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Diffstat (limited to 'openssl-1.1.0h/crypto/bn/bn_exp.c')
-rw-r--r--openssl-1.1.0h/crypto/bn/bn_exp.c1376
1 files changed, 1376 insertions, 0 deletions
diff --git a/openssl-1.1.0h/crypto/bn/bn_exp.c b/openssl-1.1.0h/crypto/bn/bn_exp.c
new file mode 100644
index 0000000..0d2d1ec
--- /dev/null
+++ b/openssl-1.1.0h/crypto/bn/bn_exp.c
@@ -0,0 +1,1376 @@
+/*
+ * Copyright 1995-2018 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
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include "internal/cryptlib.h"
+#include "internal/constant_time_locl.h"
+#include "bn_lcl.h"
+
+#include <stdlib.h>
+#ifdef _WIN32
+# include <malloc.h>
+# ifndef alloca
+# define alloca _alloca
+# endif
+#elif defined(__GNUC__)
+# ifndef alloca
+# define alloca(s) __builtin_alloca((s))
+# endif
+#elif defined(__sun)
+# include <alloca.h>
+#endif
+
+#include "rsaz_exp.h"
+
+#undef SPARC_T4_MONT
+#if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc))
+# include "sparc_arch.h"
+extern unsigned int OPENSSL_sparcv9cap_P[];
+# define SPARC_T4_MONT
+#endif
+
+/* maximum precomputation table size for *variable* sliding windows */
+#define TABLE_SIZE 32
+
+/* this one works - simple but works */
+int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
+{
+ int i, bits, ret = 0;
+ BIGNUM *v, *rr;
+
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) {
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return 0;
+ }
+
+ BN_CTX_start(ctx);
+ if ((r == a) || (r == p))
+ rr = BN_CTX_get(ctx);
+ else
+ rr = r;
+ v = BN_CTX_get(ctx);
+ if (rr == NULL || v == NULL)
+ goto err;
+
+ if (BN_copy(v, a) == NULL)
+ goto err;
+ bits = BN_num_bits(p);
+
+ if (BN_is_odd(p)) {
+ if (BN_copy(rr, a) == NULL)
+ goto err;
+ } else {
+ if (!BN_one(rr))
+ goto err;
+ }
+
+ for (i = 1; i < bits; i++) {
+ if (!BN_sqr(v, v, ctx))
+ goto err;
+ if (BN_is_bit_set(p, i)) {
+ if (!BN_mul(rr, rr, v, ctx))
+ goto err;
+ }
+ }
+ if (r != rr && BN_copy(r, rr) == NULL)
+ goto err;
+
+ ret = 1;
+ err:
+ BN_CTX_end(ctx);
+ bn_check_top(r);
+ return (ret);
+}
+
+int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
+ BN_CTX *ctx)
+{
+ int ret;
+
+ bn_check_top(a);
+ bn_check_top(p);
+ bn_check_top(m);
+
+ /*-
+ * For even modulus m = 2^k*m_odd, it might make sense to compute
+ * a^p mod m_odd and a^p mod 2^k separately (with Montgomery
+ * exponentiation for the odd part), using appropriate exponent
+ * reductions, and combine the results using the CRT.
+ *
+ * For now, we use Montgomery only if the modulus is odd; otherwise,
+ * exponentiation using the reciprocal-based quick remaindering
+ * algorithm is used.
+ *
+ * (Timing obtained with expspeed.c [computations a^p mod m
+ * where a, p, m are of the same length: 256, 512, 1024, 2048,
+ * 4096, 8192 bits], compared to the running time of the
+ * standard algorithm:
+ *
+ * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration]
+ * 55 .. 77 % [UltraSparc processor, but
+ * debug-solaris-sparcv8-gcc conf.]
+ *
+ * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration]
+ * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc]
+ *
+ * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont
+ * at 2048 and more bits, but at 512 and 1024 bits, it was
+ * slower even than the standard algorithm!
+ *
+ * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations]
+ * should be obtained when the new Montgomery reduction code
+ * has been integrated into OpenSSL.)
