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Many administrators encounter this puzzling behavior when working with RDP files. Despite including credentials in the connection file, Windows Remote Desktop still prompts for authentication. Here's what's happening under the hood and how to properly configure password persistence.

For password embedding to work, your RDP file needs these specific elements:

full address:s:10.20.30.40
username:s:myuser
password 51:b:01000000D08C9DDF0115D1118C7A00C04FC297EB...
enablecredsspsupport:i:1

You can't simply store plaintext passwords in RDP files. Windows requires encrypted credentials using the Data Protection API (DPAPI). Here are three methods to properly embed credentials:

# PowerShell method
cmdkey /generic:TERMSRV/10.20.30.40 /user:myuser /pass:mypassword
mstsc /edit connection.rdp

# C# DPAPI example (for automation)
byte[] encrypted = ProtectedData.Protect(
    Encoding.Unicode.GetBytes("mypassword"),
    null,
    DataProtectionScope.CurrentUser);

# Command-line alternative
(Get-Content connection.rdp) -replace "^password .*",
    "password 51:b:$(ConvertTo-SecureString 'mypassword' -AsPlainText -Force | 
    ConvertFrom-SecureString)" | Set-Content connection.rdp

Remember these important security aspects when working with RDP credentials:

• Encrypted passwords are user-specific - won't work if shared between machines
• Never store raw passwords in version control or unsecured locations
• Consider using certificate-based authentication for better security
• Group Policy may override your credential settings (check 'Always prompt for password')

If properly configured credentials still don't work:

1. Verify no Group Policy is enforcing credential prompts (gpedit.msc)
2. Check for special characters in credentials that might need escaping
3. Ensure the RDP file isn't marked as read-only
4. Test with a newly generated RDP file from mstsc.exe

For environments where DPAPI isn't suitable, consider this PowerShell wrapper:

param($server, $user, $password)

$rdpFile = [System.IO.Path]::GetTempFileName() + ".rdp"
$secureString = ConvertTo-SecureString $password -AsPlainText -Force
$credential = New-Object System.Management.Automation.PSCredential($user, $secureString)

@"
full address:s:$server
username:s:$($credential.UserName)
password 51:b:$([Runtime.InteropServices.Marshal]::PtrToStringAuto(
    [Runtime.InteropServices.Marshal]::SecureStringToBSTR($credential.Password)))
"@ | Out-File $rdpFile -Encoding ASCII

mstsc $rdpFile
Start-Sleep -Seconds 5
Remove-Item $rdpFile

When working with Remote Desktop Protocol (RDP) files, you might encounter a situation where the client keeps prompting for credentials despite having specified them in the file. Here's a deep dive into why this happens and how to properly configure authentication.

The standard RDP file format allows storing credentials, but modern security policies often prevent automatic authentication. The key parameters are:

full address:s:10.20.30.40
username:s:myuser
password 51:b:mypassword_encrypted
domain:s:mydomain

For automatic authentication to work, you need both the correct file format and proper system policies:

1. Password encryption: Plain text passwords won't work - you need to use the encrypted format
2. Group Policy settings: The client machine must allow credential storage
3. File permissions: The RDP file must have restricted access permissions

Here's how to properly create an authenticated RDP file:

1. Generate Encrypted Password

Use PowerShell to create the encrypted password string:

$password = "mypassword"
$bytes = [System.Text.Encoding]::Unicode.GetBytes($password)
$encrypted = [System.Convert]::ToBase64String($bytes)
Write-Host "password 51:b:$encrypted"

2. Create Complete RDP File

screen mode id:i:2
use multimon:i:0
desktopwidth:i:1920
desktopheight:i:1080
session bpp:i:32
winposstr:s:0,1,0,0,800,600
full address:s:10.20.30.40
compression:i:1
keyboardhook:i:2
audiomode:i:0
redirectprinters:i:1
redirectcomports:i:0
redirectsmartcards:i:1
redirectclipboard:i:1
redirectposdevices:i:0
autoreconnection enabled:i:1
authentication level:i:0
username:s:myuser
password 51:b:UABhAHMAcwB3AG8AcgBkAA==
domain:s:mydomain
alternate shell:s:
shell working directory:s:
disable wallpaper:i:1
disable full window drag:i:1
disable menu anims:i:1
disable themes:i:0
disable cursor setting:i:0
bitmapcachepersistenable:i:1

Before implementing this solution, consider these security implications:

• Store RDP files in secure locations with restricted permissions
• Regularly rotate credentials
• Consider using certificate-based authentication instead
• Implement Network Level Authentication (NLA)

If issues persist:

1. Verify Group Policy settings (gpedit.msc) under:
   
   Computer Configuration → Administrative Templates → Windows Components → Remote Desktop Services → Remote Desktop Connection Client
2. Check credential delegation settings
3. Test with different encryption types