SFTPGo

Full featured and highly configurable SFTP server software

Features

• Each account is chrooted to his Home Dir
• SFTP accounts are virtual accounts stored in a "data provider"
• SQLite, MySQL and PostgreSQL data providers are supported. The Provider interface could be extended to support non SQL backends too
• Public key and password authentication
• Quota support: accounts can have individual quota expressed as max number of files and max total size
• Bandwidth throttling is supported, with distinct settings for upload and download
• Per user maximum concurrent sessions
• Per user permissions: list directories content, upload, download, delete, rename, create directories, create symlinks can be enabled or disabled
• Per user files/folders ownership: you can map all the users to the system account that runs SFTPGo (all platforms are supported) or you can run SFTPGo as root user and map each user or group of users to a different system account (*NIX only)
• Configurable custom commands and/or HTTP notifications on SFTP upload, download, delete or rename
• REST API for users and quota management and real time reports for the active connections with possibility of forcibly closing a connection
• Log files are accurate and they are saved in the easily parsable JSON format
• Automatically terminating idle connections
• Atomic uploads are supported

Platforms

SFTPGo is developed and tested on Linux. After each commit the code is automatically built and tested on Linux and macOS using Travis CI. Regularly the test cases are manually executed and pass on Windows. Other UNIX variants such as *BSD should work too.

Requirements

• Go 1.12 or higher
• A suitable SQL server to use as data provider: PostreSQL (9+) or MySQL (5.6+) or SQLite 3.x

Installation

Simple install the package to your $GOPATH with the go tool from shell:

$ go get -u github.com/drakkan/sftpgo

Make sure Git is installed on your machine and in your system's PATH.

Version info can be embedded populating the following variables at build time:

• github.com/drakkan/sftpgo/utils.commit
• github.com/drakkan/sftpgo/utils.date

For example you can build using the following command:

go build -i -ldflags "-s -w -X github.com/drakkan/sftpgo/utils.commit=`git describe --tags --always --dirty` -X github.com/drakkan/sftpgo/utils.date=`date --utc +%FT%TZ`" -o sftpgo

and you will get a version that includes git commit and build date like this one:

./sftpgo -v
SFTPGo version: 0.9.0-dev-90607d4-dirty-2019-08-08T19:28:36Z

A systemd sample service can be found inside the source tree.

Alternately you can use distro packages:

• Arch Linux PKGBUILD is available on AUR

Configuration

The sftpgo executable can be used this way:

Usage:
  sftpgo [command]

Available Commands:
  help        Help about any command
  serve       Start the SFTP Server

Flags:
  -h, --help      help for sftpgo
  -v, --version

The serve subcommand supports the following flags:

• --config-dir string. Location of the config dir. This directory should contain the sftpgo configuration file and is used as the base for files with a relative path (eg. the private keys for the SFTP server, the SQLite database if you use SQLite as data provider). The default value is "." or the value of SFTPGO_CONFIG_DIR environment variable.
• --config-file string. Name of the configuration file. It must be the name of a file stored in config-dir not the absolute path to the configuration file. The specified file name must have no extension we automatically load JSON, YAML, TOML, HCL and Java properties. The default value is "sftpgo" (and therefore sftpgo.json, sftpgo.yaml and so on are searched) or the value of SFTPGO_CONFIG_FILE environment variable
• --log-compress boolean. Determine if the rotated log files should be compressed using gzip. Default false or the value of SFTPGO_LOG_COMPRESS environment variable (1 or true, 0 or false)
• --log-file-path string. Location for the log file, default "sftpgo.log" or the value of SFTPGO_LOG_FILE_PATH environment variable
• --log-max-age int. Maximum number of days to retain old log files. Default 28 or the value of SFTPGO_LOG_MAX_AGE environment variable
• --log-max-backups int. Maximum number of old log files to retain. Default 5 or the value of SFTPGO_LOG_MAX_BACKUPS environment variable
• --log-max-size int. Maximum size in megabytes of the log file before it gets rotated. Default 10 or the value of SFTPGO_LOG_MAX_SIZE environment variable
• --log-verbose boolean. Enable verbose logs. Default true or the value of SFTPGO_LOG_VERBOSE environment variable (1 or true, 0 or false)

If you don't configure any private host keys, the daemon will use id_rsa in the configuration directory. If that file doesn't exist, the daemon will attempt to autogenerate it (if the user that executes SFTPGo has write access to the config-dir). The server supports any private key format supported by crypto/ssh.

Before starting sftpgo a dataprovider must be configured.

Sample SQL scripts to create the required database structure can be found inside the source tree sql directory. The SQL scripts filename's is, by convention, the date as YYYYMMDD and the suffix .sql. You need to apply all the SQL scripts for your database ordered by name, for example 20190706.sql must be applied before 20190728.sql and so on.