+ */
+
+#define MONT_MUL_MOD
+#define MONT_EXP_WORD
+#define RECP_MUL_MOD
+
+#ifdef MONT_MUL_MOD
+ /*
+ * I have finally been able to take out this pre-condition of the top bit
+ * being set. It was caused by an error in BN_div with negatives. There
+ * was also another problem when for a^b%m a >= m. eay 07-May-97
+ */
+ /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */
+
+ if (BN_is_odd(m)) {
+# ifdef MONT_EXP_WORD
+ if (a->top == 1 && !a->neg
+ && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)
+ && (BN_get_flags(a, BN_FLG_CONSTTIME) == 0)
+ && (BN_get_flags(m, BN_FLG_CONSTTIME) == 0)) {
+ BN_ULONG A = a->d[0];
+ ret = BN_mod_exp_mont_word(r, A, p, m, ctx, NULL);
+ } else
+# endif
+ ret = BN_mod_exp_mont(r, a, p, m, ctx, NULL);
+ } else
+#endif
+#ifdef RECP_MUL_MOD
+ {
+ ret = BN_mod_exp_recp(r, a, p, m, ctx);
+ }
+#else
+ {
+ ret = BN_mod_exp_simple(r, a, p, m, ctx);
+ }
+#endif
+
+ bn_check_top(r);
+ return (ret);
+}
+
+int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+ const BIGNUM *m, BN_CTX *ctx)
+{
+ int i, j, bits, ret = 0, wstart, wend, window, wvalue;
+ int start = 1;
+ BIGNUM *aa;
+ /* Table of variables obtained from 'ctx' */
+ BIGNUM *val[TABLE_SIZE];
+ BN_RECP_CTX recp;
+
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_MOD_EXP_RECP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return 0;
+ }
+
+ bits = BN_num_bits(p);
+ if (bits == 0) {
+ /* x**0 mod 1 is still zero. */
+ if (BN_is_one(m)) {
+ ret = 1;
+ BN_zero(r);
+ } else {
+ ret = BN_one(r);
+ }
+ return ret;
+ }
+
+ BN_CTX_start(ctx);
+ aa = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if (!aa || !val[0])
+ goto err;
+
+ BN_RECP_CTX_init(&recp);
+ if (m->neg) {
+ /* ignore sign of 'm' */
+ if (!BN_copy(aa, m))
+ goto err;
+ aa->neg = 0;
+ if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0)
+ goto err;
+ } else {
+ if (BN_RECP_CTX_set(&recp, m, ctx) <= 0)
+ goto err;
+ }
+
+ if (!BN_nnmod(val[0], a, m, ctx))
+ goto err; /* 1 */
+ if (BN_is_zero(val[0])) {
+ BN_zero(r);
+ ret = 1;
+ goto err;
+ }
+
+ window = BN_window_bits_for_exponent_size(bits);
+ if (window > 1) {
+ if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, 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_reciprocal(val[i], val[i - 1], aa, &recp, ctx))
+ goto err;
+ }
+ }
+
+ start = 1; /* This is used to avoid multiplication etc
+ * when there is only the value '1' in the
+ * buffer. */
+ wvalue = 0; /* The 'value' of the window */
+ wstart = bits - 1; /* The top bit of the window */
+ wend = 0; /* The bottom bit of the window */
+
+ if (!BN_one(r))
+ goto err;
+
+ for (;;) {
+ if (BN_is_bit_set(p, wstart) == 0) {
+ if (!start)
+ if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))
+ goto err;
+ if (wstart == 0)
+ break;
+ wstart--;
+ continue;
+ }
+ /*
+ * We now have wstart on a 'set' bit, we now need to work out how bit
+ * a window to do. To do this we need to scan forward until the last
+ * set bit before the end of the window
+ */
+ j = wstart;
+ wvalue = 1;
+ wend = 0;
+ for (i = 1; i < window; i++) {
+ if (wstart - i < 0)
+ break;
+ if (BN_is_bit_set(p, wstart - i)) {
+ wvalue <<= (i - wend);
+ wvalue |= 1;
+ wend = i;
+ }
+ }
+
+ /* wend is the size of the current window */
+ j = wend + 1;
+ /* add the 'bytes above' */
+ if (!start)
+ for (i = 0; i < j; i++) {
+ if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))
+ goto err;
+ }
+
+ /* wvalue will be an odd number < 2^window */
+ if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx))
+ goto err;
+
+ /* move the 'window' down further */
+ wstart -= wend + 1;
+ wvalue = 0;
+ start = 0;
+ if (wstart < 0)
+ break;
+ }
+ ret = 1;
+ err:
+ BN_CTX_end(ctx);
+ BN_RECP_CTX_free(&recp);
+ bn_check_top(r);
+ return (ret);
+}
+
+int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
+ const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
+{
+ int i, j, bits, ret = 0, wstart, wend, window, wvalue;
+ int start = 1;
+ BIGNUM *d, *r;
+ const BIGNUM *aa;
+ /* Table of variables obtained from 'ctx' */
+ BIGNUM *val[TABLE_SIZE];
+ BN_MONT_CTX *mont = NULL;
+
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
+ return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont);
+ }
+
+ bn_check_top(a);
+ bn_check_top(p);
+ bn_check_top(m);
+
+ if (!BN_is_odd(m)) {
+ BNerr(BN_F_BN_MOD_EXP_MONT, BN_R_CALLED_WITH_EVEN_MODULUS);
+ return (0);
+ }
+ bits = BN_num_bits(p);
+ if (bits == 0) {
+ /* x**0 mod 1 is still zero. */
