ELF header解析

1. ELF base type
/* 32-bit ELF base types. */
typedef __u32 Elf32_Addr;
typedef __u16 Elf32_Half;
typedef __u32 Elf32_Off;
typedef __s32 Elf32_Sword;
typedef __u32 Elf32_Word;

/* 64-bit ELF base types. */
typedef __u64 Elf64_Addr;
typedef __u16 Elf64_Half;
typedef __s16 Elf64_SHalf;
typedef __u64 Elf64_Off;
typedef __s32 Elf64_Sword;
typedef __u32 Elf64_Word;
typedef __u64 Elf64_Xword;
typedef __s64 Elf64_Sxword;

2. ELF header
typedef struct elf32_hdr{
  unsigned char e_ident[EI_NIDENT];
  Elf32_Half e_type;
  Elf32_Half e_machine;
  Elf32_Word e_version;
  Elf32_Addr e_entry;  /* Entry point */
  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;
} Elf32_Ehdr;

可用"readelf -h"命令dump出ELF header

3. Program header
typedef struct elf32_phdr{
  Elf32_Word p_type;
  Elf32_Off p_offset;
  Elf32_Addr p_vaddr;
  Elf32_Addr p_paddr;
  Elf32_Word p_filesz;
  Elf32_Word p_memsz;
  Elf32_Word p_flags;
  Elf32_Word p_align;
} Elf32_Phdr;

可用"readelf -l"命令dump出Program header

4. Section header
typedef struct elf32_shdr {
  Elf32_Word sh_name;
  Elf32_Word sh_type;
  Elf32_Word sh_flags;
  Elf32_Addr sh_addr;
  Elf32_Off sh_offset;
  Elf32_Word sh_size;
  Elf32_Word sh_link;
  Elf32_Word sh_info;
  Elf32_Word sh_addralign;
  Elf32_Word sh_entsize;
} Elf32_Shdr;

可用"readelf -S"命令dump出Section header，sh_name可由第e_shstrndx取得，e_shstrndx指向[27] .shstrta。

5. Symbol talbe
typedef struct elf32_sym{
  Elf32_Word st_name;
  Elf32_Addr st_value;
  Elf32_Word st_size;
  unsigned char st_info;
  unsigned char st_other;
  Elf32_Half st_shndx;
} Elf32_Sym;

可用"readelf -s"命令dump出Symbol table，st_name可由[28] .symtab的sh_link取得，sh_link指向[29] .strtab。

6. 參考來源
http://www.cirosantilli.com/elf-hello-world/
https://ctf-wiki.github.io/ctf-wiki/executable/elf/elf_structure.html