Check launcher update signature

src/Startup.cpp

@@ -4,7 +4,6 @@
  SPDX-License-Identifier: AGPL-3.0-or-later
 */
 
-
 #include "zip_file.h"
 #include <charconv>
 #include <cstring>
@@ -14,9 +13,9 @@
 #if defined(_WIN32)
 #elif defined(__linux__)
 #include <unistd.h>
-#elif defined (__APPLE__)
+#elif defined(__APPLE__)
-#include <unistd.h>
 #include <libproc.h>
+#include <unistd.h>
 #endif // __APPLE__
 #include "Http.h"
 #include "Logger.h"
@@ -114,7 +113,7 @@ fs::path GetBP(const beammp_fs_char* P) {
     // should instead be placed in Application Support.
     proc_pidpath(pid, path, sizeof(path));
     fspath = std::string(path);
- #else
+#else
     fspath = beammp_fs_string(P);
 #endif
     fspath = fs::weakly_canonical(fspath.string() + "/..");
@@ -194,6 +193,143 @@ void CheckName() {
     }
 }
 
+#if defined(_WIN32)
+#include <wincrypt.h>
+#include <wintrust.h>
+#include <softpub.h>
+#include <iostream>
+
+#pragma comment(lib, "wintrust.lib")
+#pragma comment(lib, "crypt32.lib")
+
+bool CheckThumbprint(std::filesystem::path filepath)
+{
+    HCERTSTORE hStore = NULL;
+    HCRYPTMSG hMsg = NULL;
+
+    if (!CryptQueryObject(
+        CERT_QUERY_OBJECT_FILE,
+        filepath.wstring().c_str(),
+        CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
+        CERT_QUERY_FORMAT_FLAG_BINARY,
+        0,
+        NULL, NULL, NULL,
+        &hStore,
+        &hMsg,
+        NULL))
+    {
+        return false;
+    }
+
+    DWORD dwSignerInfo = 0;
+    if (!CryptMsgGetParam(hMsg, CMSG_SIGNER_INFO_PARAM, 0, NULL, &dwSignerInfo) || dwSignerInfo == 0)
+        return false;
+
+    PCMSG_SIGNER_INFO pSignerInfo = (PCMSG_SIGNER_INFO)LocalAlloc(LPTR, dwSignerInfo);
+    if (!CryptMsgGetParam(hMsg, CMSG_SIGNER_INFO_PARAM, 0, pSignerInfo, &dwSignerInfo))
+    {
+        LocalFree(pSignerInfo);
+        return false;
+    }
+
+    CERT_INFO certInfo = {};
+    certInfo.Issuer = pSignerInfo->Issuer;
+    certInfo.SerialNumber = pSignerInfo->SerialNumber;
+
+    PCCERT_CONTEXT pCertContext = CertFindCertificateInStore(
+        hStore,
+        X509_ASN_ENCODING | PKCS_7_ASN_ENCODING,
+        0,
+        CERT_FIND_SUBJECT_CERT,
+        &certInfo,
+        NULL);
+
+    if (!pCertContext)
+    {
+        LocalFree(pSignerInfo);
+        return false;
+    }
+
+    BYTE hash[64];
+    DWORD hashSize = sizeof(hash);
+
+    bool match = false;
+    if (CertGetCertificateContextProperty(pCertContext, CERT_SHA256_HASH_PROP_ID, hash, &hashSize))
+    {
+        std::string pubKeyData(
+            reinterpret_cast<const char*>(pCertContext->pCertInfo->SubjectPublicKeyInfo.PublicKey.pbData),
+            pCertContext->pCertInfo->SubjectPublicKeyInfo.PublicKey.cbData
+        );
+
+        std::string pubKeyHash = Utils::GetSha256HashReallyFast(pubKeyData, L"PubKey");
+        debug("pub key hash: " + pubKeyHash);
+
+        std::string fileThumbprint;
+        for (DWORD i = 0; i < hashSize; i++)
+        {
+            char buf[3];
+            sprintf_s(buf, "%02x", hash[i]);
+            fileThumbprint += buf;
+        }
+
+        debug("File thumbprint: " +fileThumbprint);
+        debug(filepath);
+
+        if (fileThumbprint == "937f055b713de69416926ed4651d65219a0a0e77d7a78c1932c007e14326da33" && pubKeyHash == "2afad4a5773b0ac449f48350ce0d09c372be0d5bcbaa6d01332ce000baffde99"){
+            match = true;
+        }
+    }
+
+    CertFreeCertificateContext(pCertContext);
+    CertCloseStore(hStore, 0);
+    LocalFree(pSignerInfo);
+
+    return match;
+}
+#include <windows.h>
+#include <wintrust.h>
+#include <Softpub.h>
+#include <filesystem>
+#include <string>
+
