static gpg_error_t
get_it (PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid)
{
gpg_error_t err;
byte *frame = NULL;
unsigned int n;
size_t nframe;
u16 csum, csum2;
int card = 0;
gcry_sexp_t s_data;
char *desc;
char *keygrip;
byte fp[MAX_FINGERPRINT_LEN];
size_t fpn;
const int pkalgo = map_pk_openpgp_to_gcry (sk->pubkey_algo);
/* Get the keygrip. */
err = hexkeygrip_from_pk (sk, &keygrip);
if (err)
goto leave;
/* Convert the data to an S-expression. */
if (pkalgo == GCRY_PK_ELG || pkalgo == GCRY_PK_ELG_E)
{
if (!enc->data[0] || !enc->data[1])
err = gpg_error (GPG_ERR_BAD_MPI);
else
err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))",
enc->data[0], enc->data[1]);
}
else if (pkalgo == GCRY_PK_RSA || pkalgo == GCRY_PK_RSA_E)
{
if (!enc->data[0])
err = gpg_error (GPG_ERR_BAD_MPI);
else
err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))",
enc->data[0]);
}
else if (pkalgo == GCRY_PK_ECDH)
{
if (!enc->data[0] || !enc->data[1])
err = gpg_error (GPG_ERR_BAD_MPI);
else
err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))",
enc->data[0], enc->data[1]);
}
else
err = gpg_error (GPG_ERR_BUG);
if (err)
goto leave;
if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
{
fingerprint_from_pk (sk, fp, &fpn);
assert (fpn == 20);
}
/* Decrypt. */
desc = gpg_format_keydesc (sk, 0, 1);
err = agent_pkdecrypt (NULL, keygrip, desc, s_data, &frame, &nframe);
xfree (desc);
gcry_sexp_release (s_data);
if (err)
goto leave;
/* Now get the DEK (data encryption key) from the frame
*
* Old versions encode the DEK in in this format (msb is left):
*
* 0 1 DEK(16 bytes) CSUM(2 bytes) 0 RND(n bytes) 2
*
* Later versions encode the DEK like this:
*
* 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes)
*
* (mpi_get_buffer already removed the leading zero).
*
* RND are non-zero randow bytes.
* A is the cipher algorithm
* DEK is the encryption key (session key) with length k
* CSUM
*/
if (DBG_CIPHER)
log_printhex ("DEK frame:", frame, nframe);
n = 0;
if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
{
gcry_mpi_t shared_mpi;
gcry_mpi_t decoded;
/* At the beginning the frame are the bytes of shared point MPI. */
err = gcry_mpi_scan (&shared_mpi, GCRYMPI_FMT_USG, frame, nframe, NULL);
if (err)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/,
shared_mpi, sk->pkey);
mpi_release (shared_mpi);
if(err)
goto leave;
/* Reuse NFRAME, which size is sufficient to include the session key. */
err = gcry_mpi_print (GCRYMPI_FMT_USG, frame, nframe, &nframe, decoded);
mpi_release (decoded);
if (err)
goto leave;
/* Now the frame are the bytes decrypted but padded session key. */
/* Allow double padding for the benefit of DEK size concealment.
Higher than this is wasteful. */
if (!nframe || frame[nframe-1] > 8*2 || nframe <= 8
|| frame[nframe-1] > nframe)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
nframe -= frame[nframe-1]; /* Remove padding. */
assert (!n); /* (used just below) */
}
else
{
if (!card)
{
if (n + 7 > nframe)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
if (frame[n] == 1 && frame[nframe - 1] == 2)
{
log_info (_("old encoding of the DEK is not supported\n"));
err = gpg_error (GPG_ERR_CIPHER_ALGO);
goto leave;
}
if (frame[n] != 2) /* Something went wrong. */
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes. */
;
n++; /* Skip the zero byte. */
}
}
if (n + 4 > nframe)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
dek->keylen = nframe - (n + 1) - 2;
dek->algo = frame[n++];
if (dek->algo == CIPHER_ALGO_IDEA)
write_status (STATUS_RSA_OR_IDEA);
err = openpgp_cipher_test_algo (dek->algo);
if (err)
{
if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO)
{
log_info (_("cipher algorithm %d%s is unknown or disabled\n"),
dek->algo,
dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : "");
if (dek->algo == CIPHER_ALGO_IDEA)
idea_cipher_warn (0);
}
dek->algo = 0;
goto leave;
}
if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo))
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
/* Copy the key to DEK and compare the checksum. */
csum = frame[nframe - 2] << 8;
csum |= frame[nframe - 1];
memcpy (dek->key, frame + n, dek->keylen);
for (csum2 = 0, n = 0; n < dek->keylen; n++)
