- {
- BIGNUM Ri,*R;
-
- BN_init(&Ri);
- R= &(mont->RR); /* grab RR as a temp */
- BN_copy(&(mont->N),mod); /* Set N */
-
-#ifdef BN_RECURSION_MONT
- /* the word-based algorithm is faster */
- if (mont->N.top > BN_MONT_CTX_SET_SIZE_WORD)
-#endif
- {
- BIGNUM tmod;
- BN_ULONG buf[2];
-
- mont->use_word=1;
-
- mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
- BN_zero(R);
- BN_set_bit(R,BN_BITS2); /* R */
-
- buf[0]=mod->d[0]; /* tmod = N mod word size */
- buf[1]=0;
- tmod.d=buf;
- tmod.top=1;
- tmod.max=2;
- tmod.neg=mod->neg;
- /* Ri = R^-1 mod N*/
- if ((BN_mod_inverse(&Ri,R,&tmod,ctx)) == NULL)
- goto err;
- BN_lshift(&Ri,&Ri,BN_BITS2); /* R*Ri */
- if (!BN_is_zero(&Ri))
- BN_sub_word(&Ri,1);
- else /* if N mod word size == 1 */
- BN_set_word(&Ri,BN_MASK2); /* Ri-- (mod word size) */
- BN_div(&Ri,NULL,&Ri,&tmod,ctx); /* Ni = (R*Ri-1)/N,
- * keep only least significant word: */
- mont->n0=Ri.d[0];
- BN_free(&Ri);
- }
-#ifdef BN_RECURSION_MONT
- else
- { /* bignum version */
- mont->use_word=0;
- mont->ri=BN_num_bits(mod);
- BN_zero(R);
- BN_set_bit(R,mont->ri); /* R = 2^ri */
- /* Ri = R^-1 mod N*/
- if ((BN_mod_inverse(&Ri,R,mod,ctx)) == NULL)
- goto err;
- BN_lshift(&Ri,&Ri,mont->ri); /* R*Ri */
- BN_sub_word(&Ri,1);
- /* Ni = (R*Ri-1) / N */
- BN_div(&(mont->Ni),NULL,&Ri,mod,ctx);
- BN_free(&Ri);
- }
+{
+ 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;
+ }