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cdec9cb5 DK |
1 | /* mpicoder.c - Coder for the external representation of MPIs |
2 | * Copyright (C) 1998, 1999 Free Software Foundation, Inc. | |
3 | * | |
4 | * This file is part of GnuPG. | |
5 | * | |
6 | * GnuPG is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * GnuPG is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program; if not, write to the Free Software | |
18 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA | |
19 | */ | |
20 | ||
21 | #include "mpi-internal.h" | |
22 | ||
cdec9cb5 DK |
23 | #define MAX_EXTERN_MPI_BITS 16384 |
24 | ||
cdec9cb5 DK |
25 | MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread) |
26 | { | |
27 | const uint8_t *buffer = xbuffer; | |
28 | int i, j; | |
29 | unsigned nbits, nbytes, nlimbs, nread = 0; | |
30 | mpi_limb_t a; | |
3cccd154 | 31 | MPI val = NULL; |
cdec9cb5 DK |
32 | |
33 | if (*ret_nread < 2) | |
34 | goto leave; | |
35 | nbits = buffer[0] << 8 | buffer[1]; | |
36 | ||
37 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
38 | pr_info("MPI: mpi too large (%u bits)\n", nbits); | |
39 | goto leave; | |
40 | } | |
41 | buffer += 2; | |
42 | nread = 2; | |
43 | ||
44 | nbytes = (nbits + 7) / 8; | |
45 | nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB; | |
46 | val = mpi_alloc(nlimbs); | |
47 | if (!val) | |
3cccd154 | 48 | return NULL; |
cdec9cb5 DK |
49 | i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; |
50 | i %= BYTES_PER_MPI_LIMB; | |
51 | val->nbits = nbits; | |
52 | j = val->nlimbs = nlimbs; | |
53 | val->sign = 0; | |
54 | for (; j > 0; j--) { | |
55 | a = 0; | |
56 | for (; i < BYTES_PER_MPI_LIMB; i++) { | |
57 | if (++nread > *ret_nread) { | |
58 | printk | |
59 | ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n", | |
60 | nread, *ret_nread); | |
61 | goto leave; | |
62 | } | |
63 | a <<= 8; | |
64 | a |= *buffer++; | |
65 | } | |
66 | i = 0; | |
67 | val->d[j - 1] = a; | |
68 | } | |
69 | ||
70 | leave: | |
71 | *ret_nread = nread; | |
72 | return val; | |
73 | } | |
74 | EXPORT_SYMBOL_GPL(mpi_read_from_buffer); | |
75 | ||
cdec9cb5 DK |
76 | /**************** |
77 | * Return an allocated buffer with the MPI (msb first). | |
78 | * NBYTES receives the length of this buffer. Caller must free the | |
79 | * return string (This function does return a 0 byte buffer with NBYTES | |
80 | * set to zero if the value of A is zero. If sign is not NULL, it will | |
81 | * be set to the sign of the A. | |
82 | */ | |
83 | void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign) | |
84 | { | |
85 | uint8_t *p, *buffer; | |
86 | mpi_limb_t alimb; | |
87 | int i; | |
88 | unsigned int n; | |
89 | ||
90 | if (sign) | |
91 | *sign = a->sign; | |
92 | *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB; | |
93 | if (!n) | |
94 | n++; /* avoid zero length allocation */ | |
95 | p = buffer = kmalloc(n, GFP_KERNEL); | |
4bf1924c DH |
96 | if (!p) |
97 | return NULL; | |
cdec9cb5 DK |
98 | |
99 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
100 | alimb = a->d[i]; | |
101 | #if BYTES_PER_MPI_LIMB == 4 | |
102 | *p++ = alimb >> 24; | |
103 | *p++ = alimb >> 16; | |
104 | *p++ = alimb >> 8; | |
105 | *p++ = alimb; | |
