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#include <err.h>
#include <errno.h>
#include <getopt.h>
#include <inttypes.h>
#include <libgen.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>
#include <time.h>
#include "base32.h"
#include "common.h"
#include "hmac.h"
#include "sha1.h"
#include "xendian.h"
static void process(const char *, size_t);
static void process_stdin(void);
static inline uint32_t pow32(uint32_t, uint32_t)
__attribute__((always_inline, const));
static inline bool xisdigit(char)
__attribute__((always_inline, const));
static inline bool bigendian(void)
__attribute__((always_inline, const));
static int digits = 6, period = 30;
static noreturn void
usage(const char *argv0)
{
fprintf(stderr,
"Usage: %s [-d digits] [-p period] [secret]\n"
" %s -h\n",
argv0, argv0);
exit(EXIT_FAILURE);
}
int
main(int argc, char **argv)
{
int opt;
static const struct option longopts[] = {
{"digits", required_argument, 0, 'd'},
{"help", no_argument, 0, 'h'},
{"period", required_argument, 0, 'p'},
{0},
};
argv[0] = basename(argv[0]);
while ((opt = getopt_long(argc, argv, "d:hp:", longopts, NULL)) != -1) {
switch (opt) {
case 'h':
/* TODO: Open the manual page! */
usage(argv[0]);
break;
case 'd':
case 'p': {
/* strtol() allows for numbers with leading spaces and a
‘+’/‘-’. We don’t want that, so assert that the input
begins with a number. */
if (!xisdigit(optarg[0]))
errx(1, "%s: Invalid integer", optarg);
char *endptr;
long n = strtol(optarg, &endptr, 10);
/* There are trailing invalid digits */
if (*endptr != 0)
errx(1, "%s: Invalid integer", optarg);
/* The number was too large. We asserted that the input
didn’t start with ‘-’ so we can ignore checking for
LONG_MIN. */
if (n > INT_MAX)
errno = ERANGE;
err(1, "%s", optarg);
}
if (n == 0)
errx(1, "%s: Integer must be non-zero", optarg);
if (opt == 'd')
digits = (int)n;
else
period = (int)n;
break;
}
default:
usage(argv[0]);
}
}
argc -= optind;
argv += optind;
switch (argc) {
case 0:
process_stdin();
break;
case 1:
process(argv[0], strlen(argv[0]));
break;
default:
usage(argv[-optind]);
}
return EXIT_SUCCESS;
}
void
process_stdin(void)
{
ssize_t nr;
size_t len;
char *line = NULL;
while ((nr = getline(&line, &len, stdin)) != -1) {
if (line[nr - 1] == '\n')
line[--nr] = 0;
process(line, nr);
}
if (errno != 0)
err(1, "getline");
}
void
process(const char *s, size_t n)
{
/* Remove padding bytes */
while (n > 0 && s[n - 1] == '=')
n--;
if (n == 0)
errx(1, "Empty Base32 input");
static uint8_t _key[256];
uint8_t *key = _key;
size_t keysz = n * 5 / 8;
if (keysz > sizeof(_key)) {
if ((key = malloc(keysz)) == NULL)
err(1, "malloc");
}
if (!b32toa(key, s, n))
errx(1, "%s: Invalid Base32 input", s);
/* time(2) claims that this call will never fail if passed a NULL
argument. We cast the time_t to uint64_t which will always be
safe to do. */
uint64_t epoch = htobe64((uint64_t)time(NULL) / (uint64_t)period);
uint8_t dgst[SHA1DGSTSZ];
hmac_sha1(dgst, key, keysz, (uint8_t *)&epoch, sizeof(epoch));
int off = dgst[19] & 0x0F;
uint32_t binc = (dgst[off + 0] & 0x7F) << 24
| (dgst[off + 1] & 0xFF) << 16
| (dgst[off + 2] & 0xFF) << 8
| (dgst[off + 3] & 0xFF) << 0;
printf("%0*" PRId32 "\n", digits, binc % pow32(10, digits));
if (key != _key)
free(key);
}
/* TODO: Check for overflow? */
uint32_t
pow32(uint32_t x, uint32_t y)
{
uint32_t n = x;
if (y == 0)
return 1;
while (--y != 0)
x *= n;
return x;
}
bool
xisdigit(char ch)
{
return ch >= '0' && ch <= '9';
}
bool
bigendian(void)
{
union {
uint16_t u16;
uint8_t u8[2];
} u = {
.u16 = 0x0102,
};
u.u16 = 0x0102U;
return u.u8[0] == 1;
}
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