From 0a7915624ea4d3a629879e6a6fd79f432ffde016 Mon Sep 17 00:00:00 2001 From: Rob Landley Date: Thu, 4 Dec 2014 16:42:01 -0600 Subject: Add shred. --- toys/other/shred.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 toys/other/shred.c (limited to 'toys/other/shred.c') diff --git a/toys/other/shred.c b/toys/other/shred.c new file mode 100644 index 00000000..07d62c3d --- /dev/null +++ b/toys/other/shred.c @@ -0,0 +1,104 @@ +/* shred.c - Overwrite a file to securely delete + * + * Copyright 2014 Rob Landley + * + * No standard + +USE_SHRED(NEWTOY(shred, "<1zxus#<1n#<1o#<0f", TOYFLAG_USR|TOYFLAG_BIN)) + +config SHRED + bool "shred" + default n + help + usage: shred [-fuz] [-n COUNT] [-s SIZE] FILE... + + Securely delete a file by overwriting its contents with random data. + + -f Force (chmod if necessary) + -n COUNT Random overwrite iterations (default 1) + -o OFFSET Start at OFFSET + -s SIZE Use SIZE instead of detecting file size + -u unlink (actually delete file when done) + -x Use exact size (default without -s rounds up to next 4k) + -z zero at end + + Note: data journaling filesystems render this command useless, you must + overwrite all free space (fill up disk) to erase old data on those. +*/ + +#define FOR_shred +#include "toys.h" + +GLOBALS( + long offset; + long iterations; + long size; + + int ufd; +) + +void shred_main(void) +{ + char **try; + + if (!(toys.optflags & FLAG_n)) TT.iterations++; + TT.ufd = xopen("/dev/urandom", O_RDONLY); + + // We don't use loopfiles() here because "-" isn't stdin, and want to + // respond to files we can't open via chmod. + + for (try = toys.optargs; *try; try++) { + off_t pos = 0, len = TT.size; + int fd = open(*try, O_RDWR), iter = 0, throw; + + // do -f chmod if necessary + if (fd == -1 && (toys.optflags & FLAG_f)) { + chmod(*try, 0600); + fd = open(*try, O_RDWR); + } + if (fd == -1) { + perror_msg("%s", *try); + continue; + } + + // determine length + if (!len) len = fdlength(fd); + if (len<1) { + error_msg("%s: needs -s", *try); + close(fd); + continue; + } + + // Loop through, writing to this file + for (;;) { + // Advance to next -n or -z? + + if (pos >= len) { + pos = -1; + if (++iter == TT.iterations && (toys.optargs && FLAG_z)) { + memset(toybuf, 0, sizeof(toybuf)); + continue; + } + if (iter >= TT.iterations) break; + } + + if (pos < TT.offset) { + if (TT.offset != lseek(fd, TT.offset, SEEK_SET)) { + perror_msg("%s", *try); + break; + } + pos = TT.offset; + } + + // Determine length, read random data if not zeroing, write. + + throw = sizeof(toybuf); + if (toys.optflags & FLAG_x) + if (len-pos < throw) throw = len-pos; + + if (iter != TT.iterations) xread(TT.ufd, toybuf, throw); + if (throw != writeall(fd, toybuf, throw)) perror_msg("%s"); + pos += throw; + } + } +} -- cgit v1.2.3