diff options
Diffstat (limited to 'core/lib/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c')
| -rw-r--r-- | core/lib/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/core/lib/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c b/core/lib/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c new file mode 100644 index 0000000..466522b --- /dev/null +++ b/core/lib/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c @@ -0,0 +1,157 @@ +/* + * Copyright (c) 2001-2007, Tom St Denis + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +/* LibTomCrypt, modular cryptographic library -- Tom St Denis + * + * LibTomCrypt is a library that provides various cryptographic + * algorithms in a highly modular and flexible manner. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@gmail.com, http://libtom.org + */ +#include "tomcrypt.h" + +/** + @file der_encode_integer.c + ASN.1 DER, encode an integer, Tom St Denis +*/ + + +#ifdef LTC_DER + +/* Exports a positive bignum as DER format (upto 2^32 bytes in size) */ +/** + Store a mp_int integer + @param num The first mp_int to encode + @param out [out] The destination for the DER encoded integers + @param outlen [in/out] The max size and resulting size of the DER encoded integers + @return CRYPT_OK if successful +*/ +int der_encode_integer(void *num, unsigned char *out, unsigned long *outlen) +{ + unsigned long tmplen, y; + int err, leading_zero; + + LTC_ARGCHK(num != NULL); + LTC_ARGCHK(out != NULL); + LTC_ARGCHK(outlen != NULL); + + /* find out how big this will be */ + if ((err = der_length_integer(num, &tmplen)) != CRYPT_OK) { + return err; + } + + if (*outlen < tmplen) { + *outlen = tmplen; + return CRYPT_BUFFER_OVERFLOW; + } + + if (mp_cmp_d(num, 0) != LTC_MP_LT) { + /* we only need a leading zero if the msb of the first byte is one */ + if ((mp_count_bits(num) & 7) == 0 || mp_iszero(num) == LTC_MP_YES) { + leading_zero = 1; + } else { + leading_zero = 0; + } + + /* get length of num in bytes (plus 1 since we force the msbyte to zero) */ + y = mp_unsigned_bin_size(num) + leading_zero; + } else { + leading_zero = 0; + y = mp_count_bits(num); + y = y + (8 - (y & 7)); + y = y >> 3; + if (((mp_cnt_lsb(num)+1)==mp_count_bits(num)) && ((mp_count_bits(num)&7)==0)) --y; + } + + /* now store initial data */ + *out++ = 0x02; + if (y < 128) { + /* short form */ + *out++ = (unsigned char)y; + } else if (y < 256) { + *out++ = 0x81; + *out++ = (unsigned char)y; + } else if (y < 65536UL) { + *out++ = 0x82; + *out++ = (unsigned char)((y>>8)&255); + *out++ = (unsigned char)y; + } else if (y < 16777216UL) { + *out++ = 0x83; + *out++ = (unsigned char)((y>>16)&255); + *out++ = (unsigned char)((y>>8)&255); + *out++ = (unsigned char)y; + } else { + return CRYPT_INVALID_ARG; + } + + /* now store msbyte of zero if num is non-zero */ + if (leading_zero) { + *out++ = 0x00; + } + + /* if it's not zero store it as big endian */ + if (mp_cmp_d(num, 0) == LTC_MP_GT) { + /* now store the mpint */ + if ((err = mp_to_unsigned_bin(num, out)) != CRYPT_OK) { + return err; + } + } else if (mp_iszero(num) != LTC_MP_YES) { + void *tmp; + + /* negative */ + if (mp_init(&tmp) != CRYPT_OK) { + return CRYPT_MEM; + } + + /* 2^roundup and subtract */ + y = mp_count_bits(num); + y = y + (8 - (y & 7)); + if (((mp_cnt_lsb(num)+1)==mp_count_bits(num)) && ((mp_count_bits(num)&7)==0)) y -= 8; + if (mp_2expt(tmp, y) != CRYPT_OK || mp_add(tmp, num, tmp) != CRYPT_OK) { + mp_clear(tmp); + return CRYPT_MEM; + } + if ((err = mp_to_unsigned_bin(tmp, out)) != CRYPT_OK) { + mp_clear(tmp); + return err; + } + mp_clear(tmp); + } + + /* we good */ + *outlen = tmplen; + return CRYPT_OK; +} + +#endif + +/* $Source$ */ +/* $Revision$ */ +/* $Date$ */ |