Category: Technology

Python: Listing XML tags

I was having a lot of trouble using find/findall when parsing an XML document — turns out the namespace prefixed the tag name … so I needed to find {http://maven.apache.org/POM/4.0.0}groupId instead of just groupId

How do you figure that out? Quickest way, for me, was just to print out all of the tag names.

from lxml import etree
# Load POM XML into tree
tree = etree.parse( strXMLFile )

# # List all element names in XML document
for element in tree.iter():
     print(element.tag)

Updating Fedora — System Boots to Grub Error After Update

If you film the boot sequence and look frame by frame, you’ll see that it very briefly flashes a TPM error

error: ../../grub-core/commands/efi/tpm.c:150:unknown TPM error.

 

From what I’ve been able to glean, this secure boot stuff works off of signatures. Microsoft has signatures in BIOS. Everyone else kind of inserts their keys on the fly … so you can run out of space to save these keys and be unable to boot. To work around this, every time an update gets us over the limit, we go into the secure boot DBX management menu and reset the “Forbidden Signatures” from factory default. This is 13 keys instead of 373, and the OS is able to do it’s “thing” and boot.

 

And I’m actually writing this down this time because I had spent a lot of time researching this last time Scott’s laptop failed to boot and dumped out to a grub menu. This time, I kinda know what we did and why but lost a lot of the details.

RSync to Mirror Local Files

The rsync utility was meant to be used to sync files across the network — to or from an rsync server. For some time, I had a group of friends who shared documents off of my rsync server. Anyone with access could run an rsync command and sync their computer up with the group’s documents. With the advent of online file storage and collaborative editing, this was no longer needed. But I still use rsync to make sure my laptop has a local copy of a folder on the server. Mount /path/to/folder/contents/to/copy to the SMB or NFS share, and the following rsync command ensures the laptop’s /path/to/where/contents/should/be/placed has an exact mirror of the contents of the server folder

rsync –archive –verbose –update –delete “/path/to/folder/contents/to/copy/” “/path/to/where/contents/should/be/placed/”

–archive is a grouping of:
-r recursive
-l copy symlinks
-p preserve permissions
-t preserve modification timestamps
-g preserve group
-o preserve owner
–devices preserve device files (su only)
–specials preserve special files

Python: Generate Transcript of Video File

There’s a speech_recognition module in Python that transcribes an audio file — since ffmpeg can convert a video file to mp3, that means you can also use Python to transcribe a video file. 

# requires pocketsphinx from CMU if using sphinx for speech to text recognition
import os
import speech_recognition as sr
import ffmpeg

strFFMPEGBinaryLocation = 'c:/tmp/ffmpeg/bin/ffmpeg.exe'
strCurrentDirectory = os.getcwd()

strInputVideo = "\"Z:/Path To/My Video/file.MP4\""
strOutputFileName = "converted.wav"
# Convert mp4 to wav file
strffmpeg_convert_mp4_to_wav = f'{strFFMPEGBinaryLocation} -i {strInputVideo} {strCurrentDirectory}/{strOutputFileName}'
os.system(strffmpeg_convert_mp4_to_wav)

# Run converted wav file through speech recognizer
r = sr.Recognizer()
audio = sr.AudioFile(f'{strCurrentDirectory}/{strOutputFileName}')

with audio as source:
	#audio = r.record(source, 90)				# Would need API key to process longer audio?
	#text = r.recognize_google(audio)
	audio = r.record(source)
	text = r.recognize_sphinx(audio)
print(text)

PowerShell: Mass Active Directory Password Changes

We have a bunch of accounts that function as extra mailboxes — all conveniently housed in on OU. The following PowerShell command sets the password for all of the accounts in one go. Not terribly useful for “real world” use … but useful for testing (and probably something I’ll end up using again)

$OUpath = ‘ou=Mail Aliases,dc=example,dc=com’
$strNewPassword = “What3v3rYu0W@nt1tT0B3”

Get-ADUser -Filter * -SearchBase $OUpath | Set-ADAccountPassword -Reset -NewPassword (ConvertTo-SecureString -AsPlainText $strNewPassword -Force)

Python Code — Creating Title Images

Instead of allowing YouTube to randomly pick a frame to use as the preview image, I have always made a title image for the Township meetings I post to YouTube. At first, this was a manual (and thus time consuming for a lot of videos). In the interim, I have created a script that generates the color gradient background and overlays text including the meeting type and date. 

