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gpg: Add arg session_algo to pk_decrypt. 

* common/kem.c: Move constants to the top.  Add some documentation.
* g10/pkglue.c (pk_encrypt): Add arguments session_key and factor code
out to ...
(do_encrypt_rsa_elg): here,
(do_encrypt_ecdh): and here,
(do_encrypt_kem): and here.
* g10/encrypt.c (write_pubkey_enc): Call with session key algorithm.
--

This makes it easier to review the code.
This commit is contained in:
Werner Koch 2024-04-15 09:23:16 +02:00
parent 35ef87d8d9
commit 4c20d2d273
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
4 changed files with 188 additions and 134 deletions
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32
common/kem.c
View File

@ -23,9 +23,10 @@
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copies of the GNU General Public License
* You should have received copies of the GNU General Public License
* and the GNU Lesser General Public License along with this program;
* if not, see <https://www.gnu.org/licenses/>.
* SPDX-License-Identifier: (LGPL-3.0-or-later OR GPL-2.0-or-later)
*/
#include <config.h>
@ -35,7 +36,18 @@
#include <gcrypt.h>
#include "mischelp.h"
/* domSeperation as per *PGP specs. */
#define KMAC_KEY "OpenPGPCompositeKeyDerivationFunction"
/* customizationString as per *PGP specs. */
#define KMAC_CUSTOM "KDF"
/* The blocksize used for Keccak by compute_kmac256. */
#define KECCAK512_BLOCKSIZE 136
static gpg_error_t
compute_kmac256 (void *digest, size_t digestlen,
const void *key, size_t keylen,
@ -163,14 +175,16 @@ gnupg_ecc_kem_kdf (void *kek, size_t kek_len,
return 0;
}
/* domSeperation */
#define KMAC_KEY "OpenPGPCompositeKeyDerivationFunction"
/* customizationString */
#define KMAC_CUSTOM "KDF"
/* Compute KEK by combining two KEMs. */
/* Compute KEK by combining two KEMs. The caller provides a buffer
* KEK allocated with size KEK_LEN which will receive the computed
* KEK. (ECC_SS, ECC_SS_LEN) is the shared secret of the first key.
* (ECC_CT, ECC_CT_LEN) is the ciphertext of the first key.
* (MLKEM_SS, ECC_SS_LEN) is the shared secret of the second key.
* (MLKEM_CT, MLKEM_CT_LEN) is the ciphertext of the second key.
* (FIXEDINFO, FIXEDINFO_LEN) is an octet string used to bind the KEK
* to a the key; for PGP we use the concatenation of the session key's
* algorithm id and the v5 fingerprint of the key.
*/
gpg_error_t
gnupg_kem_combiner (void *kek, size_t kek_len,
const void *ecc_ss, size_t ecc_ss_len,

2
g10/encrypt.c
View File

@ -1138,7 +1138,7 @@ write_pubkey_enc (ctrl_t ctrl,
* build_packet(). */
frame = encode_session_key (pk->pubkey_algo, dek,
pubkey_nbits (pk->pubkey_algo, pk->pkey));
rc = pk_encrypt (pk, frame, enc->data);
rc = pk_encrypt (pk, frame, dek->algo, enc->data);
gcry_mpi_release (frame);
if (rc)
log_error ("pubkey_encrypt failed: %s\n", gpg_strerror (rc) );

