ELF header read

.gdb_history

@@ -0,0 +1,3 @@
+file helpelf
+r
+q

helper.c

@@ -0,0 +1,90 @@
+// 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;
+}

makefile

@@ -0,0 +1,8 @@
+all:
+	gcc -Wall -Wextra helper.c -g -o helpelf
+
+install:
+	sudo cp helpelf /usr/bin/helpelf
+
+clean:
+	rm helpelf