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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 #include "pgp.h"
35 #include "px.h"
36 
37 static mpz_t *
39 {
40  mpz_t *mp = mp_int_alloc();
41 
42  mp_int_init_size(mp, 256);
43  return mp;
44 }
45 
46 static void
48 {
49  if (!a)
50  return;
51  /* fixme: no clear? */
52  mp_int_free(a);
53 }
54 
55 
56 static int
57 mp_px_rand(uint32 bits, mpz_t *res)
58 {
59  unsigned bytes = (bits + 7) / 8;
60  int last_bits = bits & 7;
61  uint8 *buf;
62 
63  buf = px_alloc(bytes);
64  if (!pg_strong_random(buf, bytes))
65  {
66  px_free(buf);
67  return PXE_NO_RANDOM;
68  }
69 
70  /* clear unnecessary bits and set last bit to one */
71  if (last_bits)
72  {
73  buf[0] >>= 8 - last_bits;
74  buf[0] |= 1 << (last_bits - 1);
75  }
76  else
77  buf[0] |= 1 << 7;
78 
79  mp_int_read_unsigned(res, buf, bytes);
80 
81  px_free(buf);
82 
83  return 0;
84 }
85 
86 static void
87 mp_modmul(mpz_t *a, mpz_t *b, mpz_t *p, mpz_t *res)
88 {
89  mpz_t *tmp = mp_new();
90 
91  mp_int_mul(a, b, tmp);
92  mp_int_mod(tmp, p, res);
93  mp_clear_free(tmp);
94 }
95 
96 static mpz_t *
98 {
99  mpz_t *bn = mp_new();
100 
101  mp_int_read_unsigned(bn, n->data, n->bytes);
102 
103  if (!bn)
104  return NULL;
105  if (mp_int_count_bits(bn) != n->bits)
106  {
107  px_debug("mpi_to_bn: bignum conversion failed: mpi=%d, bn=%d",
108  n->bits, mp_int_count_bits(bn));
109  mp_clear_free(bn);
110  return NULL;
111  }
112  return bn;
113 }
114 
115 static PGP_MPI *
117 {
118  int res;
119  PGP_MPI *n;
120  int bytes;
121 
122  res = pgp_mpi_alloc(mp_int_count_bits(bn), &n);
123  if (res < 0)
124  return NULL;
125 
126  bytes = (mp_int_count_bits(bn) + 7) / 8;
127  if (bytes != n->bytes)
128  {
129  px_debug("bn_to_mpi: bignum conversion failed: bn=%d, mpi=%d",
130  bytes, n->bytes);
131  pgp_mpi_free(n);
132  return NULL;
133  }
134  mp_int_to_unsigned(bn, n->data, n->bytes);
135  return n;
136 }
137 
138 /*
139  * Decide the number of bits in the random component k
140  *
141  * It should be in the same range as p for signing (which
142  * is deprecated), but can be much smaller for encrypting.
143  *
144  * Until I research it further, I just mimic gpg behaviour.
145  * It has a special mapping table, for values <= 5120,
146  * above that it uses 'arbitrary high number'. Following
147  * algorithm hovers 10-70 bits above gpg values. And for
148  * larger p, it uses gpg's algorithm.
149  *
150  * The point is - if k gets large, encryption will be
151  * really slow. It does not matter for decryption.
