dns.mitm: parse redirections from hosts file

config_templates/system_settings.ini

@@ -42,6 +42,13 @@
 ; enabled or disabled.
 ; 0 = Disabled (not debug mode), 1 = Enabled (debug mode)
 ; enable_am_debug_mode = u8!0x0
+; Controls whether dns.mitm is enabled
+; 0 = Disabled, 1 = Enabled
+; atmosphere!enable_dns_mitm = u8!0x1
+; Controls whether dns.mitm uses the default redirections in addition to
+; whatever is specified in the user's hosts file.
+; 0 = Disabled (use hosts file contents), 1 = Enabled (use defaults and hosts file contents)
+; atmosphere!add_defaults_to_dns_hosts = u8!0x0
 [hbloader]
 ; Controls the size of the homebrew heap when running as applet.
 ; If set to zero, all available applet memory is used as heap.

libraries/libstratosphere/include/stratosphere/ams/ams_emummc_api.hpp

@@ -22,6 +22,9 @@ namespace ams::emummc {
     /* Get whether emummc is active. */
     bool IsActive();
 
+    /* Get the active emummc id. */
+    u32 GetActiveId();
+
     /* Get Nintendo redirection path. */
     const char *GetNintendoDirPath();
 

libraries/libstratosphere/source/ams/ams_emummc_api.cpp

@@ -57,10 +57,10 @@ namespace ams::emummc {
         };
 
         /* Globals. */
-        os::Mutex g_lock(false);
+        constinit os::SdkMutex g_lock;
-        ExosphereConfig g_exo_config;
+        constinit ExosphereConfig g_exo_config;
-        bool g_is_emummc;
+        constinit bool g_is_emummc;
-        bool g_has_cached;
+        constinit bool g_has_cached;
 
         /* Helpers. */
         void CacheValues() {
@@ -110,6 +110,12 @@ namespace ams::emummc {
         return g_is_emummc;
     }
 
+    /* Get the active emummc id. */
+    u32 GetActiveId() {
+        CacheValues();
+        return g_exo_config.base_cfg.id;
+    }
+
     /* Get Nintendo redirection path. */
     const char *GetNintendoDirPath() {
         CacheValues();

stratosphere/ams_mitm/source/amsmitm_fs_utils.cpp

@@ -47,6 +47,36 @@ namespace ams::mitm::fs {
         return fsFsCreateFile(&g_sd_filesystem, path, size, option);
     }
 
+    Result DeleteSdFile(const char *path) {
+        R_TRY(EnsureSdInitialized());
+        return fsFsDeleteFile(&g_sd_filesystem, path);
+    }
+
+    bool HasSdFile(const char *path) {
+        if (R_FAILED(EnsureSdInitialized())) {
+            return false;
+        }
+
+        FsDirEntryType type;
+        if (R_FAILED(fsFsGetEntryType(&g_sd_filesystem, path, &type))) {
+            return false;
+        }
+
+        return type == FsDirEntryType_File;
+    }
+
+    bool HasAtmosphereSdFile(const char *path) {
+        char fixed_path[ams::fs::EntryNameLengthMax + 1];
+        FormatAtmosphereSdPath(fixed_path, sizeof(fixed_path), path);
+        return HasSdFile(fixed_path);
+    }
+
+    Result DeleteAtmosphereSdFile(const char *path) {
+        char fixed_path[ams::fs::EntryNameLengthMax + 1];
+        FormatAtmosphereSdPath(fixed_path, sizeof(fixed_path), path);
+        return DeleteSdFile(fixed_path);
+    }
+
     Result CreateAtmosphereSdFile(const char *path, s64 size, s32 option) {
         char fixed_path[ams::fs::EntryNameLengthMax + 1];
         FormatAtmosphereSdPath(fixed_path, sizeof(fixed_path), path);

stratosphere/ams_mitm/source/amsmitm_fs_utils.hpp

@@ -22,6 +22,7 @@ namespace ams::mitm::fs {
     void OpenGlobalSdCardFileSystem();
 
