Problem with libssh2_session_handshake

[dapepe]

After the recent update I am receiving the following error message when syncing files via SFTP:

Cannot read file attributes of "sftp://username@192.168.1.5:22".
LIBSSH2_ERROR_NONE [libssh2_session_handshake]


Any suggestions why this is happening?

[dapepe]

P.S.: Using Version 11.27 (Donation Edition) on MacOS Ventura 13.0

[Zenju]

There's only one place inside libssh2_session_handshake() with buggy error handling, so I'm guessing you're hitting it.
Does the following fixed version give a better error message? https://www.mediafire.com/file/0mcagr2utbu6x4g/FreeFileSync_11.28_beta_macOS%25282%2529.zip

[dapepe]

Thanks for your quick response. I tried your version, unfortunately same results!

[Zenju]

Let's dig a little deeper: https://www.mediafire.com/file/odqwkh67hvkpz6j/FreeFileSync_11.28_beta2_macOS%25282%2529.zip

[dapepe]

Again, no luck:

Cannot find the following folders:

sftp://xxxxxxxxx@192.168.157.5:20202/home/media
___________________________________________

Cannot read file attributes of "sftp://xxxxxxxxx@192.168.157.5:20202".
LIBSSH2_ERROR_OUT_OF_BOUNDARY


I tested the SFTP connection with CyberDuck, it's working.

[Zenju]

Which SFTP server are you using? Ideally, I'd have steps to reproduce this.

Until then, the following version should give a more detailed error message: https://www.mediafire.com/file/2e55usw5sy90958/FreeFileSync_11.28_beta3_macOS.zip

[dapepe]

I am accessing my local Synology NAS.

This is the error messages:

Cannot read file attributes of "sftp://xxxxxxxxxx@192.168.157.5:20202".
LIBSSH2_ERROR_OUT_OF_BOUNDARY: Failed to get response to ssh-userauth request [libssh2_session_handshake]


[Zenju]

Okay, one more level deeper: https://www.mediafire.com/file/b5iloxnp3krbi4p/FreeFileSync_11.28_beta4_macOS.zip

[dapepe]

Thanks! Here's the new error message:

Cannot read file attributes of "sftp://xxxxxxx@192.168.157.5:20202".
LIBSSH2_ERROR_OUT_OF_BOUNDARY: transport.c line 478: -117770238 [libssh2_session_handshake]


Hope this helps!

[Zenju]

libssh2 is sending SSH_MSG_SERVICE_REQUEST for "ssh-userauth", then waiting for the server to respond with SSH_MSG_SERVICE_ACCEPT:
https://github.com/libssh2/libssh2/blob/821d50dad313b53fb2782f26aec1f52f1be34fc0/src/session.c#L781

However, while unpacking the response stream it finds p->packet_length is 4177197058 > LIBSSH2_PACKET_MAXPAYLOAD(40000) and fails with LIBSSH2_ERROR_OUT_OF_BOUNDARY.
https://github.com/libssh2/libssh2/blob/821d50dad313b53fb2782f26aec1f52f1be34fc0/src/transport.c#L444

The 4177197058 value looks like corrupted data. If it is a SFTP server bug, or an issue of libssh2 doing something wrong in the steps prior I don't know.

If you know some way to reproduce the issue on my machine I could try to find the issue. Otherwise it's a job for these guys: https://github.com/libssh2/libssh2/issues

[dapepe]

OK, thanks for investigating! I guess I will stay with version 11.17 for now, this is the last version where everything worked fine!