一:SSL协议是什么?
SSL是一种加密传输协议.引用网上一段话:SSL 是Secure socket Layer英文缩写,它的中文意思是安全套接层协议,指使用公钥和私钥技术组合的安全网络通讯协议。SSL协议是网景公司(Netscape)推出的基于 WEB应用的安全协议,SSL协议指定了一种在应用程序协议(如Http、Telenet、NMTP和FTP等)和TCP/IP协议之间提供数据安全性分层的机制,它为TCP/IP连接提供数据加密、服务器认证、消息完整性以及可选的客户机认证,主要用于提高应用程序之间数据的安全性,对传送的数据进行加密和隐藏,确保数据在传送中不被改变,即确保数据的完整性。

二:Delphi中如何使用SSL协议?
要使用SSL协议,有几种方法,一种是根据SSL协议文档自己实现,另外一种是调用第三方的开发库.现在一般的开发者(无论是Delphi还是VC)都是使用开源的OpenSSL库.本文的介绍都是基于OpenSSL的.
Delphi中的Indy组件本身就是支持OpenSSL的.例如,对于IdTCPClient,只需要拖一个IdSSLIOHandlerSocket控件到窗口,然后将IdTCPClient的IOHandler指向它即可.不过IdSSLOpenSSLHeaders.pas的声明比较老,是基于OpenSSL 0.9.4的,而0.9.4的DLL文件现在比较少见了.现在一般使用OpenSSL 0.9.7i.(可以打开IdSSLOpenSSLHeaders.pas,搜索版本,老版本是这样的:

OPENSSL_OPENSSL_VERSION_NUMBER = $00904100;
OPENSSL_OPENSSL_VERSION_TEXT = 'OpenSSL 0.9.4 09 Aug 1999'; {Do not localize}

0.9.4和0.9.7i的区别是0.9.4的部分函数位于ssleay32.dll中,而0.9.7i则抛弃了此DLL.网上有很多修改过的基于0.9.7i版本的IdSSLOpenSSLHeaders.pas,本文的演示代码主要是基于0.9.7i.

三:SSL客户端编程实例

使用OpenSSL之前,得先装载SSL库.直接调用Load函数即可完成:

if not uIdSSLOpenSSLHeaders.Load then //装载ssl库
begin
Application.MessageBox('装载ssl动态库失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

然后装载错误字符库和加密算法:

IdSslLoadErrorStrings;
IdSslAddSslAlgorithms; //load所有的SSL算法

然后,初始化SSL使用的协议版本和SSL上下文:

methClient := IdSslMethodClientV23;//SSL协议有多个版本,包括SSLv2,SSLv23,SSLv3和TLSv1我们这里使用v23.
if methClient = nil then
begin
Application.MessageBox('建立SSL Client所用的method失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

ctxClient := IdSslCtxNew(methClient); //初始化上下文情景.
if ctxClient = nil then
begin
Application.MessageBox('创建客户端SSL_CTX失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

上下文情景初始化完毕后,就可以进行socket通信了.首先创建一个正常的socket,连接到目的地址,然后申请一个SSL会话的环境:
sslClient := IdSslNew(ctxClient);
if sslClient = nil then
begin
closesocket(ClientSocket);
Application.MessageBox('申请SSL会话的环境失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

然后绑定套接字:
IdSslSetFd(sslClient, ClientSocket);
IdSslConnect(sslClient);
成功后就可以调用IdSslRead和IdSslWrite来读写数据了.
下面我们给出一个完整的例子,用于连接安全焦点的论坛首页.此程序用到一个Memo控件和一个按钮控件.注意:此代码没有做过多的错误处理,读者可以自行添加:

procedure TForm1.Button1Click(Sender: TObject);
const
//Url: string = 'https://www.xfocus.net/bbs/index.php?lang=cn';
Host: string = 'www.xfocus.net';
Port: Word = 443;
var
Wsa: TWSAData;
ctxClient: PSSL_CTX; //SSL上下文
methClient: PSSL_METHOD;
sRemoteIP: string;

