authentication issue with md5 on postgres 11

[rickcoup]

• asyncpg version: 0.21.0 and lower
• PostgreSQL version: 11
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?:
• Python version: 3.6.0
• Platform: linux 3.10.0
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and
  uvloop?:

We have the same code. When running with useridAAA with password, it works on some servers, but not on other servers. The useridAAA's password is authenticated with md5 on the postgres. If we switch to useridBBB, which is authenticated as SHA256 on postgres. It works on all servers. It's the same password for useridAAA and useridBBB. What's dictating the hash on the password on the client side?

Below is the error message when couldn't be authenticated.
`DEBUG: Using selector: EpollSelector

DEBUG: Get address info edclpgsd320c.bcbsfl.com:5420, type=<SocketKind.SOCK_STREAM: 1>

DEBUG: Getting address info edclpgsd320c.bcbsfl.com:5420, type=<SocketKind.SOCK_STREAM: 1> took 2.792 ms: [(<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_STREAM: 1>, 6, '', ('))]

DEBUG: poll 59997.326 ms took 1.820 ms: 1 events

DEBUG: connect <socket.socket fd=6, family=AddressFamily.AF_INET, type=2049, proto=6, laddr=('0.0.0.0', 0)> to ()

DEBUG: poll 59993.166 ms took 0.141 ms: 1 events

DEBUG: <socket.socket fd=6, family=AddressFamily.AF_INET, type=2049, proto=6, laddr=('), raddr=(')> connected to : (<_SelectorSocketTransport fd=6 read=polling write=<idle, bufsize=0>>, <asyncpg.protocol.protocol.Protocol object at 0x7fc691bc7858>)

DEBUG: poll 59990.760 ms took 0.014 ms: 1 events

INFO: poll 59990.568 ms took 60000.243 ms: 1 events

DEBUG: <_SelectorSocketTransport fd=6 read=polling write=<idle, bufsize=0>> received EOF

Traceback (most recent call last):

File "asyncdb3c.py", line 52, in

app = loop.run_until_complete(init_app())

File "/usr/lib64/python3.6/asyncio/base_events.py", line 484, in run_until_complete

return future.result()

File "asyncdb3c.py", line 34, in init_app

pool = await asyncpg.create_pool("postgres://useridAAA:------@------.-----.com:5490/xxx01s1?application_name=aaa",min_size=1, max_size=3,max_inactive_connection_lifetime=3)

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/pool.py", line 398, in async__init_

await self._initialize()

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/pool.py", line 426, in _initialize

await first_ch.connect()

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/pool.py", line 125, in connect

self._con = await self._pool._get_new_connection()

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/pool.py", line 472, in _get_new_connection

**self._connect_kwargs)

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/connection.py", line 1727, in connect

max_cacheable_statement_size=max_cacheable_statement_size)

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/connect_utils.py", line 666, in _connect

connection_class=connection_class)

File "/usr/lib64/python3.6/asyncio/coroutines.py", line 110, in next

return self.gen.send(None)

File "/u/i3ye/ppx/lib64/python3.6/site-packages/asyncpg/connect_utils.py", line 642, in _connect_addr

await asyncio.wait_for(connected, timeout=timeout)

File "/usr/lib64/python3.6/asyncio/tasks.py", line 358, in wait_for

return fut.result()

asyncpg.exceptions.ConnectionDoesNotExistError: connection was closed in the middle of operation

`

[elprans]

The error traceback you provided doesn't seem to be related to authentication. Looks like a network issue to me. What do server-side logs show?

[rickcoup]

Here is the server log. It doesn't seem related either. Regardless, which code in the client is deciding to do MD5 or SHA256?

020-09-22 09:32:42.141 EDT [26229]: [26229-10] db=----,user=useridAAA,app=[unknown],client=---.comLOG: disconnection: session time: 0:00:03.012 user=useridAAA database=--- host=----.com port=61034
2020-09-22 09:32:42.154 EDT [25375]: [25375-2] db=----,user=useridAAA,app=[unknown],client=---.comFATAL: canceling authentication due to timeout

[elprans]

Authentication method is decided by the server based on configuration, asyncpg only reacts to what the server is asking it to do. See _parse_msg_authentication.

[rickcoup]

Trying to find out how the postgres server to instruct the client to hash, but didn't find much. What's the constant that the client is using from the server to do the hash? I doubt on that because we have the same server and the same client code.But the different hash was used by the same client code. It seems the client code is influenced by something else.

Also, looking at code below from https://gemfury.com/agriconnect/python:asyncpg/0.18.2/content/protocol/coreproto.pyx. It doesn't seem it's handling the scram sha 256?

`cdef _parse_msg_authentication(self):
        cdef:
            int32_t status
            bytes md5_salt

    status = self.buffer.read_int32()

    if status == AUTH_SUCCESSFUL:
        # AuthenticationOk
        self.result_type = RESULT_OK

    elif status == AUTH_REQUIRED_PASSWORD:
        # AuthenticationCleartextPassword
        self.result_type = RESULT_OK
        self.auth_msg = self._auth_password_message_cleartext()

    elif status == AUTH_REQUIRED_PASSWORDMD5:
        # AuthenticationMD5Password
        # Note: MD5 salt is passed as a four-byte sequence
        md5_salt = self.buffer.read_bytes(4)
        self.auth_msg = self._auth_password_message_md5(md5_salt)

    elif status in (AUTH_REQUIRED_KERBEROS, AUTH_REQUIRED_SCMCRED,
                    AUTH_REQUIRED_GSS, AUTH_REQUIRED_GSS_CONTINUE,
                    AUTH_REQUIRED_SSPI):
        self.result_type = RESULT_FAILED
        self.result = apg_exc.InterfaceError(
            'unsupported authentication method requested by the '
            'server: {!r}'.format(AUTH_METHOD_NAME[status]))

    else:
        self.result_type = RESULT_FAILED
        self.result = apg_exc.InterfaceError(
            'unsupported authentication method requested by the '
            'server: {}'.format(status))

    self.buffer.discard_message()`

[elprans]

It doesn't seem it's handling the scram sha 256?

You are looking at a fairly old version of asyncpg. Why 0.18.2?

[rickcoup]

look at the latest code. where is the PROTOCOL_AUTH value from?

cdef _connect(self):
     cdef:
         WriteBuffer buf
         WriteBuffer outbuf

     if self.con_status != CONNECTION_BAD:
         raise apg_exc.InternalClientError('already connected')

     self._set_state(PROTOCOL_AUTH)
     self.con_status = CONNECTION_STARTED

[haoyun]

google led me to this old open issue. I have a related problem with asyncpg. I understood from #769 that kerberos authentication is not supported. However the error information is quite strange.

what I got is

Traceback (most recent call last):
  File "asyncpg/protocol/coreproto.pyx", line 154, in asyncpg.protocol.protocol.CoreProtocol._process__auth
  File "asyncpg/protocol/coreproto.pyx", line 621, in asyncpg.protocol.protocol.CoreProtocol._parse_msg_authentication
NameError: name 'AUTH_METHOD_NAME' is not defined

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
...
  File "/home/yun/.conda/envs/saffron/lib/python3.9/asyncio/tasks.py", line 479, in wait_for
    return fut.result()
asyncpg.exceptions._base.InternalClientError: unexpected error while performing authentication: name 'AUTH_METHOD_NAME' is not defined

which indicates that AUTH_METHOD_NAME is not defined. That's quite strange.