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sec_negotiate_gnutls.h
/* FreeTDS - Library of routines accessing Sybase and Microsoft databases
* Copyright (C) 2015 Frediano Ziglio
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>
#ifdef HAVE_GNUTLS_ABSTRACT_H
# include <gnutls/abstract.h>
#endif
#if !defined(HAVE_NETTLE) || !defined(HAVE_GMP) || !defined(HAVE_GNUTLS_RND)
# include <gcrypt.h>
#endif
#ifndef HAVE_NETTLE
# include <libtasn1.h>
#endif
#ifdef HAVE_NETTLE
# include <nettle/asn1.h>
# include <nettle/rsa.h>
# include <nettle/bignum.h>
#endif
#ifndef HAVE_GNUTLS
#error HAVE_GNUTLS not defined, this file should not be included
#endif
/* emulate GMP if not present */
#ifndef HAVE_GMP
#define HAVE_GMP 1
typedef struct {
gcry_mpi_t num;
} mpz_t[1];
#define mpz_powm(w,n,e,m) \
gcry_mpi_powm((w)->num, (n)->num, (e)->num, (m)->num);
#define mpz_init(n) do { (n)->num = NULL; } while(0)
#define mpz_clear(n) gcry_mpi_release((n)->num)
#endif
/* emulate Nettle if not present */
#ifndef HAVE_NETTLE
#define HAVE_NETTLE 1
typedef void nettle_random_func(void *ctx, size_t len, uint8_t *out);
static inline void
nettle_mpz_set_str_256_u(mpz_t x, unsigned length, const uint8_t *s)
{
gcry_mpi_scan(&x->num, GCRYMPI_FMT_USG, s, length, NULL);
}
static inline void
nettle_mpz_get_str_256(unsigned length, uint8_t *s, const mpz_t x)
{
gcry_mpi_print(GCRYMPI_FMT_USG, s, length, NULL, x->num);
}
struct asn1_der_iterator {
const unsigned char *data, *data_end;
unsigned long length;
unsigned long type;
};
enum asn1_iterator_result {
ASN1_ITERATOR_ERROR,
ASN1_ITERATOR_PRIMITIVE,
ASN1_ITERATOR_CONSTRUCTED,
ASN1_ITERATOR_END,
};
enum {
ASN1_SEQUENCE = ASN1_TAG_SEQUENCE,
};
static enum asn1_iterator_result
asn1_der_iterator_next(struct asn1_der_iterator *der)
{
unsigned char cls;
unsigned long tag;
int len;
long l;
if (asn1_get_tag_der(der->data, der->data_end - der->data, &cls, &len, &tag) != ASN1_SUCCESS)
return ASN1_ITERATOR_ERROR;
der->type = tag;
der->data += len;
l = asn1_get_length_der(der->data, der->data_end - der->data, &len);
if (l < 0)
return ASN1_ITERATOR_ERROR;
der->data += len;
der->length = l;
if (cls == ASN1_CLASS_STRUCTURED)
return ASN1_ITERATOR_CONSTRUCTED;
return ASN1_ITERATOR_PRIMITIVE;
}
static enum asn1_iterator_result
asn1_der_iterator_first(struct asn1_der_iterator *der, int size, const void *der_buf)
{
der->data = (const unsigned char *) der_buf;
der->data_end = der->data + size;
return asn1_der_iterator_next(der);
}
struct rsa_public_key {
unsigned size;
mpz_t n, e;
};
static void
rsa_public_key_init(struct rsa_public_key *key)
{
key->size = 0;
mpz_init(key->n);
mpz_init(key->e);
}
static void
rsa_public_key_clear(struct rsa_public_key *key)
{
mpz_clear(key->n);
mpz_clear(key->e);
}
static int
rsa_public_key_from_der_iterator(struct rsa_public_key *key, unsigned key_bits, struct asn1_der_iterator *der)
{
enum asn1_iterator_result ret;
ret = asn1_der_iterator_next(der);
if (ret != ASN1_ITERATOR_PRIMITIVE || der->type != ASN1_TAG_INTEGER)
return 0;
gcry_mpi_scan(&key->n->num, GCRYMPI_FMT_USG, der->data, der->length, NULL);
key->size = (gcry_mpi_get_nbits(key->n->num)+7)/8;
der->data += der->length;
ret = asn1_der_iterator_next(der);
if (ret != ASN1_ITERATOR_PRIMITIVE || der->type != ASN1_TAG_INTEGER)
return 0;
gcry_mpi_scan(&key->e->num, GCRYMPI_FMT_USG, der->data, der->length, NULL);
return 1;
}
static void
sha1(uint8_t *hash, const void *data, size_t len)
{
gcry_md_hash_buffer(GCRY_MD_SHA1, hash, data, len);
}
#else
static void
sha1(uint8_t *hash, const void *data, size_t len)
{
struct sha1_ctx ctx;
sha1_init(&ctx);
sha1_update(&ctx, len, (const uint8_t *) data);
sha1_digest(&ctx, 20, hash);
}
#endif
#define dumpl(b,l) tdsdump_dump_buf(TDS_DBG_INFO1, #b, b, l)
#ifndef dumpl
#define dumpl(b,l) do {} while(0)
#endif
