1/* Minimal /bin/sh for in-container use.
2 Copyright (C) 2018-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#define _FILE_OFFSET_BITS 64
20
21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
24#include <sched.h>
25#include <sys/syscall.h>
26#include <unistd.h>
27#include <sys/types.h>
28#include <dirent.h>
29#include <string.h>
30#include <sys/stat.h>
31#include <sys/fcntl.h>
32#include <sys/file.h>
33#include <sys/wait.h>
34#include <stdarg.h>
35#include <sys/sysmacros.h>
36#include <ctype.h>
37#include <utime.h>
38#include <errno.h>
39#include <error.h>
40
41#include <support/support.h>
42
43/* Design considerations
44
45 General rule: optimize for developer time, not run time.
46
47 Specifically:
48
49 * Don't worry about slow algorithms
50 * Don't worry about free'ing memory
51 * Don't implement anything the testsuite doesn't need.
52 * Line and argument counts are limited, see below.
53
54*/
55
56#define MAX_ARG_COUNT 100
57#define MAX_LINE_LENGTH 1000
58
59/* Debugging is enabled via --debug, which must be the first argument. */
60static int debug_mode = 0;
61#define dprintf if (debug_mode) fprintf
62
63/* Emulate the "/bin/true" command. Arguments are ignored. */
64static int
65true_func (char **argv)
66{
67 return 0;
68}
69
70/* Emulate the "/bin/echo" command. Options are ignored, arguments
71 are printed to stdout. */
72static int
73echo_func (char **argv)
74{
75 int i;
76
77 for (i = 0; argv[i]; i++)
78 {
79 if (i > 0)
80 putchar (' ');
81 fputs (argv[i], stdout);
82 }
83 putchar ('\n');
84
85 return 0;
86}
87
88/* Emulate the "/bin/cp" command. Options are ignored. Only copies
89 one source file to one destination file. Directory destinations
90 are not supported. */
91static int
92copy_func (char **argv)
93{
94 char *sname = argv[0];
95 char *dname = argv[1];
96 int sfd, dfd;
97 struct stat st;
98
99 sfd = open (sname, O_RDONLY);
100 if (sfd < 0)
101 {
102 fprintf (stderr, "cp: unable to open %s for reading: %s\n",
103 sname, strerror (errno));
104 return 1;
105 }
106
107 if (fstat (sfd, &st) < 0)
108 {
109 fprintf (stderr, "cp: unable to fstat %s: %s\n",
110 sname, strerror (errno));
111 return 1;
112 }
113
114 dfd = open (dname, O_WRONLY | O_TRUNC | O_CREAT, 0600);
115 if (dfd < 0)
116 {
117 fprintf (stderr, "cp: unable to open %s for writing: %s\n",
118 dname, strerror (errno));
119 return 1;
120 }
121
122 if (support_copy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
123 {
124 fprintf (stderr, "cp: cannot copy file %s to %s: %s\n",
125 sname, dname, strerror (errno));
126 return 1;
127 }
128
129 close (sfd);
130 close (dfd);
131
132 chmod (dname, st.st_mode & 0777);
133
134 return 0;
135
136}
137
138/* Emulate the 'exit' builtin. The exit value is optional. */
139static int
140exit_func (char **argv)
141{
142 int exit_val = 0;
143
144 if (argv[0] != 0)
145 exit_val = atoi (argv[0]) & 0xff;
146 exit (exit_val);
147 return 0;
148}
149
150/* Emulate the "/bin/kill" command. Options are ignored. */
151static int
152kill_func (char **argv)
153{
154 int signum = SIGTERM;
155 int i;
156
157 for (i = 0; argv[i]; i++)
158 {
159 pid_t pid;
160 if (strcmp (argv[i], "$$") == 0)
161 pid = getpid ();
162 else
