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diff --git a/agent/pkdecrypt.c b/agent/pkdecrypt.c
index 24ba1fd64..8f1614292 100644
--- a/agent/pkdecrypt.c
+++ b/agent/pkdecrypt.c
@@ -1,497 +1,478 @@
/* pkdecrypt.c - public key decryption (well, actually using a secret key)
* Copyright (C) 2001, 2003 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* GnuPG is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <sys/stat.h>
#include "agent.h"
#include "../common/openpgpdefs.h"
/* DECRYPT the stuff in ciphertext which is expected to be a S-Exp.
Try to get the key from CTRL and write the decoded stuff back to
OUTFP. The padding information is stored at R_PADDING with -1
for not known. */
gpg_error_t
agent_pkdecrypt (ctrl_t ctrl, const char *desc_text,
const unsigned char *ciphertext, size_t ciphertextlen,
membuf_t *outbuf, int *r_padding)
{
gcry_sexp_t s_skey = NULL, s_cipher = NULL, s_plain = NULL;
unsigned char *shadow_info = NULL;
gpg_error_t err = 0;
int no_shadow_info = 0;
char *buf = NULL;
size_t len;
*r_padding = -1;
if (!ctrl->have_keygrip)
{
log_error ("speculative decryption not yet supported\n");
err = gpg_error (GPG_ERR_NO_SECKEY);
goto leave;
}
err = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
if (err)
{
log_error ("failed to convert ciphertext: %s\n", gpg_strerror (err));
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
if (DBG_CRYPTO)
{
log_printhex (ctrl->keygrip, 20, "keygrip:");
log_printhex (ciphertext, ciphertextlen, "cipher: ");
}
err = agent_key_from_file (ctrl, NULL, desc_text,
NULL, &shadow_info,
CACHE_MODE_NORMAL, NULL, &s_skey, NULL, NULL);
if (gpg_err_code (err) == GPG_ERR_NO_SECKEY)
no_shadow_info = 1;
else if (err)
{
log_error ("failed to read the secret key\n");
goto leave;
}
if (shadow_info || no_shadow_info)
{ /* divert operation to the smartcard */
if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
{
err = gpg_error (GPG_ERR_INV_SEXP);
goto leave;
}
if (s_skey && agent_is_tpm2_key (s_skey))
err = divert_tpm2_pkdecrypt (ctrl, ciphertext, shadow_info,
&buf, &len, r_padding);
else
err = divert_pkdecrypt (ctrl, ctrl->keygrip, ciphertext,
&buf, &len, r_padding);
if (err)
{
/* We restore the original error (ie. no seckey) is no card
* has been found and we have no shadow key. This avoids a
* surprising "card removed" error code. */
if ((gpg_err_code (err) == GPG_ERR_CARD_REMOVED
|| gpg_err_code (err) == GPG_ERR_CARD_NOT_PRESENT)
&& no_shadow_info)
err = gpg_error (GPG_ERR_NO_SECKEY);
else
log_error ("smartcard decryption failed: %s\n", gpg_strerror (err));
goto leave;
}
put_membuf_printf (outbuf, "(5:value%u:", (unsigned int)len);
put_membuf (outbuf, buf, len);
put_membuf (outbuf, ")", 2);
}
else
{ /* No smartcard, but a private key */
/* if (DBG_CRYPTO ) */
/* { */
/* log_debug ("skey: "); */
/* gcry_sexp_dump (s_skey); */
/* } */
err = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
if (err)
{
log_error ("decryption failed: %s\n", gpg_strerror (err));
goto leave;
}
if (DBG_CRYPTO)
{
log_debug ("plain: ");
gcry_sexp_dump (s_plain);
}
len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
log_assert (len);
buf = xmalloc (len);
len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
log_assert (len);
if (*buf == '(')
put_membuf (outbuf, buf, len);
else
{
/* Old style libgcrypt: This is only an S-expression
part. Turn it into a complete S-expression. */
put_membuf (outbuf, "(5:value", 8);
put_membuf (outbuf, buf, len);
put_membuf (outbuf, ")", 2);
}
}
leave:
gcry_sexp_release (s_skey);
gcry_sexp_release (s_plain);
gcry_sexp_release (s_cipher);
xfree (buf);
xfree (shadow_info);
return err;
}
/* Reverse BUFFER to change the endianness. */
static void
reverse_buffer (unsigned char *buffer, unsigned int length)
{
unsigned int tmp, i;
for (i=0; i < length/2; i++)
{
tmp = buffer[i];
buffer[i] = buffer[length-1-i];
buffer[length-1-i] = tmp;
}
}
/* For hybrid PGP KEM (ECC+ML-KEM), decrypt CIPHERTEXT using KEM API.
