iOS获取SSL证书的sha1值和sha256值

参考链接：Get SSL certificate details

最近在做SSL证书加密，因为证书有有效期，因此需要考虑证书过期前的更新机制：用sha1值是否变更，来判断服务端的SSL证书是否已更新。
首先，将.cer证书转成NSData类型。
获取sha1值方法：

+(NSString*)sha1:(NSData*)certData {
    unsigned char sha1Buffer[CC_SHA1_DIGEST_LENGTH];
    CC_SHA1(certData.bytes, certData.length, sha1Buffer);
    NSMutableString *fingerprint = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 3];
    for (int i = 0; i < CC_SHA1_DIGEST_LENGTH; ++i)
        [fingerprint appendFormat:@"%02x ",sha1Buffer[i]];
    return [fingerprint stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
}

获取sha256值方法：

+(NSString*)sha256:(NSData*)certData {
    unsigned char sha256Buffer[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256(certData.bytes, certData.length, sha256Buffer);
    NSMutableString *fingerprint = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 3];
    for (int i = 0; i < CC_SHA256_DIGEST_LENGTH; ++i)
        [fingerprint appendFormat:@"%02x ",sha256Buffer[i]];
    return [fingerprint stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
}