163 pid = atoi (argv[i]);
164 kill (pid, signum);
165 }
166 return 0;
167}
168
169/* This is a list of all the built-in commands we understand. */
170static struct {
171 const char *name;
172 int (*func) (char **argv);
173} builtin_funcs[] = {
174 { "true", true_func },
175 { "echo", echo_func },
176 { "cp", copy_func },
177 { "exit", exit_func },
178 { "kill", kill_func },
179 { NULL, NULL }
180};
181
182/* Run one tokenized command. argv[0] is the command. argv is
183 NULL-terminated. */
184static void
185run_command_array (char **argv)
186{
187 int i, j;
188 pid_t pid;
189 int status;
190 int (*builtin_func) (char **args);
191
192 if (argv[0] == NULL)
193 return;
194
195 builtin_func = NULL;
196
197 int new_stdin = 0;
198 int new_stdout = 1;
199 int new_stderr = 2;
200
201 dprintf (stderr, "run_command_array starting\n");
202 for (i = 0; argv[i]; i++)
203 dprintf (stderr, " argv [%d] `%s'\n", i, argv[i]);
204
205 for (j = i = 0; argv[i]; i++)
206 {
207 if (strcmp (argv[i], "<") == 0 && argv[i + 1])
208 {
209 new_stdin = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
210 ++i;
211 continue;
212 }
213 if (strcmp (argv[i], ">") == 0 && argv[i + 1])
214 {
215 new_stdout = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
216 ++i;
217 continue;
218 }
219 if (strcmp (argv[i], ">>") == 0 && argv[i + 1])
220 {
221 new_stdout = open (argv[i + 1], O_WRONLY|O_CREAT|O_APPEND, 0777);
222 ++i;
223 continue;
224 }
225 if (strcmp (argv[i], "2>") == 0 && argv[i + 1])
226 {
227 new_stderr = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
228 ++i;
229 continue;
230 }
231 argv[j++] = argv[i];
232 }
233 argv[j] = NULL;
234
235
236 for (i = 0; builtin_funcs[i].name != NULL; i++)
237 if (strcmp (argv[0], builtin_funcs[i].name) == 0)
238 builtin_func = builtin_funcs[i].func;
239
240 dprintf (stderr, "builtin %p argv0 `%s'\n", builtin_func, argv[0]);
241
242 pid = fork ();
243 if (pid < 0)
244 {
245 fprintf (stderr, "sh: fork failed\n");
246 exit (1);
247 }
248
249 if (pid == 0)
250 {
251 if (new_stdin != 0)
252 {
253 dup2 (new_stdin, 0);
254 close (new_stdin);
255 }
256 if (new_stdout != 1)
257 {
258 dup2 (new_stdout, 1);
259 close (new_stdout);
260 }
261 if (new_stderr != 2)
262 {
263 dup2 (new_stderr, 2);
264 close (new_stderr);
265 }
266
267 if (builtin_func != NULL)
268 exit (builtin_func (argv + 1));
269
270 execvp (argv[0], argv);
271
272 fprintf (stderr, "sh: execing %s failed: %s",
273 argv[0], strerror (errno));
274 exit (127);
275 }
276
277 waitpid (pid, &status, 0);
278
279 dprintf (stderr, "exiting run_command_array\n");
280
281 if (WIFEXITED (status))
282 {
283 int rv = WEXITSTATUS (status);
284 if (rv)
285 exit (rv);
286 }
287 else if (WIFSIGNALED (status))
288 {
289 int sig = WTERMSIG (status);
290 raise (sig);
291 }
292 else
293 exit (1);
294}
295
296/* Run one command-as-a-string, by tokenizing it. Limited to
297 MAX_ARG_COUNT arguments. Simple substitution is done of $1 to $9
298 (as whole separate tokens) from iargs[]. Quoted strings work if
299 the quotes wrap whole tokens; i.e. "foo bar" but not foo" bar". */
300static void
301run_command_string (const char *cmdline, const char **iargs)
302{
303 char *args[MAX_ARG_COUNT+1];
