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Move a couple functions from crypto_sign to crypto_core/curve25519

Browse Source 
This improves clarity and makes it easier to reuse these in a
different context.

Also change fe_isnonzero() to fe_zero() and make it work as
documented.
This commit is contained in:
Frank Denis
2017-10-21 21:24:25 +02:00
parent 9fc0ece3d9
commit 88417977e3
5 changed files with 129 additions and 128 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libsodium/crypto_core/curve25519/ref10/curve25519_ref10.c
+115 -8
View File
@@ -3,7 +3,9 @@
#include <string.h>
#include "crypto_verify_32.h"
#include "private/common.h"
#include "private/curve25519_ref10.h"
#include "utils.h"
static inline uint64_t
load_3(const unsigned char *in)
@@ -441,21 +443,19 @@ fe_isnegative(const fe f)
/*
return 1 if f == 0
return 0 if f != 0
*
Preconditions:
|f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
*/
static unsigned char zero[32];
int
fe_isnonzero(const fe f)
fe_iszero(const fe f)
{
unsigned char s[32];
fe_tobytes(s, f);
return crypto_verify_32(s, zero);
return sodium_is_zero(s, 32);
}
/*
@@ -1433,9 +1433,9 @@ ge_frombytes_negate_vartime(ge_p3 *h, const unsigned char *s)
fe_sq(vxx, h->X);
fe_mul(vxx, vxx, v);
fe_sub(check, vxx, u); /* vx^2-u */
if (fe_isnonzero(check)) {
if (fe_iszero(check) == 0) {
fe_add(check, vxx, u); /* vx^2+u */
if (fe_isnonzero(check)) {
if (fe_iszero(check) == 0) {
return -1;
}
fe_mul(h->X, h->X, sqrtm1);
@@ -2037,7 +2037,7 @@ ge_scalarmult_base(ge_p3 *h, const unsigned char *a)
}
/* multiply by the order of the main subgroup l = 2^252+27742317777372353535851937790883648493 */
void
static void
ge_mul_l(ge_p3 *r, const ge_p3 *A)
{
static const signed char aslide[253] = {
@@ -2091,6 +2091,91 @@ ge_mul_l(ge_p3 *r, const ge_p3 *A)
}
}
int
ge_is_on_main_subgroup(const ge_p3 *p)
{
ge_p3 pl;
ge_mul_l(&pl, p);
return fe_iszero(pl.X);
}
int
ge_has_small_order(const unsigned char s[32], unsigned char neg)
{
CRYPTO_ALIGN(16)
static const unsigned char blacklist[][32] = {
/* 0 (order 4) */
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
/* 1 (order 1) */
{ 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
/* 2707385501144840649318225287225658788936804267575313519463743609750303402022
(order 8) */
{ 0x26, 0xe8, 0x95, 0x8f, 0xc2, 0xb2, 0x27, 0xb0, 0x45, 0xc3, 0xf4,
0x89, 0xf2, 0xef, 0x98, 0xf0, 0xd5, 0xdf, 0xac, 0x05, 0xd3, 0xc6,
0x33, 0x39, 0xb1, 0x38, 0x02, 0x88, 0x6d, 0x53, 0xfc, 0x05 },
/* 55188659117513257062467267217118295137698188065244968500265048394206261417927
(order 8) */
{ 0xc7, 0x17, 0x6a, 0x70, 0x3d, 0x4d, 0xd8, 0x4f, 0xba, 0x3c, 0x0b,
0x76, 0x0d, 0x10, 0x67, 0x0f, 0x2a, 0x20, 0x53, 0xfa, 0x2c, 0x39,
0xcc, 0xc6, 0x4e, 0xc7, 0xfd, 0x77, 0x92, 0xac, 0x03, 0x7a },
/* p-1 (order 2) */
{ 0x13, 0xe8, 0x95, 0x8f, 0xc2, 0xb2, 0x27, 0xb0, 0x45, 0xc3, 0xf4,
0x89, 0xf2, 0xef, 0x98, 0xf0, 0xd5, 0xdf, 0xac, 0x05, 0xd3, 0xc6,
0x33, 0x39, 0xb1, 0x38, 0x02, 0x88, 0x6d, 0x53, 0xfc, 0x85 },
/* p (order 4) */
{ 0xb4, 0x17, 0x6a, 0x70, 0x3d, 0x4d, 0xd8, 0x4f, 0xba, 0x3c, 0x0b,
0x76, 0x0d, 0x10, 0x67, 0x0f, 0x2a, 0x20, 0x53, 0xfa, 0x2c, 0x39,
0xcc, 0xc6, 0x4e, 0xc7, 0xfd, 0x77, 0x92, 0xac, 0x03, 0xfa },
/* p+1 (order 1) */
{ 0xec, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* p+2707385501144840649318225287225658788936804267575313519463743609750303402022
(order 8) */
{ 0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* p+55188659117513257062467267217118295137698188065244968500265048394206261417927
(order 8) */
{ 0xee, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* 2p-1 (order 2) */
