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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_decode_bit_string.c |
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15 ASN.1 DER, encode a BIT STRING, 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 /** |
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22 Store a BIT STRING |
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23 @param in The DER encoded BIT STRING |
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24 @param inlen The size of the DER BIT STRING |
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25 @param out [out] The array of bits stored (one per char) |
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26 @param outlen [in/out] The number of bits stored |
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27 @return CRYPT_OK if successful |
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28 */ |
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29 int der_decode_bit_string(const unsigned char *in, unsigned long inlen, |
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30 unsigned char *out, unsigned long *outlen) |
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31 { |
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32 unsigned long dlen, blen, x, y; |
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33 |
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34 LTC_ARGCHK(in != 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 /* packet must be at least 4 bytes */ |
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39 if (inlen < 4) { |
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40 return CRYPT_INVALID_ARG; |
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41 } |
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42 |
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43 /* check for 0x03 */ |
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44 if ((in[0]&0x1F) != 0x03) { |
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45 return CRYPT_INVALID_PACKET; |
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46 } |
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47 |
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48 /* offset in the data */ |
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49 x = 1; |
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50 |
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51 /* get the length of the data */ |
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52 if (in[x] & 0x80) { |
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53 /* long format get number of length bytes */ |
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54 y = in[x++] & 127; |
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55 |
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56 /* invalid if 0 or > 2 */ |
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57 if (y == 0 || y > 2) { |
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58 return CRYPT_INVALID_PACKET; |
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59 } |
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60 |
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61 /* read the data len */ |
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62 dlen = 0; |
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63 while (y--) { |
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64 dlen = (dlen << 8) | (unsigned long)in[x++]; |
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65 } |
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66 } else { |
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67 /* short format */ |
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68 dlen = in[x++] & 127; |
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69 } |
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70 |
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71 /* is the data len too long or too short? */ |
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72 if ((dlen == 0) || (dlen + x > inlen)) { |
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73 return CRYPT_INVALID_PACKET; |
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74 } |
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75 |
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76 /* get padding count */ |
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77 blen = ((dlen - 1) << 3) - (in[x++] & 7); |
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78 |
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79 /* too many bits? */ |
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80 if (blen > *outlen) { |
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81 return CRYPT_BUFFER_OVERFLOW; |
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82 } |
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83 |
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84 /* decode/store the bits */ |
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85 for (y = 0; y < blen; y++) { |
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86 out[y] = (in[x] & (1 << (7 - (y & 7)))) ? 1 : 0; |
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87 if ((y & 7) == 7) { |
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88 ++x; |
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89 } |
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90 } |
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91 |
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92 /* we done */ |
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93 *outlen = blen; |
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94 return CRYPT_OK; |
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95 } |
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96 |
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97 #endif |
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98 |
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99 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_decode_bit_string.c,v $ */ |
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100 /* $Revision: 1.1 $ */ |
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101 /* $Date: 2005/05/16 15:08:11 $ */ |
