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Certificate-Based Authentication for Login

TiDB supports a certificate-based authentication method for users to log into TiDB. With this method, TiDB issues certificates to different users, uses encrypted connections to transfer data, and verifies certificates when users log in. This approach is more secure than the traditional password-based authentication method commonly used by MySQL users and is thus adopted by an increasing number of users.

To use certificate-based authentication, you might need to perform the following operations:

  • Create security keys and certificates
  • Configure certificates for TiDB and the client
  • Configure the user certificate information to be verified when the user logs in
  • Update and replace certificates

The rest of the document introduces in detail how to perform these operations.

Create security keys and certificates

It is recommended that you use OpenSSL to create keys and certificates. The certificate generation process is similar to the process described in Enable TLS Between TiDB Clients and Servers. The following paragraphs demonstrate how to configure more attribute fields that need to be verified in the certificate.

Generate CA key and certificate

  1. Execute the following command to generate the CA key:

    sudo openssl genrsa 2048 > ca-key.pem

    The output of the above command:

    Generating RSA private key, 2048 bit long modulus (2 primes)
....................+++++
...............................................+++++
e is 65537 (0x010001)

  2. Execute the following command to generate the certificate corresponding to the CA key:

    sudo openssl req -new -x509 -nodes -days 365000 -key ca-key.pem -out ca-cert.pem

  3. Enter detailed certificate information. For example:

    Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:California
Locality Name (e.g. city) []:San Francisco
Organization Name (e.g. company) [Internet Widgits Pty Ltd]:PingCAP Inc.
Organizational Unit Name (e.g. section) []:TiDB
Common Name (e.g. server FQDN or YOUR name) []:TiDB admin
Email Address []:s@pingcap.com

Generate server key and certificate

  1. Execute the following command to generate the server key:

    sudo openssl req -newkey rsa:2048 -days 365000 -nodes -keyout server-key.pem -out server-req.pem

  2. Enter detailed certificate information. For example:

    Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:California
Locality Name (e.g. city) []:San Francisco
Organization Name (e.g. company) [Internet Widgits Pty Ltd]:PingCAP Inc.
Organizational Unit Name (e.g. section) []:TiKV
Common Name (e.g. server FQDN or YOUR name) []:TiKV Test Server
Email Address []:k@pingcap.com

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

  3. Execute the following command to generate the RSA key of the server:

    sudo openssl rsa -in server-key.pem -out server-key.pem

    The output of the above command:

    writing RSA key

  4. Use the CA certificate signature to generate the signed server certificate:

    sudo openssl x509 -req -in server-req.pem -days 365000 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out server-cert.pem

    The output of the above command (for example):

    Signature ok
subject=C = US, ST = California, L = San Francisco, O = PingCAP Inc., OU = TiKV, CN = TiKV Test Server, emailAddress = k@pingcap.com
Getting CA Private Key

Generate client key and certificate

After generating the server key and certificate, you need to generate the key and certificate for the client. It is often necessary to generate different keys and certificates for different users.

  1. Execute the following command to generate the client key:

    sudo openssl req -newkey rsa:2048 -days 365000 -nodes -keyout client-key.pem -out client-req.pem

  2. Enter detailed certificate information. For example:

    Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:California
Locality Name (e.g. city) []:San Francisco
Organization Name (e.g. company) [Internet Widgits Pty Ltd]:PingCAP Inc.
Organizational Unit Name (e.g. section) []:TiDB
Common Name (e.g. server FQDN or YOUR name) []:tpch-user1
Email Address []:zz@pingcap.com

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

  3. Execute the following command to generate the RSA key of the client:

    sudo openssl rsa -in client-key.pem -out client-key.pem

    The output of the above command:

    writing RSA key

  4. Use the CA certificate signature to generate the client certificate:

    sudo openssl x509 -req -in client-req.pem -days 365000 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out client-cert.pem

    The output of the above command (for example):

    Signature ok
subject=C = US, ST = California, L = San Francisco, O = PingCAP Inc., OU = TiDB, CN = tpch-user1, emailAddress = zz@pingcap.com
Getting CA Private Key

Verify certificate

Execute the following command to verify certificate:

openssl verify -CAfile ca-cert.pem server-cert.pem client-cert.pem

If the certificate is verified, you will see the following result:

server-cert.pem: OK
client-cert.pem: OK

Configure TiDB and the client to use certificates

After generating the certificates, you need to configure the TiDB server and the client to use the corresponding server certificate or client certificate.

