100 lines
1.9 KiB
C
100 lines
1.9 KiB
C
#include <stdio.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#define RAND_SOURCE "/dev/urandom"
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unsigned int f_flag;
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unsigned int u_flag;
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unsigned int z_flag;
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unsigned int n_loops;
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int shred(int rand_fd, int fd) {
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/* Get size */
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off_t size = lseek(fd, 0, SEEK_END);
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if (size <= 0)
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return 1;
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void *buf = mmap(NULL, size, PROT_WRITE, MAP_SHARED, fd, 0);
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if (buf == MAP_FAILED) {
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fprintf(stderr, "shred: mmap: %s\n", strerror(errno));
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return 1;
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}
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for (unsigned int n = 0; n < n_loops; n++) {
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read(rand_fd, buf, size);
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fsync(fd);
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}
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if (z_flag)
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memset(buf, 0, size);
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if (munmap(buf, size)) {
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fprintf(stderr, "shred: munmap: %s\n", strerror(errno));
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return 1;
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}
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return 0;
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}
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int main(const int argc, const char **argv) {
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n_loops = 3;
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int i;
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for (i = 1; i < argc; i++) {
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if (argv[i][0] != '-')
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break;
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else if (!strcmp(argv[i], "-f"))
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f_flag = 1;
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else if (!strcmp(argv[i], "-u"))
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u_flag = 1;
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else if (!strcmp(argv[i], "-z"))
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z_flag = 1;
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else if (!strncmp(argv[i], "-n=", 3))
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n_loops = atoi(argv[i] + 3);
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else if (!strcmp(argv[i], "--help")) {
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printf("shred [-n=N Overwrite N times (default 3)] [-z Final overwrite with zeros] [-u Remove file] [-f Chmod to ensure writability] [file file2...]\n");
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return 1;
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}
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}
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int rand_fd = open(RAND_SOURCE, O_RDONLY);
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if (rand_fd < 0) {
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fprintf(stderr, "shred: %s is %s\n", RAND_SOURCE, strerror(errno));
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return 1;
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}
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for (; i < argc; i++) {
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int fd = open(argv[i], O_RDWR);
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if (fd < 0) {
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fprintf(stderr, "shred: %s is %s\n", argv[i], strerror(errno));
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continue;
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}
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shred(rand_fd, fd);
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close(fd);
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if (u_flag)
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if (unlink(argv[i]) < 0)
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fprintf(stderr, "shred: %s is %s\n", argv[i], strerror(errno));
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if (f_flag)
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if (chmod(argv[i], 0) < 0)
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fprintf(stderr, "shred: %s is %s\n", argv[i], strerror(errno));
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}
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close(rand_fd);
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return 0;
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}
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