ecdh: add error codes for point at infinity/not on curve

The point at infinity would previously raise EC_R_POINT_AT_INFINITY via
EC_POINT_get_affine_coordinates(). For consistency, also raise an error
for off-curve points.

pointed out by/ok kenjiro

1 files changed, 7 insertions, 3 deletions

diff --git a/src/lib/libcrypto/ecdh/ecdh.c b/src/lib/libcrypto/ecdh/ecdh.c
index 51b409a5dd..218c584558 100644
--- a/src/lib/libcrypto/ecdh/ecdh.c
+++ b/src/lib/libcrypto/ecdh/ecdh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ecdh.c,v 1.14 2026/06/08 12:08:08 tb Exp $ */
+/* $OpenBSD: ecdh.c,v 1.15 2026/06/09 05:24:47 tb Exp $ */
 /* ====================================================================
  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
  *
@@ -169,11 +169,15 @@ ec_key_ecdh_compute_key(unsigned char **out, size_t *out_len,
         if ((group = EC_KEY_get0_group(ecdh)) == NULL)
                 goto err;
 
-        if (EC_POINT_is_at_infinity(group, pub_key))
+        if (EC_POINT_is_at_infinity(group, pub_key)) {
+                ECerror(EC_R_POINT_AT_INFINITY);
                 goto err;
+        }
 
-        if (EC_POINT_is_on_curve(group, pub_key, ctx) <= 0)
+        if (EC_POINT_is_on_curve(group, pub_key, ctx) <= 0) {
+                ECerror(EC_R_POINT_IS_NOT_ON_CURVE);
                 goto err;
+        }
 
         if ((point = EC_POINT_new(group)) == NULL) {
                 ECerror(ERR_R_MALLOC_FAILURE);