+ bn_check_top(r);
+ ret = 1;
+ err:
+ BN_CTX_end(ctx);
+ return (ret);
+}
+
+#ifdef MONT_WORD
+static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)
+{
+ BIGNUM *n;
+ BN_ULONG *ap, *np, *rp, n0, v, carry;
+ int nl, max, i;
+
+ n = &(mont->N);
+ nl = n->top;
+ if (nl == 0) {
+ ret->top = 0;
+ return (1);
+ }
+
+ max = (2 * nl); /* carry is stored separately */
+ if (bn_wexpand(r, max) == NULL)
+ return (0);
+
+ r->neg ^= n->neg;
+ np = n->d;
+ rp = r->d;
+
+ /* clear the top words of T */
+ i = max - r->top;
+ if (i)
+ memset(&rp[r->top], 0, sizeof(*rp) * i);
+
+ r->top = max;
+ n0 = mont->n0[0];
+
+ for (carry = 0, i = 0; i < nl; i++, rp++) {
+ v = bn_mul_add_words(rp, np, nl, (rp[0] * n0) & BN_MASK2);
+ v = (v + carry + rp[nl]) & BN_MASK2;
+ carry |= (v != rp[nl]);
+ carry &= (v <= rp[nl]);
+ rp[nl] = v;
+ }
+
+ if (bn_wexpand(ret, nl) == NULL)
+ return (0);
+ ret->top = nl;
+ ret->neg = r->neg;
+
+ rp = ret->d;
+ ap = &(r->d[nl]);
+
+# define BRANCH_FREE 1
+# if BRANCH_FREE
+ {
+ BN_ULONG *nrp;
+ size_t m;
+
+ v = bn_sub_words(rp, ap, np, nl) - carry;
+ /*
+ * if subtraction result is real, then trick unconditional memcpy
+ * below to perform in-place "refresh" instead of actual copy.
+ */
+ m = (0 - (size_t)v);
+ nrp =
+ (BN_ULONG *)(((PTR_SIZE_INT) rp & ~m) | ((PTR_SIZE_INT) ap & m));
+
+ for (i = 0, nl -= 4; i < nl; i += 4) {
+ BN_ULONG t1, t2, t3, t4;
+
+ t1 = nrp[i + 0];
+ t2 = nrp[i + 1];
+ t3 = nrp[i + 2];
+ ap[i + 0] = 0;
+ t4 = nrp[i + 3];
+ ap[i + 1] = 0;
+ rp[i + 0] = t1;
+ ap[i + 2] = 0;
+ rp[i + 1] = t2;
+ ap[i + 3] = 0;
+ rp[i + 2] = t3;
+ rp[i + 3] = t4;
+ }
+ for (nl += 4; i < nl; i++)
+ rp[i] = nrp[i], ap[i] = 0;
+ }
+# else
+ if (bn_sub_words(rp, ap, np, nl) - carry)
+ memcpy(rp, ap, nl * sizeof(BN_ULONG));
+# endif
+ bn_correct_top(r);
+ bn_correct_top(ret);
+ bn_check_top(ret);
+
+ return (1);
+}
+#endif /* MONT_WORD */
+
+int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
+ BN_CTX *ctx)
+{
+ int retn = 0;
+#ifdef MONT_WORD
+ BIGNUM *t;
+
+ BN_CTX_start(ctx);
+ if ((t = BN_CTX_get(ctx)) && BN_copy(t, a))
+ retn = BN_from_montgomery_word(ret, t, mont);
+ BN_CTX_end(ctx);
+#else /* !MONT_WORD */
+ BIGNUM *t1, *t2;
+
+ BN_CTX_start(ctx);
+ t1 = BN_CTX_get(ctx);
+ t2 = BN_CTX_get(ctx);
+ if (t1 == NULL || t2 == NULL)
+ goto err;
+
+ if (!BN_copy(t1, a))
+ goto err;
+ BN_mask_bits(t1, mont->ri);
+
+ if (!BN_mul(t2, t1, &mont->Ni, ctx))
+ goto err;
+ BN_mask_bits(t2, mont->ri);
+
+ if (!BN_mul(t1, t2, &mont->N, ctx))
+ goto err;
+ if (!BN_add(t2, a, t1))
+ goto err;
+ if (!BN_rshift(ret, t2, mont->ri))
+ goto err;
+
+ if (BN_ucmp(ret, &(mont->N)) >= 0) {
+ if (!BN_usub(ret, ret, &(mont->N)))
+ goto err;
+ }
+ retn = 1;
+ bn_check_top(ret);
+ err:
+ BN_CTX_end(ctx);
+#endif /* MONT_WORD */
+ return (retn);
+}
+
+BN_MONT_CTX *BN_MONT_CTX_new(void)
+{
+ BN_MONT_CTX *ret;
+
+ if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL)
+ return (NULL);
+
+ BN_MONT_CTX_init(ret);
+ ret->flags = BN_FLG_MALLOCED;
+ return (ret);
+}
+
+void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
+{
+ ctx->ri = 0;
+ BN_init(&(ctx->RR));
+ BN_init(&(ctx->N));
