From c9046a05ec0fc3377e1077b401652d76ee5ce908 Mon Sep 17 00:00:00 2001 From: Andy Polyakov Date: Fri, 6 Jul 2018 15:13:15 +0200 Subject: [PATCH] bn/bn_{mont|exp}.c: switch to zero-padded intermediate vectors. Note that exported functions maintain original behaviour, so that external callers won't observe difference. While internally we can now perform Montogomery multiplication on fixed-length vectors, fixed at modulus size. The new functions, bn_to_mont_fixed_top and bn_mul_mont_fixed_top, are declared in bn_int.h, because one can use them even outside bn, e.g. in RSA, DSA, ECDSA... Reviewed-by: Rich Salz (Merged from https://github.com/openssl/openssl/pull/6810) (cherry picked from commit 71883868ea5b33416ae8283bcc38dd2d97e5006b) Resolved conflicts: crypto/bn/bn_exp.c crypto/bn/bn_lcl.h crypto/bn/bn_mont.c crypto/include/internal/bn_int.h --- crypto/Makefile | 2 +- crypto/bn/bn_exp.c | 47 +++++++++++++++++++++++++-------------------- crypto/bn/bn_lcl.h | 1 + crypto/bn/bn_mont.c | 47 +++++++++++++++++++++++++++++++++------------ crypto/bn_int.h | 11 +++++++++++ 5 files changed, 74 insertions(+), 34 deletions(-) create mode 100644 crypto/bn_int.h diff --git a/crypto/Makefile b/crypto/Makefile index 7869996a9c..ad1b9f018b 100644 --- a/crypto/Makefile +++ b/crypto/Makefile @@ -45,7 +45,7 @@ SRC= $(LIBSRC) EXHEADER= crypto.h opensslv.h opensslconf.h ebcdic.h symhacks.h \ ossl_typ.h HEADER= cryptlib.h buildinf.h md32_common.h o_time.h o_str.h o_dir.h \ - constant_time_locl.h $(EXHEADER) + constant_time_locl.h bn_int.h $(EXHEADER) ALL= $(GENERAL) $(SRC) $(HEADER) diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 2eb393d5b2..36b7ba69ad 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -473,17 +473,17 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, ret = 1; goto err; } - if (!BN_to_montgomery(val[0], aa, mont, ctx)) + if (!bn_to_mont_fixed_top(val[0], aa, mont, ctx)) goto err; /* 1 */ window = BN_window_bits_for_exponent_size(bits); if (window > 1) { - if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) + if (!bn_mul_mont_fixed_top(d, val[0], val[0], mont, ctx)) goto err; /* 2 */ j = 1 << (window - 1); for (i = 1; i < j; i++) { if (((val[i] = BN_CTX_get(ctx)) == NULL) || - !BN_mod_mul_montgomery(val[i], val[i - 1], d, mont, ctx)) + !bn_mul_mont_fixed_top(val[i], val[i - 1], d, mont, ctx)) goto err; } } @@ -505,19 +505,15 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, for (i = 1; i < j; i++) r->d[i] = (~m->d[i]) & BN_MASK2; r->top = j; - /* - * Upper words will be zero if the corresponding words of 'm' were - * 0xfff[...], so decrement r->top accordingly. - */ - bn_correct_top(r); + r->flags |= BN_FLG_FIXED_TOP; } else #endif - if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) + if (!bn_to_mont_fixed_top(r, BN_value_one(), mont, ctx)) goto err; for (;;) { if (BN_is_bit_set(p, wstart) == 0) { if (!start) { - if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx)) goto err; } if (wstart == 0) @@ -548,12 +544,12 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, /* add the 'bytes above' */ if (!start) for (i = 0; i < j; i++) { - if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx)) goto err; } /* wvalue will be an odd number < 2^window */ - if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx)) + if (!bn_mul_mont_fixed_top(r, r, val[wvalue >> 1], mont, ctx)) goto err; /* move the 'window' down further */ @@ -563,6 +559,11 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, if (wstart < 