The sftpgo configuration file contains the following sections:

• "sftpd", the configuration for the SFTP server
  • bind_port, integer. The port used for serving SFTP requests. Default: 2022
  • bind_address, string. Leave blank to listen on all available network interfaces. Default: ""
  • idle_timeout, integer. Time in minutes after which an idle client will be disconnected. Default: 15
  • max_auth_tries integer. Maximum number of authentication attempts permitted per connection. If set to a negative number, the number of attempts are unlimited. If set to zero, the number of attempts are limited to 6.
  • umask, string. Umask for the new files and directories. This setting has no effect on Windows. Default: "0022"
  • banner, string. Identification string used by the server. Default "SFTPGo"
  • upload_mode int. 0 means standard, the files are uploaded directly to the requested path. 1 means atomic: the files are uploaded to a temporary path and renamed to the requested path when the client ends the upload. Atomic mode avoid problems such as a web server that serves partial files when the files are being uploaded
  • actions, struct. It contains the command to execute and/or the HTTP URL to notify and the trigger conditions
    • execute_on, list of strings. Valid values are download, upload, delete, rename. On folder deletion a delete notification will be sent for each deleted file. Leave empty to disable actions.
    • command, string. Absolute path to the command to execute. Leave empty to disable. The command is invoked with the following arguments:
      • action, any valid execute_on string
      • username, user who did the action
      • path to the affected file. For rename action this is the old file name
      • target_path, non empty for rename action, this is the new file name
    • http_notification_url, a valid URL. An HTTP GET request will be executed to this URL. Leave empty to disable. The query string will contain the following parameters that have the same meaning of the command's arguments:
      • action
      • username
      • path
      • target_path, added for rename action only
  • keys, struct array. It contains the daemon's private keys. If empty or missing the daemon will search or try to generate id_rsa in the configuration directory.
    • private_key, path to the private key file. It can be a path relative to the config dir or an absolute one.
• "data_provider", the configuration for the data provider
  • driver, string. Supported drivers are sqlite, mysql, postgresql
  • name, string. Database name. For driver sqlite this can be the database name relative to the config dir or the absolute path to the SQLite database.
  • host, string. Database host. Leave empty for driver sqlite
  • port, integer. Database port. Leave empty for driver sqlite
  • username, string. Database user. Leave empty for driver sqlite
  • password, string. Database password. Leave empty for driver sqlite
  • sslmode, integer. Used for drivers mysql and postgresql. 0 disable SSL/TLS connections, 1 require ssl, 2 set ssl mode to verify-ca for driver postgresql and skip-verify for driver mysql, 3 set ssl mode to verify-full for driver postgresql and preferred for driver mysql
  • connectionstring, string. Provide a custom database connection string. If not empty this connection string will be used instead of build one using the previous parameters
  • users_table, string. Database table for SFTP users
  • manage_users, integer. Set to 0 to disable users management, 1 to enable
  • track_quota, integer. Set the preferred way to track users quota between the following choices:
    • 0, disable quota tracking. REST API to scan user dir and update quota will do nothing
    • 1, quota is updated each time a user upload or delete a file even if the user has no quota restrictions
    • 2, quota is updated each time a user upload or delete a file but only for users with quota restrictions. With this configuration the "quota scan" REST API can still be used to periodically update space usage for users without quota restrictions
• "httpd", the configuration for the HTTP server used to serve REST API
  • bind_port, integer. The port used for serving HTTP requests. Set to 0 to disable HTTP server. Default: 8080
  • bind_address, string. Leave blank to listen on all available network interfaces. Default: "127.0.0.1"

Here is a full example showing the default config in json format:

{
  "sftpd": {
    "bind_port": 2022,
    "bind_address": "",
    "idle_timeout": 15,
    "max_auth_tries": 0,
    "umask": "0022",
    "banner": "SFTPGo",
    "actions": {
      "execute_on": [],
      "command": "",
      "http_notification_url": ""
    },
    "keys": []
  },
  "data_provider": {
    "driver": "sqlite",
    "name": "sftpgo.db",
    "host": "",
    "port": 5432,
    "username": "",
    "password": "",
    "sslmode": 0,
    "connection_string": "",
    "users_table": "users",
    "manage_users": 1,
    "track_quota": 2
  },
  "httpd": {
    "bind_port": 8080,
    "bind_address": "127.0.0.1"
  }
}

If you want to use a private key that use an algorithm different from RSA or more than one private key then replace the empty keys array with something like this:

"keys": [
  {
    "private_key": "id_rsa"
  },
  {
    "private_key": "id_ecdsa"
  }
]

The configuration can be read from JSON, TOML, YAML, HCL, envfile and Java properties config files, if your config-file flag is set to sftpgo (default value) you need to create a configuration file called sftpgo.json or sftpgo.yaml and so on inside config-dir.

You can also configure all the available options using environment variables, sftpgo will check for environment variables with a name matching the key uppercased and prefixed with the SFTPGO_. You need to use __ to traverse a struct.

