/****************
* Decrypt the data, specified by ED with the key DEK.
*/
int
decrypt_data( void *procctx, PKT_encrypted *ed, DEK *dek )
{
decode_filter_ctx_t dfx;
byte *p;
int rc=0, c, i;
byte temp[32];
unsigned blocksize;
unsigned nprefix;
dfx = xtrycalloc (1, sizeof *dfx);
if (!dfx)
return gpg_error_from_syserror ();
dfx->refcount = 1;
if ( opt.verbose && !dek->algo_info_printed )
{
if (!openpgp_cipher_test_algo (dek->algo))
log_info (_("%s encrypted data\n"),
openpgp_cipher_algo_name (dek->algo));
else
log_info (_("encrypted with unknown algorithm %d\n"), dek->algo );
dek->algo_info_printed = 1;
}
{
char buf[20];
snprintf (buf, sizeof buf, "%d %d", ed->mdc_method, dek->algo);
write_status_text (STATUS_DECRYPTION_INFO, buf);
}
rc = openpgp_cipher_test_algo (dek->algo);
if (rc)
goto leave;
blocksize = openpgp_cipher_get_algo_blklen (dek->algo);
if ( !blocksize || blocksize > 16 )
log_fatal ("unsupported blocksize %u\n", blocksize );
nprefix = blocksize;
if ( ed->len && ed->len < (nprefix+2) )
BUG();
if ( ed->mdc_method )
{
if (gcry_md_open (&dfx->mdc_hash, ed->mdc_method, 0 ))
BUG ();
if ( DBG_HASHING )
gcry_md_debug (dfx->mdc_hash, "checkmdc");
}
rc = openpgp_cipher_open (&dfx->cipher_hd, dek->algo,
GCRY_CIPHER_MODE_CFB,
(GCRY_CIPHER_SECURE
| ((ed->mdc_method || dek->algo >= 100)?
0 : GCRY_CIPHER_ENABLE_SYNC)));
if (rc)
{
/* We should never get an error here cause we already checked
* that the algorithm is available. */
BUG();
}
/* log_hexdump( "thekey", dek->key, dek->keylen );*/
rc = gcry_cipher_setkey (dfx->cipher_hd, dek->key, dek->keylen);
if ( gpg_err_code (rc) == GPG_ERR_WEAK_KEY )
{
log_info(_("WARNING: message was encrypted with"
" a weak key in the symmetric cipher.\n"));
rc=0;
}
else if( rc )
{
log_error("key setup failed: %s\n", g10_errstr(rc) );
goto leave;
}
if (!ed->buf)
{
log_error(_("problem handling encrypted packet\n"));
goto leave;
}
gcry_cipher_setiv (dfx->cipher_hd, NULL, 0);
if ( ed->len )
{
for (i=0; i < (nprefix+2) && ed->len; i++, ed->len-- )
{
if ( (c=iobuf_get(ed->buf)) == -1 )
break;
else
temp[i] = c;
}
}
else
{
for (i=0; i < (nprefix+2); i++ )
if ( (c=iobuf_get(ed->buf)) == -1 )
break;
else
temp[i] = c;
}
gcry_cipher_decrypt (dfx->cipher_hd, temp, nprefix+2, NULL, 0);
gcry_cipher_sync (dfx->cipher_hd);
p = temp;
/* log_hexdump( "prefix", temp, nprefix+2 ); */
if (dek->symmetric
&& (p[nprefix-2] != p[nprefix] || p[nprefix-1] != p[nprefix+1]) )
{
rc = gpg_error (GPG_ERR_BAD_KEY);
goto leave;
}
if ( dfx->mdc_hash )
gcry_md_write (dfx->mdc_hash, temp, nprefix+2);
dfx->refcount++;
if ( ed->mdc_method )
iobuf_push_filter ( ed->buf, mdc_decode_filter, dfx );
else
iobuf_push_filter ( ed->buf, decode_filter, dfx );
proc_packets ( procctx, ed->buf );
ed->buf = NULL;
if ( ed->mdc_method && dfx->eof_seen == 2 )
rc = gpg_error (GPG_ERR_INV_PACKET);
else if ( ed->mdc_method )
{
/* We used to let parse-packet.c handle the MDC packet but this
turned out to be a problem with compressed packets: With old
style packets there is no length information available and
the decompressor uses an implicit end. However we can't know
this implicit end beforehand (:-) and thus may feed the
decompressor with more bytes than actually needed. It would
be possible to unread the extra bytes but due to our weird
iobuf system any unread is non reliable due to filters
already popped off. The easy and sane solution is to care
