For the threaded version we have to set uid,gid per thread instead
of per process. glibc setresuid() when called from a thread, it'll
send a signal to all other threads to synchronize the uid in all
other threads. To bypass this, we have to call syscall() directly.
Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
Reviewed-by: Steve Dickson <steved@xxxxxxxxxx>
---
utils/gssd/gssd_proc.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
index e2e95dc..de8dc07 100644
--- a/utils/gssd/gssd_proc.c
+++ b/utils/gssd/gssd_proc.c
@@ -69,6 +69,7 @@
#include <netdb.h>
#include <sys/types.h>
#include <sys/wait.h>
+#include <syscall.h>
#include "gssd.h"
#include "err_util.h"
@@ -436,7 +437,7 @@ change_identity(uid_t uid)
struct passwd *pw;
/* drop list of supplimentary groups first */
- if (setgroups(0, NULL) != 0) {
+ if (syscall(SYS_setgroups, 0, 0) != 0) {
printerr(0, "WARNING: unable to drop supplimentary groups!");
return errno;
}
@@ -453,20 +454,18 @@ change_identity(uid_t uid)
}
}
- /*
- * Switch the GIDs. Note that we leave the saved-set-gid alone in an
- * attempt to prevent attacks via ptrace()
+ /* Switch the UIDs and GIDs. */
+ /* For the threaded version we have to set uid,gid per thread instead
+ * of per process. glibc setresuid() when called from a thread, it'll
+ * send a signal to all other threads to synchronize the uid in all
+ * other threads. To bypass this, we have to call syscall() directly.
*/
- if (setresgid(pw->pw_gid, pw->pw_gid, -1) != 0) {
+ if (syscall(SYS_setresgid, pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
printerr(0, "WARNING: failed to set gid to %u!\n", pw->pw_gid);
return errno;
}
- /*
- * Switch UIDs, but leave saved-set-uid alone to prevent ptrace() by
- * other processes running with this uid.
- */
- if (setresuid(uid, uid, -1) != 0) {
+ if (syscall(SYS_setresuid, uid, uid, uid) != 0) {
printerr(0, "WARNING: Failed to setuid for user with uid %u\n",
uid);
return errno;
--
1.8.3.1
--
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