From 7d339778135c44370199f5c84e8c90b3d60f6717 Mon Sep 17 00:00:00 2001
From: selsta <selsta@sent.at>
Date: Thu, 21 May 2026 22:47:02 +0200
Subject: net: canonicalize Tor and I2P hostnames

---
 src/net/host.h          | 20 ++++++++++++++++++++
 src/net/i2p_address.cpp |  7 +++++--
 src/net/tor_address.cpp |  7 +++++--
 3 files changed, 30 insertions(+), 4 deletions(-)
 create mode 100644 src/net/host.h

(limited to 'src')

diff --git a/src/net/host.h b/src/net/host.h
new file mode 100644
index 000000000..c96a7b434
--- /dev/null
+++ b/src/net/host.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <string>
+
+namespace net
+{
+    /*!
+    * \brief Canonicalize a hostname by converting letters to lowercase.
+    *
+    * \param host Hostname to canonicalize in-place.
+    */
+    inline void canonicalize_host(std::string& host) noexcept
+    {
+        for (char& c : host)
+        {
+            if ('A' <= c && c <= 'Z')
+                c = static_cast<char>(c - 'A' + 'a');
+        }
+    }
+}
diff --git a/src/net/i2p_address.cpp b/src/net/i2p_address.cpp
index 4e21085d0..e793048c0 100644
--- a/src/net/i2p_address.cpp
+++ b/src/net/i2p_address.cpp
@@ -36,6 +36,7 @@
 #include <limits>
 
 #include "net/error.h"
+#include "net/host.h"
 #include "serialization/keyvalue_serialization.h"
 #include "storages/portable_storage.h"
 #include "string_tools_lexical.h"
@@ -105,10 +106,12 @@ namespace net
     expect<i2p_address> i2p_address::make(const boost::string_ref address)
     {
         boost::string_ref host = address.substr(0, address.rfind(':'));
-        MONERO_CHECK(host_check(host));
+        std::string normalized_host{host};
+        net::canonicalize_host(normalized_host);
+        MONERO_CHECK(host_check(normalized_host));
 
         static_assert(b32_length + sizeof(tld) == sizeof(i2p_address::host_), "bad internal host size");
-        return i2p_address{host};
+        return i2p_address{normalized_host};
     }
 
     bool i2p_address::_load(epee::serialization::portable_storage& src, epee::serialization::section* hparent)
diff --git a/src/net/tor_address.cpp b/src/net/tor_address.cpp
index ac36dbffd..35bd8e9a2 100644
--- a/src/net/tor_address.cpp
+++ b/src/net/tor_address.cpp
@@ -37,6 +37,7 @@
 #include <limits>
 
 #include "net/error.h"
+#include "net/host.h"
 #include "serialization/keyvalue_serialization.h"
 #include "storages/portable_storage.h"
 #include "string_tools_lexical.h"
@@ -112,7 +113,9 @@ namespace net
         const boost::string_ref port =
             address.substr(host.size() + (host.size() == address.size() ? 0 : 1));
 
-        MONERO_CHECK(host_check(host));
+        std::string normalized_host{host};
+        net::canonicalize_host(normalized_host);
+        MONERO_CHECK(host_check(normalized_host));
 
         std::uint16_t porti = default_port;
         if (!port.empty() && !epee::string_tools::get_xtype_from_string(porti, std::string{port}))
@@ -120,7 +123,7 @@ namespace net
 
         static_assert(v2_length <= v3_length, "bad internal host size");
         static_assert(v3_length + sizeof(tld) == sizeof(tor_address::host_), "bad internal host size");
-        return tor_address{host, porti};
+        return tor_address{normalized_host, porti};
     }
 
     bool tor_address::_load(epee::serialization::portable_storage& src, epee::serialization::section* hparent)
-- 
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