     /* Utilities. */
+    Result DeleteAtmosphereSdFile(const char *path);
     Result CreateSdFile(const char *path, s64 size, s32 option);
     Result CreateAtmosphereSdFile(const char *path, s64 size, s32 option);
     Result OpenSdFile(FsFile *out, const char *path, u32 mode);
@@ -30,6 +31,9 @@ namespace ams::mitm::fs {
     Result OpenAtmosphereSdRomfsFile(FsFile *out, ncm::ProgramId program_id, const char *path, u32 mode);
     Result OpenAtmosphereRomfsFile(FsFile *out, ncm::ProgramId program_id, const char *path, u32 mode, FsFileSystem *fs);
 
+    bool HasSdFile(const char *path);
+    bool HasAtmosphereSdFile(const char *path);
+
     Result CreateSdDirectory(const char *path);
     Result CreateAtmosphereSdDirectory(const char *path);
     Result OpenSdDirectory(FsDir *out, const char *path, u32 mode);

stratosphere/ams_mitm/source/dns_mitm/dnsmitm_host_redirection.cpp

@@ -17,15 +17,298 @@
 #include "../amsmitm_fs_utils.hpp"
 #include "dnsmitm_debug.hpp"
 #include "dnsmitm_host_redirection.hpp"
+#include "socket_allocator.hpp"
 