ClientSocket: TSocket;
sAddr: TSockAddr;
sslClient: PSSL;
pServer_Cert: PX509;
pStr: Pchar;
buf: array[0..4095] of Char;
nRet: integer;
strSend: string;
begin
Button1.Enabled := False;

if WSAStartup($101, Wsa) <> 0 then //初始化Wsock32.dll,MakeWord(2,2),
begin
Application.MessageBox('初始化Winsock动态库失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

if not uIdSSLOpenSSLHeaders.Load then //装载ssl库
begin
Application.MessageBox('装载ssl动态库失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;
IdSslLoadErrorStrings;
IdSslAddSslAlgorithms; //load所有的SSL算法

methClient := IdSslMethodClientV23;
if methClient = nil then
begin
Application.MessageBox('建立SSL Client所用的method失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

ctxClient := IdSslCtxNew(methClient); //初始化上下文情景
if ctxClient = nil then
begin
Application.MessageBox('创建客户端SSL_CTX失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;


sRemoteIP := GetIPAddressByHost(Host);
if sRemoteIP = '' then
begin
Application.MessageBox('获取远程IP地址失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;


ClientSocket := Socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if ClientSocket = INVALID_SOCKET then
begin
Application.MessageBox('创建socket失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

FillChar(sAddr, Sizeof(TSockAddr), #0);
sAddr.sin_family := AF_INET;
sAddr.sin_addr.S_addr := inet_addr(Pchar(sRemoteIP));
sAddr.sin_port := htons(Port);

if connect(ClientSocket, sAddr, sizeof(TSockAddr)) = SOCKET_ERROR then
begin
Application.MessageBox('连接远程服务器失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

sslClient := IdSslNew(ctxClient); //申请SSL会话的环境,参数就是前面我们申请的 SSL通讯方式。返回当前的SSL 连接环境的指针。
if sslClient = nil then
begin
closesocket(ClientSocket);
Application.MessageBox('申请SSL会话的环境失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

IdSslSetFd(sslClient, ClientSocket); //绑定读写套接字
if IdSslConnect(sslClient) = -1 then
begin
IdSslFree(sslClient);
closesocket(ClientSocket);
Application.MessageBox('绑定读写套接字失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

Memo1.Lines.Add(Format('SSL连接使用的算法为:%s', [IdSSLCipherGetName(IdSSLGetCurrentCipher(sslClient))]));

pServer_Cert := IdSslGetPeerCertificate(sslClient);
if (pServer_Cert <> nil) then
begin
Memo1.Lines.Add('服务端证书:');
pStr := IdSslX509NameOneline(IdSslX509GetSubjectName(pServer_Cert), nil, 0);
if pStr <> nil then Memo1.Lines.Add(Format('主题: %s', [pStr]));
pStr := IdSslX509NameOneline(IdSslX509GetIssuerName(pServer_Cert), nil, 0);
if pStr <> nil then Memo1.Lines.Add(Format('发行者: %s', [pStr]));
end
else
begin
Memo1.Lines.Add('客户端没有证书.');
end;
Memo1.Lines.Add('');

strSend := 'GET /bbs/index.php?lang=cn HTTP/1.1'#$D#$A +
'Accept: */*'#$D#$A +
'Accept-Language: zh-cn'#$D#$A +
'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)'#$D#$A +
'Host: ' + Host + #$D#$A +
'Connection: Keep-Alive'#$D#$A#$D#$A;

if IdSslWrite(sslClient, @strSend[1], Length(strSend)) <= 0 then
begin
IdSslFree(sslClient);
closesocket(ClientSocket);
Application.MessageBox('发送失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

FillChar(buf, sizeof(buf), #0);
nRet := IdSslRead(sslClient, buf, sizeof(buf));
while nRet > 0 do
begin
Memo1.Lines.Add(StrPas(Buf));
FillChar(buf, sizeof(buf), #0);
Application.ProcessMessages;
nRet := IdSslRead(sslClient, buf, sizeof(buf));
end;

IdSslFree(sslClient);
closesocket(ClientSocket);
if ctxClient <> nil then IdSslCtxFree(ctxClient);
WSACleanup; //结束对WSocket32.dll调用
Button1.Enabled := True;
end;

