From 09c11fe59b3d45d35e61d95d0f3a5a371f96a19d Mon Sep 17 00:00:00 2001 From: Billy Brumley Date: Sat, 2 Feb 2019 10:53:29 +0200 Subject: [PATCH] SCA hardening for mod. field inversion in EC_GROUP This commit adds a dedicated function in `EC_METHOD` to access a modular field inversion implementation suitable for the specifics of the implemented curve, featuring SCA countermeasures. The new pointer is defined as: `int (*field_inv)(const EC_GROUP*, BIGNUM *r, const BIGNUM *a, BN_CTX*)` and computes the multiplicative inverse of `a` in the underlying field, storing the result in `r`. Three implementations are included, each including specific SCA countermeasures: - `ec_GFp_simple_field_inv()`, featuring SCA hardening through blinding. - `ec_GFp_mont_field_inv()`, featuring SCA hardening through Fermat's Little Theorem (FLT) inversion. - `ec_GF2m_simple_field_inv()`, that uses `BN_GF2m_mod_inv()` which already features SCA hardening through blinding. From a security point of view, this also helps addressing a leakage previously affecting conversions from projective to affine coordinates. This commit also adds a new error reason code (i.e., `EC_R_CANNOT_INVERT`) to improve consistency between the three implementations as all of them could fail for the same reason but through different code paths resulting in inconsistent error stack states. Co-authored-by: Nicola Tuveri (cherry picked from commit e0033efc30b0f00476bba8f0fa5512be5dc8a3f1) Reviewed-by: Matt Caswell Reviewed-by: Nicola Tuveri (Merged from https://github.com/openssl/openssl/pull/8263) --- CHANGES | 6 ++ crypto/ec/ec2_smpl.c | 140 ++++++++++++++++++++++----------------- crypto/ec/ec_err.c | 6 +- crypto/ec/ec_lcl.h | 13 +++- crypto/ec/ecp_mont.c | 51 +++++++++++++- crypto/ec/ecp_nist.c | 3 +- crypto/ec/ecp_nistp224.c | 3 +- crypto/ec/ecp_nistp256.c | 3 +- crypto/ec/ecp_nistp521.c | 3 +- crypto/ec/ecp_nistz256.c | 3 +- crypto/ec/ecp_smpl.c | 51 +++++++++++++- include/openssl/ec.h | 6 +- 12 files changed, 214 insertions(+), 74 deletions(-) diff --git a/CHANGES b/CHANGES index d6342524f7..d0b6fd7f2f 100644 --- a/CHANGES +++ b/CHANGES @@ -9,6 +9,12 @@ Changes between 1.1.0j and 1.1.0k [xx XXX xxxx] + *) Added SCA hardening for modular field inversion in EC_GROUP through + a new dedicated field_inv() pointer in EC_METHOD. + This also addresses a leakage affecting conversions from projective + to affine coordinates. + [Billy Bob Brumley, Nicola Tuveri] + *) Fix a use after free bug in d2i_X509_PUBKEY when overwriting a re-used X509_PUBKEY object if the second PUBKEY is malformed. [Bernd Edlinger] diff --git a/crypto/ec/ec2_smpl.c b/crypto/ec/ec2_smpl.c index cdacce61ac..6cb6d1bbb6 100644 --- a/crypto/ec/ec2_smpl.c +++ b/crypto/ec/ec2_smpl.c @@ -1,5 +1,5 @@ /* - * Copyright 2002-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2002-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -29,67 +29,6 @@ #ifndef OPENSSL_NO_EC2M -const EC_METHOD *EC_GF2m_simple_method(void) -{ - static const EC_METHOD ret = { - EC_FLAGS_DEFAULT_OCT, - NID_X9_62_characteristic_two_field, - ec_GF2m_simple_group_init, - ec_GF2m_simple_group_finish, - ec_GF2m_simple_group_clear_finish, - ec_GF2m_simple_group_copy, - ec_GF2m_simple_group_set_curve, - ec_GF2m_simple_group_get_curve, - ec_GF2m_simple_group_get_degree, - ec_group_simple_order_bits, - ec_GF2m_simple_group_check_discriminant, - ec_GF2m_simple_point_init, - ec_GF2m_simple_point_finish, - ec_GF2m_simple_point_clear_finish, - ec_GF2m_simple_point_copy, - ec_GF2m_simple_point_set_to_infinity, - 0 /* set_Jprojective_coordinates_GFp */ , - 0 /* get_Jprojective_coordinates_GFp */ , - ec_GF2m_simple_point_set_affine_coordinates, - ec_GF2m_simple_point_get_affine_coordinates, - 0, 0, 0, - ec_GF2m_simple_add, - ec_GF2m_simple_dbl, - ec_GF2m_simple_invert, - ec_GF2m_simple_is_at_infinity, - ec_GF2m_simple_is_on_curve, - ec_GF2m_simple_cmp, - ec_GF2m_simple_make_affine, - ec_GF2m_simple_points_make_affine, - - /* - * the following three method functions are defined in ec2_mult.c - */ - ec_GF2m_simple_mul, - ec_GF2m_precompute_mult, - ec_GF2m_have_precompute_mult, - - ec_GF2m_simple_field_mul, - ec_GF2m_simple_field_sqr, - ec_GF2m_simple_field_div, - 0 /* field_encode */ , - 0 /* field_decode */ , - 0, /* field_set_to_one */ - ec_key_simple_priv2oct, - ec_key_simple_oct2priv, - 0, /* set private */ - ec_key_simple_generate_key, - ec_key_simple_check_key, - ec_key_simple_generate_public_key, - 0, /* keycopy */ - 0, /* keyfinish */ - ecdh_simple_compute_key, - 0 /* blind_coordinates */ - }; - - return &ret; -} - /* * Initialize a GF(2^m)-based EC_GROUP structure. Note that all other members * are handled by EC_GROUP_new. @@ -757,4 +696,81 @@ int ec_GF2m_simple_field_div(const EC_GROUP *group, BIGNUM *r, return BN_GF2m_mod_div(r, a, b, group->field, ctx); } +/*- + * Computes the multiplicative inverse of a in GF(2^m), storing the result in r. + * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error. + * SCA hardening is with blinding: BN_GF2m_mod_inv does that. + */ +static int ec_GF2m_simple_field_inv(const EC_GROUP *group, BIGNUM *r, + const BIGNUM *a, BN_CTX *ctx) +{ + int ret; + + if (!(ret = BN_GF2m_mod_inv(r, a, group->field, ctx))) + ECerr(EC_F_EC_GF2M_SIMPLE_FIELD_INV, EC_R_CANNOT_INVERT); + return ret; +} + +const EC_METHOD *EC_GF2m_simple_method(void) +{ + static const EC_METHOD ret = { + EC_FLAGS_DEFAULT_OCT, + NID_X9_62_characteristic_two_field, + ec_GF2m_simple_group_init, + ec_GF2m_simple_group_finish, + ec_GF2m_simple_group_clear_finish, + ec_GF2m_simple_group_copy, + ec_GF2m_simple_group_set_curve, + ec_GF2m_simple_group_get_curve, + ec_GF2m_simple_group_get_degree, + ec_group_simple_order_bits, + ec_GF2m_simple_group_check_discriminant, + ec_GF2m_simple_point_init, + ec_GF2m_simple_point_finish, + ec_GF2m_simple_point_clear_finish, + ec_GF2m_simple_point_copy, + ec_GF2m_simple_point_set_to_infinity, + 0 /* set_Jprojective_coordinates_GFp */ , + 0 /* get_Jprojective_coordinates_GFp */ , + ec_GF2m_simple_point_set_affine_coordinates, + ec_GF2m_simple_point_get_affine_coordinates, + 0, 0, 0, + ec_GF2m_simple_add, + ec_GF2m_simple_dbl, + ec_GF2m_simple_invert, + ec_GF2m_simple_is_at_infinity, + ec_GF2m_simple_is_on_curve, + ec_GF2m_simple_cmp, + ec_GF2m_simple_make_affine, + ec_GF2m_simple_points_make_affine, + + /* + * the following three method functions