 namespace ams::mitm::socket::resolver {
 
+    namespace {
+
+        constexpr const char DefaultHostsFile[] =
+            "# Nintendo telemetry servers\n"
+            "127.0.0.1 receive-lp1.dg.srv.nintendo.net\n"
+            "127.0.0.1 receive-lp1.er.srv.nintendo.net\n";
+
+        constinit os::SdkMutex g_redirection_lock;
+        std::unordered_map<std::string, ams::socket::InAddrT> g_redirection_map;
+
+        constinit char g_specific_emummc_hosts_path[0x40] = {};
+
+        void ParseHostsFile(const char *file_data) {
+            enum class State {
+                IgnoredLine,
+                BeginLine,
+                Ip1,
+                IpDot1,
+                Ip2,
+                IpDot2,
+                Ip3,
+                IpDot3,
+                Ip4,
+                WhiteSpace,
+                HostName,
+            };
+
+            ams::socket::InAddrT current_address;
+            char current_hostname[0x200];
+            u32 work;
+
+            State state = State::BeginLine;
+            for (const char *cur = file_data; *cur != '\x00'; ++cur) {
+                const char c = *cur;
+                switch (state) {
+                    case State::IgnoredLine:
+                        if (c == '\n') {
+                            state = State::BeginLine;
+                        }
+                        break;
+                    case State::BeginLine:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            current_address = 0;
+                            work            = static_cast<u32>(c - '0');
+                            state           = State::Ip1;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::Ip1:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work *= 10;
+                            work += static_cast<u32>(c - '0');
+                        } else if (c == '.') {
+                            current_address |= (work & 0xFF) << 0;
+                            work = 0;
+                            state = State::IpDot1;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::IpDot1:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work            = static_cast<u32>(c - '0');
+                            state           = State::Ip2;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::Ip2:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work *= 10;
+                            work += static_cast<u32>(c - '0');
+                        } else if (c == '.') {
+                            current_address |= (work & 0xFF) << 8;
+                            work = 0;
+                            state = State::IpDot2;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::IpDot2:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work            = static_cast<u32>(c - '0');
+                            state           = State::Ip3;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::Ip3:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work *= 10;
+                            work += static_cast<u32>(c - '0');
+                        } else if (c == '.') {
+                            current_address |= (work & 0xFF) << 16;
+                            work = 0;
+                            state = State::IpDot3;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::IpDot3:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work            = static_cast<u32>(c - '0');
+                            state           = State::Ip4;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::Ip4:
+                        if (std::isdigit(static_cast<unsigned char>(c))) {
+                            work *= 10;
+                            work += static_cast<u32>(c - '0');
+                        } else if (c == ' ' || c == '\t') {
+                            current_address |= (work & 0xFF) << 24;
+                            work = 0;
+                            state = State::WhiteSpace;
+                        } else {
+                            state = State::IgnoredLine;
+                        }
+                        break;
+                    case State::WhiteSpace:
+                        if (c == '\n') {
+                            state = State::BeginLine;
+                        } else if (c != ' ' && c != '\r' && c != '\t') {
+                            current_hostname[0] = c;
+                            work = 1;
+                            state = State::HostName;
+                        }
+                        break;
+                    case State::HostName:
+                        if (c == ' ' || c == '\r' || c == '\n' || c == '\t') {
+                            AMS_ABORT_UNLESS(work < sizeof(current_hostname));
+                            current_hostname[work] = '\x00';
+
+                            g_redirection_map[static_cast<const char *>(current_hostname)] = current_address;
+
+                            if (c == '\n') {
+                                state = State::BeginLine;
+                            } else {
+                                state = State::WhiteSpace;
+                            }
+                        } else {
+                            AMS_ABORT_UNLESS(work < sizeof(current_hostname) - 1);
+                            current_hostname[work++] = c;
+                        }
+                }
+            }
+
+            if (state == State::HostName) {
+                AMS_ABORT_UNLESS(work < sizeof(current_hostname));
+                current_hostname[work] = '\x00';
+
+                g_redirection_map[static_cast<const char *>(current_hostname)] = current_address;
+            }
+        }
+
+        void Log(::FsFile &f, const char *fmt, ...) __attribute__((format(printf, 2, 3)));
+        void Log(::FsFile &f, const char *fmt, ...) {
+            char log_buf[0x100];
+            int len = 0;
