Session start and authentication

Every iproto session begins with a greeting and optional authentication.

When a client connects to the server instance, the instance responds with a 128-byte text greeting message, not in MsgPack format:

 
Tarantool <version> (<protocol>) <instance-uuid><salt>

For example:

 
Tarantool 2.10.0 (Binary) 29b74bed-fdc5-454c-a828-1d4bf42c639aQK2HoFZGXTXBq2vFj7soCsHqTo6PGTF575ssUBAJLAI=

The greeting contains two 64-byte lines of ASCII text. Each line ends with a newline character (\n). If the line content is less than 64 bytes long, the rest of the line is filled up with symbols with an ASCII code of 0 that aren't displayed in the console.

The first line contains the instance version and protocol type. The second line contains the session salt – a base64-encoded random string, which is usually 44 bytes long. The salt is used in the authentication packet – the IPROTO_AUTH message.

If authentication is skipped, then the session user is 'guest' (the 'guest' user does not need a password).

If authentication is not skipped, then at any time an authentication packet can be prepared using the greeting, the user's name and password, and sha-1 functions, as follows.

 
PREPARE SCRAMBLE:    size_of_encoded_salt_in_greeting = 44;    size_of_salt_after_base64_decode = 32;     /* sha1() will only use the first 20 bytes */    size_of_any_sha1_digest = 20;    size_of_scramble = 20;prepare 'chap-sha1' scramble:    salt = base64_decode(encoded_salt);    step_1 = sha1(password);    step_2 = sha1(step_1);    step_3 = sha1(first_20_bytes_of_salt, step_2);    scramble = xor(step_1, step_3);    return scramble;