Mercurial > dropbear

annotate libtommath/bn_mp_montgomery_reduce.c @ 1629:258b57b208ae

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Fix for issue successfull login of disabled user (#78) This commit introduces fix for scenario: 1. Root login disabled on dropbear 2. PAM authentication model enabled While login as root user, after prompt for password user is being notified about login failrue, but after second attempt of prompt for password within same session, login becames succesfull. Signed-off-by: Pawel Rapkiewicz <[email protected]>
author vincentto13 <33652988+vincentto13@users.noreply.github.com>
date Wed, 20 Mar 2019 15:03:40 +0100
parents 8bba51a55704
children f52919ffd3b1
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 #include <tommath_private.h>
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2 #ifdef BN_MP_MONTGOMERY_REDUCE_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://libtom.org
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16 */
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17
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18 /* computes xR**-1 == x (mod N) via Montgomery Reduction */
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19 int
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20 mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho)
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21 {
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22 int ix, res, digs;
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23 mp_digit mu;
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24
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25 /* can the fast reduction [comba] method be used?
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26 *
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27 * Note that unlike in mul you're safely allowed *less*
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28 * than the available columns [255 per default] since carries
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29 * are fixed up in the inner loop.
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30 */
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31 digs = (n->used * 2) + 1;
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32 if ((digs < MP_WARRAY) &&
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33 (n->used <
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34 (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) {
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35 return fast_mp_montgomery_reduce (x, n, rho);
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36 }
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37
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38 /* grow the input as required */
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39 if (x->alloc < digs) {
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40 if ((res = mp_grow (x, digs)) != MP_OKAY) {
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41 return res;
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42 }
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43 }
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44 x->used = digs;
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45
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46 for (ix = 0; ix < n->used; ix++) {
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47 /* mu = ai * rho mod b
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48 *
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49 * The value of rho must be precalculated via
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50 * montgomery_setup() such that
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51 * it equals -1/n0 mod b this allows the
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52 * following inner loop to reduce the
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53 * input one digit at a time
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54 */
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55 mu = (mp_digit) (((mp_word)x->dp[ix] * (mp_word)rho) & MP_MASK);
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56
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57 /* a = a + mu * m * b**i */
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58 {
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59 int iy;
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60 mp_digit *tmpn, *tmpx, u;
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61 mp_word r;
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62
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63 /* alias for digits of the modulus */
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64 tmpn = n->dp;
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65
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66 /* alias for the digits of x [the input] */
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67 tmpx = x->dp + ix;
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68
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69 /* set the carry to zero */
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70 u = 0;
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71
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72 /* Multiply and add in place */
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73 for (iy = 0; iy < n->used; iy++) {
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74 /* compute product and sum */
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75 r = ((mp_word)mu * (mp_word)*tmpn++) +
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76 (mp_word) u + (mp_word) *tmpx;
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77
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78 /* get carry */
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79 u = (mp_digit)(r >> ((mp_word) DIGIT_BIT));
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80
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81 /* fix digit */
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82 *tmpx++ = (mp_digit)(r & ((mp_word) MP_MASK));
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83 }
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84 /* At this point the ix'th digit of x should be zero */
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85
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86
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87 /* propagate carries upwards as required*/
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88 while (u != 0) {
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89 *tmpx += u;
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90 u = *tmpx >> DIGIT_BIT;
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91 *tmpx++ &= MP_MASK;
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92 }
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93 }
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94 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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95
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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96 /* at this point the n.used'th least
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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97 * significant digits of x are all zero
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
98 * which means we can shift x to the
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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99 * right by n.used digits and the
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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100 * residue is unchanged.
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
101 */
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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102
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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103 /* x = x/b**n.used */
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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104 mp_clamp(x);
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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105 mp_rshd (x, n->used);
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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106
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
107 /* if x >= n then x = x - n */
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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108 if (mp_cmp_mag (x, n) != MP_LT) {
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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109 return s_mp_sub (x, n, x);
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Matt Johnston <matt@ucc.asn.au>
parents:
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110 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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111
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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112 return MP_OKAY;
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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113 }
eed26cff980b propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
Matt Johnston <matt@ucc.asn.au>
parents:
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114 #endif
389
5ff8218bcee9 propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 2af95f00ebd5bb7a28b3817db1218442c935388e)
Matt Johnston <matt@ucc.asn.au>
parents: 284
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115
1470
8bba51a55704 Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents: 1436
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116 /* ref: $Format:%D$ */
8bba51a55704 Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents: 1436
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117 /* git commit: $Format:%H$ */
8bba51a55704 Update to libtommath v1.0.1
Matt Johnston <matt@ucc.asn.au>
parents: 1436
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118 /* commit time: $Format:%ai$ */