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xserver: check for elevated privileges not uid=0

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This allows us to run the server as a normal user whilst still
being able to use the -modulepath, -logfile and -config switches
We define a xf86PrivsElevated which will do the checks and cache
the result in case it is called more than once.
Also renamed the paths #defines to match their new meaning.
Original discussion which led to this patch can be found here:
http://lists.freedesktop.org/archives/xorg-devel/2011-September/025853.html

Signed-off-by: Antoine Martin <antoine@nagafix.co.uk>
Tested-by: Michal Suchanek <hramrach at centrum.cz>
Reviewed-by: Jamey Sharp <jamey at minilop.net>
Reviewed-by: Adam Jackson <ajax@redhat.com>
This commit is contained in:
Antoine Martin 2011-12-17 01:36:51 +07:00 committed by Keith Packard
parent 2c1d0a539c
commit ead968a430
5 changed files with 91 additions and 24 deletions
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2
configure.ac
View File

@ -212,7 +212,7 @@ AC_CHECK_FUNC([dlopen], [],
AC_SUBST(DLOPEN_LIBS)
dnl Checks for library functions.
AC_CHECK_FUNCS([backtrace ffs \
AC_CHECK_FUNCS([backtrace ffs geteuid getuid issetugid getresuid \
getdtablesize getifaddrs getpeereid getpeerucred getzoneid \
mmap shmctl64 strncasecmp vasprintf vsnprintf walkcontext])
AC_REPLACE_FUNCS([strcasecmp strcasestr strlcat strlcpy strndup])

28
hw/xfree86/common/xf86Config.c
View File

@ -72,8 +72,8 @@
* These paths define the way the config file search is done. The escape
* sequences are documented in parser/scan.c.
*/
#ifndef ROOT_CONFIGPATH
#define ROOT_CONFIGPATH "%A," "%R," \
#ifndef ALL_CONFIGPATH
#define ALL_CONFIGPATH "%A," "%R," \
"/etc/X11/%R," "%P/etc/X11/%R," \
"%E," "%F," \
"/etc/X11/%F," "%P/etc/X11/%F," \
@ -83,8 +83,8 @@
"%P/lib/X11/%X.%H," \
"%P/lib/X11/%X"
#endif
#ifndef USER_CONFIGPATH
#define USER_CONFIGPATH "/etc/X11/%S," "%P/etc/X11/%S," \
#ifndef RESTRICTED_CONFIGPATH
#define RESTRICTED_CONFIGPATH "/etc/X11/%S," "%P/etc/X11/%S," \
"/etc/X11/%G," "%P/etc/X11/%G," \
"/etc/X11/%X," "/etc/%X," \
"%P/etc/X11/%X.%H," \
@ -92,14 +92,14 @@
"%P/lib/X11/%X.%H," \
"%P/lib/X11/%X"
#endif
#ifndef ROOT_CONFIGDIRPATH
#define ROOT_CONFIGDIRPATH "%A," "%R," \
#ifndef ALL_CONFIGDIRPATH
#define ALL_CONFIGDIRPATH "%A," "%R," \
"/etc/X11/%R," "%C/X11/%R," \
"/etc/X11/%X," "%C/X11/%X"
#endif
#ifndef USER_CONFIGDIRPATH
#define USER_CONFIGDIRPATH "/etc/X11/%R," "%C/X11/%R," \
"/etc/X11/%X," "%C/X11/%X"
#ifndef RESTRICTED_CONFIGDIRPATH
#define RESTRICTED_CONFIGDIRPATH "/etc/X11/%R," "%C/X11/%R," \
"/etc/X11/%X," "%C/X11/%X"
#endif
#ifndef SYS_CONFIGDIRPATH
#define SYS_CONFIGDIRPATH "/usr/share/X11/%X," "%D/X11/%X"
@ -2310,12 +2310,12 @@ xf86HandleConfigFile(Bool autoconfig)
MessageType filefrom = X_DEFAULT;
MessageType dirfrom = X_DEFAULT;
if (getuid() == 0) {
filesearch = ROOT_CONFIGPATH;
dirsearch = ROOT_CONFIGDIRPATH;
if (!xf86PrivsElevated()) {
filesearch = ALL_CONFIGPATH;
dirsearch = ALL_CONFIGDIRPATH;
} else {
filesearch = USER_CONFIGPATH;
dirsearch = USER_CONFIGDIRPATH;
filesearch = RESTRICTED_CONFIGPATH;
dirsearch = RESTRICTED_CONFIGDIRPATH;
}
if (xf86ConfigFile)

