PowerShell 6 Core Support (#35)

## About
This pull request reflects all changes done in the `linuxsupport` branch.

## Content
- Enable PowerShell 6 Core support
- Use PFX Certificate for encryption ( fixes #32 )
- Updates CI / CD pipeline ( fixes #31 )
- uses portable libressl ( fixes #34 )
- adds `-PassThru` switch for returning current `VIServer` session in `Connect-To` ( fixes #34 )
- adds git lfs for embedded libressl files
- restructured internal functions into `Private` dir
- added certificate related functions
- adds travis build pipeline for tests

src/Private/Get-DefaultCredentialStorePath.ps1

@@ -0,0 +1,61 @@
+function Get-DefaultCredentialStorePath {
+    <#
+    .SYNOPSIS
+        Returns the default CredentialStore path based on the current OS.
+
+    .DESCRIPTION
+        This is a low level helper function.
+
+    .INPUTS
+        [None]
+
+    .OUTPUTS
+        [string]
+
+    .EXAMPLE
+        $Path = Get-DefaultCredentialStorePath
+
+    .NOTES
+        File Name   : Get-DefaultCredentialStorePath.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+    #>
+    [CmdletBinding()]
+    [OutputType([string])]
+    param(
+        [Parameter(Mandatory = $false)]
+        [switch]$Shared
+    )
+
+    begin {}
+
+    process {
+        if ($Shared.IsPresent) {
+            if ($IsLinux) {
+                return Join-Path -Path '/var/opt' -ChildPath 'PSCredentialStore/CredentialStore.json'
+            }
+            if ($IsMacOS) {
+                return Join-Path -Path '/var/opt' -ChildPath 'PSCredentialStore/CredentialStore.json'
+            }
+            elseif (($isWindows) -or ($PSVersionTable.PSVersion.Major -lt 6) -or ($PSVersionTable.PSEdition -eq 'Desktop')) {
+                return Join-Path -Path $env:ProgramData -ChildPath 'PSCredentialStore/CredentialStore.json'
+            }
+        }
+        else {
+            if ($IsLinux) {
+                return Join-Path -Path $Env:HOME -ChildPath 'CredentialStore.json'
+            }
+            if ($IsMacOS) {
+                return Join-Path -Path $Env:HOME -ChildPath 'CredentialStore.json'
+            }
+            elseif (($isWindows) -or ($PSVersionTable.PSVersion.Major -lt 6) -or ($PSVersionTable.PSEdition -eq 'Desktop')) {
+                return Join-Path -Path $env:AppData -ChildPath 'CredentialStore.json'
+            }
+        }
+    }
+
+    end {}
+}

src/Private/Get-ModuleBase.ps1

@@ -0,0 +1,29 @@
+function Get-ModuleBase {
+    <#
+    .SYNOPSIS
+        Returns the base path of the current module.
+
+    .DESCRIPTION
+        This is just a wrapper for enabling pester tests.
+
+
+    .OUTPUTS
+        Returns the base path as string
+
+    .NOTES
+        File Name   : Get-ModuleBase.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+#>
+    [CmdletBinding()]
+    [OutputType()]
+    param()
+    begin {}
+    process {
+        return $MyInvocation.MyCommand.Module.ModuleBase
+    }
+    end {}
+}

src/Private/Get-RandomAESKey.ps1

@@ -0,0 +1,44 @@
+function Get-RandomAESKey {
+    <#
+    .SYNOPSIS
+        Generate a new 32-byte AES key.
+
+    .DESCRIPTION
+        Uses the System.Security.Cryptography namespace for random aes key generation.
+
+    .INPUTS
+        [None]
+
+    .OUTPUTS
+        [byte[]]
+
+    .EXAMPLE
+        .\Get-RandomAESKey
+
+    .NOTES
+        File Name   : Get-RandomAESKey.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+    #>
+
+    [CmdletBinding()]
+    [OutputType([byte[]])]
+    param()
+
+    begin {}
+
+    process {
+        $key = [byte[]]::new(32)
+        $rng = [System.Security.Cryptography.RNGCryptoServiceProvider]::Create()
+        $rng.GetBytes($key)
+        Write-Output $key
+        if ($null -ne $key) {
+            [array]::Clear($key, 0, $key.Length)
+        }
+
+    }
+    end {}
+}

src/Private/Get-TempDir.ps1

@@ -0,0 +1,44 @@
+function Get-TempDir {
+    <#
+    .SYNOPSIS
+        Returns the valid temp dir of the current OS
+
+    .DESCRIPTION
+        Returns the valid temp dir of the current OS.
+
+    .INPUTS
+        [None]
+    .OUTPUTS
+        [string]
+
+    .EXAMPLE
+        Get-TempDir
+
+    .NOTES
+        File Name   : Get-TempDir.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+    #>
+    [CmdletBinding()]
+    [OutputType([string])]
+    param()
+    begin {
+
+    }
+    process {
+        if ($IsLinux) {
+            return (Resolve-Path -Path '/tmp/').Path
+        }
+        if ($IsMacOS) {
+            return (Resolve-Path -Path '/tmp/').Path
+        }
+        elseif (($isWindows) -or ($PSVersionTable.PSVersion.Major -lt 6) -or ($PSVersionTable.PSEdition -eq 'Desktop')) {
+            return (Resolve-Path -Path $env:TEMP).Path
+        }
+    }
+    end {
+    }
+}

