├── .gitignore
├── screenshot.png
├── Makefile
├── README.md
└── ELFappend.c


/.gitignore:
--------------------------------------------------------------------------------
1 | ELFappend
2 | 


--------------------------------------------------------------------------------
/screenshot.png:
--------------------------------------------------------------------------------
https://raw.githubusercontent.com/droberson/ELFappend/HEAD/screenshot.png


--------------------------------------------------------------------------------
/Makefile:
--------------------------------------------------------------------------------
1 | all:
2 | 	gcc -o ELFappend ELFappend.c
3 | 
4 | clean:
5 | 	rm -rf ELFappend
6 | 
7 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
 1 | # ELFappend
 2 | 
 3 | This is a quick demonstration to show how one would append and extract
 4 | data to an ELF binary.
 5 | 
 6 | This would be useful for appending the source code to a binary for
 7 | future reference, including supplementary stuff with an ELF, or a
 8 | number of other scenarios.
 9 | 
10 | ## Usage
11 | 
12 | ![Screenshot](https://github.com/droberson/ELFappend/blob/master/screenshot.png)
13 | 


--------------------------------------------------------------------------------
/ELFappend.c:
--------------------------------------------------------------------------------
 1 | #include <stdio.h>
 2 | #include <elf.h>
 3 | #include <sys/types.h>
 4 | #include <sys/stat.h>
 5 | #include <unistd.h>
 6 | #include <stdlib.h>
 7 | #include <limits.h>
 8 | #include <errno.h>
 9 | #include <string.h>
10 | #include <fcntl.h>
11 | 
12 | 
13 | /* get_file_size() -- returns size of file in bytes
14 |  */
15 | size_t get_file_size(const char *filename) {
16 |   struct stat s;
17 | 
18 |   if (stat(filename, &s) == -1) {
19 |     fprintf(stderr, "Failed to stat file %s: %s\n", filename, strerror(errno));
20 |     return -1;
21 |   }
22 | 
23 |   return s.st_size;
24 | }
25 | 
26 | 
27 | /* get_elf_size() -- returns length of ELF data for a file.
28 |  *
29 |  * TODO: validate ELF file
30 |  *       figure out actual header size of ELF (malloc)
31 |  */
32 | size_t get_elf_size(const char *progname) {
33 |   int fd;
34 |   void *ELFheaderdata;
35 |   Elf64_Ehdr *ELFheader;
36 |   size_t elfsize;
37 | 
38 | 
39 |   ELFheaderdata = malloc(64);
40 | 
41 |   fd = open(progname, O_RDONLY);
42 |   if (fd == -1) {
43 |     fprintf(stderr, "Failed to open input file %s: %s\n",
44 | 	    progname,
45 | 	    strerror(errno));
46 |     fprintf(stderr, "Exiting.\n");
47 | 
48 |     exit(EXIT_FAILURE);
49 |   }
50 | 
51 |   read(fd, ELFheaderdata, 64);
52 |   ELFheader = (Elf64_Ehdr *)ELFheaderdata;
53 | 
54 | 
55 |   elfsize = ELFheader->e_shoff + (ELFheader->e_shnum * ELFheader->e_shentsize);
56 |   
57 |   close(fd);
58 |   free(ELFheaderdata);
59 | 
60 |   return elfsize;
61 | }
62 | 
63 | int main(int argc, char *argv[]) {
64 |   char ch;
65 |   FILE *fp;
66 |   char progname[PATH_MAX];
67 |   size_t filesize;
68 |   size_t elfsize;
69 | 
70 |   realpath("/proc/self/exe", progname);
71 |   printf("Hello there! I am %s\n", progname);
72 | 
73 |   filesize = get_file_size(progname);
74 |   printf("I am %ld bytes long\n", filesize);
75 | 
76 |   elfsize = get_elf_size(progname);
77 |   printf("%ld bytes is valid ELF data.\n", elfsize);
78 | 
79 |   printf("This means that there are %ld extra bytes at the end of this file\n",
80 | 	 filesize - elfsize);
81 | 
82 |   if (filesize - elfsize > 0) {
83 |     printf("dumping data....\n");
84 | 
85 |     fp = fopen(progname, "rb");
86 |     if (fp == NULL) {
87 |       printf("Unable to open %s for reading: %s", progname, strerror(errno));
88 |       exit(EXIT_FAILURE);
89 |     }
90 |     
91 |     fseek(fp, elfsize, SEEK_SET);
92 | 
93 |     while (fread(&ch, 1, 1, fp))
94 |       fprintf(stderr, "%c", ch);
95 | 
96 |     fclose(fp);
97 |   }
98 | }
99 | 


--------------------------------------------------------------------------------