annotate libtomcrypt/src/pk/asn1/der/bit/der_encode_raw_bit_string.c @ 1646:6d1bbe7d5fa5 DROPBEAR_2019.77

2019.77
author Matt Johnston <matt@ucc.asn.au>
date Sat, 23 Mar 2019 21:46:29 +0800
parents 6dba84798cd5
children
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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 #include "tomcrypt.h"
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10
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11 /**
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12 @file der_encode_bit_string.c
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13 ASN.1 DER, encode a BIT STRING, Tom St Denis
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14 */
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15
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16
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17 #ifdef LTC_DER
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18
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19 #define getbit(n, k) (((n) & ( 1 << (k) )) >> (k))
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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 (8 per char)
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24 @param inlen The number of bits to store
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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_raw_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;
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33 unsigned char buf;
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34 int err;
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35
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36 LTC_ARGCHK(in != NULL);
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37 LTC_ARGCHK(out != NULL);
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38 LTC_ARGCHK(outlen != NULL);
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39
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40 /* avoid overflows */
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41 if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) {
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42 return err;
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43 }
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44
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45 if (len > *outlen) {
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46 *outlen = len;
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47 return CRYPT_BUFFER_OVERFLOW;
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48 }
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49
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50 /* store header (include bit padding count in length) */
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51 x = 0;
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52 y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1;
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53
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54 out[x++] = 0x03;
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55 if (y < 128) {
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56 out[x++] = (unsigned char)y;
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57 } else if (y < 256) {
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58 out[x++] = 0x81;
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59 out[x++] = (unsigned char)y;
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60 } else if (y < 65536) {
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61 out[x++] = 0x82;
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62 out[x++] = (unsigned char)((y>>8)&255);
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63 out[x++] = (unsigned char)(y&255);
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64 }
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65
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66 /* store number of zero padding bits */
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67 out[x++] = (unsigned char)((8 - inlen) & 7);
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68
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69 /* store the bits in big endian format */
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70 for (y = buf = 0; y < inlen; y++) {
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71 buf |= (getbit(in[y/8],7-y%8)?1:0) << (7 - (y & 7));
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72 if ((y & 7) == 7) {
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73 out[x++] = buf;
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74 buf = 0;
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75 }
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76 }
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77 /* store last byte */
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78 if (inlen & 7) {
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79 out[x++] = buf;
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80 }
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81
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82 *outlen = x;
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83 return CRYPT_OK;
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84 }
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85
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86 #endif
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87
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88 /* ref: $Format:%D$ */
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89 /* git commit: $Format:%H$ */
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90 /* commit time: $Format:%ai$ */