将用户添加到加密文件
本主题中的代码示例使用 AddUsersToEncryptedFile 函数将新用户添加到现有加密文件。 它要求用户的加密文件系统 (来自 Active Directory) 的 EFS) 证书 (存在于受信任的人员用户证书存储中。
此示例向加密文件添加新的数据恢复字段。 因此，新添加的用户可以解密加密的文件。 调用方必须已以原始所有者、数据恢复代理或以前添加到加密文件的用户身份访问加密文件。
//-------------------------------------------------------------------
//
// Adduser.c: adds a user to an encrypted file.
//
// Note: Build project must link Crypt32.lib
//-------------------------------------------------------------------
#define UNICODE 1
#include <Windows.h>
#include <malloc.h>
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <wincrypt.h>
#include <winefs.h>
#pragma comment(lib, "Advapi32.lib")
#pragma comment(lib, "Crypt32.lib")
//-------------------------------------------------------------------
// Utility function that outputs this application's usage
// instructions.
//
VOID usage(LPWSTR wszAppName)
{
wprintf(L"\n%s: adds users to encrypted files.\n", wszAppName);
wprintf(L"\nUsage:\tadduser <file> <user name> <subject name>\n\n");
wprintf(L"\t<file> is the name of the file\n");
wprintf(L"\t<user name> is the name of the user's account\n");
wprintf(L"\t\tExample: for name@example.com, use \"name\"\n");
wprintf(L"\t<subject name> is the \"IssuedTo\" name on the ");
wprintf(L"certificate\n\t\tfrom the TrustedPeople store.\n");
exit(1);
}
VOID ErrorExit(LPWSTR wszErrorMessage, DWORD dwErrorCode);
void __cdecl wmain(int argc, wchar_t *argv[])
{
LPWSTR wszFile = NULL;
LPWSTR wszAccount = NULL;
LPWSTR wszSubject = NULL;
PSID pSid = NULL;
DWORD cbSid = 0;
LPWSTR wszDomain = NULL;
DWORD cchDomain = 0;
SID_NAME_USE SidType = SidTypeUser;
HCERTSTORE hStore = NULL;
PCCERT_CONTEXT pCertContext = NULL;
PENCRYPTION_CERTIFICATE pEfsEncryptionCert = NULL;
PENCRYPTION_CERTIFICATE_LIST pEfsEncryptionCertList = NULL;
DWORD dwResult = ERROR_SUCCESS;
// Simple check whether to explain usage to the user.
//
if(argc !=4)
{
usage(argv[0]);
}
// TODO: Check the parameters for correctness.
//
wszFile = argv[1];
wszAccount = argv[2];
wszSubject = argv[3];
// First, look up the user's SID using the specified account name.
// Call LookupAccountName twice; first to find the size of the
// SID, and a second time to retrieve the SID.
//
LookupAccountName(NULL,wszAccount,pSid,&cbSid,
wszDomain,&cchDomain,&SidType);
if(0 == cbSid)
{
ErrorExit(L"LookupAccountName did not return the SID size.",
GetLastError());
}
pSid = (PSID)malloc(cbSid);
if(!pSid)
{
ErrorExit(L"Failed to allocate SID.", GetLastError());
}
wszDomain = (LPWSTR)malloc(cchDomain * sizeof(WCHAR));
if(!wszDomain)
{
ErrorExit(L"Failed to allocate string.", GetLastError());
}
if(!LookupAccountName(NULL,wszAccount,pSid,&cbSid,
wszDomain,&cchDomain,&SidType))
{
ErrorExit(L"LookupAccountName failed.", GetLastError());
}
// Obtain the user's certificate.
// Search the TrustedPeople store for the specified subject name.
// Anyone who has encrypted a file on the computer has an
// encryption certificate placed the TrustedPeople store by the
// system. It is likely that the user has a matching private key.
