Couchbase Developer's Guide 1.8 - Chapter 7. Developing a Client Library

7.1.1. List Mechanisms
Prev	7.1. Providing SASL Authentication	Next

7.1.1. List Mechanisms

We start the SASL authentication by asking the memcached server for the mechanisms it supports. This is achieved by sending the following packet:

Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 80 | 20 | 00 | 00 |
+---------------+---------------+---------------+---------------+
4| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
8| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
12| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
16| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
20| 00 | 00 | 00 | 00 |

Header breakdown
Field (offset) (value)
Magic (0): 0x80 (PROTOCOL_BINARY_REQ)
Opcode (1): 0x20 (sasl list mechs)
Key length (2-3): 0x0000 (0)
Extra length (4): 0x00
Data type (5): 0x00
vBucket (6-7): 0x0000 (0)
Total body (8-11): 0x00000000 (0)
Opaque (12-15): 0x00000000 (0)
CAS (16-23): 0x0000000000000000 (0)

If the server supports SASL authentication the following packet is returned:

Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 81 | 20 | 00 | 00 |
+---------------+---------------+---------------+---------------+
4| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
8| 00 | 00 | 00 | 05 |
+---------------+---------------+---------------+---------------+
12| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
16| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
20| 00 | 00 | 00 | 00 |
+---------------+---------------+---------------+---------------+
24| 50 ('P') | 4c ('L') | 41 ('A') | 49 ('I') |
+---------------+---------------+---------------+---------------+

28| 4e ('N') |

Header breakdown
Field (offset) (value)
Magic (0): 0x81 (PROTOCOL_BINARY_RES)
Opcode (1): 0x20 (sasl list mechs)
Key length (2-3): 0x0000 (0)
Extra length (4): 0x00
Data type (5): 0x00
Status (6-7): 0x0000 (SUCCESS)
Total body (8-11): 0x00000005 (5)
Opaque (12-15): 0x00000000 (0)
CAS (16-23): 0x0000000000000000 (0)
Mechanisms (24-28): PLAIN

Please note that the server may support a different set of mechanisms. The list of mechanisms is a space-separated list of SASL mechanism names (e.g. "PLAIN CRAM-MD5 GSSAPI").