439 lines
9.7 KiB
C
439 lines
9.7 KiB
C
/* Minimal /bin/sh for in-container use.
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Copyright (C) 2018-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define _FILE_OFFSET_BITS 64
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sched.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <dirent.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <sys/fcntl.h>
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#include <sys/file.h>
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#include <sys/wait.h>
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#include <stdarg.h>
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#include <sys/sysmacros.h>
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#include <ctype.h>
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#include <utime.h>
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#include <errno.h>
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#include <error.h>
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#include <support/support.h>
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/* Design considerations
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General rule: optimize for developer time, not run time.
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Specifically:
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* Don't worry about slow algorithms
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* Don't worry about free'ing memory
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* Don't implement anything the testsuite doesn't need.
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* Line and argument counts are limited, see below.
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*/
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#define MAX_ARG_COUNT 100
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#define MAX_LINE_LENGTH 1000
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/* Debugging is enabled via --debug, which must be the first argument. */
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static int debug_mode = 0;
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#define dprintf if (debug_mode) fprintf
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/* Emulate the "/bin/true" command. Arguments are ignored. */
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static int
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true_func (char **argv)
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{
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return 0;
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}
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/* Emulate the "/bin/echo" command. Options are ignored, arguments
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are printed to stdout. */
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static int
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echo_func (char **argv)
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{
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int i;
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for (i = 0; argv[i]; i++)
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{
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if (i > 0)
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putchar (' ');
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fputs (argv[i], stdout);
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}
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putchar ('\n');
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return 0;
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}
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/* Emulate the "/bin/cp" command. Options are ignored. Only copies
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one source file to one destination file. Directory destinations
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are not supported. */
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static int
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copy_func (char **argv)
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{
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char *sname = argv[0];
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char *dname = argv[1];
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int sfd = -1, dfd = -1;
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struct stat st;
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int ret = 1;
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sfd = open (sname, O_RDONLY);
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if (sfd < 0)
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{
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fprintf (stderr, "cp: unable to open %s for reading: %s\n",
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sname, strerror (errno));
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return 1;
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}
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if (fstat (sfd, &st) < 0)
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{
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fprintf (stderr, "cp: unable to fstat %s: %s\n",
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sname, strerror (errno));
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goto out;
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}
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dfd = open (dname, O_WRONLY | O_TRUNC | O_CREAT, 0600);
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if (dfd < 0)
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{
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fprintf (stderr, "cp: unable to open %s for writing: %s\n",
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dname, strerror (errno));
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goto out;
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}
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if (support_copy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
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{
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fprintf (stderr, "cp: cannot copy file %s to %s: %s\n",
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sname, dname, strerror (errno));
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goto out;
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}
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ret = 0;
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chmod (dname, st.st_mode & 0777);
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out:
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if (sfd >= 0)
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close (sfd);
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if (dfd >= 0)
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close (dfd);
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return ret;
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}
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/* Emulate the 'exit' builtin. The exit value is optional. */
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static int
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exit_func (char **argv)
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{
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int exit_val = 0;
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if (argv[0] != 0)
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exit_val = atoi (argv[0]) & 0xff;
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exit (exit_val);
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return 0;
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}
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/* Emulate the "/bin/kill" command. Options are ignored. */
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static int
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kill_func (char **argv)
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{
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int signum = SIGTERM;
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int i;
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for (i = 0; argv[i]; i++)
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{
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pid_t pid;
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if (strcmp (argv[i], "$$") == 0)
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pid = getpid ();
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else
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pid = atoi (argv[i]);
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kill (pid, signum);
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}
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return 0;
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}
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/* This is a list of all the built-in commands we understand. */
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static struct {
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const char *name;
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int (*func) (char **argv);
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} builtin_funcs[] = {
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{ "true", true_func },
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{ "echo", echo_func },
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{ "cp", copy_func },
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{ "exit", exit_func },
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{ "kill", kill_func },
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{ NULL, NULL }
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};
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/* Run one tokenized command. argv[0] is the command. argv is
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NULL-terminated. */
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static void
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run_command_array (char **argv)
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{
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int i, j;
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pid_t pid;
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int status;
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int (*builtin_func) (char **args);
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if (argv[0] == NULL)
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return;
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builtin_func = NULL;
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int new_stdin = 0;
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int new_stdout = 1;
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int new_stderr = 2;
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dprintf (stderr, "run_command_array starting\n");
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for (i = 0; argv[i]; i++)
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dprintf (stderr, " argv [%d] `%s'\n", i, argv[i]);
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for (j = i = 0; argv[i]; i++)
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{
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if (strcmp (argv[i], "<") == 0 && argv[i + 1])
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{
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new_stdin = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
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++i;
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continue;
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}
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if (strcmp (argv[i], ">") == 0 && argv[i + 1])
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{
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new_stdout = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
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++i;
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continue;
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}
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if (strcmp (argv[i], ">>") == 0 && argv[i + 1])
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{
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new_stdout = open (argv[i + 1], O_WRONLY|O_CREAT|O_APPEND, 0777);
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++i;
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continue;
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}
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if (strcmp (argv[i], "2>") == 0 && argv[i + 1])
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{
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new_stderr = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
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++i;
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continue;
