feat(auth): add custom github app authentication with automatic token refresh

Author: alcoholmajuu

README.md

@@ -183,9 +183,14 @@ GitHub Enterprise Server does not support remote server hosting. Please refer to
 1. To run the server in a container, you will need to have [Docker](https://www.docker.com/) installed.
 2. Once Docker is installed, you will also need to ensure Docker is running. The Docker image is available at `ghcr.io/github/github-mcp-server`. The image is public; if you get errors on pull, you may have an expired token and need to `docker logout ghcr.io`.
 3. **Authentication.** On github.com you don't need to create anything up front — the one-click buttons above log you in with OAuth on first use (a browser-based flow; the token is kept in memory only). The Docker buttons publish a fixed callback port (`127.0.0.1:8085`) so the container's login callback is reachable. See **[Local Server OAuth Login](docs/oauth-login.md)** for how it works, headless/device-code fallback, and bringing your own OAuth or GitHub App (required for GitHub Enterprise Server and `ghe.com`).
-
    Prefer a token? You can still authenticate with a [GitHub Personal Access Token](https://github.com/settings/personal-access-tokens/new) by setting `GITHUB_PERSONAL_ACCESS_TOKEN` instead (it takes precedence over OAuth). The MCP server can use many of the GitHub APIs, so enable the permissions that you feel comfortable granting your AI tools (to learn more about access tokens, please check out the [documentation](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens)).
 
+   **Using GitHub App Authentication.** Alternatively, you can run the server as a GitHub App installation. This is recommended for automated environments or enterprise deployments. Set the following environment variables (or pass the corresponding CLI flags):
+   - `GITHUB_APP_ID` (or `--app-id`): The GitHub App ID.
+   - `GITHUB_APP_INSTALLATION_ID` (or `--app-installation-id`): The App installation ID.
+   - `GITHUB_APP_PRIVATE_KEY` (or `--app-private-key`): The RSA private key PEM block string.
+   - `GITHUB_APP_PRIVATE_KEY_PATH` (or `--app-private-key-path`): Alternatively, the file path to the RSA private key PEM file.
+
 <details><summary><b>Handling PATs Securely</b></summary>
 
 ### Environment Variables (Recommended)

cmd/github-mcp-server/main.go

@@ -13,9 +13,11 @@ import (
 	"github.com/github/github-mcp-server/pkg/github"
 	ghhttp "github.com/github/github-mcp-server/pkg/http"
 	ghoauth "github.com/github/github-mcp-server/pkg/http/oauth"
+	"github.com/github/github-mcp-server/pkg/utils"
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
 	"github.com/spf13/viper"
+	"golang.org/x/oauth2"
 )
 
 // These variables are set by the build process using ldflags.
@@ -39,6 +41,22 @@ var (
 			token := viper.GetString("personal_access_token")
 			oauthClientID := viper.GetString("oauth-client-id")
 			oauthClientSecret := viper.GetString("oauth-client-secret")
+
+			// Check GitHub App configuration
+			appID := viper.GetInt64("app-id")
+			appInstallationID := viper.GetInt64("app-installation-id")
+			appPrivateKey := viper.GetString("app-private-key")
+			appPrivateKeyPath := viper.GetString("app-private-key-path")
+
+			var appTokenSource oauth2.TokenSource
+			if appID != 0 && appInstallationID != 0 {
+				var err error
+				appTokenSource, err = utils.NewGitHubAppTokenSource(appID, appInstallationID, []byte(appPrivateKey), appPrivateKeyPath, viper.GetString("host"))
+				if err != nil {
+					return err
+				}
+			}
+
 			// Fall back to the build-time baked-in client (official releases) when none is
 			// configured explicitly. The baked-in app is registered on github.com, so it is
 			// only applied to the default host; GHES/ghe.com users must bring their own
@@ -50,8 +68,8 @@ var (
 				oauthClientID = buildinfo.OAuthClientID
 				oauthClientSecret = buildinfo.OAuthClientSecret
 			}
-			if token == "" && oauthClientID == "" {
-				return errors.New("authentication required: set GITHUB_PERSONAL_ACCESS_TOKEN, or pass --oauth-client-id to log in via OAuth")
+			if token == "" && oauthClientID == "" && appTokenSource == nil {
+				return errors.New("authentication required: set GITHUB_PERSONAL_ACCESS_TOKEN, pass --oauth-client-id to log in via OAuth, or configure GitHub App credentials")
 			}
 
