Cómo obtener información de Authenticode firmaron los archivos ejecutables

Resumen

Puede utilizar la API WinVerifyTrust() para comprobar un archivo ejecutable de Authenticode firmado.

Aunque se comprueba una firma, un programa que también deba hacer lo siguiente:
  • Determinar los detalles del certificado que firmó el archivo ejecutable.
  • Determinar la fecha y la hora en que el archivo fue la marca de tiempo.
  • Recuperar el vínculo de dirección URL asociado al archivo.
  • Recuperar el certificado de marca de hora.
En este artículo se muestra cómo utilizar CryptQueryObject() API para recuperar información detallada de un archivo ejecutable de Authenticode firmado.

Más información

Las firmas Authenticode están basados en PKCS7, por lo tanto, puede utilizar CryptQueryObject y otras funciones de Crypto API para recuperar la firma PKCS7 y descodificar los atributos PKCS7.

El siguiente código de c de ejemplo muestra cómo utilizar estas API.

#include <windows.h>#include <wincrypt.h>
#include <wintrust.h>
#include <stdio.h>
#include <tchar.h>

#pragma comment(lib, "crypt32.lib")

#define ENCODING (X509_ASN_ENCODING | PKCS_7_ASN_ENCODING)

typedef struct {
LPWSTR lpszProgramName;
LPWSTR lpszPublisherLink;
LPWSTR lpszMoreInfoLink;
} SPROG_PUBLISHERINFO, *PSPROG_PUBLISHERINFO;

BOOL GetProgAndPublisherInfo(PCMSG_SIGNER_INFO pSignerInfo,
PSPROG_PUBLISHERINFO Info);
BOOL GetDateOfTimeStamp(PCMSG_SIGNER_INFO pSignerInfo, SYSTEMTIME *st);
BOOL PrintCertificateInfo(PCCERT_CONTEXT pCertContext);
BOOL GetTimeStampSignerInfo(PCMSG_SIGNER_INFO pSignerInfo,
PCMSG_SIGNER_INFO *pCounterSignerInfo);

int _tmain(int argc, TCHAR *argv[])
{
WCHAR szFileName[MAX_PATH];
HCERTSTORE hStore = NULL;
HCRYPTMSG hMsg = NULL;
PCCERT_CONTEXT pCertContext = NULL;
BOOL fResult;
DWORD dwEncoding, dwContentType, dwFormatType;
PCMSG_SIGNER_INFO pSignerInfo = NULL;
PCMSG_SIGNER_INFO pCounterSignerInfo = NULL;
DWORD dwSignerInfo;
CERT_INFO CertInfo;
SPROG_PUBLISHERINFO ProgPubInfo;
SYSTEMTIME st;

ZeroMemory(&ProgPubInfo, sizeof(ProgPubInfo));
__try
{
if (argc != 2)
{
_tprintf(_T("Usage: SignedFileInfo <filename>\n"));
return 0;
}

#ifdef UNICODE
lstrcpynW(szFileName, argv[1], MAX_PATH);
#else
if (mbstowcs(szFileName, argv[1], MAX_PATH) == -1)
{
printf("Unable to convert to unicode.\n");
__leave;
}
#endif

// Get message handle and store handle from the signed file.
fResult = CryptQueryObject(CERT_QUERY_OBJECT_FILE,
szFileName,
CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
CERT_QUERY_FORMAT_FLAG_BINARY,
0,
&dwEncoding,
&dwContentType,
&dwFormatType,
&hStore,
&hMsg,
NULL);
if (!fResult)
{
_tprintf(_T("CryptQueryObject failed with %x\n"), GetLastError());
__leave;
}

// Get signer information size.
fResult = CryptMsgGetParam(hMsg,
CMSG_SIGNER_INFO_PARAM,
0,
NULL,
&dwSignerInfo);
if (!fResult)
{
_tprintf(_T("CryptMsgGetParam failed with %x\n"), GetLastError());
__leave;
}

// Allocate memory for signer information.
pSignerInfo = (PCMSG_SIGNER_INFO)LocalAlloc(LPTR, dwSignerInfo);
if (!pSignerInfo)
{
_tprintf(_T("Unable to allocate memory for Signer Info.\n"));
__leave;
}

// Get Signer Information.
fResult = CryptMsgGetParam(hMsg,
CMSG_SIGNER_INFO_PARAM,
0,
(PVOID)pSignerInfo,
&dwSignerInfo);
if (!fResult)
{
_tprintf(_T("CryptMsgGetParam failed with %x\n"), GetLastError());
__leave;
}