First keygrip is for ECC, second keygrip is for PQC. CIPHERTEXT
should follow the format of:
- (enc-val(pqc(e%m)(k%m)(s%m)(fixed-info&)))
+ (enc-val(pqc(c%u)(e%m)(k%m)(s%m)(fixed-info&)))
+ c: cipher identifier (symmetric)
e: ECDH ciphertext
k: ML-KEM ciphertext
s: encrypted session key
fixed-info: A buffer with the fixed info.
FIXME: For now, possible keys on smartcard are not supported.
*/
static gpg_error_t
agent_hybrid_pgp_kem_decrypt (ctrl_t ctrl, const char *desc_text,
gcry_sexp_t s_cipher, membuf_t *outbuf)
{
#if GCRYPT_VERSION_NUMBER >= 0x010b00
gcry_sexp_t s_skey0 = NULL;
gcry_sexp_t s_skey1 = NULL;
unsigned char *shadow_info = NULL;
gpg_error_t err = 0;
unsigned int nbits;
const unsigned char *p;
size_t len;
+ int algo;
gcry_mpi_t encrypted_sessionkey_mpi = NULL;
const unsigned char *encrypted_sessionkey;
size_t encrypted_sessionkey_len;
gcry_mpi_t ecc_sk_mpi = NULL;
unsigned char ecc_sk[32];
gcry_mpi_t ecc_pk_mpi = NULL;
unsigned char ecc_pk[32];
gcry_mpi_t ecc_ct_mpi = NULL;
const unsigned char *ecc_ct;
size_t ecc_ct_len;
unsigned char ecc_ecdh[32];
unsigned char ecc_ss[32];
gcry_mpi_t mlkem_sk_mpi = NULL;
gcry_mpi_t mlkem_ct_mpi = NULL;
const unsigned char *mlkem_sk;
const unsigned char *mlkem_ct;
unsigned char mlkem_ss[GCRY_KEM_MLKEM768_SHARED_LEN];
unsigned char kek[32];
size_t kek_len = 32; /* AES-256 is mandatory */
gcry_cipher_hd_t hd;
unsigned char sessionkey[256];
size_t sessionkey_len;
gcry_buffer_t fixed_info = { 0, 0, 0, NULL };
gcry_sexp_t curve = NULL;
const char *curve_name;
err = agent_key_from_file (ctrl, NULL, desc_text,
ctrl->keygrip, &shadow_info,
CACHE_MODE_NORMAL, NULL, &s_skey0, NULL, NULL);
if (err)
{
log_error ("failed to read the secret key\n");
goto leave;
}
err = agent_key_from_file (ctrl, NULL, desc_text,
ctrl->keygrip1, &shadow_info,
CACHE_MODE_NORMAL, NULL, &s_skey1, NULL, NULL);
if (err)
{
log_error ("failed to read the another secret key\n");
goto leave;
}
/* Here assumes no smartcard, but private keys */
- gcry_sexp_extract_param (s_cipher, NULL, "/eks&'fixed-info'",
- &ecc_ct_mpi,
- &mlkem_ct_mpi,
- &encrypted_sessionkey_mpi,
- &fixed_info, NULL);
+ gcry_sexp_extract_param (s_cipher, NULL, "%uc/eks&'fixed-info'",
+ &algo, &ecc_ct_mpi, &mlkem_ct_mpi,
+ &encrypted_sessionkey_mpi, &fixed_info, NULL);
if (err)
goto leave;
+ len = gcry_cipher_get_algo_keylen (algo);
encrypted_sessionkey = gcry_mpi_get_opaque (encrypted_sessionkey_mpi, &nbits);
encrypted_sessionkey_len = (nbits+7)/8;
- if (encrypted_sessionkey_len < 1+1+8)
+ if (len == 0 || encrypted_sessionkey_len != len + 8)
{
- /* Fixme: This is a basic check but we should better test
- * against the expected length and something which
- * is required to avoid an underflow. */
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
