OAuth vs SSO
🔹 1. OAuth (Open Authorization)
Section titled “🔹 1. OAuth (Open Authorization)”- OAuth is an authorization protocol that allows one app to access resources (like data or APIs) from another app on behalf of the user, without sharing credentials.
⚙️ How it works (OAuth 2.0 flow – simplified):
Section titled “⚙️ How it works (OAuth 2.0 flow – simplified):”-
- User clicks Login with Google on your app.
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- Your app will redirect user to Google’s OAuth server.
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- User logs into Google and give consent (e.g., “allow access to email”).
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- Google sends an authorization code back to your app.
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- Your app exchange the code for an access token.
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- Your app uses the access token to call Google API’s (e.g., fetch user profile).
✅ Pros:
Section titled “✅ Pros:”- Delegated access(your app doesn’t see the user’s Google password).
- Secure ways for apps to interact with each other.
- Scopes (fine-grained access control: email, profile, calendar, etc.).
❌ Cons:
Section titled “❌ Cons:”- Can be complex to implement correctly.
- Only handle authorization, not authentication by itself (though OpenID Connect adds authentication).
Example:
Section titled “Example:”- “Allow Spotify to access your Google contacts” → That’s OAuth.
🔹 2. SSO (Single Sign-On)
Section titled “🔹 2. SSO (Single Sign-On)”- SSO is an authentication method that allows user to log in once and gain access to multiple apps without logging in again.
⚙️ How it works:
Section titled “⚙️ How it works:”- You log in once at a central identity provider(IdP) (eg. Okta, Microsoft, Google).
- The IdP creates a session/token for you.
- When you access another app that trusts the same IdP, you’re already authenticated.
- You don’t need to enter your credentials again -> you’re automatically logged in.
✅ Pros:
Section titled “✅ Pros:”- Great user experience (one login for many apps).
- Centralized authentication (security, policies in one place).
- Works with SAML, OAuth, OpenID Connect under the hood.
❌ Cons:
Section titled “❌ Cons:”- If the IdP goes down → all apps are affected.
- Single point of attack if not secured properly.
Example:
Section titled “Example:”- You log in to your company portal → automatically get access to Gmail, Slack, Jira, GitHub (all integrated via SSO).
🔹 Key Differences
Section titled “🔹 Key Differences”| Feature | OAuth | SSO |
|---|---|---|
| Purpose | Authorization (delegated access to resources) | Authentication (log in once, access multiple apps) |
| Scope | API access (e.g., Google Drive, Spotify) | User identity across apps |
| Who uses it | Third-party apps (your app → Google/Facebook APIs) | Enterprises & organizations |
| Protocol | OAuth 2.0, OpenID Connect | Can use SAML, OAuth 2.0, OIDC |
| Example | “Allow Trello to access your Google Drive” | Login once → access Gmail, Calendar, Drive |
🔹 How They Work Together
Section titled “🔹 How They Work Together”- OAuth = lets apps access resources on your behalf.
- SSO = lets you log in once for multiple apps.
👉 Many modern SSO systems use OAuth (with OpenID Connect) under the hood for authentication + authorization.
Section titled “👉 Many modern SSO systems use OAuth (with OpenID Connect) under the hood for authentication + authorization.”For example:
Section titled “For example:”- Login with Google (SSO for all Google services) uses OAuth 2.0 + OpenID Connect.
- Corporate SSO (Okta, Auth0, Azure AD) often uses SAML or OIDC.
⚡ Real-world analogy:
Section titled “⚡ Real-world analogy:”- OAuth = “I give my friend the house key only for the garage, not the whole house.”
- SSO = “I unlock my house once, and all rooms are open for me.”