LXR busybox/coreutils/shred.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
   4 *
   5 * Licensed under GPLv2, see file LICENSE in this source tree.
   6 */
   7//config:config SHRED
   8//config:       bool "shred (5 kb)"
   9//config:       default y
  10//config:       help
  11//config:       Overwrite a file to hide its contents, and optionally delete it
  12
  13//applet:IF_SHRED(APPLET(shred, BB_DIR_USR_BIN, BB_SUID_DROP))
  14
  15//kbuild:lib-$(CONFIG_SHRED) += shred.o
  16
  17//usage:#define shred_trivial_usage
  18//usage:       "FILE..."
  19//usage:#define shred_full_usage "\n\n"
  20//usage:       "Overwrite/delete FILEs\n"
  21//usage:     "\n        -f      Chmod to ensure writability"
  22//usage:     "\n        -n N    Overwrite N times (default 3)"
  23//usage:     "\n        -z      Final overwrite with zeros"
  24//usage:     "\n        -u      Remove file"
  25//-x and -v are accepted but have no effect
  26
  27/* shred (GNU coreutils) 8.25:
  28-f, --force             change permissions to allow writing if necessary
  29-u                      truncate and remove file after overwriting
  30-z, --zero              add a final overwrite with zeros to hide shredding
  31-n, --iterations=N      overwrite N times instead of the default (3)
  32-v, --verbose           show progress
  33-x, --exact             do not round file sizes up to the next full block; this is the default for non-regular files
  34--random-source=FILE    get random bytes from FILE
  35-s, --size=N            shred this many bytes (suffixes like K, M, G accepted)
  36--remove[=HOW]          like -u but give control on HOW to delete;  See below
  37*/
  38
  39#include "libbb.h"
  40
  41int shred_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  42int shred_main(int argc UNUSED_PARAM, char **argv)
  43{
  44        int rand_fd = rand_fd; /* for compiler */
  45        int zero_fd;
  46        unsigned num_iter = 3;
  47        unsigned opt;
  48        enum {
  49                OPT_f = (1 << 0),
  50                OPT_u = (1 << 1),
  51                OPT_z = (1 << 2),
  52                OPT_n = (1 << 3),
  53                OPT_v = (1 << 4),
  54                OPT_x = (1 << 5),
  55        };
  56
  57        opt = getopt32(argv, "fuzn:+vx", &num_iter);
  58        argv += optind;
  59
  60        zero_fd = xopen("/dev/zero", O_RDONLY);
  61        if (num_iter != 0)
  62                rand_fd = xopen("/dev/urandom", O_RDONLY);
  63
  64        if (!*argv)
  65                bb_show_usage();
  66
  67        for (;;) {
  68                struct stat sb;
  69                const char *fname;
  70                unsigned i;
  71                int fd;
  72
  73                fname = *argv++;
  74                if (!fname)
  75                        break;
  76                fd = -1;
  77                if (opt & OPT_f) {
  78                        fd = open(fname, O_WRONLY);
  79                        if (fd < 0)
  80                                chmod(fname, 0666);
  81                }
  82                if (fd < 0)
  83                        fd = xopen(fname, O_WRONLY);
  84
  85                if (fstat(fd, &sb) == 0 && sb.st_size > 0) {
  86                        off_t size = sb.st_size;
  87
  88                        for (i = 0; i < num_iter; i++) {
  89                                bb_copyfd_size(rand_fd, fd, size);
  90                                fdatasync(fd);
  91                                xlseek(fd, 0, SEEK_SET);
  92                        }
  93                        if (opt & OPT_z) {
  94                                bb_copyfd_size(zero_fd, fd, size);
  95                                fdatasync(fd);
  96                        }
  97                        if (opt & OPT_u) {
  98                                ftruncate(fd, 0);
  99                                xunlink(fname);
 100                        }
 101                        xclose(fd);
 102                }
 103        }
 104
 105        return EXIT_SUCCESS;
 106}
 107