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sec_negotiate_gnutls.h
1 /* FreeTDS - Library of routines accessing Sybase and Microsoft databases
2  * Copyright (C) 2015 Frediano Ziglio
3  *
4  * This library is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Library General Public
6  * License as published by the Free Software Foundation; either
7  * version 2 of the License, or (at your option) any later version.
8  *
9  * This library is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Library General Public License for more details.
13  *
14  * You should have received a copy of the GNU Library General Public
15  * License along with this library; if not, write to the
16  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17  * Boston, MA 02111-1307, USA.
18  */
19 
20 #include <gnutls/gnutls.h>
21 #include <gnutls/crypto.h>
22 #ifdef HAVE_GNUTLS_ABSTRACT_H
23 # include <gnutls/abstract.h>
24 #endif
25 
26 #if !defined(HAVE_NETTLE) || !defined(HAVE_GMP) || !defined(HAVE_GNUTLS_RND)
27 # include <gcrypt.h>
28 #endif
29 
30 #ifndef HAVE_NETTLE
31 # include <libtasn1.h>
32 #endif
33 
34 #ifdef HAVE_NETTLE
35 # include <nettle/asn1.h>
36 # include <nettle/rsa.h>
37 # include <nettle/bignum.h>
38 #endif
39 
51 #ifndef HAVE_GNUTLS
52 #error HAVE_GNUTLS not defines, this file should not be included
53 #endif
54 
55 /* emulate GMP if not present */
56 #ifndef HAVE_GMP
57 #define HAVE_GMP 1
58 
59 typedef struct {
60  gcry_mpi_t num;
61 } mpz_t[1];
62 
63 #define mpz_powm(w,n,e,m) \
64  gcry_mpi_powm((w)->num, (n)->num, (e)->num, (m)->num);
65 #define mpz_init(n) do { (n)->num = NULL; } while(0)
66 #define mpz_clear(n) gcry_mpi_release((n)->num)
67 
68 #endif
69 
70 
71 /* emulate Nettle is not present */
72 #ifndef HAVE_NETTLE
73 #define HAVE_NETTLE 1
74 
75 typedef void nettle_random_func(void *ctx, size_t len, uint8_t *out);
76 
77 static inline void
78 nettle_mpz_set_str_256_u(mpz_t x, unsigned length, const uint8_t *s)
79 {
80  gcry_mpi_scan(&x->num, GCRYMPI_FMT_USG, s, length, NULL);
81 }
82 
83 static inline void
84 nettle_mpz_get_str_256(unsigned length, uint8_t *s, const mpz_t x)
85 {
86  gcry_mpi_print(GCRYMPI_FMT_USG, s, length, NULL, x->num);
87 }
88 
90  const unsigned char *data, *data_end;
91  unsigned long length;
92  unsigned long type;
93 };
94 
95 enum asn1_iterator_result {
96  ASN1_ITERATOR_ERROR,
97  ASN1_ITERATOR_PRIMITIVE,
98  ASN1_ITERATOR_CONSTRUCTED,
99  ASN1_ITERATOR_END,
100 };
101 
102 enum {
103  ASN1_SEQUENCE = ASN1_TAG_SEQUENCE,
104 };
105 
106 static enum asn1_iterator_result
107 asn1_der_iterator_next(struct asn1_der_iterator *der)
108 {
109  unsigned char cls;
110  unsigned long tag;
111  int len;
112  long l;
113 
114  if (asn1_get_tag_der(der->data, der->data_end - der->data, &cls, &len, &tag) != ASN1_SUCCESS)
115  return ASN1_ITERATOR_ERROR;
116  der->type = tag;
117  der->data += len;
118  l = asn1_get_length_der(der->data, der->data_end - der->data, &len);
119  if (l < 0)
120  return ASN1_ITERATOR_ERROR;
121  der->data += len;
122  der->length = l;
123  if (cls == ASN1_CLASS_STRUCTURED)
124  return ASN1_ITERATOR_CONSTRUCTED;
125  return ASN1_ITERATOR_PRIMITIVE;
126 }
127 
128 static enum asn1_iterator_result
129 asn1_der_iterator_first(struct asn1_der_iterator *der, int size, const void *der_buf)
130 {
131  der->data = (const unsigned char *) der_buf;
132  der->data_end = der->data + size;