csum2 += dek->key[n];
if (csum != csum2)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
if (DBG_CIPHER)
log_printhex ("DEK is:", dek->key, dek->keylen);
/* Check that the algo is in the preferences and whether it has expired. */
{
PKT_public_key *pk = NULL;
KBNODE pkb = get_pubkeyblock (keyid);
if (!pkb)
{
err = -1;
log_error ("oops: public key not found for preference check\n");
}
else if (pkb->pkt->pkt.public_key->selfsigversion > 3
&& dek->algo != CIPHER_ALGO_3DES
&& !opt.quiet
&& !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo))
log_info (_("WARNING: cipher algorithm %s not found in recipient"
" preferences\n"), openpgp_cipher_algo_name (dek->algo));
if (!err)
{
KBNODE k;
for (k = pkb; k; k = k->next)
{
if (k->pkt->pkttype == PKT_PUBLIC_KEY
|| k->pkt->pkttype == PKT_PUBLIC_SUBKEY)
{
u32 aki[2];
keyid_from_pk (k->pkt->pkt.public_key, aki);
if (aki[0] == keyid[0] && aki[1] == keyid[1])
{
pk = k->pkt->pkt.public_key;
break;
}
}
}
if (!pk)
BUG ();
if (pk->expiredate && pk->expiredate <= make_timestamp ())
{
log_info (_("NOTE: secret key %s expired at %s\n"),
keystr (keyid), asctimestamp (pk->expiredate));
}
}
if (pk && pk->flags.revoked)
{
log_info (_("NOTE: key has been revoked"));
log_printf ("\n");
show_revocation_reason (pk, 1);
}
release_kbnode (pkb);
err = 0;
}
leave:
xfree (frame);
xfree (keygrip);
return err;
}
static gpg_error_t
get_it (ctrl_t ctrl,
PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid)
{
gpg_error_t err;
byte *frame = NULL;
unsigned int n;
size_t nframe;
u16 csum, csum2;
int padding;
gcry_sexp_t s_data;
char *desc;
char *keygrip;
byte fp[MAX_FINGERPRINT_LEN];
size_t fpn;
if (DBG_CLOCK)
log_clock ("decryption start");
/* Get the keygrip. */
err = hexkeygrip_from_pk (sk, &keygrip);
if (err)
goto leave;
/* Convert the data to an S-expression. */
if (sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL
|| sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL_E)
{
if (!enc->data[0] || !enc->data[1])
err = gpg_error (GPG_ERR_BAD_MPI);
else
err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))",
enc->data[0], enc->data[1]);
}
else if (sk->pubkey_algo == PUBKEY_ALGO_RSA
|| sk->pubkey_algo == PUBKEY_ALGO_RSA_E)
{
if (!enc->data[0])
err = gpg_error (GPG_ERR_BAD_MPI);
else
err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))",
enc->data[0]);
}
else if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
{
if (!enc->data[0] || !enc->data[1])
err = gpg_error (GPG_ERR_BAD_MPI);
else
err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))",
enc->data[1], enc->data[0]);
}
else
err = gpg_error (GPG_ERR_BUG);
if (err)
goto leave;
if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
{
fingerprint_from_pk (sk, fp, &fpn);
log_assert (fpn == 20);
}
/* Decrypt. */
desc = gpg_format_keydesc (ctrl, sk, FORMAT_KEYDESC_NORMAL, 1);
err = agent_pkdecrypt (NULL, keygrip,
desc, sk->keyid, sk->main_keyid, sk->pubkey_algo,
s_data, &frame, &nframe, &padding);
xfree (desc);
gcry_sexp_release (s_data);
if (err)
goto leave;
/* Now get the DEK (data encryption key) from the frame
*
* Old versions encode the DEK in this format (msb is left):
*
* 0 1 DEK(16 bytes) CSUM(2 bytes) 0 RND(n bytes) 2
*
* Later versions encode the DEK like this:
*
* 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes)
*
* (mpi_get_buffer already removed the leading zero).
*
* RND are non-zero randow bytes.
* A is the cipher algorithm
* DEK is the encryption key (session key) with length k
* CSUM
*/
if (DBG_CRYPTO)
log_printhex (frame, nframe, "DEK frame:");
n = 0;
if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
{
gcry_mpi_t shared_mpi;
gcry_mpi_t decoded;
/* At the beginning the frame are the bytes of shared point MPI. */
err = gcry_mpi_scan (&shared_mpi, GCRYMPI_FMT_USG, frame, nframe, NULL);
if (err)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/,
shared_mpi, sk->pkey);
mpi_release (shared_mpi);
if(err)
goto leave;
xfree (frame);
err = gcry_mpi_aprint (GCRYMPI_FMT_USG, &frame, &nframe, decoded);
mpi_release (decoded);
if (err)
goto leave;
/* Now the frame are the bytes decrypted but padded session key. */
/* Allow double padding for the benefit of DEK size concealment.
