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-rw-r--r--toys/other/nsenter.c66
1 files changed, 59 insertions, 7 deletions
diff --git a/toys/other/nsenter.c b/toys/other/nsenter.c
index 8f548bf0..6748ace8 100644
--- a/toys/other/nsenter.c
+++ b/toys/other/nsenter.c
@@ -13,33 +13,36 @@
// Note: flags go in same order (right to left) for shared subset
USE_NSENTER(NEWTOY(nsenter, "<1F(no-fork)t#<1(target)i:(ipc);m:(mount);n:(net);p:(pid);u:(uts);U:(user);", TOYFLAG_USR|TOYFLAG_BIN))
-USE_UNSHARE(NEWTOY(unshare, "<1^imnpuU", TOYFLAG_USR|TOYFLAG_BIN))
+USE_UNSHARE(NEWTOY(unshare, "<1^rimnpuU", TOYFLAG_USR|TOYFLAG_BIN))
config UNSHARE
bool "unshare"
default y
depends on TOYBOX_CONTAINER
help
- usage: unshare [-imnpuU] COMMAND...
+ usage: unshare [-imnpuUr] COMMAND...
- Create new namespace(s) for this process and its children, so some
- attribute is not shared with the parent process. This is part of
- Linux Containers. Each process can have its own:
+ Create new container namespace(s) for this process and its children, so
+ some attribute is not shared with the parent process.
-i SysV IPC (message queues, semaphores, shared memory)
-m Mount/unmount tree
-n Network address, sockets, routing, iptables
-p Process IDs and init
+ -r Become root (map current euid/egid to 0/0, implies -U)
-u Host and domain names
-U UIDs, GIDs, capabilities
+ A namespace allows a set of processes to have a different view of the
+ system than other sets of processes.
+
config NSENTER
bool "nsenter"
default n
help
usage: nsenter [-t pid] [-F] [-i] [-m] [-n] [-p] [-u] [-U] COMMAND...
- Run COMMAND in a different set of namespaces.
+ Run COMMAND in an existing (set of) namespace(s).
-t PID to take namespaces from (--target)
-F don't fork, even if -p is used (--no-fork)
@@ -68,18 +71,62 @@ GLOBALS(
long targetpid;
)
+// Code that must run in unshare's flag context
+#define CLEANUP_nsenter
+#define FOR_unshare
+#include <generated/flags.h>
+
+static void write_ugid_map(char *map, unsigned eugid)
+{
+ int bytes = sprintf(toybuf, "0 %u 1", eugid), fd = xopen(map, O_WRONLY);
+
+ xwrite(fd, toybuf, bytes);
+ xclose(fd);
+}
+
+
+static int handle_r(int test)
+{
+ int fd;
+
+ if (!CFG_UNSHARE || !(toys.optflags & FLAG_r) || *toys.which->name!='u')
+ return 0;
+ if (!test) return 1;
+
+ if (toys.optflags & FLAG_r) {
+ if ((fd = open("/proc/self/setgroups", O_WRONLY)) >= 0) {
+ xwrite(fd, "deny", 4);
+ close(fd);
+ }
+
+ write_ugid_map("/proc/self/uid_map", geteuid());
+ write_ugid_map("/proc/self/gid_map", getegid());
+ }
+
+ return 0;
+}
+
+// Shift back to the context GLOBALS lives in (I.E. matching the filename).
+#define CLEANUP_unshare
+#define FOR_nsenter
+#include <generated/flags.h>
+
void unshare_main(void)
{
unsigned flags[]={CLONE_NEWUSER, CLONE_NEWUTS, CLONE_NEWPID, CLONE_NEWNET,
CLONE_NEWNS, CLONE_NEWIPC}, f = 0;
int i, fd;
+ // unshare -U does not imply -r, so we cannot use [+rU]
+ if (handle_r(0)) toys.optflags |= FLAG_U;
+
// Create new namespace(s)?
- if (CFG_UNSHARE && toys.which->name[0]) {
+ if (CFG_UNSHARE && *toys.which->name=='u') {
for (i = 0; i<ARRAY_LEN(flags); i++)
if (toys.optflags & (1<<i)) f |= flags[i];
if (unshare(f)) perror_exit(0);
+ handle_r(1);
// Bind to existing namespace(s)?
} else if (CFG_NSENTER) {
@@ -114,3 +161,8 @@ void unshare_main(void)
xexec(toys.optargs);
}
+
+void nsenter_main(void)
+{
+ unshare_main();
+}