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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_length_object_identifier.c |
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15 ASN.1 DER, get length of 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 unsigned long der_object_identifier_bits(unsigned long x) |
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21 { |
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22 unsigned long c; |
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23 x &= 0xFFFFFFFF; |
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24 c = 0; |
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25 while (x) { |
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26 ++c; |
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27 x >>= 1; |
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28 } |
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29 return c; |
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30 } |
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31 |
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32 |
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33 /** |
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34 Gets length of DER encoding of Object Identifier |
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35 @param nwords The number of OID words |
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36 @param words The actual OID words to get the size of |
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37 @param outlen [out] The length of the DER encoding for the given string |
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38 @return CRYPT_OK if successful |
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39 */ |
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40 int der_length_object_identifier(unsigned long *words, unsigned long nwords, unsigned long *outlen) |
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41 { |
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42 unsigned long y, z, t; |
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43 |
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44 LTC_ARGCHK(words != NULL); |
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45 LTC_ARGCHK(outlen != NULL); |
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46 |
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47 |
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48 /* must be >= 2 words */ |
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49 if (nwords < 2) { |
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50 return CRYPT_INVALID_ARG; |
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51 } |
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52 |
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53 /* word1 = 0,1,2 and word2 0..39 */ |
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54 if (words[0] > 2 || words[1] > 39) { |
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55 return CRYPT_INVALID_ARG; |
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56 } |
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57 |
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58 /* leading byte of first two words */ |
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59 z = 1; |
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60 for (y = 2; y < nwords; y++) { |
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61 t = der_object_identifier_bits(words[y]); |
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62 z += t/7 + ((t%7) ? 1 : 0); |
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63 } |
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64 |
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65 /* now depending on the length our length encoding changes */ |
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66 if (z < 128) { |
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67 z += 2; |
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68 } else if (z < 256) { |
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69 z += 3; |
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70 } else if (z < 65536UL) { |
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71 z += 4; |
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72 } else { |
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73 return CRYPT_INVALID_ARG; |
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74 } |
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75 |
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76 *outlen = z; |
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77 return CRYPT_OK; |
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78 } |
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79 |
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80 #endif |
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81 |
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82 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/object_identifier/der_length_object_identifier.c,v $ */ |
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83 /* $Revision: 1.1 $ */ |
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84 /* $Date: 2005/05/16 15:08:11 $ */ |
