Persist static key for Template Provider

Author: Sjors

src/node/sv2_template_provider.cpp

@@ -6,6 +6,7 @@
 #include <common/args.h>
 #include <common/sv2_noise.h>
 #include <logging.h>
+#include <util/readwritefile.h>
 #include <util/strencodings.h>
 #include <util/thread.h>
 #include <validation.h>
@@ -14,10 +15,46 @@ Sv2TemplateProvider::Sv2TemplateProvider(interfaces::Mining& mining) : m_mining{
 {
     // TODO: persist static key
     CKey static_key;
-    static_key.MakeNewKey(true);
-
-    auto authority_key{GenerateRandomKey()};
-
+    try {
+        AutoFile{fsbridge::fopen(GetStaticKeyFile(), "rb")} >> static_key;
+        LogPrintLevel(BCLog::SV2, BCLog::Level::Debug, "Reading cached static key from %s\n", fs::PathToString(GetStaticKeyFile()));
+    } catch (const std::ios_base::failure&) {
+        // File is not expected to exist the first time.
+        // In the unlikely event that loading an existing key fails, create a new one.
+    }
+    if (!static_key.IsValid()) {
+        static_key = GenerateRandomKey();
+        try {
+            AutoFile{fsbridge::fopen(GetStaticKeyFile(), "wb")} << static_key;
+        } catch (const std::ios_base::failure&) {
+            LogPrintLevel(BCLog::SV2, BCLog::Level::Error, "Error writing static key to %s\n", fs::PathToString(GetStaticKeyFile()));
+            // Continue, because this is not a critical failure.
+        }
+        LogPrintLevel(BCLog::SV2, BCLog::Level::Debug, "Generated static key, saved to %s\n", fs::PathToString(GetStaticKeyFile()));
+    }
+    LogPrintLevel(BCLog::SV2, BCLog::Level::Info, "Static key: %s\n", HexStr(static_key.GetPubKey()));
+
+   // Generate self signed certificate using (cached) authority key
+    // TODO: skip loading authoritity key if -sv2cert is used
+
+    // Load authority key if cached
+    CKey authority_key;
+    try {
+        AutoFile{fsbridge::fopen(GetAuthorityKeyFile(), "rb")} >> authority_key;
+    } catch (const std::ios_base::failure&) {
+        // File is not expected to exist the first time.
+        // In the unlikely event that loading an existing key fails, create a new one.
+    }
+    if (!authority_key.IsValid()) {
+        authority_key = GenerateRandomKey();
+        try {
+            AutoFile{fsbridge::fopen(GetAuthorityKeyFile(), "wb")} << authority_key;
+        } catch (const std::ios_base::failure&) {
+            LogPrintLevel(BCLog::SV2, BCLog::Level::Error, "Error writing authority key to %s\n", fs::PathToString(GetAuthorityKeyFile()));
+            // Continue, because this is not a critical failure.
+        }
+        LogPrintLevel(BCLog::SV2, BCLog::Level::Debug, "Generated authority key, saved to %s\n", fs::PathToString(GetAuthorityKeyFile()));
+    }
     // SRI uses base58 encoded x-only pubkeys in its configuration files
     std::array<unsigned char, 34> version_pubkey_bytes;
     version_pubkey_bytes[0] = 1;
@@ -35,11 +72,19 @@ Sv2TemplateProvider::Sv2TemplateProvider(interfaces::Mining& mining) : m_mining{
     uint32_t valid_to =  std::numeric_limits<unsigned int>::max(); // 2106
     Sv2SignatureNoiseMessage certificate = Sv2SignatureNoiseMessage(version, valid_from, valid_to, XOnlyPubKey(static_key.GetPubKey()), authority_key);
 
-    // TODO: persist certificate
-
     m_connman = std::make_unique<Sv2Connman>(TP_SUBPROTOCOL, static_key, m_authority_pubkey, certificate);
 }
 
+fs::path Sv2TemplateProvider::GetStaticKeyFile()
+{
+    return gArgs.GetDataDirNet() / "sv2_static_key";
+}
+
+fs::path Sv2TemplateProvider::GetAuthorityKeyFile()
+{
+    return gArgs.GetDataDirNet() / "sv2_authority_key";
+}
+
 bool Sv2TemplateProvider::Start(const Sv2TemplateProviderOptions& options)
 {
     m_options = options;

src/node/sv2_template_provider.h

@@ -59,6 +59,12 @@ class Sv2TemplateProvider : public Sv2EventsInterface
 
     std::unique_ptr<Sv2Connman> m_connman;
 
+    /** Get name of file to store static key */
+    fs::path GetStaticKeyFile();
+
+    /** Get name of file to store authority key */
+    fs::path GetAuthorityKeyFile();
+
     /**
     * Configuration
     */