152  */
153 static int
154 decide_k_bits(int p_bits)
155 {
156  if (p_bits <= 5120)
157  return p_bits / 10 + 160;
158  else
159  return (p_bits / 8 + 200) * 3 / 2;
160 }
161 
162 int
164  PGP_MPI **c1_p, PGP_MPI **c2_p)
165 {
166  int res = PXE_PGP_MATH_FAILED;
167  int k_bits;
168  mpz_t *m = mpi_to_bn(_m);
169  mpz_t *p = mpi_to_bn(pk->pub.elg.p);
170  mpz_t *g = mpi_to_bn(pk->pub.elg.g);
171  mpz_t *y = mpi_to_bn(pk->pub.elg.y);
172  mpz_t *k = mp_new();
173  mpz_t *yk = mp_new();
174  mpz_t *c1 = mp_new();
175  mpz_t *c2 = mp_new();
176 
177  if (!m || !p || !g || !y || !k || !yk || !c1 || !c2)
178  goto err;
179 
180  /*
181  * generate k
182  */
183  k_bits = decide_k_bits(mp_int_count_bits(p));
184  res = mp_px_rand(k_bits, k);
185  if (res < 0)
186  return res;
187 
188  /*
189  * c1 = g^k c2 = m * y^k
190  */
191  mp_int_exptmod(g, k, p, c1);
192  mp_int_exptmod(y, k, p, yk);
193  mp_modmul(m, yk, p, c2);
194 
195  /* result */
196  *c1_p = bn_to_mpi(c1);
197  *c2_p = bn_to_mpi(c2);
198  if (*c1_p && *c2_p)
199  res = 0;
200 err:
201  mp_clear_free(c2);
202  mp_clear_free(c1);
203  mp_clear_free(yk);
204  mp_clear_free(k);
205  mp_clear_free(y);
206  mp_clear_free(g);
207  mp_clear_free(p);
208  mp_clear_free(m);
209  return res;
210 }
211 
212 int
214  PGP_MPI **msg_p)
215 {
216  int res = PXE_PGP_MATH_FAILED;
217  mpz_t *c1 = mpi_to_bn(_c1);
218  mpz_t *c2 = mpi_to_bn(_c2);
219  mpz_t *p = mpi_to_bn(pk->pub.elg.p);
220  mpz_t *x = mpi_to_bn(pk->sec.elg.x);
221  mpz_t *c1x = mp_new();
222  mpz_t *div = mp_new();
223  mpz_t *m = mp_new();
224 
225  if (!c1 || !c2 || !p || !x || !c1x || !div || !m)
226  goto err;
227 
228  /*
229  * m = c2 / (c1^x)
230  */
231  mp_int_exptmod(c1, x, p, c1x);
232  mp_int_invmod(c1x, p, div);
233  mp_modmul(c2, div, p, m);
234 
235  /* result */
236  *msg_p = bn_to_mpi(m);
237  if (*msg_p)
238  res = 0;
239 err:
240  mp_clear_free(m);
241  mp_clear_free(div);
242  mp_clear_free(c1x);
243  mp_clear_free(x);
244  mp_clear_free(p);
245  mp_clear_free(c2);
246  mp_clear_free(c1);
247  return res;
248 }
249 
250 int
252 {
253  int res = PXE_PGP_MATH_FAILED;
254  mpz_t *m = mpi_to_bn(_m);
255  mpz_t *e = mpi_to_bn(pk->pub.rsa.e);
256  mpz_t *n = mpi_to_bn(pk->pub.rsa.n);
257  mpz_t *c = mp_new();
258 
259  if (!m || !e || !n || !c)
260  goto err;
261 
262  /*
263  * c = m ^ e
264  */
265  mp_int_exptmod(m, e, n, c);
266 
267  *c_p = bn_to_mpi(c);
268  if (*c_p)
269  res = 0;
270 err:
271  mp_clear_free(c);
272  mp_clear_free(n);
273  mp_clear_free(e);
274  mp_clear_free(m);
275  return res;
276 }
277 
278 int
280 {
281  int res = PXE_PGP_MATH_FAILED;
282  mpz_t *c = mpi_to_bn(_c);
283  mpz_t *d = mpi_to_bn(pk->sec.rsa.d);
284  mpz_t *n = mpi_to_bn(pk->pub.rsa.n);
285  mpz_t *m = mp_new();
286 
287  if (!m || !d || !n || !c)
288  goto err;
289 
290  /*
291  * m = c ^ d
292  */
293  mp_int_exptmod(c, d, n, m);
294 
295  *m_p = bn_to_mpi(m);
296  if (*m_p)
297  res = 0;
298 err:
299  mp_clear_free(m);
300  mp_clear_free(n);
301  mp_clear_free(d);
302  mp_clear_free(c);
303  return res;
304 }
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:357
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:67
int pgp_rsa_encrypt(PGP_PubKey *pk, PGP_MPI *_m, PGP_MPI **c_p)
unsigned int uint32
Definition: c.h:359
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