Generating Unpredictable Data for MariaDB: RANDOM_BYTES Explained

• If the argument is outside this range or NULL, an error occurs.
• The function takes one argument: an integer between 1 and 1024 representing the desired number of random bytes.
• These bytes are cryptographically secure, meaning they are unpredictable and suitable for security applications like creating encryption keys, password salts, or session tokens.
• Introduced in MariaDB version 10.10, RANDOM_BYTES is a function that generates a sequence of random bytes of a specified length.

Example of using RANDOM_BYTES:

SELECT RANDOM_BYTES(32);  -- Generates 32 random bytes

Alternatives for older MariaDB versions (or if you can't upgrade):

• UDF (User-Defined Function): You can create a custom function written in C that leverages a cryptographically secure random number generator library (e.g., OpenSSL) to produce random bytes within MariaDB. This approach requires more development effort but offers full control.

Important considerations:

• Statement-based replication: If you're using statement-based replication in MariaDB, be aware that statements containing RANDOM_BYTES might not be replicated consistently across all nodes in the cluster.
• Security: Never use RAND() for generating random bytes in security contexts. It's not cryptographically secure and can compromise your application's security.

In summary:

• Always prioritize cryptographically secure methods for sensitive tasks like encryption and password hashing.
• For older versions, explore UDFs or consider upgrading if possible.
• For MariaDB 10.10 and later, use RANDOM_BYTES for secure random byte generation.

-- Generate 16 random bytes (suitable for many encryption keys)
SELECT RANDOM_BYTES(16) AS random_key;

-- Generate a 32-character hexadecimal string (useful for displaying random values)
SELECT HEX(RANDOM_BYTES(16)) AS hex_random;

Alternative for older MariaDB versions (using SUBSTR and MD5):

-- This approach is NOT cryptographically secure, use with caution!
-- It's for demonstration purposes only in older MariaDB versions.

-- Generate 16 pseudo-random bytes (less secure than RANDOM_BYTES)
SELECT SUBSTR(MD5(RAND()), 1, 32) AS pseudo_random_bytes;

-- Generate a 32-character hexadecimal string (similar to RANDOM_BYTES example)
SELECT HEX(SUBSTR(MD5(RAND()), 1, 16)) AS hex_pseudo_random;

-- Warning: This method (using MD5) is not recommended for security-sensitive applications.

Key points:

• Consider upgrading to MariaDB 10.10 or later if possible to benefit from RANDOM_BYTES.
• The alternative using MD5 is for demonstration purposes only and should not be used for generating random bytes in security contexts (encryption, password hashing).
• The RANDOM_BYTES function is the preferred and most secure method for MariaDB 10.10 and later.

• This approach offers full control but requires more development effort.
• The function would leverage a cryptographically secure random number generator library like OpenSSL to generate the bytes within MariaDB.
• This method involves creating a custom function written in C.

Here's a general outline (not actual code):

CREATE FUNCTION generate_random_bytes(length INT)
RETURNS VARBINARY(length)
SONAME 'path/to/your/udf.so';

• You'll need to write the C code for the function itself to interact with the random number generator library and return the bytes.
• Replace path/to/your/udf.so with the actual path to your compiled UDF library.

Application-Level Generation:

• This approach separates the randomness generation from the database layer, potentially offering more flexibility in your application design.
• Then, pass those bytes as parameters to your MariaDB queries.
• Instead of relying on MariaDB to generate random bytes, you can generate them in your application code (e.g., PHP, Python, Java) using the language's built-in secure random number generation functions.

Here are some examples of secure random byte generation functions in common languages:

• Java: SecureRandom.nextBytes()
• Python: os.urandom()
• PHP: openssl_random_pseudo_bytes()

External Tools (for one-time use):

• However, you'll need to manually insert this data into your MariaDB tables, which might not be ideal for frequent use.
• Tools like openssl rand or /dev/urandom (on Linux) can be used to create random data.
• For one-time use cases, you can generate random bytes using external tools on your system.

Choosing the Right Method:

• External tools are a last resort for one-time use cases.
• Application-level generation can be a good option if you need more flexibility in your application design.
• For older versions, consider UDFs if you have the development resources.
• If you're using MariaDB 10.10 or later, RANDOM_BYTES is the recommended and most secure method.