{ 0xd9, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
/* 2p (order 4) */
{ 0xda, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
/* 2p+1 (order 1) */
{ 0xdb, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }
};
size_t i, j;
unsigned char c;
neg <<= 7;
for (i = 0; i < sizeof blacklist / sizeof blacklist[0]; i++) {
c = 0;
for (j = 0; j < 31; j++) {
c |= s[j] ^ blacklist[i][j];
}
c |= s[j] ^ blacklist[i][j] ^ neg;
if (c == 0) {
return 1;
}
}
return 0;
}
/*
Input:
a[0]+256*a[1]+...+256^31*a[31] = a
@@ -2912,3 +2997,25 @@ sc_reduce(unsigned char *s)
s[30] = s11 >> 9;
s[31] = s11 >> 17;
}
int
sc_is_less_than_L(const unsigned char *s)
{
/* 2^252+27742317777372353535851937790883648493 */
static const unsigned char L[32] = {
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7,
0xa2, 0xde, 0xf9, 0xde, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
};
unsigned char c = 0;
unsigned char n = 1;
unsigned int i = 32;
do {
i--;
c |= ((s[i] - L[i]) >> 8) & n;
n &= ((s[i] ^ L[i]) - 1) >> 8;
} while (i != 0);
return (c != 0);
}
src/libsodium/crypto_sign/ed25519/ref10/ed25519_ref10.h
-3
View File
@@ -15,7 +15,4 @@ int _crypto_sign_ed25519_verify_detached(const unsigned char *sig,
unsigned long long mlen,
const unsigned char *pk,
int prehashed);
int _crypto_sign_ed25519_small_order(const unsigned char p[32], unsigned char neg);
#endif
src/libsodium/crypto_sign/ed25519/ref10/keypair.c
+6 -14
View File
@@ -16,14 +16,10 @@ crypto_sign_ed25519_scalarmult(unsigned char *q, const unsigned char *n,
unsigned char *t = q;
ge_p3 Q;
ge_p3 P;
ge_p3 pl;
if (_crypto_sign_ed25519_small_order(p, 1) ||
ge_frombytes_negate_vartime(&P, p) != 0) {
return -1;
}
ge_mul_l(&pl, &P);
if (fe_isnonzero(pl.X)) {
if (ge_has_small_order(p, 1) != 0 ||
ge_frombytes_negate_vartime(&P, p) != 0 ||
ge_is_on_main_subgroup(&P) == 0) {
return -1;
}
memmove(t, n, 32);
@@ -79,16 +75,12 @@ crypto_sign_ed25519_pk_to_curve25519(unsigned char *curve25519_pk,
const unsigned char *ed25519_pk)
{
ge_p3 A;
ge_p3 pl;
fe x;
fe one_minus_y;
if (_crypto_sign_ed25519_small_order(ed25519_pk, 1) ||
ge_frombytes_negate_vartime(&A, ed25519_pk) != 0) {
return -1;
}
ge_mul_l(&pl, &A);
if (fe_isnonzero(pl.X)) {
if (ge_has_small_order(ed25519_pk, 1) != 0 ||
ge_frombytes_negate_vartime(&A, ed25519_pk) != 0 ||
ge_is_on_main_subgroup(&A) == 0) {
return -1;
}
fe_1(one_minus_y);
src/libsodium/crypto_sign/ed25519/ref10/open.c
+2 -101
View File
@@ -10,105 +10,6 @@
#include "private/curve25519_ref10.h"
#include "utils.h"
#ifndef ED25519_COMPAT
static int
crypto_sign_check_S_lt_L(const unsigned char *S)
{
/* 2^252+27742317777372353535851937790883648493 */
static const unsigned char L[32] = {
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7,
0xa2, 0xde, 0xf9, 0xde, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
};
unsigned char c = 0;
unsigned char n = 1;
unsigned int i = 32;
do {
i--;
c |= ((S[i] - L[i]) >> 8) & n;
n &= ((S[i] ^ L[i]) - 1) >> 8;
} while (i != 0);
return -(c == 0);
}
int
_crypto_sign_ed25519_small_order(const unsigned char p[32], unsigned char neg)
{
CRYPTO_ALIGN(16)
static const unsigned char blacklist[][32] = {
/* 0 (order 4) */
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
/* 1 (order 1) */
{ 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
/* 2707385501144840649318225287225658788936804267575313519463743609750303402022
(order 8) */
{ 0x26, 0xe8, 0x95, 0x8f, 0xc2, 0xb2, 0x27, 0xb0, 0x45, 0xc3, 0xf4,
0x89, 0xf2, 0xef, 0x98, 0xf0, 0xd5, 0xdf, 0xac, 0x05, 0xd3, 0xc6,
0x33, 0x39, 0xb1, 0x38, 0x02, 0x88, 0x6d, 0x53, 0xfc, 0x05 },
/* 55188659117513257062467267217118295137698188065244968500265048394206261417927
