From 438f7f9fc438c02504db34704c9fc7d015ca5b2e Mon Sep 17 00:00:00 2001
From: selsta <selsta@sent.at>
Date: Thu, 21 May 2026 22:47:02 +0200
Subject: [PATCH] net: canonicalize Tor and I2P hostnames

---
 src/net/host.h           | 20 ++++++++++++++++++++
 src/net/i2p_address.cpp  |  7 +++++--
 src/net/tor_address.cpp  |  7 +++++--
 tests/unit_tests/net.cpp | 20 ++++++++++++++++++++
 4 files changed, 50 insertions(+), 4 deletions(-)
 create mode 100644 src/net/host.h

diff --git a/src/net/host.h b/src/net/host.h
new file mode 100644
index 000000000..21bcff2ae
--- /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 (u8'A' <= c && c <= u8'Z')
+                c = static_cast<char>(c - u8'A' + u8'a');
+        }
+    }
+}
diff --git a/src/net/i2p_address.cpp b/src/net/i2p_address.cpp
index e21bc37e2..586432076 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 e9f1b7a97..103843e18 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"
@@ -111,14 +112,16 @@ 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}))
             return {net::error::invalid_port};
 
         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)
diff --git a/tests/unit_tests/net.cpp b/tests/unit_tests/net.cpp
index acb3b95bf..5c3d9ac9c 100644
--- a/tests/unit_tests/net.cpp
+++ b/tests/unit_tests/net.cpp
@@ -57,6 +57,7 @@
 #include "crypto/crypto.h"
 #include "net/dandelionpp.h"
 #include "net/error.h"
+#include "net/host.h"
 #include "net/i2p_address.h"
 #include "net/net_utils_base.h"
 #include "net/socks.h"
@@ -68,12 +69,21 @@
 #include "serialization/keyvalue_serialization.h"
 #include "storages/portable_storage.h"
 
+TEST(host, canonicalize_host)
+{
+    std::string host{"ABCdef123.ONION"};
+    net::canonicalize_host(host);
+    EXPECT_EQ("abcdef123.onion", host);
+}
+
 namespace
 {
     static constexpr const char v2_onion[] =
         "xmrto2bturnore26.onion";
     static constexpr const char v3_onion[] =
         "vww6ybal4bd7szmgncyruucpgfkqahzddi37ktceo3ah7ngmcopnpyyd.onion";
+    static constexpr const char v3_onion_upper[] =
+        "VWW6YBAL4BD7SZMGNCYRUUCPGFKQAHZDDI37KTCEO3AH7NGMCOPNPYYD.ONION";
     static constexpr const char v3_onion_2[] =
         "zpv4fa3szgel7vf6jdjeugizdclq2vzkelscs2bhbgnlldzzggcen3ad.onion";
 }
@@ -146,6 +156,10 @@ TEST(tor_address, valid)
     EXPECT_STREQ(v3_onion, address1->str().c_str());
     EXPECT_TRUE(address1->is_blockable());
 
+    const auto uppercase = net::tor_address::make(v3_onion_upper);
+    ASSERT_TRUE(uppercase.has_value());
+    EXPECT_EQ(*address1, *uppercase);
+
     net::tor_address address2{*address1};
 
     EXPECT_EQ(0u, address2.port());
@@ -448,6 +462,8 @@ namespace
 {
     static constexpr const char b32_i2p[] =
         "vww6ybal4bd7szmgncyruucpgfkqahzddi37ktceo3ah7ngmcopn.b32.i2p";
+    static constexpr const char b32_i2p_upper[] =
+        "VWW6YBAL4BD7SZMGNCYRUUCPGFKQAHZDDI37KTCEO3AH7NGMCOPN.B32.I2P";
     static constexpr const char b32_i2p_2[] =
         "xmrto2bturnore26xmrto2bturnore26xmrto2bturnore26xmr2.b32.i2p";
 }
@@ -516,6 +532,10 @@ TEST(i2p_address, valid)
     EXPECT_STREQ(b32_i2p, address1->str().c_str());
     EXPECT_TRUE(address1->is_blockable());
 
+    const auto uppercase = net::i2p_address::make(b32_i2p_upper);
+    ASSERT_TRUE(uppercase.has_value());
+    EXPECT_EQ(*address1, *uppercase);
+
     net::i2p_address address2{*address1};
 
     EXPECT_EQ(1u, address2.port());