C - Verify code signatures - Windows API - c

Question

I need to verify code signatures of binaries. Microsoft Authenticode I think is the term. Is there a sane way to do this using the Windows API?

Answer 1

Have you looked at WinVerifyTrust ? Since it's not immediately obvious how to use it to verify the signature of a binary, you probably want to look at the sample code specifically for that.

Answer 2

How to find authenticode for drivers:
Disclaimer: I did not write this code.
BOOL VerifyEmbeddedSignature(LPCWSTR pwszSourceFile)
{
LONG lStatus;
GUID WintrustVerifyGuid = WINTRUST_ACTION_GENERIC_VERIFY_V2;
GUID DriverActionGuid = DRIVER_ACTION_VERIFY;
HANDLE hFile;
DWORD dwHash;
BYTE bHash[100];
HCATINFO hCatInfo;
HCATADMIN hCatAdmin;
WINTRUST_DATA wd = { 0 };
WINTRUST_FILE_INFO wfi = { 0 };
WINTRUST_CATALOG_INFO wci = { 0 };
////set up structs to verify files with cert signatures
memset(&wfi, 0, sizeof(wfi));
wfi.cbStruct = sizeof( WINTRUST_FILE_INFO );
wfi.pcwszFilePath = pwszSourceFile;
wfi.hFile = NULL;
wfi.pgKnownSubject = NULL;
memset(&wd, 0, sizeof(wd));
wd.cbStruct = sizeof( WINTRUST_DATA );
wd.dwUnionChoice = WTD_CHOICE_FILE;
wd.pFile = &wfi;
wd.dwUIChoice = WTD_UI_NONE;
wd.fdwRevocationChecks = WTD_REVOKE_NONE;
wd.dwStateAction = 0;
wd.dwProvFlags = WTD_SAFER_FLAG;
wd.hWVTStateData = NULL;
wd.pwszURLReference = NULL;
wd.pPolicyCallbackData = NULL;
wd.pSIPClientData = NULL;
wd.dwUIContext = 0;
lStatus = WinVerifyTrust( NULL, &WintrustVerifyGuid, &wd );
////if failed, try to verify using catalog files
if (lStatus != ERROR_SUCCESS)
{
//open the file
hFile = CreateFileW(pwszSourceFile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == INVALID_HANDLE_VALUE)
return FALSE;
dwHash = sizeof(bHash);
if (!CryptCATAdminCalcHashFromFileHandle(hFile, &dwHash, bHash, 0))
{
CloseHandle(hFile);
return FALSE;
}
//Create a string form of the hash (used later in pszMemberTag)
LPWSTR pszMemberTag = new WCHAR[dwHash * 2 + 1];
for ( DWORD dw = 0; dw < dwHash; ++dw )
{
wsprintfW( &pszMemberTag[dw * 2], L"%02X", bHash[dw] );
}
if (!CryptCATAdminAcquireContext(&hCatAdmin, &DriverActionGuid, 0))
{
CloseHandle(hFile);
return FALSE;
}
//find the catalog which contains the hash
hCatInfo = CryptCATAdminEnumCatalogFromHash(hCatAdmin, bHash, dwHash, 0, NULL);
if ( hCatInfo )
{
CATALOG_INFO ci = { 0 };
CryptCATCatalogInfoFromContext( hCatInfo, &ci, 0 );
memset(&wci, 0, sizeof(wci));
wci.cbStruct = sizeof( WINTRUST_CATALOG_INFO );
wci.pcwszCatalogFilePath = ci.wszCatalogFile;
wci.pcwszMemberFilePath = pwszSourceFile;
wci.pcwszMemberTag = pszMemberTag;
memset(&wd, 0, sizeof(wd));
wd.cbStruct = sizeof( WINTRUST_DATA );
wd.dwUnionChoice = WTD_CHOICE_CATALOG;
wd.pCatalog = &wci;
wd.dwUIChoice = WTD_UI_NONE;
wd.fdwRevocationChecks = WTD_STATEACTION_VERIFY;
wd.dwProvFlags = 0;
wd.hWVTStateData = NULL;
wd.pwszURLReference = NULL;
wd.pPolicyCallbackData = NULL;
wd.pSIPClientData = NULL;
wd.dwUIContext = 0;
lStatus = WinVerifyTrust( NULL, &WintrustVerifyGuid, &wd );
CryptCATAdminReleaseCatalogContext( hCatAdmin, hCatInfo, 0 );
}
CryptCATAdminReleaseContext( hCatAdmin, 0 );
delete[] pszMemberTag;
CloseHandle(hFile);
}
if (lStatus != ERROR_SUCCESS)
return false;
else
return true;
}

