问：我在服务器上用 CreateFileMapping 创建了一段共享内存。让这个exe始终在服务器上跑。 同时，别的用户在客户端用IE访问服务器，将要查询的数据通过C#制作的网页提交上来，服务器得到网页参数后，建立一个COM对象访问上一个exe的共享内存，然后将在共享内存中的查询结果返回给客户。 问题是现在这个COM无法用openmapping访问exe的共享内存，提示 访问拒绝 。而我在服务器上随便建议一个工程编译成exe,文件就可访问这段共享内存!!为何在网页中就不成？COM难道要有什么 权限 设置.两个进程之间的权限整合方法是什么？怎么用DACL?
我用ATL写了一个Service,在这个Service中，我创建了一块共享内存(Memory Mapping)和一个Mutex然后我在另一个普通程序中去访问这块共享内存和Mutex,但是，我用CreateMutex打开Mutex失败，GetLastError()返回5，含义是访问被拒绝！！同样，我在用MapViewOfFile时，也得到同样的错误！！！！！！
我已经知道原因是因为在创建共享内存和Mutext时，SECURITY_ATTRIBUTES我设为NULL!!!
但是我没有解决的方法,希望各位大虾帮帮忙！
答：检查服务运行所使用的用户的权限。通常，为了安全起见，服务进程的拥有者权限是很低的。为了让服务进程访问对象，你需要在创建共享内存时指定一个更加广泛的的安全描述符，增加一个新的访问控制项目(ACE)给你的ASP进程的拥有者。默认的访问控制列表(ACL)只包含创建者和管理员组。
下列代码创建一个所有用户都可以访问的安全描述符。你可以在创建共享内存时使用这个安全描述符。 CShareRestrictedSD ShareRestrictedSD; hMapFile = CreateFileMapping(INVALID_HANDLE_VALUE, // Current file handle. ShareRestrictedSD.GetSA(), // Default security. // NULL, PAGE_READWRITE, // Read/write permission. 0, // Max. object size. FileSize, // Size of hFile. MapName); // Name of mapping object.
class CShareRestrictedSD {public: CShareRestrictedSD(); virtual ~CShareRestrictedSD(); SECURITY_ATTRIBUTES* GetSA();protected: PVOID ptr; SECURITY_ATTRIBUTES sa; SECURITY_DESCRIPTOR sd;};//如果这家伙起作用，那么它的作者是jiangsheng；//如果这家伙一点用没有，那我不知道它的作者。PVOID BuildRestrictedSD(PSECURITY_DESCRIPTOR pSD) {
DWORD dwAclLength;
PSID psidEveryone = NULL;
PACL pDACL = NULL; BOOL bResult = FALSE;
PACCESS_ALLOWED_ACE pACE = NULL;
SID_IDENTIFIER_AUTHORITY siaWorld = SECURITY_WORLD_SID_AUTHORITY ; SECURITY_INFORMATION si = DACL_SECURITY_INFORMATION; __try {
// initialize the security descriptor if (!InitializeSecurityDescriptor(pSD, SECURITY_DESCRIPTOR_REVISION)) { printf("InitializeSecurityDescriptor() failed with error %d/n", GetLastError()); __leave; }
// obtain a sid for the Authenticated Users Group if (!AllocateAndInitializeSid(&siaWorld, 1, SECURITY_WORLD_RID, 0, 0, 0, 0, 0, 0, 0, &psidEveryone)) { printf("AllocateAndInitializeSid() failed with error %d/n", GetLastError()); __leave; }
// NOTE: // // The Authenticated Users group includes all user accounts that // have been successfully authenticated by the system. If access // must be restricted to a specific user or group other than // Authenticated Users, the SID can be constructed using the // LookupAccountSid() API based on a user or group name.
// calculate the DACL length dwAclLength = sizeof(ACL) // add space for Authenticated Users group ACE + sizeof(ACCESS_ALLOWED_ACE) - sizeof(DWORD) + GetLengthSid(psidEveryone);
// allocate memory for the DACL pDACL = (PACL) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, dwAclLength); if (!pDACL) { printf("HeapAlloc() failed with error %d/n", GetLastError()); __leave; }
// initialize the DACL if (!InitializeAcl(pDACL, dwAclLength, ACL_REVISION)) { printf("InitializeAcl() failed with error %d/n", GetLastError()); __leave; } // add the Authenticated Users group ACE to the DACL with // GENERIC_READ, GENERIC_WRITE, and GENERIC_EXECUTE access if (!AddAccessAllowedAce(pDACL, ACL_REVISION, GENERIC_ALL, psidEveryone)) { printf("AddAccessAllowedAce() failed with error %d/n", GetLastError()); __leave; }
// set the DACL in the security descriptor if (!SetSecurityDescriptorDacl(pSD, TRUE, pDACL, FALSE)) { printf("SetSecurityDescriptorDacl() failed with error %d/n", GetLastError()); __leave; }
bResult = TRUE; } __finally {
if (psidEveryone) FreeSid(psidEveryone); }
if (bResult == FALSE) { if (pDACL) HeapFree(GetProcessHeap(), 0, pDACL); pDACL = NULL; }
return (PVOID) pDACL;}
// The following function frees memory allocated in the// BuildRestrictedSD() functionVOID FreeRestrictedSD(PVOID ptr) {
if (ptr) HeapFree(GetProcessHeap(), 0, ptr);
return;}
CShareRestrictedSD::CShareRestrictedSD(){ ptr=NULL; sa.nLength = sizeof(sa); sa.lpSecurityDescriptor = &sd; sa.bInheritHandle = FALSE; // build a restricted security descriptor ptr = BuildRestrictedSD(&sd); if (!ptr) { TRACE("BuildRestrictedSD() failed/n"); }}
CShareRestrictedSD::~CShareRestrictedSD(){ if(ptr){ FreeRestrictedSD(ptr); }}SECURITY_ATTRIBUTES* CShareRestrictedSD::GetSA(){ if(ptr){ return &sa; } else return NULL;}
本文来自博客，转载请标明出处：http://blog.csdn.net/jiangsheng/archive/2004/06/24/25563.aspx
