Diff between ELF32/64

helper.c

@@ -1,90 +0,0 @@
-// goal:
-// replace "file" + "checksec"
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <errno.h>
-#include <stdint.h>
-#include <string.h>
-
-#define MAX_FILENAME   256
-#define EI_NIDENT      16
-#define MAX_HEADER_LEN 2048
-
-#define Elf32_Half uint16_t
-#define Elf32_Word uint32_t
-#define Elf32_Addr uint32_t
-#define Elf32_Off  uint32_t
-
-struct Elf32_Ehdr
-{
-	unsigned char e_ident[EI_NIDENT];
-	Elf32_Half e_type;
-	Elf32_Half e_machine;
-	Elf32_Word e_version;
-	Elf32_Addr e_entry; 
-	Elf32_Off e_phoff;
-	Elf32_Off e_shoff;
-	Elf32_Word e_flags;
-	Elf32_Half e_ehsize;
-	Elf32_Half e_phentsize;
-	Elf32_Half e_phnum;
-	Elf32_Half e_shentsize;
-	Elf32_Half e_shnum;
-	Elf32_Half e_shstrndx;
-};
-
-int parse_elf_header32(struct Elf32_Ehdr* header, FILE* fp)
-{
-	fread(header, sizeof(struct Elf32_Ehdr), 1, fp);
-	return EXIT_SUCCESS;
-}
-
-int main(int argc, char* argv[])
-{	
-	// Accessing file arg
-	if (argc < 2)
-	{
-		printf("Usage: %s <elf>\n", argv[0]);
-		return -EINVAL;
-	}
-
-	char* filename = argv[1];
-
-	// 0. is ELF32 or ELF64 ???
-	// 1. create ELF header struct
-	// 2. populate ELF header struct
-	// 3. display ELF header struct	
-
-	if (!filename)
-	{
-		printf("Error parsing filename.\n");
-		return -EINVAL;
-	}
-	
-	FILE* elf_file = fopen(filename, "rb");
-
-	if (!elf_file)
-	{
-		printf("Couldn't open file '%s'\n", filename);
-		return -ENOENT;
-	}
-
-	struct Elf32_Ehdr elf_header = {0};	
-	int res = parse_elf_header32(&elf_header, elf_file);
-	if (res)
-	{
-		printf("Error parsing ELF header.\n");
-		return -EINVAL;
-	}
-
-	if (!(memcmp(elf_header.e_ident, "\177ELF", 4) == 0))
-	{
-		printf("Not an ELF file..\n");
-		return -EINVAL;
-	}
-
-	printf("ELF file\n");
-	
-	return EXIT_SUCCESS;
-}

main.c

@@ -0,0 +1,164 @@
+// goal:
+// replace "file" + "checksec"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
+
+#define MAX_FILENAME   256
+#define EI_NIDENT      16
+#define MAX_HEADER_LEN 2048
+
+#define Elf32_Half uint16_t
+#define Elf32_Word uint32_t
+#define Elf32_Addr uint32_t
+#define Elf32_Off  uint32_t
+
+#define Elf64_Half uint32_t
+#define Elf64_Word uint64_t
+#define Elf64_Addr uint64_t
+#define Elf64_Off  uint64_t
+
+struct Elf32_Ehdr
+{
+	unsigned char e_ident[EI_NIDENT];
+	Elf32_Half e_type;
+	Elf32_Half e_machine;
+	Elf32_Word e_version;
+	Elf32_Addr e_entry; 
+	Elf32_Off e_phoff;
+	Elf32_Off e_shoff;
+	Elf32_Word e_flags;
+	Elf32_Half e_ehsize;
+	Elf32_Half e_phentsize;
+	Elf32_Half e_phnum;
+	Elf32_Half e_shentsize;
+	Elf32_Half e_shnum;
+	Elf32_Half e_shstrndx;
+};
+
+struct Elf64_Ehdr
+{
+	unsigned char e_ident[EI_NIDENT];
+	Elf64_Half e_type;
+	Elf64_Half e_machine;
+	Elf64_Word e_version;
+	Elf64_Addr e_entry; 
+	Elf64_Off e_phoff;
+	Elf64_Off e_shoff;
+	Elf64_Word e_flags;
+	Elf64_Half e_ehsize;
+	Elf64_Half e_phentsize;
+	Elf64_Half e_phnum;
+	Elf64_Half e_shentsize;
+	Elf64_Half e_shnum;
+	Elf64_Half e_shstrndx;
+};
+
+int parse_elf_header32(struct Elf32_Ehdr* header, FILE* fp)
+{
+	if (!fread(header, sizeof(struct Elf32_Ehdr), 1, fp))
+	{
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int parse_elf_header64(struct Elf64_Ehdr* header, FILE* fp)
+{
+	if (!fread(header, sizeof(struct Elf64_Ehdr), 1, fp))
+	{
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int read_elf_magic(FILE* fp)
+{
+	char buf[5] = {0};
+	fread(buf, 1, 4, fp);
+	if (memcmp(buf, "\177ELF", 4) == 0) return 1;
+	return 0;
+}
+
+void display_elf32(struct Elf32_Ehdr* header)
+{
+	printf("32-bit ELF\n");
+}
+
+void display_elf64(struct Elf64_Ehdr* header)
+{
+	printf("64-bit ELF\n");
+}
+
+unsigned char read_elf_obj_size(FILE* fp)
+{
+	unsigned char local_elf_obj_size = 0;
+	fseek(fp, 4, SEEK_SET);
+	fread(&local_elf_obj_size, 1, 1, fp);
+	rewind(fp);
+	return local_elf_obj_size;
+}
+
+int main(int argc, char* argv[])
+{
+	// Argument processing	
+	if (argc < 2)
+	{
+		printf("Usage: %s <elf>\n", argv[0]);
+		return -EINVAL;
+	}
+
+	char* filename = argv[1];
+	if (!filename)
+	{
+		printf("Error parsing filename.\n");
+		return -EINVAL;
+	}
+	
+	FILE* elf_file = fopen(filename, "rb");
+	if (!elf_file)
+	{
+		printf("Couldn't open file '%s'\n", filename);
+		return -ENOENT;
+	}
+
+	int is_elf = read_elf_magic(elf_file);
+	if (!is_elf)
+	{
+		printf("Not a valid ELF file.\n");
+		return -EINVAL;
+	}
+
+	// ELF32 or ELF64?
+	unsigned char elf_obj_size = read_elf_obj_size(elf_file);
+
+	switch(elf_obj_size)
+	{
+		case 0x01:
+			struct Elf32_Ehdr elf32_header = {0};
+			if (parse_elf_header32(&elf32_header, elf_file))
+			{
+				printf("Failed to parse 32-bit ELF header\n");
+				return -EINVAL;
+			}
+			display_elf32(&elf32_header);
+			break;
+		case 0x02:
+			struct Elf64_Ehdr elf64_header = {0};
+			if (parse_elf_header64(&elf64_header, elf_file))
+			{
+				printf("Failed to parse 64-bit ELF header\n");
+				return -EINVAL;
+			}
+			display_elf64(&elf64_header);
+			break;
+		default:
+			printf("Invalid ELF object size\n");
+			return -EINVAL;
+	}
+
+	return EXIT_SUCCESS;
+}

makefile

@@ -1,5 +1,5 @@
 all:
-	gcc -Wall -Wextra helper.c -g -o helpelf
+	gcc -Wall -Wextra main.c -g -o helpelf
 
 install:
 	sudo cp helpelf /usr/bin/helpelf