rdesktop 1.8.6 crashes when connecting to xrdp 0.9.9, but not when connecting to xrdp 0.5.0

[Matthias Adam]

Hello,

this is my first post on this list, so I'll just give as much information as possible.

My client in this scenario is a running Manjaro Linux (Arch Linux, rolling release at kernel 5.1.21.1 currently) and I'm trying to connect to my two raspberry pi (2B and 4B).

Result when connecting to Raspberry Pi 2B, running raspbian Wheezy (7) and xrdp 0.5.0: No problems using "rdesktop -u pi -p XXXX 192.168.1.101

Result when connecting to Raspberry Pi 4B, running raspbian Buster (10) and xrdp 0.9.9 using same syntax, other IP: 

$ rdesktop -u pi -p XXXXXX 192.168.1.123
Autoselected keyboard map de
Connection established using plain RDP.
ERROR: rdp.c:1123: process_demand_active(), consume of source descriptor from stream would overrun0000 03 00 01 b5 02 f0 80 68 00 01 03 eb 70 81 a6 08 .......h....p...
0010 00 00 00 69 bd b4 0a 77 e5 a7 2a 2a d9 c1 dc 67 ...i...w..**...g
0020 54 36 3e 08 9a cd f4 75 00 88 b3 8d 80 e6 cb a3 T6>....u........
0030 04 bd 4c c0 a7 05 45 45 6b f5 6e 55 39 93 ca 31 ..L...EEk.nU9..1
0040 71 02 dc a4 bf ec 01 b5 f4 10 60 90 77 ec d1 9d q.........`.w...
0050 5f 84 9c 42 01 5f 8d 66 4a e6 ab 76 cd 89 7a 1e _..B._.fJ..v..z.
0060 8f c4 e2 7d be a8 28 e2 44 a4 34 79 b5 39 1f 91 ...}..(.D.4y.9..
0070 ba 25 d9 f4 48 af f4 4c 4f 44 6d 0a 34 6d 8c 4a .%..H..LODm.4m.J
0080 c1 65 4a ed f2 e2 ea e1 e2 8f 68 4d d5 f0 59 4a .eJ.......hM..YJ
0090 a6 ad d5 f5 93 a3 bc b5 f7 0c 85 31 6f c2 e2 3e ...........1o..>
00a0 d0 6d 26 eb db 31 24 ef 3c 29 f1 e8 57 5a 9e 50 .m&..1$.<)..WZ.P
00b0 df 54 99 dd e2 35 c6 5a e3 c3 ab 9d 62 9b 6e 18 .T...5.Z....b.n.
00c0 6c 4a 5c d9 fa 53 79 01 be e4 ca d8 25 5a 00 79 lJ\..Sy.....%Z.y
00d0 bd f6 72 cd cf 8c db 7e bb c6 e0 d2 11 74 95 09 ..r....~.....t..
00e0 4b 39 68 ba e9 e4 c7 a8 16 c8 01 f5 11 00 2b 46 K9h...........+F
00f0 10 9e 80 02 09 0c d5 c5 a9 f2 36 67 d4 96 be 96 ..........6g....
0100 e7 b2 16 72 0e 22 93 16 de a1 1e 74 0c f3 ec f7 ...r.".....t....
0110 b0 7c 12 f6 1e 29 9d e8 bd d5 3f e3 21 2d 3a 08 .|...)....?.!-:.
0120 93 3c 41 bc 2a b5 d5 7a 72 3c 1d f7 86 2e a3 2b .<A.*..zr<.....+
0130 a7 ef a7 eb 6c d0 ec d8 ca b9 fc f6 f8 da fe 7d ....l..........}
0140 c7 fa 8b f9 9b 8f 3c f3 e9 3a d4 0c b0 b5 08 02 ......<..:......
0150 b8 91 ed c1 6b ac 01 0e cd e2 9a ad 86 2f 52 33 ....k......../R3
0160 7c 30 0a 6d 38 ad 0f ee a4 ae 89 43 db bb 52 44 |0.m8......C..RD
0170 ee ec 87 64 5b 96 36 67 00 b8 39 4f 5a 7f 64 07 ...d[.6g..9OZ.d.
0180 99 35 46 4c 2a 7e 30 f9 30 e1 d5 12 5e 1a 27 f2 .5FL*~0.0...^.'.
0190 c9 9a 45 7a 6d 19 cc 99 4d 37 d5 ef 2e b3 fd 91 ..Ezm...M7......
01a0 b3 79 c1 e1 e2 21 23 a1 e4 6f e0 bf ab 05 90 a3 .y...!#..o......
01b0 33 8b 1a d3 72                                  3...r

I can ssh into both hosts without problem. What gave the last impuls to report this bug here is the fact, that I can connect to the Raspberry Pi 4b (xrdp 0.9.9) just fine when using "$ xfreerdp /u:pi /p:XXXXX /v:192.168.1.123" from my Arch Linux box. So the problem has to exist with the combination rdesktop 1.8.6 & xrdp 0.9.9.

