1 /* nsenter.c - Enter existing namespaces
2 *
3 * Copyright 2014 andy Lutomirski <luto@amacapital.net>
4 *
5 * No standard
6 *
7 * unshare.c - run command in new context
8 *
9 * Copyright 2011 Rob Landley <rob@landley.net>
10 *
11 * No Standard
12 *
13
14 // Note: flags go in same order (right to left) for shared subset
15 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))
16 USE_UNSHARE(NEWTOY(unshare, "<1^rimnpuU", TOYFLAG_USR|TOYFLAG_BIN))
17
18 config UNSHARE
19 bool "unshare"
20 default y
21 depends on TOYBOX_CONTAINER
22 help
23 usage: unshare [-imnpuUr] COMMAND...
24
25 Create new container namespace(s) for this process and its children, so
26 some attribute is not shared with the parent process.
27
28 -i SysV IPC (message queues, semaphores, shared memory)
29 -m Mount/unmount tree
30 -n Network address, sockets, routing, iptables
31 -p Process IDs and init
32 -r Become root (map current euid/egid to 0/0, implies -U)
33 -u Host and domain names
34 -U UIDs, GIDs, capabilities
35
36 A namespace allows a set of processes to have a different view of the
37 system than other sets of processes.
38
39 config NSENTER
40 bool "nsenter"
41 default y
42 help
43 usage: nsenter [-t pid] [-F] [-i] [-m] [-n] [-p] [-u] [-U] COMMAND...
44
45 Run COMMAND in an existing (set of) namespace(s).
46
47 -t PID to take namespaces from (--target)
48 -F don't fork, even if -p is used (--no-fork)
49
50 The namespaces to switch are:
51
52 -i SysV IPC: message queues, semaphores, shared memory (--ipc)
53 -m Mount/unmount tree (--mnt)
54 -n Network address, sockets, routing, iptables (--net)
55 -p Process IDs and init, will fork unless -F is used (--pid)
56 -u Host and domain names (--uts)
57 -U UIDs, GIDs, capabilities (--user)
58
59 If -t isn't specified, each namespace argument must provide a path
60 to a namespace file, ala "-i=/proc/$PID/ns/ipc"
61 */
62
63 #define FOR_nsenter
64 #include "toys.h"
65 #include <linux/sched.h>
66 int unshare(int flags);
67 int setns(int fd, int nstype);
68
GLOBALS(char * nsnames[6];long targetpid;)69 GLOBALS(
70 char *nsnames[6];
71 long targetpid;
72 )
73
74 // Code that must run in unshare's flag context
75 #define CLEANUP_nsenter
76 #define FOR_unshare
77 #include <generated/flags.h>
78
79 static void write_ugid_map(char *map, unsigned eugid)
80 {
81 int bytes = sprintf(toybuf, "0 %u 1", eugid), fd = xopen(map, O_WRONLY);
82
83 xwrite(fd, toybuf, bytes);
84 xclose(fd);
85 }
86
handle_r(int euid,int egid)87 static void handle_r(int euid, int egid)
88 {
89 int fd;
90
91 if ((fd = open("/proc/self/setgroups", O_WRONLY)) >= 0) {
92 xwrite(fd, "deny", 4);
93 close(fd);
94 }
95
96 write_ugid_map("/proc/self/uid_map", euid);
97 write_ugid_map("/proc/self/gid_map", egid);
98 }
99
test_r()100 static int test_r()
101 {
102 return toys.optflags & FLAG_r;
103 }
104
105 // Shift back to the context GLOBALS lives in (I.E. matching the filename).
106 #define CLEANUP_unshare
107 #define FOR_nsenter
108 #include <generated/flags.h>
109
unshare_main(void)110 void unshare_main(void)
111 {
112 unsigned flags[]={CLONE_NEWUSER, CLONE_NEWUTS, CLONE_NEWPID, CLONE_NEWNET,
113 CLONE_NEWNS, CLONE_NEWIPC}, f = 0;
114 int i, fd;
115
116 // Create new namespace(s)?
117 if (CFG_UNSHARE && *toys.which->name=='u') {
118 // For -r, we have to save our original [ug]id before calling unshare()
119 int euid = geteuid(), egid = getegid();
120
121 // unshare -U does not imply -r, so we cannot use [+rU]
122 if (test_r()) toys.optflags |= FLAG_U;
123
124 for (i = 0; i<ARRAY_LEN(flags); i++)
125 if (toys.optflags & (1<<i)) f |= flags[i];
126
127 if (unshare(f)) perror_exit(0);
128 if (test_r()) handle_r(euid, egid);
129
130 // Bind to existing namespace(s)?
131 } else if (CFG_NSENTER) {
132 char *nsnames = "user\0uts\0pid\0net\0mnt\0ipc";
133
134 for (i = 0; i<ARRAY_LEN(flags); i++) {
135 char *filename = TT.nsnames[i];
136
137 if (toys.optflags & (1<<i)) {
138 if (!filename || !*filename) {
139 if (!(toys.optflags & FLAG_t)) error_exit("need -t or =filename");
140 sprintf(toybuf, "/proc/%ld/ns/%s", TT.targetpid, nsnames);
141 filename = toybuf;
142 }
143
144 if (setns(fd = xopen(filename, O_RDONLY), flags[i]))
145 perror_exit("setns");
146 close(fd);
147 }
148 nsnames += strlen(nsnames)+1;
149 }
150
151 if ((toys.optflags & FLAG_p) && !(toys.optflags & FLAG_F)) {
152 pid_t pid = xfork();
153
154 if (pid) {
155 while (waitpid(pid, 0, 0) == -1 && errno == EINTR);
156 return;
157 }
158 }
159 }
160
161 xexec(toys.optargs);
162 }
163
nsenter_main(void)164 void nsenter_main(void)
165 {
166 unshare_main();
167 }
168