本文首先感谢 Apple 开发者论坛的eskimo1，他是我见过的最热心肠的人，对任何人他都不吝于给予无私帮助。
服务器生成PKCS12证书库，并通过servlet导出为DER客户端证书（含一个密钥和一个证书）。iPhone从服务器下载证书后，如何进行验证？
一、 生成证书
假设密钥库为dlt.p12，库密码ipcc@95598，有效期1天，则命令为：
keytool -genkey -v -alias root -keyalg RSA -storetype PKCS12 -keystore dlt.p12 -dname "CN=www.handtimes.com,OU=ipcc,O=云电同方,L=昆明,ST=云南,C=中国" -storepass ipcc@95598 -keypass ipcc@95598
生成客户端用的证书：
keytool -genkey -v -alias p12client -keyalg RSA -storetype PKCS12 -keystore dlt.p12 -dname "CN=www.handtimes.com,OU=ipcc,O=云电同方,L=昆明,ST=云南,C=中国" -storepass ipcc@95598 -keypass 123456 -validity 1
要查看已生成的证书，用下面的命令：
keytool -list -v -alias p12client -keystore dlt.p12 -storepass ipcc@95598 -storetype PKCS12
或者：
keytool -list -v -keystore IPCCCA – dlt.p12 ipcc@95598 -storetype PKCS12
如果需要将p12证书导出为.cer格式，可以使用命令：
keytool -export -alias p12client -keystore dlt.p12 -storetype PKCS12 -storepass ipcc@95598 -rfc -file p12.cer
查看.cer文件：
keytool -printcert -v -file /Users/kmyhy/Desktop/client.cer
如果需要将keystore中的私钥导出为.p12格式：
Keytool.exe -importkeystore -srckeystore IPCCCA -srcstoretype jks -srcstorepass ipcc@95598 -srcalias p12client -destkeystore dltclient.p12 -deststoretype pkcs12 -deststorepass ipcc@95598 -destkeypass 123456 – validity 3
注意，keytool用的是jdk1.6提供的版本。此时命令提示忽略用户输入的destkeypass密码：
重新输入密码123456，回车，将在用户主目录下生成dltclient.p12文件。
查看dltclient.p12内容：
keytool.exe -list -keystore dltclient.p12 -storepass ipcc@95598 -storetype pkcs12
可以看到如下输出：
可以看到其中包含了证书和私钥,并且其认证指纹是和IPCCCA中的一模一样的。
一、 提供证书下载
先把生成的p12证书库dlt.p12放到服务器目录下。
新建一个Servlet：GetP12Cert。
public class GetP12Cert extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final int max_days =1;
/**
* @see HttpServlet#HttpServlet()
*/
public GetP12Cert() {
super ();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename= "C://Documents and Settings//Administrator//dlt.cer" ;
String pass= "ipcc@95598" ;
Pkcs12Manager man= null ;
String alias= "p12client" ;
String keypass= "123456" ;
try {
man= new Pkcs12Manager( new File(filename),pass);
man.updateExpiration(alias, keypass, max_days );
exportCert(man,alias,response);
// man.saveCert(alias, "123456");
//man.saveCert(alias, "123456");
} catch (Exception e){
e.printStackTrace();
}
}
// 导出证书
private void exportCert(Pkcs12Manager man,String alias,HttpServletResponse response){
OutputStream out= null ;
try {
Certificate cert = man. keyStore .getCertificate(alias);
// 得到证书内容（以编码过的格式）
byte [] buf = cert.getEncoded();
// 写证书文件
response.setContentType( "application/x-download" );
response.addHeader( "Content-Disposition" , "attachment;filename="
+ man. file .getName());
out= response.getOutputStream();
out.write(buf);
}
catch (Exception e){e.printStackTrace();}
finally {
try {
out.close();
} catch (Exception e){
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
}
其中，Pkcs12Manager是一个javabean，提供了对PKCS12证书的读取、修改操作，代码如下：
public class Pkcs12Manager {
public File file ;
public KeyStore keyStore ;
private char [] storePass ;
public Pkcs12Manager(File file, String pass) throws IOException, Exception {
this . file = file;
this . storePass =pass.toCharArray();
getKeyStore(); // 加载 KeyStore 文件
}
// 加载 KeyStore 文件
public synchronized KeyStore getKeyStore() throws IOException, Exception {
if ( keyStore == null ) {
FileInputStream fin = new FileInputStream( file );
