Add Get-SecureRandom cmdlet

[SteveL-MSFT]

PR Summary

Add a Get-SecureRandom cmdlet which does not expose a -SetSeed parameter ensuring results are always cryptographically secure. Get-Random is derived from this cmdlet and maintains the -SetSeed parameter. The only changes to the move of code from GetRandomCommand is changing some members to internal from private so that Get-Random can call them.

The tests are a copy of the Get-Random tests removing the -SetSeed tests and adding a specific test to ensure that parameter doesn't exist.

PR Context

Users of Get-Random who use -SetSeed may mistakenly think they are cryptographically secure but is not since a seed is used. This new cmdlet makes it easy to not make this mistake.

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  • Documentation needed
    • Issue filed: New Get-SecureRandom cmdlet MicrosoftDocs/PowerShell-Docs#10041
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[iSazonov]

Is "Secure" right term if "strong crypto" is assumed? Maybe "Get-StrongRandom".

[MartinGC94]

Why not just emit a warning if the SetSeed parameter is used? If a new Get-SecureRandom command is added people will probably assume that Get-Random is insecure, when in reality it's only insecure in specific circumstances.

[SteveL-MSFT]

@MartinGC94 I considered adding a warning when -SetSeed is used, but when used in automation, no one will likely see the warning. You're correct that the default usage of Get-Random is secure, but the intent here is to make it more clear. Get-Random will continue to work as it does today so this is really for newer users.

@iSazonov I chose Get-SecureRandom primarily to match the naming of the *-SecureString cmdlets even though there is no relation functionally between the two. Strong or Crypto would only be meaningful to someone who already understands the implications of -SetSeed and the name is really for those who may not.

[PaulHigin]

LGTM

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This PR has 720 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

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Label      : Extra Large
Size       : +434 -286
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Total files changed: 7

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.cs : +295 -284
.psd1 : +2 -2
.ps1 : +137 -0

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🎉v7.4.0-preview.4 has been released which incorporates this pull request.:tada:

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