Microsoft Authentication Library (MSAL) for Go

The Microsoft Authentication Library (MSAL) for Go is part of the Microsoft identity platform for developers (formerly named Azure AD) v2.0. It allows you to sign in users or apps with Microsoft identities (Azure AD and Microsoft Accounts) and obtain tokens to call Microsoft APIs such as Microsoft Graph or your own APIs registered with the Microsoft identity platform. It is built using industry standard OAuth2 and OpenID Connect protocols.

The latest code resides in the dev branch.

Quick links:

Build Status

Installation

Setting up Go

To install Go, visit this link.

Installing MSAL Go

go get -u github.com/AzureAD/microsoft-authentication-library-for-go/

Usage

Before using MSAL Go, you will need to register your application with the Microsoft identity platform.

Acquiring Tokens

Acquiring tokens with MSAL Go follows this general pattern. There might be some slight differences for other token acquisition flows. Here is a basic example:

1. Create a client. MSAL separates public and confidential client applications, so call public.New() or confidential.New() to create the appropriate client for your application.

   • Initializing a public client:

   import "github.com/AzureAD/microsoft-authentication-library-for-go/apps/public"
   
   publicClient, err := public.New("client_id", public.WithAuthority("https://login.microsoftonline.com/your_tenant"))
   

   • Initializing a confidential client:

   import "github.com/AzureAD/microsoft-authentication-library-for-go/apps/confidential"
   
   // confidential clients have a credential, such as a secret or a certificate
   cred, err := confidential.NewCredFromSecret("client_secret")
   if err != nil {
       // TODO: handle error
   }
   confidentialClient, err := confidential.New("https://login.microsoftonline.com/your_tenant", "client_id", cred)
   

   • Initializing a Managed Identity client for SystemAssigned:

   import mi "github.com/AzureAD/microsoft-authentication-library-for-go/apps/managedidentity"
   
   // Managed identity client have a type of ID required, SystemAssigned or UserAssigned
   miSystemAssigned, err := mi.New(mi.SystemAssigned())
   if err != nil {
       // TODO: handle error
   }
   

   • Initializing a Managed Identity client for UserAssigned:

   import mi "github.com/AzureAD/microsoft-authentication-library-for-go/apps/managedidentity"
   
   // Managed identity client have a type of ID required, SystemAssigned or UserAssigned
   miSystemAssigned, err := mi.New(mi.UserAssignedClientID("YOUR_CLIENT_ID"))
   if err != nil {
       // TODO: handle error
   }
   

2. Call AcquireTokenSilent() to look for a cached token. If AcquireTokenSilent() returns an error, call another AcquireToken... method to authenticate.

   • Public clients should specify a user account, if one is available:

   // If your application previously authenticated a user, call AcquireTokenSilent with that user's account
   // to use cached authentication data. This example shows choosing an account from the cache, however this
   // isn't always necessary because the AuthResult returned by authentication methods includes user account
   // information.
   accounts, err := client.Accounts(context.TODO())
   if err != nil {
       // TODO: handle error
   }
   if len(accounts) > 0 {
       // There may be more accounts; here we assume the first one is wanted.
       // AcquireTokenSilent returns a non-nil error when it can't provide a token.
       result, err = client.AcquireTokenSilent(context.TODO(), scopes, public.WithSilentAccount(accounts[0]))
   }
   if err != nil || len(accounts) == 0 {
       // cache miss, authenticate a user with another AcquireToken* method
       result, err = client.AcquireTokenInteractive(context.TODO(), scopes)
       if err != nil {
           // TODO: handle error
       }
   }
   // TODO: save the authenticated user's account, use the access token
   userAccount := result.Account
   accessToken := result.AccessToken
   

   • Confidential clients can simply call AcquireTokenSilent():

   scopes := []string{"scope"}
   result, err := confidentialClient.AcquireTokenSilent(context.TODO(), scopes)
   if err != nil {
       // cache miss, authenticate with another AcquireToken... method
       result, err = confidentialClient.AcquireTokenByCredential(context.TODO(), scopes)
       if err != nil {
           // TODO: handle error
       }
   }
   accessToken := result.AccessToken
   

   • ManagedIdentity client can simply call AcquireToken():

   resource := "<Your resource>"
   result, err := miSystemAssigned.AcquireToken(context.TODO(), resource)
   if err != nil {
       // TODO: handle error
   }
   accessToken := result.AccessToken
   

Loading Certificates from PEM

confidential.CertFromPEM loads a certificate and an unencrypted private key from PEM data for use with NewCredFromCert.

Security note — encrypted PEM is not supported: CertFromPEM rejects legacy RFC 1423 encrypted PEM blocks (those with a DEK-Info header, e.g. DEK-Info: DES-EDE3-CBC,...) with an error. That format relies on a weak key derivation function (a single MD5 iteration) and obsolete DES/3DES ciphers, which provide little protection against offline password-guessing attacks.

Provide the private key unencrypted and protect it with filesystem permissions. You can strip legacy encryption with OpenSSL:

openssl pkcs8 -topk8 -nocrypt -in legacy.key -out key.pem

Community Help and Support

We use Stack Overflow to work with the community on supporting Azure Active Directory and its SDKs, including this one! We highly recommend you ask your questions on Stack Overflow (we're all on there!) Also browse existing issues to see if someone has had your question before. Please use the "msal" tag when asking your questions.

If you find and bug or have a feature request, please raise the issue on GitHub Issues.

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Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.opensource.microsoft.com.

When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.

Security Library

This library controls how users sign-in and access services. We recommend you always take the latest version of our library in your app when possible. We use semantic versioning so you can control the risk associated with updating your app. As an example, always downloading the latest minor version number (e.g. x.y.x) ensures you get the latest security and feature enhancements but our API surface remains the same. You can always see the latest version and release notes under the Releases tab of GitHub.

Security Reporting

If you find a security issue with our libraries or services please report it to secure@microsoft.com with as much detail as possible. Your submission may be eligible for a bounty through the Microsoft Bounty program. Please do not post security issues to GitHub Issues or any other public site. We will contact you shortly upon receiving the information. We encourage you to get notifications of when security incidents occur by visiting this page and subscribing to Security Advisory Alerts.

Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT License (the "License").