feat: validate OAUTH2_PROVIDER value

internal/cli/cli.go

@@ -89,6 +89,23 @@ func Parse() {
 		printErrorAndExit(err)
 	}
 
+	if oauth2Provider := config.Opts.OAuth2Provider(); oauth2Provider != "" {
+		if oauth2Provider != "oidc" && oauth2Provider != "google" {
+			printErrorAndExit(fmt.Errorf(`unsupported OAuth2 provider: %q (Possible values are "google" or "oidc")`, oauth2Provider))
+		}
+	}
+
+	if config.Opts.DisableLocalAuth() {
+		switch {
+		case config.Opts.OAuth2Provider() == "" && config.Opts.AuthProxyHeader() == "":
+			printErrorAndExit(errors.New("DISABLE_LOCAL_AUTH is enabled but neither OAUTH2_PROVIDER nor AUTH_PROXY_HEADER is not set. Please enable at least one authentication source"))
+		case config.Opts.OAuth2Provider() != "" && !config.Opts.IsOAuth2UserCreationAllowed():
+			printErrorAndExit(errors.New("DISABLE_LOCAL_AUTH is enabled and an OAUTH2_PROVIDER is configured, but OAUTH2_USER_CREATION is not enabled"))
+		case config.Opts.AuthProxyHeader() != "" && !config.Opts.IsAuthProxyUserCreationAllowed():
+			printErrorAndExit(errors.New("DISABLE_LOCAL_AUTH is enabled and an AUTH_PROXY_HEADER is configured, but AUTH_PROXY_USER_CREATION is not enabled"))
+		}
+	}
+
 	if flagConfigDump {
 		fmt.Print(config.Opts)
 		return
@@ -226,17 +243,6 @@ func Parse() {
 		return
 	}
 
-	if config.Opts.DisableLocalAuth() {
-		switch {
-		case config.Opts.OAuth2Provider() == "" && config.Opts.AuthProxyHeader() == "":
-			printErrorAndExit(errors.New("DISABLE_LOCAL_AUTH is enabled but neither OAUTH2_PROVIDER nor AUTH_PROXY_HEADER is not set. Please enable at least one authentication source"))
-		case config.Opts.OAuth2Provider() != "" && !config.Opts.IsOAuth2UserCreationAllowed():
-			printErrorAndExit(errors.New("DISABLE_LOCAL_AUTH is enabled and an OAUTH2_PROVIDER is configured, but OAUTH2_USER_CREATION is not enabled"))
-		case config.Opts.AuthProxyHeader() != "" && !config.Opts.IsAuthProxyUserCreationAllowed():
-			printErrorAndExit(errors.New("DISABLE_LOCAL_AUTH is enabled and an AUTH_PROXY_HEADER is configured, but AUTH_PROXY_USER_CREATION is not enabled"))
-		}
-	}
-
 	startDaemon(store)
 }