 			// If you're wondering why we're not using viper.GetStringSlice("toolsets"),
@@ -110,13 +128,14 @@ var (
 				InsidersMode:         viper.GetBool("insiders"),
 				ExcludeTools:         excludeTools,
 				RepoAccessCacheTTL:   &ttl,
+				GitHubAppTokenSource: appTokenSource,
 			}
 
-			// When no static token is provided, log in via OAuth using the given
+			// When no static token or GitHub App TokenSource is set, log in via OAuth using the given
 			// client. The requested scopes default to the full supported set
 			// (which filters out no tools); an explicit, narrower --oauth-scopes
 			// both narrows the grant and hides tools needing other scopes.
-			if token == "" {
+			if token == "" && appTokenSource == nil {
 				scopes := ghoauth.SupportedScopes
 				if viper.IsSet("oauth-scopes") {
 					if err := viper.UnmarshalKey("oauth-scopes", &scopes); err != nil {
@@ -172,6 +191,21 @@ var (
 				}
 			}
 
+			// Check GitHub App configuration for HTTP mode
+			appID := viper.GetInt64("app-id")
+			appInstallationID := viper.GetInt64("app-installation-id")
+			appPrivateKey := viper.GetString("app-private-key")
+			appPrivateKeyPath := viper.GetString("app-private-key-path")
+
+			var appTokenSource oauth2.TokenSource
+			if appID != 0 && appInstallationID != 0 {
+				var err error
+				appTokenSource, err = utils.NewGitHubAppTokenSource(appID, appInstallationID, []byte(appPrivateKey), appPrivateKeyPath, viper.GetString("host"))
+				if err != nil {
+					return err
+				}
+			}
+
 			ttl := viper.GetDuration("repo-access-cache-ttl")
 			httpConfig := ghhttp.ServerConfig{
 				Version:              version,
@@ -194,6 +228,7 @@ var (
 				EnabledFeatures:      enabledFeatures,
 				InsidersMode:         viper.GetBool("insiders"),
 				TrustProxyHeaders:    viper.GetBool("trust-proxy-headers"),
+				GitHubAppTokenSource: appTokenSource,
 			}
 
 			return ghhttp.RunHTTPServer(httpConfig)
@@ -222,6 +257,12 @@ func init() {
 	rootCmd.PersistentFlags().Bool("insiders", false, "Enable insiders features")
 	rootCmd.PersistentFlags().Duration("repo-access-cache-ttl", 5*time.Minute, "Override the repo access cache TTL (e.g. 1m, 0s to disable)")
 
+	// GitHub App flags
+	rootCmd.PersistentFlags().Int64("app-id", 0, "GitHub App ID")
+	rootCmd.PersistentFlags().Int64("app-installation-id", 0, "GitHub App Installation ID")
+	rootCmd.PersistentFlags().String("app-private-key", "", "GitHub App Private Key PEM content")
+	rootCmd.PersistentFlags().String("app-private-key-path", "", "Path to GitHub App Private Key PEM file")
+
 	// stdio-specific OAuth flags. Provide --oauth-client-id (instead of a token)
 	// to log in via the browser-based OAuth flow on first use. Works for both
 	// OAuth Apps and GitHub Apps.
@@ -252,6 +293,10 @@ func init() {
 	_ = viper.BindPFlag("lockdown-mode", rootCmd.PersistentFlags().Lookup("lockdown-mode"))
 	_ = viper.BindPFlag("insiders", rootCmd.PersistentFlags().Lookup("insiders"))
 	_ = viper.BindPFlag("repo-access-cache-ttl", rootCmd.PersistentFlags().Lookup("repo-access-cache-ttl"))
+	_ = viper.BindPFlag("app-id", rootCmd.PersistentFlags().Lookup("app-id"))
+	_ = viper.BindPFlag("app-installation-id", rootCmd.PersistentFlags().Lookup("app-installation-id"))
+	_ = viper.BindPFlag("app-private-key", rootCmd.PersistentFlags().Lookup("app-private-key"))
+	_ = viper.BindPFlag("app-private-key-path", rootCmd.PersistentFlags().Lookup("app-private-key-path"))
 	_ = viper.BindPFlag("oauth-client-id", stdioCmd.Flags().Lookup("oauth-client-id"))
 	_ = viper.BindPFlag("oauth-client-secret", stdioCmd.Flags().Lookup("oauth-client-secret"))
 	_ = viper.BindPFlag("oauth-scopes", stdioCmd.Flags().Lookup("oauth-scopes"))

