generate payload from file

.gitignore

@@ -1,3 +1,4 @@
 *.o
 *.a
-woody_woodpacker
+woody_woodpacker
+woody

.vscode/settings.json

@@ -0,0 +1,8 @@
+{
+	"files.associations": {
+		"stdio.h": "c",
+		"mman.h": "c",
+		"stdint.h": "c",
+		"compare": "c"
+	}
+}

Makefile

@@ -4,7 +4,8 @@ SRCS_PATH	= srcs/
 
 SRCS  =		$(SRCS_PATH)main.c \
 			$(SRCS_PATH)utils.c \
-			$(SRCS_PATH)woody.c
+			$(SRCS_PATH)woody.c \
+			$(SRCS_PATH)encrypt.c
 
 
 OBJS		= ${SRCS:.c=.o}
@@ -37,4 +38,4 @@ fclean:
 re:		fclean
 		make all
 
-.PHONY : all clean fclean re
+.PHONY : all clean fclean re

README

@@ -0,0 +1,5 @@
+Transform payload code in hexa :
+	nasm -f elf64 -o print.o print.s && ld -o print print.o && nasm -f bin -o payload print.s && hexdump -v -e '"\\\x\" 1/1 "%02x"' payload
+
+To get it in the clipboad directly append :
+	| xclip -sel clip to directly

ft_printf/libft/Makefile

@@ -41,6 +41,7 @@ SRCS  =		$(SRCS_PATH)ft_atoi.c \
 			$(SRCS_PATH)ft_bzero.c \
 			$(SRCS_PATH)ft_strdup.c \
 			$(SRCS_PATH)ft_strnstr.c \
+			$(SRCS_PATH)ft_strnstr_nullterminated.c \
 			$(SRCS_PATH)ft_calloc.c \
 			$(SRCS_PATH)ft_substr.c \
 			$(SRCS_PATH)ft_strjoin.c \

ft_printf/libft/ft_strnstr_nullterminated.c

@@ -0,0 +1,17 @@
+#include "libft.h"
+
+char	*ft_strnstr_nullterminated(const char *big, const char *little, size_t len)
+{
+	size_t	len_l;
+
+	if (*little == 0)
+		return ((char *)big);
+	len_l = ft_strlen(little);
+	while (len-- >= len_l)
+	{
+		if (*big == *little && ft_strncmp(big, little, len_l) == 0)
+			return ((char *)big);
+		big++;
+	}
+	return (NULL);
+}

ft_printf/libft/libft.h

@@ -37,6 +37,7 @@ int				ft_strncmp(const char *s1, const char *s2, size_t n);
 size_t			ft_strlcpy(char *dst, const char *src, size_t size);
 size_t			ft_strlcat(char *dst, const char *src, size_t size);
 char			*ft_strnstr(const char *big, const char *little, size_t len);
+char			*ft_strnstr_nullterminated(const char *big, const char *little, size_t len);
 int				ft_atoi(const char *nptr);
 char			*ft_substr(char const *s, unsigned int start, size_t len);
 char			*ft_strjoin(char const *s1, char const *s2);
@@ -55,6 +56,7 @@ void			*ft_calloc(size_t nmemb, size_t size);
 char			*ft_convert_base(char *nbr, char *base_from, char *base_to);
 char			*ft_u_convert(char *nbr, char *base_from, char *base_to);
 void			ft_rev_int_tab(char *tab, int size);
+
 typedef struct	s_list
 {
 	void			*content;

includes/woody.h

@@ -1,7 +1,8 @@
 #ifndef WOODY_H
-# define WOODY_H
+#define WOODY_H
 
 #include "../ft_printf/includes/ft_printf.h"
+#include <stdbool.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -11,21 +12,35 @@
 #include <sys/mman.h>
 #include <fcntl.h>
 #include <elf.h>
+#include <stdint.h>
+
+#define JUMP "\xe9"
+
+typedef struct payload
+{
+	char *payload;
+	size_t len;
+}	t_payload;
 
 typedef struct efl_content
 {
 	long unsigned int file_size;
-	char	*file_path;
-	char	*file;
-
-}				t_efl_content;
-
+	char *file_path;
+	char *file;
+	Elf64_Ehdr *Ehdr;
+	Elf64_Phdr *Phdr;
+	Elf64_Shdr *Shdr;
+	char *extra_data;
+} t_efl_content;
 
