Re: [PATCH 2/2] mpi:ec: Use mpi_new with NBITS, instead of mpi_alloc.

>From 07efee1de2dac1b2a6ce29698b2abec9dd1f6820 Mon Sep 17 00:00:00 2001
Message-ID: <07efee1de2dac1b2a6ce29698b2abec9dd1f6820.1771055590.git.gniibe@fsij.org>
In-Reply-To: <43b648f0465fb449471944a84bb40f45996f6de3.1771055590.git.gniibe@fsij.org>
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From: NIIBE Yutaka <[email protected]>
Date: Sat, 14 Feb 2026 16:49:05 +0900
Subject: [PATCH 3/3] cipher:ecc: Fix Weierstrass curve with PUBKEY_FLAG_PARAM.
To: [email protected]
MIME-Version: 1.0
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* cipher/ecc-curves.c (point_from_keyparam): Handle the case where
EC==NULL.
* cipher/ecc-misc.c (_gcry_ecc_sec_decodepoint): Care about
EC==NULL.

--

GnuPG-bug-id: 8094
Signed-off-by: NIIBE Yutaka <[email protected]>
---
 cipher/ecc-curves.c | 6 +++++-
 cipher/ecc-misc.c   | 4 ++--
 2 files changed, 7 insertions(+), 3 deletions(-)


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diff --git a/cipher/ecc-curves.c b/cipher/ecc-curves.c
index 5478e69d..08b374d5 100644
--- a/cipher/ecc-curves.c
+++ b/cipher/ecc-curves.c
@@ -991,7 +991,11 @@ point_from_keyparam (gcry_mpi_point_t *r_a,
       if (!a)
         return GPG_ERR_INV_OBJ;
 
-      point = mpi_point_new (ec->nbits);
+      /* NOTE: EC may be NULL, when it's for Weierstrass curve for
+       * parameter "g".  And it's OK for _gcry_mpi_ec_decode_point
+       * (and _gcry_ecc_sec_decodepoint) to be called with EC=NULL.
+       */
+      point = mpi_point_new (ec? ec->nbits: 0);
       rc = _gcry_mpi_ec_decode_point (point, a, ec);
       mpi_free (a);
       if (rc)
diff --git a/cipher/ecc-misc.c b/cipher/ecc-misc.c
index 40303ac4..615b0df2 100644
--- a/cipher/ecc-misc.c
+++ b/cipher/ecc-misc.c
@@ -176,7 +176,7 @@ _gcry_mpi_ec_ec2os (gcry_mpi_point_t point, mpi_ec_t ec)
    RESULT must have been initialized and is set on success to the
    point given by VALUE.  */
 gpg_err_code_t
-_gcry_ecc_sec_decodepoint  (gcry_mpi_t value, mpi_ec_t ec, mpi_point_t result)
+_gcry_ecc_sec_decodepoint (gcry_mpi_t value, mpi_ec_t ec, mpi_point_t result)
 {
   gpg_err_code_t rc;
   size_t n;
@@ -220,7 +220,7 @@ _gcry_ecc_sec_decodepoint  (gcry_mpi_t value, mpi_ec_t ec, mpi_point_t result)
       gcry_mpi_t p1_4;
       int y_bit = (*buf == 3);
 
-      if (!mpi_test_bit (ec->p, 1))
+      if (ec == NULL || !mpi_test_bit (ec->p, 1))
         {
           xfree (buf_memory);
           return GPG_ERR_NOT_IMPLEMENTED; /* No support for point compression.  */

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