# Valid meeting types: "TrusteeRegular",  "TrusteeSpecial", "TrusteeEmer", "TrusteeHearing", "BZAReg", "BZAHearing", "ZCReg", "ZCHearing"
strMeetingListSpreadsheet = 'MeetingList.xlsx'

from PIL import Image, ImageDraw, ImageFont
import pandas as pd

BLACK= (0,0,0)
WHITE = (255,255,255)

TRUSTEE_COLOR_PALETTE = [(156,12,12), (92,7,7), (0,0,0)]
BZA_COLOR_PALETTE = [(253,139,1), (91,51,0), (0,0,0)]
ZC_COLOR_PALETTE = [(24,113,56), (8,41,20), (0,0,0)]
MISC_COLOR_PALETTE = [(175,28,195), (55,9,61), (0,0,0)]

objFontMeetingTitle = ImageFont.truetype("/usr/share/fonts/liberation-sans/LiberationSans-Regular.ttf",115)
objFontMeetingTopic = ImageFont.truetype("/usr/share/fonts/liberation-sans/LiberationSans-Regular.ttf",115)
objFontMeetingDate = ImageFont.truetype("/usr/share/fonts/liberation-sans/LiberationSans-Italic.ttf",95)

class Point(object):
    def __init__(self, x, y):
        self.x, self.y = x, y

class Rect(object):
    def __init__(self, x1, y1, x2, y2):
        minx, maxx = (x1,x2) if x1 < x2 else (x2,x1)
        miny, maxy = (y1,y2) if y1 < y2 else (y2,y1)
        self.min = Point(minx, miny)
        self.max = Point(maxx, maxy)

    width  = property(lambda self: self.max.x - self.min.x)
    height = property(lambda self: self.max.y - self.min.y)

def gradient_color(minval, maxval, val, color_palette):
    """ Computes intermediate RGB color of a value in the range of minval
        to maxval (inclusive) based on a color_palette representing the range.
    """
    max_index = len(color_palette)-1
    delta = maxval - minval
    if delta == 0:
        delta = 1
    v = float(val-minval) / delta * max_index
    i1, i2 = int(v), min(int(v)+1, max_index)
    (r1, g1, b1), (r2, g2, b2) = color_palette[i1], color_palette[i2]
    f = v - i1
    return int(r1 + f*(r2-r1)), int(g1 + f*(g2-g1)), int(b1 + f*(b2-b1))

def horz_gradient(draw, rect, color_func, color_palette):
    minval, maxval = 1, len(color_palette)
    delta = maxval - minval
    width = float(rect.width)  # Cache.
    for x in range(rect.min.x, rect.max.x+1):
        f = (x - rect.min.x) / width
        val = minval + f * delta
        color = color_func(minval, maxval, val, color_palette)
        draw.line([(x, rect.min.y), (x, rect.max.y)], fill=color)

def vert_gradient(draw, rect, color_func, color_palette):
    minval, maxval = 1, len(color_palette)
    delta = maxval - minval
    height = float(rect.height)  # Cache.
    for y in range(rect.min.y, rect.max.y+1):
        f = (y - rect.min.y) / height
        val = minval + f * delta
        color = color_func(minval, maxval, val, color_palette)
        draw.line([(rect.min.x, y), (rect.max.x, y)], fill=color)


if __name__ == '__main__':
    df = pd.read_excel(strMeetingListSpreadsheet, sheet_name="Sheet1")

    df = df.reset_index()  # make sure indexes pair with number of rows

    for index, row in df.iterrows():
        strGraphicName = f"{row['Date'].strftime('%Y%d%m')}-{row['Type']}.png"
        strMeetingType = row['Type']

        # Draw a three color horizontal gradient.
        region = Rect(0, 0, 1920, 1080)
        width, height = region.max.x+1, region.max.y+1
        image = Image.new("RGB", (width, height), BLACK)
        draw = ImageDraw.Draw(image)