304 int ap = 0;
305 const char *start, *end;
306 int nargs;
307
308 for (nargs = 0; iargs[nargs] != NULL; ++nargs)
309 ;
310
311 dprintf (stderr, "run_command_string starting: '%s'\n", cmdline);
312
313 while (ap < MAX_ARG_COUNT)
314 {
315 /* If the argument is quoted, this is the quote character, else NUL. */
316 int in_quote = 0;
317
318 /* Skip whitespace up to the next token. */
319 while (*cmdline && isspace (*cmdline))
320 cmdline ++;
321 if (*cmdline == 0)
322 break;
323
324 start = cmdline;
325 /* Check for quoted argument. */
326 in_quote = (*cmdline == '\'' || *cmdline == '"') ? *cmdline : 0;
327
328 /* Skip to end of token; either by whitespace or matching quote. */
329 dprintf (stderr, "in_quote %d\n", in_quote);
330 while (*cmdline
331 && (!isspace (*cmdline) || in_quote))
332 {
333 if (*cmdline == in_quote
334 && cmdline != start)
335 in_quote = 0;
336 dprintf (stderr, "[%c]%d ", *cmdline, in_quote);
337 cmdline ++;
338 }
339 dprintf (stderr, "\n");
340
341 /* Allocate space for this token and store it in args[]. */
342 end = cmdline;
343 dprintf (stderr, "start<%s> end<%s>\n", start, end);
344 args[ap] = (char *) xmalloc (end - start + 1);
345 memcpy (args[ap], start, end - start);
346 args[ap][end - start] = 0;
347
348 /* Strip off quotes, if found. */
349 dprintf (stderr, "args[%d] = <%s>\n", ap, args[ap]);
350 if (args[ap][0] == '\''
351 && args[ap][strlen (args[ap])-1] == '\'')
352 {
353 args[ap][strlen (args[ap])-1] = 0;
354 args[ap] ++;
355 }
356
357 else if (args[ap][0] == '"'
358 && args[ap][strlen (args[ap])-1] == '"')
359 {
360 args[ap][strlen (args[ap])-1] = 0;
361 args[ap] ++;
362 }
363
364 /* Replace positional parameters like $4. */
365 else if (args[ap][0] == '$'
366 && isdigit (args[ap][1])
367 && args[ap][2] == 0)
368 {
369 int a = args[ap][1] - '1';
370 if (0 <= a && a < nargs)
371 args[ap] = strdup (iargs[a]);
372 }
373
374 ap ++;
375
376 if (*cmdline == 0)
377 break;
378 }
379
380 /* Lastly, NULL terminate the array and run it. */
381 args[ap] = NULL;
382 run_command_array (args);
383}
384
385/* Run a script by reading lines and passing them to the above
386 function. */
387static void
388run_script (const char *filename, const char **args)
389{
390 char line[MAX_LINE_LENGTH + 1];
391 dprintf (stderr, "run_script starting: '%s'\n", filename);
392 FILE *f = fopen (filename, "r");
393 if (f == NULL)
394 {
395 fprintf (stderr, "sh: %s: %s\n", filename, strerror (errno));
396 exit (1);
397 }
398 while (fgets (line, sizeof (line), f) != NULL)
399 {
400 if (line[0] == '#')
401 {
402 dprintf (stderr, "comment: %s\n", line);
403 continue;
404 }
405 run_command_string (line, args);
406 }
407 fclose (f);
408}
409
410int
411main (int argc, const char **argv)
412{
413 int i;
414
415 if (strcmp (argv[1], "--debug") == 0)
416 {
417 debug_mode = 1;
418 --argc;
419 ++argv;
420 }
421
422 dprintf (stderr, "container-sh starting:\n");
423 for (i = 0; i < argc; i++)
424 dprintf (stderr, " argv[%d] is `%s'\n", i, argv[i]);
425
426 if (strcmp (argv[1], "-c") == 0)
427 run_command_string (argv[2], argv+3);
428 else
429 run_script (argv[1], argv+2);
430
431 dprintf (stderr, "normal exit 0\n");
432 return 0;
433}
434