+            {
+                std::va_list vl;
+                va_start(vl, fmt);
+                len = util::VSNPrintf(log_buf, sizeof(log_buf), fmt, vl);
+                va_end(vl);
+            }
+
+            s64 ofs;
+            R_ABORT_UNLESS(::fsFileGetSize(std::addressof(f), std::addressof(ofs)));
+            R_ABORT_UNLESS(::fsFileWrite(std::addressof(f), ofs, log_buf, len, FsWriteOption_Flush));
+        }
+
+        const char *SelectHostsFile(::FsFile &log_file) {
+            Log(log_file, "Selecting hosts file...\n");
+            const bool is_emummc = emummc::IsActive();
+            const u32 emummc_id  = emummc::GetActiveId();
+            util::SNPrintf(g_specific_emummc_hosts_path, sizeof(g_specific_emummc_hosts_path), "/hosts/emummc_%04x", emummc_id);
+
+            if (is_emummc) {
+                if (mitm::fs::HasAtmosphereSdFile(g_specific_emummc_hosts_path)) {
+                    return g_specific_emummc_hosts_path;
+                }
+                Log(log_file, "Skipping %s because it does not exist...\n", g_specific_emummc_hosts_path);
+
+                if (mitm::fs::HasAtmosphereSdFile("/hosts/emummc")) {
+                    return "/hosts/emummc";
+                }
+                Log(log_file, "Skipping %s because it does not exist...\n", "/hosts/emummc");
+            } else {
+                if (mitm::fs::HasAtmosphereSdFile("/hosts/sysmmc")) {
+                    return "/hosts/sysmmc";
+                }
+                Log(log_file, "Skipping %s because it does not exist...\n", "/hosts/sysmmc");
+            }
+
+            return "/hosts/default";
+        }
+
+    }
+
+    void InitializeResolverRedirections(bool add_defaults) {
+        /* Acquire exclusive access to the map. */
+        std::scoped_lock lk(g_redirection_lock);
+
+        /* Clear the redirections map. */
+        g_redirection_map.clear();
+
+        /* Open log file. */
+        ::FsFile log_file;
+        mitm::fs::DeleteAtmosphereSdFile("/dns_mitm_startup.log");
+        R_ABORT_UNLESS(mitm::fs::CreateAtmosphereSdFile("/dns_mitm_startup.log", 0, ams::fs::CreateOption_None));
+        R_ABORT_UNLESS(mitm::fs::OpenAtmosphereSdFile(std::addressof(log_file), "/dns_mitm_startup.log", ams::fs::OpenMode_ReadWrite | ams::fs::OpenMode_AllowAppend));
+        ON_SCOPE_EXIT { ::fsFileClose(std::addressof(log_file)); };
+
+        Log(log_file, "DNS Mitm:\n");
+
+        /* If a default hosts file doesn't exist on the sd card, create one. */
+        if (!mitm::fs::HasAtmosphereSdFile("/hosts/default")) {
+            Log(log_file, "Creating /hosts/default because it does not exist.\n");
+
+            mitm::fs::CreateAtmosphereSdDirectory("/hosts");
+            R_ABORT_UNLESS(mitm::fs::CreateAtmosphereSdFile("/hosts/default", sizeof(DefaultHostsFile) - 1, ams::fs::CreateOption_None));
+
+            ::FsFile default_file;
+            R_ABORT_UNLESS(mitm::fs::OpenAtmosphereSdFile(std::addressof(default_file), "/hosts/default", ams::fs::OpenMode_ReadWrite));
+            R_ABORT_UNLESS(::fsFileWrite(std::addressof(default_file), 0, DefaultHostsFile, sizeof(DefaultHostsFile) - 1, ::FsWriteOption_Flush));
+            ::fsFileClose(std::addressof(default_file));
+        }
+
+        /* If we should, add the defaults. */
+        if (add_defaults) {
+            Log(log_file, "Adding defaults to redirection list.\n");
+            ParseHostsFile(DefaultHostsFile);
+        }
+
+        /* Select the hosts file. */
+        const char *hosts_path = SelectHostsFile(log_file);
+        Log(log_file, "Selected %s\n", hosts_path);
+
+        /* Load the hosts file. */
+        {
+            char *hosts_file_data = nullptr;
+            ON_SCOPE_EXIT { if (hosts_file_data != nullptr) { ams::Free(hosts_file_data); } };
+            {
+                ::FsFile hosts_file;
+                R_ABORT_UNLESS(mitm::fs::OpenAtmosphereSdFile(std::addressof(hosts_file), hosts_path, ams::fs::OpenMode_Read));
+                ON_SCOPE_EXIT { ::fsFileClose(std::addressof(hosts_file)); };
+
+                /* Get the hosts file size. */
+                s64 hosts_size;
+                R_ABORT_UNLESS(::fsFileGetSize(std::addressof(hosts_file), std::addressof(hosts_size)));
+
+                /* Validate we can read the file. */
+                AMS_ABORT_UNLESS(0 <= hosts_size && hosts_size < 0x8000);
+
+                /* Read the data. */
+                hosts_file_data = static_cast<char *>(ams::Malloc(0x8000));
+                AMS_ABORT_UNLESS(hosts_file_data != nullptr);
+
+                u64 br;
+                R_ABORT_UNLESS(::fsFileRead(std::addressof(hosts_file), 0, hosts_file_data, hosts_size, ::FsReadOption_None, std::addressof(br)));
+                AMS_ABORT_UNLESS(br == static_cast<u64>(hosts_size));
+
+                /* Null-terminate. */
+                hosts_file_data[hosts_size] = '\x00';
+            }
+
+            /* Parse the hosts file. */
+            ParseHostsFile(hosts_file_data);
+        }
+
+        /* Print the redirections. */
+        Log(log_file, "Redirections:\n");
+        for (const auto &[host, address] : g_redirection_map) {
+            Log(log_file, "    `%s` -> %u.%u.%u.%u\n", host.c_str(), (address >> 0) & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF, (address >> 24) & 0xFF);
+        }
+    }
+
     bool GetRedirectedHostByName(ams::socket::InAddrT *out, const char *hostname) {
-        /* TODO: Real implementation */
+        std::scoped_lock lk(g_redirection_lock);
-        if (std::strcmp(hostname, "receive-lp1.dg.srv.nintendo.net") == 0) {
+
-            *out = ams::socket::InAddr_Loopback;
+        for (const auto &[host, address] : g_redirection_map) {
+            if (std::strcmp(host.c_str(), hostname) == 0) {
+                *out = address;
                 return true;
             }
+        }
 
