90 lines
2.1 KiB
C
90 lines
2.1 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
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*/
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#include "tomcrypt.h"
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/**
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@file der_encode_bit_string.c
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ASN.1 DER, encode a BIT STRING, Tom St Denis
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*/
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#ifdef LTC_DER
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/**
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Store a BIT STRING
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@param in The array of bits to store (one per char)
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@param inlen The number of bits tostore
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@param out [out] The destination for the DER encoded BIT STRING
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@param outlen [in/out] The max size and resulting size of the DER BIT STRING
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@return CRYPT_OK if successful
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*/
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int der_encode_bit_string(const unsigned char *in, unsigned long inlen,
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unsigned char *out, unsigned long *outlen)
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{
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unsigned long len, x, y;
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unsigned char buf;
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int err;
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LTC_ARGCHK(in != NULL);
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LTC_ARGCHK(out != NULL);
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LTC_ARGCHK(outlen != NULL);
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/* avoid overflows */
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if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) {
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return err;
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}
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if (len > *outlen) {
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*outlen = len;
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return CRYPT_BUFFER_OVERFLOW;
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}
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/* store header (include bit padding count in length) */
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x = 0;
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y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1;
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out[x++] = 0x03;
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if (y < 128) {
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out[x++] = (unsigned char)y;
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} else if (y < 256) {
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out[x++] = 0x81;
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out[x++] = (unsigned char)y;
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} else if (y < 65536) {
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out[x++] = 0x82;
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out[x++] = (unsigned char)((y>>8)&255);
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out[x++] = (unsigned char)(y&255);
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}
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/* store number of zero padding bits */
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out[x++] = (unsigned char)((8 - inlen) & 7);
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/* store the bits in big endian format */
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for (y = buf = 0; y < inlen; y++) {
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buf |= (in[y] ? 1 : 0) << (7 - (y & 7));
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if ((y & 7) == 7) {
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out[x++] = buf;
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buf = 0;
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}
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}
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/* store last byte */
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if (inlen & 7) {
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out[x++] = buf;
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}
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*outlen = x;
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return CRYPT_OK;
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}
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#endif
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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