KeyStore store = KeyStore.getInstance ( "PKCS12" );
try {
store.load(fin, storePass );
}
finally {
try {
fin.close();
} catch (IOException e) { }
}
keyStore = store;
}
return keyStore ;
}
// 读取 alias 指定的证书内容
public X509CertInfo getX509CertInfo(String alias) throws Exception {
X509CertImpl cimp=getX509CertImpl(alias);
// 获取 X509CertInfo 对象
return (X509CertInfo) cimp.get(X509CertImpl. NAME
+ "." + X509CertImpl. INFO );
}
// 根据 alias 获取 X509CertImpl 对象
private X509CertImpl getX509CertImpl(String alias) throws Exception{
Certificate c = keyStore .getCertificate(alias); // 读取证书
// 从待签发的证书中提取证书信息
byte [] enc = c.getEncoded(); // 获取 证书内容（经过编码的字节）
X509CertImpl cimp= new X509CertImpl(enc); // 创建 X509CertImpl 象
return cimp;
}
// 修改证书过期时间 : 过期时间顺延 n 天
public void updateExpiration(String alias,String keypass, int n) throws Exception{
System. out .println(getExpiration(alias));
X509CertInfo cinfo=getX509CertInfo(alias); // 获取 X509CertInfo 对象
X509CertImpl cimp=getX509CertImpl(alias); // 获取 X509CertImpl 对象
String sigAlgrithm=cimp.getSigAlgName(); // 获取签名算法
CertificateValidity cv=(CertificateValidity)cinfo.get(X509CertInfo. VALIDITY );
// 有效期为当前日期后延 n 天
Date d2 = new Date( new Date().getTime() + n * 24 * 60 * 60 * 1000L);
System. out .println( "new date:" +d2.toString());
// 创建有效期对象
cv.set(CertificateValidity. NOT_AFTER , d2);
cinfo.set(X509CertInfo. VALIDITY , cv); // 设置有效期
saveCert(alias,keypass,cinfo,sigAlgrithm);
System. out .println(getExpiration(alias));
}
// 读取证书过期时间
public String getExpiration(String alias) throws Exception{
X509CertInfo cinfo=getX509CertInfo(alias);
CertificateValidity cv=(CertificateValidity)cinfo.get(X509CertInfo. VALIDITY );
// 创建有效期对象
Date d=(Date)cv.get(CertificateValidity. NOT_AFTER );
return d.toString();
}
// 存储证书
private void saveCert(String alias,String keypass,
X509CertInfo cinfo,String algrithm) throws Exception{
// 从密钥库中读取 CA 的私钥
PrivateKey pKey = (PrivateKey) keyStore .getKey(alias, keypass.toCharArray());
X509CertImpl cert = new X509CertImpl(cinfo); // 新建证书
cert.sign(pKey, algrithm); // 使用 CA 私钥对其签名
// 获取别名对应条目的证书链
Certificate[] chain = new Certificate[] { cert };
// 向密钥库中添加条目 , 使用已存在别名将覆盖已存在条目
keyStore .setKeyEntry(alias, pKey, keypass.toCharArray(), chain);
// 将 keystore 存储至文件
FileOutputStream fOut = new FileOutputStream( file );
keyStore .store(fOut, storePass );
fOut.close();
}
// 获取签名算法
public String getSigAlgName(String alias) throws Exception{
Certificate c = keyStore .getCertificate(alias); // 读取证书
// 获取 证书内容（经过编码的字节）
byte [] enc = c.getEncoded();
// 创建 X509CertImpl 对象
X509CertImpl cimp2 = new X509CertImpl(enc);
String sigAlgrithm=cimp2.getSigAlgName();
return sigAlgrithm;
}
}
将上述Servlet 和javabean 部署到服务器中。这样，通过访问http://localhost/GetP12Cert 就可以获得一个有效的证书dlt.cer。
二、 证书的验证
假设我们的客户端为iPhone客户端。则在iPhone中进行证书验证的代码为：
NSString * path=[[ NSBundle mainBundle ] pathForResource : @"dlt.cer" ofType : nil ];
// EfficientDate 参数为任意一个有效的日期（在证书有效期之内）
MyTrustService * myTrust=[[ MyTrustService alloc ]
initWithFilename :path EfficientDate : @"2011-05-10 0:0:0" ];
ValuateResult ret=[myTrust trustValuate :[[ NSDate alloc ] init ]];
switch (ret) {
case ValuateResultOK :
NSLog ( @" 证书有效 " );
break ;
case ValuateResultEXPIRED :
NSLog ( @" 证书已过期 " );
break ;
default :