133 
134  return asn1_der_iterator_next(der);
135 }
136 
138  unsigned size;
139  mpz_t n, e;
140 };
141 
142 static void
143 rsa_public_key_init(struct rsa_public_key *key)
144 {
145  key->size = 0;
146  mpz_init(key->n);
147  mpz_init(key->e);
148 }
149 
150 static void
151 rsa_public_key_clear(struct rsa_public_key *key)
152 {
153  mpz_clear(key->n);
154  mpz_clear(key->e);
155 }
156 
157 static int
158 rsa_public_key_from_der_iterator(struct rsa_public_key *key, unsigned key_bits, struct asn1_der_iterator *der)
159 {
160  enum asn1_iterator_result ret;
161 
162  ret = asn1_der_iterator_next(der);
163  if (ret != ASN1_ITERATOR_PRIMITIVE || der->type != ASN1_TAG_INTEGER)
164  return 0;
165  gcry_mpi_scan(&key->n->num, GCRYMPI_FMT_USG, der->data, der->length, NULL);
166  key->size = (gcry_mpi_get_nbits(key->n->num)+7)/8;
167  der->data += der->length;
168 
169  ret = asn1_der_iterator_next(der);
170  if (ret != ASN1_ITERATOR_PRIMITIVE || der->type != ASN1_TAG_INTEGER)
171  return 0;
172  gcry_mpi_scan(&key->e->num, GCRYMPI_FMT_USG, der->data, der->length, NULL);
173 
174  return 1;
175 }
176 
177 static void
178 sha1(uint8_t *hash, const void *data, size_t len)
179 {
180  gcry_md_hash_buffer(GCRY_MD_SHA1, hash, data, len);
181 }
182 #else
183 static void
184 sha1(uint8_t *hash, const void *data, size_t len)
185 {
186  struct sha1_ctx ctx;
187  sha1_init(&ctx);
188  sha1_update(&ctx, len, (const uint8_t *) data);
189  sha1_digest(&ctx, 20, hash);
190 }
191 #endif
192 
193 
194 static void
195 rnd_func(void *ctx, size_t len, uint8_t * out)
196 {
197  tds_random_buffer(out, len);
198 }
199 
200 #define dumpl(b,l) tdsdump_dump_buf(TDS_DBG_INFO1, #b, b, l)
201 #ifndef dumpl
202 #define dumpl(b,l) do {} while(0)
203 #endif
204 #define dump(b) dumpl(b, sizeof(b))
205 
206 /* OAEP configuration parameters */
207 #define hash_func sha1
208 enum { hash_len = 20 }; /* sha1 length */
209 enum { key_size_max = 1024 }; /* max key in bytes */
210 static const char label[] = "";
211 
212 static void
213 memxor(uint8_t *dest, const uint8_t *src, size_t len)
214 {
215  size_t n;
216  for (n = 0; n < len; ++n)
217  dest[n] = dest[n] ^ src[n];
218 }
219 
220 static void
221 mgf_mask(uint8_t *dest, size_t dest_len, const uint8_t *mask, size_t mask_len)
222 {
223  unsigned n = 0;
224  uint8_t hash[hash_len];
225  uint8_t seed[mask_len + 4];
226 
227  memcpy(seed, mask, mask_len);
228  /* we always have some data and check is done internally */
229  for (;;) {
230  TDS_PUT_UA4BE(seed+mask_len, n);
231 
232  hash_func(hash, seed, sizeof(seed));
233  if (dest_len <= hash_len) {
234  memxor(dest, hash, dest_len);
235  break;
236  }
237 
238  memxor(dest, hash, hash_len);
239  dest += hash_len;
240  dest_len -= hash_len;
241  ++n;
242  }
243 }
244 
245 static int
246 oaep_encrypt(size_t key_size, void *random_ctx, nettle_random_func *random,
247  size_t length, const uint8_t *message, mpz_t m)
248 {
249  /* EM: 0x00 ROS (HASH 0x00.. 0x01 message) */
250  struct {
251  uint8_t all[1]; /* zero but used to access all data */
252  uint8_t ros[hash_len];
253  uint8_t db[key_size_max - hash_len - 1];
254  } em;
255  const unsigned db_len = key_size - hash_len - 1;
256 
257  if (length + hash_len * 2 + 2 > key_size)
258  /* Message too long for this key. */
259  return 0;
260 
261  /* create db */
262  memset(&em, 0, sizeof(em));
263  hash_func(em.db, label, strlen(label));