+ BN_init(&(ctx->Ni));
+ ctx->n0[0] = ctx->n0[1] = 0;
+ ctx->flags = 0;
+}
+
+void BN_MONT_CTX_free(BN_MONT_CTX *mont)
+{
+ if (mont == NULL)
+ return;
+
+ BN_clear_free(&(mont->RR));
+ BN_clear_free(&(mont->N));
+ BN_clear_free(&(mont->Ni));
+ if (mont->flags & BN_FLG_MALLOCED)
+ OPENSSL_free(mont);
+}
+
+int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
+{
+ int ret = 0;
+ BIGNUM *Ri, *R;
+
+ if (BN_is_zero(mod))
+ return 0;
+
+ BN_CTX_start(ctx);
+ if ((Ri = BN_CTX_get(ctx)) == NULL)
+ goto err;
+ R = &(mont->RR); /* grab RR as a temp */
+ if (!BN_copy(&(mont->N), mod))
+ goto err; /* Set N */
+ mont->N.neg = 0;
+
+#ifdef MONT_WORD
+ {
+ BIGNUM tmod;
+ BN_ULONG buf[2];
+
+ BN_init(&tmod);
+ tmod.d = buf;
+ tmod.dmax = 2;
+ tmod.neg = 0;
+
+ mont->ri = (BN_num_bits(mod) + (BN_BITS2 - 1)) / BN_BITS2 * BN_BITS2;
+
+# if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)
+ /*
+ * Only certain BN_BITS2<=32 platforms actually make use of n0[1],
+ * and we could use the #else case (with a shorter R value) for the
+ * others. However, currently only the assembler files do know which
+ * is which.
+ */
+
+ BN_zero(R);
+ if (!(BN_set_bit(R, 2 * BN_BITS2)))
+ goto err;
+
+ tmod.top = 0;
+ if ((buf[0] = mod->d[0]))
+ tmod.top = 1;
+ if ((buf[1] = mod->top > 1 ? mod->d[1] : 0))
+ tmod.top = 2;
+
+ if ((BN_mod_inverse(Ri, R, &tmod, ctx)) == NULL)
+ goto err;
+ if (!BN_lshift(Ri, Ri, 2 * BN_BITS2))
+ goto err; /* R*Ri */
+ if (!BN_is_zero(Ri)) {
+ if (!BN_sub_word(Ri, 1))
+ goto err;
+ } else { /* if N mod word size == 1 */
+
+ if (bn_expand(Ri, (int)sizeof(BN_ULONG) * 2) == NULL)
+ goto err;
+ /* Ri-- (mod double word size) */
+ Ri->neg = 0;
+ Ri->d[0] = BN_MASK2;
+ Ri->d[1] = BN_MASK2;
+ Ri->top = 2;
+ }
+ if (!BN_div(Ri, NULL, Ri, &tmod, ctx))
+ goto err;
+ /*
+ * Ni = (R*Ri-1)/N, keep only couple of least significant words:
+ */
+ mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
+ mont->n0[1] = (Ri->top > 1) ? Ri->d[1] : 0;
+# else
+ BN_zero(R);
+ if (!(BN_set_bit(R, BN_BITS2)))
+ goto err; /* R */
+
+ buf[0] = mod->d[0]; /* tmod = N mod word size */
+ buf[1] = 0;
+ tmod.top = buf[0] != 0 ? 1 : 0;
+ /* Ri = R^-1 mod N */
+ if ((BN_mod_inverse(Ri, R, &tmod, ctx)) == NULL)
+ goto err;
+ if (!BN_lshift(Ri, Ri, BN_BITS2))
+ goto err; /* R*Ri */
+ if (!BN_is_zero(Ri)) {
+ if (!BN_sub_word(Ri, 1))
+ goto err;
+ } else { /* if N mod word size == 1 */
+
+ if (!BN_set_word(Ri, BN_MASK2))
+ goto err; /* Ri-- (mod word size) */
+ }
+ if (!BN_div(Ri, NULL, Ri, &tmod, ctx))
+ goto err;
+ /*
+ * Ni = (R*Ri-1)/N, keep only least significant word:
+ */
+ mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
+ mont->n0[1] = 0;
+# endif
+ }
+#else /* !MONT_WORD */
+ { /* bignum version */
+ mont->ri = BN_num_bits(&mont->N);
+ BN_zero(R);
+ if (!BN_set_bit(R, mont->ri))
+ goto err; /* R = 2^ri */
+ /* Ri = R^-1 mod N */
+ if ((BN_mod_inverse(Ri, R, &mont->N, ctx)) == NULL)
+ goto err;
+ if (!BN_lshift(Ri, Ri, mont->ri))
+ goto err; /* R*Ri */
+ if (!BN_sub_word(Ri, 1))
+ goto err;
+ /*
+ * Ni = (R*Ri-1) / N
+ */
+ if (!BN_div(&(mont->Ni), NULL, Ri, &mont->N, ctx))
+ goto err;
+ }