powershell - Powershell：使用“System.Security.SecureString”时，Invoke-RestMethod 给了我“错误请求”

Question

这是我的代码：

$appliance = Read-Host "OneView Address"
$userName = Read-Host "Username"
$password = Read-Host "Password" -AsSecureString

$url = "https://$appliance"

$user = @{
    userName= "$($userName)"
    password= "$($password)"
    authnHost= "$appliance"
    authLoginDomain= "Local"
}

$json = $user | ConvertTo-Json 

$headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headers.Add("Content-type", 'application/json')
$headers.Add("Accept", 'application/json')
$uri = $url + '/rest/login-sessions'
$response = Invoke-RestMethod -Uri $uri -Method POST -Headers $headers -Body $json -ContentType 'application/json'

当我运行它时，我收到以下错误：

Invoke-RestMethod : The remote server returned an error: (400) Bad Request.
At C:\myscript.ps1:54 char:13
+ $response = Invoke-RestMethod -Uri $uri -Method POST -Headers $header ...
+             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand

当我不使用参数“-AsSecureString”读取密码时，它可以工作。

有人可以告诉我这里有什么问题吗？

提前致谢。