getsection.c

   1 #include <fcntl.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <sys/mman.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7 #include "light_elf.h"
   8
   9 /* Return the offset, and the length of an ELF section with a given name in a given ELF file */
  10 int get_elf_section_offset_and_lenghth(char* fname, char* section_name, unsigned long *offset, unsigned long *length)
  11 {
  12     uint8_t *data;
  13     int i;
  14     int fd = open(fname, O_RDONLY);
  15     data = mmap(NULL, lseek(fd, 0, SEEK_END), PROT_READ, MAP_SHARED, fd, 0);
  16
  17 // optionally add more architectures for 32-bit builds so that it doesn't fall back to Elf64_*
  18 // see e.g. https://sourceforge.net/p/predef/wiki/Architectures/ for more predefined macro names
  19 #if __SIZEOF_POINTER__ == 4
  20     Elf32_Ehdr *elf;
  21     Elf32_Shdr *shdr;
  22     elf = (Elf32_Ehdr *) data;
  23     shdr = (Elf32_Shdr *) (data + elf->e_shoff);
  24 #elif __SIZEOF_POINTER__ == 8
  25     Elf64_Ehdr *elf;
  26     Elf64_Shdr *shdr;
  27     elf = (Elf64_Ehdr *) data;
  28     shdr = (Elf64_Shdr *) (data + elf->e_shoff);
  29 #else
  30     #error Platforms other than 32-bit/64-bit are currently not supported!
  31 #endif
  32
  33     char *strTab = (char *)(data + shdr[elf->e_shstrndx].sh_offset);
  34     for(i = 0; i <  elf->e_shnum; i++) {
  35         if(strcmp(&strTab[shdr[i].sh_name], section_name) == 0) {
  36         *offset = shdr[i].sh_offset;
  37         *length = shdr[i].sh_size;
  38         }
  39     }
  40     close(fd);
  41     return(0);
  42 }
  43
  44 void print_hex(char* fname, unsigned long offset, unsigned long length){
  45     uint8_t *data;
  46     unsigned long k;
  47     int fd = open(fname, O_RDONLY);
  48     data = mmap(NULL, lseek(fd, 0, SEEK_END), PROT_READ, MAP_SHARED, fd, 0);
  49     close(fd);
  50     for (k = offset; k < offset + length; k++) {
  51         printf("%x", data[k]);
  52         }
  53         printf("\n");
  54 }
  55
  56 void print_binary(char* fname, unsigned long offset, unsigned long length){
  57     uint8_t *data;
  58     unsigned long k;
  59     int fd = open(fname, O_RDONLY);
  60     data = mmap(NULL, lseek(fd, 0, SEEK_END), PROT_READ, MAP_SHARED, fd, 0);
  61     close(fd);
  62     for (k = offset; k < offset + length; k++) {
  63         printf("%c", data[k]);
  64         }
  65         printf("\n");
  66 }
  67
  68 /*
  69 int main(int ac, char **av)
  70 {
  71     unsigned long offset = 0;
  72     unsigned long length = 0; // Where the function will store the result
  73     char* segment_name;
  74     segment_name = ".upd_info";
  75     int res = get_elf_section_offset_and_lenghth(av[1], segment_name, &offset, &length);
  76     printf("segment_name: %s\n", segment_name);
  77     printf("offset: %lu\n", offset);
  78     printf("length: %lu\n", length);
  79     print_hex(av[1], offset, length);
  80     print_binary(av[1], offset, length);
  81     segment_name = ".sha256_sig";
  82     printf("segment_name: %s\n", segment_name);
  83     res = get_elf_section_offset_and_lenghth(av[1], segment_name, &offset, &length);
  84     printf("offset: %lu\n", offset);
  85     printf("length: %lu\n", length);
  86     print_hex(av[1], offset, length);
  87     print_binary(av[1], offset, length);
  88     return res;
  89 }
  90 */