utun2/lib/platform_compat.c

/* platform_compat.c - Platform compatibility layer implementation */

#include "platform_compat.h"
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#ifdef _WIN32
    #include <windows.h>
    #include <bcrypt.h>
    #include <iphlpapi.h>
    #pragma comment(lib, "iphlpapi.lib")
    #ifndef STATUS_SUCCESS
        #define STATUS_SUCCESS ((NTSTATUS)0x00000000L)
    #endif
#else
    #include <fcntl.h>
    #include <unistd.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #include <ifaddrs.h>
    #include <net/if.h>
#endif

/*
 * Generate cryptographically secure random bytes
 * Returns 0 on success, -1 on error
 */
int random_bytes(uint8_t *buffer, size_t len) {
    if (!buffer || len == 0) return -1;
    
#ifdef _WIN32
    NTSTATUS status = BCryptGenRandom(NULL, buffer, (ULONG)len, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
    return (status == STATUS_SUCCESS) ? 0 : -1;
#else
    int fd = open("/dev/urandom", O_RDONLY);
    if (fd < 0) return -1;
    
    ssize_t ret = read(fd, buffer, len);
    close(fd);
    
    return (ret == (ssize_t)len) ? 0 : -1;
#endif
}

#ifndef _WIN32
static uint32_t get_default_route_ip_linux(void) {
    FILE *f = fopen("/proc/net/route", "r");
    if (!f) return 0;

    char line[256];
    char *ifname = NULL;
    unsigned int dest, gw;

    if (!fgets(line, sizeof(line), f)) {
        fclose(f);
        return 0;
    }

    while (fgets(line, sizeof(line), f)) {
        int items = sscanf(line, "%ms %x %x", &ifname, &dest, &gw);
        if (items != 3) {
            free(ifname);
            continue;
        }

        if (dest == 0) {
            free(ifname);
            break;
        }
        free(ifname);
        ifname = NULL;
    }

    fclose(f);

    if (!ifname) return 0;

    struct ifaddrs *ifaddr, *ifa;
    if (getifaddrs(&ifaddr) == -1) {
        free(ifname);
        return 0;
    }

    uint32_t result = 0;
    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
        if (ifa->ifa_addr == NULL) continue;
        if (ifa->ifa_name == NULL) continue;
        if (strcmp(ifa->ifa_name, ifname) != 0) continue;
        if (ifa->ifa_addr->sa_family != AF_INET) continue;

        struct sockaddr_in *addr = (struct sockaddr_in *)ifa->ifa_addr;
        result = addr->sin_addr.s_addr;
        break;
    }

    freeifaddrs(ifaddr);
    free(ifname);
    return result;
}
#else
static uint32_t get_default_route_ip_windows(void) {
    SOCKET s = socket(AF_INET, SOCK_DGRAM, 0);
    if (s == INVALID_SOCKET) return 0;

    struct sockaddr_in remote;
    remote.sin_family = AF_INET;
    remote.sin_port = htons(53);
    remote.sin_addr.s_addr = inet_addr("8.8.8.8");

    if (connect(s, (struct sockaddr *)&remote, sizeof(remote)) == SOCKET_ERROR) {
        closesocket(s);
        return 0;
    }

    struct sockaddr_in local;
    int len = sizeof(local);
    if (getsockname(s, (struct sockaddr *)&local, &len) == SOCKET_ERROR) {
        closesocket(s);
        return 0;
    }

    closesocket(s);
    return local.sin_addr.s_addr;
}
#endif

uint32_t get_default_route_ip(void) {
#ifdef _WIN32
    return get_default_route_ip_windows();
#else
    return get_default_route_ip_linux();
#endif
}