go.mod

@@ -4,7 +4,9 @@ go 1.25.0
 
 require (
 	github.com/go-chi/chi/v5 v5.3.1
+	github.com/go-resty/resty/v2 v2.17.2
 	github.com/go-viper/mapstructure/v2 v2.5.0
+	github.com/golang-jwt/jwt/v5 v5.3.1
 	github.com/google/go-github/v89 v89.0.0
 	github.com/google/jsonschema-go v0.4.3
 	github.com/josephburnett/jd/v2 v2.5.0

go.sum

@@ -9,6 +9,8 @@ github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S
 github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/go-chi/chi/v5 v5.3.1 h1:3j4HZLGZQ3JpMCrPJF/Jl3mYJfWLKBfNJ6quurUGCf8=
 github.com/go-chi/chi/v5 v5.3.1/go.mod h1:R+tYY2hNuVUUjxoPtqUdgBqevM9s9njzkTLutVsOCto=
+github.com/go-resty/resty/v2 v2.17.2 h1:FQW5oHYcIlkCNrMD2lloGScxcHJ0gkjshV3qcQAyHQk=
+github.com/go-resty/resty/v2 v2.17.2/go.mod h1:kCKZ3wWmwJaNc7S29BRtUhJwy7iqmn+2mLtQrOyQlVA=
 github.com/go-viper/mapstructure/v2 v2.5.0 h1:vM5IJoUAy3d7zRSVtIwQgBj7BiWtMPfmPEgAXnvj1Ro=
 github.com/go-viper/mapstructure/v2 v2.5.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/golang-jwt/jwt/v5 v5.3.1 h1:kYf81DTWFe7t+1VvL7eS+jKFVWaUnK9cB1qbwn63YCY=

internal/ghmcp/server.go

@@ -28,6 +28,7 @@ import (
 	gogithub "github.com/google/go-github/v89/github"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 	"github.com/shurcooL/githubv4"
+	"golang.org/x/oauth2"
 )
 
 // githubClients holds all the GitHub API clients created for a server instance.
@@ -257,6 +258,9 @@ type StdioServerConfig struct {
 	// are hidden. The default set is the full supported list, which hides
 	// nothing; an explicit, narrower list filters accordingly.
 	OAuthScopes []string
+
+	// GitHubAppTokenSource, when non-nil, supplies the GitHub App installation token.
+	GitHubAppTokenSource oauth2.TokenSource
 }
 
 // RunStdioServer is not concurrent safe.
@@ -318,6 +322,14 @@ func RunStdioServer(cfg StdioServerConfig) error {
 	if cfg.OAuthManager != nil {
 		tokenProvider = cfg.OAuthManager.AccessToken
 		toolHandlerMiddleware = append(toolHandlerMiddleware, createOAuthToolMiddleware(cfg.OAuthManager, logger))
+	} else if cfg.GitHubAppTokenSource != nil {
+		tokenProvider = func() string {
+			tok, err := cfg.GitHubAppTokenSource.Token()
+			if err != nil {
+				return ""
+			}
+			return tok.AccessToken
+		}
 	}
 
 	ghServer, err := NewStdioMCPServer(ctx, github.MCPServerConfig{

pkg/github/dependencies.go

@@ -21,6 +21,7 @@ import (
 	gogithub "github.com/google/go-github/v89/github"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 	"github.com/shurcooL/githubv4"
+	"golang.org/x/oauth2"
 )
 
 // depsContextKey is the context key for ToolDependencies.
@@ -267,12 +268,13 @@ func NewToolFromHandler(
 
 type RequestDeps struct {
 	// Static dependencies
-	apiHosts          utils.APIHostResolver
-	version           string
-	lockdownMode      bool
-	RepoAccessOpts    []lockdown.RepoAccessOption
-	T                 translations.TranslationHelperFunc
-	ContentWindowSize int
+	apiHosts             utils.APIHostResolver
+	version              string
+	lockdownMode         bool
+	RepoAccessOpts       []lockdown.RepoAccessOption
+	T                    translations.TranslationHelperFunc
+	ContentWindowSize    int
+	gitHubAppTokenSource oauth2.TokenSource
 