are defined in ec2_mult.c + */ + ec_GF2m_simple_mul, + ec_GF2m_precompute_mult, + ec_GF2m_have_precompute_mult, + + ec_GF2m_simple_field_mul, + ec_GF2m_simple_field_sqr, + ec_GF2m_simple_field_div, + ec_GF2m_simple_field_inv, + 0 /* field_encode */ , + 0 /* field_decode */ , + 0, /* field_set_to_one */ + ec_key_simple_priv2oct, + ec_key_simple_oct2priv, + 0, /* set private */ + ec_key_simple_generate_key, + ec_key_simple_check_key, + ec_key_simple_generate_public_key, + 0, /* keycopy */ + 0, /* keyfinish */ + ecdh_simple_compute_key, + 0 /* blind_coordinates */ + }; + + return &ret; +} + #endif diff --git a/crypto/ec/ec_err.c b/crypto/ec/ec_err.c index 717c92e984..aeee2e8f4c 100644 --- a/crypto/ec/ec_err.c +++ b/crypto/ec/ec_err.c @@ -1,6 +1,6 @@ /* * Generated by util/mkerr.pl DO NOT EDIT - * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -58,6 +58,7 @@ static ERR_STRING_DATA EC_str_functs[] = { {ERR_FUNC(EC_F_EC_ASN1_GROUP2FIELDID), "ec_asn1_group2fieldid"}, {ERR_FUNC(EC_F_EC_GF2M_MONTGOMERY_POINT_MULTIPLY), "ec_GF2m_montgomery_point_multiply"}, + {ERR_FUNC(EC_F_EC_GF2M_SIMPLE_FIELD_INV), "ec_GF2m_simple_field_inv"}, {ERR_FUNC(EC_F_EC_GF2M_SIMPLE_GROUP_CHECK_DISCRIMINANT), "ec_GF2m_simple_group_check_discriminant"}, {ERR_FUNC(EC_F_EC_GF2M_SIMPLE_GROUP_SET_CURVE), @@ -72,6 +73,7 @@ static ERR_STRING_DATA EC_str_functs[] = { "ec_GF2m_simple_set_compressed_coordinates"}, {ERR_FUNC(EC_F_EC_GFP_MONT_FIELD_DECODE), "ec_GFp_mont_field_decode"}, {ERR_FUNC(EC_F_EC_GFP_MONT_FIELD_ENCODE), "ec_GFp_mont_field_encode"}, + {ERR_FUNC(EC_F_EC_GFP_MONT_FIELD_INV), "ec_GFp_mont_field_inv"}, {ERR_FUNC(EC_F_EC_GFP_MONT_FIELD_MUL), "ec_GFp_mont_field_mul"}, {ERR_FUNC(EC_F_EC_GFP_MONT_FIELD_SET_TO_ONE), "ec_GFp_mont_field_set_to_one"}, @@ -99,6 +101,7 @@ static ERR_STRING_DATA EC_str_functs[] = { "ec_GFp_nist_group_set_curve"}, {ERR_FUNC(EC_F_EC_GFP_SIMPLE_BLIND_COORDINATES), "ec_GFp_simple_blind_coordinates"}, + {ERR_FUNC(EC_F_EC_GFP_SIMPLE_FIELD_INV), "ec_GFp_simple_field_inv"}, {ERR_FUNC(EC_F_EC_GFP_SIMPLE_GROUP_CHECK_DISCRIMINANT), "ec_GFp_simple_group_check_discriminant"}, {ERR_FUNC(EC_F_EC_GFP_SIMPLE_GROUP_SET_CURVE), @@ -211,6 +214,7 @@ static ERR_STRING_DATA EC_str_reasons[] = { {ERR_REASON(EC_R_BAD_SIGNATURE), "bad signature"}, {ERR_REASON(EC_R_BIGNUM_OUT_OF_RANGE), "bignum out of range"}, {ERR_REASON(EC_R_BUFFER_TOO_SMALL), "buffer too small"}, + {ERR_REASON(EC_R_CANNOT_INVERT), "cannot invert"}, {ERR_REASON(EC_R_COORDINATES_OUT_OF_RANGE), "coordinates out of range"}, {ERR_REASON(EC_R_CURVE_DOES_NOT_SUPPORT_ECDH), "curve does not support ecdh"}, diff --git a/crypto/ec/ec_lcl.h b/crypto/ec/ec_lcl.h index ca1776efdb..2e85597f6b 100644 --- a/crypto/ec/ec_lcl.h +++ b/crypto/ec/ec_lcl.h @@ -1,5 +1,5 @@ /* - * Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -150,6 +150,13 @@ struct ec_method_st { int (*field_sqr) (const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *); int (*field_div) (const EC_GROUP *, BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *); + /*- + * 'field_inv' computes the multipicative inverse of a in the field, + * storing the result in r. + * + * If 'a' is zero (or equivalent), you'll get an