File Transfer Protocol (FTP/SFTP)

Supported Protocols

When enabled, MinIO supports FTP access over the following protocols:

• SSH File Transfer Protocol (SFTP)

  SFTP is defined by the Internet Engineering Task Force (IETF) as an extension of SSH 2.0. SFTP allows file transfer over SSH for use with Transport Layer Security (TLS) and virtual private network (VPN) applications.

  Your FTP client must support SFTP.

• File Transfer Protocol over SSL/TLS (FTPS)

  FTPS allows for encrypted FTP communication with TLS certificates over the standard FTP communication channel. FTPS should not be confused with SFTP, as FTPS does not communicate over a Secure Shell (SSH).

  Your FTP client must support FTPS.

• File Transfer Protocol (FTP)

  Unencrypted file transfer.

  MinIO does not recommend using unencrypted FTP for file transfer.

Supported Commands

When enabled, MinIO supports the following FTP operations:

• get

• put

• ls

• mkdir

• rmdir

• delete

MinIO does not support either append or rename operations.

Versioning

SFTP clients can only operate on the latest version of an object. Specifically:

• For read operations, MinIO only returns the latest version of the requested object(s) to the FTP client.

• For write operations, MinIO applies normal versioning behavior and creates a new object version at the specified namespace. delete and rmdir operations create DeleteMarker objects.

Authentication and Access

FTP access requires the same authentication as any other S3 client. MinIO supports the following authentication providers:

• MinIO IDP users and their service accounts

• Active Directory/LDAP users and their service accounts

• OpenID/OIDC service accounts

STS credentials cannot access buckets or objects over FTP.

Authenticated users can access buckets and objects based on the policies assigned to the user or parent user account.

The FTP protocol does not require any of the admin:* permissions. The FTP protocols do not support any of the MinIO admin actions.

Connect to MinIO Using FTP

The following example connects to a server using minio credentials to list contents in a bucket named runner

> ftp localhost -P 8021
Connected to localhost.
220 Welcome to MinIO FTP Server
Name (localhost:user): minio
331 User name ok, password required
Password:
230 Password ok, continue
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls runner/
229 Entering Extended Passive Mode (|||39155|)
150 Opening ASCII mode data connection for file list
drwxrwxrwx 1 nobody nobody            0 Jan  1 00:00 chunkdocs/
drwxrwxrwx 1 nobody nobody            0 Jan  1 00:00 testdir/
...

Start MinIO with FTP over TLS (FTPS) Enabled

The following example starts MinIO with FTPS enabled.

minio server http://server{1...4}/disk{1...4} \
--ftp="address=:8021"                         \
--ftp="passive-port-range=30000-40000"        \
--ftp="tls-private-key=path/to/private.key"   \
--ftp="tls-public-cert=path/to/public.crt"    \
...

Download an Object over FTP

This example lists items in a bucket, then downloads the contents of the bucket.

> ftp localhost -P 8021
Connected to localhost.
220 Welcome to MinIO FTP Server
Name (localhost:user): minio
331 User name ok, password required
Password:
230 Password ok, continue
Remote system type is UNIX.
Using binary mode to transfer files.ftp> ls runner/chunkdocs/metadata
229 Entering Extended Passive Mode (|||44269|)
150 Opening ASCII mode data connection for file list
-rwxrwxrwx 1 nobody nobody           45 Apr  1 06:13 chunkdocs/metadata
226 Closing data connection, sent 75 bytes
ftp> get
(remote-file) runner/chunkdocs/metadata
(local-file) test
local: test remote: runner/chunkdocs/metadata
229 Entering Extended Passive Mode (|||37785|)
150 Data transfer starting 45 bytes
     45        3.58 KiB/s
226 Closing data connection, sent 45 bytes
45 bytes received in 00:00 (3.55 KiB/s)
...

Connect to MinIO Using SFTP

The following example connects to an SFTP server, lists the contents of a bucket named runner, and downloads an object.

> sftp -P 8022 minio@localhost
minio@localhost's password:
Connected to localhost.
sftp> ls runner/
chunkdocs  testdir
sftp> get runner/chunkdocs/metadata metadata
Fetching /runner/chunkdocs/metadata to metadata
metadata                               100%  226    16.6KB/s   00:00

Connect to MinIO Using SFTP with a Certificate Key File

MinIO supports mutual TLS (mTLS) certificate-based authentication on SFTP, where both the server and the client verify the authenticity of each other.

This type of authentication requires the following:

1. Public key file for the trusted certificate authority

2. Public key file for the MinIO Server minted and signed by the trusted certificate authority

3. Public key file for the user minted and signed by the trusted certificate authority for the client connecting by SFTP and located in the user’s .ssh folder (or equivalent for the operating system)

The keys must include a principals list of the user(s) that can authenticate with the key:

ssh-keygen -s ~/.ssh/ca_user_key -I miniouser -n miniouser -V +1h -z 1 miniouser1.pub

• -s specifies the path to the certificate authority public key to use for generating this key. The specified public key must have a principals list that includes this user.

• -I specifies the key identity for the public key.

• -n creates the user principals list for which this key is valid. You must include the user for which this key is valid, and the user must match the username in MinIO.

• -V limits the duration for which the generated key is valid. In this example, the key is valid for one hour. Adjust the duration for your requirements.

• -z adds a serial number to the key to distinguish this generated public key from other keys signed by the same certificate authority public key.

MinIO requires specifying the Certificate Authority used to sign the certificates for SFTP access. Start or restart the MinIO Server and specify the path to the trusted certificate authority’s public key using an --sftp="trusted-user-ca-key=PATH" flag:

minio server {path-to-server} --sftp="trusted-user-ca-key=/path/to/.ssh/ca_user_key.pub" {...other flags}

When connecting to the MinIO Server with SFTP, the client verifies the MinIO Server’s certificate. The client then passes its own certificate to the MinIO Server. The MinIO Server verifies the key created above by comparing its value to the the known public key from the certificate authority provided at server startup.

Once the MinIO Server verifies the client’s certificate, the user can connect to the MinIO server over SFTP:

sftp -P <SFTP port> <server IP>

Require service account or LDAP for authentication

To force authentication to SFTP using LDAP or service account credentials, append a suffix to the username. Valid suffixes are either =ldap or =svc.

> sftp -P 8022 my-ldap-user=ldap@[minio@localhost]:/bucket

> sftp -P 8022 my-ldap-user=svc@[minio@localhost]:/bucket

• Replace my-ldap-user with the username to use.

• Replace [minio@localhost] with the address of the MinIO server.