286
g10/pkglue.c
View File

@ -1,6 +1,7 @@
/* pkglue.c - public key operations glue code
* Copyright (C) 2000, 2003, 2010 Free Software Foundation, Inc.
* Copyright (C) 2014 Werner Koch
* Copyright (C) 2024 g10 Code GmbH.
*
* This file is part of GnuPG.
*
@ -16,6 +17,7 @@
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
* SPDX-License-Identifier: GPL-3.0-or-later
*/
#include <config.h>
@ -415,18 +417,120 @@ pk_verify (pubkey_algo_t pkalgo, gcry_mpi_t hash,
}
/* Core of the encryption for KEM algorithms. See pk_decrypt for a
* description of the arguments. */
static gpg_error_t
do_encrypt_kem (PKT_public_key *pk, gcry_mpi_t data, int seskey_algo,
gcry_mpi_t *resarr)
{
log_debug ("Implement Kyber encryption\n");
return gpg_error (GPG_ERR_NOT_IMPLEMENTED);
}
/*
* Emulate our old PK interface here - sometime in the future we might
* change the internal design to directly fit to libgcrypt. PK is is
* the OpenPGP public key packet, DATA is an MPI with the to be
* encrypted data, and RESARR receives the encrypted data. RESARRAY
* is expected to be an two item array which will be filled with newly
* allocated MPIs.
*/
gpg_error_t
pk_encrypt (PKT_public_key *pk, gcry_mpi_t data, gcry_mpi_t *resarr)
/* Core of the encryption for the ECDH algorithms. See pk_decrypt for
* a description of the arguments. */
static gpg_error_t
do_encrypt_ecdh (PKT_public_key *pk, gcry_mpi_t data, gcry_mpi_t *resarr)
{
gcry_mpi_t *pkey = pk->pkey;
gcry_sexp_t s_ciph = NULL;
gcry_sexp_t s_data = NULL;
gcry_sexp_t s_pkey = NULL;
gpg_error_t err;
gcry_mpi_t k = NULL;
char *curve = NULL;
int with_djb_tweak_flag;
gcry_mpi_t public = NULL;
gcry_mpi_t result = NULL;
byte fp[MAX_FINGERPRINT_LEN];
byte *shared = NULL;
byte *p;
size_t nshared;
unsigned int nbits;
err = pk_ecdh_generate_ephemeral_key (pkey, &k);
if (err)
goto leave;
curve = openpgp_oid_to_str (pkey[0]);
if (!curve)
{
err = gpg_error_from_syserror ();
goto leave;
}
with_djb_tweak_flag = openpgp_oid_is_cv25519 (pkey[0]);
/* Now use the ephemeral secret to compute the shared point. */
err = gcry_sexp_build (&s_pkey, NULL,
with_djb_tweak_flag ?
"(public-key(ecdh(curve%s)(flags djb-tweak)(q%m)))"
: "(public-key(ecdh(curve%s)(q%m)))",
curve, pkey[1]);
if (err)
goto leave;
/* Put K into a simplified S-expression. */
err = gcry_sexp_build (&s_data, NULL, "%m", k);
if (err)
goto leave;
/* Run encryption. */
err = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
if (err)
goto leave;
gcry_sexp_release (s_data); s_data = NULL;
gcry_sexp_release (s_pkey); s_pkey = NULL;
/* Get the shared point and the ephemeral public key. */
shared = get_data_from_sexp (s_ciph, "s", &nshared);
if (!shared)
{
err = gpg_error_from_syserror ();
goto leave;
}
err = sexp_extract_param_sos (s_ciph, "e", &public);
gcry_sexp_release (s_ciph); s_ciph = NULL;
if (DBG_CRYPTO)
{
log_debug ("ECDH ephemeral key:");
gcry_mpi_dump (public);
log_printf ("\n");
}
fingerprint_from_pk (pk, fp, NULL);
p = gcry_mpi_get_opaque (data, &nbits);
result = NULL;
err = pk_ecdh_encrypt_with_shared_point (shared, nshared, fp, p,
(nbits+7)/8, pkey, &result);
if (err)
goto leave;
resarr[0] = public; public = NULL;
resarr[1] = result; result = NULL;
leave:
gcry_mpi_release (public);
gcry_mpi_release (result);
xfree (shared);
gcry_sexp_release (s_ciph);
gcry_sexp_release (s_data);
gcry_sexp_release (s_pkey);
xfree (curve);
gcry_mpi_release (k);
return err;
}
/* Core of the encryption for RSA and Elgamal algorithms. See
* pk_decrypt for a description of the arguments. */
static gpg_error_t
do_encrypt_rsa_elg (PKT_public_key *pk, gcry_mpi_t data, gcry_mpi_t *resarr)
{
pubkey_algo_t algo = pk->pubkey_algo;
gcry_mpi_t *pkey = pk->pkey;
@ -435,132 +539,68 @@ pk_encrypt (PKT_public_key *pk, gcry_mpi_t data, gcry_mpi_t *resarr)
gcry_sexp_t s_pkey = NULL;
gpg_error_t err;
/* Make a sexp from pkey. */
if (algo == PUBKEY_ALGO_ELGAMAL || algo == PUBKEY_ALGO_ELGAMAL_E)
{
err = gcry_sexp_build (&s_pkey, NULL,
"(public-key(elg(p%m)(g%m)(y%m)))",
pkey[0], pkey[1], pkey[2]);
/* Put DATA into a simplified S-expression. */
if (!err)
err = gcry_sexp_build (&s_data, NULL, "%m", data);
}
else if (algo == PUBKEY_ALGO_RSA || algo == PUBKEY_ALGO_RSA_E)
{
err = gcry_sexp_build (&s_pkey, NULL,
"(public-key(rsa(n%m)(e%m)))",
pkey[0], pkey[1]);
/* Put DATA into a simplified S-expression. */
if (!err)
err = gcry_sexp_build (&s_data, NULL, "%m", data);
