Implementing Zero Trust For SaaS Applications

# Implementing Zero Trust for SaaS Applications

## When to Use

- When securing access to SaaS applications (Microsoft 365, Google Workspace, Salesforce, Slack)
- When implementing conditional access policies requiring MFA and device compliance for SaaS
- When deploying CASB for shadow IT discovery and unsanctioned app blocking
- When enforcing session-level controls (DLP, download restrictions) for sensitive SaaS data
- When governing OAuth application permissions and detecting excessive consent grants

**Do not use** as a replacement for SaaS-native security controls (configure those first), for applications with no SAML/OIDC support, or when SaaS vendor does not support API integration for CASB/SSPM.

## Prerequisites

- Identity provider with conditional access: Microsoft Entra ID P1/P2, Okta
- CASB solution: Microsoft Defender for Cloud Apps, Netskope, or Zscaler CASB
- SaaS applications configured with SSO via SAML 2.0 or OIDC
- MDM enrollment for device compliance signals (Intune, Jamf)
- DLP policies defined for sensitive data categories

## Workflow

### Step 1: Federate SaaS Authentication Through Identity Provider

Centralize authentication for all SaaS applications through a single IdP.

```powershell
# Configure SAML SSO for Salesforce via Entra ID
Connect-MgGraph -Scopes "Application.ReadWrite.All"

# Create enterprise application for Salesforce
$app = New-MgServicePrincipal -AppId "SALESFORCE_APP_ID" -DisplayName "Salesforce"

# Configure SAML SSO settings
$samlSettings = @{
    preferredSingleSignOnMode = "saml"
    samlSingleSignOnSettings = @{
        relayState = ""
    }
}
Update-MgServicePrincipal -ServicePrincipalId $app.Id -BodyParameter $samlSettings

# Assign user groups to the application
New-MgServicePrincipalAppRoleAssignment -ServicePrincipalId $app.Id -BodyParameter @{
    principalId = "SALES_GROUP_ID"
    resourceId = $app.Id
    appRoleId = "DEFAULT_ROLE_ID"
}
```