[Samba] NTLMSSP Sign/Seal - using NTLM1

[Vincent]

Hello,

We have a customer that is using Samba version 4.7.12 and Windows 10
clients. When they initiate connections, they are very slow to authenticate
(several minutes). It does not readily appear there are network
connectivity issues.

Of possible note, the following log sequence is, repeatedly, observed
within the Samba debug logs:

[2023/07/06 11:14:15.676774,  3, pid=2118992, effective(0, 0), real(0, 0)]
../auth/ntlmssp/ntlmssp_sign.c:509(ntlmssp_sign_reset)
  NTLMSSP Sign/Seal - Initialising with flags:
[2023/07/06 11:14:15.676783,  3, pid=2118992, effective(0, 0), real(0, 0)]
../auth/ntlmssp/ntlmssp_util.c:69(debug_ntlmssp_flags)
  Got NTLMSSP neg_flags=0x62008a15
    NTLMSSP_NEGOTIATE_UNICODE
    NTLMSSP_REQUEST_TARGET
    NTLMSSP_NEGOTIATE_SIGN
    NTLMSSP_NEGOTIATE_NTLM
    NTLMSSP_ANONYMOUS
    NTLMSSP_NEGOTIATE_ALWAYS_SIGN
    NTLMSSP_NEGOTIATE_VERSION
    NTLMSSP_NEGOTIATE_128
    NTLMSSP_NEGOTIATE_KEY_EXCH
[2023/07/06 11:14:15.676809,  5, pid=2118992, effective(0, 0), real(0, 0)]
../auth/ntlmssp/ntlmssp_sign.c:633(ntlmssp_sign_reset)
  *NTLMSSP Sign/Seal - using NTLM1*
[2023/07/06 11:14:15.786392,  3, pid=2118992, effective(0, 0), real(0, 0)]
../source3/libsmb/cliconnect.c:1678(cli_session_setup_creds_done_spnego)
  SPNEGO login failed: The request is not supported.

What would cause the client to use NTLM1 for signing and sealing? Is this
due to the NTLMSSP_NEGOTIATE_SEAL flag not being set? Is this even an
issue? I presume it may be problematic, due to the subsequent "SPNEGO login
failed" message.

Thank you,

Vincent