完整代码下载地址:http://www.138soft.com/download/ssldemo_client.rar

四:SSL服务端编程实例

服务端没有什么好讲的,跟客户端不同的地方,在于初始化时需要加载证书,然后Accept后需要再用IdSslAccept关联.关于如何用Delphi生成证书文件,详见下一讲.下面直接贴代码:

var
Form1: TForm1;
g_Wsa: TWSAData;
g_ServerSocketMain: TSocket = INVALID_SOCKET;
g_ctxServer: PSSL_CTX = nil; //SSL上下文
g_methServer: PSSL_METHOD = nil;
g_DebugCritSec: TRTLCriticalSection;
g_hAcceptThread: THandle = 0;
g_Start: BOOL = False;

implementation

{$R *.dfm}

function AcceptThread(lp: Pointer): DWORD; stdcall;
var
nAddrLen: integer;
sdClient: TSocket;
sAddrs: TSockAddr;
nErrorCode: integer;
sslServer: PSSL;
pClient_Cert: PX509;
pStr: Pchar;
nRet: integer;
buf: array[0..4095] of Char;
strBody, strSend: string;
begin
Result := 0;

while g_Start do
begin
nAddrLen := sizeof(TSockAddr);
sdClient := accept(g_ServerSocketMain, @sAddrs, @nAddrLen);
if (sdClient = INVALID_SOCKET) then
begin
nErrorCode := WSAGetLastError;
EnterCriticalSection(g_DebugCritSec);
if g_Start then Form1.Memo1.Lines.Add(Format('发生错误.错误代码:%d', [nErrorCode]));
LeaveCriticalSection(g_DebugCritSec);
end
else
begin
EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add(Format('新连接.客户端IP:%s', [inet_ntoa(sAddrs.sin_addr)]));
LeaveCriticalSection(g_DebugCritSec);


sslServer := IdSslNew(g_ctxServer); //申请SSL会话的环境,参数就是前面我们申请的 SSL通讯方式,返回当前的SSL 连接环境的指针.
if sslServer = nil then
begin
closesocket(sdClient);
Continue;
end;

IdSslSetFd(sslServer, sdClient); //绑定读写套接字

nRet := IdSslAccept(sslServer);
if (nRet = -1) then
begin
closesocket(sdClient);
IdSslShutdown(sslServer);
IdSslFree(sslServer);
Continue;
end;

EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add(Format('SSL连接使用的算法为:%s', [IdSSLCipherGetName(IdSSLGetCurrentCipher(sslServer))]));
LeaveCriticalSection(g_DebugCritSec);

pClient_Cert := IdSslGetPeerCertificate(sslServer);
if (pClient_Cert <> nil) then
begin
EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add('客户端证书:');
LeaveCriticalSection(g_DebugCritSec);
pStr := IdSslX509NameOneline(IdSslX509GetSubjectName(pClient_Cert), nil, 0);
if pStr = nil then Exit;
EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add(Format('主题: %s', [pStr]));
LeaveCriticalSection(g_DebugCritSec);
IdSslFree(pStr);
pStr := IdSslX509NameOneline(IdSslX509GetIssuerName(pClient_Cert), nil, 0);
if pStr = nil then Exit;
IdSslFree(pStr);
EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add(Format('发行者: %s', [pStr]));
LeaveCriticalSection(g_DebugCritSec);
IdSslFree(pStr);
IdSslFree(pClient_Cert);
end
else
begin
EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add('客户端没有证书.');
LeaveCriticalSection(g_DebugCritSec);
end;


FillChar(buf, sizeof(buf), #0);
nRet := IdSslRead(sslServer, buf, sizeof(buf));
if nRet <= 0 then
begin
closesocket(sdClient);
sdClient := INVALID_SOCKET;
IdSslShutdown(sslServer);
IdSslFree(sslServer);
sslServer := nil;
end
else
begin
EnterCriticalSection(g_DebugCritSec);
Form1.Memo1.Lines.Add('客户端发送请求:'#$D#$A + StrPas(buf));
LeaveCriticalSection(g_DebugCritSec);
end;

strBody := 'Your IP is:' + inet_ntoa(sAddrs.sin_addr);

strSend := 'HTTP/1.1 200 OK'#$D#$A +
'Content-Length: ' + IntToStr(Length(strBody)) + #$D#$A +
'Content-Type: text/html'#$D#$A#$D#$A + strBody;

