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examples/peterglen/encdec.c

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/* =====[ encdec.c ]=========================================================
Description: Encryption excamples. Feasability study for diba
[Digital Bank].
Revisions:
REV DATE BY DESCRIPTION
---- ----------- ---------- ------------------------------
0.00 jul.14.2017 Peter Glen Initial version.
======================================================================= */
#include <signal.h>
#include "gcrypt.h"
#include "gcry.h"
#include "gsexp.h"
#include "zmalloc.h"
#include "getpass.h"
#include "base64.h"
//static int keysize = 2048;
static void myfunc(int sig)
{
printf("\nSignal %d (segment violation)\n", sig);
exit(111);
}
int main(int argc, char** argv)
{
signal(SIGSEGV, myfunc);
if (argc != 2) {
fprintf(stderr, "Usage: %s <rsa-keypair.key>\n", argv[0]);
xerr("Invalid arguments.");
}
printf("Showing mutated cypher text.\n");
gcrypt_init();
gcry_error_t err;
char* fname = argv[1];
FILE* lockf = fopen(fname, "rb");
if (!lockf) {
xerr2("fopen() on '%s' failed.", fname);
}
//int pkv = gcry_pk_map_name("rsa");
//printf("Public key algo: %d Name: '%s'\n", pkv, gcry_pk_algo_name(pkv) );
/* Read and decrypt the key pair from disk. */
unsigned int flen = getfsize(lockf);
zline2(__LINE__, __FILE__);
char* fbuf = zalloc(flen + 1);
if (!fbuf) {
xerr("malloc: could not allocate rsa buffer");
}
if (fread(fbuf, flen, 1, lockf) != 1) {
xerr("fread() on composit key failed");
}
fbuf[flen] = '\0';
zcheck(fbuf, __LINE__);
char *err_str;
int rsa_len = flen;
char *rsa_buf = decode_comp_key(fbuf, &rsa_len, &err_str);
if (!rsa_buf) {
xerr2("decode key failed. %s", err_str);
}
/* Grab a key pair password and create an AES context with it. */
char passwd[MAXPASSLEN]; int weak = TRUE;
getpassx passx;
passx.prompt = "Enter keypair pass:";
passx.pass = passwd;
passx.maxlen = MAXPASSLEN;
passx.minlen = 3;
passx.weak = TRUE;
passx.nodouble = TRUE;
int ret = getpass2(&passx);
if(ret < 0)
xerr("Error on password entry.");
gcry_cipher_hd_t aes_hd;
get_aes_ctx(&aes_hd, passwd, strlen(passwd));
err = gcry_cipher_decrypt(aes_hd, (unsigned char*) rsa_buf,
rsa_len, NULL, 0);
if (err) {
xerr("gcrypt: failed to decrypt key pair");
}
/* Load the key pair components into sexps. */
gcry_sexp_t rsa_keypair;
err = gcry_sexp_new(&rsa_keypair, rsa_buf, rsa_len, 0);
if(err)
{
xerr("gcrypt: failed to rate key pair S-expr (pass?)");
}
gcry_sexp_t pubk = gcry_sexp_find_token(rsa_keypair, "public-key", 0);
gcry_sexp_t privk = gcry_sexp_find_token(rsa_keypair, "private-key", 0);
if(privk == NULL)
{
xerr("No private key here.");
}
//printf("keylen %d\n", gcry_pk_get_nbits(privk));
/* Create a message. */
gcry_mpi_t msg;
gcry_sexp_t data;
const unsigned char* ss = (const unsigned char*)
//"Hello world. Hello world. Hello world. Hello world. Hello world. Hello world. Hello world."
//"Hello world. Hello world. Hello world. Hello world. Hello world. Hello world. Hello world."
"Hello world. Hello world. Hello world. Hello world. Hello world. Hello world. Hello world.";
printf("Original message -> %d bytes \n'%s'\n", strlen(ss), (char*) ss);
err = gcry_mpi_scan(&msg, GCRYMPI_FMT_USG, ss,
strlen((const char*) ss), NULL);
if (err) {
xerr("failed to create a mpi from the message");
}
err = gcry_sexp_build(&data, NULL,
"(data (flags raw) (value %m))", msg);
if (err) {
xerr("failed to create a sexp from the message");
}
/* Encrypt the message. */
gcry_sexp_t ciph;
err = gcry_pk_encrypt(&ciph, data, pubk);
if (err) {
xerr("gcrypt: encryption failed");
}
gcry_mpi_t msg2;
gcry_sexp_t data2;
char *sss = strdup(ss);
sss[1] = 'f';
err = gcry_mpi_scan(&msg2, GCRYMPI_FMT_USG, sss,
strlen((const char*) sss), NULL);
err = gcry_sexp_build(&data2, NULL,
"(data (flags raw) (value %m))", msg2);
if (err) {
xerr("failed to create a sexp from the message");
}
gcry_sexp_t ciph2;
err = gcry_pk_encrypt(&ciph2, data2, pubk);
if (err) {
xerr("gcrypt: encryption failed");
}
printf("\n" "Cypher:\n");
gcry_sexp_t ddd = gcry_sexp_find_token(ciph, "a", 1);
print_sexp(ddd);
unsigned int plen = 0;
const char *ptr = gcry_sexp_nth_data(ddd, 1, &plen);
printf("\n" "Cypher2:\n");
gcry_sexp_t ddd2 = gcry_sexp_find_token(ciph2, "a", 1);
print_sexp(ddd2);
unsigned int plen2 = 0;
const char *ptr2 = gcry_sexp_nth_data(ddd2, 1, &plen2);
//dump_mem(ptr2, plen2);
/* Decrypt the message. */
gcry_sexp_t plain;
err = gcry_pk_decrypt(&plain, ciph, privk);
if (err) {
xerr("gcrypt: decryption failed");
}
gcry_mpi_t out_msg = gcry_sexp_nth_mpi(plain, 0, GCRYMPI_FMT_USG);
unsigned char *buffm;
int written;
err = gcry_mpi_aprint(GCRYMPI_FMT_USG, &buffm, &written, out_msg);
if (err) {
xerr("failed to stringify mpi");
}
printf("Decrypted message -> (%d bytes)\n'%s'\n", strlen(buffm), (char*) buffm);
/* Release contexts. */
gcry_mpi_release(msg);
gcry_mpi_release(out_msg);
gcry_sexp_release(rsa_keypair);
gcry_sexp_release(pubk);
gcry_sexp_release(privk);
gcry_sexp_release(data);
gcry_sexp_release(ciph);
gcry_sexp_release(plain);
gcry_cipher_close(aes_hd);
zfree(rsa_buf);
//fclose(lockf);
return 0;
}