 	// Feature flag checker for runtime checks
 	featureChecker inventory.FeatureFlagChecker
@@ -291,27 +293,41 @@ func NewRequestDeps(
 	contentWindowSize int,
 	featureChecker inventory.FeatureFlagChecker,
 	obsv observability.Exporters,
+	gitHubAppTokenSource oauth2.TokenSource,
 ) *RequestDeps {
 	return &RequestDeps{
-		apiHosts:          apiHosts,
-		version:           version,
-		lockdownMode:      lockdownMode,
-		RepoAccessOpts:    repoAccessOpts,
-		T:                 t,
-		ContentWindowSize: contentWindowSize,
-		featureChecker:    featureChecker,
-		obsv:              obsv,
+		apiHosts:             apiHosts,
+		version:              version,
+		lockdownMode:         lockdownMode,
+		RepoAccessOpts:       repoAccessOpts,
+		T:                    t,
+		ContentWindowSize:    contentWindowSize,
+		featureChecker:       featureChecker,
+		obsv:                 obsv,
+		gitHubAppTokenSource: gitHubAppTokenSource,
 	}
 }
 
+func (d *RequestDeps) resolveToken(ctx context.Context) (string, error) {
+	if tokenInfo, ok := ghcontext.GetTokenInfo(ctx); ok {
+		return tokenInfo.Token, nil
+	}
+	if d.gitHubAppTokenSource != nil {
+		tok, err := d.gitHubAppTokenSource.Token()
+		if err != nil {
+			return "", fmt.Errorf("failed to get default token from GitHub App source: %w", err)
+		}
+		return tok.AccessToken, nil
+	}
+	return "", fmt.Errorf("no token info in context and no default token source configured")
+}
+
 // GetClient implements ToolDependencies.
 func (d *RequestDeps) GetClient(ctx context.Context) (*gogithub.Client, error) {
-	// extract the token from the context
-	tokenInfo, ok := ghcontext.GetTokenInfo(ctx)
-	if !ok {
-		return nil, fmt.Errorf("no token info in context")
+	token, err := d.resolveToken(ctx)
+	if err != nil {
+		return nil, err
 	}
-	token := tokenInfo.Token
 
 	baseRestURL, err := d.apiHosts.BaseRESTURL(ctx)
 	if err != nil {
@@ -336,12 +352,15 @@ func (d *RequestDeps) GetClient(ctx context.Context) (*gogithub.Client, error) {
 
 // GetGQLClient implements ToolDependencies.
 func (d *RequestDeps) GetGQLClient(ctx context.Context) (*githubv4.Client, error) {
-	// extract the token from the context
-	tokenInfo, ok := ghcontext.GetTokenInfo(ctx)
-	if !ok {
-		return nil, fmt.Errorf("no token info in context")
+	token, err := d.resolveToken(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	graphqlURL, err := d.apiHosts.GraphqlURL(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get GraphQL URL: %w", err)
 	}
-	token := tokenInfo.Token
 
 	// Construct GraphQL client
 	// We use NewEnterpriseClient unconditionally since we already parsed the API host
@@ -356,11 +375,6 @@ func (d *RequestDeps) GetGQLClient(ctx context.Context) (*githubv4.Client, error
 		},
 	}
 
-	graphqlURL, err := d.apiHosts.GraphqlURL(ctx)
-	if err != nil {
-		return nil, fmt.Errorf("failed to get GraphQL URL: %w", err)
-	}
-
 	gqlClient := githubv4.NewEnterpriseClient(graphqlURL.String(), gqlHTTPClient)
 	return gqlClient, nil
 }

pkg/http/server.go

@@ -25,6 +25,7 @@ import (
 	"github.com/github/github-mcp-server/pkg/translations"
 	"github.com/github/github-mcp-server/pkg/utils"
 	"github.com/go-chi/chi/v5"
+	"golang.org/x/oauth2"
 )
 
 type ServerConfig struct {
@@ -100,6 +101,9 @@ type ServerConfig struct {
 
 	// InsidersMode expands to the curated set of feature flags enabled for insiders.
 	InsidersMode bool
+
+	// GitHubAppTokenSource, when non-nil, supplies the GitHub App installation token.
+	GitHubAppTokenSource oauth2.TokenSource
 }
 
 func RunHTTPServer(cfg ServerConfig) error {
@@ -153,6 +157,7 @@ func RunHTTPServer(cfg ServerConfig) error {
 		cfg.ContentWindowSize,
 		featureChecker,
 		obs,
+		cfg.GitHubAppTokenSource,
 	)
 
 	// Initialize the global tool scope map