+ if (BN_is_one(m)) {
+ ret = 1;
+ BN_zero(rr);
+ } else {
+ ret = BN_one(rr);
+ }
+ return ret;
+ }
+
+ BN_CTX_start(ctx);
+ d = BN_CTX_get(ctx);
+ r = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if (!d || !r || !val[0])
+ goto err;
+
+ /*
+ * If this is not done, things will break in the montgomery part
+ */
+
+ if (in_mont != NULL)
+ mont = in_mont;
+ else {
+ if ((mont = BN_MONT_CTX_new()) == NULL)
+ goto err;
+ if (!BN_MONT_CTX_set(mont, m, ctx))
+ goto err;
+ }
+
+ if (a->neg || BN_ucmp(a, m) >= 0) {
+ if (!BN_nnmod(val[0], a, m, ctx))
+ goto err;
+ aa = val[0];
+ } else
+ aa = a;
+ if (BN_is_zero(aa)) {
+ BN_zero(rr);
+ ret = 1;
+ goto err;
+ }
+ if (!BN_to_montgomery(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))
+ 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))
+ goto err;
+ }
+ }
+
+ start = 1; /* This is used to avoid multiplication etc
+ * when there is only the value '1' in the
+ * buffer. */
+ wvalue = 0; /* The 'value' of the window */
+ wstart = bits - 1; /* The top bit of the window */
+ wend = 0; /* The bottom bit of the window */
+
+#if 1 /* by Shay Gueron's suggestion */
+ j = m->top; /* borrow j */
+ if (m->d[j - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) {
+ if (bn_wexpand(r, j) == NULL)
+ goto err;
+ /* 2^(top*BN_BITS2) - m */
+ r->d[0] = (0 - m->d[0]) & BN_MASK2;
+ 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);
+ } else
+#endif
+ if (!BN_to_montgomery(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))
+ goto err;
+ }
+ if (wstart == 0)
+ break;
+ wstart--;
+ continue;
+ }
+ /*
+ * We now have wstart on a 'set' bit, we now need to work out how bit
+ * a window to do. To do this we need to scan forward until the last
+ * set bit before the end of the window
+ */
+ j = wstart;
+ wvalue = 1;
+ wend = 0;
+ for (i = 1; i < window; i++) {
+ if (wstart - i < 0)
+ break;
+ if (BN_is_bit_set(p, wstart - i)) {
+ wvalue <<= (i - wend);
+ wvalue |= 1;
+ wend = i;
+ }
+ }
+
+ /* wend is the size of the current window */
+ j = wend + 1;
+ /* add the 'bytes above' */
+ if (!start)
+ for (i = 0; i < j; i++) {
+ if (!BN_mod_mul_montgomery(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))
+ goto err;
+
+ /* move the 'window' down further */
+ wstart -= wend + 1;
+ wvalue = 0;
+ start = 0;
+ if (wstart < 0)
+ break;
+ }
+#if defined(SPARC_T4_MONT)
+ if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) {
+ j = mont->N.top; /* borrow j */
+ val[0]->d[0] = 1; /* borrow val[0] */
+ for (i = 1; i < j; i++)
+ val[0]->d[i] = 0;
+ val[0]->top = j;
+ if (!BN_mod_mul_montgomery(rr, r, val[0], mont, ctx))
+ goto err;
+ } else
+#endif
+ if (!BN_from_montgomery(rr, r, mont, ctx))
+ goto err;
+ ret = 1;
+ err:
+ if (in_mont == NULL)
+ BN_MONT_CTX_free(mont);
+ BN_CTX_end(ctx);
+ bn_check_top(rr);
+ return (ret);
+}
+
+#if defined(SPARC_T4_MONT)
+static BN_ULONG bn_get_bits(const BIGNUM *a, int bitpos)
+{
+ BN_ULONG ret = 0;
+ int wordpos;
+
+ wordpos = bitpos / BN_BITS2;
+ bitpos %= BN_BITS2;
+ if (wordpos >= 0 && wordpos < a->top) {
+ ret = a->d[wordpos] & BN_MASK2;
+ if (bitpos) {
+ ret >>= bitpos;
+ if (++wordpos < a->top)
+ ret |= a->d[wordpos] << (BN_BITS2 - bitpos);
+ }
+ }
+
+ return ret & BN_MASK2;
+}
+#endif
+
+/*
+ * BN_mod_exp_mont_consttime() stores the precomputed powers in a specific
+ * layout so that accessing any of these table values shows the same access
+ * pattern as far as cache lines are concerned. The following functions are
+ * used to transfer a BIGNUM from/to that table.
+ */
+
+static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top,
+ unsigned char *buf, int idx,
+ int window)
+{
+ int i, j;
+ int width = 1 << window;
+ BN_ULONG *table = (BN_ULONG *)buf;
+
+ if (top > b->top)
+ top = b->top; /* this works because 'buf' is explicitly
+ * zeroed */
+ for (i = 0, j = idx; i < top; i++, j += width) {
+ table[j] = b->d[i];
+ }
+
+ return 1;
+}
+
+static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top,
+ unsigned char *buf, int idx,
+ int window)
+{
+ int i, j;
+ int width = 1 << window;
+ /*
+ * We declare table 'volatile' in order to discourage compiler
+ * from reordering loads from the table. Concern is that if
+ * reordered in specific manner loads might give away the
+ * information we are trying to conceal. Some would argue that
+ * compiler can reorder them anyway, but it can as well be
+ * argued that doing so would be violation of standard...