// Get program name and publisher information from
// signer info structure.
if (GetProgAndPublisherInfo(pSignerInfo, &ProgPubInfo))
{
if (ProgPubInfo.lpszProgramName != NULL)
{
wprintf(L"Program Name : %s\n",
ProgPubInfo.lpszProgramName);
}

if (ProgPubInfo.lpszPublisherLink != NULL)
{
wprintf(L"Publisher Link : %s\n",
ProgPubInfo.lpszPublisherLink);
}

if (ProgPubInfo.lpszMoreInfoLink != NULL)
{
wprintf(L"MoreInfo Link : %s\n",
ProgPubInfo.lpszMoreInfoLink);
}
}

_tprintf(_T("\n"));

// Search for the signer certificate in the temporary
// certificate store.
CertInfo.Issuer = pSignerInfo->Issuer;
CertInfo.SerialNumber = pSignerInfo->SerialNumber;

pCertContext = CertFindCertificateInStore(hStore,
ENCODING,
0,
CERT_FIND_SUBJECT_CERT,
(PVOID)&CertInfo,
NULL);
if (!pCertContext)
{
_tprintf(_T("CertFindCertificateInStore failed with %x\n"),
GetLastError());
__leave;
}

// Print Signer certificate information.
_tprintf(_T("Signer Certificate:\n\n"));
PrintCertificateInfo(pCertContext);
_tprintf(_T("\n"));

// Get the timestamp certificate signerinfo structure.
if (GetTimeStampSignerInfo(pSignerInfo, &pCounterSignerInfo))
{
// Search for Timestamp certificate in the temporary
// certificate store.
CertInfo.Issuer = pCounterSignerInfo->Issuer;
CertInfo.SerialNumber = pCounterSignerInfo->SerialNumber;

pCertContext = CertFindCertificateInStore(hStore,
ENCODING,
0,
CERT_FIND_SUBJECT_CERT,
(PVOID)&CertInfo,
NULL);
if (!pCertContext)
{
_tprintf(_T("CertFindCertificateInStore failed with %x\n"),
GetLastError());
__leave;
}

// Print timestamp certificate information.
_tprintf(_T("TimeStamp Certificate:\n\n"));
PrintCertificateInfo(pCertContext);
_tprintf(_T("\n"));

// Find Date of timestamp.
if (GetDateOfTimeStamp(pCounterSignerInfo, &st))
{
_tprintf(_T("Date of TimeStamp : %02d/%02d/%04d %02d:%02d\n"),
st.wMonth,
st.wDay,
st.wYear,
st.wHour,
st.wMinute);
}
_tprintf(_T("\n"));
}
}
__finally
{
// Clean up.
if (ProgPubInfo.lpszProgramName != NULL)
LocalFree(ProgPubInfo.lpszProgramName);
if (ProgPubInfo.lpszPublisherLink != NULL)
LocalFree(ProgPubInfo.lpszPublisherLink);
if (ProgPubInfo.lpszMoreInfoLink != NULL)
LocalFree(ProgPubInfo.lpszMoreInfoLink);

if (pSignerInfo != NULL) LocalFree(pSignerInfo);
if (pCounterSignerInfo != NULL) LocalFree(pCounterSignerInfo);
if (pCertContext != NULL) CertFreeCertificateContext(pCertContext);
if (hStore != NULL) CertCloseStore(hStore, 0);
if (hMsg != NULL) CryptMsgClose(hMsg);
}
return 0;
}

BOOL PrintCertificateInfo(PCCERT_CONTEXT pCertContext)
{
BOOL fReturn = FALSE;
LPTSTR szName = NULL;
DWORD dwData;

__try
{
// Print Serial Number.
_tprintf(_T("Serial Number: "));
dwData = pCertContext->pCertInfo->SerialNumber.cbData;
for (DWORD n = 0; n < dwData; n++)
{
_tprintf(_T("%02x "),
pCertContext->pCertInfo->SerialNumber.pbData[dwData - (n + 1)]);
}
_tprintf(_T("\n"));

// Get Issuer name size.
if (!(dwData = CertGetNameString(pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
CERT_NAME_ISSUER_FLAG,
NULL,
NULL,
0)))
{
_tprintf(_T("CertGetNameString failed.\n"));
__leave;
}

// Allocate memory for Issuer name.
szName = (LPTSTR)LocalAlloc(LPTR, dwData * sizeof(TCHAR));
if (!szName)
{
_tprintf(_T("Unable to allocate memory for issuer name.\n"));
__leave;
}