(order 8) */
{ 0xc7, 0x17, 0x6a, 0x70, 0x3d, 0x4d, 0xd8, 0x4f, 0xba, 0x3c, 0x0b,
0x76, 0x0d, 0x10, 0x67, 0x0f, 0x2a, 0x20, 0x53, 0xfa, 0x2c, 0x39,
0xcc, 0xc6, 0x4e, 0xc7, 0xfd, 0x77, 0x92, 0xac, 0x03, 0x7a },
/* p-1 (order 2) */
{ 0x13, 0xe8, 0x95, 0x8f, 0xc2, 0xb2, 0x27, 0xb0, 0x45, 0xc3, 0xf4,
0x89, 0xf2, 0xef, 0x98, 0xf0, 0xd5, 0xdf, 0xac, 0x05, 0xd3, 0xc6,
0x33, 0x39, 0xb1, 0x38, 0x02, 0x88, 0x6d, 0x53, 0xfc, 0x85 },
/* p (order 4) */
{ 0xb4, 0x17, 0x6a, 0x70, 0x3d, 0x4d, 0xd8, 0x4f, 0xba, 0x3c, 0x0b,
0x76, 0x0d, 0x10, 0x67, 0x0f, 0x2a, 0x20, 0x53, 0xfa, 0x2c, 0x39,
0xcc, 0xc6, 0x4e, 0xc7, 0xfd, 0x77, 0x92, 0xac, 0x03, 0xfa },
/* p+1 (order 1) */
{ 0xec, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* p+2707385501144840649318225287225658788936804267575313519463743609750303402022
(order 8) */
{ 0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* p+55188659117513257062467267217118295137698188065244968500265048394206261417927
(order 8) */
{ 0xee, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* 2p-1 (order 2) */
{ 0xd9, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
/* 2p (order 4) */
{ 0xda, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
/* 2p+1 (order 1) */
{ 0xdb, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }
};
size_t i, j;
unsigned char c;
neg <<= 7;
for (i = 0; i < sizeof blacklist / sizeof blacklist[0]; i++) {
c = 0;
for (j = 0; j < 31; j++) {
c |= p[j] ^ blacklist[i][j];
}
c |= p[j] ^ blacklist[i][j] ^ neg;
if (c == 0) {
return 1;
}
}
return 0;
}
#endif
int
_crypto_sign_ed25519_verify_detached(const unsigned char *sig,
const unsigned char *m,
@@ -125,8 +26,8 @@ _crypto_sign_ed25519_verify_detached(const unsigned char *sig,
ge_p2 R;
#ifndef ED25519_COMPAT
if (crypto_sign_check_S_lt_L(sig + 32) != 0 ||
_crypto_sign_ed25519_small_order(sig, 0) != 0) {
if (sc_is_less_than_L(sig + 32) == 0 ||
ge_has_small_order(sig, 0) != 0) {
return -1;
}
#else
src/libsodium/include/sodium/private/curve25519_ref10.h
+6 -2
View File
@@ -104,7 +104,8 @@ typedef struct {
#define ge_scalarmult_base crypto_core_curve25519_ref10_ge_scalarmult_base
#define ge_double_scalarmult_vartime crypto_core_curve25519_ref10_ge_double_scalarmult_vartime
#define ge_scalarmult_vartime crypto_core_curve25519_ref10_ge_scalarmult_vartime
#define ge_mul_l crypto_core_curve25519_ref10_ge_mul_l
#define ge_is_on_main_subgroup crypto_core_curve25519_ref10_ge_is_on_main_subgroup
#define ge_has_small_order crypto_core_curve25519_ref10_ge_has_small_order
extern void ge_tobytes(unsigned char *,const ge_p2 *);
extern void ge_p3_tobytes(unsigned char *,const ge_p3 *);
@@ -118,7 +119,8 @@ extern void ge_scalarmult_base(ge_p3 *,const unsigned char *);
extern void ge_double_scalarmult_vartime(ge_p2 *,const unsigned char *,const ge_p3 *,const unsigned char *);
extern void ge_scalarmult(ge_p3 *,const unsigned char *,const ge_p3 *);
extern void ge_scalarmult_vartime(ge_p3 *,const unsigned char *,const ge_p3 *);
extern void ge_mul_l(ge_p3 *r, const ge_p3 *A);
extern int ge_is_on_main_subgroup(const ge_p3 *p);
extern int ge_has_small_order(const unsigned char s[32], unsigned char neg);
/*
The set of scalars is \Z/l
@@ -127,8 +129,10 @@ extern void ge_mul_l(ge_p3 *r, const ge_p3 *A);
#define sc_reduce crypto_core_curve25519_ref10_sc_reduce
#define sc_muladd crypto_core_curve25519_ref10_sc_muladd
#define sc_is_less_than_L crypto_core_curve25519_ref10_sc_is_less_than_L
extern void sc_reduce(unsigned char *);
extern void sc_muladd(unsigned char *,const unsigned char *,const unsigned char *,const unsigned char *);
extern int sc_is_less_than_L(const unsigned char *s);
#endif