264  em.all[key_size - length - 1] = 0x1;
265  memcpy(em.all+(key_size - length), message, length);
266  dumpl(em.db, db_len);
267 
268  /* create ros */
269  random(random_ctx, hash_len, em.ros);
270  dump(em.ros);
271 
272  /* mask db */
273  mgf_mask(em.db, db_len, em.ros, hash_len);
274  dumpl(em.db, db_len);
275 
276  /* mask ros */
277  mgf_mask(em.ros, hash_len, em.db, db_len);
278  dump(em.ros);
279 
280  nettle_mpz_set_str_256_u(m, key_size, em.all);
281 
282  return 1;
283 }
284 
285 static int
286 rsa_encrypt_oaep(const struct rsa_public_key *key, void *random_ctx, nettle_random_func *random,
287  size_t length, const uint8_t *message, mpz_t gibberish)
288 {
289  if (!oaep_encrypt(key->size, random_ctx, random, length, message, gibberish))
290  return 0;
291 
292  mpz_powm(gibberish, gibberish, key->e, key->n);
293  return 1;
294 }
295 
296 static void*
297 tds5_rsa_encrypt(const void *key, size_t key_len, const void *nonce, size_t nonce_len, const char *pwd, size_t *em_size)
298 {
299  int ret;
300  mpz_t p;
301  gnutls_datum_t pubkey_datum = { (unsigned char *) key, key_len };
302  struct asn1_der_iterator der;
303  struct rsa_public_key pubkey;
304  uint8_t *message;
305  size_t message_len, pwd_len;
306  uint8_t *em = NULL;
307  unsigned char der_buf[2048];
308  size_t size = sizeof(der_buf);
309 
310  mpz_init(p);
311  rsa_public_key_init(&pubkey);
312 
313  pwd_len = strlen(pwd);
314  message_len = nonce_len + pwd_len;
315  message = tds_new(uint8_t, message_len);
316  if (!message)
317  return NULL;
318  memcpy(message, nonce, nonce_len);
319  memcpy(message + nonce_len, pwd, pwd_len);
320 
321  /* use nettle directly */
322  /* parse PEM, get DER */
323  ret = gnutls_pem_base64_decode("RSA PUBLIC KEY", &pubkey_datum, der_buf, &size);
324  if (ret) {
325  tdsdump_log(TDS_DBG_ERROR, "Error %d decoding public key: %s\n", ret, gnutls_strerror(ret));
326  goto error;
327  }
328 
329  /* get key with nettle using DER */
330  ret = asn1_der_iterator_first(&der, size, der_buf);
331  if (ret != ASN1_ITERATOR_CONSTRUCTED || der.type != ASN1_SEQUENCE) {
332  tdsdump_log(TDS_DBG_ERROR, "Invalid DER content\n");
333  goto error;
334  }
335 
336  ret = rsa_public_key_from_der_iterator(&pubkey, key_size_max * 8, &der);
337  if (!ret) {
338  tdsdump_log(TDS_DBG_ERROR, "Invalid DER content\n");
339  goto error;
340  }
341 
342  /* get password encrypted */
343  ret = rsa_encrypt_oaep(&pubkey, NULL, rnd_func, message_len, message, p);
344  if (!ret) {
345  tdsdump_log(TDS_DBG_ERROR, "Error encrypting message\n");
346  goto error;
347  }
348 
349  em = tds_new(uint8_t, pubkey.size);
350  *em_size = pubkey.size;
351  if (!em)
352  goto error;
353 
354  nettle_mpz_get_str_256(pubkey.size, em, p);
355 
356  tdsdump_dump_buf(TDS_DBG_INFO1, "em", em, pubkey.size);
357 
358 error:
359  free(message);
360  rsa_public_key_clear(&pubkey);
361  mpz_clear(p);
362  return em;
363 }
364 
void tdsdump_dump_buf(const char *file, unsigned int level_line, const char *msg, const void *buf, size_t length)
Dump the contents of data into the log file in a human readable format.
Definition: log.c:255
Definition: sec_negotiate_gnutls.h:137
Definition: sec_negotiate_gnutls.h:89
Definition: sec_negotiate_gnutls.h:59
void tdsdump_log(const char *file, unsigned int level_line, const char *fmt,...)
Write a message to the debug log.
Definition: log.c:353