// Get Issuer name.
if (!(CertGetNameString(pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
CERT_NAME_ISSUER_FLAG,
NULL,
szName,
dwData)))
{
_tprintf(_T("CertGetNameString failed.\n"));
__leave;
}

// print Issuer name.
_tprintf(_T("Issuer Name: %s\n"), szName);
LocalFree(szName);
szName = NULL;

// Get Subject name size.
if (!(dwData = CertGetNameString(pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
0,
NULL,
NULL,
0)))
{
_tprintf(_T("CertGetNameString failed.\n"));
__leave;
}

// Allocate memory for subject name.
szName = (LPTSTR)LocalAlloc(LPTR, dwData * sizeof(TCHAR));
if (!szName)
{
_tprintf(_T("Unable to allocate memory for subject name.\n"));
__leave;
}

// Get subject name.
if (!(CertGetNameString(pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
0,
NULL,
szName,
dwData)))
{
_tprintf(_T("CertGetNameString failed.\n"));
__leave;
}

// Print Subject Name.
_tprintf(_T("Subject Name: %s\n"), szName);

fReturn = TRUE;
}
__finally
{
if (szName != NULL) LocalFree(szName);
}

return fReturn;
}

LPWSTR AllocateAndCopyWideString(LPCWSTR inputString)
{
LPWSTR outputString = NULL;

outputString = (LPWSTR)LocalAlloc(LPTR,
(wcslen(inputString) + 1) * sizeof(WCHAR));
if (outputString != NULL)
{
lstrcpyW(outputString, inputString);
}
return outputString;
}

BOOL GetProgAndPublisherInfo(PCMSG_SIGNER_INFO pSignerInfo,
PSPROG_PUBLISHERINFO Info)
{
BOOL fReturn = FALSE;
PSPC_SP_OPUS_INFO OpusInfo = NULL;
DWORD dwData;
BOOL fResult;

__try
{
// Loop through authenticated attributes and find
// SPC_SP_OPUS_INFO_OBJID OID.
for (DWORD n = 0; n < pSignerInfo->AuthAttrs.cAttr; n++)
{
if (lstrcmpA(SPC_SP_OPUS_INFO_OBJID,
pSignerInfo->AuthAttrs.rgAttr[n].pszObjId) == 0)
{
// Get Size of SPC_SP_OPUS_INFO structure.
fResult = CryptDecodeObject(ENCODING,
SPC_SP_OPUS_INFO_OBJID,
pSignerInfo->AuthAttrs.rgAttr[n].rgValue[0].pbData,
pSignerInfo->AuthAttrs.rgAttr[n].rgValue[0].cbData,
0,
NULL,
&dwData);
if (!fResult)
{
_tprintf(_T("CryptDecodeObject failed with %x\n"),
GetLastError());
__leave;
}

// Allocate memory for SPC_SP_OPUS_INFO structure.
OpusInfo = (PSPC_SP_OPUS_INFO)LocalAlloc(LPTR, dwData);
if (!OpusInfo)
{
_tprintf(_T("Unable to allocate memory for Publisher Info.\n"));
__leave;
}

// Decode and get SPC_SP_OPUS_INFO structure.
fResult = CryptDecodeObject(ENCODING,
SPC_SP_OPUS_INFO_OBJID,
pSignerInfo->AuthAttrs.rgAttr[n].rgValue[0].pbData,
pSignerInfo->AuthAttrs.rgAttr[n].rgValue[0].cbData,
0,
OpusInfo,
&dwData);
if (!fResult)
{
_tprintf(_T("CryptDecodeObject failed with %x\n"),
GetLastError());
__leave;
}

// Fill in Program Name if present.
if (OpusInfo->pwszProgramName)
{
Info->lpszProgramName =
AllocateAndCopyWideString(OpusInfo->pwszProgramName);
}
else
Info->lpszProgramName = NULL;

// Fill in Publisher Information if present.
if (OpusInfo->pPublisherInfo)
{

switch (OpusInfo->pPublisherInfo->dwLinkChoice)
{
case SPC_URL_LINK_CHOICE:
Info->lpszPublisherLink =
AllocateAndCopyWideString(OpusInfo->pPublisherInfo->pwszUrl);
break;

case SPC_FILE_LINK_CHOICE:
Info->lpszPublisherLink =
AllocateAndCopyWideString(OpusInfo->pPublisherInfo->pwszFile);
break;

default:
Info->lpszPublisherLink = NULL;
break;
}
}
else
{
Info->lpszPublisherLink = NULL;
}

