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pgp-mpi-internal.c
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1 /*
2  * pgp-mpi-internal.c
3  * OpenPGP MPI functions.
4  *
5  * Copyright (c) 2005 Marko Kreen
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  * notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  * notice, this list of conditions and the following disclaimer in the
15  * documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * contrib/pgcrypto/pgp-mpi-internal.c
30  */
31 #include "postgres.h"
32 
33 #include "imath.h"
34 
35 #include "px.h"
36 #include "pgp.h"
37 
38 static mpz_t *
40 {
41  mpz_t *mp = mp_int_alloc();
42 
43  mp_int_init_size(mp, 256);
44  return mp;
45 }
46 
47 static void
49 {
50  if (!a)
51  return;
52  /* fixme: no clear? */
53  mp_int_free(a);
54 }
55 
56 
57 static int
58 mp_px_rand(uint32 bits, mpz_t *res)
59 {
60  unsigned bytes = (bits + 7) / 8;
61  int last_bits = bits & 7;
62  uint8 *buf;
63 
64  buf = px_alloc(bytes);
65  if (!pg_strong_random(buf, bytes))
66  {
67  px_free(buf);
68  return PXE_NO_RANDOM;
69  }
70 
71  /* clear unnecessary bits and set last bit to one */
72  if (last_bits)
73  {
74  buf[0] >>= 8 - last_bits;
75  buf[0] |= 1 << (last_bits - 1);
76  }
77  else
78  buf[0] |= 1 << 7;
79 
80  mp_int_read_unsigned(res, buf, bytes);
81 
82  px_free(buf);
83 
84  return 0;
85 }
86 
87 static void
88 mp_modmul(mpz_t *a, mpz_t *b, mpz_t *p, mpz_t *res)
89 {
90  mpz_t *tmp = mp_new();
91 
92  mp_int_mul(a, b, tmp);
93  mp_int_mod(tmp, p, res);
94  mp_clear_free(tmp);
95 }
96 
97 static mpz_t *
99 {
100  mpz_t *bn = mp_new();
101 
102  mp_int_read_unsigned(bn, n->data, n->bytes);
103 
104  if (!bn)
105  return NULL;
106  if (mp_int_count_bits(bn) != n->bits)
107  {
108  px_debug("mpi_to_bn: bignum conversion failed: mpi=%d, bn=%d",
109  n->bits, mp_int_count_bits(bn));
110  mp_clear_free(bn);
111  return NULL;
112  }
113  return bn;
114 }
115 
116 static PGP_MPI *
118 {
119  int res;
120  PGP_MPI *n;
121  int bytes;
122 
123  res = pgp_mpi_alloc(mp_int_count_bits(bn), &n);
124  if (res < 0)
125  return NULL;
126 
127  bytes = (mp_int_count_bits(bn) + 7) / 8;
128  if (bytes != n->bytes)
129  {
130  px_debug("bn_to_mpi: bignum conversion failed: bn=%d, mpi=%d",
131  bytes, n->bytes);
132  pgp_mpi_free(n);
133  return NULL;
134  }
135  mp_int_to_unsigned(bn, n->data, n->bytes);
136  return n;
137 }
138 
139 /*
140  * Decide the number of bits in the random component k
141  *
142  * It should be in the same range as p for signing (which
143  * is deprecated), but can be much smaller for encrypting.
144  *
145  * Until I research it further, I just mimic gpg behaviour.
146  * It has a special mapping table, for values <= 5120,
147  * above that it uses 'arbitrary high number'. Following
148  * algorithm hovers 10-70 bits above gpg values. And for
149  * larger p, it uses gpg's algorithm.
150  *
151  * The point is - if k gets large, encryption will be
152  * really slow. It does not matter for decryption.
