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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_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 array of bits to store (one per char) |
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24 @param inlen The number of bits tostore |
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25 @param out [out] The destination for the DER encoded BIT STRING |
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26 @param outlen [in/out] The max size and resulting size of the DER BIT STRING |
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27 @return CRYPT_OK if successful |
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28 */ |
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29 int der_encode_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 len, x, y, buf; |
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33 int err; |
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34 |
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35 LTC_ARGCHK(in != NULL); |
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36 LTC_ARGCHK(out != NULL); |
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37 LTC_ARGCHK(outlen != NULL); |
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38 |
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39 /* avoid overflows */ |
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40 if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) { |
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41 return err; |
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42 } |
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43 |
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44 if (len > *outlen) { |
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45 return CRYPT_BUFFER_OVERFLOW; |
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46 } |
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47 |
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48 /* store header (include bit padding count in length) */ |
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49 x = 0; |
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50 y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1; |
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51 |
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52 out[x++] = 0x03; |
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53 if (y < 128) { |
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54 out[x++] = y; |
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55 } else if (y < 256) { |
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56 out[x++] = 0x81; |
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57 out[x++] = y; |
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58 } else if (y < 65536) { |
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59 out[x++] = 0x82; |
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60 out[x++] = (y>>8)&255; |
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61 out[x++] = y&255; |
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62 } |
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63 |
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64 /* store number of zero padding bits */ |
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65 out[x++] = (8 - inlen) & 7; |
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66 |
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67 /* store the bits in big endian format */ |
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68 for (y = buf = 0; y < inlen; y++) { |
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69 buf |= (in[y] ? 1 : 0) << (7 - (y & 7)); |
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70 if ((y & 7) == 7) { |
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71 out[x++] = buf; |
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72 buf = 0; |
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73 } |
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74 } |
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75 /* store last byte */ |
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76 if (inlen & 7) { |
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77 out[x++] = buf; |
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78 } |
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79 *outlen = x; |
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80 return CRYPT_OK; |
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81 } |
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82 |
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83 #endif |
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84 |
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85 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_encode_bit_string.c,v $ */ |
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86 /* $Revision: 1.1 $ */ |
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87 /* $Date: 2005/05/16 15:08:11 $ */ |
