WinVerifyTrust、CruptQueryObject兩種方法的比較
A word of warning: it's worse than you already thought.
警告一句:情況比你想象的還要糟糕。
At least since introducing SHA-256 signing (has this always been the case?), it's possible for Authenticode to have multiple signatures. They're not encoded as multiple signatures in the PKCS-7 signature message; instead, they're unauthenticated message attributes of type OID_NESTED_SIGNATURE, each containing another complete PKCS-7 signature message.
WinVerifyTrust will tell you the file is valid if any of the signatures are valid and come from a trusted certificate chain. However it won't tell you which of the signatures was valid. If you then use CryptQueryObject to read the full PKCS-7 message, and only look at the certificate for the primary signature (as in the code samples here and on MSDN), you're not necessarily looking at a verified certificate. The associated signature might not match the executable, and/or the certificate might not have a trusted CA chain.
WinVerifyTrust可以判斷是否有任何一個證書是有效的。 然而它沒辦法告訴你哪個證書是有效的。 如果是用CruptQueryObject接口，又沒有辦法得到除了主證書以外的其他證書信息。
If you're using the details of the primary signature to validate that the certificate is one your software trusts, you're vulnerable to a situation where WinVerifyTrust is trusting a secondary signature, but your code is checking the primary signature's certificate is what you expected, and you haven't noticed that the signature from the primary certificate is nonsense. An attacker could use your public certificate without owning its private key, combined with some other code-signing certificate issued to someone else, to bypass a publisher check this way.
如果你通過主證書的詳細信息去驗證軟件是否可信任，在這種場景下容易被攻擊：WinVerifyTrust信任了第二個證書，但是你的檢查代碼又在檢查主證書，可能即使主證書並不匹配但是WinVerifyTrust也檢查通過了。
From Win8 onwards, WinVerifyTrust can optionally validate specific signatures, so you should be able to iterate the signatures to find one that is valid and one that satisfies your requirements.
win8之后可以指定驗證哪個證書是有效的。
If you have to be Win7-compatible, though, as far as I know the best you can manage is MsiGetFileSignatureInformation. From experimentation (as for everything else here, the actual documentation is frustratingly woolly), it seems to return the trusted certificate when WinVerifyTrust trusts one. But if there isn't a trusted signature, it returns the primary signature's certificate anyway, so you still have to use WinVerifyTrust to check that first.
Of course there also plenty of possible time-of-check/time-of-use problems here.
WinVerifyTrust
驗證數字簽名是否有效，當前的用法解釋如下：
//-------------------------------------------------------------------
// Copyright (C) Microsoft. All rights reserved.
// Example of verifying the embedded signature of a PE file by using
// the WinVerifyTrust function.
#define _UNICODE 1
#define UNICODE 1
#include <tchar.h>
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <Softpub.h>
#include <wincrypt.h>
#include <wintrust.h>
// Link with the Wintrust.lib file.
#pragma comment (lib, "wintrust")
BOOL VerifyEmbeddedSignature(LPCWSTR pwszSourceFile)
{
LONG lStatus;
DWORD dwLastError;
// Initialize the WINTRUST_FILE_INFO structure.
// 待驗證文件的完整路徑
WINTRUST_FILE_INFO FileData;
memset(&FileData, 0, sizeof(FileData));
FileData.cbStruct = sizeof(WINTRUST_FILE_INFO);
FileData.pcwszFilePath = pwszSourceFile;
FileData.hFile = NULL;
FileData.pgKnownSubject = NULL;
/*
WVTPolicyGUID specifies the policy to apply on the file
WINTRUST_ACTION_GENERIC_VERIFY_V2 policy checks:
1) The certificate used to sign the file chains up to a root
certificate located in the trusted root certificate store. This
implies that the identity of the publisher has been verified by
a certification authority.
2) In cases where user interface is displayed (which this example
does not do), WinVerifyTrust will check for whether the
end entity certificate is stored in the trusted publisher store,
implying that the user trusts content from this publisher.
3) The end entity certificate has sufficient permission to sign
code, as indicated by the presence of a code signing EKU or no
EKU.
*/
GUID WVTPolicyGUID = WINTRUST_ACTION_GENERIC_VERIFY_V2;
WINTRUST_DATA WinTrustData;
// Initialize the WinVerifyTrust input data structure.
// Default all fields to 0.
memset(&WinTrustData, 0, sizeof(WinTrustData));
WinTrustData.cbStruct = sizeof(WinTrustData);
// Use default code signing EKU.
WinTrustData.pPolicyCallbackData = NULL;
// No data to pass to SIP.
WinTrustData.pSIPClientData = NULL;
// Disable WVT UI.