+ */
+ volatile BN_ULONG *table = (volatile BN_ULONG *)buf;
+
+ if (bn_wexpand(b, top) == NULL)
+ return 0;
+
+ if (window <= 3) {
+ for (i = 0; i < top; i++, table += width) {
+ BN_ULONG acc = 0;
+
+ for (j = 0; j < width; j++) {
+ acc |= table[j] &
+ ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1));
+ }
+
+ b->d[i] = acc;
+ }
+ } else {
+ int xstride = 1 << (window - 2);
+ BN_ULONG y0, y1, y2, y3;
+
+ i = idx >> (window - 2); /* equivalent of idx / xstride */
+ idx &= xstride - 1; /* equivalent of idx % xstride */
+
+ y0 = (BN_ULONG)0 - (constant_time_eq_int(i,0)&1);
+ y1 = (BN_ULONG)0 - (constant_time_eq_int(i,1)&1);
+ y2 = (BN_ULONG)0 - (constant_time_eq_int(i,2)&1);
+ y3 = (BN_ULONG)0 - (constant_time_eq_int(i,3)&1);
+
+ for (i = 0; i < top; i++, table += width) {
+ BN_ULONG acc = 0;
+
+ for (j = 0; j < xstride; j++) {
+ acc |= ( (table[j + 0 * xstride] & y0) |
+ (table[j + 1 * xstride] & y1) |
+ (table[j + 2 * xstride] & y2) |
+ (table[j + 3 * xstride] & y3) )
+ & ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1));
+ }
+
+ b->d[i] = acc;
+ }
+ }
+
+ b->top = top;
+ bn_correct_top(b);
+ return 1;
+}
+
+/*
+ * Given a pointer value, compute the next address that is a cache line
+ * multiple.
+ */
+#define MOD_EXP_CTIME_ALIGN(x_) \
+ ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK))))
+
+/*
+ * This variant of BN_mod_exp_mont() uses fixed windows and the special
+ * precomputation memory layout to limit data-dependency to a minimum to
+ * protect secret exponents (cf. the hyper-threading timing attacks pointed
+ * out by Colin Percival,
+ * http://www.daemonology.net/hyperthreading-considered-harmful/)
+ */
+int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
+ const BIGNUM *m, BN_CTX *ctx,
+ BN_MONT_CTX *in_mont)
+{
+ int i, bits, ret = 0, window, wvalue;
+ int top;
+ BN_MONT_CTX *mont = NULL;
+
+ int numPowers;
+ unsigned char *powerbufFree = NULL;
+ int powerbufLen = 0;
+ unsigned char *powerbuf = NULL;
+ BIGNUM tmp, am;
+#if defined(SPARC_T4_MONT)
+ unsigned int t4 = 0;
+#endif
+
+ bn_check_top(a);
+ bn_check_top(p);
+ bn_check_top(m);
+
+ if (!BN_is_odd(m)) {
+ BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME, BN_R_CALLED_WITH_EVEN_MODULUS);
+ return (0);
+ }
+
+ top = m->top;
+
+ /*
+ * Use all bits stored in |p|, rather than |BN_num_bits|, so we do not leak
+ * whether the top bits are zero.
+ */
+ bits = p->top * BN_BITS2;
+ if (bits == 0) {
+ /* x**0 mod 1 is still zero. */
+ if (BN_is_one(m)) {
+ ret = 1;
+ BN_zero(rr);
+ } else {
+ ret = BN_one(rr);
+ }
+ return ret;
+ }
+
+ BN_CTX_start(ctx);
+
+ /*
+ * Allocate a montgomery context if it was not supplied by the caller. If
+ * this is not done, things will break in the montgomery part.
+ */
+ if (in_mont != NULL)
+ mont = in_mont;
+ else {
+ if ((mont = BN_MONT_CTX_new()) == NULL)
+ goto err;
+ if (!BN_MONT_CTX_set(mont, m, ctx))
+ goto err;
+ }
+
+#ifdef RSAZ_ENABLED
+ /*
+ * If the size of the operands allow it, perform the optimized
+ * RSAZ exponentiation. For further information see
+ * crypto/bn/rsaz_exp.c and accompanying assembly modules.
+ */
+ if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024)
+ && rsaz_avx2_eligible()) {
+ if (NULL == bn_wexpand(rr, 16))
+ goto err;
+ RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d,
+ mont->n0[0]);
+ rr->top = 16;
+ rr->neg = 0;
+ bn_correct_top(rr);
+ ret = 1;
+ goto err;
+ } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) {
+ if (NULL == bn_wexpand(rr, 8))
+ goto err;
+ RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d);
+ rr->top = 8;
+ rr->neg = 0;
+ bn_correct_top(rr);
+ ret = 1;
+ goto err;
+ }
+#endif
+
+ /* Get the window size to use with size of p. */
+ window = BN_window_bits_for_ctime_exponent_size(bits);
+#if defined(SPARC_T4_MONT)
+ if (window >= 5 && (top & 15) == 0 && top <= 64 &&
+ (OPENSSL_sparcv9cap_P[1] & (CFR_MONTMUL | CFR_MONTSQR)) ==
+ (CFR_MONTMUL | CFR_MONTSQR) && (t4 = OPENSSL_sparcv9cap_P[0]))
+ window = 5;
+ else
+#endif
+#if defined(OPENSSL_BN_ASM_MONT5)
+ if (window >= 5) {
+ window = 5; /* ~5% improvement for RSA2048 sign, and even
+ * for RSA4096 */
+ /* reserve space for mont->N.d[] copy */
+ powerbufLen += top * sizeof(mont->N.d[0]);
+ }
+#endif
+ (void)0;
+
+ /*
+ * Allocate a buffer large enough to hold all of the pre-computed powers
+ * of am, am itself and tmp.