0) break; } + /* + * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery + * removes padding [if any] and makes return value suitable for public + * API consumer. + */ #if defined(SPARC_T4_MONT) if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { j = mont->N.top; /* borrow j */ @@ -681,7 +682,7 @@ static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top, } b->top = top; - bn_correct_top(b); + b->flags |= BN_FLG_FIXED_TOP; return 1; } @@ -852,16 +853,16 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, tmp.top = top; } else #endif - if (!BN_to_montgomery(&tmp, BN_value_one(), mont, ctx)) + if (!bn_to_mont_fixed_top(&tmp, BN_value_one(), mont, ctx)) goto err; /* prepare a^1 in Montgomery domain */ if (a->neg || BN_ucmp(a, m) >= 0) { if (!BN_mod(&am, a, m, ctx)) goto err; - if (!BN_to_montgomery(&am, &am, mont, ctx)) + if (!bn_to_mont_fixed_top(&am, &am, mont, ctx)) goto err; - } else if (!BN_to_montgomery(&am, a, mont, ctx)) + } else if (!bn_to_mont_fixed_top(&am, a, mont, ctx)) goto err; #if defined(SPARC_T4_MONT) @@ -1128,14 +1129,14 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, * performance advantage of sqr over mul). */ if (window > 1) { - if (!BN_mod_mul_montgomery(&tmp, &am, &am, mont, ctx)) + if (!bn_mul_mont_fixed_top(&tmp, &am, &am, mont, ctx)) goto err; if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 2, window)) goto err; for (i = 3; i < numPowers; i++) { /* Calculate a^i = a^(i-1) * a */ - if (!BN_mod_mul_montgomery(&tmp, &am, &tmp, mont, ctx)) + if (!bn_mul_mont_fixed_top(&tmp, &am, &tmp, mont, ctx)) goto err; if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i, window)) @@ -1159,7 +1160,7 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, /* Scan the window, squaring the result as we go */ for (i = 0; i < window; i++, bits--) { - if (!BN_mod_mul_montgomery(&tmp, &tmp, &tmp, mont, ctx)) + if (!bn_mul_mont_fixed_top(&tmp, &tmp, &tmp, mont, ctx)) goto err; wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); } @@ -1172,12 +1173,16 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, goto err; /* Multiply the result into the intermediate result */ - if (!BN_mod_mul_montgomery(&tmp, &tmp, &am, mont, ctx)) + if (!bn_mul_mont_fixed_top(&tmp, &tmp, &am, mont, ctx)) goto err; } } - /* Convert the final result from montgomery to standard format */ + /* + * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery + * removes padding [if any] and makes return value suitable for public + * API consumer. + */ #if defined(SPARC_T4_MONT) if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { am.d[0] = 1; /* borrow am */ diff --git a/crypto/bn/bn_lcl.h b/crypto/bn/bn_lcl.h index 00f4f09945..1aa7fe83db 100644 --- a/crypto/bn/bn_lcl.h +++ b/crypto/bn/bn_lcl.h @@ -113,6 +113,7 @@ # define HEADER_BN_LCL_H # include +# include "bn_int.h" #ifdef __cplusplus extern "C" { diff --git a/crypto/bn/bn_mont.c b/crypto/bn/bn_mont.c index cc8f927ee2..d41434a143 100644 --- a/crypto/bn/bn_mont.c +++ b/crypto/bn/bn_mont.c @@ -123,11 +123,22 @@ #define MONT_WORD /* use the faster word-based algorithm */ #ifdef MONT_WORD -static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont); +static int bn_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont); #endif int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_MONT_CTX *mont, BN_CTX *ctx) +{ + int ret = bn_mul_mont_fixed_top(r, a, b, mont, ctx); + + bn_correct_top(r); + bn_check_top(r); + + return ret; +} + +int bn_mul_mont_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, + BN_MONT_CTX *mont, BN_CTX *ctx) { BIGNUM *tmp; int ret = 0; @@ -140,8 +151,8 @@ int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, if (bn_mul_mont(r->d, a->d, b->d, mont->N.d, mont->n0, num)) { r->neg = a->neg ^ b->neg; r->top = num; - bn_correct_top(r); - return (1); + r->flags |= BN_FLG_FIXED_TOP; + return 1; } } #endif @@ -161,13 +172,12 @@ int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, } /* reduce from aRR to aR */ #ifdef MONT_WORD - if (!BN_from_montgomery_word(r, tmp, mont)) + if (!bn_from_montgomery_word(r, tmp, mont)) goto err; #else if (!BN_from_montgomery(r, tmp, mont, ctx)) goto err; #endif - bn_check_top(r); ret = 1; err: BN_CTX_end(ctx); @@ -175,7 +185,7 @@ int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, } #ifdef MONT_WORD -static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont) +static int bn_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont) { BIGNUM *n; BN_ULONG *ap, *np, *rp, n0, v, carry; @@ -205,6 +215,7 @@ static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont) # endif r->top = max; + r->flags |= BN_FLG_FIXED_TOP; n0 = mont->n0[0]; /* @@ -223,6 +234,7 @@ static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont) if (bn_wexpand(ret, nl) == NULL) return (0); ret->top = nl; + ret->flags |= BN_FLG_FIXED_TOP; ret->neg = r->neg; rp = ret->d; @@ -243,9 +255,6 @@ static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont) rp[i] = (carry & ap[i]) | (~carry & rp[i]); ap[i] = 0; } - bn_correct_top(r); - bn_correct_top(ret); - bn_check_top(ret); return (1); } @@ -259,8 +268,11 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, BIGNUM *t; BN_CTX_start(ctx); - if ((t = BN_CTX_get(ctx)) && BN_copy(t, a)) - retn = BN_from_montgomery_word(ret, t, mont); + if ((t = BN_CTX_get(ctx)) && BN_copy(t, a)) { + retn = bn_from_montgomery_word(ret, t, mont); + bn_correct_top(ret); + bn_check_top(ret); + } BN_CTX_end(ctx); #else /* !MONT_WORD */ BIGNUM *t1, *t2; @@ -298,6 +310,12 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, return (retn); } +int bn_to_mont_fixed_top(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont, + BN_CTX *ctx) +{ + return bn_mul_mont_fixed_top(r, a, &(mont->RR), mont, ctx); +} + BN_MONT_CTX *BN_MONT_CTX_new(void) { BN_MONT_CTX *ret; @@ -334,7 +352,7 @@ void BN_MONT_CTX_free(BN_MONT_CTX *mont) int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx) { - int ret = 0; + int i, ret = 0; BIGNUM *Ri, *R; if (BN_is_zero(mod)) @@ -465,6 +483,11 @@ int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx) if (!BN_mod(&(mont->RR), &(mont->RR), &(mont->N), ctx)) goto err; + for (i = mont->RR.top, ret = mont->N.top; i < ret; i++) + mont->RR.d[i] = 0; + mont->RR.top = ret; + mont->RR.flags |= BN_FLG_FIXED_TOP; + ret = 1; err: BN_CTX_end(ctx); diff --git a/crypto/bn_int.h b/crypto/bn_int.h new file mode 100644 index 0000000000..a3b0fa7960 --- /dev/null +++ b/crypto/bn_int.h @@ -0,0 +1,11 @@ +/* + * Some BIGNUM functions assume most significant limb to be non-zero, which + * is customarily arranged by bn_correct_top. Output from below functions + * is not processed with bn_correct_top, and for this reason it may not be + * returned out of public API. It may only be passed internally into other + * functions known to support non-minimal or zero-padded BIGNUMs. + */ +int bn_mul_mont_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, + BN_MONT_CTX *mont, BN_CTX *ctx); +int bn_to_mont_fixed_top(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont, + BN_CTX *ctx); -- 2.25.1