From fcb6f13f442d6a3f27689a87e3ed2bb9b431a332 Mon Sep 17 00:00:00 2001
From: Antoine Poinsot <darosior@protonmail.com>
Date: Tue, 14 Feb 2023 10:31:32 +0100
Subject: [PATCH] pubkey: introduce a GetEvenCorrespondingCPubKey helper

We'll need to get a compressed key out of an x-only one in other places.
Avoid duplicating the code.
---
 src/pubkey.cpp            | 7 +++++++
 src/pubkey.h              | 2 ++
 src/script/descriptor.cpp | 4 +---
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/pubkey.cpp b/src/pubkey.cpp
index 05808e4c227..11e1b4abb51 100644
--- a/src/pubkey.cpp
+++ b/src/pubkey.cpp
@@ -204,6 +204,13 @@ std::vector<CKeyID> XOnlyPubKey::GetKeyIDs() const
     return out;
 }
 
+CPubKey XOnlyPubKey::GetEvenCorrespondingCPubKey() const
+{
+    unsigned char full_key[CPubKey::COMPRESSED_SIZE] = {0x02};
+    std::copy(begin(), end(), full_key + 1);
+    return CPubKey{full_key};
+}
+
 bool XOnlyPubKey::IsFullyValid() const
 {
     secp256k1_xonly_pubkey pubkey;
diff --git a/src/pubkey.h b/src/pubkey.h
index 4b34fd829bc..2b655c3f73b 100644
--- a/src/pubkey.h
+++ b/src/pubkey.h
@@ -282,6 +282,8 @@ public:
      */
     std::vector<CKeyID> GetKeyIDs() const;
 
+    CPubKey GetEvenCorrespondingCPubKey() const;
+
     const unsigned char& operator[](int pos) const { return *(m_keydata.begin() + pos); }
     const unsigned char* data() const { return m_keydata.begin(); }
     static constexpr size_t size() { return decltype(m_keydata)::size(); }
diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index eaef481c51b..22177504fc1 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -1401,9 +1401,7 @@ std::unique_ptr<PubkeyProvider> InferPubkey(const CPubKey& pubkey, ParseScriptCo
 
 std::unique_ptr<PubkeyProvider> InferXOnlyPubkey(const XOnlyPubKey& xkey, ParseScriptContext ctx, const SigningProvider& provider)
 {
-    unsigned char full_key[CPubKey::COMPRESSED_SIZE] = {0x02};
-    std::copy(xkey.begin(), xkey.end(), full_key + 1);
-    CPubKey pubkey(full_key);
+    CPubKey pubkey{xkey.GetEvenCorrespondingCPubKey()};
     std::unique_ptr<PubkeyProvider> key_provider = std::make_unique<ConstPubkeyProvider>(0, pubkey, true);
     KeyOriginInfo info;
     if (provider.GetKeyOriginByXOnly(xkey, info)) {