Answer 3

Here is the working code to verify a file (technically any file type).
#include <stdio.h>
#include <windows.h>
#include <Softpub.h>
#include <wincrypt.h>
#include <wintrust.h>
#include <mscat.h>
#include <atlbase.h>
// Link with the Wintrust.lib file.
#pragma comment (lib, "wintrust")
BOOL VerifySignature(LPCSTR path) //We will receive the char* filepath not wchar*
{
USES_CONVERSION;
LPCWSTR pwszSourceFile = A2W(path); //We convert the char* to wchar*
LONG lStatus;
GUID WintrustVerifyGuid = WINTRUST_ACTION_GENERIC_VERIFY_V2;
GUID DriverActionGuid = DRIVER_ACTION_VERIFY;
HANDLE hFile;
DWORD dwHash;
BYTE bHash[100];
HCATINFO hCatInfo;
HCATADMIN hCatAdmin;
WINTRUST_DATA wd = { 0 };
WINTRUST_FILE_INFO wfi = { 0 };
WINTRUST_CATALOG_INFO wci = { 0 };
////set up structs to verify files with cert signatures
wfi.cbStruct = sizeof(WINTRUST_FILE_INFO);
wfi.pcwszFilePath = pwszSourceFile;
wfi.hFile = NULL;
wfi.pgKnownSubject = NULL;
wd.cbStruct = sizeof(WINTRUST_DATA);
wd.pPolicyCallbackData = NULL;
wd.pSIPClientData = NULL;
wd.dwUIChoice = WTD_UI_NONE;
wd.fdwRevocationChecks = WTD_REVOKE_NONE;
wd.dwUnionChoice = WTD_CHOICE_FILE;
wd.pFile = &wfi;
wd.dwStateAction = WTD_STATEACTION_VERIFY;
wd.hWVTStateData = NULL;
wd.pwszURLReference = NULL;
wd.dwProvFlags |= WTD_CACHE_ONLY_URL_RETRIEVAL;
wd.dwUIContext = 0;
wd.pSignatureSettings = 0;
lStatus = WinVerifyTrust((HWND)INVALID_HANDLE_VALUE, &WintrustVerifyGuid, &wd);
wd.dwStateAction = WTD_STATEACTION_CLOSE;
WinVerifyTrust((HWND)INVALID_HANDLE_VALUE, &WintrustVerifyGuid, &wd); //close hWVTStateData
////if failed, try to verify using catalog files
if (lStatus != ERROR_SUCCESS)
{
//open the file
hFile = CreateFileW(pwszSourceFile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == INVALID_HANDLE_VALUE)
return FALSE;
dwHash = sizeof(bHash);
if (!CryptCATAdminCalcHashFromFileHandle(hFile, &dwHash, bHash, 0))
{
CloseHandle(hFile);
return FALSE;
}
//Create a string form of the hash (used later in pszMemberTag)
LPWSTR pszMemberTag = new WCHAR[dwHash * 2 + 1];
for (DWORD dw = 0; dw < dwHash; ++dw)
{
wsprintfW(&pszMemberTag[dw * 2], L"%02X", bHash[dw]);
}
if (!CryptCATAdminAcquireContext(&hCatAdmin, &DriverActionGuid, 0))
{
CloseHandle(hFile);
return FALSE;
}
//find the catalog which contains the hash
hCatInfo = CryptCATAdminEnumCatalogFromHash(hCatAdmin, bHash, dwHash, 0, NULL);
if (hCatInfo)
{
CATALOG_INFO ci = { 0 };
CryptCATCatalogInfoFromContext(hCatInfo, &ci, 0);
memset(&wci, 0, sizeof(wci));
wci.cbStruct = sizeof(WINTRUST_CATALOG_INFO);
wci.pcwszCatalogFilePath = ci.wszCatalogFile;
wci.pcwszMemberFilePath = pwszSourceFile;
wci.hMemberFile = hFile;
wci.pcwszMemberTag = pszMemberTag;
wci.pbCalculatedFileHash = bHash;
wci.cbCalculatedFileHash = dwHash;
wci.hCatAdmin = hCatAdmin;
memset(&wd, 0, sizeof(wd));
wd.cbStruct = sizeof(WINTRUST_DATA);
wd.pPolicyCallbackData = NULL;
wd.pSIPClientData = NULL;
wd.dwUIChoice = WTD_UI_NONE;
wd.fdwRevocationChecks = WTD_REVOKE_NONE;
wd.dwUnionChoice = WTD_CHOICE_CATALOG;
wd.pCatalog = &wci;
wd.dwStateAction = WTD_STATEACTION_VERIFY;
wd.hWVTStateData = NULL;
wd.pwszURLReference = NULL;
wd.dwProvFlags |= WTD_CACHE_ONLY_URL_RETRIEVAL;
wd.dwUIContext = 0;
wd.pSignatureSettings = 0;
lStatus = WinVerifyTrust((HWND)INVALID_HANDLE_VALUE, &WintrustVerifyGuid, &wd);
wd.dwStateAction = WTD_STATEACTION_CLOSE;
WinVerifyTrust((HWND)INVALID_HANDLE_VALUE, &WintrustVerifyGuid, &wd); //close hWVTStateData
CryptCATAdminReleaseCatalogContext(hCatAdmin, hCatInfo, 0);
}
CryptCATAdminReleaseContext(hCatAdmin, 0);
delete[] pszMemberTag;
CloseHandle(hFile);
}
return (lStatus == ERROR_SUCCESS);
}
int main(int argc, char *argv[])
{
if (VerifySignature(argv[1]))
printf("Verified file signature\n");
else
printf("Could not verify file signature\n");
return 0;
}