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agent: Finish ECC KEM, adding support for NIST curves.

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* agent/command.c (cmd_pkdecrypt): ECC KEM PGP doesn't use OPTION.
* agent/pkdecrypt.c (ecc_table): Add NIST curves.
(ECC_SCALAR_LEN_MAX, ECC_POINT_LEN_MAX): Fix for NIST curves.
(composite_pgp_kem_decrypt): Take care of error by gcry_cipher_setkey.
(ecc_kem_decrypt): Fix un-wrapping the session key.

--

GnuPG-bug-id: 7649
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2025-05-22 14:29:51 +09:00
parent 57a3d23925
commit b956f47e2a
No known key found for this signature in database
GPG Key ID: 640114AF89DE6054
2 changed files with 42 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
agent/command.c
View File

@ -1096,7 +1096,7 @@ cmd_pkdecrypt (assuan_context_t ctx, char *line)
if (!rc)
rc = assuan_inquire (ctx, "CIPHERTEXT",
&value, &valuelen, MAXLEN_CIPHERTEXT);
if (!rc && kemid > KEM_PQC_PGP)
if (!rc && kemid > KEM_PGP)
rc = assuan_inquire (ctx, "OPTION",
&option, &optionlen, MAXLEN_CIPHERTEXT);
if (rc)

57
agent/pkdecrypt.c
View File

@ -43,7 +43,6 @@ struct ecc_params
int scalar_reverse;
};
/* FIXME: Add NIST curves for traditional ECC */
static const struct ecc_params ecc_table[] =
{
{
@ -58,6 +57,24 @@ static const struct ecc_params ecc_table[] =
GCRY_MD_SHA3_512, GCRY_KEM_RAW_X448,
0
},
{
"NIST P-256",
65, 32, 65,
GCRY_MD_SHA3_256, GCRY_KEM_RAW_P256R1,
0
},
{
"NIST P-384",
97, 48, 97,
GCRY_MD_SHA3_512, GCRY_KEM_RAW_P384R1,
0
},
{
"NIST P-521",
133, 66, 133,
GCRY_MD_SHA3_512, GCRY_KEM_RAW_P521R1,
0
},
{
"brainpoolP256r1",
65, 32, 65,
@ -82,8 +99,8 @@ static const struct ecc_params ecc_table[] =
/* Maximum buffer sizes required for ECC KEM. Keep this aligned to
* the ecc_table above. */
#define ECC_SCALAR_LEN_MAX 64
#define ECC_POINT_LEN_MAX (1+2*64)
#define ECC_SCALAR_LEN_MAX 66
#define ECC_POINT_LEN_MAX (1+2*ECC_SCALAR_LEN_MAX)
#define ECC_HASH_LEN_MAX 64
@ -729,10 +746,10 @@ composite_pgp_kem_decrypt (ctrl_t ctrl, const char *desc_text,
}
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);
if (!err)
err = gcry_cipher_decrypt (hd, sessionkey, sessionkey_len,
encrypted_sessionkey, encrypted_sessionkey_len);
gcry_cipher_close (hd);
mpi_release (encrypted_sessionkey_mpi);
@ -770,7 +787,7 @@ composite_pgp_kem_decrypt (ctrl_t ctrl, const char *desc_text,
/* For ECC PGP KEM, decrypt CIPHERTEXT using KEM API. CIPHERTEXT
should follow the format of:
(enc-val(ecdh(c%d)(h%d)(e%m)(s%m)(fixed-info&)))
(enc-val(ecc(c%d)(h%d)(e%m)(s%m)(kdf-params&)))
c: cipher identifier (of wrapping key)
h: hash identifier
e: ECDH ciphertext
@ -808,7 +825,7 @@ ecc_kem_decrypt (ctrl_t ctrl, const char *desc_text,
gcry_cipher_hd_t hd;
unsigned char sessionkey[256];
size_t sessionkey_len;
gcry_buffer_t fixed_info = { 0, 0, 0, NULL };
gcry_buffer_t kdf_params = { 0, 0, 0, NULL };
err = agent_key_from_file (ctrl, NULL, desc_text,
NULL, &shadow_info,
@ -819,9 +836,9 @@ ecc_kem_decrypt (ctrl_t ctrl, const char *desc_text,
goto leave;
}
err = gcry_sexp_extract_param (s_cipher, NULL, "%dc%dh/es&'fixed-info'",
err = gcry_sexp_extract_param (s_cipher, NULL, "%dc%dh/es&'kdf-params'",
&algo, &hashalgo, &ecc_ct_mpi,
&encrypted_sessionkey_mpi, &fixed_info, NULL);
&encrypted_sessionkey_mpi, &kdf_params, NULL);
if (err)
{
if (opt.verbose)
@ -829,7 +846,7 @@ ecc_kem_decrypt (ctrl_t ctrl, const char *desc_text,
goto leave;
}
if (!fixed_info.data)
if (!kdf_params.data)
{
if (opt.verbose)
log_info ("%s: the KDF parameters is required\n", __func__);
@ -869,7 +886,7 @@ ecc_kem_decrypt (ctrl_t ctrl, const char *desc_text,
x-component from the point. */
ecc_ecdh + 1 : ecc_ecdh,
ecc->scalar_len, ecc_ct, ecc_point_len,
ecc_pk, ecc_point_len, &fixed_info);
ecc_pk, ecc_point_len, &kdf_params);
if (err)
{
if (opt.verbose)
@ -891,10 +908,18 @@ ecc_kem_decrypt (ctrl_t ctrl, const char *desc_text,
goto leave;
}
if (encrypted_sessionkey[0] != encrypted_sessionkey_len - 1)
{
err = gpg_error (GPG_ERR_INV_DATA);
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);
sessionkey_len = encrypted_sessionkey_len - 8 - 1;
if (!err)
err = gcry_cipher_decrypt (hd, sessionkey, sessionkey_len,
encrypted_sessionkey + 1,
encrypted_sessionkey_len - 1);
gcry_cipher_close (hd);
if (err)
@ -914,7 +939,7 @@ ecc_kem_decrypt (ctrl_t ctrl, const char *desc_text,
xfree (kek);
mpi_release (ecc_ct_mpi);
mpi_release (encrypted_sessionkey_mpi);
gcry_free (fixed_info.data);
gcry_free (kdf_params.data);
gcry_sexp_release (s_skey);
xfree (shadow_info);
return err;