Convert a secure string to plain text

Question

I'm working in PowerShell and I have code that successfully converts a user entered password into plain text:

$SecurePassword = Read-Host -AsSecureString  "Enter password" | convertfrom-securestring | out-file C:\Users\tmarsh\Documents\securePassword.txt 

I've been tried several ways to convert it back, but none of them seem to work properly. Most recently, I've tried with the following:

$PlainPassword = Get-Content C:\Users\tmarsh\Documents\securePassword.txt  #convert the SecureString object to plain text using PtrToString and SecureStringToBSTR $BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($PlainPassword) $PlainPassword = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR) [Runtime.InteropServices.Marshal]::ZeroFreeBSTR($BSTR) #this is an important step to keep things secure 

This gives me an error as well.

Cannot convert argument "s", with value: "01000000d08c9ddf0115d1118c7a00c04fc297eb0100000026a5b6067d53fd43801a9ef3f8ef9e43000000000200000000000366000 0c0000000100000008118fdea02bfb57d0dda41f9748a05f10000000004800000a000000010000000c50f5093f3b87fbf9ee57cbd17267e0a10000000833d1d712cef01497872a3457bc8 bc271400000038c731cb8c47219399e4265515e9569438d8e8ed", for "SecureStringToBSTR" to type "System.Security.SecureString": "Cannot convert the "01000000 d08c9ddf0115d1118c7a00c04fc297eb0100000026a5b6067d53fd43801a9ef3f8ef9e430000000002000000000003660000c0000000100000008118fdea02bfb57d0dda41f9748a05f10 000000004800000a000000010000000c50f5093f3b87fbf9ee57cbd17267e0a10000000833d1d712cef01497872a3457bc8bc271400000038c731cb8c47219399e4265515e9569438d8e8 ed" value of type "System.String" to type "System.Security.SecureString"." At C:\Users\tmarsh\Documents\Scripts\Local Admin Script\PlainTextConverter1.ps1:14 char:1 + $BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($PlainPassw ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     + CategoryInfo          : NotSpecified: (:) [], MethodException     + FullyQualifiedErrorId : MethodArgumentConversionInvalidCastArgument  Cannot find an overload for "PtrToStringAuto" and the argument count: "1". At C:\Users\tmarsh\Documents\Scripts\Local Admin Script\PlainTextConverter1.ps1:15 char:1 + $PlainPassword = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     + CategoryInfo          : NotSpecified: (:) [], MethodException     + FullyQualifiedErrorId : MethodCountCouldNotFindBest  Cannot convert argument "s", with value: "", for "ZeroFreeBSTR" to type "System.IntPtr": "Cannot convert null to type "System.IntPtr"." At C:\Users\tmarsh\Documents\Scripts\Local Admin Script\PlainTextConverter1.ps1:16 char:1 + [Runtime.InteropServices.Marshal]::ZeroFreeBSTR($BSTR) #this is an important ste ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     + CategoryInfo          : NotSpecified: (:) [], MethodException     + FullyQualifiedErrorId : MethodArgumentConversionInvalidCastArgument  Password is:  01000000d08c9ddf0115d1118c7a00c04fc297eb0100000026a5b6067d53fd43801a9ef3f8ef9e430000000002000000000003660000c0000000100000008118fdea02bfb57d0dda41f97 48a05f10000000004800000a000000010000000c50f5093f3b87fbf9ee57cbd17267e0a10000000833d1d712cef01497872a3457bc8bc271400000038c731cb8c47219399e4265515e9569 438d8e8ed 

Does anyone know of a way that will work for this?

Answer 1

You are close, but the parameter you pass to SecureStringToBSTR must be a SecureString. You appear to be passing the result of ConvertFrom-SecureString, which is an encrypted standard string. So call ConvertTo-SecureString on this before passing to SecureStringToBSTR.

$SecurePassword = ConvertTo-SecureString $PlainPassword -AsPlainText -Force $BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($SecurePassword) $UnsecurePassword = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR)