Mercurial > dropbear
annotate src/pk/asn1/der/integer/der_encode_integer.c @ 390:d8e44bef7917 libtomcrypt-dropbear
Replace // with /* */
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 11 Jan 2007 04:28:09 +0000 |
parents | d5faf4814ddb |
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rev | line source |
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280
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Re-import libtomcrypt 1.05 for cleaner propagating.
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
380 | 9 * Tom St Denis, [email protected], http://libtomcrypt.com |
280
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10 */ |
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11 #include "tomcrypt.h" |
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12 |
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13 /** |
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14 @file der_encode_integer.c |
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15 ASN.1 DER, encode an integer, Tom St Denis |
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16 */ |
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17 |
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18 |
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19 #ifdef LTC_DER |
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20 |
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21 /* Exports a positive bignum as DER format (upto 2^32 bytes in size) */ |
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22 /** |
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23 Store a mp_int integer |
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24 @param num The first mp_int to encode |
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25 @param out [out] The destination for the DER encoded integers |
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26 @param outlen [in/out] The max size and resulting size of the DER encoded integers |
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27 @return CRYPT_OK if successful |
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28 */ |
380 | 29 int der_encode_integer(void *num, unsigned char *out, unsigned long *outlen) |
280
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30 { |
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31 unsigned long tmplen, y; |
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32 int err, leading_zero; |
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33 |
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34 LTC_ARGCHK(num != NULL); |
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35 LTC_ARGCHK(out != NULL); |
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36 LTC_ARGCHK(outlen != NULL); |
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37 |
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38 /* find out how big this will be */ |
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39 if ((err = der_length_integer(num, &tmplen)) != CRYPT_OK) { |
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40 return err; |
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41 } |
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42 |
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43 if (*outlen < tmplen) { |
380 | 44 *outlen = tmplen; |
280
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45 return CRYPT_BUFFER_OVERFLOW; |
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46 } |
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47 |
380 | 48 if (mp_cmp_d(num, 0) != LTC_MP_LT) { |
280
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49 /* we only need a leading zero if the msb of the first byte is one */ |
380 | 50 if ((mp_count_bits(num) & 7) == 0 || mp_iszero(num) == LTC_MP_YES) { |
280
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51 leading_zero = 1; |
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52 } else { |
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53 leading_zero = 0; |
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54 } |
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55 |
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56 /* get length of num in bytes (plus 1 since we force the msbyte to zero) */ |
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57 y = mp_unsigned_bin_size(num) + leading_zero; |
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58 } else { |
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59 leading_zero = 0; |
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60 y = mp_count_bits(num); |
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61 y = y + (8 - (y & 7)); |
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62 y = y >> 3; |
380 | 63 if (((mp_cnt_lsb(num)+1)==mp_count_bits(num)) && ((mp_count_bits(num)&7)==0)) --y; |
280
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64 } |
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65 |
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66 /* now store initial data */ |
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67 *out++ = 0x02; |
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68 if (y < 128) { |
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69 /* short form */ |
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70 *out++ = (unsigned char)y; |
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71 } else if (y < 256) { |
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72 *out++ = 0x81; |
380 | 73 *out++ = (unsigned char)y; |
280
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74 } else if (y < 65536UL) { |
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75 *out++ = 0x82; |
380 | 76 *out++ = (unsigned char)((y>>8)&255); |
77 *out++ = (unsigned char)y; | |
280
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78 } else if (y < 16777216UL) { |
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79 *out++ = 0x83; |
380 | 80 *out++ = (unsigned char)((y>>16)&255); |
81 *out++ = (unsigned char)((y>>8)&255); | |
82 *out++ = (unsigned char)y; | |
280
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83 } else { |
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84 return CRYPT_INVALID_ARG; |
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85 } |
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86 |
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87 /* now store msbyte of zero if num is non-zero */ |
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88 if (leading_zero) { |
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89 *out++ = 0x00; |
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90 } |
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91 |
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92 /* if it's not zero store it as big endian */ |
380 | 93 if (mp_cmp_d(num, 0) == LTC_MP_GT) { |
280
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94 /* now store the mpint */ |
380 | 95 if ((err = mp_to_unsigned_bin(num, out)) != CRYPT_OK) { |
96 return err; | |
280
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97 } |
380 | 98 } else if (mp_iszero(num) != LTC_MP_YES) { |
99 void *tmp; | |
100 | |
280
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101 /* negative */ |
380 | 102 if (mp_init(&tmp) != CRYPT_OK) { |
280
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103 return CRYPT_MEM; |
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104 } |
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105 |
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106 /* 2^roundup and subtract */ |
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107 y = mp_count_bits(num); |
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108 y = y + (8 - (y & 7)); |
380 | 109 if (((mp_cnt_lsb(num)+1)==mp_count_bits(num)) && ((mp_count_bits(num)&7)==0)) y -= 8; |
110 if (mp_2expt(tmp, y) != CRYPT_OK || mp_add(tmp, num, tmp) != CRYPT_OK) { | |
111 mp_clear(tmp); | |
280
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112 return CRYPT_MEM; |
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113 } |
380 | 114 if ((err = mp_to_unsigned_bin(tmp, out)) != CRYPT_OK) { |
115 mp_clear(tmp); | |
116 return err; | |
280
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117 } |
380 | 118 mp_clear(tmp); |
280
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119 } |
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120 |
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121 /* we good */ |
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122 *outlen = tmplen; |
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123 return CRYPT_OK; |
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124 } |
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125 |
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126 #endif |
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127 |
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128 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c,v $ */ |
380 | 129 /* $Revision: 1.8 $ */ |
130 /* $Date: 2006/12/04 21:34:03 $ */ |