Move a check for hybrid point encoding into a helper function

1 files changed, 14 insertions, 7 deletions

diff --git a/src/lib/libcrypto/ec/ecp_oct.c b/src/lib/libcrypto/ec/ecp_oct.c
index 0a66a5cd48..d4ef0406f5 100644
--- a/src/lib/libcrypto/ec/ecp_oct.c
+++ b/src/lib/libcrypto/ec/ecp_oct.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ecp_oct.c,v 1.25 2024/10/22 21:10:45 tb Exp $ */
+/* $OpenBSD: ecp_oct.c,v 1.26 2024/10/22 21:28:53 tb Exp $ */
 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
  * for the OpenSSL project.
  * Includes code written by Bodo Moeller for the OpenSSL project.
@@ -209,6 +209,17 @@ ec_oct_conversion_form_is_valid(uint8_t form)
         return (form & EC_OCT_POINT_CONVERSION_MASK) == form;
 }
 
+static int
+ec_oct_check_hybrid_ybit_is_consistent(uint8_t form, int ybit, const BIGNUM *y)
+{
+        if (form == EC_OCT_POINT_HYBRID && ybit != BN_is_odd(y)) {
+                ECerror(EC_R_INVALID_ENCODING);
+                return 0;
+        }
+
+        return 1;
+}
+
 /* Nonzero y-bit only makes sense with compressed or hybrid encoding. */
 static int
 ec_oct_nonzero_ybit_allowed(uint8_t form)
@@ -437,12 +448,8 @@ ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
                         goto err;
                 if (!ec_oct_get_field_element_cbs(&cbs, group, y))
                         goto err;
-                if (form == EC_OCT_POINT_HYBRID) {
-                        if (ybit != BN_is_odd(y)) {
-                                ECerror(EC_R_INVALID_ENCODING);
-                                goto err;
-                        }
-                }
+                if (!ec_oct_check_hybrid_ybit_is_consistent(form, ybit, y))
+                        goto err;
                 if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
                         goto err;
         }