src/Private/Resolve-Dependency.ps1

@@ -0,0 +1,88 @@
+function Resolve-Dependency {
+    <#
+    .SYNOPSIS
+        Tests defined optional dependencies and returns the result as bool.
+
+    .DESCRIPTION
+        Use this function to test for optional modules. You can use it if you provide functions which needs special
+        modules but you don't want to make them required.
+
+        Place a file called Dependency.json in your module root dir. The default format is:
+
+        {
+            "Version": 0.1,
+            "Mandatory": {},
+            "Optional": [
+                {
+                    "Name": "VMware",
+                    "Modules": [
+                        "VMware.VimAutomation.Core"
+                    ]
+                },
+                {
+                    "Name": "CiscoUCS",
+                    "Modules": []
+                }
+            ]
+        }
+
+    .PARAMETER Name
+        Select the dependency item name you defined in the dependency.json.
+    .INPUTS
+        [None]
+
+    .OUTPUTS
+        [bool]
+
+    .EXAMPLE
+        If (-not (Resolve-Dependency -Name 'VMware')) {
+            Write-Error -Message ("Could not resolve the optional dependencies defined for {0}" -f 'VMware') -ErrorAction 'Stop'
+        }
+
+    .NOTES
+        ```
+        File Name   : ResolveDependency.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+        ```
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+    #>
+    [OutputType([bool])]
+    [CmdletBinding()]
+    param (
+        [Parameter(Mandatory = $true)]
+        [ValidateNotNullOrEmpty()]
+        [string]$Name
+    )
+
+    begin {
+        $ModuleRootDir = Get-ModuleBase
+        $DepFilePath = Join-Path -Path $ModuleRootDir -ChildPath "Dependency.json"
+        if (Test-Path -Path $DepFilePath) {
+            $Dependency = Get-Content -Path $DepFilePath -Raw -Encoding UTF8 | ConvertFrom-Json
+        }
+        else {
+            Write-Warning ("Could not find the dependency file: {0}" -f $DepFilePath)
+        }
+    }
+
+    process {
+        $SelectedDependency = $Dependency.Optional | Where-Object {$_.Name -match $Name}
+        $res = @()
+        foreach ($Module in $SelectedDependency.Modules) {
+            $res += Test-Module -Name $Module
+        }
+        # return false if there was not module at all
+        if (($res -contains $false) -or ($res.Count -eq 0)) {
+            return $false
+        }
+        else {
+            return $true
+        }
+    }
+
+    end {
+    }
+}

src/Private/Test-Module.ps1

@@ -0,0 +1,79 @@
+function Test-Module {
+    <#
+    .SYNOPSIS
+        Tests if the given module exists on the local system.
+
+    .DESCRIPTION
+        Tests if the given module is installed on the local system. It returns a bool value as result.
+
+    .PARAMETER Name
+        Define a item name you need to test
+
+    .PARAMETER Type
+        Define the dependency type. This could be a Module or PSnapin.
+
+    .PARAMETER MessagePattern
+        You an optionally adjust the message pattern for the error message itself.
+        The available placeholders are:
+        - {0} : Type
+        - {1} : Name
+
+    .PARAMETER StopIfFails
+        This switch forces the entire script to stop if the given dependency object fails.
+
+    .INPUTS
+        [None]
+
+    .OUTPUTS
+        [Bool]
+
+    .EXAMPLE
+        .\Test-Dependency -Name 'VMware.PowerCLI' -Type 'Module'
+
+    .EXAMPLE
+        .\Test-Dependency -Name 'VMware.PowerCLI' -Type 'Module' -StopIfFails
+
+    .NOTES
+        ```
+        File Name   : Test-Module.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+        ```
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+    #>
+    [OutputType([bool])]
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true)]
+        [ValidateNotNullOrEmpty()]
+        [string]$Name,
+
+        [Parameter(Mandatory = $false)]
+        [ValidateNotNullOrEmpty()]
+        [string]$MessagePattern = @"
+Could not find the required {0} called {1}. Please install the required {0} to run this function!
+"@,
+        [Parameter(Mandatory = $false)]
+        [switch]$StopIfFails
+    )
+    begin {}
+
+    process {
+        $Message = $MessagePattern -f $Type, $Name
+        Write-Debug $Message
+
+        if (Get-Module -Name $Name -ListAvailable) {
+            return $true
+        }
+        else {
+            if ($StopIfFails) {
+                Write-Error -Message $Message -ErrorAction Stop -Category NotInstalled
+            }
+            return $false
+        }
+    }
+
+    end {}
+}