// Fill in More Info if present.
if (OpusInfo->pMoreInfo)
{
switch (OpusInfo->pMoreInfo->dwLinkChoice)
{
case SPC_URL_LINK_CHOICE:
Info->lpszMoreInfoLink =
AllocateAndCopyWideString(OpusInfo->pMoreInfo->pwszUrl);
break;

case SPC_FILE_LINK_CHOICE:
Info->lpszMoreInfoLink =
AllocateAndCopyWideString(OpusInfo->pMoreInfo->pwszFile);
break;

default:
Info->lpszMoreInfoLink = NULL;
break;
}
}
else
{
Info->lpszMoreInfoLink = NULL;
}

fReturn = TRUE;

break; // Break from for loop.
} // lstrcmp SPC_SP_OPUS_INFO_OBJID
} // for
}
__finally
{
if (OpusInfo != NULL) LocalFree(OpusInfo);
}

return fReturn;
}

BOOL GetDateOfTimeStamp(PCMSG_SIGNER_INFO pSignerInfo, SYSTEMTIME *st)
{
BOOL fResult;
FILETIME lft, ft;
DWORD dwData;
BOOL fReturn = FALSE;

// Loop through authenticated attributes and find
// szOID_RSA_signingTime OID.
for (DWORD n = 0; n < pSignerInfo->AuthAttrs.cAttr; n++)
{
if (lstrcmpA(szOID_RSA_signingTime,
pSignerInfo->AuthAttrs.rgAttr[n].pszObjId) == 0)
{
// Decode and get FILETIME structure.
dwData = sizeof(ft);
fResult = CryptDecodeObject(ENCODING,
szOID_RSA_signingTime,
pSignerInfo->AuthAttrs.rgAttr[n].rgValue[0].pbData,
pSignerInfo->AuthAttrs.rgAttr[n].rgValue[0].cbData,
0,
(PVOID)&ft,
&dwData);
if (!fResult)
{
_tprintf(_T("CryptDecodeObject failed with %x\n"),
GetLastError());
break;
}

// Convert to local time.
FileTimeToLocalFileTime(&ft, &lft);
FileTimeToSystemTime(&lft, st);

fReturn = TRUE;

break; // Break from for loop.

} //lstrcmp szOID_RSA_signingTime
} // for

return fReturn;
}

BOOL GetTimeStampSignerInfo(PCMSG_SIGNER_INFO pSignerInfo, PCMSG_SIGNER_INFO *pCounterSignerInfo)
{
PCCERT_CONTEXT pCertContext = NULL;
BOOL fReturn = FALSE;
BOOL fResult;
DWORD dwSize;

__try
{
*pCounterSignerInfo = NULL;

// Loop through unathenticated attributes for
// szOID_RSA_counterSign OID.
for (DWORD n = 0; n < pSignerInfo->UnauthAttrs.cAttr; n++)
{
if (lstrcmpA(pSignerInfo->UnauthAttrs.rgAttr[n].pszObjId,
szOID_RSA_counterSign) == 0)
{
// Get size of CMSG_SIGNER_INFO structure.
fResult = CryptDecodeObject(ENCODING,
PKCS7_SIGNER_INFO,
pSignerInfo->UnauthAttrs.rgAttr[n].rgValue[0].pbData,
pSignerInfo->UnauthAttrs.rgAttr[n].rgValue[0].cbData,
0,
NULL,
&dwSize);
if (!fResult)
{
_tprintf(_T("CryptDecodeObject failed with %x\n"),
GetLastError());
__leave;
}

// Allocate memory for CMSG_SIGNER_INFO.
*pCounterSignerInfo = (PCMSG_SIGNER_INFO)LocalAlloc(LPTR, dwSize);
if (!*pCounterSignerInfo)
{
_tprintf(_T("Unable to allocate memory for timestamp info.\n"));
__leave;
}

// Decode and get CMSG_SIGNER_INFO structure
// for timestamp certificate.
fResult = CryptDecodeObject(ENCODING,
PKCS7_SIGNER_INFO,
pSignerInfo->UnauthAttrs.rgAttr[n].rgValue[0].pbData,
pSignerInfo->UnauthAttrs.rgAttr[n].rgValue[0].cbData,
0,
(PVOID)*pCounterSignerInfo,
&dwSize);
if (!fResult)
{
_tprintf(_T("CryptDecodeObject failed with %x\n"),
GetLastError());
__leave;
}

fReturn = TRUE;

break; // Break from for loop.
}
}
}
__finally
{
// Clean up.
if (pCertContext != NULL) CertFreeCertificateContext(pCertContext);
}

return fReturn;
}

Propiedades

Id. de artículo: 323809 - Última revisión: 17 ene. 2017 - Revisión: 1

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