Handle BN_CTX at the EC API boundary.

The EC API allows callers to optionally pass in a BN_CTX, which means that
any code needing a BN_CTX has to check if one was provided, allocate one if
not, then free it again. Rather than doing this dance throughout the EC
code, handle the BN_CTX existance at the EC API boundary. This means that
lower level implementation code can simply assume that the BN_CTX is
available.

ok tb@

1 files changed, 56 insertions, 14 deletions

diff --git a/src/lib/libcrypto/ec/ec_oct.c b/src/lib/libcrypto/ec/ec_oct.c
index ef17ec59a5..b1c9e6a634 100644
--- a/src/lib/libcrypto/ec/ec_oct.c
+++ b/src/lib/libcrypto/ec/ec_oct.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ec_oct.c,v 1.10 2023/03/08 04:50:27 jsing Exp $ */
+/* $OpenBSD: ec_oct.c,v 1.11 2023/04/11 18:58:20 jsing Exp $ */
 /*
  * Originally written by Bodo Moeller for the OpenSSL project.
  */
@@ -72,18 +72,32 @@
 
 int
 EC_POINT_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point,
-    const BIGNUM *x, int y_bit, BN_CTX *ctx)
+    const BIGNUM *x, int y_bit, BN_CTX *ctx_in)
 {
+        BN_CTX *ctx;
+        int ret = 0;
+
+        if ((ctx = ctx_in) == NULL)
+                ctx = BN_CTX_new();
+        if (ctx == NULL)
+                goto err;
+
         if (group->meth->point_set_compressed_coordinates == NULL) {
                 ECerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-                return 0;
+                goto err;
         }
         if (group->meth != point->meth) {
                 ECerror(EC_R_INCOMPATIBLE_OBJECTS);
-                return 0;
+                goto err;
         }
-        return group->meth->point_set_compressed_coordinates(group, point,
+        ret = group->meth->point_set_compressed_coordinates(group, point,
             x, y_bit, ctx);
+
+ err:
+        if (ctx != ctx_in)
+                BN_CTX_free(ctx);
+
+        return ret;
 }
 
 int
@@ -104,31 +118,59 @@ EC_POINT_set_compressed_coordinates_GF2m(const EC_GROUP *group, EC_POINT *point,
 
 size_t
 EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *point,
-    point_conversion_form_t form,
-    unsigned char *buf, size_t len, BN_CTX *ctx)
+    point_conversion_form_t form, unsigned char *buf, size_t len,
+    BN_CTX *ctx_in)
 {
+        BN_CTX *ctx;
+        int ret = 0;
+
+        if ((ctx = ctx_in) == NULL)
+                ctx = BN_CTX_new();
+        if (ctx == NULL)
+                goto err;
+
         if (group->meth->point2oct == NULL) { 
                 ECerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-                return 0;
+                goto err;
         }
         if (group->meth != point->meth) {
                 ECerror(EC_R_INCOMPATIBLE_OBJECTS);
-                return 0;
+                goto err;
         }
-        return group->meth->point2oct(group, point, form, buf, len, ctx);
+        ret = group->meth->point2oct(group, point, form, buf, len, ctx);
+
+ err:
+        if (ctx != ctx_in)
+                BN_CTX_free(ctx);
+
+        return ret;
 }
 
 int
 EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *point,
-    const unsigned char *buf, size_t len, BN_CTX *ctx)
+    const unsigned char *buf, size_t len, BN_CTX *ctx_in)
 {
+        BN_CTX *ctx;
+        int ret = 0;
+
+        if ((ctx = ctx_in) == NULL)
+                ctx = BN_CTX_new();
+        if (ctx == NULL)
+                goto err;
+
         if (group->meth->oct2point == NULL) {
                 ECerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-                return 0;
+                goto err;
         }
         if (group->meth != point->meth) {
                 ECerror(EC_R_INCOMPATIBLE_OBJECTS);
-                return 0;
+                goto err;
         }
-        return group->meth->oct2point(group, point, buf, len, ctx);
+        ret = group->meth->oct2point(group, point, buf, len, ctx);
+
+ err:
+        if (ctx != ctx_in)
+                BN_CTX_free(ctx);
+
+        return ret;
 }