78
hw/xfree86/common/xf86Init.c
View File

@ -238,6 +238,65 @@ xf86PrintMarkers(void)
LogPrintMarkers();
}
Bool xf86PrivsElevated(void)
{
static Bool privsTested = FALSE;
static Bool privsElevated = TRUE;
if (!privsTested) {
#if defined(WIN32)
privsElevated = FALSE;
#else
if ((getuid() != geteuid()) || (getgid() != getegid())) {
privsElevated = TRUE;
} else {
#if defined(HAVE_ISSETUGID)
privsElevated = issetugid();
#elif defined(HAVE_GETRESUID)
uid_t ruid, euid, suid;
gid_t rgid, egid, sgid;
if ((getresuid(&ruid, &euid, &suid) == 0) &&
(getresgid(&rgid, &egid, &sgid) == 0)) {
privsElevated = (euid != suid) || (egid != sgid);
}
else {
printf("Failed getresuid or getresgid");
/* Something went wrong, make defensive assumption */
privsElevated = TRUE;
}
#else
if (getuid()==0) {
/* running as root: uid==euid==0 */
privsElevated = FALSE;
}
else {
/*
* If there are saved ID's the process might still be privileged
* even though the above test succeeded. If issetugid() and
* getresgid() aren't available, test this by trying to set
* euid to 0.
*/
unsigned int oldeuid;
oldeuid = geteuid();
if (seteuid(0) != 0) {
privsElevated = FALSE;
} else {
if (seteuid(oldeuid) != 0) {
FatalError("Failed to drop privileges. Exiting\n");
}
privsElevated = TRUE;
}
}
#endif
}
#endif
privsTested = TRUE;
}
return privsElevated;
}
static Bool
xf86CreateRootWindow(WindowPtr pWin)
{
@ -872,7 +931,7 @@ OsVendorInit(void)
#ifdef O_NONBLOCK
if (!beenHere) {
if (geteuid() == 0 && getuid() != geteuid())
if (xf86PrivsElevated())
{
int status;
@ -1043,10 +1102,11 @@ ddxProcessArgument(int argc, char **argv, int i)
FatalError("Required argument to %s not specified\n", argv[i]); \
}
/* First the options that are only allowed for root */
/* First the options that are not allowed with elevated privileges */
if (!strcmp(argv[i], "-modulepath") || !strcmp(argv[i], "-logfile")) {
if ( (geteuid() == 0) && (getuid() != 0) ) {
FatalError("The '%s' option can only be used by root.\n", argv[i]);
if (xf86PrivsElevated()) {
FatalError("The '%s' option cannot be used with "
"elevated privileges.\n", argv[i]);
}
else if (!strcmp(argv[i], "-modulepath"))
{
@ -1074,9 +1134,9 @@ ddxProcessArgument(int argc, char **argv, int i)
if (!strcmp(argv[i], "-config") || !strcmp(argv[i], "-xf86config"))
{
CHECK_FOR_REQUIRED_ARGUMENT();
if (getuid() != 0 && !xf86PathIsSafe(argv[i + 1])) {
if (xf86PrivsElevated() && !xf86PathIsSafe(argv[i + 1])) {
FatalError("\nInvalid argument for %s\n"
"\tFor non-root users, the file specified with %s must be\n"
"\tWith elevated privileges, the file specified with %s must be\n"
"\ta relative path and must not contain any \"..\" elements.\n"
"\tUsing default "__XCONFIGFILE__" search path.\n\n",
argv[i], argv[i]);
@ -1087,9 +1147,9 @@ ddxProcessArgument(int argc, char **argv, int i)
if (!strcmp(argv[i], "-configdir"))
{
CHECK_FOR_REQUIRED_ARGUMENT();
if (getuid() != 0 && !xf86PathIsSafe(argv[i + 1])) {
if (xf86PrivsElevated() && !xf86PathIsSafe(argv[i + 1])) {
FatalError("\nInvalid argument for %s\n"
"\tFor non-root users, the file specified with %s must be\n"
"\tWith elevated privileges, the file specified with %s must be\n"
"\ta relative path and must not contain any \"..\" elements.\n"
"\tUsing default "__XCONFIGDIR__" search path.\n\n",
argv[i], argv[i]);
@ -1375,7 +1435,7 @@ ddxUseMsg(void)
ErrorF("\n");
ErrorF("\n");
ErrorF("Device Dependent Usage\n");
if (getuid() == 0 || geteuid() != 0)
if (!xf86PrivsElevated())
{
ErrorF("-modulepath paths specify the module search path\n");
ErrorF("-logfile file specify a log file name\n");

1
hw/xfree86/common/xf86Priv.h
View File

@ -145,6 +145,7 @@ extern _X_EXPORT Bool xf86LoadModules(char **list, pointer *optlist);
extern _X_EXPORT int xf86SetVerbosity(int verb);
extern _X_EXPORT int xf86SetLogVerbosity(int verb);
extern _X_EXPORT Bool xf86CallDriverProbe( struct _DriverRec * drv, Bool detect_only );
extern _X_EXPORT Bool xf86PrivsElevated(void);
#endif /* _NO_XF86_PROTOTYPES */

6
include/xorg-config.h.in
View File

@ -130,4 +130,10 @@
/* Use libpciaccess */
#undef XSERVER_LIBPCIACCESS
/* Have setugid */
#undef HAVE_ISSETUGID
/* Have getresuid */
#undef HAVE_GETRESUID
#endif /* _XORG_CONFIG_H_ */