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|
/* pubkey.c - Public key API
* Copyright (C) 2002, 2003, 2007, 2008, 2009, 2010 Free Software
* Foundation, Inc.
*
* Author: Timo Schulz
*
* This file is part of OpenCDK.
*
* The OpenCDK library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <gnutls_int.h>
#include <gnutls_datum.h>
#include "opencdk.h"
#include "main.h"
#include "packet.h"
/* This function gets the signature parameters and encodes
* them into a way for _gnutls_pk_verify to use.
*/
static cdk_error_t
sig_to_datum (gnutls_datum_t * r_sig, cdk_pkt_signature_t sig)
{
int err;
cdk_error_t rc;
if (!r_sig || !sig)
return CDK_Inv_Value;
rc = 0;
if (is_RSA (sig->pubkey_algo))
{
err = _gnutls_mpi_dprint (sig->mpi[0], r_sig);
if (err < 0)
rc = map_gnutls_error (err);
}
else if (is_DSA (sig->pubkey_algo))
{
err = _gnutls_encode_ber_rs (r_sig, sig->mpi[0], sig->mpi[1]);
if (err < 0)
rc = map_gnutls_error (err);
}
else
rc = CDK_Inv_Algo;
return rc;
}
/**
* cdk_pk_verify:
* @pk: the public key
* @sig: signature
* @md: the message digest
*
* Verify the signature in @sig and compare it with the message digest in @md.
**/
cdk_error_t
cdk_pk_verify (cdk_pubkey_t pk, cdk_pkt_signature_t sig, const byte * md)
{
gnutls_datum_t s_sig;
byte *encmd = NULL;
size_t enclen;
cdk_error_t rc;
int ret, algo;
unsigned int i;
gnutls_datum_t data;
gnutls_pk_params_st params;
if (!pk || !sig || !md)
{
gnutls_assert ();
return CDK_Inv_Value;
}
if (is_DSA (pk->pubkey_algo))
algo = GNUTLS_PK_DSA;
else if (is_RSA (pk->pubkey_algo))
algo = GNUTLS_PK_RSA;
else
{
gnutls_assert ();
return CDK_Inv_Value;
}
rc = sig_to_datum (&s_sig, sig);
if (rc)
{
gnutls_assert ();
goto leave;
}
rc = _cdk_digest_encode_pkcs1 (&encmd, &enclen, pk->pubkey_algo, md,
sig->digest_algo, cdk_pk_get_nbits (pk));
if (rc)
{
gnutls_assert ();
goto leave;
}
data.data = encmd;
data.size = enclen;
params.params_nr = cdk_pk_get_npkey (pk->pubkey_algo);
for (i = 0; i < params.params_nr; i++)
params.params[i] = pk->mpi[i];
params.flags = 0;
ret = _gnutls_pk_verify (algo, &data, &s_sig, ¶ms);
if (ret < 0)
{
gnutls_assert ();
rc = map_gnutls_error (ret);
goto leave;
}
rc = 0;
leave:
_gnutls_free_datum (&s_sig);
cdk_free (encmd);
return rc;
}
/**
* cdk_pk_get_nbits:
* @pk: the public key
*
* Return the length of the public key in bits.
* The meaning of length is actually the size of the 'prime'
* object in the key. For RSA keys the modulus, for ElG/DSA
* the size of the public prime.
**/
int
cdk_pk_get_nbits (cdk_pubkey_t pk)
{
if (!pk || !pk->mpi[0])
return 0;
return _gnutls_mpi_get_nbits (pk->mpi[0]);
}
/**
* cdk_pk_get_npkey:
* @algo: The public key algorithm.
*
* Return the number of multiprecison integer forming an public
* key with the given algorithm.
*/
int
cdk_pk_get_npkey (int algo)
{
if (is_RSA (algo))
return RSA_PUBLIC_PARAMS;
else if (is_DSA (algo))
return DSA_PUBLIC_PARAMS;
else if (is_ELG (algo))
return 3;
else
{
gnutls_assert ();
return 0;
}
}
/**
* cdk_pk_get_nskey:
* @algo: the public key algorithm
*
* Return the number of multiprecision integers forming an
* secret key with the given algorithm.
