How to programmatically sign an app package (C++)

Learn how to sign an app package by using the SignerSignEx2 function.

If you want to programmatically create Windows app packages by using the Packaging API, you also need to sign the app packages before they can be deployed. The Packaging API doesn't provide a specialized method for signing app packages. Instead, use the standard cryptography functions to sign your app packages.

What you need to know

Technologies

• Introduction to Code Signing
• Packaging, deployment, and query of Windows apps
• cryptography functions

Prerequisites

• You need to have a packaged Windows app. For info about creating an app package, see How to create an app package.
• You need to have a code signing certificate that is appropriate for signing the app package. For info about creating a test code signing certificate, see How to create an app package signing certificate. Load this signing certificate into a CERT_CONTEXT structure. For example, you can use PFXImportCertStore and CertFindCertificateInStore to load a signing certificate.
• Windows 8 introduces the SignerSignEx2 function. Use SignerSignEx2 when you sign Windows app packages.

Instructions

Step 1: Define the required structures for SignerSignEx2

In addition to the Wincrypt.h header, the SignerSignEx2 function depends on many structures that aren't defined in any SDK header file. To use SignerSignEx2, you must define these structures yourself:

typedef struct _SIGNER_FILE_INFO
{
    DWORD cbSize;
    LPCWSTR pwszFileName;
    HANDLE hFile;
}SIGNER_FILE_INFO, *PSIGNER_FILE_INFO;
 
typedef struct _SIGNER_BLOB_INFO
{
    DWORD cbSize;
    GUID *pGuidSubject;
    DWORD cbBlob;
    BYTE *pbBlob;
    LPCWSTR pwszDisplayName;
}SIGNER_BLOB_INFO, *PSIGNER_BLOB_INFO;
 
typedef struct _SIGNER_SUBJECT_INFO
{
    DWORD cbSize;
    DWORD *pdwIndex;
    DWORD dwSubjectChoice;
    union
    {
        SIGNER_FILE_INFO *pSignerFileInfo;
        SIGNER_BLOB_INFO *pSignerBlobInfo;
    };
}SIGNER_SUBJECT_INFO, *PSIGNER_SUBJECT_INFO;
 
// dwSubjectChoice should be one of the following:
#define SIGNER_SUBJECT_FILE    0x01
#define SIGNER_SUBJECT_BLOB    0x02
 
typedef struct _SIGNER_ATTR_AUTHCODE
{
    DWORD cbSize;
    BOOL fCommercial;
    BOOL fIndividual;
    LPCWSTR pwszName;
    LPCWSTR pwszInfo;
}SIGNER_ATTR_AUTHCODE, *PSIGNER_ATTR_AUTHCODE;
 
typedef struct _SIGNER_SIGNATURE_INFO
{
    DWORD cbSize;
    ALG_ID algidHash;
    DWORD dwAttrChoice;
    union
    {
        SIGNER_ATTR_AUTHCODE *pAttrAuthcode;
    };
    PCRYPT_ATTRIBUTES psAuthenticated;
    PCRYPT_ATTRIBUTES psUnauthenticated;
}SIGNER_SIGNATURE_INFO, *PSIGNER_SIGNATURE_INFO;
 
// dwAttrChoice should be one of the following:
#define SIGNER_NO_ATTR          0x00
#define SIGNER_AUTHCODE_ATTR    0x01
 
typedef struct _SIGNER_PROVIDER_INFO
{
    DWORD cbSize;
    LPCWSTR pwszProviderName;
    DWORD dwProviderType;
    DWORD dwKeySpec;
    DWORD dwPvkChoice;
    union
    {
        LPWSTR pwszPvkFileName;
        LPWSTR pwszKeyContainer;
    };
}SIGNER_PROVIDER_INFO, *PSIGNER_PROVIDER_INFO;
 
//dwPvkChoice should be one of the following:
#define PVK_TYPE_FILE_NAME       0x01
#define PVK_TYPE_KEYCONTAINER    0x02
 
typedef struct _SIGNER_SPC_CHAIN_INFO
{
    DWORD cbSize;
    LPCWSTR pwszSpcFile;
    DWORD dwCertPolicy; 
    HCERTSTORE hCertStore;
}SIGNER_SPC_CHAIN_INFO, *PSIGNER_SPC_CHAIN_INFO;
 
typedef struct _SIGNER_CERT_STORE_INFO
{
    DWORD cbSize;
    PCCERT_CONTEXT pSigningCert;
    DWORD dwCertPolicy;
    HCERTSTORE hCertStore;
}SIGNER_CERT_STORE_INFO, *PSIGNER_CERT_STORE_INFO;
 
