PowerShell's Invoke-RestMethod equivalent of curl -u (Basic Authentication)

I'm not sure why the -Credential parameter isn't working in your case, but it works with the httpbin service.

You can try this:

$pwd = ConvertTo-SecureString "MyPassword" -AsPlainText -Force
$cred = New-Object Management.Automation.PSCredential ('PsUser', $pwd)

Invoke-RestMethod 'http://httpbin.org/basic-auth/PsUser/MyPassword' -cred $cred

Edit: As noted in the comments, this method will not send the Authorization header on the initial request. It waits for a challenge response then re-sends the request with the Authorization header. This will not work for services that require credentials on the initial request.

#Requires -Version 6
$Uri = 'https://httpbin.org/basic-auth/user/pass'
# use "user" and "pass" when prompted for credentials
$Credential = Get-Credential
Invoke-RestMethod -Uri $Uri -Authentication Basic -Credential $Credential

It appears you should combine methods when they fail independently.

Create the credential and add it to the request.

Create the header and add it to the request.

$username = "username";
$password = ConvertTo-SecureString –String "password" –AsPlainText -Force
$credential = New-Object –TypeName "System.Management.Automation.PSCredential" –ArgumentList $username, $password

$base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f $username,$password)))

$getProjectUri = "yourUri"
Invoke-RestMethod -Method Get -Uri $getProjectUri -Headers @{Authorization = "Basic $base64AuthInfo" } -Credential $credential -ContentType "application/json"

This version works with Get-Credential's PSCredential object. It also works cross-platform in PowerShell 6.0. It does this by avoiding use of BSTR calls, which are sometimes suggested when attempting to extract the password from PSCredential.

$creds = Get-Credential
$unsecureCreds = $creds.GetNetworkCredential()
$base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f $unsecureCreds.UserName,$unsecureCreds.Password)))
Remove-Variable unsecureCreds

Invoke-RestMethod -Headers @{Authorization=("Basic {0}" -f $base64AuthInfo)} ...

You basically need to pass the username and password pair to Invoke-RestMethod as an encoded credentials variable.

What worked for me was the following:

$USERNAME = 'user'
$PASSWORD = 'password'
$IDP_URL = 'example.com/token'


$credPair = "$($USERNAME):$($PASSWORD)"
$encodedCredentials = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes($credPair))

$parameters = @{
    Uri         = $IDP_URL
    Headers     = @{ 'Authorization' = "Basic $encodedCredentials" }
    Method      = 'POST'
    Body        = '...'
    ContentType = '...'
}

Invoke-RestMethod @parameters

Note how you can extract the request parameters into $parameters to avoid bloating your command.

I've found that using the -WebSession parameter works, if you pre-create a WebRequestSession object with credentials. I won't rehash how to create a PS Credential object, as that's already been covered in other answers.

$WebSession = New-Object -TypeName Microsoft.PowerShell.Commands.WebRequestSession -Property @{Credentials=$Credential}
Invoke-RestMethod -Uri "your_URI" -WebSession $WebSession

This approach sends the auth header on the first call, so avoids the 401 response.

Incidentally, this approach can also be used to set proxy details (which don't work properly in all versions of PS when specified using the parameters), and handles cookies if your API requires that.

I know this is a really old question, but I wanted to share an update somewhere. None of the posts I was finding for Basic Auth with PowerShell were working for me. After much trial-and-error and reading through the MS Docs I found that I needed to use the -AllowUnencryptedAuthentication parameter because I was connecting using http. I also had to upgrade my PS version to get access to the parameter.

From the description of the parameter: "Allows sending of credentials and secrets over unencrypted connections. By default, supplying Credential or any Authentication option with a Uri that does not begin with https:// will result in an error and the request will abort to prevent unintentionally communicating secrets in plain text over unencrypted connections. To override this behavior at your own risk, supply the AllowUnencryptedAuthentication parameter."

I spent a few days having no luck with any of the above examples. Eventually I worked out I needed to specify the Method of Post. e.g.:

$request =  Invoke-WebRequest -Method Post -Uri "https://www.emea-api.morningstar.com/token/oauth" -Headers @{accept='*/*';Authorization='Basic bWFy...encoded username:password...='};

-mobailey