From e932d0c4e982d4c0835583cf4a13169ac99d004c Mon Sep 17 00:00:00 2001
From: Nadav Barak <nadav@fireblocks.com>
Date: Sun, 17 Nov 2024 18:03:37 +0200
Subject: [PATCH] Better checking for BN_CTX_get

---
 src/common/cosigner/mta.cpp                           | 11 +++++++++++
 .../crypto/GFp_curve_algebra/GFp_curve_algebra.c      |  2 +-
 src/common/crypto/commitments/ring_pedersen.c         |  3 ++-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/common/cosigner/mta.cpp b/src/common/cosigner/mta.cpp
index 9ecea35..fda85a4 100644
--- a/src/common/cosigner/mta.cpp
+++ b/src/common/cosigner/mta.cpp
@@ -818,6 +818,11 @@ void response_verifier::process_paillier(const BIGNUM* e, const BIGNUM* request,
     BIGNUM* B = BN_CTX_get(_ctx.get());
     BIGNUM* gamma = BN_CTX_get(_ctx.get());
     
+    if (!tmp1 || !tmp2 || !B || !gamma)
+    {
+        throw cosigner_exception(cosigner_exception::NO_MEM);
+    }
+
     if (is_coprime_fast(response, _my_paillier->pub.n, _ctx.get()) != 1)
     {
         LOG_ERROR("response is not a valid ciphertext");
@@ -953,6 +958,12 @@ void response_verifier::process_ring_pedersen(const BIGNUM* e, const mta_range_z
     BIGNUM* tmp1 = BN_CTX_get(_ctx.get());
     BIGNUM* tmp2 = BN_CTX_get(_ctx.get());
     uint8_t gamma[2 * sizeof(uint64_t)];
+
+    if (!tmp1 || !tmp2)
+    {
+        throw cosigner_exception(cosigner_exception::NO_MEM);
+    }
+    
     if (!RAND_bytes(gamma, 2 * sizeof(uint64_t)))
     {
         LOG_ERROR("Failed to get random number, error %lu", ERR_get_error());
diff --git a/src/common/crypto/GFp_curve_algebra/GFp_curve_algebra.c b/src/common/crypto/GFp_curve_algebra/GFp_curve_algebra.c
index ea30bc0..70a05a7 100644
--- a/src/common/crypto/GFp_curve_algebra/GFp_curve_algebra.c
+++ b/src/common/crypto/GFp_curve_algebra/GFp_curve_algebra.c
@@ -344,10 +344,10 @@ elliptic_curve_algebra_status GFp_curve_algebra_verify_linear_combination(const
     }
 
     zero = BN_CTX_get(bn_ctx);
-    BN_zero(zero);
     tmp = EC_POINT_new(ctx->curve);
     if (!zero || !tmp)
         goto cleanup;
+    BN_zero(zero);
     if (!EC_POINTs_mul(ctx->curve, tmp, zero, points_count, (const EC_POINT**)points, (const BIGNUM**)coeff, bn_ctx))
     {
         status = ELLIPTIC_CURVE_ALGEBRA_UNKNOWN_ERROR;
diff --git a/src/common/crypto/commitments/ring_pedersen.c b/src/common/crypto/commitments/ring_pedersen.c
index 67743df..8338e52 100644
--- a/src/common/crypto/commitments/ring_pedersen.c
+++ b/src/common/crypto/commitments/ring_pedersen.c
@@ -816,10 +816,11 @@ ring_pedersen_status ring_pedersen_verify_batch_commitments_internal(const ring_
     B = BN_CTX_get(ctx);
     tmp1 = BN_CTX_get(ctx);
     tmp2 = BN_CTX_get(ctx);
-    BN_one(B);
 
     if (!t_exp || !B || !tmp1 || !tmp2)
         goto cleanup;
+        
+    BN_one(B);
 
     ring_pedersen_init_mont(&priv->pub, ctx);
     status = RING_PEDERSEN_UNKNOWN_ERROR;