Re: [Xen-staging] [xen-unstable] hvm: Remove access to QEMU monitor inVNC server

[Anthony Liguori <aliguori@us.ibm.com>]

Christian Limpach wrote:
>> hvm: Remove access to QEMU monitor in VNC server
>>
>> This fixes a RHEL5 errata and CVE-2007-0998.
>>
>> The monitor is still accessible in debug builds of ioemu (debug=y).
>>
>> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> 
> This change is quite weird since it doesn't disable monitor access when
> using SDL.
> 
> Also, the additional virtual consoles can be used for giving access to
> things without security implications, like serial ports.
> 
> I think a much better fix for the security issue would be to change the
> default monitor output not to be a virtual console.

QEMU 0.9.0 supports redirecting the monitor to a unix socket and 
supports reconnecting to the monitor (so that the banner is shown each 
time).

When using these options, you can actually execute monitor commands from 
the command line by doing something like:

echo help | socat stdin unix:/path/to/socket

With these patches (or by moving qemu-dm up to 0.9.0), someone could add 
an xm monitor command that let you execute commands via xm.

That, IMHO, would be the best possible solution.

Regards,

Anthony Liguori

>     christian
> 
>> ---
>>  tools/ioemu/Makefile.target |    4 ++++
>>  tools/ioemu/vnc.c           |   13 +++++++++++--
>>  2 files changed, 15 insertions(+), 2 deletions(-)
>>
>> diff -r a9a39cc52e74 -r 3375391fb0c9 tools/ioemu/Makefile.target
>> --- a/tools/ioemu/Makefile.target	Tue Mar 27 16:19:25 2007 +0100
>> +++ b/tools/ioemu/Makefile.target	Tue Mar 27 16:23:52 2007 +0100
>> @@ -193,6 +193,10 @@ LIBS+=-lsocket -lnsl -lresolv
>>  LIBS+=-lsocket -lnsl -lresolv
>>  endif
>>  
>> +ifeq ($(debug),y)
>> +CFLAGS += -DQEMU_VNC_MONITOR_EXPORT
>> +endif
>> +
>>  # profiling code
>>  ifdef TARGET_GPROF
>>  LDFLAGS+=-p
>> diff -r a9a39cc52e74 -r 3375391fb0c9 tools/ioemu/vnc.c
>> --- a/tools/ioemu/vnc.c	Tue Mar 27 16:19:25 2007 +0100
>> +++ b/tools/ioemu/vnc.c	Tue Mar 27 16:23:52 2007 +0100
>> @@ -113,8 +113,10 @@ struct VncState
>>      int visible_w;
>>      int visible_h;
>>  
>> +#ifdef QEMU_VNC_MONITOR_EXPORT
>>      int ctl_keys;               /* Ctrl+Alt starts calibration */
>>      int shift_keys;             /* Shift / CapsLock keys */
>> +#endif
>>      int numlock;
>>  };
>>  
>> @@ -895,6 +897,7 @@ static void do_key_event(VncState *vs, i
>>  	    kbd_put_keycode(keycode & 0x7f);
>>  	else
>>  	    kbd_put_keycode(keycode | 0x80);
>> +#ifdef QEMU_VNC_MONITOR_EXPORT
>>      } else if (down) {
>>  	int qemu_keysym = 0;
>>  
>> @@ -922,8 +925,10 @@ static void do_key_event(VncState *vs, i
>>  	}
>>  	if (qemu_keysym != 0)
>>  	    kbd_put_keysym(qemu_keysym);
>> -    }
>> -
>> +#endif
>> +    }
>> +
>> +#ifdef QEMU_VNC_MONITOR_EXPORT
>>      if (down) {
>>  	switch (sym) {
>>  	case XK_Control_L:
>> @@ -976,6 +981,10 @@ static void do_key_event(VncState *vs, i
>>  	    break;
>>  	}
>>      }
>> +#else
>> +    if (!down && sym == XK_Num_Lock)
>> +        vs->numlock = !vs->numlock;
>> +#endif
>>  }
>>  
>>  static void key_event(VncState *vs, int down, uint32_t sym)
>>
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>>