#define dump(b) dumpl(b, sizeof(b))
/* OAEP configuration parameters */
#define hash_func sha1
enum { hash_len = 20 }; /* sha1 length */
enum { key_size_max = 1024 }; /* max key in bytes */
static const char label[] = "";
static void
memxor(uint8_t *dest, const uint8_t *src, size_t len)
{
size_t n;
for (n = 0; n < len; ++n)
dest[n] = dest[n] ^ src[n];
}
static void
mgf_mask(uint8_t *dest, size_t dest_len, const uint8_t *mask, size_t mask_len)
{
unsigned n = 0;
uint8_t hash[hash_len];
uint8_t seed[mask_len + 4];
memcpy(seed, mask, mask_len);
/* we always have some data and check is done internally */
for (;;) {
TDS_PUT_UA4BE(seed+mask_len, n);
hash_func(hash, seed, sizeof(seed));
if (dest_len <= hash_len) {
memxor(dest, hash, dest_len);
break;
}
memxor(dest, hash, hash_len);
dest += hash_len;
dest_len -= hash_len;
++n;
}
}
static int
oaep_encrypt(size_t key_size, size_t length, const uint8_t *message, mpz_t m)
{
/* EM: 0x00 ROS (HASH 0x00.. 0x01 message) */
struct {
uint8_t all[1]; /* zero but used to access all data */
uint8_t ros[hash_len];
uint8_t db[key_size_max - hash_len - 1];
} em;
const unsigned db_len = key_size - hash_len - 1;
if (length + hash_len * 2 + 2 > key_size)
/* Message too long for this key. */
return 0;
/* create db */
memset(&em, 0, sizeof(em));
hash_func(em.db, label, strlen(label));
em.all[key_size - length - 1] = 0x1;
memcpy(em.all+(key_size - length), message, length);
dumpl(em.db, db_len);
/* create ros */
tds_random_buffer(em.ros, hash_len);
dump(em.ros);
/* mask db */
mgf_mask(em.db, db_len, em.ros, hash_len);
dumpl(em.db, db_len);
/* mask ros */
mgf_mask(em.ros, hash_len, em.db, db_len);
dump(em.ros);
nettle_mpz_set_str_256_u(m, key_size, em.all);
return 1;
}
static int
rsa_encrypt_oaep(const struct rsa_public_key *key,
size_t length, const uint8_t *message, mpz_t gibberish)
{
if (!oaep_encrypt(key->size, length, message, gibberish))
return 0;
mpz_powm(gibberish, gibberish, key->e, key->n);
return 1;
}
static void*
tds5_rsa_encrypt(const void *key, size_t key_len, const void *nonce, size_t nonce_len, const char *pwd, size_t *em_size)
{
int ret;
mpz_t p;
gnutls_datum_t pubkey_datum = { (unsigned char *) key, key_len };
struct asn1_der_iterator der;
struct rsa_public_key pubkey;
uint8_t *message;
size_t message_len, pwd_len;
uint8_t *em = NULL;
unsigned char der_buf[2048];
size_t size = sizeof(der_buf);
mpz_init(p);
rsa_public_key_init(&pubkey);
pwd_len = strlen(pwd);
message_len = nonce_len + pwd_len;
message = tds_new(uint8_t, message_len);
if (!message)
return NULL;
memcpy(message, nonce, nonce_len);
memcpy(message + nonce_len, pwd, pwd_len);
/* use nettle directly */
/* parse PEM, get DER */
ret = gnutls_pem_base64_decode("RSA PUBLIC KEY", &pubkey_datum, der_buf, &size);
if (ret) {
tdsdump_log(TDS_DBG_ERROR, "Error %d decoding public key: %s\n", ret, gnutls_strerror(ret));
goto error;
}
/* get key with nettle using DER */
ret = asn1_der_iterator_first(&der, size, der_buf);
if (ret != ASN1_ITERATOR_CONSTRUCTED || der.type != ASN1_SEQUENCE) {
tdsdump_log(TDS_DBG_ERROR, "Invalid DER content\n");
goto error;
}
ret = rsa_public_key_from_der_iterator(&pubkey, key_size_max * 8, &der);
if (!ret) {
tdsdump_log(TDS_DBG_ERROR, "Invalid DER content\n");
goto error;
}
/* get password encrypted */
ret = rsa_encrypt_oaep(&pubkey, message_len, message, p);
if (!ret) {
tdsdump_log(TDS_DBG_ERROR, "Error encrypting message\n");
goto error;
}
em = tds_new(uint8_t, pubkey.size);
*em_size = pubkey.size;
if (!em)
goto error;
nettle_mpz_get_str_256(pubkey.size, em, p);
tdsdump_dump_buf(TDS_DBG_INFO1, "em", em, pubkey.size);
error:
free(message);
rsa_public_key_clear(&pubkey);
mpz_clear(p);
return em;
}
mpz_t
Definition sec_negotiate_gnutls.h:59
asn1_der_iterator
Definition sec_negotiate_gnutls.h:89
rsa_public_key
Definition sec_negotiate_gnutls.h:137