Question

如何在以编程方式使用CoSign Signature API创建签名字段时设置清除策略，以保护签名免受更改？我在文档中找到了一个枚举SAPI_ENUM_SIG_CLEAR_POLICY但找不到使用情况。

编辑：是否可以通过SAPILib COM使用CoSign从c＃实现。

Answer 1

明确政策是一种扩展信息，在SAPI_CUSTOM_FIELD_ELEMENTS_STRUCT结构中设置为自定义字段。下面的代码基于DevPortal的Hello World example，演示了如何将签名字段的清除策略设置为SAPI_ENUM_SIG_CLEAR_POLICY_NEVER（签名无法清除）。

int _tmain(int argc, _TCHAR* argv[])
{
    int                         rc;
    SAPI_SES_HANDLE             hSession;

    // Custom Values
    wchar_t                     *filePath               = L"c:\\temp\\demo.pdf";    // PDF file to sign
    wchar_t                     *username               = L"{signer_username}";     // CoSign Account Username
    wchar_t                     *domain                 = NULL;                     // CoSign Account Domain
    wchar_t                     *password               = L"{signer_password}";     // CoSign Account Password
    int                         sigPageNum              = 1;                        // Create Signature on the first page
    int                         sigX                    = 145;                      // Signature Field X location
    int                         sigY                    = 125;                      // Signature Field Y location
    int                         sigWidth                = 160;                      // Signature Field Width
    int                         sigHeight               = 45;                       // Signature Field Height
    wchar_t                     *timeFormat             = L"hh:mm:ss";              // Time appearance format mask
    wchar_t                     *dateFormat             = L"dd/MM/yyyy";            // Date appearance format mask
    int                         appearanceMask          = SAPI_ENUM_DRAWING_ELEMENT_GRAPHICAL_IMAGE |       // Elements to display on the Signature Field
                                                          SAPI_ENUM_DRAWING_ELEMENT_SIGNED_BY       |
                                                          SAPI_ENUM_DRAWING_ELEMENT_TIME;
    SAPI_ENUM_SIG_CLEAR_POLICY_TYPE sigClearPolicy      = SAPI_ENUM_SIG_CLEAR_POLICY_NEVER; // Signature clear policy

    // Initialize SAPI library
    if ((rc = SAPIInit()) != SAPI_OK)
    {
        printf("Error on SAPIInit, rc = 0x%x, Extended error 0x%x\n", rc, SAPIExtendedLastErrorGet());
        return -1;
    }

    // Acquire SAPI session handle
    if ((rc = SAPIHandleAcquire(&hSession)) != SAPI_OK)
    {
        printf("Error on SAPIHandleAcquire, rc = 0x%x, Extended error 0x%x\n", rc, SAPIExtendedLastErrorGet());
        return -1;
    }

    // Personalize SAPI Session
    if ((rc = SAPILogon(hSession, (SAPI_LPCWSTR) username, (SAPI_LPCWSTR) domain, (unsigned char*) password, (wcslen(password)+1)*2)) != SAPI_OK)
    {
        SAPIHandleRelease (hSession);   // Release memory allocated for Session Handle
        printf("Error on SAPILogon, rc = 0x%x, Extended error 0x%x\n", rc, SAPIExtendedLastErrorGet());
        return -1;
    }

    // Instantiate SAPI_SIG_FIELD_SETTINGS struct
    SAPI_SIG_FIELD_SETTINGS sSigFieldSettings;
    memset(&sSigFieldSettings, 0, sizeof(SAPI_SIG_FIELD_SETTINGS));
    sSigFieldSettings.StructLen = sizeof(SAPI_SIG_FIELD_SETTINGS);

    // Define Signature Field Settings
    sSigFieldSettings.Page              = sigPageNum;
    sSigFieldSettings.X                 = sigX;
    sSigFieldSettings.Y                 = sigY;
    sSigFieldSettings.Width             = sigWidth;
    sSigFieldSettings.Height            = sigHeight;
    sSigFieldSettings.AppearanceMask    = appearanceMask;
    sSigFieldSettings.SignatureType     = SAPI_ENUM_SIGNATURE_DIGITAL;
    sSigFieldSettings.DependencyMode    = SAPI_ENUM_DEPENDENCY_MODE_INDEPENDENT;
    swprintf((wchar_t*)sSigFieldSettings.TimeFormat.DateFormat, dateFormat);
    swprintf((wchar_t*)sSigFieldSettings.TimeFormat.TimeFormat, timeFormat);
    sSigFieldSettings.TimeFormat.ExtTimeFormat = SAPI_ENUM_EXTENDED_TIME_FORMAT_GMT;    // Display GMT offset

    // Set signature clear policy
    SAPI_CUSTOM_FIELD_ELEMENTS_STRUCT sCustomFieldStruct;
    memset(&sCustomFieldStruct, 0, sizeof(SAPI_CUSTOM_FIELD_ELEMENTS_STRUCT));
    sCustomFieldStruct.StructLen = sizeof(SAPI_CUSTOM_FIELD_ELEMENTS_STRUCT);
    sCustomFieldStruct.NumOfElements = 1;
    sCustomFieldStruct.CustomFieldsArray[0].ID = SAPI_ENUM_SIG_FIELD_SETTING_CLEAR_PERMIT;
    sCustomFieldStruct.CustomFieldsArray[0].Type = SAPI_ENUM_DATA_TYPE_DWORD;
    sCustomFieldStruct.CustomFieldsArray[0].Value = (unsigned char*)&sigClearPolicy;
    sCustomFieldStruct.CustomFieldsArray[0].ValueLen = sizeof(int);

    sSigFieldSettings.ExtendedInfo = &sCustomFieldStruct;

    // Create and sign a new signature field in the document
    if ( SAPI_OK != (rc = SAPISignatureFieldCreateSign (
        hSession,                       // Session Handle
        SAPI_ENUM_FILE_ADOBE,           // Type of the file to sign - PDF
        (SAPI_LPCWSTR)filePath,         // Path to PDF file to sign
        &sSigFieldSettings,             // Signature Field details
        0,                              // Flags
        NULL,                           // Credentials (only if prompt-for-sign feature is enabled)
        0)))                            // Credentials length
    {
        SAPILogoff(hSession);           // Release user context
        SAPIHandleRelease (hSession);   // Release memory allocated for Session Handle
        printf("Error on SAPISignatureFieldCreateSign, rc = 0x%x, Extended error 0x%x\n", rc, SAPIExtendedLastErrorGet());
        return -1;
    }

    // Release all memory allocations
    SAPILogoff(hSession);               // Release user context
    SAPIHandleRelease (hSession);       // Release Session Handle

    printf ("The file has been successfully signed!\n");

    return 0;
}

使用CoSign Signature API创建签名字段时设置清除策略

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