General issues with UserAtHost proxy

[chsoft-ag]

FTP OS: irrelevant

FTP Server: irrelevant

FTP Proxy: CCProxy 8.0 (and likely others)

Computer OS: Windows 10 20H2

FluentFTP Version: 34.0

There appear to be two general issues with the UserAtHost proxy.

CCProxy and probably other proxies provide a status 220 banner on connect. With the current UserAtHost proxy implementation it is impossible to connect in such a case, because the Execute("USER " + userName); during Authenticate will run into the StaleDataCheck, which closes the stream, causing another failing Connect() attempt and the whole thing continues failing recursively.

Inserting a GetReply() during the proxy handshake solves the issue (as in the custom Blue Coat solution for #246), but I think calling base.Handshake() should be the preferred way for FTP proxies to override that method anyway, no? I am not sure though whether all FTP proxies provide a banner, or if a direct or indirect call to GetReply() during the handshake might actually lead to a potential hang if they do not.

The second issue is that the current method of replacing Credentials.UserName with User@Host information is not guarded, which leads to User@Host@Host@Host... if Handshake is called repeatedly as in the scenario above.

I'm happy to provide a PR for these issues, if there is some consensus on how to approach the first issue. If proxies exist with or without banner, perhaps a check of whether the stream has data before calling GetReply() is an option, or a version of that function that times out instead of blocking when no data is available?

Logs :

# Connect()
# Connect()
Status:   Connecting to 192.168.40.9:2121
Status:   Connecting to 192.168.40.9:2121
Status:   There is stale data on the socket, maybe our connection timed out or you did not call GetReply(). Re-connecting...
Status:   There is stale data on the socket, maybe our connection timed out or you did not call GetReply(). Re-connecting...
Status:   The stale data was: 220-CCProxy FTP Service(Unregistered)
220-you need to input userid@site as login name.
220 Example: user [email protected]
Status:   The stale data was: 220-CCProxy FTP Service(Unregistered)
220-you need to input userid@site as login name.
220 Example: user [email protected]
Status:   Disposing FtpSocketStream...
Status:   Disposing FtpSocketStream...

# Connect()
# Connect()
Status:   Connecting to 192.168.40.9:2121
Status:   Connecting to 192.168.40.9:2121
Status:   There is stale data on the socket, maybe our connection timed out or you did not call GetReply(). Re-connecting...
Status:   There is stale data on the socket, maybe our connection timed out or you did not call GetReply(). Re-connecting...
Status:   The stale data was: 220-CCProxy FTP Service(Unregistered)
220-you need to input userid@site as login name.
220 Example: user [email protected]
Status:   The stale data was: 220-CCProxy FTP Service(Unregistered)
220-you need to input userid@site as login name.
220 Example: user [email protected]
Status:   Disposing FtpSocketStream...
Status:   Disposing FtpSocketStream...

[continues ad infinitum]

[robinrodricks]

Hi, thanks for this detailed issue/PR. The first option is probably better check of whether the stream has data before calling GetReply().

[robinrodricks]

If this is specific to CCProxy, then it would be better to create a custom proxy class like for BlueHost, if you are not sure, then also create a custom proxy class.

[FamiPun]

I encountered a similar problem when using UserAtHost proxy, but it was solved by creating a custom proxy class like BlueHost.

[robinrodricks]

Added to the bucket list. We will pick this up as and when we have free time. Comment on this issue if you want us to prioritize it. Thanks!