From cdbc3fa8edc5b42391a5f2bfe1a8f6099929acf7 Mon Sep 17 00:00:00 2001

From: Alan Coopersmith <alan.coopersmith@oracle.com>

Date: Fri, 6 Jan 2023 12:50:48 -0800

Subject: [PATCH libXpm 5/6] Fix CVE-2022-4883: compression commands depend on

 $PATH

By default, on all platforms except MinGW, libXpm will detect if a

filename ends in .Z or .gz, and will when reading such a file fork off

an uncompress or gunzip command to read from via a pipe, and when

writing such a file will fork off a compress or gzip command to write

to via a pipe.

In libXpm 3.5.14 or older these are run via execlp(), relying on $PATH

to find the commands.  If libXpm is called from a program running with

raised privileges, such as via setuid, then a malicious user could set

$PATH to include programs of their choosing to be run with those

privileges.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

---

 README.md    | 12 ++++++++++++

 configure.ac | 14 ++++++++++++++

 src/RdFToI.c | 17 ++++++++++++++---

 src/WrFFrI.c |  4 ++--

 4 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md

index f3f4c93..0b1c886 100644

--- a/README.md

+++ b/README.md

@@ -31,3 +31,15 @@ if it can't find the file it was asked to open.  It relies on the

 --enable-open-zfile feature to open the file, and is enabled by default

 when --enable-open-zfile is enabled, and can be disabled by passing the

 --disable-stat-zfile flag to the configure script.

+

+All of these commands will be executed with whatever userid & privileges the

+function is called with, relying on the caller to ensure the correct euid,

+egid, etc. are set before calling.

+

+To reduce risk, the paths to these commands are now set at configure time to

+the first version found in the PATH used to run configure, and do not depend

+on the PATH environment variable set at runtime.

+

+To specify paths to be used for these commands instead of searching $PATH, pass

+the XPM_PATH_COMPRESS, XPM_PATH_UNCOMPRESS, XPM_PATH_GZIP, and XPM_PATH_GUNZIP

+variables to the configure command.

diff --git a/configure.ac b/configure.ac

index 85e2c73..4fc370d 100644

--- a/configure.ac

+++ b/configure.ac

@@ -49,6 +49,14 @@ if test "x$USE_GETTEXT" = "xyes" ; then

 fi

 AM_CONDITIONAL(USE_GETTEXT, test "x$USE_GETTEXT" = "xyes")

+dnl Helper macro to find absolute path to program and add a #define for it

+AC_DEFUN([XPM_PATH_PROG],[

+AC_PATH_PROG([$1], [$2], [])

+AS_IF([test "x$$1" = "x"],

+      [AC_MSG_ERROR([$2 not found, set $1 or use --disable-stat-zfile])])

+AC_DEFINE_UNQUOTED([$1], ["$$1"], [Path to $2])

+]) dnl End of AC_DEFUN([XPM_PATH_PROG]...

+

 # Optional feature: When a filename ending in .Z or .gz is requested,

 # open a pipe to a newly forked compress/uncompress/gzip/gunzip command to

 # handle it.

@@ -64,6 +72,12 @@ AC_ARG_ENABLE(open-zfile,

 AC_MSG_RESULT([$OPEN_ZFILE])

 if test x$OPEN_ZFILE = xno ; then

         AC_DEFINE(NO_ZPIPE, 1, [Define to 1 to disable decompression via pipes])

+else

+        XPM_PATH_PROG([XPM_PATH_COMPRESS], [compress])

+        XPM_PATH_PROG([XPM_PATH_UNCOMPRESS], [uncompress])

+        XPM_PATH_PROG([XPM_PATH_GZIP], [gzip])

+        XPM_PATH_PROG([XPM_PATH_GUNZIP], [gunzip])

+        AC_CHECK_FUNCS([closefrom close_range], [break])

 fi

 # Optional feature: When ___.xpm is requested, also look for ___.xpm.Z & .gz

diff --git a/src/RdFToI.c b/src/RdFToI.c

index bd09611..a91d337 100644

--- a/src/RdFToI.c

+++ b/src/RdFToI.c

@@ -43,6 +43,7 @@

 #include <errno.h>

 #include <sys/types.h>

 #include <sys/wait.h>

+#include <unistd.h>

 #else

 #ifdef FOR_MSW

 #include <fcntl.h>

@@ -161,7 +162,17 @@ xpmPipeThrough(

 	    goto err;

 	if ( 0 == pid )

 	{

-	    execlp(cmd, cmd, arg1, (char *)NULL);

+#ifdef HAVE_CLOSEFROM

+	    closefrom(3);

+#elif defined(HAVE_CLOSE_RANGE)

+# ifdef CLOSE_RANGE_UNSHARE

+#  define close_range_flags CLOSE_RANGE_UNSHARE

+# else

+#  define close_range_flags 0

+#endif

+	    close_range(3, ~0U, close_range_flags);

+#endif

+	    execl(cmd, cmd, arg1, (char *)NULL);

 	    perror(cmd);

 	    goto err;

 	}

@@ -235,12 +246,12 @@ OpenReadFile(

 	if ( ext && !strcmp(ext, ".Z") )

 	{

 	    mdata->type = XPMPIPE;

-	    mdata->stream.file = xpmPipeThrough(fd, "uncompress", "-c", "r");

+	    mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_UNCOMPRESS, "-c", "r");

 	}

 	else if ( ext && !strcmp(ext, ".gz") )

 	{

 	    mdata->type = XPMPIPE;

-	    mdata->stream.file = xpmPipeThrough(fd, "gunzip", "-qc", "r");

+	    mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_GUNZIP, "-qc", "r");

 	}

 	else

 #endif /* z-files */

diff --git a/src/WrFFrI.c b/src/WrFFrI.c

index 328c987..d59098f 100644

--- a/src/WrFFrI.c

+++ b/src/WrFFrI.c

@@ -342,10 +342,10 @@ OpenWriteFile(

 #ifndef NO_ZPIPE

 	len = strlen(filename);

 	if (len > 2 && !strcmp(".Z", filename + (len - 2))) {

-	    mdata->stream.file = xpmPipeThrough(fd, "compress", NULL, "w");

+	    mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_COMPRESS, NULL, "w");

 	    mdata->type = XPMPIPE;

 	} else if (len > 3 && !strcmp(".gz", filename + (len - 3))) {

-	    mdata->stream.file = xpmPipeThrough(fd, "gzip", "-q", "w");

+	    mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_GZIP, "-q", "w");

 	    mdata->type = XPMPIPE;

 	} else

 #endif

-- 

2.39.0