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I have a really simple question which I am sure someone can answer really quickly for me.

I have one text file (password.txt) containing a random string of characters which has been generated by a Poweshell script to be used as a wifi password.

I have another script (change-password.ps1) which logs into my router and changes the password. I have managed to get this script to look at a json file (config.json) and use one of static passphrases.

This is my json file

{ "PSKs": {
            "01":"PSKforJanuary123!!",
            "02":"PSKforFebruary123!",
            "03":"PSKforMarch123!",
            "04":"PSKforApril123!",
            "05":"PSKforMay123!",
            "06":"PSKforJune123!",
            "07":"PSKforJuly123!",
            "08":"PSKforAugust123!",
            "09":"PSKforSeptember123!",
            "10":"PSKforOctober123!",
            "11":"PSKforNovember123!",
            "12":"PSKforDecember123!"
        }
    }

So instead of using one of these from the list above, how can I replace the "PSKfor***123!" with the line of text from my password.txt?

Or is there a way I can create this random string of characters within my json file without having to run another script to generate it?

Thanks in advance!

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  • 2
    "how can I replace the "PSKfor***123!" with the line of text from my password.txt?" replace where? your question is not clear. Commented Dec 11, 2024 at 16:45
  • @TangentiallyPerpendicular it was indeed a typo, I have corrected it now Commented Dec 11, 2024 at 16:50
  • @SantiagoSquarzon Where it says "PSKformonth123" in my json file, I am trying to replace it with a random string to use as a password. Commented Dec 11, 2024 at 16:52
  • Which one of the PSKformonth123 ? The one that corresponds with the current month (i.e.: 12 in this case) ? These clarifications should be in your question Commented Dec 11, 2024 at 16:57
  • @SantiagoSquarzon Sorry, all of them. I want to replace all of them with the same single password or just one line which doesn't specify a month. Once i have this worming I am going to run the script once a month so it generates a new one without having to check what month it is. It will change it every month regardless. Commented Dec 11, 2024 at 17:12

2 Answers 2

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How to update all properties in the Json using a password stored in a file:

$json = Get-Content path\to\json.txt -Raw | ConvertFrom-Json
$pass = Get-Content path\to\password.txt
$json.PSKs.PSObject.Properties | ForEach-Object { $_.Value = $pass }
$json | ConvertTo-Json | Set-Content path\to\json.txt

How to update a single property in the Json using a password stored in a file, say for example, to dynamically update the property that corresponds with the current month:

$json = Get-Content path\to\json.txt -Raw | ConvertFrom-Json
$pass = Get-Content path\to\password.txt
$month = [datetime]::Now.ToString('MM')
# `$json.PSKs.$month` would work too here
$json.PSKs.PSObject.Properties[$month].Value = $pass
$json | ConvertTo-Json | Set-Content path\to\json.txt

How to update all properties using a randomly generated password, for this you will need to figure out what logic you want to use to generate a random password. A very easy way is via RandomNumberGenerator.GetString(ReadOnlySpan<Char>, Int32) Method but this method only works in PowerShell 7.

# `$chars` can be whatever you like, this is just an example
$chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!@#$%&_-+='.ToCharArray()
$json = Get-Content path\to\json.txt -Raw | ConvertFrom-Json
$json.PSKs.PSObject.Properties | ForEach-Object {
    # `20` is for the string length
    $_.Value = [System.Security.Cryptography.RandomNumberGenerator]::GetString($chars, 20)
}
$json | ConvertTo-Json | Set-Content path\to\json.txt
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3 Comments

Thats awesome! Thank you so much, this fixed my problem! I finally went with this: ''$json = Get-Content $PSScriptRoot\config.json -Raw | ConvertFrom-Json $pass = Get-Content $PSScriptRoot\luxion-guests.txt $month = [datetime]::Now.ToString('MM') # $json.PSKs.$month would work too here $json.PSKs.PSObject.Properties[$month].Value = $pass $json | ConvertTo-Json | Set-Content $PSScriptRoot\config.json''
Sorry I cannot get the hang of formatting on here :(
np glad it helped @Beckyboo
0

NOTE: my solutions require Powershell 7.x

Given you know the key, replacing all the values it's easy

$JsonHashTable = Get-Content -Path $JsonFile | ConvertFrom-Json -AsHashtable -Depth 100
$PasswordString = Get-Content -Path $PasswordFile

# .Clone() necessary because otherwise the Keys list gets refreshed
# at every change and that causes a error.   
foreach ($Key in $JsonHashTable.PSKs.Keys.Clone()) {      
    $JsonHashTable.PSKs.$Key = $PasswordString 
}

$JsonHashTable | ConvertTo-Json -Depth 100 | Set-Content -Path $JsonFile

To change one specific month:

while ($MonthToChange -notin 1..12) {
    # Evaluate some error handling   
    [int]$MonthToChange = Read-Host -Prompt 'Insert number of the month to change [0-12]'
}

$MonthKey = '{0:d2}' -f $MonthToChange

$JsonHashTable.PSKs.$MonthKey=$PasswordString

To dynamically generate a random string to use as password, given the apparent low-risk environment(you will have those passwords store in plain text after all) I'd suggest using

$PasswordString = New-Guid | Select-Object -ExpandProperty Guid

Depending on the real use situation, evaluate implementing some random string generator module.

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1 Comment

Thanks for the response @sirtao, I have gone with the response above for now but I may come back to this at a later date.

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