external auth: add example HTTP server to use as authentication hook

The server authenticate against an LDAP server.

examples/ldapauthserver/config/config.go

@@ -0,0 +1,158 @@
+package config
+
+import (
+	"strings"
+
+	"github.com/drakkan/sftpgo/ldapauthserver/logger"
+	"github.com/spf13/viper"
+)
+
+const (
+	logSender = "config"
+	// DefaultConfigName defines the name for the default config file.
+	// This is the file name without extension, we use viper and so we
+	// support all the config files format supported by viper
+	DefaultConfigName = "ldapauth"
+	// ConfigEnvPrefix defines a prefix that ENVIRONMENT variables will use
+	configEnvPrefix = "ldapauth"
+)
+
+// HTTPDConfig defines configuration for the HTTPD server
+type HTTPDConfig struct {
+	BindAddress        string `mapstructure:"bind_address"`
+	BindPort           int    `mapstructure:"bind_port"`
+	AuthUserFile       string `mapstructure:"auth_user_file"`
+	CertificateFile    string `mapstructure:"certificate_file"`
+	CertificateKeyFile string `mapstructure:"certificate_key_file"`
+}
+
+// LDAPConfig defines the configuration parameters for LDAP connections and searchs
+type LDAPConfig struct {
+	BaseDN             string   `mapstructure:"basedn"`
+	BindURL            string   `mapstructure:"bind_url"`
+	BindUsername       string   `mapstructure:"bind_username"`
+	BindPassword       string   `mapstructure:"bind_password"`
+	SearchFilter       string   `mapstructure:"search_filter"`
+	SearchBaseAttrs    []string `mapstructure:"search_base_attrs"`
+	DefaultUID         int      `mapstructure:"default_uid"`
+	DefaultGID         int      `mapstructure:"default_gid"`
+	ForceDefaultUID    bool     `mapstructure:"force_default_uid"`
+	ForceDefaultGID    bool     `mapstructure:"force_default_gid"`
+	InsecureSkipVerify bool     `mapstructure:"insecure_skip_verify"`
+	CACertificates     []string `mapstructure:"ca_certificates"`
+}
+
+type appConfig struct {
+	HTTPD HTTPDConfig `mapstructure:"httpd"`
+	LDAP  LDAPConfig  `mapstructure:"ldap"`
+}
+
+var conf appConfig
+
+func init() {
+	conf = appConfig{
+		HTTPD: HTTPDConfig{
+			BindAddress:        "",
+			BindPort:           9000,
+			AuthUserFile:       "",
+			CertificateFile:    "",
+			CertificateKeyFile: "",
+		},
+		LDAP: LDAPConfig{
+			BaseDN:       "dc=example,dc=com",
+			BindURL:      "ldap://192.168.1.103:389",
+			BindUsername: "cn=Directory Manager",
+			BindPassword: "YOUR_ADMIN_PASSWORD_HERE",
+			SearchFilter: "(&(objectClass=nsPerson)(uid=%s))",
+			SearchBaseAttrs: []string{
+				"dn",
+				"homeDirectory",
+				"uidNumber",
+				"gidNumber",
+				"nsSshPublicKey",
+			},
+			DefaultUID:         0,
+			DefaultGID:         0,
+			ForceDefaultUID:    true,
+			ForceDefaultGID:    true,
+			InsecureSkipVerify: false,
+			CACertificates:     nil,
+		},
+	}
+	viper.SetEnvPrefix(configEnvPrefix)
+	replacer := strings.NewReplacer(".", "__")
+	viper.SetEnvKeyReplacer(replacer)
+	viper.SetConfigName(DefaultConfigName)
+	viper.AutomaticEnv()
+	viper.AllowEmptyEnv(true)
+}
+
+// GetHomeDirectory returns the configured name for the LDAP field to use as home directory
+func (l *LDAPConfig) GetHomeDirectory() string {
+	if len(l.SearchBaseAttrs) > 1 {
+		return l.SearchBaseAttrs[1]
+	}
+	return "homeDirectory"
+}
+
+// GetUIDNumber returns the configured name for the LDAP field to use as UID
+func (l *LDAPConfig) GetUIDNumber() string {
+	if len(l.SearchBaseAttrs) > 2 {
+		return l.SearchBaseAttrs[2]
+	}
+	return "uidNumber"
+}
+
+// GetGIDNumber returns the configured name for the LDAP field to use as GID
+func (l *LDAPConfig) GetGIDNumber() string {
+	if len(l.SearchBaseAttrs) > 3 {
+		return l.SearchBaseAttrs[3]
+	}
+	return "gidNumber"
+}
+
+// GetPublicKey returns the configured name for the LDAP field to use as public keys
+func (l *LDAPConfig) GetPublicKey() string {
+	if len(l.SearchBaseAttrs) > 4 {
+		return l.SearchBaseAttrs[4]
+	}
+	return "nsSshPublicKey"
+}
+
+// GetHTTPDConfig returns the configuration for the HTTP server
+func GetHTTPDConfig() HTTPDConfig {
+	return conf.HTTPD
+}
+
+// GetLDAPConfig returns LDAP related settings
+func GetLDAPConfig() LDAPConfig {
+	return conf.LDAP
+}
+
+func getRedactedConf() appConfig {
+	c := conf
+	return c
+}
+
+// LoadConfig loads the configuration
+func LoadConfig(configDir, configName string) error {
+	var err error
+	viper.AddConfigPath(configDir)
+	viper.AddConfigPath(".")
+	viper.SetConfigName(configName)
+	if err = viper.ReadInConfig(); err != nil {
+		logger.Warn(logSender, "", "error loading configuration file: %v. Default configuration will be used: %+v",
+			err, getRedactedConf())
+		logger.WarnToConsole("error loading configuration file: %v. Default configuration will be used.", err)
+		return err
+	}
+	err = viper.Unmarshal(&conf)
+	if err != nil {
+		logger.Warn(logSender, "", "error parsing configuration file: %v. Default configuration will be used: %+v",
+			err, getRedactedConf())
+		logger.WarnToConsole("error parsing configuration file: %v. Default configuration will be used.", err)
+		return err
+	}
+	logger.Debug(logSender, "", "config file used: '%#v', config loaded: %+v", viper.ConfigFileUsed(), getRedactedConf())
+	return err
+}