+ */
+ numPowers = 1 << window;
+ powerbufLen += sizeof(m->d[0]) * (top * numPowers +
+ ((2 * top) >
+ numPowers ? (2 * top) : numPowers));
+#ifdef alloca
+ if (powerbufLen < 3072)
+ powerbufFree =
+ alloca(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH);
+ else
+#endif
+ if ((powerbufFree =
+ OPENSSL_malloc(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH))
+ == NULL)
+ goto err;
+
+ powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree);
+ memset(powerbuf, 0, powerbufLen);
+
+#ifdef alloca
+ if (powerbufLen < 3072)
+ powerbufFree = NULL;
+#endif
+
+ /* lay down tmp and am right after powers table */
+ tmp.d = (BN_ULONG *)(powerbuf + sizeof(m->d[0]) * top * numPowers);
+ am.d = tmp.d + top;
+ tmp.top = am.top = 0;
+ tmp.dmax = am.dmax = top;
+ tmp.neg = am.neg = 0;
+ tmp.flags = am.flags = BN_FLG_STATIC_DATA;
+
+ /* prepare a^0 in Montgomery domain */
+#if 1 /* by Shay Gueron's suggestion */
+ if (m->d[top - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) {
+ /* 2^(top*BN_BITS2) - m */
+ tmp.d[0] = (0 - m->d[0]) & BN_MASK2;
+ for (i = 1; i < top; i++)
+ tmp.d[i] = (~m->d[i]) & BN_MASK2;
+ tmp.top = top;
+ } else
+#endif
+ if (!BN_to_montgomery(&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))
+ goto err;
+ } else if (!BN_to_montgomery(&am, a, mont, ctx))
+ goto err;
+
+#if defined(SPARC_T4_MONT)
+ if (t4) {
+ typedef int (*bn_pwr5_mont_f) (BN_ULONG *tp, const BN_ULONG *np,
+ const BN_ULONG *n0, const void *table,
+ int power, int bits);
+ int bn_pwr5_mont_t4_8(BN_ULONG *tp, const BN_ULONG *np,
+ const BN_ULONG *n0, const void *table,
+ int power, int bits);
+ int bn_pwr5_mont_t4_16(BN_ULONG *tp, const BN_ULONG *np,
+ const BN_ULONG *n0, const void *table,
+ int power, int bits);
+ int bn_pwr5_mont_t4_24(BN_ULONG *tp, const BN_ULONG *np,
+ const BN_ULONG *n0, const void *table,
+ int power, int bits);
+ int bn_pwr5_mont_t4_32(BN_ULONG *tp, const BN_ULONG *np,
+ const BN_ULONG *n0, const void *table,
+ int power, int bits);
+ static const bn_pwr5_mont_f pwr5_funcs[4] = {
+ bn_pwr5_mont_t4_8, bn_pwr5_mont_t4_16,
+ bn_pwr5_mont_t4_24, bn_pwr5_mont_t4_32
+ };
+ bn_pwr5_mont_f pwr5_worker = pwr5_funcs[top / 16 - 1];
+
+ typedef int (*bn_mul_mont_f) (BN_ULONG *rp, const BN_ULONG *ap,
+ const void *bp, const BN_ULONG *np,
+ const BN_ULONG *n0);
+ int bn_mul_mont_t4_8(BN_ULONG *rp, const BN_ULONG *ap, const void *bp,
+ const BN_ULONG *np, const BN_ULONG *n0);
+ int bn_mul_mont_t4_16(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *bp, const BN_ULONG *np,
+ const BN_ULONG *n0);
+ int bn_mul_mont_t4_24(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *bp, const BN_ULONG *np,
+ const BN_ULONG *n0);
+ int bn_mul_mont_t4_32(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *bp, const BN_ULONG *np,
+ const BN_ULONG *n0);
+ static const bn_mul_mont_f mul_funcs[4] = {
+ bn_mul_mont_t4_8, bn_mul_mont_t4_16,
+ bn_mul_mont_t4_24, bn_mul_mont_t4_32
+ };
+ bn_mul_mont_f mul_worker = mul_funcs[top / 16 - 1];
+
+ void bn_mul_mont_vis3(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *bp, const BN_ULONG *np,
+ const BN_ULONG *n0, int num);
+ void bn_mul_mont_t4(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *bp, const BN_ULONG *np,
+ const BN_ULONG *n0, int num);
+ void bn_mul_mont_gather5_t4(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *table, const BN_ULONG *np,
+ const BN_ULONG *n0, int num, int power);
+ void bn_flip_n_scatter5_t4(const BN_ULONG *inp, size_t num,
+ void *table, size_t power);
+ void bn_gather5_t4(BN_ULONG *out, size_t num,
+ void *table, size_t power);
+ void bn_flip_t4(BN_ULONG *dst, BN_ULONG *src, size_t num);
+
+ BN_ULONG *np = mont->N.d, *n0 = mont->n0;
+ int stride = 5 * (6 - (top / 16 - 1)); /* multiple of 5, but less
+ * than 32 */
+
+ /*
+ * BN_to_montgomery can contaminate words above .top [in
+ * BN_DEBUG[_DEBUG] build]...