NSLog ( @" 证书校验失败 " );
break ;
}
[myTrust release ];
其中MyTrustService代码为（注意导入security.framework框架）：
#import <Foundation/Foundation.h>
#import <Security/Security.h>
static const char * kTrustNames [ 8 ] = {
"Invalid" ,
"Proceed" ,
"Confirm" ,
"Deny" ,
"Unspecified" ,
"RecoverableTrustFailure" ,
"FatalTrustFailure" ,
"OtherError"
};
typedef enum
{
ValuateResultINVALID = 0 , // 评估结果无效，表明评估出错或未经过评估
ValuateResultFAILED , // 证书签名无效
ValuateResultEXPIRED , // 证书过期
ValuateResultOK // 证书有效
} ValuateResult;
@interface MyTrustService : NSObject {
NSString * file ;
NSDate * efficientDate ;
}
-( id )initWithFilename:( NSString *)filename EfficientDate:( NSString *)date;
-( ValuateResult )trustValuate:( NSDate *)date;
-( ValuateResult )valuate:( SecCertificateRef )cert Trust:( SecTrustRef )trust Date:( NSDate *)date;
@end
#import "MyTrustService.h"
@implementation MyTrustService
-( id )initWithFilename:( NSString *)filename EfficientDate:( NSString *)date{
if ( self =[ super init ]) {
file =filename;
// 设置有效日期，注意，第 2 个参数是一个有效的证书日期，只要这个日期对证书而言是有效的就行
efficientDate =[[ NSDate alloc ] initWithString :date];
}
return self ;
}
-( ValuateResult )trustValuate:( NSDate *)date{
ValuateResult ret;
OSStatus err;
NSData * certData;
SecCertificateRef cert;
SecPolicyRef policy;
SecTrustRef trust;
assert ( file != nil );
assert (date != nil );
// 从文件获得 DER 数据
certData = [ NSData dataWithContentsOfFile : file ];
assert (certData != nil );
// 从 NSData 获得 Certificate 对象
cert = SecCertificateCreateWithData ( NULL , ( CFDataRef ) certData);
assert (cert != NULL );
// 获得 x509 policy
policy = SecPolicyCreateBasicX509 ();
assert (policy != NULL );
// 获得 Trust 对象
err = SecTrustCreateWithCertificates (cert, policy, &trust);
assert (err == noErr );
// 由于是自签名证书，需要将锚证书设置为要验证的证书自己。注意，这样将使所有除了参数指定的锚证书之外的所有锚证书无效
err = SecTrustSetAnchorCertificates (trust, ( CFArrayRef ) [ NSArray arrayWithObject :( id ) cert]);
assert (err == noErr );
// 调用 valuate 方法进行评估
ret=[ self valuate :cert Trust :trust Date :date];
// 评估结束，把 SecTrustSetAnchorCertificates 指定的锚证书失效，于是所有锚证书又可被信任了
err= SecTrustSetAnchorCertificatesOnly (trust, NO );
CFRelease (trust);
CFRelease (policy);
CFRelease (cert);
return ret;
}
-( ValuateResult )valuate:( SecCertificateRef )cert Trust:( SecTrustRef )trust Date:( NSDate *)date{
ValuateResult ret;
OSStatus err;
SecTrustResultType result;
err = SecTrustSetVerifyDate (trust, ( CFDateRef ) date);
assert (err == noErr );
CFAbsoluteTime trustTime;
trustTime = SecTrustGetVerifyTime (trust);
err = SecTrustEvaluate (trust, &result);
assert (err == noErr );
if (result < ( sizeof ( kTrustNames ) / sizeof (* kTrustNames ))) { // if(result < 8)
if (result== 5 ) { // if result=RecoverableTrustFailure
// 设了个有效的日期，进行再次评估
err= SecTrustSetVerifyDate (trust, ( CFDateRef ) efficientDate );
assert (err== noErr );
err= SecTrustEvaluate (trust, &result);
assert (err == noErr );
if (result== 4 ) { // if result=Unspecified,
// 返回证书已过期，这里我们假设把证书尚未生效的情况也算作过期
ret= ValuateResultEXPIRED ;
}
} else if (result== 4 ) { // 如果第 1 次就通过评估，证书有效
ret= ValuateResultOK ;
} else {
ret= ValuateResultFAILED ; // 证书 无效
}
} else {
NSLog ( @"result = unknown (%zu)" , ( size_t ) result);
}
return ret;
}
-( void )dealloc{
[ efficientDate release ];
[ super dealloc ];
}
@end