110 lines
2.1 KiB
C
110 lines
2.1 KiB
C
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#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/stat.h>
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#define RAND_SOURCE "/dev/urandom"
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#define ZERO_SOURCE "/dev/zero"
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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 zero_fd, int fd, unsigned int iter) {
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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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lseek(fd, 0, SEEK_SET);
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char buf[1];
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while (size) {
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if (iter == n_loops && z_flag)
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read(zero_fd, buf, sizeof(buf));
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else
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read(rand_fd, buf, sizeof(buf));
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write(fd, buf, sizeof(buf));
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size--;
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}
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fsync(fd);
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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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char *val = strchr(argv[i], '=');
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if (!val)
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break;
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val[0] = '\0';
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n_loops = atoi(val + 1);
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}
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else if (!strcmp(argv[i], "-h")) {
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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...]\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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int zero_fd = open(ZERO_SOURCE, O_RDONLY);
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if (zero_fd < 0) {
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fprintf(stderr, "shred: %s is %s\n", ZERO_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_WRONLY);
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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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for (unsigned int n = 0; n <= n_loops; n++)
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shred(rand_fd, zero_fd, fd, n);
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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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close(zero_fd);
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return 0;
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}
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