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Commit 3aa0f0cc authored by Andre Eisenbach's avatar Andre Eisenbach Committed by Myles Watson
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DO NOT MERGE : Re-land: SMP: Validate remote elliptic curve points 

Fixes: 72377774
Test: net_test_stack_smp (where applicable)
(cherry picked from commit 9fd31a04)
Change-Id: Ic38ad2f447a6a675025c84fd7746c9124f1eb324
parent 21d18e1a

system/stack/smp/p_256_ecc_pp.cc

+22 −0
Original line number Diff line number Diff line
@@ -245,3 +245,25 @@ void ECC_PointMult_Bin_NAF(Point* q, Point* p, uint32_t* n, 
  multiprecision_mersenns_mult_mod(q->z, q->z, minus_p.x, keyLength);

  multiprecision_mersenns_mult_mod(q->y, q->y, q->z, keyLength);

}



bool ECC_ValidatePoint(const Point& pt) {

  const size_t kl = KEY_LENGTH_DWORDS_P256;

  p_256_init_curve(kl);



  // Ensure y^2 = x^3 + a*x + b (mod p); a = -3



  // y^2 mod p

  uint32_t y2_mod[kl] = {0};

  multiprecision_mersenns_squa_mod(y2_mod, (uint32_t*)pt.y, kl);



  // Right hand side calculation

  uint32_t rhs[kl] = {0};

  multiprecision_mersenns_squa_mod(rhs, (uint32_t*)pt.x, kl);

  uint32_t three[kl] = {0};

  three[0] = 3;

  multiprecision_sub_mod(rhs, rhs, three, kl);

  multiprecision_mersenns_mult_mod(rhs, rhs, (uint32_t*)pt.x, kl);

  multiprecision_add_mod(rhs, rhs, curve_p256.b, kl);



  return multiprecision_compare(rhs, y2_mod, kl) == 0;

}

system/stack/smp/p_256_ecc_pp.h

+3 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 


#pragma once



#include <cstdbool>

#include "p_256_multprecision.h"



typedef struct {
@@ -55,6 +56,8 @@ typedef struct { 
extern elliptic_curve_t curve;

extern elliptic_curve_t curve_p256;



bool ECC_ValidatePoint(const Point& p);



void ECC_PointMult_Bin_NAF(Point* q, Point* p, uint32_t* n, uint32_t keyLength);



#define ECC_PointMult(q, p, n, keyLength) \

system/stack/smp/smp_act.cc

+12 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include "include/bt_target.h"

#include "stack/btm/btm_int.h"

#include "stack/include/l2c_api.h"

#include "stack/smp/p_256_ecc_pp.h"

#include "stack/smp/smp_int.h"

#include "utils/include/bt_utils.h"
@@ -655,6 +656,17 @@ void smp_process_pairing_public_key(tSMP_CB* p_cb, tSMP_INT_DATA* p_data) { 


  STREAM_TO_ARRAY(p_cb->peer_publ_key.x, p, BT_OCTET32_LEN);

  STREAM_TO_ARRAY(p_cb->peer_publ_key.y, p, BT_OCTET32_LEN);



  Point pt;

  memcpy(pt.x, p_cb->peer_publ_key.x, BT_OCTET32_LEN);

  memcpy(pt.y, p_cb->peer_publ_key.y, BT_OCTET32_LEN);



  if (!ECC_ValidatePoint(pt)) {

    android_errorWriteLog(0x534e4554, "72377774");

    smp_sm_event(p_cb, SMP_AUTH_CMPL_EVT, &reason);

    return;

  }



  p_cb->flags |= SMP_PAIR_FLAG_HAVE_PEER_PUBL_KEY;



  smp_wait_for_both_public_keys(p_cb, NULL);