From 20a95cb2d816bc641d95d2d9b5be46d574de47d5 Mon Sep 17 00:00:00 2001
From: obscuren <obscuren@obscura.com>
Date: Tue, 20 Jan 2015 14:39:26 +0100
Subject: [PATCH] handle point at infinity

---
 secp256k1/src/impl/ecdsa.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/secp256k1/src/impl/ecdsa.h b/secp256k1/src/impl/ecdsa.h
index b001e26..dd26cfd 100644
--- a/secp256k1/src/impl/ecdsa.h
+++ b/secp256k1/src/impl/ecdsa.h
@@ -149,6 +149,8 @@ int static secp256k1_ecdsa_sig_recover(const secp256k1_ecdsa_sig_t *sig, secp256
     secp256k1_num_mod_mul(&u2, &rn, &sig->s, &c->order);
     secp256k1_gej_t qj;
     secp256k1_ecmult(&qj, &xj, &u2, &u1);
+    if (secp256k1_gej_is_infinity(&qj))
+        return 0;
     secp256k1_ge_set_gej(pubkey, &qj);
     secp256k1_num_free(&rn);
     secp256k1_num_free(&u1);