iphone开发：验证来自https url的证书信息

当用户使用网络浏览器（Safari、Chrome等）连接到“https url”时，例如：“https://encrypted.google.com”，则用户可以获得有关证书相关的信息到这样的“https url”；也就是说，在连接到url“https://encrypted.google.com”的情况下，可以验证以下证书信息：

1. Equifax 安全证书颁发机构
2. *.google.com 发布者：Google 互联网管理局。证书的到期日期。证书是否有效
3. 有关证书的更多详细信息，如签名算法、公钥信息、指纹等。

所以，问题是：“为了获取上述信息（或者至少知道证书是否有效），正确的 Objective C 函数调用是什么？”

提前致谢，

可以使用 NSURLConnection 委托方法获取证书信息：

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge

That is:

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace {
BOOL  result = [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
NSLog(@"<%p %@: %s line:%d> Result:%s", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __PRETTY_FUNCTION__, __LINE__, (result == YES) ? "YES" : "NO");
return result;
}

- (void)connection:(NSURLConnection *)connection      didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
NSArray *trustedHosts = [NSArray arrayWithObject:@"encrypted.google.com"];
BOOL isAuthMethodServerTrust = [challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
NSLog(@"<%p %@: %s line:%d> Result:%s", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __PRETTY_FUNCTION__, __LINE__, (isAuthMethodServerTrust == YES) ? "YES" : "NO");
if (isAuthMethodServerTrust)
{
    if ([trustedHosts containsObject:challenge.protectionSpace.host])
    {
        NSLog(@"<%p %@: %s line:%d> trustedHosts containsObject:challenge.protectionSpace.host", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __PRETTY_FUNCTION__, __LINE__);
        NSURLCredential* urlCredential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
        NSLog(@"<%p %@: %s line:%d> Url credential", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __PRETTY_FUNCTION__, __LINE__);         
        [challenge.sender useCredential:urlCredential forAuthenticationChallenge:challenge];

        //Code to verify certificate info
        SecTrustRef trustRef = [[challenge protectionSpace] serverTrust];
        CFIndex count = SecTrustGetCertificateCount(trustRef); 

        for (CFIndex i = 0; i < count; i++)
        {
            SecCertificateRef certRef = SecTrustGetCertificateAtIndex(trustRef, i);
            CFStringRef certSummary = SecCertificateCopySubjectSummary(certRef);
            CFDataRef certData = SecCertificateCopyData(certRef);
            NSLog(@"<%p %@: %s line:%d> Certificate summary:%@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __PRETTY_FUNCTION__, __LINE__, (NSString*) certSummary);
            NSLog(@"<%p %@: %s line:%d> Certificate data:%@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __PRETTY_FUNCTION__, __LINE__, (NSString*) certData);
            CFRelease(certData);
        }
    }
}
}

此代码为您提供以下与“https://encrypted.google.com”相关的信息： 在“certSummary”NSString 中证书的颁发者。 在证书的“certData”数据中。问题是，目前我不知道如何从此类数据中提取信息（到期日期、公钥……），因此欢迎任何帮助。