1 /* mpi-add.c - MPI functions 1 /* mpi-add.c - MPI functions
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002, 2 * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3 * 2003 Free Software Foundation 3 * 2003 Free Software Foundation, Inc.
4 * 4 *
5 * This file is part of Libgcrypt. 5 * This file is part of Libgcrypt.
6 * 6 *
7 * Note: This code is heavily based on the GNU 7 * Note: This code is heavily based on the GNU MP Library.
8 * Actually it's the same code with only 8 * Actually it's the same code with only minor changes in the
9 * way the data is stored; this is to su 9 * way the data is stored; this is to support the abstraction
10 * of an optional secure memory allocati 10 * of an optional secure memory allocation which may be used
11 * to avoid revealing of sensitive data 11 * to avoid revealing of sensitive data due to paging etc.
12 */ 12 */
13 13
14 #include "mpi-internal.h" 14 #include "mpi-internal.h"
15 15
16 int mpi_add(MPI w, MPI u, MPI v) 16 int mpi_add(MPI w, MPI u, MPI v)
17 { 17 {
18 mpi_ptr_t wp, up, vp; 18 mpi_ptr_t wp, up, vp;
19 mpi_size_t usize, vsize, wsize; 19 mpi_size_t usize, vsize, wsize;
20 int usign, vsign, wsign; 20 int usign, vsign, wsign;
21 int err; 21 int err;
22 22
23 if (u->nlimbs < v->nlimbs) { /* Swap U 23 if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
24 usize = v->nlimbs; 24 usize = v->nlimbs;
25 usign = v->sign; 25 usign = v->sign;
26 vsize = u->nlimbs; 26 vsize = u->nlimbs;
27 vsign = u->sign; 27 vsign = u->sign;
28 wsize = usize + 1; 28 wsize = usize + 1;
29 err = RESIZE_IF_NEEDED(w, wsiz 29 err = RESIZE_IF_NEEDED(w, wsize);
30 if (err) 30 if (err)
31 return err; 31 return err;
32 /* These must be after realloc 32 /* These must be after realloc (u or v may be the same as w). */
33 up = v->d; 33 up = v->d;
34 vp = u->d; 34 vp = u->d;
35 } else { 35 } else {
36 usize = u->nlimbs; 36 usize = u->nlimbs;
37 usign = u->sign; 37 usign = u->sign;
38 vsize = v->nlimbs; 38 vsize = v->nlimbs;
39 vsign = v->sign; 39 vsign = v->sign;
40 wsize = usize + 1; 40 wsize = usize + 1;
41 err = RESIZE_IF_NEEDED(w, wsiz 41 err = RESIZE_IF_NEEDED(w, wsize);
42 if (err) 42 if (err)
43 return err; 43 return err;
44 /* These must be after realloc 44 /* These must be after realloc (u or v may be the same as w). */
45 up = u->d; 45 up = u->d;
46 vp = v->d; 46 vp = v->d;
47 } 47 }
48 wp = w->d; 48 wp = w->d;
49 wsign = 0; 49 wsign = 0;
50 50
51 if (!vsize) { /* simple */ 51 if (!vsize) { /* simple */
52 MPN_COPY(wp, up, usize); 52 MPN_COPY(wp, up, usize);
53 wsize = usize; 53 wsize = usize;
54 wsign = usign; 54 wsign = usign;
55 } else if (usign != vsign) { /* differ 55 } else if (usign != vsign) { /* different sign */
56 /* This test is right since US 56 /* This test is right since USIZE >= VSIZE */
57 if (usize != vsize) { 57 if (usize != vsize) {
58 mpihelp_sub(wp, up, us 58 mpihelp_sub(wp, up, usize, vp, vsize);
59 wsize = usize; 59 wsize = usize;
60 MPN_NORMALIZE(wp, wsiz 60 MPN_NORMALIZE(wp, wsize);
61 wsign = usign; 61 wsign = usign;
62 } else if (mpihelp_cmp(up, vp, 62 } else if (mpihelp_cmp(up, vp, usize) < 0) {
63 mpihelp_sub_n(wp, vp, 63 mpihelp_sub_n(wp, vp, up, usize);
64 wsize = usize; 64 wsize = usize;
65 MPN_NORMALIZE(wp, wsiz 65 MPN_NORMALIZE(wp, wsize);
66 if (!usign) 66 if (!usign)
67 wsign = 1; 67 wsign = 1;
68 } else { 68 } else {
69 mpihelp_sub_n(wp, up, 69 mpihelp_sub_n(wp, up, vp, usize);
70 wsize = usize; 70 wsize = usize;
71 MPN_NORMALIZE(wp, wsiz 71 MPN_NORMALIZE(wp, wsize);
72 if (usign) 72 if (usign)
73 wsign = 1; 73 wsign = 1;
74 } 74 }
75 } else { /* U and V have same sign. Ad 75 } else { /* U and V have same sign. Add them. */
76 mpi_limb_t cy = mpihelp_add(wp 76 mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);
77 wp[usize] = cy; 77 wp[usize] = cy;
78 wsize = usize + cy; 78 wsize = usize + cy;
79 if (usign) 79 if (usign)
80 wsign = 1; 80 wsign = 1;
81 } 81 }
82 82
83 w->nlimbs = wsize; 83 w->nlimbs = wsize;
84 w->sign = wsign; 84 w->sign = wsign;
85 return 0; 85 return 0;
86 } 86 }
87 EXPORT_SYMBOL_GPL(mpi_add); 87 EXPORT_SYMBOL_GPL(mpi_add);
88 88
89 int mpi_sub(MPI w, MPI u, MPI v) 89 int mpi_sub(MPI w, MPI u, MPI v)
90 { 90 {
91 int err; 91 int err;
92 MPI vv; 92 MPI vv;
93 93
94 vv = mpi_copy(v); 94 vv = mpi_copy(v);
95 if (!vv) 95 if (!vv)
96 return -ENOMEM; 96 return -ENOMEM;
97 97
98 vv->sign = !vv->sign; 98 vv->sign = !vv->sign;
99 err = mpi_add(w, u, vv); 99 err = mpi_add(w, u, vv);
100 mpi_free(vv); 100 mpi_free(vv);
101 101
102 return err; 102 return err;
103 } 103 }
104 EXPORT_SYMBOL_GPL(mpi_sub); 104 EXPORT_SYMBOL_GPL(mpi_sub);
105 105
106 int mpi_addm(MPI w, MPI u, MPI v, MPI m) 106 int mpi_addm(MPI w, MPI u, MPI v, MPI m)
107 { 107 {
108 return mpi_add(w, u, v) ?: 108 return mpi_add(w, u, v) ?:
109 mpi_mod(w, w, m); 109 mpi_mod(w, w, m);
110 } 110 }
111 EXPORT_SYMBOL_GPL(mpi_addm); 111 EXPORT_SYMBOL_GPL(mpi_addm);
112 112
113 int mpi_subm(MPI w, MPI u, MPI v, MPI m) 113 int mpi_subm(MPI w, MPI u, MPI v, MPI m)
114 { 114 {
115 return mpi_sub(w, u, v) ?: 115 return mpi_sub(w, u, v) ?:
116 mpi_mod(w, w, m); 116 mpi_mod(w, w, m);
117 } 117 }
118 EXPORT_SYMBOL_GPL(mpi_subm); 118 EXPORT_SYMBOL_GPL(mpi_subm);
119 119
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