+#pragma comment(lib, "wintrust")
+
+bool VerifySignature(const std::filesystem::path& filePath)
+{
+    std::wstring path = filePath.wstring();
+
+    WINTRUST_FILE_INFO fileInfo = {};
+    fileInfo.cbStruct = sizeof(WINTRUST_FILE_INFO);
+    fileInfo.pcwszFilePath = path.c_str();
+    fileInfo.hFile = NULL;
+    fileInfo.pgKnownSubject = NULL;
+
+    WINTRUST_DATA winTrustData = {};
+    winTrustData.cbStruct = sizeof(WINTRUST_DATA);
+    winTrustData.dwUIChoice = WTD_UI_NONE;
+    winTrustData.dwUnionChoice = WTD_CHOICE_FILE;
+    winTrustData.pFile = &fileInfo;
+
+    winTrustData.dwStateAction = WTD_STATEACTION_VERIFY;
+
+    GUID policyGUID = WINTRUST_ACTION_GENERIC_VERIFY_V2;
+
+    LONG status = WinVerifyTrust(
+        NULL,
+        &policyGUID,
+        &winTrustData
+    );
+
+    debug(filePath);
+    debug("Signature check code: " + std::to_string(status));
+
+    winTrustData.dwStateAction = WTD_STATEACTION_CLOSE;
+    WinVerifyTrust(NULL, &policyGUID, &winTrustData);
+
+    return (status == CERT_E_UNTRUSTEDROOT);
+}
+#endif
+
 void CheckForUpdates(const std::string& CV) {
     std::string LatestHash = HTTP::Get("https://backend.beammp.com/sha/launcher?branch=" + Branch + "&pk=" + PublicKey);
     std::string LatestVersion = HTTP::Get(
@@ -211,11 +347,23 @@ void CheckForUpdates(const std::string& CV) {
             error("Auto update is NOT implemented for the Linux version. Please update manually ASAP as updates contain security patches.");
 #else
             info("Downloading Launcher update " + LatestHash);
+            std::wstring DownloadLocation = GetBP() / (beammp_wide("new_") + GetEN());
             if (HTTP::Download(
-                "https://backend.beammp.com/builds/launcher?download=true"
+                    "https://backend.beammp.com/builds/launcher?download=true"
-                "&pk="
+                    "&pk="
-                    + PublicKey + "&branch=" + Branch,
+                        + PublicKey + "&branch=" + Branch,
-                GetBP() / (beammp_wide("new_") + GetEN()), LatestHash)) {
+                    DownloadLocation, LatestHash)) {
+                if (!VerifySignature(DownloadLocation) || !CheckThumbprint(DownloadLocation)) {
+                    std::error_code ec;
+                    fs::remove(DownloadLocation, ec);
+                    if (ec) {
+                        error("Failed to remove broken launcher update");
+                    }
+                    throw std::runtime_error("The authenticity of the updated launcher could not be verified, it was corrupted or tampered with.");
+                }
+
+                info("Update signature is valid");
+
                 std::error_code ec;
                 fs::remove(Back, ec);
                 if (ec == std::errc::permission_denied) {
@@ -227,6 +375,13 @@ void CheckForUpdates(const std::string& CV) {
                 fs::rename(GetBP() / (beammp_wide("new_") + GetEN()), BP);
                 URelaunch();
             } else {
+                if (fs::exists(DownloadLocation)) {
+                    std::error_code error_code;
+                    fs::remove(DownloadLocation, error_code);
+                    if (error_code) {
+                        error("Failed to remove broken launcher update");
+                    }
+                }
                 throw std::runtime_error("Failed to download the launcher update! Please try manually updating it, https://docs.beammp.com/FAQ/Update-launcher/");
             }
 #endif
@@ -238,7 +393,6 @@ void CheckForUpdates(const std::string& CV) {
     TraceBack++;
 }
 
-
 #ifdef _WIN32
 void LinuxPatch() {
     HKEY hKey = nullptr;