- encrypted_sessionkey_len--;
- if (encrypted_sessionkey[0] != encrypted_sessionkey_len)
- {
- err = gpg_error (GPG_ERR_INV_DATA);
- goto leave;
- }
- encrypted_sessionkey++; /* Skip the length. */
-
- if (encrypted_sessionkey[0] != CIPHER_ALGO_AES256)
- {
- err = gpg_error (GPG_ERR_INV_DATA);
- goto leave;
- }
-
- encrypted_sessionkey_len--;
- encrypted_sessionkey++; /* Skip the sym algo */
-
/* Fistly, ECC part. FIXME: For now, we assume X25519. */
curve = gcry_sexp_find_token (s_skey0, "curve", 0);
if (!curve)
{
err = gpg_error (GPG_ERR_BAD_SECKEY);
goto leave;
}
curve_name = gcry_sexp_nth_data (curve, 1, &len);
if (len != 10 || memcmp (curve_name, "Curve25519", len))
{
err = gpg_error (GPG_ERR_BAD_SECKEY);
goto leave;
}
- err = gcry_sexp_extract_param (s_skey0, NULL, "/q/d",
+ err = gcry_sexp_extract_param (s_skey0, NULL, "/qd",
&ecc_pk_mpi, &ecc_sk_mpi, NULL);
if (err)
goto leave;
p = gcry_mpi_get_opaque (ecc_pk_mpi, &nbits);
len = (nbits+7)/8;
memcpy (ecc_pk, p+1, 32); /* Remove the 0x40 prefix */
p = gcry_mpi_get_opaque (ecc_sk_mpi, &nbits);
len = (nbits+7)/8;
if (len > 32)
{
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
memset (ecc_sk, 0, 32);
memcpy (ecc_sk + 32 - len, p, len);
reverse_buffer (ecc_sk, 32);
mpi_release (ecc_pk_mpi);
mpi_release (ecc_sk_mpi);
ecc_pk_mpi = NULL;
ecc_sk_mpi = NULL;
ecc_ct = gcry_mpi_get_opaque (ecc_ct_mpi, &nbits);
ecc_ct_len = (nbits+7)/8;
if (ecc_ct_len != 32)
{
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
err = gcry_kem_decap (GCRY_KEM_RAW_X25519, ecc_sk, 32, ecc_ct, ecc_ct_len,
ecc_ecdh, 32, NULL, 0);
if (err)
goto leave;
err = gnupg_ecc_kem_kdf (ecc_ss, 32, GCRY_MD_SHA3_256,
ecc_ecdh, 32, ecc_ct, 32, ecc_pk, 32);
if (err)
goto leave;
/* Secondly, PQC part. For now, we assume ML-KEM. */
gcry_sexp_extract_param (s_skey1, NULL, "/s", &mlkem_sk_mpi, NULL);
mlkem_sk = gcry_mpi_get_opaque (mlkem_sk_mpi, &nbits);
len = (nbits+7)/8;
if (len != GCRY_KEM_MLKEM768_SECKEY_LEN)
{
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
mlkem_ct = gcry_mpi_get_opaque (mlkem_ct_mpi, &nbits);
len = (nbits+7)/8;
if (len != GCRY_KEM_MLKEM768_CIPHER_LEN)
{
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
err = gcry_kem_decap (GCRY_KEM_MLKEM768,
mlkem_sk, GCRY_KEM_MLKEM768_SECKEY_LEN,
mlkem_ct, GCRY_KEM_MLKEM768_CIPHER_LEN,
mlkem_ss, GCRY_KEM_MLKEM768_SHARED_LEN,
NULL, 0);
if (err)
goto leave;
mpi_release (mlkem_sk_mpi);
mlkem_sk_mpi = NULL;
/* Then, combine two shared secrets and ciphertexts into one KEK */
err = gnupg_kem_combiner (kek, kek_len,
ecc_ss, 32, ecc_ct, 32,
mlkem_ss, GCRY_KEM_MLKEM768_SHARED_LEN,
mlkem_ct, GCRY_KEM_MLKEM768_CIPHER_LEN,
fixed_info.data, fixed_info.size);
if (err)
{
log_error ("KEM combiner failed: %s\n", gpg_strerror (err));
goto leave;
}
mpi_release (ecc_ct_mpi);
