Problem - Kevin Tafuro

spc_file_wipe( )
A wrapper around the first function, which uses a FILE object instead of a file
descriptor. If an error occurs while performing the wipe operation, the return
value is –1; otherwise, a successful operation returns zero.
SpcWipeFile( )
A Windows-specific function that uses the Win32 API for file access. It requires
an open file handle as its only argument and returns a boolean indicating success
or failure.
Note that for all three functions, the file descriptor, FILE object, or file handle passed
as an argument must be open with write access to the file to be wiped; otherwise, the
wiping functions will fail. As written, these functions will probably not work very
well on media other than disk because they are constantly seeking back to the beginning
of the file. Another issue that may arise is filesystem caching. All the writes
made to the file may not actually be written to the physical media.
#include
#include
#include
#include
#include
#include
#include
#define SPC_WIPE_BUFSIZE 4096
static int write_data(int fd, const void *buf, size_t nbytes) {
size_t towrite, written = 0;
ssize_t result;
do {
if (nbytes - written > SSIZE_MAX) towrite = SSIZE_MAX;
else towrite = nbytes - written;
if ((result = write(fd, (const char *)buf + written, towrite)) >= 0)
written += result;
else if (errno != EINTR) return 0;
} while (written < nbytes);
return 1;
}
static int random_pass(int fd, size_t nbytes)
{
size_t towrite;
unsigned char buf[SPC_WIPE_BUFSIZE];
if (lseek(fd, 0, SEEK_SET) != 0) return -1;
while (nbytes > 0) {
towrite = (nbytes > sizeof(buf) ? sizeof(buf) : nbytes);
spc_rand(buf, towrite);
if (!write_data(fd, buf, towrite)) return -1;
nbytes -= towrite;
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Erasing Files Securely | 49