**/
int
cdk_pk_get_nskey (int algo)
{
int ret;
if (is_RSA (algo))
ret = RSA_PRIVATE_PARAMS;
else if (is_DSA (algo))
ret = DSA_PRIVATE_PARAMS;
else if (is_ELG (algo))
ret = 4;
else
{
gnutls_assert ();
return 0;
}
ret -= cdk_pk_get_npkey (algo);
return ret;
}
/**
* cdk_pk_get_nbits:
* @algo: the public key algorithm
*
* Return the number of MPIs a signature consists of.
**/
int
cdk_pk_get_nsig (int algo)
{
if (is_RSA (algo))
return 1;
else if (is_DSA (algo))
return 2;
else
return 0;
}
/**
* cdk_pk_get_nenc:
* @algo: the public key algorithm
*
* Return the number of MPI's the encrypted data consists of.
**/
int
cdk_pk_get_nenc (int algo)
{
if (is_RSA (algo))
return 1;
else if (is_ELG (algo))
return 2;
else
return 0;
}
int
_cdk_pk_algo_usage (int algo)
{
int usage;
/* The ElGamal sign+encrypt algorithm is not supported any longer. */
switch (algo)
{
case CDK_PK_RSA:
usage = CDK_KEY_USG_SIGN | CDK_KEY_USG_ENCR;
break;
case CDK_PK_RSA_E:
usage = CDK_KEY_USG_ENCR;
break;
case CDK_PK_RSA_S:
usage = CDK_KEY_USG_SIGN;
break;
case CDK_PK_ELG_E:
usage = CDK_KEY_USG_ENCR;
break;
case CDK_PK_DSA:
usage = CDK_KEY_USG_SIGN;
break;
default:
usage = 0;
}
return usage;
}
/* You can use a NULL buf to get the output size only
*/
static cdk_error_t
mpi_to_buffer (bigint_t a, byte * buf, size_t buflen,
size_t * r_nwritten, size_t * r_nbits)
{
size_t nbits;
int err;
if (!a || !r_nwritten)
{
gnutls_assert ();
return CDK_Inv_Value;
}
nbits = _gnutls_mpi_get_nbits (a);
if (r_nbits)
*r_nbits = nbits;
if (r_nwritten)
*r_nwritten = (nbits + 7) / 8 + 2;
if ((nbits + 7) / 8 + 2 > buflen)
return CDK_Too_Short;
*r_nwritten = buflen;
err = _gnutls_mpi_print (a, buf, r_nwritten);
if (err < 0)
{
gnutls_assert ();
return map_gnutls_error (err);
}
return 0;
}
/**
* cdk_pk_get_mpi:
* @pk: public key
* @idx: index of the MPI to retrieve
* @buf: buffer to hold the raw data
* @r_nwritten: output how large the raw data is
* @r_nbits: size of the MPI in bits.
*
* Return the MPI with the given index of the public key.
**/
cdk_error_t
cdk_pk_get_mpi (cdk_pubkey_t pk, size_t idx,
byte * buf, size_t buflen, size_t * r_nwritten,
size_t * r_nbits)
{
if (!pk || !r_nwritten)
return CDK_Inv_Value;
if ((ssize_t) idx > cdk_pk_get_npkey (pk->pubkey_algo))
return CDK_Inv_Value;
return mpi_to_buffer (pk->mpi[idx], buf, buflen, r_nwritten, r_nbits);
}
/**
* cdk_sk_get_mpi:
* @sk: secret key
* @idx: index of the MPI to retrieve
* @buf: buffer to hold the raw data
* @r_nwritten: output length of the raw data
* @r_nbits: length of the MPI data in bits.
*
* Return the MPI of the given secret key with the
* index @idx. It is important to check if the key
* is protected and thus no real MPI data will be returned then.