 // utils.c
-void	*secure_access(char *file, unsigned long file_size, unsigned long offset_to_data, unsigned long supposed_data_size);
-int		ft_put_error(char *str);
+void *fetch(char *file, unsigned long file_size, unsigned long offset_to_data, unsigned long supposed_data_size);
+int ft_put_error(char *str);
 
 // woody.c
-int woody(t_efl_content *file_content);
+int prepare_injection(t_efl_content *woody);
+
+// encrypt.c
+void encrypt(char *file, unsigned long int offset, unsigned long int size);
 
 #endif

print.s

@@ -0,0 +1,27 @@
+bits 64
+global _start
+
+_start:
+		push rax
+		push rdi
+		push rsi
+		push rdx
+
+		mov rdi, 1
+		mov rdi, 1
+		mov rdi, 1
+		mov rdi, 1
+		mov rdi, 1
+		mov rdi, 1
+		lea     rsi, [rel msg]
+		mov rdx, 10
+		mov rax, 1
+		syscall
+
+	    pop rdx
+        pop rsi
+        pop rdi
+        pop rax
+        jmp 0x00000000
+
+		msg     db "..WOODY..",10

srcs/encrypt.c

@@ -0,0 +1,11 @@
+#include "../includes/woody.h"
+
+void	encrypt(char *file, unsigned long int offset, unsigned long int size)
+{
+	size_t i = 0;
+	while (i < size)
+	{
+		file[offset + i] = 0;
+		++i;
+	}
+}

srcs/main.c

@@ -1,29 +1,29 @@
 #include "../includes/woody.h"
 
-int get_elf_file(t_efl_content *file_content)
+int get_elf_file(t_efl_content *woody)
 {
 	int fd;
 	off_t off;
 
-	fd = open(file_content->file_path, O_RDONLY);
+	fd = open(woody->file_path, O_RDONLY);
 	if (fd < 0)
 	{
-		ft_printf("Error: Failed to open \'%s\'\n", file_content->file_path);
+		ft_printf("Error: Failed to open \'%s\'\n", woody->file_path);
 		return EXIT_FAILURE;
 	}
 	off = lseek(fd, 0, SEEK_END);
     if (off == -1)
     {
 		close(fd);
-		ft_printf("Error: Failed to read file offset \'%s\'\n", file_content->file_path);
+		ft_printf("Error: Failed to read file offset \'%s\'\n", woody->file_path);
         return EXIT_FAILURE;
     }
-	file_content->file_size = off;
-	file_content->file = mmap(NULL, file_content->file_size, PROT_READ, MAP_PRIVATE, fd, 0);
-    if (file_content->file  == MAP_FAILED)
+	woody->file_size = off;
+	woody->file = mmap(NULL, woody->file_size, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
+    if (woody->file  == MAP_FAILED)
 	{
 		close(fd);
-		ft_printf("Error: Failed to map file \'%s\'\n", file_content->file_path);
+		ft_printf("Error: Failed to map file \'%s\'\n", woody->file_path);
 		return EXIT_FAILURE;
     }
     close(fd);
@@ -32,15 +32,14 @@ int get_elf_file(t_efl_content *file_content)
 
 int main(int ac, char **av)
 {
-	t_efl_content file_content;
+	t_efl_content woody;
 	if (ac != 2)
 	{
 		return ft_put_error("Woody_woodpacker take 1 argument\n");
 	}
-	file_content.file_path = av[1];
-	int ret = get_elf_file(&file_content);
+	woody.file_path = av[1];
+	int ret = get_elf_file(&woody);
 	if (ret == EXIT_FAILURE)
 		return ret;
-	
-	return woody(&file_content);
+	return prepare_injection(&woody);
 }

srcs/utils.c

@@ -1,6 +1,6 @@
 #include "../includes/woody.h"
 
-void	*secure_access(char *file, unsigned long file_size, unsigned long offset_to_data, unsigned long supposed_data_size)
+void	*fetch(char *file, unsigned long file_size, unsigned long offset_to_data, unsigned long supposed_data_size)
 {
 	if (file_size > offset_to_data && file_size >= (offset_to_data + supposed_data_size))
 		return (file + offset_to_data);

srcs/woody.c

@@ -1,12 +1,214 @@
 #include "../includes/woody.h"
 
