Single Sign-On (SSO)

OIDC OAuth2 SSO SAML

Single Sign-On (SSO) allows users to authenticate with multiple applications using a single set of credentials. This plugin supports OpenID Connect (OIDC), OAuth2 providers, and SAML 2.0.

Installation

Install the plugin

npm install @better-auth/sso

Add Plugin to the server

auth.ts

import { betterAuth } from "better-auth"
import { sso } from "@better-auth/sso";
 
const auth = betterAuth({
    plugins: [ 
        sso() 
    ] 
})

Migrate the database

Run the migration or generate the schema to add the necessary fields and tables to the database.

npx @better-auth/cli migrate

See the Schema section to add the fields manually.

Add the client plugin

auth-client.ts

import { createAuthClient } from "better-auth/client"
import { ssoClient } from "@better-auth/sso/client"
 
const authClient = createAuthClient({
    plugins: [ 
        ssoClient() 
    ] 
})

Usage

Register an OIDC Provider

To register an OIDC provider, use the registerSSOProvider endpoint and provide the necessary configuration details for the provider.

A redirect URL will be automatically generated using the provider ID. For instance, if the provider ID is hydra, the redirect URL would be {baseURL}/api/auth/sso/callback/hydra. Note that /api/auth may vary depending on your base path configuration.

Example

import { authClient } from "@/lib/auth-client";
 
// Register with OIDC configuration
await authClient.sso.register({
    providerId: "example-provider",
    issuer: "https://idp.example.com",
    domain: "example.com",
    oidcConfig: {
        clientId: "client-id",
        clientSecret: "client-secret",
        authorizationEndpoint: "https://idp.example.com/authorize",
        tokenEndpoint: "https://idp.example.com/token",
        jwksEndpoint: "https://idp.example.com/jwks",
        discoveryEndpoint: "https://idp.example.com/.well-known/openid-configuration",
        scopes: ["openid", "email", "profile"],
        pkce: true,
    },
    mapping: {
        id: "sub",
        email: "email",
        emailVerified: "email_verified",
        name: "name",
        image: "picture",
    },
});

Register a SAML Provider

To register a SAML provider, use the registerSSOProvider endpoint with SAML configuration details. The provider will act as a Service Provider (SP) and integrate with your Identity Provider (IdP).

import { authClient } from "@/lib/auth-client";
 
await authClient.sso.register({
    providerId: "saml-provider",
    issuer: "https://idp.example.com",
    domain: "example.com",
    samlConfig: {
        entryPoint: "https://idp.example.com/sso",
        cert: "-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----",
        callbackUrl: "https://yourapp.com/api/auth/sso/saml2/callback/saml-provider",
        audience: "https://yourapp.com",
        wantAssertionsSigned: true,
        signatureAlgorithm: "sha256",
        digestAlgorithm: "sha256",
        identifierFormat: "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress",
        idpMetadata: {
            metadata: "<!-- IdP Metadata XML -->",
            privateKey: "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----",
            privateKeyPass: "your-private-key-password",
            isAssertionEncrypted: true,
            encPrivateKey: "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----",
            encPrivateKeyPass: "your-encryption-key-password"
        },
        spMetadata: {
            metadata: "<!-- SP Metadata XML -->",
            binding: "post",
            privateKey: "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----",
            privateKeyPass: "your-sp-private-key-password",
            isAssertionEncrypted: true,
            encPrivateKey: "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----",
            encPrivateKeyPass: "your-sp-encryption-key-password"
        }
    },
    mapping: {
        id: "nameID",
        email: "email",
        name: "displayName",
        firstName: "givenName",
        lastName: "surname",
        extraFields: {
            department: "department",
            role: "role"
        }
    },
});

Get Service Provider Metadata

For SAML providers, you can retrieve the Service Provider metadata XML that needs to be configured in your Identity Provider:

get-sp-metadata.ts

const response = await auth.api.spMetadata({
    query: {
        providerId: "saml-provider",
        format: "xml" // or "json"
    }
});
 
const metadataXML = await response.text();
console.log(metadataXML);

To sign in with an SSO provider, you can call signIn.sso

You can sign in using the email with domain matching:

sign-in.ts

const res = await authClient.signIn.sso({
    email: "user@example.com",
    callbackURL: "/dashboard",
});

or you can specify the domain:

sign-in-domain.ts

const res = await authClient.signIn.sso({
    domain: "example.com",
    callbackURL: "/dashboard",
});

You can also sign in using the organization slug if a provider is associated with an organization:

sign-in-org.ts

const res = await authClient.signIn.sso({
    organizationSlug: "example-org",
    callbackURL: "/dashboard",
});

Alternatively, you can sign in using the provider's ID:

sign-in-provider-id.ts

const res = await authClient.signIn.sso({
    providerId: "example-provider-id",
    callbackURL: "/dashboard",
});

To use the server API you can use signInSSO

sign-in-org.ts

const res = await auth.api.signInSSO({
    body: {
        organizationSlug: "example-org",
        callbackURL: "/dashboard",
    }
});

