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bpo-39401: Avoid unsafe DLL load on Windows 7 and earlier #18231

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merged 2 commits into from
Jan 29, 2020
Merged

bpo-39401: Avoid unsafe DLL load on Windows 7 and earlier #18231

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5ed9ebc
bpo-39401: Avoid unsafe DLL load on Windows 7 and earlier
zooba Jan 28, 2020
4b0a3bc
Replace dynamic load with static import
zooba Jan 28, 2020
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Security/2020-01-28-20-54-09.bpo-39401.he7h_A.rst
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@@ -0,0 +1 @@
Avoid unsafe DLL load at startup on Windows 7 and earlier.
55 changes: 5 additions & 50 deletions PC/getpathp.c
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Expand Up @@ -91,6 +91,7 @@
#endif

#include <windows.h>
#include <pathcch.h>
#include <shlwapi.h>

#ifdef HAVE_SYS_TYPES_H
Expand Down Expand Up @@ -242,42 +243,14 @@ ismodule(wchar_t *filename, int update_filename)
stuff as fits will be appended.
*/

static int _PathCchCombineEx_Initialized = 0;
typedef HRESULT(__stdcall *PPathCchCombineEx) (PWSTR pszPathOut, size_t cchPathOut,
PCWSTR pszPathIn, PCWSTR pszMore,
unsigned long dwFlags);
static PPathCchCombineEx _PathCchCombineEx;

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");
if (pathapi) {
_PathCchCombineEx = (PPathCchCombineEx)GetProcAddress(pathapi, "PathCchCombineEx");
}
else {
_PathCchCombineEx = NULL;
}
_PathCchCombineEx_Initialized = 1;
}

if (_PathCchCombineEx) {
if (FAILED(_PathCchCombineEx(buffer, MAXPATHLEN+1, buffer, stuff, 0))) {
Py_FatalError("buffer overflow in getpathp.c's join()");
}
} else {
if (!PathCombineW(buffer, buffer, stuff)) {
Py_FatalError("buffer overflow in getpathp.c's join()");
}
if (FAILED(PathCchCombineEx(buffer, MAXPATHLEN+1, buffer, stuff, 0))) {
Py_FatalError("buffer overflow in getpathp.c's join()");
}
}

static int _PathCchCanonicalizeEx_Initialized = 0;
typedef HRESULT(__stdcall *PPathCchCanonicalizeEx) (PWSTR pszPathOut, size_t cchPathOut,
PCWSTR pszPathIn, unsigned long dwFlags);
static PPathCchCanonicalizeEx _PathCchCanonicalizeEx;

/* Call PathCchCanonicalizeEx(path): remove navigation elements such as "."
and ".." to produce a direct, well-formed path. */
static PyStatus
Expand All @@ -287,26 +260,8 @@ canonicalize(wchar_t *buffer, const wchar_t *path)
return _PyStatus_NO_MEMORY();
}

if (_PathCchCanonicalizeEx_Initialized == 0) {
HMODULE pathapi = LoadLibraryW(L"api-ms-win-core-path-l1-1-0.dll");
if (pathapi) {
_PathCchCanonicalizeEx = (PPathCchCanonicalizeEx)GetProcAddress(pathapi, "PathCchCanonicalizeEx");
}
else {
_PathCchCanonicalizeEx = NULL;
}
_PathCchCanonicalizeEx_Initialized = 1;
}

if (_PathCchCanonicalizeEx) {
if (FAILED(_PathCchCanonicalizeEx(buffer, MAXPATHLEN + 1, path, 0))) {
return INIT_ERR_BUFFER_OVERFLOW();
}
}
else {
if (!PathCanonicalizeW(buffer, path)) {
return INIT_ERR_BUFFER_OVERFLOW();
}
if (FAILED(PathCchCanonicalizeEx(buffer, MAXPATHLEN + 1, path, 0))) {
return INIT_ERR_BUFFER_OVERFLOW();
}
return _PyStatus_OK();
}
Expand Down
2 changes: 1 addition & 1 deletion PCbuild/pythoncore.vcxproj
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Expand Up @@ -106,7 +106,7 @@
<PreprocessorDefinitions Condition="$(IncludeExternals)">_Py_HAVE_ZLIB;%(PreprocessorDefinitions)</PreprocessorDefinitions>
</ClCompile>
<Link>
<AdditionalDependencies>version.lib;shlwapi.lib;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
<AdditionalDependencies>version.lib;shlwapi.lib;ws2_32.lib;pathcch.lib;%(AdditionalDependencies)</AdditionalDependencies>
</Link>
</ItemDefinitionGroup>
<ItemGroup>
Expand Down