Alternatives to storing image data in script as Base64 string?

Question

Alternatives to storing image data in script as Base64 string?

DaveK 1,871

Hi,

So after much head scratching and searching for a script which seems to have gone walkabout, it turns out its a false positive detection in my AV which has caused the issue and deleted my script! I'll be able to put an exception in the AV for the file, restore it from backup etc so in this instance it isn't causing a problem know I know about it but its got me thinking on if it happens again.

The script in question emails its output to a few users and I'm using a HTML body to generate dynamic content depending on the script result and I've included an image as as header in keeping with company branding etc - all worked fine for years. It turns out it seems to be the image which is encoder in Base64 that causes the issue as with the $headerfile = "base64#1234hjgetr etc" removed, the detection stops and the AV leaves me alone again.

I've had a quick web search for if using Base64 to encode images to string is the best way forward and a few sources has said possibly not so I was wondering what others think and if there are any different approaches I can take. My goal is to have the script contain the image so I'm only ever needing to move the one ps1 file around and from a code point of view, I can just copy the email function out of the script to re-use knowing it will always have the right corporate feel to it without having to start from scratch.

Does anyone has any suggestion on how I can encode images to be contained within the script to avoid having to copy image files alongside the script and load from storage? I don't want to upload to cloud or share the images from a central share.

cheers

Rich Matheisen 47,901 Reputation points

2023-03-01T20:10:49.26+00:00

I think "Windows Server PowerShell" isn't the best place to ask for advice like this. The "base64" part of the "img" tag's "src" identifies a "user agent". In the situation you're asking about that's how the web browser discovers how to deal with the decoding. If you choose another encoding format you'd have to be sure that the user agent was available on all the client machines that receive your email, and that all the web browsers used on those machines had a version of that user agent, too.

A better way is to place the image on a web server and provide an "alt" tag describing the image for those that, perhaps, have either no access to the web server (e.g. it's not accessible outside your LAN), are visually impaired, etc.
DaveK 1,871 Reputation points

2023-03-02T11:09:03.87+00:00

Hi, Sorry I should have been clearer on how the Base64 string is used. The image is inserted as an inline PNG image decoded as part of script using a steam and creating the image using LinkedResource(Stream, ContentType) so it isn't used directly in the img tag - I've tried that in the past and had all kind of issues with clients as you mention.

I was wondering more if there are any other methods to 'embed' the image into my script for use in the same manor but hopefully without it triggering the same AV false positive the Base64 data does. I've other scripts which use the same method which don't produce the false positive so I'm thinking its more

It was a little bit of a long short using the Windows Server PowerShell tag I'll admit but I'm aware there are some experienced minds here so was worth a go :)
Rich Matheisen 47,901 Reputation points

2023-03-02T20:13:47.8433333+00:00

As near as I can tell, the only TransferEncoding schemes allowed are here: https://learn.microsoft.com/en-us/dotnet/api/system.net.mime.transferencoding?view=net-7.0

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Rich Matheisen 47,901 Reputation points

2023-03-01T20:10:49.26+00:00

I think "Windows Server PowerShell" isn't the best place to ask for advice like this. The "base64" part of the "img" tag's "src" identifies a "user agent". In the situation you're asking about that's how the web browser discovers how to deal with the decoding. If you choose another encoding format you'd have to be sure that the user agent was available on all the client machines that receive your email, and that all the web browsers used on those machines had a version of that user agent, too.

A better way is to place the image on a web server and provide an "alt" tag describing the image for those that, perhaps, have either no access to the web server (e.g. it's not accessible outside your LAN), are visually impaired, etc.
DaveK 1,871 Reputation points

2023-03-02T11:09:03.87+00:00

Hi, Sorry I should have been clearer on how the Base64 string is used. The image is inserted as an inline PNG image decoded as part of script using a steam and creating the image using LinkedResource(Stream, ContentType) so it isn't used directly in the img tag - I've tried that in the past and had all kind of issues with clients as you mention.

I was wondering more if there are any other methods to 'embed' the image into my script for use in the same manor but hopefully without it triggering the same AV false positive the Base64 data does. I've other scripts which use the same method which don't produce the false positive so I'm thinking its more

It was a little bit of a long short using the Windows Server PowerShell tag I'll admit but I'm aware there are some experienced minds here so was worth a go :)
Rich Matheisen 47,901 Reputation points

2023-03-02T20:13:47.8433333+00:00

As near as I can tell, the only TransferEncoding schemes allowed are here: https://learn.microsoft.com/en-us/dotnet/api/system.net.mime.transferencoding?view=net-7.0

Answer 1

Aung Zaw Min Thwin 306

pls refer to below sample: Hope that helps :)

$Path = c:\temp\abc.jpg
$path = (Get-Item $Path).FullName
$ByteArr = [io.file]::ReadAllBytes($Path)

$LineLength = 80
$base64Str = [Convert]::ToBase64String($ByteArr) -replace ".{$LineLength}" , "$&`r`n"

#to convert from base64:
#$ByteArr1 = [convert]::FromBase64String($base64Str)

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Alternatives to storing image data in script as Base64 string?

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