Reimplement GetPseudoDeviceId to be more accurate

Now returns a valid V5 UUID and uses the game's seed from control.nacp
for generation.

app/src/main/cpp/skyline/common/uuid.cpp

@@ -74,4 +74,18 @@ namespace skyline {
 
         return uuid.Swap();
     }
+
+    UUID UUID::GenerateUuidV5(const std::array<u8, 20> sha1) {
+        constexpr u8 reserved{0x1}; // RFC4122 variant
+        constexpr u8 version{0x5}; // v4 UUIDs are generated using SHA1 hashes
+
+        UuidLayout uuid;
+        std::memcpy(&uuid, sha1.data(), sizeof(UuidLayout));
+
+        // Set format bits
+        uuid.reserved = reserved;
+        uuid.version = version;
+
+        return uuid.Swap();
+    }
 }

app/src/main/cpp/skyline/common/uuid.h

@@ -15,6 +15,11 @@ namespace skyline {
          */
         static UUID GenerateUuidV4();
 
+        /**
+         * @brief Generates a version 5 UUID from the given SHA1
+         */
+        static UUID GenerateUuidV5(const std::array<u8, 20> sha1);
+
         /**
          * @brief Checks if a UUID is an invalid nil UUID
          */

app/src/main/cpp/skyline/services/am/controller/IApplicationFunctions.cpp

@@ -1,6 +1,9 @@
 // SPDX-License-Identifier: MPL-2.0
 // Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
 
+#include <common/uuid.h>
+#include <mbedtls/sha1.h>
+#include <loader/loader.h>
 #include <kernel/types/KProcess.h>
 #include <services/account/IAccountServiceForApplication.h>
 #include <services/am/storage/IStorage.h>
@@ -39,8 +42,15 @@ namespace skyline::service::am {
     }
 
     Result IApplicationFunctions::GetPseudoDeviceId(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response) {
-        response.Push<u64>(0L);
+        auto seedForPseudoDeviceId{state.loader->nacp->nacpContents.seedForPseudoDeviceId};
-        response.Push<u64>(0L);
+        std::array<u8, 20> hashBuf{};
+
+        // On HOS the seed from control.ncap is hashed together with the device specific device ID seed,
+        // for us it's enough to just hash the seed from control.nacp as it provides the same guarantees.
+        if (int err{mbedtls_sha1_ret(seedForPseudoDeviceId.data(), seedForPseudoDeviceId.size(), hashBuf.data())}; err < 0)
+            throw exception("Failed to hash device ID, err: {}", err);
+
+        response.Push<UUID>(UUID::GenerateUuidV5(hashBuf));
         return {};
     }
 

app/src/main/cpp/skyline/services/am/controller/IApplicationFunctions.h

@@ -43,7 +43,7 @@ namespace skyline::service::am {
         Result NotifyRunning(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response);
 
         /**
-         * @brief Returns a UUID, however what it refers to is currently unknown
+         * @brief Returns a V5 UUID generated from a seed in control.nacp and a device specific seed
          * @url https://switchbrew.org/wiki/Applet_Manager_services#GetPseudoDeviceId
          */
         Result GetPseudoDeviceId(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response);

app/src/main/cpp/skyline/vfs/nacp.h

@@ -26,7 +26,9 @@ namespace skyline::vfs {
             std::array<ApplicationTitle, 0x10> titleEntries; //!< Title entries for each language
             u8 _pad0_[0x78];
             u64 saveDataOwnerId; //!< The ID that should be used for this application's savedata
-            u8 _pad1_[0xF80];
+            u8 _pad1_[0x78];
+            std::array<u8, 8> seedForPseudoDeviceId; //!< Seed that is combined with the device seed for generating the pseudo-device ID
+            u8 _pad2_[0xF00];
         } nacpContents{};
         static_assert(sizeof(NacpData) == 0x4000);