//dwCertPolicy can be a combination of the following flags:
#define SIGNER_CERT_POLICY_STORE            0x01
#define SIGNER_CERT_POLICY_CHAIN            0x02
#define SIGNER_CERT_POLICY_SPC              0x04
#define SIGNER_CERT_POLICY_CHAIN_NO_ROOT    0x08
 
typedef struct _SIGNER_CERT
{
    DWORD cbSize;
    DWORD dwCertChoice;
    union
    {
        LPCWSTR pwszSpcFile;
        SIGNER_CERT_STORE_INFO *pCertStoreInfo;
        SIGNER_SPC_CHAIN_INFO *pSpcChainInfo;
    };
    HWND hwnd;
}SIGNER_CERT, *PSIGNER_CERT;
 
//dwCertChoice should be one of the following
#define SIGNER_CERT_SPC_FILE     0x01
#define SIGNER_CERT_STORE        0x02
#define SIGNER_CERT_SPC_CHAIN    0x03
 
typedef struct _SIGNER_CONTEXT
{
    DWORD cbSize;
    DWORD cbBlob;
    BYTE *pbBlob;
}SIGNER_CONTEXT, *PSIGNER_CONTEXT;
 
typedef struct _SIGNER_SIGN_EX2_PARAMS
{
    DWORD dwFlags;
    PSIGNER_SUBJECT_INFO pSubjectInfo;
    PSIGNER_CERT pSigningCert;
    PSIGNER_SIGNATURE_INFO pSignatureInfo;
    PSIGNER_PROVIDER_INFO pProviderInfo;
    DWORD dwTimestampFlags;
    PCSTR pszAlgorithmOid;
    PCWSTR pwszTimestampURL;
    PCRYPT_ATTRIBUTES pCryptAttrs;
    PVOID pSipData;
    PSIGNER_CONTEXT *pSignerContext;
    PVOID pCryptoPolicy;
    PVOID pReserved;
} SIGNER_SIGN_EX2_PARAMS, *PSIGNER_SIGN_EX2_PARAMS;
 
typedef struct _APPX_SIP_CLIENT_DATA
{
    PSIGNER_SIGN_EX2_PARAMS pSignerParams;
    IUnknown* pAppxSipState;
} APPX_SIP_CLIENT_DATA, *PAPPX_SIP_CLIENT_DATA;

Step 2: Call SignerSignEx2 to sign the app package

After you define the required structures that are specified in the previous step, you can use any of the options available on the SignerSignEx2 function to sign an app package. When you use SignerSignEx2 with Windows app packages, these restrictions apply:

• You must provide a pointer to an APPX_SIP_CLIENT_DATA structure as the pSipData parameter when you sign an app package. You must populate the pSignerParams member of APPX_SIP_CLIENT_DATA with the same parameters that you use to sign the app package. To do this, define your desired parameters on the SIGNER_SIGN_EX2_PARAMS structure, assign the address of this structure to pSignerParams, and then directly reference the structure's members as well when you call SignerSignEx2.
• After you call SignerSignEx2, you must free the pAppxSipState on the pSipData by calling IUnknown::Release on pAppxSipState if it's not NULL.
• The algidHash member of the SIGNER_SIGNATURE_INFO structure must be the same hash algorithm that was used in creating the app package. For info about how to determine the hash algorithm from the app package, see How to sign an app package using SignTool. The Windows 8 default algorithm that MakeAppx and Visual Studio use to create app packages is “algidHash = CALG_SHA_256”.
• If you want to time stamp the signature on the app package as well, you must do so during the call to SignerSignEx2 by providing SignerSignEx2's optional time stamping parameters (dwTimestampFlags, pszTimestampAlgorithmOid, pwszHttpTimeStamp, psRequest). Calling SignerTimeStampEx3 or its variants on an app package that is already signed is unsupported.

