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agent: Fix PQC decryption. 

* agent/pkdecrypt.c (agent_hybrid_pgp_kem_decrypt): Change the format
of SEXP in the protocol for symmetric cipher algorithm identifier.

--

GnuPG-bug-id: 7014
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2024-04-11 15:21:42 +09:00
parent 6737e07a9b
commit 172d53d636
No known key found for this signature in database
GPG Key ID: 640114AF89DE6054
1 changed files with 9 additions and 28 deletions
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37
agent/pkdecrypt.c
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@ -177,7 +177,8 @@ reverse_buffer (unsigned char *buffer, unsigned int length)
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
@ -199,6 +200,7 @@ agent_hybrid_pgp_kem_decrypt (ctrl_t ctrl, const char *desc_text,
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;
@ -250,41 +252,20 @@ agent_hybrid_pgp_kem_decrypt (ctrl_t ctrl, const char *desc_text,
/* 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)
{
/* 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)
if (len == 0 || encrypted_sessionkey_len != len + 8)
{
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);
@ -301,7 +282,7 @@ agent_hybrid_pgp_kem_decrypt (ctrl_t ctrl, const char *desc_text,
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;