diff options
Diffstat (limited to 'src/libstrongswan/crypto/mgf1/mgf1_bitspender.c')
| -rw-r--r-- | src/libstrongswan/crypto/mgf1/mgf1_bitspender.c | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/src/libstrongswan/crypto/mgf1/mgf1_bitspender.c b/src/libstrongswan/crypto/mgf1/mgf1_bitspender.c new file mode 100644 index 000000000..ef0a2bd01 --- /dev/null +++ b/src/libstrongswan/crypto/mgf1/mgf1_bitspender.c @@ -0,0 +1,208 @@ +/* + * Copyright (C) 2014 Andreas Steffen + * HSR Hochschule fuer Technik Rapperswil + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * for more details. + */ + +#include "mgf1_bitspender.h" + +#include <crypto/mgf1/mgf1.h> + +typedef struct private_mgf1_bitspender_t private_mgf1_bitspender_t; + +/** + * Private data structure for mgf1_bitspender_t object + */ +struct private_mgf1_bitspender_t { + /** + * Public interface. + */ + mgf1_bitspender_t public; + + /** + * MGF1 bit mask generator + */ + mgf1_t *mgf1; + + /** + * Octet storage (accommodates up to 64 octets) + */ + uint8_t octets[HASH_SIZE_SHA512]; + + /** + * Length of the returned hash value in octets + */ + int hash_len; + + /** + * Number of generated octets + */ + int octets_count; + + /** + * Number of available octets + */ + int octets_left; + + /** + * Bit storage (accommodates up to 32 bits) + */ + uint32_t bits; + + /** + * Number of available bits + */ + int bits_left; + + /** + * Byte storage (accommodates up to 4 bytes) + */ + uint8_t bytes[4]; + + /** + * Number of available bytes + */ + int bytes_left; + +}; + +METHOD(mgf1_bitspender_t, get_bits, bool, + private_mgf1_bitspender_t *this, int bits_needed, uint32_t *bits) +{ + int bits_now; + + *bits = 0x00000000; + + if (bits_needed == 0) + { + /* trivial */ + return TRUE; + } + if (bits_needed > 32) + { + /* too many bits requested */ + return FALSE; + } + + while (bits_needed) + { + if (this->bits_left == 0) + { + if (this->octets_left == 0) + { + /* get another block from MGF1 */ + if (!this->mgf1->get_mask(this->mgf1, this->hash_len, + this->octets)) + { + /* no block available */ + return FALSE; + } + this->octets_left = this->hash_len; + this->octets_count += this->hash_len; + } + this->bits = untoh32(this->octets + this->hash_len - + this->octets_left); + this->bits_left = 32; + this->octets_left -= 4; + } + if (bits_needed > this->bits_left) + { + bits_now = this->bits_left; + this->bits_left = 0; + bits_needed -= bits_now; + } + else + { + bits_now = bits_needed; + this->bits_left -= bits_needed; + bits_needed = 0; + } + if (bits_now == 32) + { + *bits = this->bits; + } + else + { + *bits <<= bits_now; + *bits |= this->bits >> this->bits_left; + if (this->bits_left) + { + this->bits &= 0xffffffff >> (32 - this->bits_left); + } + } + } + return TRUE; +} + +METHOD(mgf1_bitspender_t, get_byte, bool, + private_mgf1_bitspender_t *this, uint8_t *byte) +{ + if (this->bytes_left == 0) + { + if (this->octets_left == 0) + { + /* get another block from MGF1 */ + if (!this->mgf1->get_mask(this->mgf1, this->hash_len, this->octets)) + { + /* no block available */ + return FALSE; + } + this->octets_left = this->hash_len; + this->octets_count += this->hash_len; + } + memcpy(this->bytes, this->octets + this->hash_len - this->octets_left, 4); + this->bytes_left = 4; + this->octets_left -= 4; + } + *byte = this->bytes[4 - this->bytes_left--]; + + return TRUE; +} + +METHOD(mgf1_bitspender_t, destroy, void, + private_mgf1_bitspender_t *this) +{ + DBG2(DBG_LIB, "mgf1 generated %u octets", this->octets_count); + memwipe(this->octets, sizeof(this->octets)); + this->mgf1->destroy(this->mgf1); + free(this); +} + +/** + * See header. + */ +mgf1_bitspender_t *mgf1_bitspender_create(hash_algorithm_t alg, chunk_t seed, + bool hash_seed) +{ + private_mgf1_bitspender_t *this; + mgf1_t *mgf1; + + mgf1 = mgf1_create(alg, seed, hash_seed); + if (!mgf1) + { + return NULL; + } + DBG2(DBG_LIB, "mgf1 based on %N is seeded with %u octets", + hash_algorithm_short_names, alg, seed.len); + + INIT(this, + .public = { + .get_bits = _get_bits, + .get_byte = _get_byte, + .destroy = _destroy, + }, + .mgf1 = mgf1, + .hash_len = mgf1->get_hash_size(mgf1), + ); + + return &this->public; +} |