[LBBS-62] net_imap: IMAP client frequently fails for Microsoft accounts
Lately, I've been noticing that Microsoft client proxies frequently fail. Seems to be due to a bug with how we're parsing the capabilities responses:
[2024-08-03 09:24:50.630] DEBUG[551614]: io_tls.c:804 ssl_client_new: TLS SN: /C=US/ST=Washington/L=Redmond/O=Microsoft Corporation/CN=outlook.com
[2024-08-03 09:24:50.630] DEBUG[551614]: io_tls.c:811 ssl_client_new: TLS Issuer: /C=US/O=DigiCert Inc/CN=DigiCert Cloud Services CA-1
[2024-08-03 09:24:50.630] DEBUG[551614]: io_tls.c:819 ssl_client_new: TLS verification successful 0x7fbe5000ae20
[2024-08-03 09:24:50.630] DEBUG[551614]: io.c:170 io_transform_store: Set up node I/O transformer at index 0
[2024-08-03 09:24:50.630] DEBUG[551614]: tcp.c:58 bbs_tcp_client_connect: Implicit TLS completed
...
[2024-08-03 09:24:50.657] DEBUG[551614]: tcp.c:107 bbs_tcp_client_expect: <= * CAPABILITY IMAP4 IMAP4rev1 AUTH=PLAIN AUTH=XOAUTH2 SASL-IR UIDPLUS ID UNSELECT CHILDREN IDLE NAMESPACE LITERAL+
[2024-08-03 09:24:50.657] DEBUG[551614]: mod_mail.c:1717 imap_client_capability: Capabilities: IMAP4 IMAP4rev1 AUTH=PLAIN AUTH=XOAUTH2 SASL-IR UIDPLUS ID UNSELECT CHILDREN IDLE NAMESPACE LITERAL+
[2024-08-03 09:24:50.657] DEBUG[551614]: tcp.c:107 bbs_tcp_client_expect: <= a0 OK CAPABILITY completed.
...
[2024-08-03 09:24:53.114] DEBUG[551614]: readline.c:151 bbs_readline: bbs_poll_read returned -1
[2024-08-03 09:24:53.114] DEBUG[551614]: mod_mail.c:1903 imap_client_login: Didn't receive expected 'a1 OK'
[2024-08-03 09:24:53.114] DEBUG[551614]: imap_client.c:45 client_destroy: Destroying IMAP client...Comments
9/13/2024 9:06 PM — InterLinked
Autoresolved by code commit on GitHub:
mod_mail: Log remote IMAP server error when LOGIN fails.
https://github.com/InterLinked1/lbbs/commit/9a1918b2c5d7dd2bfb0a94c3843222e0acb7d6cd
You must be
9/13/2024 8:58 PM — InterLinked
No bug in capability parsing existed, though a related bug in logging the LOGIN error has been identified.
The actual cause of this is that Microsoft is deliberately rejecting login attempts intermittently, in anticipation of their disabling basic authentication on Monday: https://support.microsoft.com/en-us/office/modern-authentication-methods-now-needed-to-continue-syncing-outlook-email-in-non-microsoft-email-apps-c5d65390-9676-4763-b41f-d7986499a90d
"Until September 16th, users signing into Outlook.com through Basic Authentication may experience recurring password prompts in Outlook and other third-party email applications. This is a known issue. After September 16th, users attempting to connect their Microsoft accounts through Basic Authentication will fail to do so."
While a workaround would be to retry multiple times if LOGIN fails, I will not be implementing that because the server is 100% at fault here, and it would only work for the next 3 days anyways. Trust Microsoft to not know how to run a mail server, as usual.