/* pubkey-enc.c - Process a public key encoded packet.
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2006, 2009,
* 2010 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 .
*/
#include
#include
#include
#include
#include
#include "gpg.h"
#include "util.h"
#include "packet.h"
#include "keydb.h"
#include "trustdb.h"
#include "cipher.h"
#include "status.h"
#include "options.h"
#include "main.h"
#include "i18n.h"
#include "pkglue.h"
#include "call-agent.h"
static gpg_error_t get_it (PKT_pubkey_enc *k,
DEK *dek, PKT_public_key *sk, u32 *keyid);
/* Check that the given algo is mentioned in one of the valid user-ids. */
static int
is_algo_in_prefs (kbnode_t keyblock, preftype_t type, int algo)
{
kbnode_t k;
for (k = keyblock; k; k = k->next)
{
if (k->pkt->pkttype == PKT_USER_ID)
{
PKT_user_id *uid = k->pkt->pkt.user_id;
prefitem_t *prefs = uid->prefs;
if (uid->created && prefs && !uid->is_revoked && !uid->is_expired)
{
for (; prefs->type; prefs++)
if (prefs->type == type && prefs->value == algo)
return 1;
}
}
}
return 0;
}
/*
* Get the session key from a pubkey enc packet and return it in DEK,
* which should have been allocated in secure memory by the caller.
*/
gpg_error_t
get_session_key (PKT_pubkey_enc * k, DEK * dek)
{
PKT_public_key *sk = NULL;
int rc;
rc = openpgp_pk_test_algo2 (k->pubkey_algo, PUBKEY_USAGE_ENC);
if (rc)
goto leave;
if ((k->keyid[0] || k->keyid[1]) && !opt.try_all_secrets)
{
sk = xmalloc_clear (sizeof *sk);
sk->pubkey_algo = k->pubkey_algo; /* We want a pubkey with this algo. */
if (!(rc = get_seckey (sk, k->keyid)))
rc = get_it (k, dek, sk, k->keyid);
}
else if (opt.skip_hidden_recipients)
rc = gpg_error (GPG_ERR_NO_SECKEY);
else /* Anonymous receiver: Try all available secret keys. */
{
void *enum_context = NULL;
u32 keyid[2];
for (;;)
{
if (sk)
free_public_key (sk);
sk = xmalloc_clear (sizeof *sk);
rc = enum_secret_keys (&enum_context, sk);
if (rc)
{
rc = G10ERR_NO_SECKEY;
break;
}
if (sk->pubkey_algo != k->pubkey_algo)
continue;
if (!(sk->pubkey_usage & PUBKEY_USAGE_ENC))
continue;
keyid_from_pk (sk, keyid);
log_info (_("anonymous recipient; trying secret key %s ...\n"),
keystr (keyid));
rc = get_it (k, dek, sk, keyid);
if (!rc)
{
log_info (_("okay, we are the anonymous recipient.\n"));
break;
}
else if (gpg_err_code (rc) == GPG_ERR_FULLY_CANCELED)
break; /* Don't try any more secret keys. */
}
enum_secret_keys (&enum_context, NULL); /* free context */
}
leave:
if (sk)
free_public_key (sk);
return rc;
}
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;
/* Get the keygrip. */
err = hexkeygrip_from_pk (sk, &keygrip);
if (err)
goto leave;
/* Convert the data to an S-expression. */
if (sk->pubkey_algo == GCRY_PK_ELG || sk->pubkey_algo == 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 (sk->pubkey_algo == GCRY_PK_RSA || sk->pubkey_algo == 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
err = gpg_error (GPG_ERR_BUG);
if (err)
goto leave;
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, fp, &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 ) {
if (!card)
{
if (n + 7 > nframe)
{
err = gpg_error (G10ERR_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 (G10ERR_CIPHER_ALGO);
goto leave;
}
if (frame[n] != 2) /* Something went wrong. */
{
err = gpg_error (G10ERR_WRONG_SECKEY);
goto leave;
}
for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes. */
;
n++; /* Skip the zero byte. */
}
}
else {
/* Allow double padding for the benefit of DEK size concealment.
* Higher than this is wasteful.
*/
if( frame[nframe-1] > 8*2 || nframe <= 8 ) {
err = G10ERR_WRONG_SECKEY; goto leave;
}
nframe -= frame[nframe-1]; /* remove padding */
assert( n==0 ); /* used just bellow */
}
if (n + 4 > nframe)
{
err = gpg_error (G10ERR_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;
}
/*
* Get the session key from the given string.
* String is supposed to be formatted as this:
* :
*/
gpg_error_t
get_override_session_key (DEK *dek, const char *string)
{
const char *s;
int i;
if (!string)
return G10ERR_BAD_KEY;
dek->algo = atoi (string);
if (dek->algo < 1)
return G10ERR_BAD_KEY;
if (!(s = strchr (string, ':')))
return G10ERR_BAD_KEY;
s++;
for (i = 0; i < DIM (dek->key) && *s; i++, s += 2)
{
int c = hextobyte (s);
if (c == -1)
return G10ERR_BAD_KEY;
dek->key[i] = c;
}
if (*s)
return G10ERR_BAD_KEY;
dek->keylen = i;
return 0;
}