+ */
+ for (i = am.top; i < top; i++)
+ am.d[i] = 0;
+ for (i = tmp.top; i < top; i++)
+ tmp.d[i] = 0;
+
+ bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 0);
+ bn_flip_n_scatter5_t4(am.d, top, powerbuf, 1);
+ if (!(*mul_worker) (tmp.d, am.d, am.d, np, n0) &&
+ !(*mul_worker) (tmp.d, am.d, am.d, np, n0))
+ bn_mul_mont_vis3(tmp.d, am.d, am.d, np, n0, top);
+ bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 2);
+
+ for (i = 3; i < 32; i++) {
+ /* Calculate a^i = a^(i-1) * a */
+ if (!(*mul_worker) (tmp.d, tmp.d, am.d, np, n0) &&
+ !(*mul_worker) (tmp.d, tmp.d, am.d, np, n0))
+ bn_mul_mont_vis3(tmp.d, tmp.d, am.d, np, n0, top);
+ bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, i);
+ }
+
+ /* switch to 64-bit domain */
+ np = alloca(top * sizeof(BN_ULONG));
+ top /= 2;
+ bn_flip_t4(np, mont->N.d, top);
+
+ bits--;
+ for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--)
+ wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+ bn_gather5_t4(tmp.d, top, powerbuf, wvalue);
+
+ /*
+ * Scan the exponent one window at a time starting from the most
+ * significant bits.
+ */
+ while (bits >= 0) {
+ if (bits < stride)
+ stride = bits + 1;
+ bits -= stride;
+ wvalue = bn_get_bits(p, bits + 1);
+
+ if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride))
+ continue;
+ /* retry once and fall back */
+ if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride))
+ continue;
+
+ bits += stride - 5;
+ wvalue >>= stride - 5;
+ wvalue &= 31;
+ bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont_gather5_t4(tmp.d, tmp.d, powerbuf, np, n0, top,
+ wvalue);
+ }
+
+ bn_flip_t4(tmp.d, tmp.d, top);
+ top *= 2;
+ /* back to 32-bit domain */
+ tmp.top = top;
+ bn_correct_top(&tmp);
+ OPENSSL_cleanse(np, top * sizeof(BN_ULONG));
+ } else
+#endif
+#if defined(OPENSSL_BN_ASM_MONT5)
+ if (window == 5 && top > 1) {
+ /*
+ * This optimization uses ideas from http://eprint.iacr.org/2011/239,
+ * specifically optimization of cache-timing attack countermeasures
+ * and pre-computation optimization.
+ */
+
+ /*
+ * Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as
+ * 512-bit RSA is hardly relevant, we omit it to spare size...
+ */
+ void bn_mul_mont_gather5(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *table, const BN_ULONG *np,
+ const BN_ULONG *n0, int num, int power);
+ void bn_scatter5(const BN_ULONG *inp, size_t num,
+ void *table, size_t power);
+ void bn_gather5(BN_ULONG *out, size_t num, void *table, size_t power);
+ void bn_power5(BN_ULONG *rp, const BN_ULONG *ap,
+ const void *table, const BN_ULONG *np,
+ const BN_ULONG *n0, int num, int power);
+ int bn_get_bits5(const BN_ULONG *ap, int off);
+ int bn_from_montgomery(BN_ULONG *rp, const BN_ULONG *ap,
+ const BN_ULONG *not_used, const BN_ULONG *np,
+ const BN_ULONG *n0, int num);
+
+ BN_ULONG *n0 = mont->n0, *np;
+
+ /*
+ * BN_to_montgomery can contaminate words above .top [in
+ * BN_DEBUG[_DEBUG] build]...
+ */
+ for (i = am.top; i < top; i++)
+ am.d[i] = 0;
+ for (i = tmp.top; i < top; i++)
+ tmp.d[i] = 0;
+
+ /*
+ * copy mont->N.d[] to improve cache locality
+ */
+ for (np = am.d + top, i = 0; i < top; i++)
+ np[i] = mont->N.d[i];
+
+ bn_scatter5(tmp.d, top, powerbuf, 0);
+ bn_scatter5(am.d, am.top, powerbuf, 1);
+ bn_mul_mont(tmp.d, am.d, am.d, np, n0, top);
+ bn_scatter5(tmp.d, top, powerbuf, 2);
+
+# if 0
+ for (i = 3; i < 32; i++) {
+ /* Calculate a^i = a^(i-1) * a */
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
+ bn_scatter5(tmp.d, top, powerbuf, i);
+ }
+# else
+ /* same as above, but uses squaring for 1/2 of operations */
+ for (i = 4; i < 32; i *= 2) {
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_scatter5(tmp.d, top, powerbuf, i);
+ }
+ for (i = 3; i < 8; i += 2) {
+ int j;
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
+ bn_scatter5(tmp.d, top, powerbuf, i);
+ for (j = 2 * i; j < 32; j *= 2) {
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_scatter5(tmp.d, top, powerbuf, j);
+ }
+ }
+ for (; i < 16; i += 2) {
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
+ bn_scatter5(tmp.d, top, powerbuf, i);
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_scatter5(tmp.d, top, powerbuf, 2 * i);
+ }
+ for (; i < 32; i += 2) {
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
+ bn_scatter5(tmp.d, top, powerbuf, i);
+ }
+# endif
+ bits--;
+ for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--)
+ wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+ bn_gather5(tmp.d, top, powerbuf, wvalue);
+
+ /*
+ * Scan the exponent one window at a time starting from the most
+ * significant bits.
