Add function to explictly request a certain provider

Signed-off-by: Priya Wadhwa <priya@chainguard.dev>

pkg/providers/all/all.go

@@ -27,6 +27,7 @@ import (
 
 // Alias these methods, so that folks can import this to get all providers.
 var (
-	Enabled = providers.Enabled
-	Provide = providers.Provide
+	Enabled         = providers.Enabled
+	Provide         = providers.Provide
+	ExplicitProvide = providers.ExplicitProvide
 )

pkg/providers/interface.go

@@ -83,3 +83,18 @@ func Provide(ctx context.Context, audience string) (string, error) {
 	}
 	return id, err
 }
+
+// ExplicitProvide fetches an OIDC token from the specified provider
+func ExplicitProvide(ctx context.Context, audience, provider string) (string, error) {
+	m.Lock()
+	defer m.Unlock()
+
+	p, ok := providers[provider]
+	if !ok {
+		return "", fmt.Errorf("%s is not a valid provider", provider)
+	}
+	if !p.Enabled(ctx) {
+		return "", fmt.Errorf("provider %s is not enabled, check providers.Enabled() before providers.ExplicitProvide()", provider)
+	}
+	return p.Provide(ctx, audience)
+}