Configure TiDB to use server certificate

Modify the [security] section in the TiDB configuration file. This step specifies the directory in which the CA certificate, the server key, and the server certificate are stored. You can replace path/to/server-cert.pem, path/to/server-key.pem, path/to/ca-cert.pem with your own directory.

[security]
ssl-cert ="path/to/server-cert.pem"
ssl-key ="path/to/server-key.pem"
ssl-ca="path/to/ca-cert.pem"

Start TiDB and check logs. If the following information is displayed in the log, the configuration is successful:

[INFO] [server.go:286] ["mysql protocol server secure connection is enabled"] ["client verification enabled"=true]

Configure the client to use client certificate

Configure the client so that the client uses the client key and certificate for login.

Taking the MySQL client as an example, you can use the newly created client certificate, client key and CA by specifying ssl-cert, ssl-key, and ssl-ca:

mysql -utest -h0.0.0.0 -P4000 --ssl-cert /path/to/client-cert.new.pem --ssl-key /path/to/client-key.new.pem --ssl-ca /path/to/ca-cert.pem

Configure the user certificate information for login verification

First, connect TiDB using the client to configure the login verification. Then, you can get and configure the user certificate information to be verified.

Get user certificate information

The user certificate information can be specified by REQUIRE SUBJECT, REQUIRE ISSUER, REQUIRE SAN, and REQUIRE CIPHER, which are used to check the X.509 certificate attributes.

  • REQUIRE SUBJECT: Specifies the subject information of the client certificate when you log in. With this option specified, you do not need to configure require ssl or x509. The information to be specified is consistent with the entered subject information in Generate client keys and certificates.

    To get this option, execute the following command:

    openssl x509 -noout -subject -in client-cert.pem | sed 's/.\{8\}//'  | sed 's/, /\//g' | sed 's/ = /=/g' | sed 's/^/\//'

  • require issuer: Specifies the subject information of the CA certificate that issues the user certificate. The information to be specified is consistent with the entered subject information in Generate CA key and certificate.

    To get this option, execute the following command:

    openssl x509 -noout -subject -in ca-cert.pem | sed 's/.\{8\}//'  | sed 's/, /\//g' | sed 's/ = /=/g' | sed 's/^/\//'

  • require san: Specifies the Subject Alternative Name information of the CA certificate that issues the user certificate. The information to be specified is consistent with the alt_names of the openssl.cnf configuration file used to generate the client certificate.

    • Execute the following command to get the information of the REQUIRE SAN item in the generated certificate:

      openssl x509 -noout -extensions subjectAltName -in client.crt

    • REQUIRE SAN currently supports the following Subject Alternative Name check items:

      • URI
      • IP
      • DNS

    • Multiple check items can be configured after they are connected by commas. For example, configure REQUIRE SAN as follows for the u1 user:

      CREATE USER 'u1'@'%' REQUIRE SAN 'DNS:d1,URI:spiffe://example.org/myservice1,URI:spiffe://example.org/myservice2';

      The above configuration only allows the u1 user to log in to TiDB using the certificate with the URI item spiffe://example.org/myservice1 or spiffe://example.org/myservice2 and the DNS item d1.

  • REQUIRE CIPHER: Checks the cipher method supported by the client. Use the following statement to check the list of supported cipher methods:

    SHOW SESSION STATUS LIKE 'Ssl_cipher_list';

Configure user certificate information

After getting the user certificate information (REQUIRE SUBJECT, REQUIRE ISSUER, REQUIRE SAN, REQUIRE CIPHER), configure these information to be verified when creating a user, granting privileges, or altering a user. Replace <replaceable> with the corresponding information in the following statements.

You can configure one option or multiple options using the space or and as the separator.

  • Configure user certificate when creating a user (CREATE USER):

    CREATE USER 'u1'@'%' REQUIRE ISSUER '<replaceable>' SUBJECT '<replaceable>' SAN '<replaceable>' CIPHER '<replaceable>';

  • Configure user certificate when altering a user:

    ALTER USER 'u1'@'%' REQUIRE ISSUER '<replaceable>' SUBJECT '<replaceable>' SAN '<replaceable>' CIPHER '<replaceable>';

After the above configuration, the following items will be verified when you log in:

  • SSL is used; the CA that issues the client certificate is consistent with the CA configured in the server.
  • The issuer information of the client certificate matches the information specified in REQUIRE ISSUER.
  • The subject information of the client certificate matches the information specified in REQUIRE CIPHER.
  • The Subject Alternative Name information of the client certificate matches the information specified in REQUIRE SAN.