+ */
+ if (top & 7)
+ while (bits >= 0) {
+ for (wvalue = 0, i = 0; i < 5; i++, bits--)
+ wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
+ bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top,
+ wvalue);
+ } else {
+ while (bits >= 0) {
+ wvalue = bn_get_bits5(p->d, bits - 4);
+ bits -= 5;
+ bn_power5(tmp.d, tmp.d, powerbuf, np, n0, top, wvalue);
+ }
+ }
+
+ ret = bn_from_montgomery(tmp.d, tmp.d, NULL, np, n0, top);
+ tmp.top = top;
+ bn_correct_top(&tmp);
+ if (ret) {
+ if (!BN_copy(rr, &tmp))
+ ret = 0;
+ goto err; /* non-zero ret means it's not error */
+ }
+ } else
+#endif
+ {
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, window))
+ goto err;
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, window))
+ goto err;
+
+ /*
+ * If the window size is greater than 1, then calculate
+ * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1) (even
+ * powers could instead be computed as (a^(i/2))^2 to use the slight
+ * performance advantage of sqr over mul).
+ */
+ if (window > 1) {
+ if (!BN_mod_mul_montgomery(&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))
+ goto err;
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i,
+ window))
+ goto err;
+ }
+ }
+
+ bits--;
+ for (wvalue = 0, i = bits % window; i >= 0; i--, bits--)
+ wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+ if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, wvalue,
+ window))
+ goto err;
+
+ /*
+ * Scan the exponent one window at a time starting from the most
+ * significant bits.
+ */
+ while (bits >= 0) {
+ wvalue = 0; /* The 'value' of the window */
+
+ /* 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))
+ goto err;
+ wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+ }
+
+ /*
+ * Fetch the appropriate pre-computed value from the pre-buf
+ */
+ if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, wvalue,
+ window))
+ goto err;
+
+ /* Multiply the result into the intermediate result */
+ if (!BN_mod_mul_montgomery(&tmp, &tmp, &am, mont, ctx))
+ goto err;
+ }
+ }
+
+ /* Convert the final result from montgomery to standard format */
+#if defined(SPARC_T4_MONT)
+ if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) {
+ am.d[0] = 1; /* borrow am */
+ for (i = 1; i < top; i++)
+ am.d[i] = 0;
+ if (!BN_mod_mul_montgomery(rr, &tmp, &am, mont, ctx))
+ goto err;
+ } else
+#endif
+ if (!BN_from_montgomery(rr, &tmp, mont, ctx))
+ goto err;
+ ret = 1;
+ err:
+ if (in_mont == NULL)
+ BN_MONT_CTX_free(mont);
+ if (powerbuf != NULL) {
+ OPENSSL_cleanse(powerbuf, powerbufLen);
+ OPENSSL_free(powerbufFree);
+ }
+ BN_CTX_end(ctx);
+ return (ret);
+}
+
+int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
+ const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
+{
+ BN_MONT_CTX *mont = NULL;
+ int b, bits, ret = 0;
+ int r_is_one;
+ BN_ULONG w, next_w;
+ BIGNUM *d, *r, *t;
+ BIGNUM *swap_tmp;
+#define BN_MOD_MUL_WORD(r, w, m) \
+ (BN_mul_word(r, (w)) && \
+ (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \
+ (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1))))
+ /*
+ * BN_MOD_MUL_WORD is only used with 'w' large, so the BN_ucmp test is
+ * probably more overhead than always using BN_mod (which uses BN_copy if
+ * a similar test returns true).
+ */
+ /*
+ * We can use BN_mod and do not need BN_nnmod because our accumulator is
+ * never negative (the result of BN_mod does not depend on the sign of
+ * the modulus).
+ */
+#define BN_TO_MONTGOMERY_WORD(r, w, mont) \
+ (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
+
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_MOD_EXP_MONT_WORD, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return 0;
+ }
+
+ bn_check_top(p);
+ bn_check_top(m);
+
+ if (!BN_is_odd(m)) {
+ BNerr(BN_F_BN_MOD_EXP_MONT_WORD, BN_R_CALLED_WITH_EVEN_MODULUS);
+ return (0);
+ }
+ if (m->top == 1)
+ a %= m->d[0]; /* make sure that 'a' is reduced */
+
+ bits = BN_num_bits(p);
+ if (bits == 0) {
+ /* x**0 mod 1 is still zero. */
+ if (BN_is_one(m)) {
+ ret = 1;
+ BN_zero(rr);
+ } else {
+ ret = BN_one(rr);
+ }
+ return ret;
+ }
+ if (a == 0) {
+ BN_zero(rr);
+ ret = 1;
+ return ret;
+ }
+
+ BN_CTX_start(ctx);