Full method

POST

/sign-in/sso

const { data, error } = await authClient.signIn.sso({
    email: "john@example.com",
    organizationSlug: "example-org",
    providerId: "example-provider",
    domain: "example.com",
    callbackURL: "https://example.com/callback", // required
    errorCallbackURL: "https://example.com/callback",
    newUserCallbackURL: "https://example.com/new-user",
    scopes: ["openid", "email", "profile", "offline_access"],
    requestSignUp: true,
});

Prop	Description	Type
`email?`	The email address to sign in with. This is used to identify the issuer to sign in with. It's optional if the issuer is provided.	`string`
`organizationSlug?`	The slug of the organization to sign in with.	`string`
`providerId?`	The ID of the provider to sign in with. This can be provided instead of email or issuer.	`string`
`domain?`	The domain of the provider.	`string`
`callbackURL`	The URL to redirect to after login.	`string`
`errorCallbackURL?`	The URL to redirect to after login.	`string`
`newUserCallbackURL?`	The URL to redirect to after login if the user is new.	`string`
`scopes?`	Scopes to request from the provider.	`string[]`
`requestSignUp?`	Explicitly request sign-up. Useful when disableImplicitSignUp is true for this provider.	`boolean`

When a user is authenticated, if the user does not exist, the user will be provisioned using the provisionUser function. If the organization provisioning is enabled and a provider is associated with an organization, the user will be added to the organization.

auth.ts

const auth = betterAuth({
    plugins: [
        sso({
            provisionUser: async (user) => {
                // provision user
            },
            organizationProvisioning: {
                disabled: false,
                defaultRole: "member",
                getRole: async (user) => {
                    // get role if needed
                },
            },
        }),
    ],
});

Provisioning

The SSO plugin provides powerful provisioning capabilities to automatically set up users and manage their organization memberships when they sign in through SSO providers.

User Provisioning

User provisioning allows you to run custom logic whenever a user signs in through an SSO provider. This is useful for:

Setting up user profiles with additional data from the SSO provider
Synchronizing user attributes with external systems
Creating user-specific resources
Logging SSO sign-ins
Updating user information from the SSO provider

auth.ts

const auth = betterAuth({
    plugins: [
        sso({
            provisionUser: async ({ user, userInfo, token, provider }) => {
                // Update user profile with SSO data
                await updateUserProfile(user.id, {
                    department: userInfo.attributes?.department,
                    jobTitle: userInfo.attributes?.jobTitle,
                    manager: userInfo.attributes?.manager,
                    lastSSOLogin: new Date(),
                });
 
                // Create user-specific resources
                await createUserWorkspace(user.id);
 
                // Sync with external systems
                await syncUserWithCRM(user.id, userInfo);
 
                // Log the SSO sign-in
                await auditLog.create({
                    userId: user.id,
                    action: 'sso_signin',
                    provider: provider.providerId,
                    metadata: {
                        email: userInfo.email,
                        ssoProvider: provider.issuer,
                    },
                });
            },
        }),
    ],
});

The provisionUser function receives:

user: The user object from the database
userInfo: User information from the SSO provider (includes attributes, email, name, etc.)
token: OAuth2 tokens (for OIDC providers) - may be undefined for SAML
provider: The SSO provider configuration

Organization Provisioning

Organization provisioning automatically manages user memberships in organizations when SSO providers are linked to specific organizations. This is particularly useful for:

Enterprise SSO where each company/domain maps to an organization
Automatic role assignment based on SSO attributes
Managing team memberships through SSO

Basic Organization Provisioning

auth.ts

const auth = betterAuth({
    plugins: [
        sso({
            organizationProvisioning: {
                disabled: false,           // Enable org provisioning
                defaultRole: "member",     // Default role for new members
            },
        }),
    ],
});

Advanced Organization Provisioning with Custom Roles

auth.ts

const auth = betterAuth({
    plugins: [
        sso({
            organizationProvisioning: {
                disabled: false,
                defaultRole: "member",
                getRole: async ({ user, userInfo, provider }) => {
                    // Assign roles based on SSO attributes
                    const department = userInfo.attributes?.department;
                    const jobTitle = userInfo.attributes?.jobTitle;
                    
                    // Admins based on job title
                    if (jobTitle?.toLowerCase().includes('manager') || 
                        jobTitle?.toLowerCase().includes('director') ||
                        jobTitle?.toLowerCase().includes('vp')) {
                        return "admin";
                    }
                    
                    // Special roles for IT department
                    if (department?.toLowerCase() === 'it') {
                        return "admin";
                    }
                    
                    // Default to member for everyone else
                    return "member";
                },
            },
        }),
    ],
});

Linking SSO Providers to Organizations

When registering an SSO provider, you can link it to a specific organization:

await auth.api.registerSSOProvider({
    body: {
        providerId: "acme-corp-saml",
        issuer: "https://acme-corp.okta.com",
        domain: "acmecorp.com",
        organizationId: "org_acme_corp_id", // Link to organization
        samlConfig: {
            // SAML configuration...
        },
    },
    headers,
});

Now when users from acmecorp.com sign in through this provider, they'll automatically be added to the "Acme Corp" organization with the appropriate role.