}
else if (algo == PUBKEY_ALGO_ECDH)
{
gcry_mpi_t k;
err = pk_ecdh_generate_ephemeral_key (pkey, &k);
if (!err)
{
char *curve;
curve = openpgp_oid_to_str (pkey[0]);
if (!curve)
err = gpg_error_from_syserror ();
else
{
int with_djb_tweak_flag = openpgp_oid_is_cv25519 (pkey[0]);
/* Now use the ephemeral secret to compute the shared point. */
err = gcry_sexp_build (&s_pkey, NULL,
with_djb_tweak_flag ?
"(public-key(ecdh(curve%s)(flags djb-tweak)(q%m)))"
: "(public-key(ecdh(curve%s)(q%m)))",
curve, pkey[1]);
xfree (curve);
/* Put K into a simplified S-expression. */
if (!err)
err = gcry_sexp_build (&s_data, NULL, "%m", k);
}
gcry_mpi_release (k);
}
}
else if (algo == PUBKEY_ALGO_KYBER)
{
log_debug ("Implement Kyber encryption\n");
err = gpg_error (GPG_ERR_NOT_IMPLEMENTED);
}
err = gcry_sexp_build (&s_pkey, NULL,
"(public-key(elg(p%m)(g%m)(y%m)))",
pkey[0], pkey[1], pkey[2]);
else
err = gpg_error (GPG_ERR_PUBKEY_ALGO);
/* Pass it to libgcrypt. */
if (!err)
err = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
gcry_sexp_release (s_data);
gcry_sexp_release (s_pkey);
err = gcry_sexp_build (&s_pkey, NULL,
"(public-key(rsa(n%m)(e%m)))",
pkey[0], pkey[1]);
if (err)
;
else if (algo == PUBKEY_ALGO_ECDH)
{
gcry_mpi_t public, result;
byte fp[MAX_FINGERPRINT_LEN];
byte *shared;
size_t nshared;
goto leave;
/* Get the shared point and the ephemeral public key. */
shared = get_data_from_sexp (s_ciph, "s", &nshared);
if (!shared)
{
err = gpg_error_from_syserror ();
goto leave;
}
err = sexp_extract_param_sos (s_ciph, "e", &public);
gcry_sexp_release (s_ciph);
s_ciph = NULL;
if (DBG_CRYPTO)
{
log_debug ("ECDH ephemeral key:");
gcry_mpi_dump (public);
log_printf ("\n");
}
err = gcry_sexp_build (&s_data, NULL, "%m", data);
if (err)
goto leave;
result = NULL;
fingerprint_from_pk (pk, fp, NULL);
err = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
if (err)
goto leave;
if (!err)
{
unsigned int nbits;
byte *p = gcry_mpi_get_opaque (data, &nbits);
err = pk_ecdh_encrypt_with_shared_point (shared, nshared, fp, p,
(nbits+7)/8, pkey, &result);
}
xfree (shared);
if (!err)
{
resarr[0] = public;
resarr[1] = result;
}
else
{
gcry_mpi_release (public);
gcry_mpi_release (result);
}
}
else /* Elgamal or RSA case. */
{ /* Fixme: Add better error handling or make gnupg use
S-expressions directly. */
resarr[0] = get_mpi_from_sexp (s_ciph, "a", GCRYMPI_FMT_USG);
if (!is_RSA (algo))
resarr[1] = get_mpi_from_sexp (s_ciph, "b", GCRYMPI_FMT_USG);
}
gcry_sexp_release (s_data); s_data = NULL;
gcry_sexp_release (s_pkey); s_pkey = NULL;
resarr[0] = get_mpi_from_sexp (s_ciph, "a", GCRYMPI_FMT_USG);
if (!is_RSA (algo))
resarr[1] = get_mpi_from_sexp (s_ciph, "b", GCRYMPI_FMT_USG);
leave:
gcry_sexp_release (s_data);
gcry_sexp_release (s_pkey);
gcry_sexp_release (s_ciph);
return err;
}
/*
* Emulate our old PK interface here - sometime in the future we might
* change the internal design to directly fit to libgcrypt. PK is is
* the OpenPGP public key packet, DATA is an MPI with the to be
* encrypted data, and RESARR receives the encrypted data. RESARRAY
* is expected to be an two item array which will be filled with newly
* allocated MPIs. SESKEY_ALGO is required for public key algorithms
* which do not encode it in DATA.
*/
gpg_error_t
pk_encrypt (PKT_public_key *pk, gcry_mpi_t data, int seskey_algo,
gcry_mpi_t *resarr)
{
pubkey_algo_t algo = pk->pubkey_algo;
if (algo == PUBKEY_ALGO_KYBER)
return do_encrypt_kem (pk, data, seskey_algo, resarr);
else if (algo == PUBKEY_ALGO_ECDH)
return do_encrypt_ecdh (pk, data, resarr);
else if (algo == PUBKEY_ALGO_ELGAMAL || algo == PUBKEY_ALGO_ELGAMAL_E)
return do_encrypt_rsa_elg (pk, data, resarr);
else if (algo == PUBKEY_ALGO_RSA || algo == PUBKEY_ALGO_RSA_E)
return do_encrypt_rsa_elg (pk, data, resarr);
else
return gpg_error (GPG_ERR_PUBKEY_ALGO);
}
/* Check whether SKEY is a suitable secret key. */
int
pk_check_secret_key (pubkey_algo_t pkalgo, gcry_mpi_t *skey)

2
g10/pkglue.h
View File

@ -31,7 +31,7 @@ gpg_error_t sexp_extract_param_sos_nlz (gcry_sexp_t sexp, const char *param,
int pk_verify (pubkey_algo_t algo, gcry_mpi_t hash, gcry_mpi_t *data,
gcry_mpi_t *pkey);
gpg_error_t pk_encrypt (PKT_public_key *pk, gcry_mpi_t data,
gpg_error_t pk_encrypt (PKT_public_key *pk, gcry_mpi_t data, int seskey_algo,
gcry_mpi_t *resarr);
int pk_check_secret_key (pubkey_algo_t algo, gcry_mpi_t *skey);