66 lines
1.8 KiB
Diff
66 lines
1.8 KiB
Diff
In rare cases droping groups with setgroups(0, NULL) is an operation
|
|
that can grant a user additional privileges. User namespaces were
|
|
allwoing that operation to unprivileged users and that had to be
|
|
fixed.
|
|
|
|
Update unshare --map-root-user to disable the setgroups operation
|
|
before setting the gid_map.
|
|
|
|
This is needed as after the security fix gid_map is restricted to
|
|
privileged users unless setgroups has been disabled.
|
|
|
|
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
|
|
---
|
|
include/pathnames.h | 1 +
|
|
sys-utils/unshare.c | 19 +++++++++++++++++++
|
|
2 files changed, 20 insertions(+)
|
|
|
|
diff --git a/include/pathnames.h b/include/pathnames.h
|
|
index 1cc4e15e6e4f..1c53e4554268 100644
|
|
--- a/include/pathnames.h
|
|
+++ b/include/pathnames.h
|
|
@@ -92,6 +92,7 @@
|
|
|
|
#define _PATH_PROC_UIDMAP "/proc/self/uid_map"
|
|
#define _PATH_PROC_GIDMAP "/proc/self/gid_map"
|
|
+#define _PATH_PROC_SETGROUPS "/proc/self/setgroups"
|
|
|
|
#define _PATH_PROC_ATTR_CURRENT "/proc/self/attr/current"
|
|
#define _PATH_PROC_ATTR_EXEC "/proc/self/attr/exec"
|
|
diff --git a/sys-utils/unshare.c b/sys-utils/unshare.c
|
|
index 95e4afbd055e..d409a7c936b6 100644
|
|
--- a/sys-utils/unshare.c
|
|
+++ b/sys-utils/unshare.c
|
|
@@ -39,6 +39,24 @@
|
|
#include "pathnames.h"
|
|
#include "all-io.h"
|
|
|
|
+static void disable_setgroups(void)
|
|
+{
|
|
+ const char *file = _PATH_PROC_SETGROUPS;
|
|
+ const char *deny = "deny";
|
|
+ int fd;
|
|
+
|
|
+ fd = open(file, O_WRONLY);
|
|
+ if (fd < 0) {
|
|
+ if (errno == ENOENT)
|
|
+ return;
|
|
+ err(EXIT_FAILURE, _("cannot open %s"), file);
|
|
+ }
|
|
+
|
|
+ if (write_all(fd, deny, strlen(deny)))
|
|
+ err(EXIT_FAILURE, _("write failed %s"), file);
|
|
+ close(fd);
|
|
+}
|
|
+
|
|
static void map_id(const char *file, uint32_t from, uint32_t to)
|
|
{
|
|
char *buf;
|
|
@@ -178,6 +196,7 @@ int main(int argc, char *argv[])
|
|
}
|
|
|
|
if (maproot) {
|
|
+ disable_setgroups();
|
|
map_id(_PATH_PROC_UIDMAP, 0, real_euid);
|
|
map_id(_PATH_PROC_GIDMAP, 0, real_egid);
|
|
}
|