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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 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.org |
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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_object_identifier.c |
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15 ASN.1 DER, Encode Object Identifier, Tom St Denis |
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16 */ |
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17 |
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18 #ifdef LTC_DER |
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19 /** |
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20 Encode an OID |
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21 @param words The words to encode (upto 32-bits each) |
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22 @param nwords The number of words in the OID |
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23 @param out [out] Destination of OID data |
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24 @param outlen [in/out] The max and resulting size of the OID |
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25 @return CRYPT_OK if successful |
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26 */ |
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27 int der_encode_object_identifier(unsigned long *words, unsigned long nwords, |
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28 unsigned char *out, unsigned long *outlen) |
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29 { |
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30 unsigned long i, x, y, z, t, mask; |
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31 int err; |
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32 |
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33 LTC_ARGCHK(words != NULL); |
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34 LTC_ARGCHK(out != NULL); |
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35 LTC_ARGCHK(outlen != NULL); |
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36 |
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37 /* check length */ |
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38 if ((err = der_length_object_identifier(words, nwords, &x)) != CRYPT_OK) { |
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39 return err; |
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40 } |
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41 if (x > *outlen) { |
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42 return CRYPT_BUFFER_OVERFLOW; |
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43 } |
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44 |
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45 /* compute length to store OID data */ |
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46 z = 1; |
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47 for (y = 2; y < nwords; y++) { |
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48 t = der_object_identifier_bits(words[y]); |
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49 z += t/7 + ((t%7) ? 1 : 0); |
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50 } |
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51 |
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52 /* store header + length */ |
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53 x = 0; |
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54 out[x++] = 0x06; |
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55 if (z < 128) { |
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56 out[x++] = z; |
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57 } else if (z < 256) { |
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58 out[x++] = 0x81; |
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59 out[x++] = z; |
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60 } else if (z < 65536UL) { |
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61 out[x++] = 0x82; |
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62 out[x++] = (z>>8)&255; |
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63 out[x++] = z&255; |
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64 } else { |
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65 return CRYPT_INVALID_ARG; |
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66 } |
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67 |
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68 /* store first byte */ |
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69 out[x++] = words[0] * 40 + words[1]; |
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70 |
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71 for (i = 2; i < nwords; i++) { |
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72 /* store 7 bit words in little endian */ |
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73 t = words[i] & 0xFFFFFFFF; |
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74 if (t) { |
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75 y = x; |
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76 mask = 0; |
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77 while (t) { |
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78 out[x++] = (t & 0x7F) | mask; |
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79 t >>= 7; |
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80 mask |= 0x80; /* upper bit is set on all but the last byte */ |
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81 } |
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82 /* now swap bytes y...x-1 */ |
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83 z = x - 1; |
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84 while (y < z) { |
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85 t = out[y]; out[y] = out[z]; out[z] = t; |
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86 ++y; |
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87 --z; |
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88 } |
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89 } else { |
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90 /* zero word */ |
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91 out[x++] = 0x00; |
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92 } |
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93 } |
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94 |
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95 *outlen = x; |
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96 return CRYPT_OK; |
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97 } |
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98 |
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99 #endif |
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100 |
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101 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/object_identifier/der_encode_object_identifier.c,v $ */ |
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102 /* $Revision: 1.1 $ */ |
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103 /* $Date: 2005/05/16 15:08:11 $ */ |