about the MDC packet only here and never pass it to the
packet parser. Fortunatley the OpenPGP spec requires a
strict format for the MDC packet so that we know that 22
bytes are appended. */
int datalen = gcry_md_get_algo_dlen (ed->mdc_method);
assert (dfx->cipher_hd);
assert (dfx->mdc_hash);
gcry_cipher_decrypt (dfx->cipher_hd, dfx->defer, 22, NULL, 0);
gcry_md_write (dfx->mdc_hash, dfx->defer, 2);
gcry_md_final (dfx->mdc_hash);
if (dfx->defer[0] != '\xd3' || dfx->defer[1] != '\x14' )
{
log_error("mdc_packet with invalid encoding\n");
rc = gpg_error (GPG_ERR_INV_PACKET);
}
else if (datalen != 20
|| memcmp (gcry_md_read (dfx->mdc_hash, 0),
dfx->defer+2,datalen ))
rc = gpg_error (GPG_ERR_BAD_SIGNATURE);
/* log_printhex("MDC message:", dfx->defer, 22); */
/* log_printhex("MDC calc:", gcry_md_read (dfx->mdc_hash,0), datalen); */
}
leave:
release_dfx_context (dfx);
return rc;
}
/* Check the signature on CERT using the ISSUER_CERT. This function
does only test the cryptographic signature and nothing else. It is
assumed that the ISSUER_CERT is valid. */
static gpg_error_t
check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
{
gpg_error_t err;
const char *algoid;
gcry_md_hd_t md;
int i, algo;
ksba_sexp_t p;
size_t n;
gcry_sexp_t s_sig, s_hash, s_pkey;
const char *s;
char algo_name[16+1]; /* hash algorithm name converted to lower case. */
int digestlen;
unsigned char *digest;
/* Hash the target certificate using the algorithm from that certificate. */
algoid = ksba_cert_get_digest_algo (cert);
algo = gcry_md_map_name (algoid);
if (!algo)
{
log_error (_("unknown hash algorithm '%s'\n"), algoid? algoid:"?");
return gpg_error (GPG_ERR_GENERAL);
}
s = gcry_md_algo_name (algo);
for (i=0; *s && i < sizeof algo_name - 1; s++, i++)
algo_name[i] = tolower (*s);
algo_name[i] = 0;
err = gcry_md_open (&md, algo, 0);
if (err)
{
log_error ("md_open failed: %s\n", gpg_strerror (err));
return err;
}
if (DBG_HASHING)
gcry_md_debug (md, "hash.cert");
err = ksba_cert_hash (cert, 1, HASH_FNC, md);
if (err)
{
log_error ("ksba_cert_hash failed: %s\n", gpg_strerror (err));
gcry_md_close (md);
return err;
}
gcry_md_final (md);
/* Get the signature value out of the target certificate. */
p = ksba_cert_get_sig_val (cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
if (!n)
{
log_error ("libksba did not return a proper S-Exp\n");
gcry_md_close (md);
ksba_free (p);
return gpg_error (GPG_ERR_BUG);
}
if (DBG_CRYPTO)
{
int j;
log_debug ("signature value:");
for (j=0; j < n; j++)
log_printf (" %02X", p[j]);
log_printf ("\n");
}
err = gcry_sexp_sscan ( &s_sig, NULL, p, n);
ksba_free (p);
if (err)
{
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (err));
gcry_md_close (md);
return err;
}
/* Get the public key from the issuer certificate. */
p = ksba_cert_get_public_key (issuer_cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
if (!n)
{
log_error ("libksba did not return a proper S-Exp\n");
gcry_md_close (md);
ksba_free (p);
gcry_sexp_release (s_sig);
return gpg_error (GPG_ERR_BUG);
}
err = gcry_sexp_sscan ( &s_pkey, NULL, p, n);
ksba_free (p);
if (err)
{
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (err));
gcry_md_close (md);
gcry_sexp_release (s_sig);
return err;
}
/* Prepare the values for signature verification. At this point we
have these values:
S_PKEY - S-expression with the issuer's public key.
