[Python-checkins] [3.6] bpo-39401: Avoid unsafe DLL load on Windows 7 and earlier (GH-18231) (GH-18233)

[Steve Dower]

https://github.com/python/cpython/commit/51332c467ed2e07a191f903d554d0c54248e4d88
commit: 51332c467ed2e07a191f903d554d0c54248e4d88
branch: 3.6
author: Steve Dower <steve.dower at python.org>
committer: GitHub <noreply at github.com>
date: 2020-01-30T21:12:20-05:00
summary:

[3.6] bpo-39401: Avoid unsafe DLL load on Windows 7 and earlier (GH-18231) (GH-18233)

files:
A Misc/NEWS.d/next/Security/2020-01-28-20-54-09.bpo-39401.he7h_A.rst
M PC/getpathp.c
M Tools/msi/bundle/bootstrap/PythonBootstrapperApplication.cpp

diff --git a/Misc/NEWS.d/next/Security/2020-01-28-20-54-09.bpo-39401.he7h_A.rst b/Misc/NEWS.d/next/Security/2020-01-28-20-54-09.bpo-39401.he7h_A.rst
new file mode 100644
index 0000000000000..5071e126b70d0
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2020-01-28-20-54-09.bpo-39401.he7h_A.rst
@@ -0,0 +1 @@
+Avoid unsafe load of ``api-ms-win-core-path-l1-1-0.dll`` at startup on Windows 7.
diff --git a/PC/getpathp.c b/PC/getpathp.c
index 880ea7b966e5c..e86c376fb4d34 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -224,7 +224,8 @@ static void
 join(wchar_t *buffer, const wchar_t *stuff)
 {
     if (_PathCchCombineEx_Initialized == 0) {
-        HMODULE pathapi = LoadLibraryW(L"api-ms-win-core-path-l1-1-0.dll");
+        HMODULE pathapi = LoadLibraryExW(L"api-ms-win-core-path-l1-1-0.dll", NULL,
+                                         LOAD_LIBRARY_SEARCH_SYSTEM32);
         if (pathapi)
             _PathCchCombineEx = (PPathCchCombineEx)GetProcAddress(pathapi, "PathCchCombineEx");
         else
@@ -249,7 +250,8 @@ static PPathCchCanonicalizeEx _PathCchCanonicalizeEx;
 static void canonicalize(wchar_t *buffer, const wchar_t *path)
 {
     if (_PathCchCanonicalizeEx_Initialized == 0) {
-        HMODULE pathapi = LoadLibraryW(L"api-ms-win-core-path-l1-1-0.dll");
+        HMODULE pathapi = LoadLibraryExW(L"api-ms-win-core-path-l1-1-0.dll", NULL,
+                                         LOAD_LIBRARY_SEARCH_SYSTEM32);
         if (pathapi) {
             _PathCchCanonicalizeEx = (PPathCchCanonicalizeEx)GetProcAddress(pathapi, "PathCchCanonicalizeEx");
         }
diff --git a/Tools/msi/bundle/bootstrap/PythonBootstrapperApplication.cpp b/Tools/msi/bundle/bootstrap/PythonBootstrapperApplication.cpp
index e88981fc3abb4..d14aeff190470 100644
--- a/Tools/msi/bundle/bootstrap/PythonBootstrapperApplication.cpp
+++ b/Tools/msi/bundle/bootstrap/PythonBootstrapperApplication.cpp
@@ -3042,8 +3042,16 @@ class PythonBootstrapperApplication : public CBalBaseBootstrapperApplication {
             }
         } else {
             if (IsWindows7SP1OrGreater()) {
-                BalLog(BOOTSTRAPPER_LOG_LEVEL_STANDARD, "Target OS is Windows 7 SP1 or later");
-                return;
+                HMODULE hKernel32 = GetModuleHandleW(L"kernel32");
+                if (hKernel32 && !GetProcAddress(hKernel32, "AddDllDirectory")) {
+                    BalLog(BOOTSTRAPPER_LOG_LEVEL_ERROR, "Detected Windows 7 SP1 without KB2533623");
+                    BalLog(BOOTSTRAPPER_LOG_LEVEL_ERROR, "KB2533623 update is required to continue.");
+                    /* The "MissingSP1" error also specifies updates are required */
+                    LocGetString(_wixLoc, L"#(loc.FailureWin7MissingSP1)", &pLocString);
+                } else {
+                    BalLog(BOOTSTRAPPER_LOG_LEVEL_STANDARD, "Target OS is Windows 7 SP1 or later");
+                    return;
+                }
             } else if (IsWindows7OrGreater()) {
                 BalLog(BOOTSTRAPPER_LOG_LEVEL_ERROR, "Detected Windows 7 RTM");
                 BalLog(BOOTSTRAPPER_LOG_LEVEL_ERROR, "Service Pack 1 is required to continue installation");