1 /* nsenter.c - Enter existing namespaces 2 * 3 * Copyright 2014 Andy Lutomirski <luto (at) 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 (at) 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 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^f(fork);r(map-root-user);i:(ipc);m:(mount);n:(net);p:(pid);u:(uts);U:(user);", 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 -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 40 config 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 <linux/sched.h> 68 int unshare(int flags); 69 int setns(int fd, int nstype); 70 71 GLOBALS( 72 char *nsnames[6]; 73 long targetpid; 74 ) 75 76 // Code that must run in unshare's flag context 77 #define CLEANUP_nsenter 78 #define FOR_unshare 79 #include <generated/flags.h> 80 81 static void write_ugid_map(char *map, unsigned eugid) 82 { 83 int bytes = sprintf(toybuf, "0 %u 1", eugid), fd = xopen(map, O_WRONLY); 84 85 xwrite(fd, toybuf, bytes); 86 xclose(fd); 87 } 88 89 static void handle_r(int euid, int egid) 90 { 91 int fd; 92 93 if ((fd = open("/proc/self/setgroups", O_WRONLY)) >= 0) { 94 xwrite(fd, "deny", 4); 95 close(fd); 96 } 97 98 write_ugid_map("/proc/self/uid_map", euid); 99 write_ugid_map("/proc/self/gid_map", egid); 100 } 101 102 static int test_r() 103 { 104 return toys.optflags & FLAG_r; 105 } 106 107 static int test_f() 108 { 109 return toys.optflags & FLAG_f; 110 } 111 112 // Shift back to the context GLOBALS lives in (I.E. matching the filename). 113 #define CLEANUP_unshare 114 #define FOR_nsenter 115 #include <generated/flags.h> 116 117 void unshare_main(void) 118 { 119 unsigned flags[]={CLONE_NEWUSER, CLONE_NEWUTS, CLONE_NEWPID, CLONE_NEWNET, 120 CLONE_NEWNS, CLONE_NEWIPC}, f = 0; 121 int i, fd; 122 123 // Create new namespace(s)? 124 if (CFG_UNSHARE && *toys.which->name=='u') { 125 // For -r, we have to save our original [ug]id before calling unshare() 126 int euid = geteuid(), egid = getegid(); 127 128 // unshare -U does not imply -r, so we cannot use [+rU] 129 if (test_r()) toys.optflags |= FLAG_U; 130 131 for (i = 0; i<ARRAY_LEN(flags); i++) 132 if (toys.optflags & (1<<i)) f |= flags[i]; 133 134 if (unshare(f)) perror_exit(0); 135 if (test_r()) handle_r(euid, egid); 136 137 if (test_f()) { 138 toys.exitval = xrun(toys.optargs); 139 140 return; 141 } 142 // Bind to existing namespace(s)? 143 } else if (CFG_NSENTER) { 144 char *nsnames = "user\0uts\0pid\0net\0mnt\0ipc"; 145 146 for (i = 0; i<ARRAY_LEN(flags); i++) { 147 char *filename = TT.nsnames[i]; 148 149 if (toys.optflags & (1<<i)) { 150 if (!filename || !*filename) { 151 if (!(toys.optflags & FLAG_t)) error_exit("need -t or =filename"); 152 sprintf(toybuf, "/proc/%ld/ns/%s", TT.targetpid, nsnames); 153 filename = toybuf; 154 } 155 156 if (setns(fd = xopenro(filename), flags[i])) perror_exit("setns"); 157 close(fd); 158 } 159 nsnames += strlen(nsnames)+1; 160 } 161 162 if ((toys.optflags & FLAG_p) && !(toys.optflags & FLAG_F)) { 163 toys.exitval = xrun(toys.optargs); 164 165 return; 166 } 167 } 168 169 xexec(toys.optargs); 170 } 171 172 void nsenter_main(void) 173 { 174 unshare_main(); 175 } 176