S_SIG - Signature value as given in the certrificate.
MD - Finalized hash context with hash of the certificate.
ALGO_NAME - Lowercase hash algorithm name
*/
digestlen = gcry_md_get_algo_dlen (algo);
digest = gcry_md_read (md, algo);
if (pk_algo_from_sexp (s_pkey) == GCRY_PK_DSA)
{
if (digestlen != 20)
{
log_error (_("DSA requires the use of a 160 bit hash algorithm\n"));
gcry_md_close (md);
gcry_sexp_release (s_sig);
gcry_sexp_release (s_pkey);
return gpg_error (GPG_ERR_INTERNAL);
}
if ( gcry_sexp_build (&s_hash, NULL, "(data(flags raw)(value %b))",
(int)digestlen, digest) )
BUG ();
}
else /* Not DSA. */
{
if ( gcry_sexp_build (&s_hash, NULL, "(data(flags pkcs1)(hash %s %b))",
algo_name, (int)digestlen, digest) )
BUG ();
}
err = gcry_pk_verify (s_sig, s_hash, s_pkey);
if (DBG_X509)
log_debug ("gcry_pk_verify: %s\n", gpg_strerror (err));
gcry_md_close (md);
gcry_sexp_release (s_sig);
gcry_sexp_release (s_hash);
gcry_sexp_release (s_pkey);
return err;
}
static void
write_header (cipher_filter_context_t *cfx, iobuf_t a)
{
gcry_error_t err;
PACKET pkt;
PKT_encrypted ed;
byte temp[18];
unsigned int blocksize;
unsigned int nprefix;
blocksize = openpgp_cipher_get_algo_blklen (cfx->dek->algo);
if ( blocksize < 8 || blocksize > 16 )
log_fatal ("unsupported blocksize %u\n", blocksize);
memset (&ed, 0, sizeof ed);
ed.len = cfx->datalen;
ed.extralen = blocksize + 2;
ed.new_ctb = !ed.len;
if (cfx->dek->use_mdc)
{
ed.mdc_method = DIGEST_ALGO_SHA1;
gcry_md_open (&cfx->mdc_hash, DIGEST_ALGO_SHA1, 0);
if (DBG_HASHING)
gcry_md_debug (cfx->mdc_hash, "creatmdc");
}
else if (!opt.no_mdc_warn)
{
log_info ("WARNING: "
"encrypting without integrity protection is dangerous\n");
}
write_status_printf (STATUS_BEGIN_ENCRYPTION, "%d %d",
ed.mdc_method, cfx->dek->algo);
init_packet (&pkt);
pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
pkt.pkt.encrypted = &ed;
if (build_packet( a, &pkt))
log_bug ("build_packet(ENCR_DATA) failed\n");
nprefix = blocksize;
gcry_randomize (temp, nprefix, GCRY_STRONG_RANDOM );
temp[nprefix] = temp[nprefix-2];
temp[nprefix+1] = temp[nprefix-1];
print_cipher_algo_note (cfx->dek->algo);
err = openpgp_cipher_open (&cfx->cipher_hd,
cfx->dek->algo,
GCRY_CIPHER_MODE_CFB,
(GCRY_CIPHER_SECURE
| ((cfx->dek->use_mdc || cfx->dek->algo >= 100)?