//
hStore = CertOpenSystemStore( (HCRYPTPROV)NULL,L"TrustedPeople");
if (! hStore)
{
ErrorExit(L"OpenSystemStore failed.", GetLastError());
}
pCertContext = CertFindCertificateInStore( hStore,
X509_ASN_ENCODING | PKCS_7_ASN_ENCODING,
0,
CERT_FIND_SUBJECT_STR,
(VOID*)wszSubject,
NULL);
if(!pCertContext)
{
ErrorExit(L"FindCertificateInStore failed.", GetLastError());
}
// Create the ENCRYPTION_CERTIFICATE using the cert context and
// the user's SID.
//
pEfsEncryptionCert = (PENCRYPTION_CERTIFICATE)
malloc(sizeof(ENCRYPTION_CERTIFICATE));
if(!pEfsEncryptionCert)
{
ErrorExit(L"Failed to allocate structure.", GetLastError());
}
pEfsEncryptionCert->cbTotalLength =
sizeof(ENCRYPTION_CERTIFICATE);
pEfsEncryptionCert->pUserSid = (SID *)pSid;
pEfsEncryptionCert->pCertBlob = (PEFS_CERTIFICATE_BLOB)
malloc(sizeof(EFS_CERTIFICATE_BLOB));
if(!pEfsEncryptionCert->pCertBlob)
{
ErrorExit(L"Failed to allocate cert blob.", GetLastError());
}
pEfsEncryptionCert->pCertBlob->dwCertEncodingType =
pCertContext->dwCertEncodingType;
pEfsEncryptionCert->pCertBlob->cbData =
pCertContext->cbCertEncoded;
pEfsEncryptionCert->pCertBlob->pbData =
pCertContext->pbCertEncoded;
// AddUsersToEncryptedFile takes an ENCRYPTION_CERTIFICATE_LIST;
// create one with only one ENCRYPTION_CERTIFICATE in it.
//
pEfsEncryptionCertList = (PENCRYPTION_CERTIFICATE_LIST)
malloc(sizeof(ENCRYPTION_CERTIFICATE_LIST));
if(!pEfsEncryptionCertList)
{
ErrorExit(L"Failed to allocate structure.", GetLastError());
}
pEfsEncryptionCertList->nUsers = 1;
pEfsEncryptionCertList->pUsers = &pEfsEncryptionCert;
// Call the API to add the user.
//
dwResult =
AddUsersToEncryptedFile(wszFile,pEfsEncryptionCertList);
if(ERROR_SUCCESS == dwResult)
{
wprintf(L"The user was successfully added to the file.\n");
}
else
{
ErrorExit(L"AddUsersToEncryptedFile failed.", dwResult);
}
// Clean up all allocated resources.
//
if(wszDomain) free(wszDomain);
if(pSid) free(pSid);
if(pCertContext) CertFreeCertificateContext(pCertContext);
if(hStore) CertCloseStore(hStore,CERT_CLOSE_STORE_FORCE_FLAG);
if(pEfsEncryptionCertList)
{
if (pEfsEncryptionCertList->pUsers)
{
if(pEfsEncryptionCertList->pUsers[0])
{
if((pEfsEncryptionCertList->pUsers[0])->pCertBlob)
free((pEfsEncryptionCertList->pUsers[0])->pCertBlob);
free(pEfsEncryptionCertList->pUsers[0]);
}
free(pEfsEncryptionCertList->pUsers);
}
free(pEfsEncryptionCertList);
}
wprintf(L"The program ran to completion without error.\n");
exit(0);
}
//------------------------------------------------------------------
// A simple error handling function that prints an error message
// and exits the program.
//
// TODO: Replace this function with one that has better error
// reporting.
//
VOID ErrorExit(LPWSTR wszErrorMessage, DWORD dwErrorCode)
{
fwprintf(stderr, L"An error occurred in running the program. \n");
fwprintf(stderr, L"%s\n", wszErrorMessage);
fwprintf(stderr, L"Error code: 0x%08x\n", dwErrorCode);
fwprintf(stderr, L"Program terminating. \n");
exit(1);
}
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