src/digest_md5.c

   1 #include <glib.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4
   5 #include "appimage/appimage_shared.h"
   6 #include "getsection.h"
   7
   8
   9 bool compare_byte_buffers(const char* buf1, const char* buf2, size_t num_bytes) {
  10     for (size_t i = 0; i < num_bytes; i++) {
  11         if (buf1[i] != buf2[i]) {
  12             return false;
  13         }
  14     }
  15
  16     return true;
  17 }
  18
  19
  20 int main(int argc, char* argv[]) {
  21     if (argc != 2) {
  22         printf("Usage: %s <my.AppImage>\n", argv[0]);
  23         printf("\n");
  24         printf("Calculate AppImage MD5 digest, and compare it to embedded value (if available)\n");
  25     }
  26
  27     const char* fname = argv[1];
  28     if (!g_file_test(fname, G_FILE_TEST_IS_REGULAR)) {
  29         fprintf(stderr, "No such file or directory: %s\n", fname);
  30         return 1;
  31     }
  32
  33     static const int digest_size = 16;
  34
  35     // first, calculate MD5 digest using algorithm in libappimage
  36     char expected_digest[digest_size];
  37
  38     if (!appimage_type2_digest_md5(fname, expected_digest)) {
  39         fprintf(stderr, "Could not calculate MD5 digest\n");
  40         return 1;
  41     }
  42
  43     // print hex encoded digest
  44     char* hexlified_expected_digest = appimage_hexlify(expected_digest, digest_size);
  45     printf("calculated: %s\n", hexlified_expected_digest);
  46     free(hexlified_expected_digest);
  47
  48     unsigned long offset = 0, length = 0;
  49
  50     static const char section_name[] = ".digest_md5";
  51
  52     if (!appimage_get_elf_section_offset_and_length(fname, section_name, &offset, &length) || offset == 0 || length == 0) {
  53         fprintf(stderr, "Could not find %s section in file\n", section_name);
  54         return 1;
  55     }
  56
  57     if (length < digest_size) {
  58         fprintf(stderr,
  59             "Invalid section length for section %s: expected %d bytes, found %lu bytes\n",
  60             section_name, digest_size, length
  61         );
  62         return 1;
  63     }
  64
  65     char embedded_digest[digest_size];
  66     FILE* fp = fopen(fname, "r");
  67
  68     if (fp == NULL) {
  69         fprintf(stderr, "Failed to open AppImage for writing");
  70         return 1;
  71     }
  72
  73     if (fseek(fp, offset, SEEK_SET) != 0) {
  74         fprintf(stderr, "Failed to read embedded digest: failed to seek to offset\n");
  75         fclose(fp);
  76         return 1;
  77     }
  78
  79     if (fread(embedded_digest, sizeof(char), digest_size, fp) != digest_size) {
  80         fprintf(stderr, "Failed to read embedded digest: read invalid amount of bytes from file\n");
  81         fclose(fp);
  82         return 1;
  83     }
  84
  85     fclose(fp);
  86
  87     char* hexlified_embedded_digest = appimage_hexlify(embedded_digest, digest_size);
  88     printf("  embedded: %s\n", hexlified_embedded_digest);
  89     free(hexlified_embedded_digest);
  90
  91     if (compare_byte_buffers(expected_digest, embedded_digest, digest_size)) {
  92         printf("Digests match\n");
  93         return 0;
  94     } else {
  95         printf("Digests don't match!");
  96         return 1;
  97     }
  98 }