mpi_release (mlkem_ct_mpi);
ecc_ct_mpi = NULL;
mlkem_ct_mpi = NULL;
if (DBG_CRYPTO)
{
log_printhex (kek, kek_len, "KEK key: ");
}
err = gcry_cipher_open (&hd, GCRY_CIPHER_AES256,
GCRY_CIPHER_MODE_AESWRAP, 0);
if (err)
{
log_error ("ecdh failed to initialize AESWRAP: %s\n",
gpg_strerror (err));
goto leave;
}
err = gcry_cipher_setkey (hd, kek, kek_len);
sessionkey_len = encrypted_sessionkey_len - 8;
err = gcry_cipher_decrypt (hd, sessionkey, sessionkey_len,
encrypted_sessionkey, encrypted_sessionkey_len);
gcry_cipher_close (hd);
mpi_release (encrypted_sessionkey_mpi);
encrypted_sessionkey_mpi = NULL;
if (err)
{
log_error ("KEM decrypt failed: %s\n", gpg_strerror (err));
goto leave;
}
put_membuf_printf (outbuf,
"(5:value%u:", (unsigned int)sessionkey_len);
put_membuf (outbuf, sessionkey, sessionkey_len);
put_membuf (outbuf, ")", 2);
leave:
mpi_release (mlkem_sk_mpi);
mpi_release (ecc_pk_mpi);
mpi_release (ecc_sk_mpi);
mpi_release (ecc_ct_mpi);
mpi_release (mlkem_ct_mpi);
mpi_release (encrypted_sessionkey_mpi);
gcry_free (fixed_info.data);
gcry_sexp_release (curve);
gcry_sexp_release (s_skey0);
gcry_sexp_release (s_skey1);
return err;
#else
return gpg_error (GPG_ERR_NOT_IMPLEMENTED);
#endif
}
/* DECRYPT the encrypted stuff (like encrypted session key) in
CIPHERTEXT using KEM API, with KEMID. Keys (or a key) are
specified in CTRL. DESC_TEXT is used to retrieve private key.
OPTION can be specified for upper layer option for KEM. Decrypted
stuff (like session key) is written to OUTBUF.
*/
gpg_error_t
agent_kem_decrypt (ctrl_t ctrl, const char *desc_text, int kemid,
const unsigned char *ciphertext, size_t ciphertextlen,
const unsigned char *option, size_t optionlen,
membuf_t *outbuf)
{
gcry_sexp_t s_cipher = NULL;
gpg_error_t err = 0;
/* For now, only PQC-PGP is supported. */
if (kemid != KEM_PQC_PGP)
return gpg_error (GPG_ERR_UNSUPPORTED_ALGORITHM);
(void)optionlen;
if (kemid == KEM_PQC_PGP && option)
{
log_error ("PQC-PGP requires no option\n");
return gpg_error (GPG_ERR_INV_ARG);
}
if (!ctrl->have_keygrip)
{
log_error ("speculative decryption not yet supported\n");
return gpg_error (GPG_ERR_NO_SECKEY);
}
if (!ctrl->have_keygrip1)
{
log_error ("hybrid KEM requires two KEYGRIPs\n");
return gpg_error (GPG_ERR_NO_SECKEY);
}
err = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
if (err)
{
log_error ("failed to convert ciphertext: %s\n", gpg_strerror (err));
return gpg_error (GPG_ERR_INV_DATA);
}
if (DBG_CRYPTO)
{
log_printhex (ctrl->keygrip, 20, "keygrip:");
log_printhex (ctrl->keygrip1, 20, "keygrip1:");
log_printhex (ciphertext, ciphertextlen, "cipher: ");
}
err = agent_hybrid_pgp_kem_decrypt (ctrl, desc_text, s_cipher, outbuf);
gcry_sexp_release (s_cipher);
return err;
}

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