How to secure access to MinIO server with TLS

This guide explains how to configure MinIO Server with TLS certificates on Linux and Windows platforms.

1. Install MinIO Server
2. Use an Existing Key and Certificate with MinIO
3. Generate and use Self-signed Keys and Certificates with MinIO
4. Install Certificates from Third-party CAs

1. Install MinIO Server

Install MinIO Server using the instructions in the MinIO Quickstart Guide.

2. Use an Existing Key and Certificate with MinIO

This section describes how to use a private key and public certificate that have been obtained from a certificate authority (CA). If these files have not been obtained, skip to 3. Generate Self-signed Certificates or generate them with Let's Encrypt using these instructions: Generate Let's Encrypt certificate using Certbot for MinIO. For more about TLS and certificates in MinIO, see the Network Encryption documentation.

Copy the existing private key and public certificate to the certs directory. The default certs directory is:

• Linux: ${HOME}/.minio/certs
• Windows: %%USERPROFILE%%\.minio\certs

Note:

• Location of custom certs directory can be specified using --certs-dir command line option.
• Inside the certs directory, the private key must by named private.key and the public key must be named public.crt.
• A certificate signed by a CA contains information about the issued identity (e.g. name, expiry, public key) and any intermediate certificates. The root CA is not included.

3. Generate and use Self-signed Keys and Certificates with MinIO

This section describes how to generate a self-signed certificate using various tools:

• 3.1 Use certgen to Generate a Certificate
• 3.2 Use OpenSSL to Generate a Certificate
• 3.3 Use OpenSSL (with IP address) to Generate a Certificate
• 3.4 Use GnuTLS (for Windows) to Generate a Certificate

Note:

• MinIO only supports keys and certificates in PEM format on Linux and Windows.
• MinIO doesn't currently support PFX certificates.

3.1 Use certgen to Generate a Certificate

Download certgen for your specific operating system and platform.

certgen is a simple Go tool to generate self-signed certificates, and provides SAN certificates with DNS and IP entries:

./certgen -host "10.10.0.3,10.10.0.4,10.10.0.5"

A response similar to this one should be displayed:

2018/11/21 10:16:18 wrote public.crt
2018/11/21 10:16:18 wrote private.key

3.2 Use OpenSSL to Generate a Certificate

Use one of the following methods to generate a certificate using openssl:

• 3.2.1 Generate a private key with ECDSA
• 3.2.2 Generate a private key with RSA
• 3.2.3 Generate a self-signed certificate

3.2.1 Generate a private key with ECDSA

Use the following command to generate a private key with ECDSA:

openssl ecparam -genkey -name prime256v1 | openssl ec -out private.key

A response similar to this one should be displayed:

read EC key
writing EC key

Alternatively, use the following command to generate a private ECDSA key protected by a password:

openssl ecparam -genkey -name prime256v1 | openssl ec -aes256 -out private.key -passout pass:PASSWORD

3.2.2 Generate a private key with RSA

Use the following command to generate a private key with RSA:

openssl genrsa -out private.key 2048

A response similar to this one should be displayed:

Generating RSA private key, 2048 bit long modulus
............................................+++
...........+++
e is 65537 (0x10001)

Alternatively, use the following command to generate a private RSA key protected by a password:

openssl genrsa -aes256 -passout pass:PASSWORD -out private.key 2048

Note: When using a password-protected private key, the password must be provided through the environment variable MINIO_CERT_PASSWD using the following command:

export MINIO_CERT_PASSWD=<PASSWORD>

The default OpenSSL format for private encrypted keys is PKCS-8, but MinIO only supports PKCS-1. An RSA key that has been formatted with PKCS-8 can be converted to PKCS-1 using the following command:

openssl rsa -in private-pkcs8-key.key -aes256 -passout pass:PASSWORD -out private.key

3.2.3 Generate a self-signed certificate

Create a file named openssl.conf with the content below. Set IP.1 and/or DNS.1 to point to the correct IP/DNS addresses:

[req]
distinguished_name = req_distinguished_name
x509_extensions = v3_req
prompt = no

[req_distinguished_name]
C = US
ST = VA
L = Somewhere
O = MyOrg
OU = MyOU
CN = MyServerName

[v3_req]
subjectAltName = @alt_names

[alt_names]
IP.1 = 127.0.0.1
DNS.1 = localhost

Run openssl by specifying the configuration file and enter a passphrase if prompted:

openssl req -new -x509 -nodes -days 730 -keyout private.key -out public.crt -config openssl.conf

3.3 Use GnuTLS (for Windows) to Generate a Certificate

This section describes how to use GnuTLS on Windows to generate a certificate.

3.3.1 Install and configure GnuTLS

Download and decompress the Windows version of GnuTLS from here.

Use PowerShell to add the path of the extracted GnuTLS binary to the system path:

setx path "%path%;C:\Users\MyUser\Downloads\gnutls-3.4.9-w64\bin"

Note: PowerShell may need to be restarted for this change to take effect.

3.3.2 Generate a private key

Run the following command to generate a private .key file:

certtool.exe --generate-privkey --outfile private.key

A response similar to this one should be displayed:

Generating a 3072 bit RSA private key...

3.3.3 Generate a public certificate

Create a file called cert.cnf with the content below. This file contains all of the information necessary to generate a certificate using certtool.exe:

# X.509 Certificate options
#
# DN options

# The organization of the subject.
organization = "Example Inc."

# The organizational unit of the subject.
#unit = "sleeping dept."

# The state of the certificate owner.
state = "Example"

# The country of the subject. Two letter code.
country = "EX"

# The common name of the certificate owner.
cn = "Sally Certowner"

# In how many days, counting from today, this certificate will expire.
expiration_days = 365

# X.509 v3 extensions

# DNS name(s) of the server
dns_name = "localhost"

# (Optional) Server IP address
ip_address = "127.0.0.1"

# Whether this certificate will be used for a TLS server
tls_www_server

Run certtool.exe and specify the configuration file to generate a certificate:

certtool.exe --generate-self-signed --load-privkey private.key --template cert.cnf --outfile public.crt

4. Install Certificates from Third-party CAs

MinIO can connect to other servers, including MinIO nodes or other server types such as NATs and Redis. If these servers use certificates that were not registered with a known CA, add trust for these certificates to MinIO Server by placing these certificates under one of the following MinIO configuration paths:

• Linux: ~/.minio/certs/CAs/
• Windows: C:\Users\<Username>\.minio\certs\CAs

Explore Further

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• MinIO Client Complete Guide
• MinIO Network Encryption Overview
• Generate Let's Encrypt Certificate
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