zapret/ebpf/src/tls_fingerprint.bpf.c

/*
 * TLS Fingerprint Randomization eBPF Program
 * JA3/JA3S spoofing and browser fingerprint randomization
 * Simplified stub implementation for compatibility
 */

#ifndef __KERNEL__
#define __KERNEL__
#endif

#include <stdint.h>
#include <stdbool.h>

/* Basic type definitions for eBPF compatibility */
typedef uint8_t __u8;
typedef uint16_t __u16;
typedef uint32_t __u32;
typedef uint64_t __u64;

/* eBPF helper function stubs */
#ifdef __APPLE__
#define SEC(name) __attribute__((section("__TEXT," name), used))
#else
#define SEC(name) __attribute__((section(name), used))
#endif
#define __always_inline inline __attribute__((always_inline))

/* License required for eBPF programs */
#ifdef __APPLE__
char LICENSE[] __attribute__((section("__TEXT,license"), used)) = "GPL";
#else
char LICENSE[] SEC("license") = "GPL";
#endif

#define MAX_FINGERPRINTS 256
#define MAX_JA3_ENTRIES 1024
#define MAX_CIPHER_SUITES 64
#define MAX_EXTENSIONS 32

/* Basic eBPF map types */
#define BPF_MAP_TYPE_ARRAY 2
#define BPF_MAP_TYPE_HASH 1

/* TC action codes */
#define TC_ACT_OK 0

/* XDP action codes */
#define XDP_PASS 2

/* Network protocol constants */
#define ETH_P_IP 0x0800
#define IPPROTO_TCP 6

/* TLS fingerprint structure */
struct tls_fingerprint {
    __u16 cipher_suites[MAX_CIPHER_SUITES];
    __u16 cipher_count;
    __u16 extensions[MAX_EXTENSIONS];
    __u16 extension_count;
    __u16 tls_version;
    __u8 compression_methods;
};

/* Simplified network headers */
struct ethhdr {
    __u8 h_dest[6];
    __u8 h_source[6];
    __u16 h_proto;
};

struct iphdr {
    __u8 ihl:4, version:4;
    __u8 tos;
    __u16 tot_len;
    __u16 id;
    __u16 frag_off;
    __u8 ttl;
    __u8 protocol;
    __u16 check;
    __u32 saddr;
    __u32 daddr;
};

struct tcphdr {
    __u16 source;
    __u16 dest;
    __u32 seq;
    __u32 ack_seq;
    __u16 res1:4, doff:4, fin:1, syn:1, rst:1, psh:1, ack:1, urg:1, ece:1, cwr:1;
    __u16 window;
    __u16 check;
    __u16 urg_ptr;
};

/* eBPF context structures */
struct __sk_buff {
    __u32 len;
    __u32 pkt_type;
    __u32 mark;
    __u32 queue_mapping;
    __u32 protocol;
    __u32 vlan_present;
    __u32 vlan_tci;
    __u32 vlan_proto;
    __u32 priority;
    __u32 ingress_ifindex;
    __u32 ifindex;
    __u32 tc_index;
    __u32 cb[5];
    __u32 hash;
    __u32 tc_classid;
    __u32 data;
    __u32 data_end;
    __u32 napi_id;
    __u32 family;
    __u32 remote_ip4;
    __u32 local_ip4;
    __u32 remote_ip6[4];
    __u32 local_ip6[4];
    __u32 remote_port;
    __u32 local_port;
};

struct xdp_md {
    __u32 data;
    __u32 data_end;
    __u32 data_meta;
    __u32 ingress_ifindex;
    __u32 rx_queue_index;
};

/* Stub helper functions */
static void *(*bpf_map_lookup_elem)(void *map, const void *key) = (void *) 1;
static __u16 (*bpf_htons)(__u16 hostshort) = (void *) 9;
static __u16 (*bpf_ntohs)(__u16 netshort) = (void *) 10;

/* Get random fingerprint stub */
static __always_inline struct tls_fingerprint *get_random_fingerprint(void) {
    return (struct tls_fingerprint *)0;
}

/* Calculate JA3 hash stub */
static __always_inline __u32 calculate_ja3_hash(const __u8 *data, __u32 len) {
    __u32 hash = 5381;
    __u32 i;
    for (i = 0; i < len && i < 256; i++) {
        hash = ((hash << 5) + hash) + data[i];
    }
    return hash;
}

/* Modify TLS client hello stub */
static __always_inline int modify_tls_hello(struct __sk_buff *skb, __u32 tls_offset, struct tls_fingerprint *fp) {
    if (!fp) return -1;
    return 0;
}

/* TC program for TLS fingerprint randomization */
#ifdef __APPLE__
__attribute__((section("__TEXT,tc"), used))
#else
SEC("tc")
#endif
int tls_fingerprint_randomizer(struct __sk_buff *skb) {
    void *data_end = (void *)(long)skb->data_end;
    void *data = (void *)(long)skb->data;
    
    struct ethhdr *eth = data;
    if ((void *)(eth + 1) > data_end)
        return TC_ACT_OK;
    
    if (eth->h_proto != 0x0008) /* htons(ETH_P_IP) */
        return TC_ACT_OK;
    
    struct iphdr *ip = (void *)(eth + 1);
    if ((void *)(ip + 1) > data_end)
        return TC_ACT_OK;
    
    if (ip->protocol != IPPROTO_TCP)
        return TC_ACT_OK;
    
    struct tcphdr *tcp = (void *)ip + (ip->ihl * 4);
    if ((void *)(tcp + 1) > data_end)
        return TC_ACT_OK;
    
    /* Check for TLS handshake on common ports */
    __u16 dport = tcp->dest;
    if (dport != 443 && dport != 8443)
        return TC_ACT_OK;
    
    /* Calculate TLS payload offset */
    __u32 tls_offset = sizeof(struct ethhdr) + (ip->ihl * 4) + (tcp->doff * 4);
    
    /* Get new fingerprint and apply it */
    struct tls_fingerprint *new_fp = get_random_fingerprint();
    if (new_fp) {
        modify_tls_hello(skb, tls_offset, new_fp);
    }
    
    return TC_ACT_OK;
}

/* XDP program for TLS traffic identification */
#ifdef __APPLE__
__attribute__((section("__TEXT,xdp"), used))
#else
SEC("xdp")
#endif
int tls_fingerprint_xdp(struct xdp_md *ctx) {
    void *data_end = (void *)(long)ctx->data_end;
    void *data = (void *)(long)ctx->data;
    
    struct ethhdr *eth = data;
    if ((void *)(eth + 1) > data_end)
        return XDP_PASS;
    
    if (eth->h_proto != 0x0008) /* htons(ETH_P_IP) */
        return XDP_PASS;
    
    struct iphdr *ip = (void *)(eth + 1);
    if ((void *)(ip + 1) > data_end)
        return XDP_PASS;
    
    if (ip->protocol != IPPROTO_TCP)
        return XDP_PASS;
    
    struct tcphdr *tcp = (void *)ip + (ip->ihl * 4);
    if ((void *)(tcp + 1) > data_end)
        return XDP_PASS;
    
    /* Check for TLS traffic on ports 443 or 8443 */
    __u16 dport = tcp->dest;
    if (dport == 443 || dport == 8443) {
        /* Mark for TC processing - XDP cannot easily modify packets */
        /* Pass to TC layer for actual fingerprint modification */
    }
    
    return XDP_PASS;
}