File Transfer Protocol (FTP/SFTP)

Supported Commands

When enabled, MinIO supports the following SFTP operations:

• get

• put

• ls

• mkdir

• rmdir

• delete

MinIO does not support either append or rename operations.

MinIO Operator only supports the SFTP file transfer protocol. Other protocols, such as FTP, are not supported for accessing Tenants.

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 SFTP client.

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

Authentication and Access

SFTP 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

• Certificate Key File

STS credentials cannot access buckets or objects over SFTP.

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

The SFTP protocol does not require any of the admin:* permissions. You may not perform other MinIO admin actions with SFTP.

Connect to MinIO Using SFTP

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

sftp -P 8022 my-access-key@localhost
my-access-key@localhost's password:
Connected to localhost.
sftp> ls
test-bucket
sftp> ls test-bucket
test-bucket/test-file.txt
sftp> get test-bucket/test-file.txt
Fetching /test-bucket/test-file.txt to test-file.txt
test-file.txt                    100%    6     1.3KB/s   00:00

Check if SFTP is Enabled for a Tenant

The following kubectl get command uses yq to display the value of enableSFTP, indicating whether SFTP is enabled:

kubectl get tenants/my-tenant -n my-tenant-ns -o yaml | yq '.spec.features'

Replace my-tenant and my-tenant-ns with the desired Tenant and namespace.

If SFTP is enabled, the output resembles the following:

enableSFTP: true

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.