Move BN_RECP_CTX to the heap

This introduces a BN_RECP_CTX_create() function that allocates and
populates the BN_RECP_CTX in a single call, without taking an unused
BN_CTX argument.

At the same time, make the N and Nr members BIGNUMs on the heap which
are allocated by BN_RECP_CTX_create() and freed by BN_RECP_CTX_free()
and remove the unnecessary flags argument.

Garbage collect the now unused BN_RECP_CTX_{new,init,set}().

ok jsing

1 files changed, 34 insertions, 40 deletions

diff --git a/src/lib/libcrypto/bn/bn_recp.c b/src/lib/libcrypto/bn/bn_recp.c
index 44c5b05e4d..e7484f9f4b 100644
--- a/src/lib/libcrypto/bn/bn_recp.c
+++ b/src/lib/libcrypto/bn/bn_recp.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_recp.c,v 1.25 2025/01/08 20:21:28 tb Exp $ */
+/* $OpenBSD: bn_recp.c,v 1.26 2025/01/21 15:44:22 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -62,26 +62,34 @@
 
 #include "bn_local.h"
 
-void
-BN_RECP_CTX_init(BN_RECP_CTX *recp)
-{
-        BN_init(&recp->N);
-        BN_init(&recp->Nr);
-        recp->num_bits = 0;
-        recp->flags = 0;
-}
+struct bn_recp_ctx_st {
+        BIGNUM *N;      /* the divisor */
+        BIGNUM *Nr;     /* the reciprocal 2^shift / N */
+        int num_bits;   /* number of bits in N */
+        int shift;
+} /* BN_RECP_CTX */;
 
 BN_RECP_CTX *
-BN_RECP_CTX_new(void)
+BN_RECP_CTX_create(const BIGNUM *N)
 {
-        BN_RECP_CTX *ret;
+        BN_RECP_CTX *recp;
 
-        if ((ret = malloc(sizeof(BN_RECP_CTX))) == NULL)
-                return NULL;
+        if ((recp = calloc(1, sizeof(*recp))) == NULL)
+                goto err;
 
-        BN_RECP_CTX_init(ret);
-        ret->flags = BN_FLG_MALLOCED;
-        return ret;
+        if ((recp->N = BN_dup(N)) == NULL)
+                goto err;
+        recp->num_bits = BN_num_bits(recp->N);
+
+        if ((recp->Nr = BN_new()) == NULL)
+                goto err;
+
+        return recp;
+
+ err:
+        BN_RECP_CTX_free(recp);
+
+        return NULL;
 }
 
 void
@@ -90,23 +98,9 @@ BN_RECP_CTX_free(BN_RECP_CTX *recp)
         if (recp == NULL)
                 return;
 
-        BN_free(&recp->N);
-        BN_free(&recp->Nr);
-        if (recp->flags & BN_FLG_MALLOCED)
-                free(recp);
-}
-
-int
-BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)
-{
-        if (!bn_copy(&recp->N, d))
-                return 0;
-        recp->num_bits = BN_num_bits(&recp->N);
-
-        BN_zero(&recp->Nr);
-        recp->shift = 0;
-
-        return 1;
+        BN_free(recp->N);
+        BN_free(recp->Nr);
+        freezero(recp, sizeof(*recp));
 }
 
 /* len is the expected size of the result
@@ -158,7 +152,7 @@ BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp,
         if (a == NULL || b == NULL || d == NULL || r == NULL)
                 goto err;
 
-        if (BN_ucmp(m, &recp->N) < 0) {
+        if (BN_ucmp(m, recp->N) < 0) {
                 BN_zero(d);
                 if (!bn_copy(r, m)) {
                         BN_CTX_end(ctx);
@@ -182,7 +176,7 @@ BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp,
 
         /* Nr := round(2^i / N) */
         if (i != recp->shift)
-                recp->shift = BN_reciprocal(&recp->Nr, &recp->N, i, ctx);
+                recp->shift = BN_reciprocal(recp->Nr, recp->N, i, ctx);
 
         /* BN_reciprocal returns i, or -1 for an error */
         if (recp->shift == -1)
@@ -195,13 +189,13 @@ BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp,
          */
         if (!BN_rshift(a, m, recp->num_bits))
                 goto err;
-        if (!BN_mul(b, a, &recp->Nr, ctx))
+        if (!BN_mul(b, a, recp->Nr, ctx))
                 goto err;
         if (!BN_rshift(d, b, i - recp->num_bits))
                 goto err;
         d->neg = 0;
 
-        if (!BN_mul(b, &recp->N, d, ctx))
+        if (!BN_mul(b, recp->N, d, ctx))
                 goto err;
         if (!BN_usub(r, m, b))
                 goto err;
@@ -209,12 +203,12 @@ BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp,
 
 #if 1
         j = 0;
-        while (BN_ucmp(r, &recp->N) >= 0) {
+        while (BN_ucmp(r, recp->N) >= 0) {
                 if (j++ > 2) {
                         BNerror(BN_R_BAD_RECIPROCAL);
                         goto err;
                 }
-                if (!BN_usub(r, r, &recp->N))
+                if (!BN_usub(r, r, recp->N))
                         goto err;
                 if (!BN_add_word(d, 1))
                         goto err;
@@ -222,7 +216,7 @@ BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp,
 #endif
 
         BN_set_negative(r, m->neg);
-        BN_set_negative(d, m->neg ^ recp->N.neg);
+        BN_set_negative(d, m->neg ^ recp->N->neg);
 
         ret = 1;