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modtrezorutils: add consteq

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This commit is contained in:
Jan Pochyla 2017-09-26 17:26:34 +02:00
parent f22edd7609
commit 7d31bdcf78
1 changed files with 29 additions and 0 deletions
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29
embed/extmod/modtrezorutils/modtrezorutils.c
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@ -12,6 +12,34 @@
#include <string.h>
#include "common.h"
/// def consteq(sec: bytes, pub: bytes) -> bool:
/// '''
/// Compares the private information in `sec` with public, user-provided
/// information in `pub`. Runs in constant time, corresponding to a length
/// of `pub`. Can access memory behind valid length of `sec`, caller is
/// expected to avoid any invalid memory access.
/// '''
STATIC mp_obj_t mod_trezorutils_consteq(mp_obj_t sec, mp_obj_t pub) {
mp_buffer_info_t secbuf;
mp_get_buffer_raise(sec, &secbuf, MP_BUFFER_READ);
mp_buffer_info_t pubbuf;
mp_get_buffer_raise(pub, &pubbuf, MP_BUFFER_READ);
size_t diff = secbuf.len - pubbuf.len;
for (size_t i = 0; i < pubbuf.len; i++) {
const uint8_t *s = (uint8_t *)secbuf.buf;
const uint8_t *p = (uint8_t *)pubbuf.buf;
diff |= s[i] - p[i];
}
if (diff == 0) {
return mp_const_true;
} else {
return mp_const_false;
}
}
STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorutils_consteq_obj, mod_trezorutils_consteq);
/// def memcpy(dst: bytearray, dst_ofs: int,
/// src: bytearray, src_ofs: int,
/// n: int) -> int:
@ -68,6 +96,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorutils_halt_obj, 0, 1, mod_t
STATIC const mp_rom_map_elem_t mp_module_trezorutils_globals_table[] = {
{ MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_trezorutils) },
{ MP_ROM_QSTR(MP_QSTR_consteq), MP_ROM_PTR(&mod_trezorutils_consteq_obj) },
{ MP_ROM_QSTR(MP_QSTR_memcpy), MP_ROM_PTR(&mod_trezorutils_memcpy_obj) },
{ MP_ROM_QSTR(MP_QSTR_halt), MP_ROM_PTR(&mod_trezorutils_halt_obj) },
};