-int woody(t_efl_content *file_content)
-{
-	Elf64_Ehdr *Ehdr = (Elf64_Ehdr *)secure_access(file_content->file, file_content->file_size, 0, sizeof(Elf64_Ehdr));
 
-	if (!Ehdr)
+int elf_magic_numbers(char *str)
+{
+	return (!ft_strncmp(str, ELFMAG, SELFMAG));
+}
+
+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;
+}
+
+void offset_sections(t_efl_content *woody, unsigned int from, unsigned int offset_ammount)
+{
+	for (int i = 0; i < woody->Ehdr->e_phnum; i++)
+	{
+		if (woody->Phdr[i].p_offset > from)
+			woody->Phdr[i].p_offset += offset_ammount;
+	}
+	for (int i = 0; i < woody->Ehdr->e_shnum; i++)
+	{
+		if (woody->Shdr[i].sh_offset > from)
+			woody->Shdr[i].sh_offset += offset_ammount;
+	}
+}
+
+size_t	create_codecave(t_efl_content *woody, Elf64_Phdr *load_segment, t_payload *payload)
+{
+	const unsigned int page_size = 4096; // getpagesize(); not authorized
+	unsigned int padding_size = ((payload->len / page_size) + 1) * page_size;
+	unsigned int codecave_start = load_segment->p_offset + load_segment->p_filesz;
+	offset_sections(woody, codecave_start, padding_size);
+	char *new_woody = malloc(woody->file_size + padding_size);
+	if (!new_woody)
+		return 0;
+	ft_memcpy(new_woody, woody->file, codecave_start);
+	ft_bzero(new_woody + codecave_start, padding_size);
+	ft_memcpy(new_woody + codecave_start + padding_size,  woody->file + codecave_start, woody->file_size - codecave_start);
+	munmap(woody->file, woody->file_size);
+	woody->file = new_woody;
+	woody->file_size += padding_size;
+	woody->Ehdr = (Elf64_Ehdr *)new_woody;
+	woody->Phdr = (Elf64_Phdr *)fetch(woody->file, woody->file_size, woody->Ehdr->e_phoff, sizeof(Elf64_Phdr));
+	woody->Shdr = (Elf64_Shdr *)fetch(woody->file, woody->file_size, woody->Ehdr->e_shoff, sizeof(Elf64_Shdr));
+	return codecave_start;
+}
+
+t_payload *get_payload()
+{
+	t_payload *payload = malloc(sizeof(t_payload));
+	if (!payload)
+		return NULL;
+	char buffer[1024];
+	int fd = open("payload", O_RDONLY);
+	payload->len = read(fd, buffer, 1024);
+	payload->payload = malloc(sizeof(char) * payload->len);
+	ft_memcpy(payload->payload, buffer, payload->len);
+	return payload;
+}
+
+int	insert_payload(t_efl_content *woody, t_payload *payload, size_t payload_position)
+{
+	char *ptr = ft_strnstr_nullterminated(payload->payload, JUMP, payload->len);
+	if (ptr)
+	{
+		int32_t jmp_index = ptr - payload->payload; 
+		int32_t jump_value = ((payload_position + payload->len) - woody->Ehdr->e_entry) * -1;
+
+		ft_memcpy(&payload->payload[jmp_index + 1], &jump_value, sizeof(jump_value));
+		ft_memcpy(woody->file + payload_position, payload->payload, payload->len);
+
+		printf("Old entry : %ld (%lx)\n", woody->Ehdr->e_entry, woody->Ehdr->e_entry);
+		printf("Code cave start = %ld (%lx)\n", payload_position, payload_position);
+		printf("Payload size = %ld (%lx)\n", payload->len, payload->len);
+		printf("Backwar d offset = %d (%x)\n", jump_value, jump_value);
+		
+		return EXIT_SUCCESS;
+	}
+	return EXIT_FAILURE;
+}
+
+void	inject(t_efl_content *woody)
+{
+	t_payload *payload = get_payload();
+
+	int i = get_load_segment(woody, 0, true);	
+	int j = get_load_segment(woody, i + 1, false);
 	