**/
cdk_error_t
cdk_sk_get_mpi (cdk_pkt_seckey_t sk, size_t idx,
byte * buf, size_t buflen, size_t * r_nwritten,
size_t * r_nbits)
{
if (!sk || !r_nwritten)
return CDK_Inv_Value;
if ((ssize_t) idx > cdk_pk_get_nskey (sk->pubkey_algo))
return CDK_Inv_Value;
return mpi_to_buffer (sk->mpi[idx], buf, buflen, r_nwritten, r_nbits);
}
static u16
checksum_mpi (bigint_t m)
{
byte buf[MAX_MPI_BYTES + 2];
size_t nread;
unsigned int i;
u16 chksum = 0;
if (!m)
return 0;
nread = DIM (buf);
if (_gnutls_mpi_print_pgp (m, buf, &nread) < 0)
return 0;
for (i = 0; i < nread; i++)
chksum += buf[i];
return chksum;
}
/**
* cdk_pk_from_secret_key:
* @sk: the secret key
* @ret_pk: the new public key
*
* Create a new public key from a secret key.
**/
cdk_error_t
cdk_pk_from_secret_key (cdk_pkt_seckey_t sk, cdk_pubkey_t * ret_pk)
{
if (!sk)
return CDK_Inv_Value;
return _cdk_copy_pubkey (ret_pk, sk->pk);
}
int
_cdk_sk_get_csum (cdk_pkt_seckey_t sk)
{
u16 csum = 0, i;
if (!sk)
return 0;
for (i = 0; i < cdk_pk_get_nskey (sk->pubkey_algo); i++)
csum += checksum_mpi (sk->mpi[i]);
return csum;
}
/**
* cdk_pk_get_fingerprint:
* @pk: the public key
* @fpr: the buffer to hold the fingerprint
*
* Return the fingerprint of the given public key.
* The buffer must be at least 20 octets.
* This function should be considered deprecated and
* the new cdk_pk_to_fingerprint() should be used whenever
* possible to avoid overflows.
**/
cdk_error_t
cdk_pk_get_fingerprint (cdk_pubkey_t pk, byte * fpr)
{
digest_hd_st hd;
int md_algo;
int dlen = 0;
int err;
if (!pk || !fpr)
return CDK_Inv_Value;
if (pk->version < 4 && is_RSA (pk->pubkey_algo))
md_algo = GNUTLS_DIG_MD5; /* special */
else
md_algo = GNUTLS_DIG_SHA1;
dlen = _gnutls_hash_get_algo_len (md_algo);
err = _gnutls_hash_init (&hd, md_algo);
if (err < 0)
return map_gnutls_error (err);
_cdk_hash_pubkey (pk, &hd, 1);
_gnutls_hash_deinit (&hd, fpr);
if (dlen == 16)
memset (fpr + 16, 0, 4);
return 0;
}
/**
* cdk_pk_to_fingerprint:
* @pk: the public key
* @fprbuf: buffer to save the fingerprint
* @fprbuflen: buffer size
* @r_nout: actual length of the fingerprint.
*
* Calculate a fingerprint of the given key and
* return it in the given byte array.
**/
cdk_error_t
cdk_pk_to_fingerprint (cdk_pubkey_t pk,
byte * fprbuf, size_t fprbuflen, size_t * r_nout)
{
size_t key_fprlen;
cdk_error_t err;
if (!pk)
return CDK_Inv_Value;
if (pk->version < 4)
key_fprlen = 16;
else
key_fprlen = 20;
/* Only return the required buffer size for the fingerprint. */
if (!fprbuf && !fprbuflen && r_nout)
{
*r_nout = key_fprlen;
return 0;
}
if (!fprbuf || key_fprlen > fprbuflen)
return CDK_Too_Short;
err = cdk_pk_get_fingerprint (pk, fprbuf);
if (r_nout)
*r_nout = key_fprlen;
return err;
}
/**
* cdk_pk_fingerprint_get_keyid:
* @fpr: the key fingerprint
* @fprlen: the length of the fingerprint
*
* Derive the key ID from the key fingerprint.
* For version 3 keys, this is not working.
**/
u32
cdk_pk_fingerprint_get_keyid (const byte * fpr, size_t fprlen, u32 * keyid)
{
u32 lowbits = 0;
/* In this case we say the key is a V3 RSA key and we can't
use the fingerprint to get the keyid. */
if (fpr && fprlen == 16)
{
keyid[0] = 0;
keyid[1] = 0;
return 0;
}
else if (keyid && fpr)
{
keyid[0] = _cdk_buftou32 (fpr + 12);
keyid[1] = _cdk_buftou32 (fpr + 16);
lowbits = keyid[1];
}
else if (fpr)
lowbits = _cdk_buftou32 (fpr + 16);
return lowbits;
}
/**
* cdk_pk_get_keyid:
* @pk: the public key
* @keyid: buffer to store the key ID
*
* Calculate the key ID of the given public key.
