1/* nsenter.c - Enter existing namespaces 2 * 3 * Copyright 2014 Andy Lutomirski <luto@amacapital.net> 4 * 5 * See http://man7.org/linux/man-pages/man1/nsenter.1.html 6 * 7 * unshare.c - run command in new context 8 * 9 * Copyright 2011 Rob Landley <rob@landley.net> 10 * 11 * See http://man7.org/linux/man-pages/man1/unshare.1.html 12 * 13 14// Note: flags go in same order (right to left) for shared subset 15USE_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)) 16USE_UNSHARE(NEWTOY(unshare, "<1^f(fork);r(map-root-user);i:(ipc);m:(mount);n:(net);p:(pid);u:(uts);U:(user);", TOYFLAG_USR|TOYFLAG_BIN)) 17 18config 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 -f Fork command in the background (--fork) 29 -i SysV IPC (message queues, semaphores, shared memory) (--ipc) 30 -m Mount/unmount tree (--mount) 31 -n Network address, sockets, routing, iptables (--net) 32 -p Process IDs and init (--pid) 33 -r Become root (map current euid/egid to 0/0, implies -U) (--map-root-user) 34 -u Host and domain names (--uts) 35 -U UIDs, GIDs, capabilities (--user) 36 37 A namespace allows a set of processes to have a different view of the 38 system than other sets of processes. 39 40config NSENTER 41 bool "nsenter" 42 depends on TOYBOX_CONTAINER 43 default y 44 help 45 usage: nsenter [-t pid] [-F] [-i] [-m] [-n] [-p] [-u] [-U] COMMAND... 46 47 Run COMMAND in an existing (set of) namespace(s). 48 49 -t PID to take namespaces from (--target) 50 -F don't fork, even if -p is used (--no-fork) 51 52 The namespaces to switch are: 53 54 -i SysV IPC: message queues, semaphores, shared memory (--ipc) 55 -m Mount/unmount tree (--mount) 56 -n Network address, sockets, routing, iptables (--net) 57 -p Process IDs and init, will fork unless -F is used (--pid) 58 -u Host and domain names (--uts) 59 -U UIDs, GIDs, capabilities (--user) 60 61 If -t isn't specified, each namespace argument must provide a path 62 to a namespace file, ala "-i=/proc/$PID/ns/ipc" 63*/ 64 65#define FOR_nsenter 66#include "toys.h" 67#include <sys/syscall.h> 68#include <linux/sched.h> 69 70#define unshare(flags) syscall(SYS_unshare, flags) 71#define setns(fd, nstype) syscall(SYS_setns, fd, nstype) 72 73GLOBALS( 74 char *Uupnmi[6]; 75 long t; 76) 77 78// Code that must run in unshare's flag context 79#define CLEANUP_nsenter 80#define FOR_unshare 81#include <generated/flags.h> 82 83static void write_ugid_map(char *map, unsigned eugid) 84{ 85 int fd = xopen(map, O_WRONLY); 86 87 dprintf(fd, "0 %u 1", eugid); 88 xclose(fd); 89} 90 91static void handle_r(int euid, int egid) 92{ 93 int fd; 94 95 if ((fd = open("/proc/self/setgroups", O_WRONLY)) >= 0) { 96 xwrite(fd, "deny", 4); 97 close(fd); 98 } 99 100 write_ugid_map("/proc/self/uid_map", euid); 101 write_ugid_map("/proc/self/gid_map", egid); 102} 103 104static int test_r() 105{ 106 return toys.optflags & FLAG_r; 107} 108 109static int test_f() 110{ 111 return toys.optflags & FLAG_f; 112} 113 114// Shift back to the context GLOBALS lives in (I.E. matching the filename). 115#define CLEANUP_unshare 116#define FOR_nsenter 117#include <generated/flags.h> 118 119void unshare_main(void) 120{ 121 unsigned flags[]={CLONE_NEWUSER, CLONE_NEWUTS, CLONE_NEWPID, CLONE_NEWNET, 122 CLONE_NEWNS, CLONE_NEWIPC}, f = 0; 123 int i, fd; 124 125 // Create new namespace(s)? 126 if (CFG_UNSHARE && *toys.which->name=='u') { 127 // For -r, we have to save our original [ug]id before calling unshare() 128 int euid = geteuid(), egid = getegid(); 129 130 // unshare -U does not imply -r, so we cannot use [+rU] 131 if (test_r()) toys.optflags |= FLAG_U; 132 133 for (i = 0; i<ARRAY_LEN(flags); i++) 134 if (toys.optflags & (1<<i)) f |= flags[i]; 135 136 if (unshare(f)) perror_exit(0); 137 if (test_r()) handle_r(euid, egid); 138 139 if (test_f()) { 140 toys.exitval = xrun(toys.optargs); 141 142 return; 143 } 144 // Bind to existing namespace(s)? 145 } else if (CFG_NSENTER) { 146 char *nsnames = "user\0uts\0pid\0net\0mnt\0ipc"; 147 148 for (i = 0; i<ARRAY_LEN(flags); i++) { 149 char *filename = TT.Uupnmi[i]; 150 151 if (toys.optflags & (1<<i)) { 152 if (!filename || !*filename) { 153 if (!(toys.optflags & FLAG_t)) error_exit("need -t or =filename"); 154 sprintf(toybuf, "/proc/%ld/ns/%s", TT.t, nsnames); 155 filename = toybuf; 156 } 157 158 if (setns(fd = xopenro(filename), flags[i])) perror_exit("setns"); 159 close(fd); 160 } 161 nsnames += strlen(nsnames)+1; 162 } 163 164 if ((toys.optflags & FLAG_p) && !(toys.optflags & FLAG_F)) { 165 toys.exitval = xrun(toys.optargs); 166 167 return; 168 } 169 } 170 171 xexec(toys.optargs); 172} 173 174void nsenter_main(void) 175{ 176 unshare_main(); 177} 178