EC_R_CANNOT_INVERT error. + */ + int (*field_inv) (const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *); /* e.g. to Montgomery */ int (*field_encode) (const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *); @@ -376,6 +383,8 @@ int ec_GFp_simple_field_mul(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *); int ec_GFp_simple_field_sqr(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *); +int ec_GFp_simple_field_inv(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, + BN_CTX *); int ec_GFp_simple_blind_coordinates(const EC_GROUP *group, EC_POINT *p, BN_CTX *ctx); @@ -390,6 +399,8 @@ int ec_GFp_mont_field_mul(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *); int ec_GFp_mont_field_sqr(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *); +int ec_GFp_mont_field_inv(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, + BN_CTX *); int ec_GFp_mont_field_encode(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *); int ec_GFp_mont_field_decode(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, diff --git a/crypto/ec/ecp_mont.c b/crypto/ec/ecp_mont.c index d837d4d465..8ecd53ad55 100644 --- a/crypto/ec/ecp_mont.c +++ b/crypto/ec/ecp_mont.c @@ -1,5 +1,5 @@ /* - * Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -55,6 +55,7 @@ const EC_METHOD *EC_GFp_mont_method(void) ec_GFp_mont_field_mul, ec_GFp_mont_field_sqr, 0 /* field_div */ , + ec_GFp_mont_field_inv, ec_GFp_mont_field_encode, ec_GFp_mont_field_decode, ec_GFp_mont_field_set_to_one, @@ -207,6 +208,54 @@ int ec_GFp_mont_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, return BN_mod_mul_montgomery(r, a, a, group->field_data1, ctx); } +/*- + * Computes the multiplicative inverse of a in GF(p), storing the result in r. + * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error. + * We have a Mont structure, so SCA hardening is FLT inversion. + */ +int ec_GFp_mont_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, + BN_CTX *ctx) +{ + BIGNUM *e = NULL; + BN_CTX *new_ctx = NULL; + int ret = 0; + + if (group->field_data1 == NULL) + return 0; + + if (ctx == NULL && (ctx = new_ctx = BN_CTX_secure_new()) == NULL) + return 0; + + BN_CTX_start(ctx); + if ((e = BN_CTX_get(ctx)) == NULL) + goto err; + + /* Inverse in constant time with Fermats Little Theorem */ + if (!BN_set_word(e, 2)) + goto err; + if (!BN_sub(e, group->field, e)) + goto err; + /*- + * Exponent e is public. + * No need for scatter-gather or BN_FLG_CONSTTIME. + */ + if (!BN_mod_exp_mont(r, a, e, group->field, ctx, group->field_data1)) + goto err; + + /* throw an error on zero */ + if (BN_is_zero(r)) { + ECerr(EC_F_EC_GFP_MONT_FIELD_INV, EC_R_CANNOT_INVERT); + goto err; + } + + ret = 1; + + err: + BN_CTX_end(ctx); + BN_CTX_free(new_ctx); + return ret; +} + int ec_GFp_mont_field_encode(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, BN_CTX *ctx) { diff --git a/crypto/ec/ecp_nist.c b/crypto/ec/ecp_nist.c index 143f21f3f9..c874380203 100644 --- a/crypto/ec/ecp_nist.c +++ b/crypto/ec/ecp_nist.c @@ -1,5 +1,5 @@ /* - * Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -57,6 +57,7 @@ const EC_METHOD *EC_GFp_nist_method(void) ec_GFp_nist_field_mul, ec_GFp_nist_field_sqr, 0 /* field_div */ , + ec_GFp_simple_field_inv, 0 /* field_encode */ , 0 /* field_decode */ , 0, /* field_set_to_one */ diff --git a/crypto/ec/ecp_nistp224.c b/crypto/ec/ecp_nistp224.c index 52056ff591..651dcb10a0 100644 --- a/crypto/ec/ecp_nistp224.c +++ b/crypto/ec/ecp_nistp224.c @@ -1,5 +1,5 @@ /* - * Copyright 2010-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2010-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -279,6 +279,7 @@ const EC_METHOD *EC_GFp_nistp224_method(void) ec_GFp_nist_field_mul, ec_GFp_nist_field_sqr, 0 /* field_div */ , + ec_GFp_simple_field_inv, 0 /* field_encode */ , 0 /* field_decode */ , 0, /* field_set_to_one */ diff --git a/crypto/ec/ecp_nistp256.c b/crypto/ec/ecp_nistp256.c index ffd2a7d93a..dfd98c62fe 100644 --- a/crypto/ec/ecp_nistp256.c +++ b/crypto/ec/ecp_nistp256.c @@ -1,5 +1,5 @@ /* - * Copyright 2011-2016 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2011-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -1810,6 +1810,7 @@ const EC_METHOD *EC_GFp_nistp256_method(void) ec_GFp_nist_field_mul, ec_GFp_nist_field_sqr, 0 /* field_div */ , + ec_GFp_simple_field_inv, 0 /* field_encode */ , 0 /* field_decode */ , 0, /* field_set_to_one */ diff --git a/crypto/ec/ecp_nistp521.c b/crypto/ec/ecp_nistp521.c index 0a82abca1b..ddfef91bda 100644 --- a/crypto/ec/ecp_nistp521.c +++ b/crypto/ec/ecp_nistp521.c @@ -1,5 +1,5 @@ /* - * Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2011-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -1631,6 +1631,7 @@ const EC_METHOD *EC_GFp_nistp521_method(void) ec_GFp_nist_field_mul, ec_GFp_nist_field_sqr, 0 /* field_div */ , + ec_GFp_simple_field_inv, 0 /* field_encode */ , 0 /* field_decode */ , 0, /* field_set_to_one */ diff --git a/crypto/ec/ecp_nistz256.c b/crypto/ec/ecp_nistz256.c index 7eafce649b..e1170b4d39 100644 --- a/crypto/ec/ecp_nistz256.c +++ b/crypto/ec/ecp_nistz256.c @@ -1,5 +1,5 @@ /* - * Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2014-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -1525,6 +1525,7 @@ const EC_METHOD *EC_GFp_nistz256_method(void) ec_GFp_mont_field_mul, ec_GFp_mont_field_sqr, 0, /* field_div */ + ec_GFp_mont_field_inv, ec_GFp_mont_field_encode, ec_GFp_mont_field_decode, ec_GFp_mont_field_set_to_one, diff --git a/crypto/ec/ecp_smpl.c b/crypto/ec/ecp_smpl.c index 2015f1173b..d8db1ea394 100644 --- a/crypto/ec/ecp_smpl.c +++ b/crypto/ec/ecp_smpl.c @@ -1,5 +1,5 @@ /* - * Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -56,6 +56,7 @@ const EC_METHOD *EC_GFp_simple_method(void) ec_GFp_simple_field_mul, ec_GFp_simple_field_sqr, 0 /* field_div */ , + ec_GFp_simple_field_inv, 0 /* field_encode */ , 0 /* field_decode */ , 0, /* field_set_to_one */ @@ -554,7 +555,7 @@ int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group, } } } else { - if (!BN_mod_inverse(Z_1, Z_, group->field, ctx)) { + if (!group->meth->field_inv(group, Z_1, Z_, ctx)) { ECerr(EC_F_EC_GFP_SIMPLE_POINT_GET_AFFINE_COORDINATES, ERR_R_BN_LIB); goto err; @@ -1267,7 +1268,7 @@ int ec_GFp_simple_points_make_affine(const EC_GROUP *group, size_t num, * points[i]->Z by its inverse. */ - if (!BN_mod_inverse(tmp, prod_Z[num - 1], group->field, ctx)) { + if (!group->meth->field_inv(group, tmp, prod_Z[num - 1], ctx)) { ECerr(EC_F_EC_GFP_SIMPLE_POINTS_MAKE_AFFINE, ERR_R_BN_LIB); goto err; } @@ -1370,6 +1371,50 @@ int ec_GFp_simple_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, return BN_mod_sqr(r, a, group->field, ctx); } +/*- + * Computes the multiplicative inverse of a in GF(p), storing the result in r. + * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error. + * Since we don't have a Mont structure here, SCA hardening is with blinding. + */ +int ec_GFp_simple_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, + BN_CTX *ctx) +{ + BIGNUM *e = NULL; + BN_CTX *new_ctx = NULL; + int ret = 0; + + if (ctx == NULL && (ctx = new_ctx = BN_CTX_secure_new()) == NULL) + return 0; + + BN_CTX_start(ctx); + if ((e = BN_CTX_get(ctx)) == NULL) + goto err; + + do { + if (!BN_rand_range(e, group->field)) + goto err; + } while (BN_is_zero(e)); + + /* r := a * e */ + if (!group->meth->field_mul(group, r, a, e, ctx)) + goto err; + /* r := 1/(a * e) */ + if (!BN_mod_inverse(r, r, group->field, ctx)) { + ECerr(EC_F_EC_GFP_SIMPLE_FIELD_INV, EC_R_CANNOT_INVERT); + goto err; + } + /* r := e/(a * e) = 1/a */ + if (!group->meth->field_mul(group, r, r, e, ctx)) + goto err; + + ret = 1; + + err: + BN_CTX_end(ctx); + BN_CTX_free(new_ctx); + return ret; +} + /*- * Apply randomization of EC point projective coordinates: * diff --git a/include/openssl/ec.h b/include/openssl/ec.h index d6b36c77c0..bea6b8c372 100644 --- a/include/openssl/ec.h +++ b/include/openssl/ec.h @@ -1,5 +1,5 @@ /* - * Copyright 2002-2018 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 2002-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -1399,6 +1399,7 @@ int ERR_load_EC_strings(void); # define EC_F_EC_ASN1_GROUP2CURVE 153 # define EC_F_EC_ASN1_GROUP2FIELDID 154 # define EC_F_EC_GF2M_MONTGOMERY_POINT_MULTIPLY 208 +# define EC_F_EC_GF2M_SIMPLE_FIELD_INV 296 # define EC_F_EC_GF2M_SIMPLE_GROUP_CHECK_DISCRIMINANT 159 # define EC_F_EC_GF2M_SIMPLE_GROUP_SET_CURVE 195 # define EC_F_EC_GF2M_SIMPLE_OCT2POINT 160 @@ -1408,6 +1409,7 @@ int ERR_load_EC_strings(void); # define EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES 164 # define EC_F_EC_GFP_MONT_FIELD_DECODE 133 # define EC_F_EC_GFP_MONT_FIELD_ENCODE 134 +# define EC_F_EC_GFP_MONT_FIELD_INV 297 # define EC_F_EC_GFP_MONT_FIELD_MUL 131 # define EC_F_EC_GFP_MONT_FIELD_SET_TO_ONE 209 # define EC_F_EC_GFP_MONT_FIELD_SQR 132 @@ -1425,6 +1427,7 @@ int ERR_load_EC_strings(void); # define EC_F_EC_GFP_NIST_FIELD_SQR 201 # define EC_F_EC_GFP_NIST_GROUP_SET_CURVE 202 # define EC_F_EC_GFP_SIMPLE_BLIND_COORDINATES 287 +# define EC_F_EC_GFP_SIMPLE_FIELD_INV 298 # define EC_F_EC_GFP_SIMPLE_GROUP_CHECK_DISCRIMINANT 165 # define EC_F_EC_GFP_SIMPLE_GROUP_SET_CURVE 166 # define EC_F_EC_GFP_SIMPLE_MAKE_AFFINE 102 @@ -1514,6 +1517,7 @@ int ERR_load_EC_strings(void); # define EC_R_BAD_SIGNATURE 156 # define EC_R_BIGNUM_OUT_OF_RANGE 144 # define EC_R_BUFFER_TOO_SMALL 100 +# define EC_R_CANNOT_INVERT 165 # define EC_R_COORDINATES_OUT_OF_RANGE 146 # define EC_R_CURVE_DOES_NOT_SUPPORT_ECDH 160 # define EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING 159 -- 2.25.1