Higher than this is wasteful. */
if (!nframe || frame[nframe-1] > 8*2 || nframe <= 8
|| frame[nframe-1] > nframe)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
nframe -= frame[nframe-1]; /* Remove padding. */
log_assert (!n); /* (used just below) */
}
else
{
if (padding)
{
if (n + 7 > nframe)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
if (frame[n] == 1 && frame[nframe - 1] == 2)
{
log_info (_("old encoding of the DEK is not supported\n"));
err = gpg_error (GPG_ERR_CIPHER_ALGO);
goto leave;
}
if (frame[n] != 2) /* Something went wrong. */
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes. */
;
n++; /* Skip the zero byte. */
}
}
if (n + 4 > nframe)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
dek->keylen = nframe - (n + 1) - 2;
dek->algo = frame[n++];
err = openpgp_cipher_test_algo (dek->algo);
if (err)
{
if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO)
{
log_info (_("cipher algorithm %d%s is unknown or disabled\n"),
dek->algo,
dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : "");
}
dek->algo = 0;
goto leave;
}
if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo))
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
/* Copy the key to DEK and compare the checksum. */
csum = buf16_to_u16 (frame+nframe-2);
memcpy (dek->key, frame + n, dek->keylen);
for (csum2 = 0, n = 0; n < dek->keylen; n++)
csum2 += dek->key[n];
if (csum != csum2)
{
err = gpg_error (GPG_ERR_WRONG_SECKEY);
goto leave;
}
if (DBG_CLOCK)
log_clock ("decryption ready");
if (DBG_CRYPTO)
log_printhex (dek->key, dek->keylen, "DEK is:");
/* Check that the algo is in the preferences and whether it has
* expired. Also print a status line with the key's fingerprint. */
{
PKT_public_key *pk = NULL;
PKT_public_key *mainpk = NULL;
KBNODE pkb = get_pubkeyblock (ctrl, keyid);
if (!pkb)
{
err = -1;
log_error ("oops: public key not found for preference check\n");
}
else if (pkb->pkt->pkt.public_key->selfsigversion > 3
&& dek->algo != CIPHER_ALGO_3DES
&& !opt.quiet
&& !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo))
log_info (_("WARNING: cipher algorithm %s not found in recipient"
" preferences\n"), openpgp_cipher_algo_name (dek->algo));
if (!err)
{
kbnode_t k;
int first = 1;
for (k = pkb; k; k = k->next)
{
if (k->pkt->pkttype == PKT_PUBLIC_KEY
|| k->pkt->pkttype == PKT_PUBLIC_SUBKEY)
{
u32 aki[2];
if (first)
{
first = 0;
mainpk = k->pkt->pkt.public_key;
}
keyid_from_pk (k->pkt->pkt.public_key, aki);
if (aki[0] == keyid[0] && aki[1] == keyid[1])
{
pk = k->pkt->pkt.public_key;
break;
}
}
}
if (!pk)
BUG ();
if (pk->expiredate && pk->expiredate <= make_timestamp ())
{
log_info (_("Note: secret key %s expired at %s\n"),
keystr (keyid), asctimestamp (pk->expiredate));
}
}
if (pk && pk->flags.revoked)
{
log_info (_("Note: key has been revoked"));
log_printf ("\n");
show_revocation_reason (ctrl, pk, 1);
}
if (is_status_enabled () && pk && mainpk)
{
char pkhex[MAX_FINGERPRINT_LEN*2+1];
char mainpkhex[MAX_FINGERPRINT_LEN*2+1];
hexfingerprint (pk, pkhex, sizeof pkhex);
hexfingerprint (mainpk, mainpkhex, sizeof mainpkhex);
/* Note that we do not want to create a trustdb just for
* getting the ownertrust: If there is no trustdb there can't
* be ulitmately trusted key anyway and thus the ownertrust
* value is irrelevant. */
write_status_printf (STATUS_DECRYPTION_KEY, "%s %s %c",
pkhex, mainpkhex,
get_ownertrust_info (ctrl, mainpk, 1));
}
release_kbnode (pkb);
err = 0;
}
leave:
xfree (frame);
xfree (keygrip);
return err;
}
