X2Go Bug report logs - #1429
Tilde expansion no longer performed by libssh after CVE-2019-14889

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Message #5 received at submit@bugs.x2go.org (full text, mbox, reply):

From: Sylvain Cuaz <sylvain@ilm-informatique.fr>

To: submit@bugs.x2go.org

Subject: Tilde expansion no longer performed by libssh after CVE-2019-14889

Date: Fri, 20 Dec 2019 18:21:24 +0100

Package: x2goclient
Version: 4.1.1.1

SSH key fails to be copied to the remote side because the path use a tilde, so neither file sharing nor client-side printing works.

Client OS Ubuntu 18.04.3 LTS with libssh-4 0.8.0~20170825.94fa1e38-1ubuntu0.5
Server OS Ubuntu 16.04.6 LTS

Since december, 10th on Ubuntu, every time I connect to a server with either file sharing or printing enabled I have this error message :
"Cannot create remote file ~ilm/.x2go/ssh/key.jdT502" - "SCP: Warning: status code 1 received: scp: ~ilm/.x2go/ssh: No such file or directory\n"
But the directory does exist.

After using gdb I saw that ONMainWindow::exportDirs() calls SshMasterConnection::copyFile() with dst="~"+uname +"/.x2go/ssh/"+dst;
which is ultimately passed to libssh. But following CVE-2019-14889 the path is now literal (quoted), see
https://git.libssh.org/projects/libssh.git/log/src/scp.c for the libssh logs and
https://usn.ubuntu.com/4219-1/ for the ubuntu packages

A similar issue is handled for Windows in SshProcess::start_cp()

As a workaround I reinstalled an old version of the libssh-4 package and the bug went away.

Message #10 received at 1429@bugs.x2go.org (full text, mbox, reply):

From: Mihai Moldovan <ionic@ionic.de>

To: Sylvain Cuaz <sylvain@ilm-informatique.fr>, 1429@bugs.x2go.org

Subject: Re: [X2Go-Dev] Bug#1429: Tilde expansion no longer performed by libssh after CVE-2019-14889

Date: Fri, 20 Dec 2019 19:06:14 +0100

[Message part 1 (text/plain, inline)]

Control: reassign -1 x2goclient 4.1.2.1
Control: forcemerge -1 1428

* On 12/20/19 6:21 PM, Sylvain Cuaz wrote:
> SSH key fails to be copied to the remote side because the path use a tilde, so neither file sharing nor client-side printing works.
> [...]
> After using gdb I saw that ONMainWindow::exportDirs() calls SshMasterConnection::copyFile() with dst="~"+uname +"/.x2go/ssh/"+dst;
> which is ultimately passed to libssh. But following CVE-2019-14889 the path is now literal (quoted), see
> https://git.libssh.org/projects/libssh.git/log/src/scp.c for the libssh logs and
> https://usn.ubuntu.com/4219-1/ for the ubuntu packages

Yes, I think that this change has been intentional. I'll have to fix that in
X2Go Client and I know how to do this easily to retain support for pre-patched
and patched versions.

I will, however, probably not be able to provide new release versions with that
fix (and others) for about a months.

I'll let you know when fixed nightly versions are available, though.


> As a workaround I reinstalled an old version of the libssh-4 package and the bug went away.

Please don't do that OR recommend that. You're essentially now running without
the CVE fix, which is probably worse than a broken client.



Mihai

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Message #23 received at 1429@bugs.x2go.org (full text, mbox, reply):

From: Sylvain Cuaz <sylvain@ilm-informatique.fr>

To: Mihai Moldovan <ionic@ionic.de>, 1429@bugs.x2go.org

Subject: Re: [X2Go-Dev] Bug#1429: Tilde expansion no longer performed by libssh after CVE-2019-14889

Date: Fri, 20 Dec 2019 21:44:07 +0100

Le 20/12/2019 à 19:06, Mihai Moldovan a écrit :
> Control: reassign -1 x2goclient 4.1.2.1
> Control: forcemerge -1 1428
>
> * On 12/20/19 6:21 PM, Sylvain Cuaz wrote:
>> SSH key fails to be copied to the remote side because the path use a tilde, so neither file sharing nor client-side printing works.
>> [...]
>> After using gdb I saw that ONMainWindow::exportDirs() calls SshMasterConnection::copyFile() with dst="~"+uname +"/.x2go/ssh/"+dst;
>> which is ultimately passed to libssh. But following CVE-2019-14889 the path is now literal (quoted), see
>> https://git.libssh.org/projects/libssh.git/log/src/scp.c for the libssh logs and
>> https://usn.ubuntu.com/4219-1/ for the ubuntu packages
> Yes, I think that this change has been intentional. I'll have to fix that in
> X2Go Client and I know how to do this easily to retain support for pre-patched
> and patched versions.
>
> I will, however, probably not be able to provide new release versions with that
> fix (and others) for about a months.
>
> I'll let you know when fixed nightly versions are available, though.

OK thanks

>> As a workaround I reinstalled an old version of the libssh-4 package and the bug went away.
> Please don't do that OR recommend that. You're essentially now running without
> the CVE fix, which is probably worse than a broken client.

Yes, 'workaround' was not the right word. I meant while investigating to confirm my findings.

Message #28 received at 1429@bugs.x2go.org (full text, mbox, reply):

From: Mihai Moldovan <ionic@ionic.de>

To: Sylvain Cuaz <sylvain@ilm-informatique.fr>, 1429@bugs.x2go.org

Subject: Re: [X2Go-Dev] Bug#1429: Tilde expansion no longer performed by libssh after CVE-2019-14889

Date: Sat, 21 Dec 2019 00:30:51 +0100

[Message part 1 (text/plain, inline)]

* On 12/20/19 9:44 PM, Sylvain Cuaz wrote:
> Le 20/12/2019 à 19:06, Mihai Moldovan a écrit :
>> I'll let you know when fixed nightly versions are available, though.
> 
> OK thanks

Nightly builds should incorporate the fix now.



Mihai

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