106 | #elif BYTES_PER_MPI_LIMB == 8 | |
107 | *p++ = alimb >> 56; | |
108 | *p++ = alimb >> 48; | |
109 | *p++ = alimb >> 40; | |
110 | *p++ = alimb >> 32; | |
111 | *p++ = alimb >> 24; | |
112 | *p++ = alimb >> 16; | |
113 | *p++ = alimb >> 8; | |
114 | *p++ = alimb; | |
115 | #else | |
116 | #error please implement for this limb size. | |
117 | #endif | |
118 | } | |
119 | ||
120 | /* this is sub-optimal but we need to do the shift operation | |
121 | * because the caller has to free the returned buffer */ | |
122 | for (p = buffer; !*p && *nbytes; p++, --*nbytes) | |
123 | ; | |
124 | if (p != buffer) | |
125 | memmove(buffer, p, *nbytes); | |
126 | ||
127 | return buffer; | |
128 | } | |
129 | EXPORT_SYMBOL_GPL(mpi_get_buffer); | |
130 | ||
131 | /**************** | |
132 | * Use BUFFER to update MPI. | |
133 | */ | |
134 | int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign) | |
135 | { | |
136 | const uint8_t *buffer = xbuffer, *p; | |
137 | mpi_limb_t alimb; | |
138 | int nlimbs; | |
139 | int i; | |
140 | ||
141 | nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB; | |
142 | if (RESIZE_IF_NEEDED(a, nlimbs) < 0) | |
143 | return -ENOMEM; | |
144 | a->sign = sign; | |
145 | ||
146 | for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) { | |
147 | #if BYTES_PER_MPI_LIMB == 4 | |
148 | alimb = (mpi_limb_t) *p--; | |
149 | alimb |= (mpi_limb_t) *p-- << 8; | |
150 | alimb |= (mpi_limb_t) *p-- << 16; | |
151 | alimb |= (mpi_limb_t) *p-- << 24; | |
152 | #elif BYTES_PER_MPI_LIMB == 8 | |
153 | alimb = (mpi_limb_t) *p--; | |
154 | alimb |= (mpi_limb_t) *p-- << 8; | |
155 | alimb |= (mpi_limb_t) *p-- << 16; | |
156 | alimb |= (mpi_limb_t) *p-- << 24; | |
157 | alimb |= (mpi_limb_t) *p-- << 32; | |
158 | alimb |= (mpi_limb_t) *p-- << 40; | |
159 | alimb |= (mpi_limb_t) *p-- << 48; | |
160 | alimb |= (mpi_limb_t) *p-- << 56; | |
161 | #else | |
162 | #error please implement for this limb size. | |
163 | #endif | |
164 | a->d[i++] = alimb; | |
165 | } | |
166 | if (p >= buffer) { | |
167 | #if BYTES_PER_MPI_LIMB == 4 | |
168 | alimb = *p--; | |
169 | if (p >= buffer) | |
170 | alimb |= (mpi_limb_t) *p-- << 8; | |
171 | if (p >= buffer) | |
172 | alimb |= (mpi_limb_t) *p-- << 16; | |
173 | if (p >= buffer) | |
174 | alimb |= (mpi_limb_t) *p-- << 24; | |
175 | #elif BYTES_PER_MPI_LIMB == 8 | |
176 | alimb = (mpi_limb_t) *p--; | |
177 | if (p >= buffer) | |
178 | alimb |= (mpi_limb_t) *p-- << 8; | |
179 | if (p >= buffer) | |
180 | alimb |= (mpi_limb_t) *p-- << 16; | |
181 | if (p >= buffer) | |
182 | alimb |= (mpi_limb_t) *p-- << 24; | |
183 | if (p >= buffer) | |
184 | alimb |= (mpi_limb_t) *p-- << 32; | |
185 | if (p >= buffer) | |
186 | alimb |= (mpi_limb_t) *p-- << 40; | |
187 | if (p >= buffer) | |
188 | alimb |= (mpi_limb_t) *p-- << 48; | |
189 | if (p >= buffer) | |
190 | alimb |= (mpi_limb_t) *p-- << 56; | |
191 | #else | |
192 | #error please implement for this limb size. | |
193 | #endif | |
194 | a->d[i++] = alimb; | |
195 | } | |
196 | a->nlimbs = i; | |
197 | ||
198 | if (i != nlimbs) { | |
199 | pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i, | |
200 | nlimbs); | |
201 | BUG(); | |
202 | } | |
203 | return 0; | |
204 | } | |
205 | EXPORT_SYMBOL_GPL(mpi_set_buffer); |