Marco Ivaldi <marco.ivaldi@mediaservice.net> has identified 3
vulnerabilities in CDE.
Two of them could affect our CDE (open-source version), while the 3rd
(sdtcm_convert) is Solaris specific.
The two vulnerabilities, both of which affect dtsession could allow a
local privilege escalation to root. A POC exists for Solaris. The
POC will not function on our CDE for two main reasons:
- the POC is Solaris specific
- The overflowed variables in question are allocated on the heap,
whereas in Solaris these variables are located on the stack.
The first vulnerability allows an extra long palette name to be used
to cause a crash via insufficient validation in
SrvPalette.c:CheckMonitor().
The second, which has not yet been assigned a CERT CVE resides in
SmCreateDirs.c:_DtCreateDtDirs() in libDtSvc. Due to insufficient
bounds checking, a crash or corruption can be achieved by using a very
long DISPLAY name.
This one is considered difficult to exploit, and no POC code is
available at this time. CDE 2.x code-bases are also listed as not
vulnerable, however some work has been done anyway to do some proper
bounds checking in this function.
The following text portions are copied from the relevant advisories,
which have not been released as of this writing.
NOTE: Oracle CDE does NOT use CDE 2.3.0a or earlier as mentioned
below. They are completely different code-bases):
Regarding CVE-2020-2692:
A buffer overflow in the CheckMonitor() function in the Common
Desktop Environment 2.3.0a and earlier, as distributed with Oracle
Solaris 10 1/13 (Update 11) and earlier, allows local users to gain
root privileges via a long palette name passed to dtsession in a
malicious .Xdefaults file.
Note that Oracle Solaris CDE is based on the original CDE 1.x train,
which is different from the CDE 2.x codebase that was later open
sourced. Most notably, the vulnerable buffer in the Oracle Solaris
CDE is stack-based, while in the open source version it is
heap-based.
Regarding the DtSvc bug, which does not currently have a CERT CVE:
A difficult to exploit stack-based buffer overflow in the
_DtCreateDtDirs() function in the Common Desktop Environment version
distributed with Oracle Solaris 10 1/13 (Update 11) and earlier may
allow local users to corrupt memory and potentially execute
arbitrary code in order to escalate privileges via a long X11
display name. The vulnerable function is located in the libDtSvc
library and can be reached by executing the setuid program
dtsession.
The open source version of CDE (based on the CDE 2.x codebase) is
not affected.
There was code (_DtSimpleError() and _DtSimpleErrornoError()) that
only used snprintf when USE_SNPRINTF was defined, which it never was
of course. We just remove the 2 checks and always use [v]snprintf.
With this patch, CDE (autotools) builds and runs on fbsd 12 now.
fbsd11 should work too, but not yet tested.
You must use gmake - ie:
./configure MAKE=gmake
gmake
Seems all of the BSD's will need to use gmake for now.
Certain programs like dtlogin and tt_type_comp need access to the
system's cpp command to process certain files at runtime. tradcpp is
not installed on most systems, and is intended for use as a imake-cpp
replacement which is all we are using it for. We still need an
honest cpp for the CDE components to use.
Now, we look in various places for a 'cpp' command and set CPP_COMMAND
to it's value. This way tt_type_comp and other CDE programs can do
required processing at runtime.
There is a problem with CPP_PROGRAM - using $CPP or $GENCPP (tradcpp)
always fails in tt_type_comp with the error:
"nclude ", line 8: syntax error
If I define it to /lib/cpp (previous hardcoded value) then it seems to
work fine. Only the dtinfo and dtinfo_start ptypes use #include, and
therefore show this error. Needs investigation.
Also, restructure some of the dependencies in the lib/tt binaries. We
will link with libtt (which will include libtirpc as a dependency),
and XTOOLLIB - all the right X11 stuff without needing to add it to
every OS. Removed several uneeded OS specializations ("if LINUX",
etc) as a result.
This means that when linking against libtt, libtirpc should also
automatically be linked in if we determined that we are using tirpc.
This avoids having to link every program that uses libtt (almost all
of them) from having to have a $(TIRPCLIB) added to their link
commands.
We take advantage of subdir-object and just build the subdir source
files directly as normal dependencies of libDtSvc in the top level
Makefile.am.
This means the intevening subdirectory Makefiles are no longer needed,
and no need to replicate flags and the like between the
subdirectory Makefile.am files.
Also, no need to build fake .a libs we can't really use.
configure: remove AC_OUTPUT_FILES related the the lib/DtSvc/*
subdirectories. They are no longer needed.
We were building subsets of this library as archive.a objects, then
trying to combine them into a shared object. This warnings, and link
failures due to the lack of 0fPIC when building the archive libraries.
Now, we do not buld archive libraries, and the main libDtSvc.so
library is build by adding all of the .lo file in the component
subdirectories.
In a future commit, we could just remove the SUBDIR builds (DtUtil1,
etc) and build the sub objects directly.
Jon Trulson