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Re: [libvirt] Stored secrets seem to get corrupted



On Wed, Jul 04, 2012 at 10:24:38AM +0200, Wido den Hollander wrote:
> 
> 
> On 03-07-12 17:21, Daniel P. Berrange wrote:
> >On Tue, Jul 03, 2012 at 05:11:48PM +0200, Wido den Hollander wrote:
> >>Yes, there is memory corruption somewhere. I never used valgrind
> >>before, but the output seems to show.
> >>
> >>I ran libvirtd inside a screen, I've attached the screenlog with all
> >>the output.
> >>
> >>At the end you'll see there is a misread. I was storing the base64
> >>encoded value of "wido".
> >
> >Thanks so there are two errors shown by valgrind
> >
> >==6825== Invalid read of size 1
> >==6825==    at 0x5769DBA: vfprintf (vfprintf.c:1624)
> >==6825==    by 0x58289D0: __vasprintf_chk (vasprintf_chk.c:68)
> >==6825==    by 0x509C727: virVasprintf (stdio2.h:199)
> >==6825==    by 0x508CFEA: virLogVMessage (logging.c:749)
> >==6825==    by 0x508D349: virLogMessage (logging.c:696)
> >==6825==    by 0x127AB0BC: secretSaveValue (secret_driver.c:297)
> >==6825==    by 0x127AB30A: secretSetValue (secret_driver.c:861)
> >==6825==    by 0x5130CF4: virSecretSetValue (libvirt.c:14457)
> >==6825==    by 0x41CC8F: remoteDispatchSecretSetValueHelper (remote_dispatch.h:10962)
> >==6825==    by 0x5174F84: virNetServerProgramDispatch (virnetserverprogram.c:416)
> >==6825==    by 0x5171260: virNetServerHandleJob (virnetserver.c:161)
> >==6825==    by 0x50990AD: virThreadPoolWorker (threadpool.c:143)
> >==6825==  Address 0x19cb3c64 is 0 bytes after a block of size 4 alloc'd
> >==6825==    at 0x4C29DB4: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
> >==6825==    by 0x508E32F: virAllocN (memory.c:128)
> >==6825==    by 0x127AB21B: secretSetValue (secret_driver.c:838)
> >==6825==    by 0x5130CF4: virSecretSetValue (libvirt.c:14457)
> >==6825==    by 0x41CC8F: remoteDispatchSecretSetValueHelper (remote_dispatch.h:10962)
> >==6825==    by 0x5174F84: virNetServerProgramDispatch (virnetserverprogram.c:416)
> >==6825==    by 0x5171260: virNetServerHandleJob (virnetserver.c:161)
> >==6825==    by 0x50990AD: virThreadPoolWorker (threadpool.c:143)
> >==6825==    by 0x5098755: virThreadHelper (threads-pthread.c:161)
> >==6825==    by 0x550AE99: start_thread (pthread_create.c:308)
> >==6825==    by 0x58124BC: clone (clone.S:112)
> >
> >This one is harmless - this is because the VIR_DEBUG line you added
> >uses '%s' to print secret_value, but this is not a NULL terminated
> >string. So we can ignore this.
> >
> >
> >==6825==
> >==6825== Invalid read of size 4
> >==6825==    at 0xA57E4B9: base64_encode (in /usr/lib/x86_64-linux-gnu/libroken.so.18.1.0)
> >==6825==    by 0x10DDBC98: base64_encode_alloc (base64.c:140)
> >==6825==    by 0x127AB0EF: secretSaveValue (secret_driver.c:302)
> >==6825==    by 0x127AB30A: secretSetValue (secret_driver.c:861)
> >==6825==    by 0x5130CF4: virSecretSetValue (libvirt.c:14457)
> >==6825==    by 0x41CC8F: remoteDispatchSecretSetValueHelper (remote_dispatch.h:10962)
> >==6825==    by 0x5174F84: virNetServerProgramDispatch (virnetserverprogram.c:416)
> >==6825==    by 0x5171260: virNetServerHandleJob (virnetserver.c:161)
> >==6825==    by 0x50990AD: virThreadPoolWorker (threadpool.c:143)
> >==6825==    by 0x5098755: virThreadHelper (threads-pthread.c:161)
> >==6825==    by 0x550AE99: start_thread (pthread_create.c:308)
> >==6825==    by 0x58124BC: clone (clone.S:112)
> >==6825==  Address 0xb7786c8 is 8 bytes inside a block of size 9 alloc'd
> >==6825==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
> >==6825==    by 0xA57E3D7: base64_encode (in /usr/lib/x86_64-linux-gnu/libroken.so.18.1.0)
> >==6825==    by 0x10DDBC98: base64_encode_alloc (base64.c:140)
> >==6825==    by 0x127AB0EF: secretSaveValue (secret_driver.c:302)
> >==6825==    by 0x127AB30A: secretSetValue (secret_driver.c:861)
> >==6825==    by 0x5130CF4: virSecretSetValue (libvirt.c:14457)
> >==6825==    by 0x41CC8F: remoteDispatchSecretSetValueHelper (remote_dispatch.h:10962)
> >==6825==    by 0x5174F84: virNetServerProgramDispatch (virnetserverprogram.c:416)
> >==6825==    by 0x5171260: virNetServerHandleJob (virnetserver.c:161)
> >==6825==    by 0x50990AD: virThreadPoolWorker (threadpool.c:143)
> >
> >This one is very interesting. It shows that the 'base64_encode' function
> >is doing an out-of-bounds read. More tellingly though is that it is
> >reporting 'base64_encode' function is in a wierd library:
> >
> >    /usr/lib/x86_64-linux-gnu/libroken.so.18.1.
> >
> >If this were normal, we should expect to see that function present
> >in 'base64.c' since this function code is provided by gnulib itself.
> >
> >So something else libvirt is linking to, directly or indirectly
> >is using  libroken.so which also has a 'base64_encode'symbol
> >defined. This is overriding gnulib's symbol of the same name.
> >
> >I'm willing to bet the API contract of this libroken.so base64_encode.
> >differs from GNULIBS, with crashtastic results
> >
> >Can you try and find how this libroken.so is getting linked to libvirt ?
> >
> >Or indeed what this library does, or what package it is part of.
> 
> The library is libroken18-heimdal under Ubuntu 12.04:
> http://packages.ubuntu.com/precise/libroken18-heimdal
> 
> When installing ubuntu-virt-server libraries like gnutls depend on
> this library.
> 
> I'm not sure why libvirt gets linked to libroken, but on Ubuntu
> systems it's installed on most system which use libvirt.
> 
> I haven't found a header file which as the symbol 'base64_encode' in
> it for libroken, only gnutls and glib seem to have something that
> has 'base64_encode' in it, but those are prefixed with g_

I expect that this is an internal symbol from libroken.so which
they leak into the public namespace.

> For now I have no clues to why it gets linked to libroken, but it
> seems the problem has been found.

If gnutls links to libroken.so, then libvirt gets linked to it
indirectly

It sounds like we might need to have a workaround in gnulib to
avoid this problem. With other cases where gnulib replaces existing
symbols they use some magic such that the gnulib replacement gets
prefixed with 'rpl_'.

Daniel
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