With an older laptop sporting Ubuntu 18.04.3 and rdesktop 1.8.3, it also works flawlessly.

I hope the given details can provide you a hint to the underlying problem. I guess the issue will occur pretty frequently in the future as raspbian buster (and xrdp 0.9.9 with it) is being used more and more in the next future by the raspberry pi community.

In case I can help with any further details and/or testing, just let me know.

[Pierre Ossman]

On 17/08/2019 03:14, Matthias Adam wrote:
> Hello,
>
> this is my first post on this list, so I'll just give as much information
> as possible.
>
> My client in this scenario is a running Manjaro Linux (Arch Linux, rolling
> release at kernel 5.1.21.1 currently) and I'm trying to connect to my two
> raspberry pi (2B and 4B).
> Result when connecting to Raspberry Pi 2B, running raspbian Wheezy (7) and
> xrdp 0.5.0: No problems using "rdesktop -u pi -p XXXX 192.168.1.101
> Result when connecting to Raspberry Pi 4B, running raspbian Buster (10) and
> xrdp 0.9.9 using same syntax, other IP:
>
> $ rdesktop -u pi -p XXXXXX 192.168.1.123
> Autoselected keyboard map de
> Connection established using plain RDP.
> ERROR: rdp.c:1123: process_demand_active(), consume of source descriptor

We've had several reports of this happening with older versions of
Windows. Unfortunately we don't know why at this point. Someone that can
reproduce the issue would need to look at Microsoft's protocol
documentation and compare with the code and see what might be incorrect.

It only seems to happen with the legacy RDP mode though. So if you
configure TLS then you should be fine.

Regards
--
Pierre Ossman Software Development
Cendio AB https://cendio.com
Teknikringen 8 https://twitter.com/ThinLinc
583 30 Linköping https://facebook.com/ThinLinc
Phone: +46-13-214600

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

[Matthias Adam]

We've had several reports of this happening with older versions of
Windows. Unfortunately we don't know why at this point. Someone that can
reproduce the issue would need to look at Microsoft's protocol
documentation and compare with the code and see what might be incorrect.

It only seems to happen with the legacy RDP mode though. So if you
configure TLS then you should be fine.

Hello,

sorry but I do not really understand what you are proposing.

There is no Windows involved, as I am trying to connect to Debian Linux Hosts from my Arch Linux box.

Concerning the TLS mode: The only way to influence the encryption while starting rdesktop is by passing the options -e or -E to rdesktop, switching encryption off. Does that not mean that it should be automatically enabled, unless I use those switches?

I have generated cert.pem and key.pem with the openssl command given in the xrdp.ini and entered the right path to them in the xrdp.ini, so the hosts TLS capability should be set up nicely.

Is there any other detail I might have overlooked?

[Pierre Ossman]

On 08/09/2019 20:44, Matthias Adam wrote:
>
>>
>> We've had several reports of this happening with older versions of
>> Windows. Unfortunately we don't know why at this point. Someone that can
>> reproduce the issue would need to look at Microsoft's protocol
>> documentation and compare with the code and see what might be incorrect.
>>
>> It only seems to happen with the legacy RDP mode though. So if you
>> configure TLS then you should be fine.
>>
>>
>> Hello,
>
> sorry but I do not really understand what you are proposing.
> There is no Windows involved, as I am trying to connect to Debian Linux
> Hosts from my Arch Linux box.
>

Sorry. My point was that we've _also_ seen this with Windows, even if
only older things.

> Concerning the TLS mode: The only way to influence the encryption while
> starting rdesktop is by passing the options -e or -E to rdesktop, switching
> encryption off. Does that not mean that it should be automatically enabled,
> unless I use those switches?
> I have generated cert.pem and key.pem with the openssl command given in the
> xrdp.ini and entered the right path to them in the xrdp.ini, so the hosts
> TLS capability should be set up nicely.
>
> Is there any other detail I might have overlooked?
>

I'm afraid I'm not familiar with how FreeRDP works. rdesktop will always
use TLS if the server supports it. So the issue should be somewhere in
the FreeRDP configuration. I'm afraid I don't know how to debug it
further than that.