**/
u32
cdk_pk_get_keyid (cdk_pubkey_t pk, u32 * keyid)
{
u32 lowbits = 0;
byte buf[24];
if (pk && (!pk->keyid[0] || !pk->keyid[1]))
{
if (pk->version < 4 && is_RSA (pk->pubkey_algo))
{
byte p[MAX_MPI_BYTES];
size_t n;
n = MAX_MPI_BYTES;
_gnutls_mpi_print (pk->mpi[0], p, &n);
pk->keyid[0] =
p[n - 8] << 24 | p[n - 7] << 16 | p[n - 6] << 8 | p[n - 5];
pk->keyid[1] =
p[n - 4] << 24 | p[n - 3] << 16 | p[n - 2] << 8 | p[n - 1];
}
else if (pk->version == 4)
{
cdk_pk_get_fingerprint (pk, buf);
pk->keyid[0] = _cdk_buftou32 (buf + 12);
pk->keyid[1] = _cdk_buftou32 (buf + 16);
}
}
lowbits = pk ? pk->keyid[1] : 0;
if (keyid && pk)
{
keyid[0] = pk->keyid[0];
keyid[1] = pk->keyid[1];
}
return lowbits;
}
/**
* cdk_sk_get_keyid:
* @sk: the secret key
* @keyid: buffer to hold the key ID
*
* Calculate the key ID of the secret key, actually the public key.
**/
u32
cdk_sk_get_keyid (cdk_pkt_seckey_t sk, u32 * keyid)
{
u32 lowbits = 0;
if (sk && sk->pk)
{
lowbits = cdk_pk_get_keyid (sk->pk, keyid);
sk->keyid[0] = sk->pk->keyid[0];
sk->keyid[1] = sk->pk->keyid[1];
}
return lowbits;
}
/**
* cdk_sig_get_keyid:
* @sig: the signature
* @keyid: buffer to hold the key ID
*
* Retrieve the key ID from the given signature.
**/
u32
cdk_sig_get_keyid (cdk_pkt_signature_t sig, u32 * keyid)
{
u32 lowbits = sig ? sig->keyid[1] : 0;
if (keyid && sig)
{
keyid[0] = sig->keyid[0];
keyid[1] = sig->keyid[1];
}
return lowbits;
}
/* Return the key ID from the given packet.
If this is not possible, 0 is returned */
u32
_cdk_pkt_get_keyid (cdk_packet_t pkt, u32 * keyid)
{
u32 lowbits;
if (!pkt)
return 0;
switch (pkt->pkttype)
{
case CDK_PKT_PUBLIC_KEY:
case CDK_PKT_PUBLIC_SUBKEY:
lowbits = cdk_pk_get_keyid (pkt->pkt.public_key, keyid);
break;
case CDK_PKT_SECRET_KEY:
case CDK_PKT_SECRET_SUBKEY:
lowbits = cdk_sk_get_keyid (pkt->pkt.secret_key, keyid);
break;
case CDK_PKT_SIGNATURE:
lowbits = cdk_sig_get_keyid (pkt->pkt.signature, keyid);
break;
default:
lowbits = 0;
break;
}
return lowbits;
}
/* Get the fingerprint of the packet if possible. */
cdk_error_t
_cdk_pkt_get_fingerprint (cdk_packet_t pkt, byte * fpr)
{
if (!pkt || !fpr)
return CDK_Inv_Value;
switch (pkt->pkttype)
{
case CDK_PKT_PUBLIC_KEY:
case CDK_PKT_PUBLIC_SUBKEY:
return cdk_pk_get_fingerprint (pkt->pkt.public_key, fpr);
case CDK_PKT_SECRET_KEY:
case CDK_PKT_SECRET_SUBKEY:
return cdk_pk_get_fingerprint (pkt->pkt.secret_key->pk, fpr);
default:
return CDK_Inv_Mode;
}
return 0;
}
|