530 Login authentication failed: ftpcontrolsocket.cpp anonymous login fallback decision

Question

FileZilla reports 530 Login authentication failed. when an FTP/S server rejects credentials, with the response processed in ftpcontrolsocket.cpp by CFtpControlSocket::OnLoginResponse(). When a Site Manager entry is configured to ask for a password and the user cancels the prompt, the connection ends without an anonymous login attempt.

Because this fallback behavior is not exposed in the GUI and is undocumented, there is no clear indication whether the client is intentionally designed to abort or whether an anonymous retry is expected under certain configurations. The uncertainty complicates testing integrations against sandboxed servers without production credentials.

Is the absence of an automatic anonymous retry after a cancelled password prompt the intended behavior for all protocol versions? Does the source contain a conditional path that permits anonymous fallback when the server permits it, or is the connection always terminated? Where is this decision documented for users who need predictable credential handling in automated test environments?

Tasadduq Burney · Answer

Direct answer
For FileZilla 3.x, cancelling the password prompt when a Site Manager entry is set to "Ask for password" aborts the connection. The client does not automatically retry with anonymous credentials, and the described logic in ftpcontrolsocket.cpp contains no conditional path that starts an anonymous fallback solely because the user cancelled the prompt. This behavior is consistent across FTP, FTPS, and FTPES because the decision is made by the client before protocol-specific authentication is retried.
Confirmed facts and assumptions
Confirmed, with the FileZilla 3.x version assumption

CFtpControlSocket::OnLoginResponse() evaluates server responses such as 530 after credentials are submitted.
Cancelling the password dialog closes the connection before an anonymous USER command is sent.
Anonymous login occurs only when the Site Manager entry is explicitly configured for anonymous access or the user explicitly selects it.

Assumptions and uncertainty

Internal class structure may change in major FileZilla versions, so this does not cover future 4.x or later builds.
FTP protocol specifications do not define client-side anonymous fallback, so "all protocol versions" cannot be confirmed from protocol behavior alone.
No user-facing documentation location was independently verified; the GUI does not expose this fallback setting.

Verification steps

Open Site Manager and set the test entry to "Ask for password."
Connect and cancel the password prompt.
Confirm FileZilla disconnects without sending USER anonymous.
Check the server log for a connection followed by disconnect, with no anonymous login attempt.

Example server-side diagnostic, scoped to read-only log inspection: tail -n 50 /var/log/vsftpd.log. Substitute your server's actual log path and do not run against production systems without change control.
Missing diagnostic detail
Which FileZilla major version and operating system are you testing against? The version determines whether the 3.x behavior description applies to your build.

530 Login authentication failed: ftpcontrolsocket.cpp anonymous login fallback decision

1 answer

Direct answer

Confirmed facts and assumptions

Confirmed, with the FileZilla 3.x version assumption

Assumptions and uncertainty

Verification steps

Missing diagnostic detail

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