-	// if (Ehdr->e_ident[EI_CLASS])
+	size_t code_cave_size = woody->Phdr[j].p_offset - (woody->Phdr[i].p_offset + woody->Phdr[i].p_filesz);
+	size_t payload_position;
+	printf("load position = : %ld (%lx)\n", woody->Phdr[i].p_offset, woody->Phdr[i].p_offset);
+	printf("load size = : %ld (%lx)\n", woody->Phdr[i].p_filesz, woody->Phdr[i].p_filesz);
+
+	if (code_cave_size > payload->len) // inverse here to test the other technique
+	{
+		payload_position = woody->Phdr[i].p_offset + woody->Phdr[i].p_memsz;
+		printf("Code_cave_size = %ld (%lx)\n", code_cave_size, code_cave_size);
+	}
+	else
+	{
+		payload_position = create_codecave(woody, &woody->Phdr[i], payload);
+	}
+	insert_payload(woody, payload, payload_position);
+
+	woody->Ehdr->e_entry = payload_position;
+	woody->Phdr[i].p_filesz += payload->len;
+	woody->Phdr[i].p_memsz += payload->len;
+
+	printf("New entry = %ld (%lx)\n", woody->Ehdr->e_entry, woody->Ehdr->e_entry);
+}
+
+int get_elf_sections(t_efl_content *woody)
+{
+	woody->Ehdr = (Elf64_Ehdr *)fetch(woody->file, woody->file_size, 0, sizeof(Elf64_Ehdr));
+	if (!woody->Ehdr || !elf_magic_numbers(woody->file) || woody->Ehdr->e_ident[EI_CLASS] != ELFCLASS64)
+	{
+		ft_printf("Error: \'%s\' is not a valid 64-bit ELF file\n", woody->file_path);
+		return EXIT_FAILURE;
+	}
+	woody->Phdr = (Elf64_Phdr *)fetch(woody->file, woody->file_size, woody->Ehdr->e_phoff, sizeof(Elf64_Phdr));
+
+	woody->Shdr = (Elf64_Shdr *)fetch(woody->file, woody->file_size, woody->Ehdr->e_shoff, sizeof(Elf64_Shdr));
+	if (woody->Shdr == NULL || !fetch(woody->file, woody->file_size, woody->Ehdr->e_shoff, woody->Ehdr->e_shnum * sizeof(Elf64_Shdr)))
+	{
+		return ft_put_error("Corrupted file");
+	}
+
+
+
+	// Elf64_Shdr *symbols_table = NULL;
+    // for (int i = 0; i < woody->Ehdr->e_shnum; i++) {
+	// 	if (Shdr[i].sh_type == SHT_SYMTAB) {
+    //         symbols_table = fetch(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 (!fetch(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 *)fetch(woody->file, woody->file_size, Shdr[woody->Ehdr->e_shstrndx].sh_offset, 0);
+	// if (Sshstrtab == NULL)
+	// 	return ft_put_error("Corrupted file");
+
+    // Elf64_Shdr *strtab_header = (Elf64_Shdr *)fetch(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 = fetch(woody->file, woody->file_size, strtab_header->sh_offset, 0);
+	// if (strtab == NULL)
+	// 	return ft_put_error("Corrupted file");
+    // Elf64_Sym *symbols = (Elf64_Sym *)fetch(woody->file, woody->file_size, symbols_table->sh_offset, sizeof(Elf64_Sym));
+	// if (symbols == NULL)
+	// 	return ft_put_error("Corrupted file");
+
+	return EXIT_SUCCESS;
+}
+
+int prepare_injection(t_efl_content *woody)
+{
+	int elf_statut = get_elf_sections(woody);
+	if (elf_statut)
+		return elf_statut;
+
+	inject(woody);
+
+	char *woody_file;
+	if (!(woody_file = malloc(woody->file_size)))
+		return ft_put_error("Allocation error");
+
+	ft_memcpy(woody_file, woody->file, woody->file_size);
+
+	// encrypt(woody_file, strtab_header->sh_offset , strtab_header->sh_size);
+	munmap(woody_file, woody->file_size);
+	save_elf("woody", woody_file, woody->file_size);
+	free(woody_file);
 	return EXIT_SUCCESS;
 }