+ d = BN_CTX_get(ctx);
+ r = BN_CTX_get(ctx);
+ t = BN_CTX_get(ctx);
+ if (d == NULL || r == NULL || t == NULL)
+ goto err;
+
+ if (in_mont != NULL)
+ mont = in_mont;
+ else {
+ if ((mont = BN_MONT_CTX_new()) == NULL)
+ goto err;
+ if (!BN_MONT_CTX_set(mont, m, ctx))
+ goto err;
+ }
+
+ r_is_one = 1; /* except for Montgomery factor */
+
+ /* bits-1 >= 0 */
+
+ /* The result is accumulated in the product r*w. */
+ w = a; /* bit 'bits-1' of 'p' is always set */
+ for (b = bits - 2; b >= 0; b--) {
+ /* First, square r*w. */
+ next_w = w * w;
+ if ((next_w / w) != w) { /* overflow */
+ if (r_is_one) {
+ if (!BN_TO_MONTGOMERY_WORD(r, w, mont))
+ goto err;
+ r_is_one = 0;
+ } else {
+ if (!BN_MOD_MUL_WORD(r, w, m))
+ goto err;
+ }
+ next_w = 1;
+ }
+ w = next_w;
+ if (!r_is_one) {
+ if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
+ goto err;
+ }
+
+ /* Second, multiply r*w by 'a' if exponent bit is set. */
+ if (BN_is_bit_set(p, b)) {
+ next_w = w * a;
+ if ((next_w / a) != w) { /* overflow */
+ if (r_is_one) {
+ if (!BN_TO_MONTGOMERY_WORD(r, w, mont))
+ goto err;
+ r_is_one = 0;
+ } else {
+ if (!BN_MOD_MUL_WORD(r, w, m))
+ goto err;
+ }
+ next_w = a;
+ }
+ w = next_w;
+ }
+ }
+
+ /* Finally, set r:=r*w. */
+ if (w != 1) {
+ if (r_is_one) {
+ if (!BN_TO_MONTGOMERY_WORD(r, w, mont))
+ goto err;
+ r_is_one = 0;
+ } else {
+ if (!BN_MOD_MUL_WORD(r, w, m))
+ goto err;
+ }
+ }
+
+ if (r_is_one) { /* can happen only if a == 1 */
+ if (!BN_one(rr))
+ goto err;
+ } else {
+ if (!BN_from_montgomery(rr, r, mont, ctx))
+ goto err;
+ }
+ ret = 1;
+ err:
+ if (in_mont == NULL)
+ BN_MONT_CTX_free(mont);
+ BN_CTX_end(ctx);
+ bn_check_top(rr);
+ return (ret);
+}
+
+/* The old fallback, simple version :-) */
+int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+ const BIGNUM *m, BN_CTX *ctx)
+{
+ int i, j, bits, ret = 0, wstart, wend, window, wvalue;
+ int start = 1;
+ BIGNUM *d;
+ /* Table of variables obtained from 'ctx' */
+ BIGNUM *val[TABLE_SIZE];
+
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_MOD_EXP_SIMPLE, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return 0;
+ }
+
+ bits = BN_num_bits(p);
+ if (bits == 0) {
+ /* x**0 mod 1 is still zero. */
+ if (BN_is_one(m)) {
+ ret = 1;
+ BN_zero(r);
+ } else {
+ ret = BN_one(r);
+ }
+ return ret;
+ }
+
+ BN_CTX_start(ctx);
+ d = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if (!d || !val[0])
+ goto err;
+
+ if (!BN_nnmod(val[0], a, m, ctx))
+ goto err; /* 1 */
+ if (BN_is_zero(val[0])) {
+ BN_zero(r);
+ ret = 1;
+ goto err;
+ }
+
+ window = BN_window_bits_for_exponent_size(bits);
+ if (window > 1) {
+ if (!BN_mod_mul(d, val[0], val[0], m, 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(val[i], val[i - 1], d, m, ctx))
+ goto err;
+ }
+ }
+
+ start = 1; /* This is used to avoid multiplication etc
+ * when there is only the value '1' in the
+ * buffer. */
+ wvalue = 0; /* The 'value' of the window */
+ wstart = bits - 1; /* The top bit of the window */
+ wend = 0; /* The bottom bit of the window */
+
+ if (!BN_one(r))
+ goto err;
+
+ for (;;) {
+ if (BN_is_bit_set(p, wstart) == 0) {
+ if (!start)
+ if (!BN_mod_mul(r, r, r, m, ctx))
+ goto err;
+ if (wstart == 0)
+ break;
+ wstart--;
+ continue;
+ }
+ /*
+ * We now have wstart on a 'set' bit, we now need to work out how bit
+ * a window to do. To do this we need to scan forward until the last
+ * set bit before the end of the window
+ */
+ j = wstart;
+ wvalue = 1;
+ wend = 0;
+ for (i = 1; i < window; i++) {
+ if (wstart - i < 0)
+ break;
+ if (BN_is_bit_set(p, wstart - i)) {
+ wvalue <<= (i - wend);
+ wvalue |= 1;
+ wend = i;
+ }
+ }
+
+ /* wend is the size of the current window */
+ j = wend + 1;
+ /* add the 'bytes above' */
+ if (!start)
+ for (i = 0; i < j; i++) {
+ if (!BN_mod_mul(r, r, r, m, ctx))
+ goto err;
+ }
+
+ /* wvalue will be an odd number < 2^window */
+ if (!BN_mod_mul(r, r, val[wvalue >> 1], m, ctx))
+ goto err;
+
+ /* move the 'window' down further */
+ wstart -= wend + 1;
+ wvalue = 0;
+ start = 0;
+ if (wstart < 0)
+ break;
+ }
+ ret = 1;
+ err:
+ BN_CTX_end(ctx);
+ bn_check_top(r);
+ return (ret);
+}
generated by cgit