woody-woodpacker/srcs/woody.c

#include "../includes/woody.h"


int elf_magic_numbers(char *str)
{
	return (!ft_strncmp(str, ELFMAG, SELFMAG));
}

void	encrypt_zone(char *file, unsigned long int offset, unsigned long int size)
{
	size_t i = 0;
	while (i < size)
	{
		file[offset + i] = 0;
		++i;
	}
}

int		save_elf(char *path, char *file, unsigned long int size)
{
	int fd = open(path, O_CREAT | O_WRONLY | O_TRUNC, 0755);
    if (fd == -1) {
		ft_printf("Error: Failed to create new file \'%s\'\n", path);
		return EXIT_FAILURE;
    }

    if (write(fd, file, size) == -1) {
        close(fd);
        ft_printf("Error: Failed to write new file \'%s\'\n", path);
        return EXIT_FAILURE;
    }

    if (close(fd) == -1) {
		ft_printf("Error: Failed to close new file \'%s\'\n", path);
        return EXIT_FAILURE;
    }
	return EXIT_SUCCESS;
}

int	get_load_segment(t_efl_content *woody, int start, bool executable)
{
	for (int i = start; i < woody->Ehdr->e_phnum; i++)
	{
		if (woody->Phdr[i].p_type == PT_LOAD)
		{
			if (executable)
			{
				if (woody->Phdr[i].p_flags & PF_X)
					return i;
			}
			else
				return i;
		}
	}
	return -1;
}


int32_t find_jmp(char *code, size_t len)
{
	char *jump = JUMP;
	char *ptr = ft_strnstr_nullterminated(code, jump, len);
	if (ptr)
	{
		return ptr - code;
	}
	return 0;
}

void	find_cave(t_efl_content *woody)
{
	woody->Phdr = (Elf64_Phdr *)secure_jump(woody->file, woody->file_size, woody->Ehdr->e_phoff, sizeof(Elf64_Phdr));

	int i = get_load_segment(woody, 0, true);	
	int j = get_load_segment(woody, i + 1, false);
	
	printf("%d %ld\n", i, woody->Phdr[i].p_align);
	printf("%d %ld\n", j, woody->Phdr[j].p_align);
	printf("code_cave_start = %lx, virtual adress = %lx\n", woody->Phdr[i].p_offset, woody->Phdr[i].p_vaddr);
	printf("code_cave_size = %lx\n", woody->Phdr[j].p_offset - (woody->Phdr[i].p_offset + woody->Phdr[i].p_filesz));

	Elf64_Off payload_off = woody->Phdr[i].p_offset + woody->Phdr[i].p_memsz;

    size_t len = sizeof(PAYLOAD) - 1;
	char payload[] = PAYLOAD;
	int32_t jmp = find_jmp(payload, len);

	printf("%ld\n", (long int)payload[jmp + 1]);
	int32_t test = ((payload_off + len) - woody->Ehdr->e_entry) * -1;

	ft_memcpy(&payload[jmp + 1], &test, sizeof(test));

	ft_memcpy(woody->file + payload_off, payload, len);

	printf("old entry : %lx\n", woody->Ehdr->e_entry);
	printf("backward offset = %ld\n", (payload_off + len) - woody->Ehdr->e_entry);
	woody->Ehdr->e_entry = payload_off;
	woody->Phdr[i].p_filesz += len;
	woody->Phdr[i].p_memsz += len;
		

	printf("new entry = %lx\n", woody->Ehdr->e_entry);

	printf("p_filesz = %lx\n", woody->Phdr[i].p_filesz);
	printf("p_memsz = %lx\n", woody->Phdr[i].p_memsz);
	woody->file_size += len;

}


int inject(t_efl_content *woody)
{
	woody->Ehdr = (Elf64_Ehdr *)secure_jump(woody->file, woody->file_size, 0, sizeof(Elf64_Ehdr));
	if (!woody->Ehdr || !elf_magic_numbers(woody->file) || woody->Ehdr->e_ident[EI_CLASS] != 2)
	{
		ft_printf("Error: \'%s\' is not a valid 64-bit ELF file\n", woody->file_path);
		return EXIT_FAILURE;
	}

	printf("entry point = %ld\n", woody->Ehdr->e_entry);
	Elf64_Shdr *Shdr = (Elf64_Shdr *)secure_jump(woody->file, woody->file_size, woody->Ehdr->e_shoff, sizeof(Elf64_Shdr));
	if (Shdr == NULL || !secure_jump(woody->file, woody->file_size, woody->Ehdr->e_shoff, woody->Ehdr->e_shnum * sizeof(Elf64_Shdr)))
	{
		return ft_put_error("Corrupted file");
	}
	if (woody->file_size > woody->Ehdr->e_shoff + woody->Ehdr->e_shnum * sizeof(Elf64_Shdr))
	{
		printf("extra_data !\n"); // save it in woody->extra_data and append it to the end of the woody file ? Could be dangerous
	}

	Elf64_Shdr *symbols_table = NULL;
    for (int i = 0; i < woody->Ehdr->e_shnum; i++) {
		if (Shdr[i].sh_type == SHT_SYMTAB) {
            symbols_table = secure_jump(woody->file, woody->file_size, woody->Ehdr->e_shoff + (i * sizeof(Elf64_Shdr)), sizeof(Elf64_Shdr));
        }
    }
	if (symbols_table == NULL)
		return ft_put_error("No symbols");

	if (!secure_jump(woody->file, woody->file_size, woody->Ehdr->e_shoff + (woody->Ehdr->e_shstrndx * sizeof(Elf64_Shdr)), sizeof(Elf64_Shdr)))
		return ft_put_error("Corrupted file");

	char *Sshstrtab = (char *)secure_jump(woody->file, woody->file_size, Shdr[woody->Ehdr->e_shstrndx].sh_offset, 0);
	if (Sshstrtab == NULL)
		return ft_put_error("Corrupted file");

	for (int i = 0; i < woody->Ehdr->e_shnum; i++) {
		char *section_name = Sshstrtab + Shdr[i].sh_name;
		printf("%s : Offset: %lx | Size: %lx | Virtual adress: %lx\n", section_name, Shdr[i].sh_offset, Shdr[i].sh_size, Shdr[i].sh_addr);
	}	

	// useless for now
    Elf64_Shdr *strtab_header = (Elf64_Shdr *)secure_jump(woody->file, woody->file_size, woody->Ehdr->e_shoff + (symbols_table->sh_link * woody->Ehdr->e_shentsize), sizeof(Elf64_Shdr)); 
	if (!strtab_header)
		return ft_put_error("Corrupted file");

    char *strtab = secure_jump(woody->file, woody->file_size, strtab_header->sh_offset, 0);
	if (strtab == NULL)
		return ft_put_error("Corrupted file");
    Elf64_Sym *symbols = (Elf64_Sym *)secure_jump(woody->file, woody->file_size, symbols_table->sh_offset, sizeof(Elf64_Sym));
	if (symbols == NULL)
		return ft_put_error("Corrupted file");
	// end useless	woody->Ehdr->e_entry = 

	find_cave(woody);

	char *woody_file = malloc(woody->file_size);

	ft_memcpy(woody_file, woody->file, woody->file_size);

	// encrypt_zone(woody_file, strtab_header->sh_offset , strtab_header->sh_size);
	munmap(woody_file, woody->file_size);
	return save_elf("woody", woody_file, woody->file_size);
}