Connecting

Overview

Connection is done by many exchanges:

Initial Handshake Packet

  • int<1> protocol version.

  • string server version

    • MariaDB Server 10.X versions are by default prefixed "5.5.5-".

    • MariaDB 11.0 and later versions do not have a "5.5.5-" default prefix.

  • int<4> connection id.

  • string<8> authentication plugin data (1st part).

  • string<1> reserved byte.

  • int<2> server capabilities (1st part).

  • int<1> server default collation.

  • int<2> status flags.

  • int<2> server capabilities (2nd part).

  • If (server_capabilities & PLUGIN_AUTH):

  • Else:

  • string<6> filler.

  • If (server_capabilities & CLIENT_MYSQL):

  • Else:

    • int<4> server capabilities 3rd part . MariaDB specific flags /* MariaDB 10.2 or later */.

  • If (server_capabilities & CLIENT_SECURE_CONNECTION):

    • string authentication plugin data 2nd part . Length = max(12, plugin data length - 9).

    • string<1> reserved byte.

  • If (server_capabilities & PLUGIN_AUTH):

    • string authentication plugin name.

Client Handshake Response

If the client requests a TLS/SSL connection, the first response is an SSL connection request packet, followed by a handshake response packet. If no TLS is required, client directly sends a handshake response packet.

SSLRequest Packet

  • int<4> client capabilities.

  • int<4> max packet size.

  • int<1> client's default character set and collation.

  • string<19> reserved.

  • If not (server_capabilities & CLIENT_MYSQL):

    • int<4> extended client capabilities

  • Else:

ZERO-CONFIGURATION SSL ENCRYPTION

Automatic Encrypted Connections (MariaDB 11.4+):

Previously, failed SSL connections due to self-signed certificates prevented communication. MariaDB 11.4+ introduces a secondary validation method that works for all servers.

What Happens When SSL Validation Fails?

Even without a valid SSL certificate, the connector can still authenticate by remembering the server's fingerprint (unique identifier). However, it needs to confirm the connection is secure.

Verifying a Secure Connection:

The confirmation method depends on the connection type. When using secure MitM-proof methods, like Unix sockets, connector can automatically validate the connection. Otherwise, a shared secret is used.

Shared Secret for Secure Connection:

The shared secret is only used if the authentication plugin password is hashable (for instance, mysql_native_password , client_ed25519, or parsec) and not empty.

It's calculated by hashing the user's hash password with the authentication seed and the server fingerprint.

Password hash is generated depending on authentication plugin:

  • ed25519 : identical to password encryption.

  • mysql_native_password : identical to password encryption.

  • parsec: ext-salt + raw ed25519 public key.

Server 11.4+ Confirmation Details:

For servers running MariaDB 11.4 or later, the final confirmation packet contains:

  • int<1> encryption (actually only 0x01 = SHA256 encryption)

  • byte shared secret.

Matching the Shared Secret

If the calculated shared secret matches the received one, the SSL connection is considered valid (host validation is not needed). Otherwise, the connection must be closed for security reasons.

Handshake Response Packet

  • int<4> client capabilities.

  • int<4> max packet size.

  • int<1> client's default character set and collation.

  • string<19> reserved.

  • If not (server_capabilities & CLIENT_MYSQL):

    • int<4> extended client capabilities.

  • Else:

  • string username.

  • If (password):

    • If (server_capabilities & PLUGIN_AUTH_LENENC_CLIENT_DATA):

    • Else if (server_capabilities & CLIENT_SECURE_CONNECTION):

      • int<1> length of authentication response.

      • string authentication response (length is indicated by previous field).

    • Else:

      • string authentication response null ended.

  • Else:

    • string<1>\0 (empty password).

  • If (server_capabilities & CLIENT_CONNECT_WITH_DB):

  • If (server_capabilities & CLIENT_PLUGIN_AUTH):

    • string authentication plugin name.

  • If (server_capabilities & CLIENT_CONNECT_ATTRS):

    • int size of connection attributes.

    • While packet has remaining data:

Server Response to Handshake Response Packet

The server responds with an OK_packet, an ERR_packet, or an Authentication Switch Request packet.

Authentication Switch Request

(If client and server support CLIENT_AUTH capability):

  • int<1> 0xFE : Authentication switch request header.

  • string authentication plugin name.

  • byte authentication plugin data.

Plugin List

mysql_old_password Plugin

deprecated — send a 8 byte encrypted password.

Authentication plugin data format :

Client response:

  • string old format encrypted password.

mysql_clear_password Plugin

Send clear password to server.

Client response:

  • string password without encryption.

mysql_native_password Plugin

SHA-1 encrypted password with server seed.

Authentication plugin data format:

Client response:

  • byte SHA1-encrypted password.

The password is encrypted with: SHA1( password ) ^ SHA1( seed + SHA1( SHA1( password ) ) ) .

dialog Plugin (PAM)

Interactive exchanges to permit fill passwords — for example for 2-step authentication.

