Power BI REST API via Powershell: Create Datasource

The credentials from credentialDetails need to be encripted unsing RSA algorithm before calling the api. I've used an alghorthim posted in https://community.powerbi.com/t5/Developer/How-do-I-update-the-Credentials-after-I-upload-a-report-to-POWER/td-p/223243 and converted it to powershell. The algorithm from https://docs.microsoft.com/en-us/power-bi/developer/encrypt-credentials is also good. Also the server name needs to have double the amount of "\" charahters to work.

function CreateDatasourceForGateway([guid]$GatewayId, 
                                    [string]$DatasourceName, 
                                    [string]$TenantServer, 
                                    [string]$TenantDatabase,
                                    [string]$TenantDataSourceUser,
                                    [string]$TenantDataSourcePassword) {   

    $gateway = Invoke-PowerBIRestMethod `
                -Url "https://api.powerbi.com/v1.0/myorg/gateways/$GatewayId" `
                -Method GET ` | ConvertFrom-Json                

    $datasourceDetails = ConvertTo-Json -Depth 4 -InputObject $(@{
        dataSourceType = "Sql"
        connectionDetails = '{"server":"'+$TenantServer.Replace("\","\\")+'","database":"'+$TenantDatabase+'"}'
        datasourceName = $DatasourceName
        credentialDetails = @{
            credentialType = "Basic"
            credentials = Encript `
                            -Username $TenantDataSourceUser `
                            -Password $TenantDataSourcePassword `
                            -GatewayExponent $gateway.publicKey.exponent `
                            -GatewayModulus $gateway.publicKey.modulus
            encryptedConnection = "Encrypted"
            encryptionAlgorithm = "RSA-OAEP"
            privacyLevel = "None"
        }
    })

    $result = Invoke-PowerBIRestMethod `
            -Url "https://api.powerbi.com/v1.0/myorg/gateways/$GatewayId/datasources" `
            -Method POST `
            -Body $datasourceDetails
}

function Encript([string]$Username,[string]$Password,[string]$GatewayExponent,[string]$GatewayModulus) {
    $segmentLength = 85
    $encryptedLength = 128
    $plaintTxt = '{"credentialData":[{"value":"'+$Username+'","name":"username"},{"value":"'+$Password+'","name":"password"}]}'
    $rsa = New-Object System.Security.Cryptography.RSACryptoServiceProvider ($encryptedLength * 8)
    $parameters = $rsa.ExportParameters($false)
    $parameters.Exponent = [System.Convert]::FromBase64String($GatewayExponent)
    $parameters.Modulus = [System.Convert]::FromBase64String($GatewayModulus)
    $rsa.ImportParameters($parameters)
    $plainTextArray = [System.Text.Encoding]::UTF8.GetBytes($plaintTxt)    
    $hasIncompleteSegment = $plainTextArray.Length % $segmentLength -ne 0

    $segmentNumber = If (-not $hasIncompleteSegment) {[int]($plainTextArray.Length / $segmentLength)} Else {[int]($plainTextArray.Length / $segmentLength) + 1}
    $encryptedData = [System.Byte[]]::CreateInstance([System.Byte],$segmentNumber * $encryptedLength)
    [int]$encryptedDataPosition = 0;

    For ($i=0; $i -lt $segmentNumber; $i++) {
        $lengthToCopy = If ($i -eq ($segmentNumber - 1) -and $hasIncompleteSegment) {$plainTextArray.Length % $segmentLength} Else {$segmentLength}
        $segment = [System.Byte[]]::CreateInstance([System.Byte],$lengthToCopy)
        [System.Array]::Copy($plainTextArray,$i*$segmentLength,$segment,0,$lengthToCopy)
        $segmentEncryptedResult = $rsa.Encrypt($segment, $true)
        [System.Array]::Copy($segmentEncryptedResult,0,$encryptedData,$encryptedDataPosition,$segmentEncryptedResult.Length)
        $encryptedDataPosition += $segmentEncryptedResult.Length;
    }

    return [System.Convert]::ToBase64String($encryptedData)
}

Connect-PowerBIServiceAccount

CreateDatasourceForGateway `
    -GatewayId $GatewayId `
    -DatasourceName "$TenantReportPrefix Datasource"`
    -TenantServer $TenantServer `
    -TenantDatabase $TenantDatabase `
    -TenantDataSourceUser $TenantDataSourceUser `
    -TenantDataSourcePassword $TenantDataSourcePassword

Hi, i know this is an old post... did you ever get it resolved?

I'm facing the exact same issue and have been begging for help, but no success...