more ssss work

extmod/modtrezorcrypto/modtrezorcrypto-ssss.h

@@ -7,6 +7,9 @@
 
 #include "py/objstr.h"
 
+#include "trezor-crypto/bignum.h"
+#include "ssss.h"
+
 typedef struct _mp_obj_SSSS_t {
     mp_obj_base_t base;
 } mp_obj_SSSS_t;
@@ -27,12 +30,23 @@ STATIC mp_obj_t mod_TrezorCrypto_SSSS_split(size_t n_args, const mp_obj_t *args)
     mp_int_t n = mp_obj_get_int(args[2]);
     mp_buffer_info_t secret;
     mp_get_buffer_raise(args[3], &secret, MP_BUFFER_READ);
-    (void)m;
+    if (secret.len != 32) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Length of the secret has to be 256 bits"));
+    }
+    if (m < 1 || n < 1 || m > 15 || n > 15 || m > n) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Invalid number of shares"));
+    }
+    bignum256 sk;
+    bignum256 shares[n];
+    bn_read_be(secret.buf, &sk);
+    if (!ssss_split(&sk, m, n, shares)) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Error splitting secret"));
+    }
     mp_obj_tuple_t *tuple = MP_OBJ_TO_PTR(mp_obj_new_tuple(n, NULL));
     vstr_t vstr[n];
     for (int i = 0; i < n; i++) {
         vstr_init_len(&vstr[i], secret.len);
-        memcpy(vstr[i].buf, secret.buf, secret.len);
+        bn_write_be(&shares[i], secret.buf);
         tuple->items[i] = mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr[i]);
     }
     return MP_OBJ_FROM_PTR(tuple);
@@ -44,16 +58,37 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_TrezorCrypto_SSSS_split_obj, 4, 4
 /// Combine M shares of Shamir's Secret Sharing Scheme into secret
 ///
 STATIC mp_obj_t mod_TrezorCrypto_SSSS_combine(mp_obj_t self, mp_obj_t shares) {
-    mp_obj_tuple_t *tuple = MP_OBJ_TO_PTR(shares);
-    mp_int_t m = 0;
-    mp_int_t n = tuple->len;
-    for (int i = 0; i < n; i++) {
-        mp_obj_t share = tuple->items[i];
-        if (share != mp_const_none) {
-            m++;
+    mp_uint_t n;
+    mp_obj_t *share;
+    if (MP_OBJ_IS_TYPE(shares, &mp_type_tuple)) {
+        mp_obj_tuple_get(shares, &n, &share);
+    } else
+    if (MP_OBJ_IS_TYPE(shares, &mp_type_list)) {
+        mp_obj_list_get(shares, &n, &share);
+    } else {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "List or tuple expected"));
+    }
+    if (n < 1 || n > 15) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Invalid number of shares"));
+    }
+    bignum256 bnshares[n];
+    for (mp_uint_t i = 0; i < n; i++) {
+        if (MP_OBJ_IS_TYPE(share[i], &mp_type_bytes)) {
+            mp_buffer_info_t s;
+            mp_get_buffer_raise(share[i], &s, MP_BUFFER_READ);
+            bn_read_be(s.buf, &bnshares[n]);
+        } else {
+            memset(&bnshares[i], 0, sizeof(bignum256));
         }
     }
-    return tuple->items[0];
+    bignum256 sk;
+    if (!ssss_combine(bnshares, n, &sk)) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Error combining secret"));
+    }
+    vstr_t vstr;
+    vstr_init_len(&vstr, 32);
+    bn_write_be(&sk, (uint8_t *)vstr.buf);
+    return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_TrezorCrypto_SSSS_combine_obj, mod_TrezorCrypto_SSSS_combine);
 

extmod/modtrezorcrypto/ssss.c

@@ -0,0 +1,14 @@
+#include "ssss.h"
+
+bool ssss_split(const bignum256 *secret, int m, int n, bignum256 *shares)
+{
+	if (m < 1 || n < 1 || m > 15 || n > 15 || m > n) {
+		return false;
+	}
+	return true;
+}
+
+bool ssss_combine(const bignum256 *shares, int n, bignum256 *secret)
+{
+	return true;
+}

extmod/modtrezorcrypto/ssss.h

@@ -0,0 +1,10 @@
+#ifndef __SSSS_H__
+#define __SSSS_H__
+
+#include <stdbool.h>
+#include "bignum.h"
+
+bool ssss_split(const bignum256 *secret, int m, int n, bignum256 *shares);
+bool ssss_combine(const bignum256 *shares, int n, bignum256 *secret);
+
+#endif

vendor/micropython

@@ -1 +1 @@
-Subproject commit 4509a515d6057d2fca4b642b055108c2ff6bf78b
+Subproject commit 579656fb2f3c020b4e1c94d3ac8b5f3eb249bcb7