        # Add meeting title
        if strMeetingType == "TrusteeRegular":
            horz_gradient(draw, region, gradient_color, TRUSTEE_COLOR_PALETTE)
            draw.text((1670, 525),"Trustee Regular Meeting",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "TrusteeSpecial":
            horz_gradient(draw, region, gradient_color, TRUSTEE_COLOR_PALETTE)
            draw.text((1670, 525),"Trustee Special Meeting",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "TrusteeEmer":
            horz_gradient(draw, region, gradient_color, TRUSTEE_COLOR_PALETTE)
            draw.text((1670, 525),"Trustee Emergency Meeting",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "TrusteeHearing":
            horz_gradient(draw, region, gradient_color, TRUSTEE_COLOR_PALETTE)
            draw.text((1670, 525),"Trustee Public Hearing",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "BZAReg":
            horz_gradient(draw, region, gradient_color, BZA_COLOR_PALETTE)
            draw.text((1670, 525),"BZA Regular Meeting",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "BZAHearing":
            horz_gradient(draw, region, gradient_color, BZA_COLOR_PALETTE)
            draw.text((1670, 525),"BZA Public Hearing",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "ZCReg":
            horz_gradient(draw, region, gradient_color, ZC_COLOR_PALETTE)
            draw.text((1670, 525),"Zoning Commission Meeting",WHITE,font=objFontMeetingTopic, anchor="rm")
        elif strMeetingType == "ZCHearing":
            horz_gradient(draw, region, gradient_color, ZC_COLOR_PALETTE)
            draw.text((1670, 525),"Zoning Commission Hearing",WHITE,font=objFontMeetingTopic, anchor="rm")
        else:
            horz_gradient(draw, region, gradient_color, MISC_COLOR_PALETTE)
            draw.text((1670, 525),"Township Meeting",WHITE,font=objFontMeetingTopic, anchor="rm")

        # Add township and date
        draw.text((1070, 225),"Hinckley Township",WHITE,font=objFontMeetingTitle, anchor="rm")
        draw.text((1770, 825),row['Date'].strftime('%B %d, %Y'),WHITE,font=objFontMeetingDate, anchor="rm")

        image.save(strGraphicName, "PNG")
        print(f"image saved as {strGraphicName}")

I have an Excel file which contains the meeting type code, a long meeting title that is used as the second line of the image, a date (and a MeetingDate that I use in my concat formulae that create the title and description for YouTube). To use an Excel date in concat, you need to use a TEXT formula with the text formatting string.

This allows me to have a consistent preview image for all of our postings without actually making dozens of files by hand.

ZFS Compression Ratio

We’ve got several PostgreSQL servers using ZFS file system for the database, and I needed to know how compressed the data is. Fortunately, there appears to be a zfs command that does exactly that: report the compression ratio for a zfs file system. Use zfs get compressratio /path/to/mount

Web Proxy Auto Discovery (WPAD) DNS Failure

I wanted to set up automatic proxy discovery on our home network — but it just didn’t work. The website is there, it looks fine … but it doesn’t work. Turns out Microsoft introduced some security idea in Windows 2008 that prevents Windows DNS servers from serving specific names. They “banned” Web Proxy Auto Discovery (WPAD) and Intra-site Automatic Tunnel Addressing Protocol (ISATAP). Even if you’ve got a valid wpad.example.com host recorded in your domain, Windows DNS server says “Nope, no such thing!”. I guess I can appreciate the logic — some malicious actor can hijack all of your connections by tunnelling or proxying your traffic. But … doesn’t the fact I bothered to manually create a hostname kind of clue you into the fact I am trying to do this?!?

I gave up and added the proxy config to my group policy — a few computers, then, needed to be manually configured. It worked. Looking in the event log for a completely different problem, I saw the following entry:

Event ID 6268

The global query block list is a feature that prevents attacks on your  network by blocking DNS queries for specific host names. This feature has caused the DNS server to fail a query with error code NAME ERROR for wpad.example.com. even though data for this DNS name exists in the DNS database. Other queries in all locally authoritative zones for other names
that begin with labels in the block list will also fail, but no event will be logged when further queries are blocked until the DNS server service on this computer is restarted. See product documentation for information about this feature and instructions on how to configure it.

The oddest bit is that this appears to be a substring ‘starts with’ query — like wpadlet or wpadding would also fail? A quick search produced documentation on this Global Query Blocklist … and two quick ways to resolve the issue.

(1) Change the block list to contain only the services you don’t want to use. I don’t use ISATAP, so blocking isatap* hostnames isn’t problematic:

dnscmd /config /globalqueryblocklist isatap

View the current blocklist with:

dnscmd /info /globalqueryblocklist

– Or –

(2) Disable the block list — more risk, but it avoids having to figure this all out again in a few years when a hostname starting with isatap doesn’t work for no reason!

dnscmd /config /enableglobalqueryblocklist 0