Bug#912206: freerdp2-x11: ERRCONNECT_TLS_CONNECT_FAILED with libssl1.1 1.1.1-1

[Mike Gabriel]

Hi,

On  Mo 29 Okt 2018 09:34:54 CET, Kevin Locke wrote:

Package: freerdp2-x11
Version: 2.0.0~git20180411.1.7a7b1802+dfsg1-2+b1
Severity: normal

Dear Maintainer,

After upgrading libssl1.1 from 1.1.0h-4 to 1.1.1-1 xfreerdp is no longer
able to connect to a computer running Remote Desktop Services on Windows
Server 2008 R2 (with default settings as far as I am aware) using TLS
security.  Connection fails with the following messages:



Downgrading libssl1.1 to 1.1.0h-4 fixes the issue.  To further diagnose
the cause, I noticed that the server sends TCP RST in response to the
SSL Client Hello message.  After some trial and error, I determined that
this occurs whenever rsa_pkcs1_sha1 in not the offered signature
algorithms, which is the case for SECLEVEL=2 which is the default in the
libssl1.1 Debian package since version 1.1.1~~pre6-1.  To confirm, this
fails:

    openssl s_client -connect 192.168.0.2:3389

while this works:

    openssl s_client -cipher DEFAULT@SECLEVEL=1 -connect 192.168.0.2:3389

For further confirmation that rsa_pkcs1_sha1 is responsible, this works:



while this fails:



Applying this discovery, it is possible to make xfreerdp work using:

    xfreerdp /tls-ciphers:DEFAULT@SECLEVEL=1

However, since most users are unlikely to figure this out on their own,
I'd suggest calling SSL_CTX_set_security_level to set the security level
to 1 or improving the error message to suggest this workaround.

Thanks,
Kevin

[ERROR][com.freerdp.core] - freerdp_set_last_error ERRCONNECT_TLS_CONNECT_FAILED [0x00020008] [ERROR][com.freerdp.core.connection] - Error: protocol security negotiation or connection failure openssl s_client -cipher DEFAULT@SECLEVEL=1 -sigalgs rsa_pkcs1_sha1 -connect 192.168.0.2:3389 openssl s_client -cipher DEFAULT@SECLEVEL=1 -sigalgs RSA+SHA512:DSA+SHA512:ECDSA+SHA512:RSA+SHA384:DSA+SHA384:ECDSA+SHA384:RSA+SHA256:DSA+SHA256:ECDSA+SHA256:RSA+SHA224:DSA+SHA224:ECDSA+SHA224:DSA+SHA1:ECDSA+SHA1 -connect 192.168.0.2:3389

Mike
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Bernhard from FreeRDP upstream has started working on this and we will likely provide patches next week. So, please stay tuned + thanks for reporting this. The problem is caused by system-wide openssl default settings that have changed between those two referenced openssl versions. We will try to pin things down in FreeRDP, so that system-wide defaults don't apply anymore for FreeRDP.

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