This block of code introduces a critical bug that breaks existing functionality. It unconditionally re-loads the configuration from the credentialManager, which overwrites any configuration that might have been loaded from a file (option.Config) in the preceding lines (172-182).

Problematic Flow:

1. If a user provides a config file, iam.loadS3ApiConfigurationFromFile() is called, and the iam instance is populated.
2. This new block then executes iam.credentialManager.LoadConfiguration(), which fetches configuration from the credential store (e.g., filer), effectively discarding the configuration from the file.
3. iam.loadS3ApiConfiguration() is called again with this new configuration, overwriting the iam state.

This needs to be refactored to ensure that configuration is loaded only once, then modified with environment variable credentials, and finally applied.

A suggested approach for NewIdentityAccessManagementWithStore:

func NewIdentityAccessManagementWithStore(option *S3ApiServerOption, explicitStore string) *IdentityAccessManagement {
	// ... (iam and credentialManager initialization)

	var s3ApiConfiguration *iam_pb.S3ApiConfiguration
	var err error

	if option.Config != "" {
		glog.V(3).Infof("loading static config file %s", option.Config)
		content, readErr := os.ReadFile(option.Config)
		if readErr != nil {
			glog.Fatalf("fail to read config file %s: %v", option.Config, readErr)
		}
		s3ApiConfiguration = &iam_pb.S3ApiConfiguration{}
		if err = filer.ParseS3ConfigurationFromBytes(content, s3ApiConfiguration); err != nil {
			glog.Fatalf("unmarshal error from %s: %v", option.Config, err)
		}
	} else {
		glog.V(3).Infof("no static config file specified... loading config from credential manager")
		s3ApiConfiguration, err = iam.credentialManager.LoadConfiguration(context.Background())
		if err != nil {
			glog.Warningf("fail to load config: %v", err)
			// Create empty configuration if loading fails
			s3ApiConfiguration = &iam_pb.S3ApiConfiguration{}
		}
	}

	// Load environment variable credentials
	iam.loadAdminCredentialsFromEnv(s3ApiConfiguration)

	// Apply the updated configuration
	if err := iam.loadS3ApiConfiguration(s3ApiConfiguration); err != nil {
		glog.Warningf("failed to apply initial configuration: %v", err)
	}

	return iam
}

The indentation for this list seems to be inconsistent, using a mix of spaces and tabs. This can lead to inconsistent rendering in different terminals and editors.

For better readability and consistency with the surrounding help text, please use tabs for indentation.

The environment variable names "WEED_S3_ADMIN_USER" and "WEED_S3_ADMIN_PASSWORD" are used as magic strings here and in other parts of the codebase (tests, command documentation). To improve maintainability and prevent typos, it's a best practice to define them as constants.

Please consider defining these at the package level and using the constants throughout the code.

const (
	AdminUserEnv     = "WEED_S3_ADMIN_USER"
	AdminPasswordEnv = "WEED_S3_ADMIN_PASSWORD"
)

// ...

func (iam *IdentityAccessManagement) loadAdminCredentialsFromEnv(...) {
    adminUser := os.Getenv(AdminUserEnv)
    adminPassword := os.Getenv(AdminPasswordEnv)
    // ...
}

This log message is misleading. The error is from iam.credentialManager.LoadConfiguration, not from loading environment variables. This could make debugging more difficult. The log message should accurately describe the failed operation.

glog.Warningf("failed to load configuration from credential manager: %v", err)

The accessKeyIdent map is being accessed without checking if it's initialized. This could cause a nil pointer panic if the map hasn't been properly initialized during IAM setup.

Logging the access key ID in plain text could expose sensitive credential information in log files. Consider logging only a masked or truncated version for security purposes.

The identity name contains part of the access key ID which could expose sensitive information in logs. Consider using a generic message or ensuring logs are properly secured.

The current method of checking for an existing accessKeyId involves iterating through all identities and their credentials, which can be inefficient, especially with a large number of identities. Since iam.accessKeyIdent is a map designed for quick lookups of identities by access key, it should be used here for better performance and code simplicity.

iam.m.RLock()
_, accessKeyExists := iam.accessKeyIdent[accessKeyId]
iam.m.RUnlock()

The test TestNewIdentityAccessManagementWithStoreEnvVars is a great start, but it only covers cases where no configuration file is loaded. To ensure the logic correctly handles interactions with existing configurations, consider adding test cases for these scenarios:

1. Existing Access Key: A configuration file is loaded, and the accessKeyId from the environment variables already exists in it. Assert that the identity from the environment variables is not added.
2. New Access Key: A configuration file is loaded, and the accessKeyId from the environment variables is new. Assert that the new identity is added alongside the existing identities from the configuration file.

Consider using a constant for the maximum length of the access key ID to avoid "magic number".

const accessKeyIdSuffixLength = 8
identityNameSuffix := accessKeyId
if len(accessKeyId) > accessKeyIdSuffixLength {
	identityNameSuffix = accessKeyId[:accessKeyIdSuffixLength]
}

Consider defining the string "admin-" as a constant to avoid a "magic string".

const adminIdentityNamePrefix = "admin-"
Name:    adminIdentityNamePrefix + identityNameSuffix,

Consider using atomic.StoreBool to ensure that iam.isAuthEnabled is updated atomically.

iam.m.Unlock()
			atomic.StoreBool(&iam.isAuthEnabled, true)
			iam.m.Lock()