[PATCH v6 1/6] wrapper: make inclusion of Windows csprng header tightly scoped

From: Neeraj Singh via GitGitGadget <gitgitgadget@gmail.com>
Date: Mar 10, 2022, 22:43 UTC
Message-ID: <825079b6aa14c3975254a336e0e313b963bc9ab4.1646952205.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1093.v6.git.1646952204.gitgitgadget@gmail.com>

From: Neeraj Singh <neerajsi@microsoft.com>

Including NTSecAPI.h in git-compat-util.h causes build errors in any other file that includes winternl.h. NTSecAPI.h was included in order to get access to the RtlGenRandom cryptographically secure PRNG. This change scopes the inclusion of ntsecapi.h to wrapper.c, which is the only place that it's actually needed.

The build breakage is due to the definition of UNICODE_STRING in
NtSecApi.h:
    #ifndef _NTDEF_
    typedef LSA_UNICODE_STRING UNICODE_STRING, *PUNICODE_STRING;
    typedef LSA_STRING STRING, *PSTRING ;
    #endif

LsaLookup.h:
    typedef struct _LSA_UNICODE_STRING {
        USHORT Length;
        USHORT MaximumLength;
    #ifdef MIDL_PASS
        [size_is(MaximumLength/2), length_is(Length/2)]
    #endif // MIDL_PASS
        PWSTR  Buffer;
    } LSA_UNICODE_STRING, *PLSA_UNICODE_STRING;

winternl.h also defines UNICODE_STRING:
    typedef struct _UNICODE_STRING {
        USHORT Length;
        USHORT MaximumLength;
        PWSTR  Buffer;
    } UNICODE_STRING;
    typedef UNICODE_STRING *PUNICODE_STRING;

Both definitions have equivalent layouts. Apparently these internal Windows headers aren't designed to be included together. This is an oversight in the headers and does not represent an incompatibility between the APIs.

Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
---
 compat/winansi.c  | 5 -----
 git-compat-util.h | 6 ------
 wrapper.c         | 7 +++++++
 3 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/compat/winansi.c b/compat/winansi.c
index 936a80a5f00..3abe8dd5a27 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c
@@ -4,11 +4,6 @@
 
 #undef NOGDI
 
-/*
- * Including the appropriate header file for RtlGenRandom causes MSVC to see a
- * redefinition of types in an incompatible way when including headers below.
- */
-#undef HAVE_RTLGENRANDOM
 #include "../git-compat-util.h"
 #include <wingdi.h>
 #include <winreg.h>
diff --git a/git-compat-util.h b/git-compat-util.h
index 876907b9df4..d210cff058c 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -197,12 +197,6 @@
 #endif
 #include <windows.h>
 #define GIT_WINDOWS_NATIVE
-#ifdef HAVE_RTLGENRANDOM
-/* This is required to get access to RtlGenRandom. */
-#define SystemFunction036 NTAPI SystemFunction036
-#include <NTSecAPI.h>
-#undef SystemFunction036
-#endif
 #endif
 
 #include <unistd.h>
diff --git a/wrapper.c b/wrapper.c
index 3258cdb171f..1108e4840a4 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -4,6 +4,13 @@
 #include "cache.h"
 #include "config.h"
 
+#ifdef HAVE_RTLGENRANDOM
+/* This is required to get access to RtlGenRandom. */
+#define SystemFunction036 NTAPI SystemFunction036
+#include <NTSecAPI.h>
+#undef SystemFunction036
+#endif
+
 static int memory_limit_check(size_t size, int gentle)
 {
 	static size_t limit = 0;

-- 
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