Multiple Organizations Example

You can set up multiple SSO providers for different organizations:

multi-org-setup.ts

// Acme Corp SAML provider
await auth.api.registerSSOProvider({
    body: {
        providerId: "acme-corp",
        issuer: "https://acme.okta.com",
        domain: "acmecorp.com",
        organizationId: "org_acme_id",
        samlConfig: { /* ... */ },
    },
    headers,
});
 
// TechStart OIDC provider
await auth.api.registerSSOProvider({
    body: {
        providerId: "techstart-google",
        issuer: "https://accounts.google.com",
        domain: "techstart.io",
        organizationId: "org_techstart_id",
        oidcConfig: { /* ... */ },
    },
    headers,
});

Organization Provisioning Flow

User signs in through an SSO provider linked to an organization
User is authenticated and either found or created in the database
Organization membership is checked - if the user isn't already a member of the linked organization
Role is determined using either the defaultRole or getRole function
User is added to the organization with the determined role
User provisioning runs (if configured) for additional setup

Provisioning Best Practices

1. Idempotent Operations

Make sure your provisioning functions can be safely run multiple times:

provisionUser: async ({ user, userInfo }) => {
    // Check if already provisioned
    const existingProfile = await getUserProfile(user.id);
    if (!existingProfile.ssoProvisioned) {
        await createUserResources(user.id);
        await markAsProvisioned(user.id);
    }
    
    // Always update attributes (they might change)
    await updateUserAttributes(user.id, userInfo.attributes);
},

2. Error Handling

Handle errors gracefully to avoid blocking user sign-in:

provisionUser: async ({ user, userInfo }) => {
    try {
        await syncWithExternalSystem(user, userInfo);
    } catch (error) {
        // Log error but don't throw - user can still sign in
        console.error('Failed to sync user with external system:', error);
        await logProvisioningError(user.id, error);
    }
},

3. Conditional Provisioning

Only run certain provisioning steps when needed:

organizationProvisioning: {
    disabled: false,
    getRole: async ({ user, userInfo, provider }) => {
        // Only process role assignment for certain providers
        if (provider.providerId.includes('enterprise')) {
            return determineEnterpriseRole(userInfo);
        }
        return "member";
    },
},

SAML Configuration

Service Provider Configuration

When registering a SAML provider, you need to provide Service Provider (SP) metadata configuration:

metadata: XML metadata for the Service Provider
binding: The binding method, typically "post" or "redirect"
privateKey: Private key for signing (optional)
privateKeyPass: Password for the private key (if encrypted)
isAssertionEncrypted: Whether assertions should be encrypted
encPrivateKey: Private key for decryption (if encryption is enabled)
encPrivateKeyPass: Password for the encryption private key

Identity Provider Configuration

You also need to provide Identity Provider (IdP) configuration:

metadata: XML metadata from your Identity Provider
privateKey: Private key for the IdP communication (optional)
privateKeyPass: Password for the IdP private key (if encrypted)
isAssertionEncrypted: Whether assertions from IdP are encrypted
encPrivateKey: Private key for IdP assertion decryption
encPrivateKeyPass: Password for the IdP decryption key

SAML Attribute Mapping

Configure how SAML attributes map to user fields:

mapping: {
    id: "nameID",           // Default: "nameID"
    email: "email",         // Default: "email" or "nameID"
    name: "displayName",    // Default: "displayName"
    firstName: "givenName", // Default: "givenName"
    lastName: "surname",    // Default: "surname"
    extraFields: {
        department: "department",
        role: "jobTitle",
        phone: "telephoneNumber"
    }
}

SAML Endpoints

The plugin automatically creates the following SAML endpoints:

SP Metadata: /api/auth/sso/saml2/sp/metadata?providerId={providerId}
SAML Callback: /api/auth/sso/saml2/callback/{providerId}

Schema

The plugin requires additional fields in the ssoProvider table to store the provider's configuration.

Field Name	Type	Key	Description
id	string		A database identifier
issuer	string	-	The issuer identifier
domain	string	-	The domain of the provider
oidcConfig	string	-	The OIDC configuration (JSON string)
samlConfig	string	-	The SAML configuration (JSON string)
userId	string	-	The user ID
providerId	string	-	The provider ID. Used to identify a provider and to generate a redirect URL.
organizationId	string	-	The organization Id. If provider is linked to an organization.

Options

Server

provisionUser: A custom function to provision a user when they sign in with an SSO provider.

organizationProvisioning: Options for provisioning users to an organization.

defaultOverrideUserInfo: Override user info with the provider info by default.

disableImplicitSignUp: Disable implicit sign up for new users.

trustEmailVerified: Trust the email verified flag from the provider.

Prop	Type	Default
`provisionUser?`	`function`	-
`organizationProvisioning?`	`object`	-
`defaultOverrideUserInfo?`	`boolean`	-
`disableImplicitSignUp?`	`boolean`	-
`providersLimit?`	`number \| function`	`10`

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