153  */
154 static int
155 decide_k_bits(int p_bits)
156 {
157  if (p_bits <= 5120)
158  return p_bits / 10 + 160;
159  else
160  return (p_bits / 8 + 200) * 3 / 2;
161 }
162 
163 int
165  PGP_MPI **c1_p, PGP_MPI **c2_p)
166 {
167  int res = PXE_PGP_MATH_FAILED;
168  int k_bits;
169  mpz_t *m = mpi_to_bn(_m);
170  mpz_t *p = mpi_to_bn(pk->pub.elg.p);
171  mpz_t *g = mpi_to_bn(pk->pub.elg.g);
172  mpz_t *y = mpi_to_bn(pk->pub.elg.y);
173  mpz_t *k = mp_new();
174  mpz_t *yk = mp_new();
175  mpz_t *c1 = mp_new();
176  mpz_t *c2 = mp_new();
177 
178  if (!m || !p || !g || !y || !k || !yk || !c1 || !c2)
179  goto err;
180 
181  /*
182  * generate k
183  */
184  k_bits = decide_k_bits(mp_int_count_bits(p));
185  res = mp_px_rand(k_bits, k);
186  if (res < 0)
187  return res;
188 
189  /*
190  * c1 = g^k c2 = m * y^k
191  */
192  mp_int_exptmod(g, k, p, c1);
193  mp_int_exptmod(y, k, p, yk);
194  mp_modmul(m, yk, p, c2);
195 
196  /* result */
197  *c1_p = bn_to_mpi(c1);
198  *c2_p = bn_to_mpi(c2);
199  if (*c1_p && *c2_p)
200  res = 0;
201 err:
202  mp_clear_free(c2);
203  mp_clear_free(c1);
204  mp_clear_free(yk);
205  mp_clear_free(k);
206  mp_clear_free(y);
207  mp_clear_free(g);
208  mp_clear_free(p);
209  mp_clear_free(m);
210  return res;
211 }
212 
213 int
215  PGP_MPI **msg_p)
216 {
217  int res = PXE_PGP_MATH_FAILED;
218  mpz_t *c1 = mpi_to_bn(_c1);
219  mpz_t *c2 = mpi_to_bn(_c2);
220  mpz_t *p = mpi_to_bn(pk->pub.elg.p);
221  mpz_t *x = mpi_to_bn(pk->sec.elg.x);
222  mpz_t *c1x = mp_new();
223  mpz_t *div = mp_new();
224  mpz_t *m = mp_new();
225 
226  if (!c1 || !c2 || !p || !x || !c1x || !div || !m)
227  goto err;
228 
229  /*
230  * m = c2 / (c1^x)
231  */
232  mp_int_exptmod(c1, x, p, c1x);
233  mp_int_invmod(c1x, p, div);
234  mp_modmul(c2, div, p, m);
235 
236  /* result */
237  *msg_p = bn_to_mpi(m);
238  if (*msg_p)
239  res = 0;
240 err:
241  mp_clear_free(m);
242  mp_clear_free(div);
243  mp_clear_free(c1x);
244  mp_clear_free(x);
245  mp_clear_free(p);
246  mp_clear_free(c2);
247  mp_clear_free(c1);
248  return res;
249 }
250 
251 int
253 {
254  int res = PXE_PGP_MATH_FAILED;
255  mpz_t *m = mpi_to_bn(_m);
256  mpz_t *e = mpi_to_bn(pk->pub.rsa.e);
257  mpz_t *n = mpi_to_bn(pk->pub.rsa.n);
258  mpz_t *c = mp_new();
259 
260  if (!m || !e || !n || !c)
261  goto err;
262 
263  /*
264  * c = m ^ e
265  */
266  mp_int_exptmod(m, e, n, c);
267 
268  *c_p = bn_to_mpi(c);
269  if (*c_p)
270  res = 0;
271 err:
272  mp_clear_free(c);
273  mp_clear_free(n);
274  mp_clear_free(e);
275  mp_clear_free(m);
276  return res;
277 }
278 
279 int
281 {
282  int res = PXE_PGP_MATH_FAILED;