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}
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argv[j++] = argv[i];
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}
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argv[j] = NULL;
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for (i = 0; builtin_funcs[i].name != NULL; i++)
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if (strcmp (argv[0], builtin_funcs[i].name) == 0)
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builtin_func = builtin_funcs[i].func;
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dprintf (stderr, "builtin %p argv0 `%s'\n", builtin_func, argv[0]);
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pid = fork ();
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if (pid < 0)
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{
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fprintf (stderr, "sh: fork failed\n");
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exit (1);
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}
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if (pid == 0)
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{
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if (new_stdin != 0)
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{
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dup2 (new_stdin, 0);
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close (new_stdin);
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}
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if (new_stdout != 1)
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{
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dup2 (new_stdout, 1);
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close (new_stdout);
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}
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if (new_stderr != 2)
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{
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dup2 (new_stderr, 2);
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close (new_stderr);
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}
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if (builtin_func != NULL)
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exit (builtin_func (argv + 1));
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execvp (argv[0], argv);
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fprintf (stderr, "sh: execing %s failed: %s",
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argv[0], strerror (errno));
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exit (127);
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}
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waitpid (pid, &status, 0);
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dprintf (stderr, "exiting run_command_array\n");
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if (WIFEXITED (status))
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{
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int rv = WEXITSTATUS (status);
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if (rv)
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exit (rv);
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}
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else if (WIFSIGNALED (status))
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{
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int sig = WTERMSIG (status);
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raise (sig);
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}
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else
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exit (1);
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}
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/* Run one command-as-a-string, by tokenizing it. Limited to
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MAX_ARG_COUNT arguments. Simple substitution is done of $1 to $9
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(as whole separate tokens) from iargs[]. Quoted strings work if
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the quotes wrap whole tokens; i.e. "foo bar" but not foo" bar". */
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static void
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run_command_string (const char *cmdline, const char **iargs)
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{
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char *args[MAX_ARG_COUNT+1];
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int ap = 0;
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const char *start, *end;
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int nargs;
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for (nargs = 0; iargs[nargs] != NULL; ++nargs)
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;
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dprintf (stderr, "run_command_string starting: '%s'\n", cmdline);
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while (ap < MAX_ARG_COUNT)
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{
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/* If the argument is quoted, this is the quote character, else NUL. */
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int in_quote = 0;
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/* Skip whitespace up to the next token. */
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while (*cmdline && isspace (*cmdline))
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cmdline ++;
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if (*cmdline == 0)
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break;
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start = cmdline;
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/* Check for quoted argument. */
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in_quote = (*cmdline == '\'' || *cmdline == '"') ? *cmdline : 0;
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/* Skip to end of token; either by whitespace or matching quote. */
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dprintf (stderr, "in_quote %d\n", in_quote);
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while (*cmdline
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&& (!isspace (*cmdline) || in_quote))
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{
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if (*cmdline == in_quote
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&& cmdline != start)
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in_quote = 0;
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dprintf (stderr, "[%c]%d ", *cmdline, in_quote);
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cmdline ++;
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}
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dprintf (stderr, "\n");
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/* Allocate space for this token and store it in args[]. */
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end = cmdline;
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dprintf (stderr, "start<%s> end<%s>\n", start, end);
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args[ap] = (char *) xmalloc (end - start + 1);
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memcpy (args[ap], start, end - start);
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args[ap][end - start] = 0;
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/* Strip off quotes, if found. */
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dprintf (stderr, "args[%d] = <%s>\n", ap, args[ap]);
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if (args[ap][0] == '\''
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&& args[ap][strlen (args[ap])-1] == '\'')
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{
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args[ap][strlen (args[ap])-1] = 0;
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args[ap] ++;
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}
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else if (args[ap][0] == '"'
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&& args[ap][strlen (args[ap])-1] == '"')
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{
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args[ap][strlen (args[ap])-1] = 0;
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args[ap] ++;
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}
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/* Replace positional parameters like $4. */
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else if (args[ap][0] == '$'
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&& isdigit (args[ap][1])
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&& args[ap][2] == 0)
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{
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int a = args[ap][1] - '1';
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if (0 <= a && a < nargs)
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args[ap] = strdup (iargs[a]);
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}
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ap ++;
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if (*cmdline == 0)
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break;
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}
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/* Lastly, NULL terminate the array and run it. */
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args[ap] = NULL;
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run_command_array (args);
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}
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/* Run a script by reading lines and passing them to the above
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function. */
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static void
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run_script (const char *filename, const char **args)
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{
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char line[MAX_LINE_LENGTH + 1];
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dprintf (stderr, "run_script starting: '%s'\n", filename);
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FILE *f = fopen (filename, "r");
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if (f == NULL)
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{
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fprintf (stderr, "sh: %s: %s\n", filename, strerror (errno));
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exit (1);
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}
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while (fgets (line, sizeof (line), f) != NULL)
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{
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if (line[0] == '#')
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{
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dprintf (stderr, "comment: %s\n", line);
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continue;
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}
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run_command_string (line, args);
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}
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fclose (f);
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}
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int
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main (int argc, const char **argv)
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{
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int i;
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if (strcmp (argv[1], "--debug") == 0)
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{
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debug_mode = 1;
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--argc;
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++argv;
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}
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dprintf (stderr, "container-sh starting:\n");
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for (i = 0; i < argc; i++)
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dprintf (stderr, " argv[%d] is `%s'\n", i, argv[i]);
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if (strcmp (argv[1], "-c") == 0)
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run_command_string (argv[2], argv+3);
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else
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run_script (argv[1], argv+2);
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dprintf (stderr, "normal exit 0\n");
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return 0;
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}
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