IdSslWrite(sslServer, @strSend[1], Length(strSend));

closesocket(sdClient);
IdSslShutdown(sslServer);
IdSslFree(sslServer);
end;
end;
g_hAcceptThread := 0;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
sAddr: TSockAddr;
dwThreadID: DWORD;
begin
Button1.Enabled := False;

//Create a socket
g_ServerSocketMain := Socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if g_ServerSocketMain = INVALID_SOCKET then
begin
MessageBox(0, '创建Socket失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Application.Terminate;
Exit;
end;

//Bind Port
FillChar(sAddr, Sizeof(TSockAddr), #0);
sAddr.sin_family := AF_INET;
sAddr.sin_port := htons(StrToIntDef(Trim(Edit1.Text), 443));
sAddr.sin_addr.S_addr := INADDR_ANY;

if Bind(g_ServerSocketMain, sAddr, Sizeof(TSockAddr)) = SOCKET_ERROR then
begin
MessageBox(0, '绑定端口失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Application.Terminate;
Exit;
end;

//listen
if listen(g_ServerSocketMain, SOMAXCONN) = SOCKET_ERROR then
begin
MessageBox(0, '监听端口失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Application.Terminate;
Exit;
end;
g_Start := TRUE;
g_hAcceptThread := CreateThread(nil, 0, @AcceptThread, nil, 0, dwThreadId);
end;


procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
g_Start := FALSE;
if g_ServerSocketMain <> INVALID_SOCKET then
begin
closesocket(g_ServerSocketMain);
g_ServerSocketMain := INVALID_SOCKET;
end;

if (g_hAcceptThread <> 0) then
begin
WaitForSingleObject(g_hAcceptThread, INFINITE);
CloseHandle(g_hAcceptThread);
g_hAcceptThread := 0;
end;
end;

initialization

if WSAStartup($101, g_Wsa) <> 0 then //初始化Wsock32.dll,2.2版本可以使用MakeWord(2,2),
begin
MessageBox(0, '初始化Winsock动态库失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

if not Load then //装载ssl库失败
begin
MessageBox(0, '装载ssl动态库失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;
IdSslLoadErrorStrings;
IdSslAddSslAlgorithms; //load所有的SSL算法.

//========================== 初始化SSL Server ================================
g_methServer := IdSslMethodV23; //建立SSL所用的method.
if g_methServer = nil then
begin
MessageBox(0, '建立SSL Server所用的method失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;
g_ctxServer := IdSslCtxNew(g_methServer); //初始化上下文情景.
if g_ctxServer = nil then //创建SSL_CTX失败
begin
MessageBox(0, '创建服务端SSL_CTX失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;

if IdSslCtxUseCertificateFile(g_ctxServer, Pchar(ExtractFilePath(GetModuleName(HInstance)) + 'UserCert.pem'), OPENSSL_SSL_FILETYPE_PEM) <= 0 then //加载证书失败
begin
MessageBox(0, '加载证书失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;
if IdSslCtxUsePrivateKeyFile(g_ctxServer, Pchar(ExtractFilePath(GetModuleName(HInstance)) + 'UserKey.pem'), OPENSSL_SSL_FILETYPE_PEM) <= 0 then //加载私钥失败
begin
MessageBox(0, '加载私钥失败!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;
if not IdSslCtxCheckPrivateKeyFile(g_ctxServer) = 0 then //密钥证书不匹配
begin
MessageBox(0, '密钥和证书不匹配!', '错误', MB_ICONEXCLAMATION + MB_TOPMOST);
Halt;
end;
InitializeCriticalSection(g_DebugCritSec);
finalization
if g_ctxServer <> nil then IdSslCtxFree(g_ctxServer);
DeleteCriticalSection(g_DebugCritSec);
WSACleanup; //结束对WSocket32.dll调用
end.


完整代码下载地址:http://www.138soft.com/download/ssldemo_server.rar

实际上,稍微用心的人结合第一讲的客户端例子,已经可以写出中间人欺骗程序了.


ssldemo_client.rar
Last modification:August 16th, 2009 at 12:30 pm
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