283  mpz_t *c = mpi_to_bn(_c);
284  mpz_t *d = mpi_to_bn(pk->sec.rsa.d);
285  mpz_t *n = mpi_to_bn(pk->pub.rsa.n);
286  mpz_t *m = mp_new();
287 
288  if (!m || !d || !n || !c)
289  goto err;
290 
291  /*
292  * m = c ^ d
293  */
294  mp_int_exptmod(c, d, n, m);
295 
296  *m_p = bn_to_mpi(m);
297  if (*m_p)
298  res = 0;
299 err:
300  mp_clear_free(m);
301  mp_clear_free(n);
302  mp_clear_free(d);
303  mp_clear_free(c);
304  return res;
305 }
mp_result mp_int_mul(mp_int a, mp_int b, mp_int c)
Definition: imath.c:857
mp_result mp_int_invmod(mp_int a, mp_int m, mp_int c)
Definition: imath.c:1474
struct PGP_PubKey::@5::@7 elg
mp_result mp_int_read_unsigned(mp_int z, unsigned char *buf, int len)
Definition: imath.c:2147
uint8 * data
Definition: pgp.h:181
def bytes(source, encoding='ascii', errors='strict')
#define px_free(p)
Definition: px.h:46
unsigned char uint8
Definition: c.h:356
Definition: imath.h:52
mp_result mp_int_to_unsigned(mp_int z, unsigned char *buf, int limit)
Definition: imath.c:2137
mp_result mp_int_mod(mp_int a, mp_int m, mp_int c)
Definition: imath.c:1122
#define PXE_NO_RANDOM
Definition: px.h:75
mp_result mp_int_count_bits(mp_int z)
Definition: imath.c:2038
int bytes
Definition: pgp.h:183
static mpz_t * mpi_to_bn(PGP_MPI *n)
struct PGP_PubKey::@5::@8 rsa
int pgp_elgamal_encrypt(PGP_PubKey *pk, PGP_MPI *_m, PGP_MPI **c1_p, PGP_MPI **c2_p)
static mpz_t * mp_new()
mp_result mp_int_exptmod(mp_int a, mp_int b, mp_int m, mp_int c)
Definition: imath.c:1369
int pgp_mpi_alloc(int bits, PGP_MPI **mpi)
Definition: pgp-mpi.c:37
void mp_int_free(mp_int z)
Definition: imath.c:602
char * c
static char * buf
Definition: pg_test_fsync.c:68
int pgp_rsa_encrypt(PGP_PubKey *pk, PGP_MPI *_m, PGP_MPI **c_p)
unsigned int uint32
Definition: c.h:358
Definition: pgp.h:179
mp_result mp_int_init_size(mp_int z, mp_size prec)
Definition: imath.c:490
int pgp_mpi_free(PGP_MPI *mpi)
Definition: pgp-mpi.c:70
static int decide_k_bits(int p_bits)
static PGP_MPI * bn_to_mpi(mpz_t *bn)
union PGP_PubKey::@6 sec
bool pg_strong_random(void *buf, size_t len)
void px_debug(const char *fmt,...)
Definition: px.c:152
static int mp_px_rand(uint32 bits, mpz_t *res)
static void mp_modmul(mpz_t *a, mpz_t *b, mpz_t *p, mpz_t *res)
union PGP_PubKey::@5 pub
int pgp_elgamal_decrypt(PGP_PubKey *pk, PGP_MPI *_c1, PGP_MPI *_c2, PGP_MPI **msg_p)
#define PXE_PGP_MATH_FAILED
Definition: px.h:87
#define px_alloc(s)
Definition: px.h:44
e
Definition: preproc-init.c:82
int pgp_rsa_decrypt(PGP_PubKey *pk, PGP_MPI *_c, PGP_MPI **m_p)
mp_int mp_int_alloc(void)
Definition: imath.c:479
static void mp_clear_free(mpz_t *a)
int bits
Definition: pgp.h:182