         return false;
     }

stratosphere/ams_mitm/source/dns_mitm/dnsmitm_host_redirection.hpp

@@ -18,6 +18,8 @@
 
 namespace ams::mitm::socket::resolver {
 
+    void InitializeResolverRedirections(bool add_defaults);
+
     bool GetRedirectedHostByName(ams::socket::InAddrT *out, const char *hostname);
 
 }

stratosphere/ams_mitm/source/dns_mitm/dnsmitm_module.cpp

@@ -16,8 +16,9 @@
 #include <stratosphere.hpp>
 #include "../amsmitm_initialization.hpp"
 #include "dnsmitm_module.hpp"
-#include "dnsmitm_resolver_impl.hpp"
 #include "dnsmitm_debug.hpp"
+#include "dnsmitm_resolver_impl.hpp"
+#include "dnsmitm_host_redirection.hpp"
 
 namespace ams::mitm::socket::resolver {
 
@@ -93,15 +94,39 @@ namespace ams::mitm::socket::resolver {
             }
         }
 
+        bool ShouldMitmDns() {
+            u8 en = 0;
+            if (settings::fwdbg::GetSettingsItemValue(std::addressof(en), sizeof(en), "atmosphere", "enable_dns_mitm") == sizeof(en)) {
+                return (en != 0);
+            }
+            return false;
+        }
+
+        bool ShouldAddDefaultResolverRedirections() {
+            u8 en = 0;
+            if (settings::fwdbg::GetSettingsItemValue(std::addressof(en), sizeof(en), "atmosphere", "add_defaults_to_dns_hosts") == sizeof(en)) {
+                return (en != 0);
+            }
+            return false;
+        }
+
     }
 
     void MitmModule::ThreadFunction(void *arg) {
         /* Wait until initialization is complete. */
         mitm::WaitInitialized();
 
+        /* If we shouldn't mitm dns, don't do anything at all. */
+        if (!ShouldMitmDns()) {
+            return;
+        }
+
         /* Initialize debug. */
         resolver::InitializeDebug();
 
+        /* Initialize redirection map. */
+        resolver::InitializeResolverRedirections(ShouldAddDefaultResolverRedirections());
+
         /* Create mitm servers. */
         R_ABORT_UNLESS((g_server_manager.RegisterMitmServer<ResolverImpl>(PortIndex_Mitm, DnsMitmServiceName)));
 

stratosphere/ams_mitm/source/set_mitm/settings_sd_kvs.cpp

@@ -349,6 +349,15 @@ namespace ams::settings::fwdbg {
             /* 0 = Disabled (not debug mode), 1 = Enabled (debug mode) */
             R_ABORT_UNLESS(ParseSettingsItemValue("atmosphere", "enable_am_debug_mode", "u8!0x0"));
 
+            /* Controls whether dns.mitm is enabled. */
+            /* 0 = Disabled, 1 = Enabled */
+            R_ABORT_UNLESS(ParseSettingsItemValue("atmosphere", "enable_dns_mitm", "u8!0x1"));
+
+            /* Controls whether dns.mitm uses the default redirections in addition to */
+            /* whatever is specified in the user's hosts file. */
+            /* 0 = Disabled (use hosts file contents), 1 = Enabled (use defaults and hosts file contents) */
+            R_ABORT_UNLESS(ParseSettingsItemValue("atmosphere", "add_defaults_to_dns_hosts", "u8!0x0"));
+
             /* Hbloader custom settings. */
 
             /* Controls the size of the homebrew heap when running as applet. */