0x01 緣由

有人通過github找我瞭解xplico，一直沒有好好解答他的問題，於是想著手寫這麼一篇簡單文章。

0x02 介紹

做協議識別：1、特徵碼 

      2、埠

      3、正則

詳細介紹，傳送：http://www.sdnlab.com/17449.html

0x03 xplico的使用

在tTcp_garbage.c \Udp_analysis.c 中使用，一般是將tcp層資料傳給ndpi，使用是要在配置檔案中進行配置；

/* nDPI library */
#include "ndpi_main.h"
#include "ndpi_api.h"
....
....

//申請記憶體
static void *nDPImalloc(unsigned long size)
{
    return malloc(size);
}

//釋放記憶體
static void nDPIfree(void *freeable)
{
    free(freeable);
}


static void nDPIPrintf(u_int32_t protocol, void *id_struct, ndpi_log_level_t log_level, const char *format, ...)
{
    return;
}

//匹配
static ndpi_protocol nDPIPacket(packet *pkt, struct ndpi_flow_struct *l7flow, struct ndpi_id_struct *l7src, struct ndpi_id_struct *l7dst, bool ipv4)
{
    void *data;
    size_t offset, size;
    ftval voffset;
    const pstack_f *ip;
    unsigned long when;
    ndpi_protocol l7prot_id;

    if (ipv4) {
        ip = ProtStackSearchProt(pkt->stk, ip_id);
        ProtGetAttr(ip, ip_offset_id, &voffset);
        offset = voffset.uint32;
        data = pkt->raw + offset;
        size = pkt->raw_len - offset;
    }
    else {
        ip = ProtStackSearchProt(pkt->stk, ipv6_id);
        ProtGetAttr(ip, ipv6_offset_id, &voffset);
        offset = voffset.uint32;
        data = pkt->raw + offset;
        size = pkt->raw_len - offset;
    }
    when = pkt->cap_sec;
    when = when * NDPI_TICK_RES;
    when += pkt->cap_usec/1000;  /* (1000000 / NDPI_TICK_RES) */
    pthread_mutex_lock(&ndpi_mux);
      /**
   * Processes one packet and returns the ID of the detected protocol.
   * This is the MAIN PACKET PROCESSING FUNCTION.
   *
   * @par    ndpi_struct   = the detection module
   * @par    flow          = pointer to the connection state machine
   * @par    packet        = unsigned char pointer to the Layer 3 (IP header)
   * @par    packetlen     = the length of the packet
   * @par    current_tick  = the current timestamp for the packet
   * @par    src           = pointer to the source subscriber state machine
   * @par    dst           = pointer to the destination subscriber state machine
   * @return the detected ID of the protocol
   *
   */
    l7prot_id = ndpi_detection_process_packet(ndpi, l7flow, data, size, when, l7src, l7dst);
    pthread_mutex_unlock(&ndpi_mux);

    return l7prot_id;
}

packet *TcpGrbDissector(int flow_id)
{
    char *l7prot_type;
    struct ndpi_flow_struct *l7flow;
    struct ndpi_id_struct *l7src, *l7dst;
    ndpi_protocol l7prot_id
    ....
    ....
    if (stage != 4 && (l7prot_type == NULL || l7prot_id.master_protocol == NDPI_PROTOCOL_HTTP) && l7flow != NULL) {
        if (TcpGrbClientPkt(priv, pkt)) {
        		//做匹配
            l7prot_id = nDPIPacket(pkt, l7flow, l7src, l7dst, ipv4);
        }
        else {
            l7prot_id = nDPIPacket(pkt, l7flow, l7dst, l7src, ipv4);
        }
        if (l7prot_id.protocol != NDPI_PROTOCOL_UNKNOWN) {
            stage++;
            //根據id獲取名字
            l7prot_type = ndpi_protocol2name(ndpi, l7prot_id, buff, TCP_CFG_LINE_MAX_SIZE);
        }
    }
    ....
    ....
}
int DissectInit(void)
{
    char tmp_dir[256];
    unsigned short i;
    /*協議掩碼*/
    NDPI_PROTOCOL_BITMASK all;

    ....
    ....
    
    /* ndpi */
    pthread_mutex_init(&ndpi_mux, NULL);
    /*初始化，返回一個初始化檢測模組*/
    ndpi = ndpi_init_detection_module(NDPI_TICK_RES, nDPImalloc, nDPIfree, nDPIPrintf);
    if (ndpi == NULL) {
        LogPrintf(LV_ERROR, "nDPi initializzation failed");

        return -1;
    }
    /* enable all protocols */
    NDPI_BITMASK_SET_ALL(all);
    //設定協議掩碼
    ndpi_set_protocol_detection_bitmask2(ndpi, &all);
    //得到id結構的大小，用於動態申請ndpi_id_struct
    ndpi_proto_size = ndpi_detection_get_sizeof_ndpi_id_struct();
    //得到flow結構的大小，用於動態申請ndpi_flow_struct
    ndpi_flow_struct_size = ndpi_detection_get_sizeof_ndpi_flow_struct();

    return 0;
}
 

0x04 xplico中的使用例子

./xplico -l -c ./config/xplico_dpi.cfg -m pcap -f eyou.pcap

輸出結果：

13:59:00 [tcp-grb]{9969}-DEBUG: 	DST: 172.16.2.54:56051
l7prot_type HTTP //新增的輸出
13:59:00 [tcp-grb]{9969}-DEBUG: TCP->HTTP garbage... bye bye  fid:9969 count:2
13:59:00 [tcp-grb]{9966}-DEBUG: TCP->Unknown garbage... bye bye  fid:9966 count:2
13:59:00 [udp-grb]{9958}-DEBUG: 	DST: 239.255.255.250:1900
l7prot_type HTTP 
13:59:00 [tcp-grb]{9894}-DEBUG: TCP->HTTP garbage... bye bye  fid:9894 count:103