0 : GCRY_CIPHER_ENABLE_SYNC)));
if (err)
{
/* We should never get an error here cause we already checked,
* that the algorithm is available. */
BUG();
}
/* log_hexdump ("thekey", cfx->dek->key, cfx->dek->keylen); */
gcry_cipher_setkey (cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen);
gcry_cipher_setiv (cfx->cipher_hd, NULL, 0);
/* log_hexdump ("prefix", temp, nprefix+2); */
if (cfx->mdc_hash) /* Hash the "IV". */
gcry_md_write (cfx->mdc_hash, temp, nprefix+2 );
gcry_cipher_encrypt (cfx->cipher_hd, temp, nprefix+2, NULL, 0);
gcry_cipher_sync (cfx->cipher_hd);
iobuf_write (a, temp, nprefix+2);
cfx->short_blklen_warn = (blocksize < 16);
cfx->short_blklen_count = nprefix+2;
cfx->wrote_header = 1;
}
/* Check the signature on CERT using the ISSUER-CERT. This function
does only test the cryptographic signature and nothing else. It is
assumed that the ISSUER_CERT is valid. */
int
gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
{
const char *algoid;
gcry_md_hd_t md;
int rc, algo;
gcry_mpi_t frame;
ksba_sexp_t p;
size_t n;
gcry_sexp_t s_sig, s_hash, s_pkey;
algo = gcry_md_map_name ( (algoid=ksba_cert_get_digest_algo (cert)));
if (!algo)
{
log_error ("unknown hash algorithm '%s'\n", algoid? algoid:"?");
if (algoid
&& ( !strcmp (algoid, "1.2.840.113549.1.1.2")
||!strcmp (algoid, "1.2.840.113549.2.2")))
log_info (_("(this is the MD2 algorithm)\n"));
return gpg_error (GPG_ERR_GENERAL);
}
rc = gcry_md_open (&md, algo, 0);
if (rc)
{
log_error ("md_open failed: %s\n", gpg_strerror (rc));
return rc;
}
if (DBG_HASHING)
gcry_md_debug (md, "hash.cert");
rc = ksba_cert_hash (cert, 1, HASH_FNC, md);
if (rc)
{
log_error ("ksba_cert_hash failed: %s\n", gpg_strerror (rc));
gcry_md_close (md);
return rc;
}
gcry_md_final (md);
p = ksba_cert_get_sig_val (cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
if (!n)
{
log_error ("libksba did not return a proper S-Exp\n");
gcry_md_close (md);
ksba_free (p);
return gpg_error (GPG_ERR_BUG);
}
if (DBG_CRYPTO)
{
int j;
log_debug ("signature value:");
for (j=0; j < n; j++)
log_printf (" %02X", p[j]);
log_printf ("\n");
}
rc = gcry_sexp_sscan ( &s_sig, NULL, (char*)p, n);
ksba_free (p);
if (rc)
{
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc));
gcry_md_close (md);
return rc;
}
p = ksba_cert_get_public_key (issuer_cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
if (!n)
{
log_error ("libksba did not return a proper S-Exp\n");
gcry_md_close (md);
ksba_free (p);
gcry_sexp_release (s_sig);
return gpg_error (GPG_ERR_BUG);
}
rc = gcry_sexp_sscan ( &s_pkey, NULL, (char*)p, n);
ksba_free (p);
if (rc)
{
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc));
gcry_md_close (md);
gcry_sexp_release (s_sig);
return rc;
}
rc = do_encode_md (md, algo, pk_algo_from_sexp (s_pkey),
gcry_pk_get_nbits (s_pkey), s_pkey, &frame);
if (rc)
{
gcry_md_close (md);
gcry_sexp_release (s_sig);
gcry_sexp_release (s_pkey);
return rc;
}
/* put hash into the S-Exp s_hash */
if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
BUG ();
gcry_mpi_release (frame);
rc = gcry_pk_verify (s_sig, s_hash, s_pkey);
if (DBG_X509)
log_debug ("gcry_pk_verify: %s\n", gpg_strerror (rc));
gcry_md_close (md);
gcry_sexp_release (s_sig);
gcry_sexp_release (s_hash);
gcry_sexp_release (s_pkey);
return rc;
}