Authentication plugin data format:

The server can send one or many requests. For each of them, the client must display this prompt message to the user, to permit the user to type requested information, then send it to the server in string format. Password type indicates the answer format (2 means "read the input with the echo enabled", 4 means "password-like input, echo disabled")

First authentication format (from authentication switch packet) can be empty.

This end when the server sends an EOF_Packet, OK_Packet or ERROR_packet.

auth_gssapi_client Plugin

GSSAPI implementation.

Authentication plugin data format :

  • string serverPrincipalName (UTF-8 format).

  • string mechanisms (UTF-8 format).

Client must exchange packet with server until having a mutual GSSAPI authentication. The only difference compared to standard client-server GSSAPI authentication is that exchanges contain standard protocol with packet headers.

client_ed25519 Plugin

The ed25519 plugin uses the Elliptic Curve Digital Signature Algorithm to securely store users' passwords and to authenticate users.

See plugin description.

The server sends a random nonce that the client signs.

authentication plugin data format :

Client response :

  • byte ed25519 encrypted password.

parsec Plugin

Authentication plugin data format:

Client has to send an empty packet to request "ext-salt".

Format of ext-salt is:

  • string<1> 'P' (denotes KDF algorithm = PBKDF2).

  • byte<1> iteration factor. number of iterations correspond to 1024 << iteration factor (0x0 means 1024, 0x1 means 2048, etc.).

  • byte salt.

The client must then:

  • Generate derived key = hash password with PBKDF2 ( sha512 digest) with iteration number and salt from ext-salt.

  • Generate a client 32 bytes nonce.

  • Generate the signature with ed25519 of an array concatenation of server nonce + client nonce with the generated derived key as private key.

Client response:

Capabilities

Server and Client have different capabilities, here is the possibles values. client with capabilities CLIENT_MYSQL + CONNECT_WITH_DB will have a value of 9 (1 + 8).

Capability
Value
Details

CLIENT_MYSQL

1

Set by older MariaDB versions. MySQL named this CLIENT_LONG_PASSWORD.

FOUND_ROWS

2

CONNECT_WITH_DB

8

You can specify database on connect.

COMPRESS

32

Can use compression protocol

LOCAL_FILES

128

IGNORE_SPACE

256

Ignore spaces before (.

CLIENT_PROTOCOL_41

1 << 9

4.1 protocol.

CLIENT_INTERACTIVE

1 << 10

SSL

1 << 11

Can use SSL.

TRANSACTIONS

1 << 13

SECURE_CONNECTION

1 << 15

4.1 authentication.

MULTI_STATEMENTS

1 << 16

Enable/disable multi-statement support.

MULTI_RESULTS

1 << 17

Enable/disable multi-results.

PS_MULTI_RESULTS

1 << 18

Enable/disable multi-results for PrepareStatement.

PLUGIN_AUTH

1 << 19

Client supports plugin authentication.

CONNECT_ATTRS

1 << 20

Client send connection attributes.

PLUGIN_AUTH_LENENC_CLIENT_DATA

1 << 21

Enable authentication response packet to be larger than 255 bytes.

CLIENT_CAN_HANDLE_EXPIRED_PASSWORDS

1 << 22

Client can handle expired passwords.

CLIENT_SESSION_TRACK

1 << 23

Enable/disable session tracking in OK_Packet.

CLIENT_DEPRECATE_EOF

1 << 24

EOF_Packet deprecation: OK_Packet replace EOF_Packet at the end of the result set when in text format. EOF_Packet between columns definition and resultsetRows is deleted.

CLIENT_OPTIONAL_RESULTSET_METADATA

1 << 25

Not in use for MariaDB.

CLIENT_ZSTD_COMPRESSION_ALGORITHM

1 << 26

Support zstd protocol compression.

CLIENT_CAPABILITY_EXTENSION

1 << 29

Reserved for future use.

CLIENT_SSL_VERIFY_SERVER_CERT

1 << 30

Client verify server certificate. Deprecated, client has options to indicate if server certifiate must be verified.

CLIENT_REMEMBER_OPTIONS

1 << 31

MARIADB_CLIENT_PROGRESS

1 << 32

Client support progress indicator.

MARIADB_CLIENT_COM_MULTI

1 << 33

Permit COM_MULTI protocol.

MARIADB_CLIENT_STMT_BULK_OPERATIONS

1 << 34

Permit bulk insert.

MARIADB_CLIENT_EXTENDED_METADATA

1 << 35

Add extended metadata information.

MARIADB_CLIENT_CACHE_METADATA

1 << 36

Permit skipping metadata.

MARIADB_CLIENT_BULK_UNIT_RESULTS

1 << 37

When enabled, indicate that bulk command can use STMT_BULK_FLAG_SEND_UNIT_RESULTS flag that permits to return a result set of all affected rows and auto-increment values.

Native Password Authentication

The 20 byte string 'seed' is calculated by concatenating scramble first part (8 bytes) and scramble second part from Initial handshake packet. After that, the client calculates a password hash using the password and seed by using ^ (bitwise xor), + (string concatenation) and SHA1 as follows:

SHA1( passwd) ^ SHA1( seed + SHA1( SHA1( passwd ) ) )

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