 22 Since we used ssh to start this command, we do not want to listen to the data that we produce as well and flood the inputs.