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decryptor.c
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decryptor.c
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#include <stdio.h>
#include <stdlib.h>
#include <gcrypt.h>
#include <assert.h>
char * decrypt(char *filename, char *key) {
gcry_cipher_hd_t handle;
gcry_error_t err = 0;
FILE *f = fopen(filename, "rb");
fseek(f, 0, SEEK_END);
long fsize = ftell(f) - 16;
// first 16 bytes are the IV
fseek(f, 16, SEEK_SET); /* same as rewind(f); */
char *string = malloc(fsize + 1);
fread(string, fsize, 1, f);
string[fsize] = 0;
char iv[17];
rewind(f);
fread(iv, 16, 1, f);
iv[16] = 0;
fclose(f);
gcry_check_version (NULL);
gcry_control( GCRYCTL_DISABLE_SECMEM_WARN );
//gcry_control( GCRYCTL_INIT_SECMEM, 16384, 0 );
err = gcry_cipher_open (&handle, GCRY_CIPHER_TWOFISH128,GCRY_CIPHER_MODE_CFB,0);
if (err)
{
fprintf (stderr, "Failure: %s/%s\n",
gcry_strsource (err),
gcry_strerror (err));
}
err = gcry_cipher_setkey (handle, key ,16);
if (err)
{
fprintf (stderr, "Key Failure: %s/%s\n",
gcry_strsource (err),
gcry_strerror (err));
}
err = gcry_cipher_setiv(handle, iv, 16);
if (err)
{
fprintf (stderr, "IV Failure: %s/%s\n",
gcry_strsource (err),
gcry_strerror (err));
}
char *foo;
foo = malloc(fsize+1);
err = gcry_cipher_decrypt(handle, foo, fsize, string, fsize);
if (err) {
fprintf(stderr, "Decrypt failure%s/%s\n",
gcry_strsource(err),
gcry_strerror(err));
}
gcry_cipher_close(handle);
return foo;
}