source: MondoRescue/branches/3.3/mindi-busybox/loginutils/add-remove-shell.c@ 3621

/*
 * add-shell and remove-shell implementation for busybox
 *
 * Copyright (C) 2010 Nokia Corporation. All rights reserved.
 * Written by Alexander Shishkin <virtuoso@slind.org>
 *
 * Licensed under GPLv2 or later, see the LICENSE file in this source tree
 * for details.
 */
//config:config ADD_SHELL
//config:       bool "add-shell"
//config:       default y if DESKTOP
//config:       help
//config:         Add shells to /etc/shells.
//config:
//config:config REMOVE_SHELL
//config:       bool "remove-shell"
//config:       default y if DESKTOP
//config:       help
//config:         Remove shells from /etc/shells.

//applet:IF_ADD_SHELL(   APPLET_ODDNAME(add-shell   , add_remove_shell, BB_DIR_USR_SBIN, BB_SUID_DROP, add_shell   ))
//applet:IF_REMOVE_SHELL(APPLET_ODDNAME(remove-shell, add_remove_shell, BB_DIR_USR_SBIN, BB_SUID_DROP, remove_shell))

//kbuild:lib-$(CONFIG_ADD_SHELL)    += add-remove-shell.o
//kbuild:lib-$(CONFIG_REMOVE_SHELL) += add-remove-shell.o

//usage:#define add_shell_trivial_usage
//usage:       "SHELL..."
//usage:#define add_shell_full_usage "\n\n"
//usage:       "Add SHELLs to /etc/shells"

//usage:#define remove_shell_trivial_usage
//usage:       "SHELL..."
//usage:#define remove_shell_full_usage "\n\n"
//usage:       "Remove SHELLs from /etc/shells"

#include "libbb.h"

#define SHELLS_FILE "/etc/shells"

#define REMOVE_SHELL (ENABLE_REMOVE_SHELL && (!ENABLE_ADD_SHELL || applet_name[0] == 'r'))
#define ADD_SHELL    (ENABLE_ADD_SHELL && (!ENABLE_REMOVE_SHELL || applet_name[0] == 'a'))

/* NB: we use the _address_, not the value, of this string
 * as a "special value of pointer" in the code.
 */
static const char dont_add[] ALIGN1 = "\n";

int add_remove_shell_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int add_remove_shell_main(int argc UNUSED_PARAM, char **argv)
{
    FILE *orig_fp;
    char *orig_fn;
    char *new_fn;

    argv++;

    orig_fn = xmalloc_follow_symlinks(SHELLS_FILE);
    if (!orig_fn)
        return EXIT_FAILURE;
    orig_fp = fopen_for_read(orig_fn);

    new_fn = xasprintf("%s.tmp", orig_fn);
    /*
     * O_TRUNC or O_EXCL? At the first glance, O_EXCL looks better,
     * since it prevents races. But: (1) it requires a retry loop,
     * (2) if /etc/shells.tmp is *stale*, then retry loop
     * with O_EXCL will never succeed - it should have a timeout,
     * after which it should revert to O_TRUNC.
     * For now, I settle for O_TRUNC instead.
     */
    xmove_fd(xopen(new_fn, O_WRONLY | O_CREAT | O_TRUNC), STDOUT_FILENO);

    /* TODO:
    struct stat sb;
    xfstat(fileno(orig_fp), &sb);
    xfchown(STDOUT_FILENO, sb.st_uid, sb.st_gid);
    xfchmod(STDOUT_FILENO, sb.st_mode);
    */

    if (orig_fp) {
        /* Copy old file, possibly skipping removed shell names */
        char *line;
        while ((line = xmalloc_fgetline(orig_fp)) != NULL) {
            char **cpp = argv;
            while (*cpp) {
                if (strcmp(*cpp, line) == 0) {
                    /* Old file has this shell name */
                    if (REMOVE_SHELL) {
                        /* we are remove-shell */
                        /* delete this name by not copying it */
                        goto next_line;
                    }
                    /* we are add-shell */
                    /* mark this name as "do not add" */
                    *cpp = (char*)dont_add;
                }
                cpp++;
            }
            /* copy shell name from old to new file */
            puts(line);
 next_line:
            free(line);
        }
        if (ENABLE_FEATURE_CLEAN_UP)
            fclose(orig_fp);
    }

    if (ADD_SHELL) {
        char **cpp = argv;
        while (*cpp) {
            if (*cpp != dont_add)
                puts(*cpp);
            cpp++;
        }
    }

    /* Ensure we wrote out everything */
    if (fclose(stdout) != 0) {
        xunlink(new_fn);
        bb_perror_msg_and_die("%s: write error", new_fn);
    }

    /* Small hole: if rename fails, /etc/shells.tmp is not removed */
    xrename(new_fn, orig_fn);

    if (ENABLE_FEATURE_CLEAN_UP) {
        free(orig_fn);
        free(new_fn);
    }

    return EXIT_SUCCESS;
}