You can log into TiDB only after all the above items are verified. Otherwise, the ERROR 1045 (28000): Access denied error is returned. You can use the following command to check the TLS version, the cipher algorithm and whether the current connection uses the certificate for the login.

Connect the MySQL client and execute the following statement:

\s

The output:

--------------
mysql  Ver 8.5.0 for Linux on x86_64 (MySQL Community Server - GPL)

Connection id:       1
Current database:    test
Current user:        root@127.0.0.1
SSL:                 Cipher in use is TLS_AES_128_GCM_SHA256

Then execute the following statement:

SHOW VARIABLES LIKE '%ssl%';

The output:

+---------------+----------------------------------+
| Variable_name | Value                            |
+---------------+----------------------------------+
| have_openssl  | YES                              |
| have_ssl      | YES                              |
| ssl_ca        | /path/to/ca-cert.pem             |
| ssl_cert      | /path/to/server-cert.pem         |
| ssl_cipher    |                                  |
| ssl_key       | /path/to/server-key.pem          |
+---------------+----------------------------------+
6 rows in set (0.06 sec)

Update and replace certificate

The key and certificate are updated regularly. The following sections introduce how to update the key and certificate.

The CA certificate is the basis for mutual verification between the client and server. To replace the CA certificate, generate a combined certificate that supports the authentication for both old and new certificates. On the client and server, first replace the CA certificate, then replace the client/server key and certificate.

Update CA key and certificate

  1. Back up the old CA key and certificate (suppose that ca-key.pem is stolen):

    mv ca-key.pem ca-key.old.pem && \
mv ca-cert.pem ca-cert.old.pem

  2. Generate the new CA key:

    sudo openssl genrsa 2048 > ca-key.pem

  3. Generate the new CA certificate using the newly generated CA key:

    sudo openssl req -new -x509 -nodes -days 365000 -key ca-key.pem -out ca-cert.new.pem

  4. Generate the combined CA certificate:

    cat ca-cert.new.pem ca-cert.old.pem > ca-cert.pem

After the above operations, restart the TiDB server with the newly created combined CA certificate. Then the server accepts both the new and old CA certificates.

Also replace the old CA certificate with the combined certificate so that the client accepts both the old and new CA certificates.

Update client key and certificate

  1. Generate the new RSA key of the client:

    sudo openssl req -newkey rsa:2048 -days 365000 -nodes -keyout client-key.new.pem -out client-req.new.pem && \
sudo openssl rsa -in client-key.new.pem -out client-key.new.pem

  2. Use the combined certificate and the new CA key to generate the new client certificate:

    sudo openssl x509 -req -in client-req.new.pem -days 365000 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out client-cert.new.pem

  3. Make the client (for example, MySQL) connect TiDB with the new client key and certificate:

    mysql -utest -h0.0.0.0 -P4000 --ssl-cert /path/to/client-cert.new.pem --ssl-key /path/to/client-key.new.pem --ssl-ca /path/to/ca-cert.pem

Update the server key and certificate

  1. Generate the new RSA key of the server:

    sudo openssl req -newkey rsa:2048 -days 365000 -nodes -keyout server-key.new.pem -out server-req.new.pem && \
sudo openssl rsa -in server-key.new.pem -out server-key.new.pem

  2. Use the combined CA certificate and the new CA key to generate the new server certificate:

    sudo openssl x509 -req -in server-req.new.pem -days 365000 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out server-cert.new.pem

  3. Configure the TiDB server to use the new server key and certificate. See Configure TiDB server for details.

Policy-based access control for certificates

TiDB supports policy-based access control (PBAC) for certificates, leveraging policies defined by the underlying key management server. This enables fine-grained control over access based on various criteria, such as time-based policies (for example, certificates only valid during specific hours), location-based policies (for example, restricting access to certain geographic locations), and other customizable conditions, ensuring enhanced security and flexibility in certificate management.

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