[Pkg-bitcoin-commits] [libsecp256k1] 09/22: Restructure nonce clearing

[Jonas Smedegaard]

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js pushed a commit to branch master
in repository libsecp256k1.

commit 0f9e69db555ea35b90f49fa48925c366261452ec
Author: bgorlick <ben at bengorlick.com>
Date:   Fri Oct 21 03:50:10 2016 -0700

    Restructure nonce clearing
    
    Make sure we clear the nonce data even if the nonce function fails (it may have written partial data), and call memset only once in the case we iterate to produce a valid signature.
---
 src/modules/schnorr/main_impl.h | 4 ++--
 src/secp256k1.c                 | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/modules/schnorr/main_impl.h b/src/modules/schnorr/main_impl.h
old mode 100644
new mode 100755
index fa176a1..c88a7ea
--- a/src/modules/schnorr/main_impl.h
+++ b/src/modules/schnorr/main_impl.h
@@ -24,6 +24,7 @@ int secp256k1_schnorr_sign(const secp256k1_context* ctx, unsigned char *sig64, c
     secp256k1_scalar sec, non;
     int ret = 0;
     int overflow = 0;
+    unsigned char nonce32[32];
     unsigned int count = 0;
     VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
@@ -36,13 +37,11 @@ int secp256k1_schnorr_sign(const secp256k1_context* ctx, unsigned char *sig64, c
 
     secp256k1_scalar_set_b32(&sec, seckey, NULL);
     while (1) {
-        unsigned char nonce32[32];
         ret = noncefp(nonce32, msg32, seckey, secp256k1_schnorr_algo16, (void*)noncedata, count);
         if (!ret) {
             break;
         }
         secp256k1_scalar_set_b32(&non, nonce32, &overflow);
-        memset(nonce32, 0, 32);
         if (!secp256k1_scalar_is_zero(&non) && !overflow) {
             if (secp256k1_schnorr_sig_sign(&ctx->ecmult_gen_ctx, sig64, &sec, &non, NULL, secp256k1_schnorr_msghash_sha256, msg32)) {
                 break;
@@ -53,6 +52,7 @@ int secp256k1_schnorr_sign(const secp256k1_context* ctx, unsigned char *sig64, c
     if (!ret) {
         memset(sig64, 0, 64);
     }
+    memset(nonce32, 0, 32);
     secp256k1_scalar_clear(&non);
     secp256k1_scalar_clear(&sec);
     return ret;
diff --git a/src/secp256k1.c b/src/secp256k1.c
old mode 100644
new mode 100755
index 7973d60..fb8b882
--- a/src/secp256k1.c
+++ b/src/secp256k1.c
@@ -359,16 +359,15 @@ int secp256k1_ecdsa_sign(const secp256k1_context* ctx, secp256k1_ecdsa_signature
     secp256k1_scalar_set_b32(&sec, seckey, &overflow);
     /* Fail if the secret key is invalid. */
     if (!overflow && !secp256k1_scalar_is_zero(&sec)) {
+        unsigned char nonce32[32];
         unsigned int count = 0;
         secp256k1_scalar_set_b32(&msg, msg32, NULL);
         while (1) {
-            unsigned char nonce32[32];
             ret = noncefp(nonce32, msg32, seckey, NULL, (void*)noncedata, count);
             if (!ret) {
                 break;
             }
             secp256k1_scalar_set_b32(&non, nonce32, &overflow);
-            memset(nonce32, 0, 32);
             if (!overflow && !secp256k1_scalar_is_zero(&non)) {
                 if (secp256k1_ecdsa_sig_sign(&ctx->ecmult_gen_ctx, &r, &s, &sec, &msg, &non, NULL)) {
                     break;
@@ -376,6 +375,7 @@ int secp256k1_ecdsa_sign(const secp256k1_context* ctx, secp256k1_ecdsa_signature
             }
             count++;
         }
+        memset(nonce32, 0, 32);
         secp256k1_scalar_clear(&msg);
         secp256k1_scalar_clear(&non);
         secp256k1_scalar_clear(&sec);

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