WinTrustData.dwUIChoice = WTD_UI_NONE;
// No revocation checking.
WinTrustData.fdwRevocationChecks = WTD_REVOKE_NONE;
// 采用文件方式驗證， 其他還有內存等
// Verify an embedded signature on a file.
WinTrustData.dwUnionChoice = WTD_CHOICE_FILE;
// Verify action.
WinTrustData.dwStateAction = WTD_STATEACTION_VERIFY;
// Verification sets this value.
WinTrustData.hWVTStateData = NULL;
// Not used.
WinTrustData.pwszURLReference = NULL;
// This is not applicable if there is no UI because it changes
// the UI to accommodate running applications instead of
// installing applications.
WinTrustData.dwUIContext = 0;
// Set pFile.
WinTrustData.pFile = &FileData;
// 當前操作是要驗證簽名，后面還需要調用一次關閉去釋放從此次驗證操作中得到的放在trustData中的數據
// PS: 微軟為啥老喜歡同一個接口換個flag就變成完全不同的功能，感覺用個FreeWinVerifyTrustedData之類的不好嘛。。（微軟：你在教我做事？) -_-
// WinVerifyTrust verifies signatures as specified by the GUID
// and Wintrust_Data.
lStatus = WinVerifyTrust(
NULL,
&WVTPolicyGUID,
&WinTrustData);
switch (lStatus)
{
case ERROR_SUCCESS:
/*
Signed file:
- Hash that represents the subject is trusted.
- Trusted publisher without any verification errors.
- UI was disabled in dwUIChoice. No publisher or
time stamp chain errors.
- UI was enabled in dwUIChoice and the user clicked
"Yes" when asked to install and run the signed
subject.
*/
// 只是驗證了簽名有效，但是到底是不是預期的簽名者進行的簽名還不確定， 可以進一步驗證
wprintf_s(L"The file \"%s\" is signed and the signature "
L"was verified.\n",
pwszSourceFile);
break;
case TRUST_E_NOSIGNATURE:
// The file was not signed or had a signature
// that was not valid.
// Get the reason for no signature.
dwLastError = GetLastError();
if (TRUST_E_NOSIGNATURE == dwLastError ||
TRUST_E_SUBJECT_FORM_UNKNOWN == dwLastError ||
TRUST_E_PROVIDER_UNKNOWN == dwLastError)
{
// The file was not signed.
wprintf_s(L"The file \"%s\" is not signed.\n",
pwszSourceFile);
}
else
{
// The signature was not valid or there was an error
// opening the file.
wprintf_s(L"An unknown error occurred trying to "
L"verify the signature of the \"%s\" file.\n",
pwszSourceFile);
}
break;
case TRUST_E_EXPLICIT_DISTRUST:
// The hash that represents the subject or the publisher
// is not allowed by the admin or user.
wprintf_s(L"The signature is present, but specifically "
L"disallowed.\n");
break;
case TRUST_E_SUBJECT_NOT_TRUSTED:
// The user clicked "No" when asked to install and run.
wprintf_s(L"The signature is present, but not "
L"trusted.\n");
break;
case CRYPT_E_SECURITY_SETTINGS:
/*
The hash that represents the subject or the publisher
was not explicitly trusted by the admin and the
admin policy has disabled user trust. No signature,
publisher or time stamp errors.
*/
wprintf_s(L"CRYPT_E_SECURITY_SETTINGS - The hash "
L"representing the subject or the publisher wasn't "
L"explicitly trusted by the admin and admin policy "
L"has disabled user trust. No signature, publisher "
L"or timestamp errors.\n");
break;
default:
// The UI was disabled in dwUIChoice or the admin policy
// has disabled user trust. lStatus contains the
// publisher or time stamp chain error.
wprintf_s(L"Error is: 0x%x.\n",
lStatus);
break;
}
// 設置flag為CLOSE， 然后釋放掉上面申請出來的內存。。
// Any hWVTStateData must be released by a call with close.
WinTrustData.dwStateAction = WTD_STATEACTION_CLOSE;
lStatus = WinVerifyTrust(
NULL,
&WVTPolicyGUID,
&WinTrustData);
return true;
}
int _tmain(int argc, _TCHAR* argv[])
{
if(argc > 1)
{
VerifyEmbeddedSignature(argv[1]);
}
return 0;
}
CryptQueryObject
獲取數字簽名信息，比如簽名者姓名，用於校驗簽名者是否符合預期
參考
stackoverflow上的這段英文的原文
兩個接口使用樣例
為什么調用CryptQueryObject接口獲取簽名時需要傳入PKCS #7類型
對這兩個接口的使用場景做了簡單比較
ms官方使用WinVerifyTrust樣例