Here is some example code that shows how to call SignerSignEx2:

HRESULT SignAppxPackage(
    _In_ PCCERT_CONTEXT signingCertContext,
    _In_ LPCWSTR packageFilePath)
{
    HRESULT hr = S_OK;
 
    // Initialize the parameters for SignerSignEx2
    DWORD signerIndex = 0;
 
    SIGNER_FILE_INFO fileInfo = {};
    fileInfo.cbSize = sizeof(SIGNER_FILE_INFO);
    fileInfo.pwszFileName = packageFilePath;
 
    SIGNER_SUBJECT_INFO subjectInfo = {};
    subjectInfo.cbSize = sizeof(SIGNER_SUBJECT_INFO);
    subjectInfo.pdwIndex = &signerIndex;
    subjectInfo.dwSubjectChoice = SIGNER_SUBJECT_FILE;
    subjectInfo.pSignerFileInfo = &fileInfo;
 
    SIGNER_CERT_STORE_INFO certStoreInfo = {};
    certStoreInfo.cbSize = sizeof(SIGNER_CERT_STORE_INFO);
    certStoreInfo.dwCertPolicy = SIGNER_CERT_POLICY_CHAIN_NO_ROOT;
    certStoreInfo.pSigningCert = signingCertContext;
 
    SIGNER_CERT cert = {};
    cert.cbSize = sizeof(SIGNER_CERT);
    cert.dwCertChoice = SIGNER_CERT_STORE;
    cert.pCertStoreInfo = &certStoreInfo;
 
    // The algidHash of the signature to be created must match the
    // hash algorithm used to create the app package
    SIGNER_SIGNATURE_INFO signatureInfo = {};
    signatureInfo.cbSize = sizeof(SIGNER_SIGNATURE_INFO);
    signatureInfo.algidHash = CALG_SHA_256; 
    signatureInfo.dwAttrChoice = SIGNER_NO_ATTR;
 
    SIGNER_SIGN_EX2_PARAMS signerParams = {};
    signerParams.pSubjectInfo = &subjectInfo;
    signerParams.pSigningCert = &cert;
    signerParams.pSignatureInfo = &signatureInfo;
 
    APPX_SIP_CLIENT_DATA sipClientData = {};
    sipClientData.pSignerParams = &signerParams;
    signerParams.pSipData = &sipClientData;
 
    // Type definition for invoking SignerSignEx2 via GetProcAddress
    typedef HRESULT (WINAPI *SignerSignEx2Function)(
        DWORD,
        PSIGNER_SUBJECT_INFO,
        PSIGNER_CERT,
        PSIGNER_SIGNATURE_INFO,
        PSIGNER_PROVIDER_INFO,
        DWORD,
        PCSTR,
        PCWSTR,
        PCRYPT_ATTRIBUTES,
        PVOID,
        PSIGNER_CONTEXT *,
        PVOID,
        PVOID); 
 
    // Load the SignerSignEx2 function from MSSign32.dll
    HMODULE msSignModule = LoadLibraryEx(
        L"MSSign32.dll", 
        NULL, 
        LOAD_LIBRARY_SEARCH_SYSTEM32);

    if (msSignModule)
    {
        SignerSignEx2Function SignerSignEx2 = reinterpret_cast<SignerSignEx2Function>(
            GetProcAddress(msSignModule, "SignerSignEx2"));
        if (SignerSignEx2)
        {
            hr = SignerSignEx2(
                signerParams.dwFlags,
                signerParams.pSubjectInfo,
                signerParams.pSigningCert,
                signerParams.pSignatureInfo,
                signerParams.pProviderInfo,
                signerParams.dwTimestampFlags,
                signerParams.pszAlgorithmOid,
                signerParams.pwszTimestampURL,
                signerParams.pCryptAttrs,
                signerParams.pSipData,
                signerParams.pSignerContext,
                signerParams.pCryptoPolicy,
                signerParams.pReserved);
        }
        else
        {
            DWORD lastError = GetLastError();
            hr = HRESULT_FROM_WIN32(lastError);
        }
 
        FreeLibrary(msSignModule);
    }
    else
    {
        DWORD lastError = GetLastError();
        hr = HRESULT_FROM_WIN32(lastError);
    }
 
    // Free any state used during app package signing
    if (sipClientData.pAppxSipState)
    {
        sipClientData.pAppxSipState->Release();
    }
 
    return hr;
}

Remarks

After you sign the app package, you can also attempt to validate the signature programmatically by using the WinVerifyTrust function with WINTRUST_ACTION_GENERIC_VERIFY_V2. There are no special considerations in this case for using WinVerifyTrust with Windows app packages.

Related topics

Introduction to Code Signing

Packaging API

cryptography functions