Let's see some examples:

• To set sftpd bind_port you need to define the env var SFTPGO_SFTPD__BIND_PORT
• To set the execute_on actions you need to define the env var SFTPGO_SFTPD__ACTIONS__EXECUTE_ON for example SFTPGO_SFTPD__ACTIONS__EXECUTE_ON=upload,download

To start the SFTP Server with the default values for the command line flags simply use:

sftpgo serve

Account's configuration properties

For each account the following properties can be configured:

• username
• password used for password authentication. For users created using SFTPGo REST API the password will be stored using argon2id hashing algo. SFTPGo supports checking passwords stored with bcrypt too. Currently, as fallback, there is a clear text password checking but you should not store passwords as clear text and this support could be removed at any time, so please don't depend on it.
• public_keys array of public keys. At least one public key or the password is mandatory.
• home_dir The user cannot upload or download files outside this directory. Must be an absolute path
• uid, gid. If sftpgo runs as root system user then the created files and directories will be assigned to this system uid/gid. Ignored on windows and if sftpgo runs as non root user: in this case files and directories for all SFTP users will be owned by the system user that runs sftpgo.
• max_sessions maximum concurrent sessions. 0 means unlimited
• quota_size maximum size allowed as bytes. 0 means unlimited
• quota_files maximum number of files allowed. 0 means unlimited
• permissions the following permissions are supported:
  • * all permission are granted
  • list list items is allowed
  • download download files is allowed
  • upload upload files is allowed
  • delete delete files or directories is allowed
  • rename rename files or directories is allowed
  • create_dirs create directories is allowed
  • create_symlinks create symbolic links is allowed
• upload_bandwidth maximum upload bandwidth as KB/s, 0 means unlimited
• download_bandwidth maximum download bandwidth as KB/s, 0 means unlimited

These properties are stored inside the data provider. If you want to use your existing accounts, you can create a database view. Since a view is read only, you have to disable user management and quota tracking so SFTPGo will never try to write to the view.

REST API

SFTPGo exposes REST API to manage users and quota and to get real time reports for the active connections with possibility of forcibly closing a connection.

If quota tracking is enabled in sftpgo configuration file, then the used size and number of files are updated each time a file is added/removed. If files are added/removed not using SFTP or if you change track_quota from 2 to 1, you can rescan the user home dir and update the used quota using the REST API.

REST API is designed to run on localhost or on a trusted network, if you need HTTPS or authentication you can setup a reverse proxy using an HTTP Server such as Apache or NGNIX.

For example you can keep SFTPGo listening on localhost and expose it externally configuring a reverse proxy using Apache HTTP Server this way:

ProxyPass /api/v1 http://127.0.0.1:8080/api/v1
ProxyPassReverse /api/v1 http://127.0.0.1:8080/api/v1

and you can add authentication with something like this:

<Location /api/v1>
	AuthType Digest
	AuthName "Private"
	AuthDigestDomain "/api/v1"
	AuthDigestProvider file
	AuthUserFile "/etc/httpd/conf/auth_digest"
	Require valid-user
</Location>

and, of course, you can configure the web server to use HTTPS.

The OpenAPI 3 schema for the exposed API can be found inside the source tree: openapi.yaml.

A sample CLI client for the REST API can be found inside the source tree scripts directory.

You can also generate your own REST client, in your preferred programming language or even bash scripts, using an OpenAPI generator such as swagger-codegen or OpenAPI Generator

Logs

Inside the log file each line is a JSON struct, each struct has a sender fields that identify the log type.

The logs can be divided into the following categories:

• "app logs", internal logs used to debug sftpgo:
  • sender string. This is generally the package name that emits the log
  • time string. Date/time with millisecond precision
  • level string
  • message string
• "transfer logs", SFTP transfer logs:
  • sender string. SFTPUpload or SFTPDownload
  • time string. Date/time with millisecond precision
  • level string
  • elapsed_ms, int64. Elapsed time, as milliseconds, for the upload/download
  • size_bytes, int64. Size, as bytes, of the download/upload
  • username, string
  • file_path string
  • connection_id string. Unique SFTP connection identifier
• "command logs", SFTP command logs:
  • sender string. SFTPRename, SFTPRmdir, SFTPMkdir, SFTPSymlink, SFTPRemove
  • level string
  • username, string
  • file_path string
  • target_path string
  • connection_id string. Unique SFTP connection identifier
• "http logs", REST API logs:
  • sender string. httpd
  • level string
  • remote_addr string. IP and port of the remote client
  • proto string, for example HTTP/1.1
  • method string. HTTP method (GET, POST, PUT, DELETE etc.)
  • user_agent string
  • uri string. Full uri
  • resp_status integer. HTTP response status code
  • resp_size integer. Size in bytes of the HTTP response
  • elapsed_ms int64. Elapsed time, as milliseconds, to complete the request
  • request_id string. Unique request identifier

Acknowledgements

• pkg/sftp
• go-chi
• zerolog
• lumberjack
• argon2id
• go-sqlite3
• go-sql-driver/mysql
• lib/pq
• viper
• cobra

Some code was initially taken from Pterodactyl sftp server

License

GNU GPLv3