在解析证书信息之前，需要将证书转换为X509结构体。以下代码中<code>cert</code>为X509证书结构体

<h4>一、解析证书序列号</h4>

ASN1_INTEGER *serial = X509_get_serialNumber(cert);
BIGNUM *btn = ASN1_INTEGER_to_BN(serial, NULL);
char *res = BN_bn2hex(btn);
NSString *serialStr = [NSString stringWithUTF8String:res];
NSLog(@"序列号:%@",serialStr);

<h4>二、解析证书拥有者信息（用户名）</h4>

char szOutCN[256]={0};
X509_NAME *name = NULL;
name = cert->cert_info->subject;      
X509_NAME_get_text_by_NID(name,NID_commonName,szOutCN,256)
NSString *nameStr = [NSString stringWithUTF8String:szOutCN];
NSLog(@"用户名:%@",nameStr);

<h4>三、解析证书颁发机构</h4>

X509_NAME_ENTRY *name_entry;
long Nid;
unsigned char msginfo[1024];
int msginfoLen;
        
NSMutableString *issuerInfo = [[NSMutableString alloc] init];
NSMutableString *certCN = [[NSMutableString alloc] init];
        
X509_NAME *issuer = X509_get_issuer_name(cert);
int entriesNum = sk_X509_NAME_ENTRY_num(issuer->entries);
for (int i = 0; i < entriesNum; i++) {
    name_entry = sk_X509_NAME_ENTRY_value(issuer->entries, i);
            
    Nid = OBJ_obj2nid(name_entry->object);
    msginfoLen = name_entry->value->length;
    memcpy(msginfo,name_entry->value->data,msginfoLen);
    msginfo[msginfoLen]='\0';
            
    switch(Nid)
    {
        case NID_countryName://国家C
                    [issuerInfo appendString:[NSString stringWithFormat:@"C=%s,",msginfo]];
                    [certCN appendString:[NSString stringWithFormat:@"C=%s",msginfo]];
                    break;
                    
        case NID_stateOrProvinceName://省ST
                    [issuerInfo appendString:[NSString stringWithFormat:@"ST=%s,",msginfo]];
                    break;
                    
        case NID_localityName://地区L
                    [issuerInfo appendString:[NSString stringWithFormat:@"L=%s,",msginfo]];
                    break;
                    
        case NID_organizationName://组织O=
                    [issuerInfo appendString:[NSString stringWithFormat:@"O=%s,",msginfo]];
                    break;
                    
        case NID_organizationalUnitName://单位OU
                    [issuerInfo appendString:[NSString stringWithFormat:@"OU=%s,",msginfo]];
                    break;
                    
        case NID_commonName://通用名CN
                    [issuerInfo appendString:[NSString stringWithFormat:@"CN=%s",msginfo]];
                    break;
                    
        case NID_pkcs9_emailAddress://Mail
                    break;
                    
            }
}

NSLog(@"颁发机构:%@",issuerInfo);

<h4>四、解析证书密钥算法</h4>

EVP_PKEY *pk = NULL;
pk = X509_get_pubkey(cert);
NSString *pulType;
        
if (EVP_PKEY_RSA == pk->type) {
    pulType = @"RSA";
} else if (EVP_PKEY_EC == pk->type) {
    pulType = @"EC";
} else if (EVP_PKEY_DSA == pk->type) {
    pulType = @"DSA";
} else if (EVP_PKEY_DH == pk->type) {
    pulType = @"DH";
} else {
    pulType = @"UNKNOWN";
}

NSLog(@"密钥算法:%@",pulType);

<h4>五、解析证书颁发时间和过期时间</h4>

解析办法时间需要一个工具方法，因为直接获取时间为格林威治时间。需要把它转化成秒数然后再转化为本地时间。

<b>将格林威治时间转换成秒数的方法</b>
原方法地址：http://stackoverflow.com/questions/10975542/asn1-time-to-time-t-conversion

- (time_t)skf_ext_ASN1_GetTimeT:(ASN1_TIME *)time {
    struct tm t;
    const char* str = (const char*) time->data;
    size_t i = 0;
    
    memset(&t, 0, sizeof(t));
    
    if (time->type == V_ASN1_UTCTIME) {/* two digit year */
        t.tm_year = (str[i++] - '0') * 10;
        t.tm_year += (str[i++] - '0');
        if (t.tm_year < 70)
            t.tm_year += 100;
    } else if (time->type == V_ASN1_GENERALIZEDTIME) {/* four digit year */
        t.tm_year = (str[i++] - '0') * 1000;
        t.tm_year+= (str[i++] - '0') * 100;
        t.tm_year+= (str[i++] - '0') * 10;
        t.tm_year+= (str[i++] - '0');
        t.tm_year -= 1900;
    }
    t.tm_mon  = (str[i++] - '0') * 10;
    t.tm_mon += (str[i++] - '0') - 1; // -1 since January is 0 not 1.
    t.tm_mday = (str[i++] - '0') * 10;
    t.tm_mday+= (str[i++] - '0');
    t.tm_hour = (str[i++] - '0') * 10;
    t.tm_hour+= (str[i++] - '0');
    t.tm_min  = (str[i++] - '0') * 10;
    t.tm_min += (str[i++] - '0');
    t.tm_sec  = (str[i++] - '0') * 10;
    t.tm_sec += (str[i++] - '0');
    
    /* Note: we did not adjust the time based on time zone information */
    return mktime(&t);
}

<b>解析时间方法</b>

ASN1_TIME *start = NULL;
ASN1_TIME *end = NULL;
time_t ttStart = {0};
time_t ttEnd = {0};
        
// 颁发时间
start = X509_get_notBefore(cert);
ttStart = [self skf_ext_ASN1_GetTimeT:start];
// 格林威治时间与北京时间相差八小时，所以加八小时。
ttStart = ttStart + 8 * 60 * 60; 
NSDate *startDate = [NSDate dateWithTimeIntervalSince1970:ttStart];
NSString *startDateStr = [self.dateFormatter stringFromDate:startDate];
NSLog(@"颁发时间:%@",startDateStr);

// 过期时间
end = X509_get_notAfter(cert);
ttEnd = [self skf_ext_ASN1_GetTimeT:end];
ttEnd = ttEnd + 8 * 60 * 60;
NSDate *endDate = [NSDate dateWithTimeIntervalSince1970:ttEnd];
NSString *endDateStr = [self.dateFormatter stringFromDate:endDate];
NSLog(@"过期时间:%@",endDateStr);

<b><code>self.dateFormatter</code>懒加载方法</b>

- (NSDateFormatter *)dateFormatter
{
    if (!_dateFormatter) {
        _dateFormatter = [[NSDateFormatter alloc] init];
        NSTimeZone *zone = [NSTimeZone localTimeZone];
        [_dateFormatter setTimeZone:zone];
        [_dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    }
    return _dateFormatter;
}

全文完