/* * Copyright (C) 2012 Michael Brown . * * 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 any later version. * * 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. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301, USA. */ FILE_LICENCE ( GPL2_OR_LATER ); /** @file * * HMAC_DRBG algorithm * * This algorithm is designed to comply with ANS X9.82 Part 3-2007 * Section 10.2.2.2. This standard is not freely available, but most * of the text appears to be shared with NIST SP 800-90, which can be * downloaded from * * http://csrc.nist.gov/publications/nistpubs/800-90/SP800-90revised_March2007.pdf * * Where possible, references are given to both documents. In the * case of any disagreement, ANS X9.82 takes priority over NIST SP * 800-90. (In particular, note that some algorithms that are * Approved by NIST SP 800-90 are not Approved by ANS X9.82.) */ #include #include #include #include #include #include #include /** * Update the HMAC_DRBG key * * @v hash Underlying hash algorithm * @v state HMAC_DRBG internal state * @v data Provided data * @v len Length of provided data * @v single Single byte used in concatenation * * This function carries out the operation * * K = HMAC ( K, V || single || provided_data ) * * as used by hmac_drbg_update() */ static void hmac_drbg_update_key ( struct digest_algorithm *hash, struct hmac_drbg_state *state, const void *data, size_t len, const uint8_t single ) { uint8_t context[ hash->ctxsize ]; size_t out_len = hash->digestsize; DBGC ( state, "HMAC_DRBG_%s %p provided data :\n", hash->name, state ); DBGC_HDA ( state, 0, data, len ); /* Sanity checks */ assert ( hash != NULL ); assert ( state != NULL ); assert ( ( data != NULL ) || ( len == 0 ) ); assert ( ( single == 0x00 ) || ( single == 0x01 ) ); /* K = HMAC ( K, V || single || provided_data ) */ hmac_init ( hash, context, state->key, &out_len ); assert ( out_len == hash->digestsize ); hmac_update ( hash, context, state->value, out_len ); hmac_update ( hash, context, &single, sizeof ( single ) ); hmac_update ( hash, context, data, len ); hmac_final ( hash, context, state->key, &out_len, state->key ); assert ( out_len == hash->digestsize ); DBGC ( state, "HMAC_DRBG_%s %p K = HMAC ( K, V || %#02x || " "provided_data ) :\n", hash->name, state, single ); DBGC_HDA ( state, 0, state->key, out_len ); } /** * Update the HMAC_DRBG value * * @v hash Underlying hash algorithm * @v state HMAC_DRBG internal state * @v data Provided data * @v len Length of provided data * @v single Single byte used in concatenation * * This function carries out the operation * * V = HMAC ( K, V ) * * as used by hmac_drbg_update() and hmac_drbg_generate() */ static void hmac_drbg_update_value ( struct digest_algorithm *hash, struct hmac_drbg_state *state ) { uint8_t context[ hash->ctxsize ]; size_t out_len = hash->digestsize; /* Sanity checks */ assert ( hash != NULL ); assert ( state != NULL ); /* V = HMAC ( K, V ) */ hmac_init ( hash, context, state->key, &out_len ); assert ( out_len == hash->digestsize ); hmac_update ( hash, context, state->value, out_len ); hmac_final ( hash, context, state->key, &out_len, state->value ); assert ( out_len == hash->digestsize ); DBGC ( state, "HMAC_DRBG_%s %p V = HMAC ( K, V ) :\n", hash->name, state ); DBGC_HDA ( state, 0, state->value, out_len ); } /** * Update HMAC_DRBG internal state * * @v hash Underlying hash algorithm * @v state HMAC_DRBG internal state * @v data Provided data * @v len Length of provided data * * This is the HMAC_DRBG_Update function defined in ANS X9.82 Part * 3-2007 Section 10.2.2.2.2 (NIST SP 800-90 Section 10.1.2.2). * * The key and value are updated in-place within the HMAC_DRBG * internal state. */ static void hmac_drbg_update ( struct digest_algorithm *hash, struct hmac_drbg_state *state, const void *data, size_t len ) { DBGC ( state, "HMAC_DRBG_%s %p update\n", hash->name, state ); /* Sanity checks */ assert ( hash != NULL ); assert ( state != NULL ); assert ( ( data != NULL ) || ( len == 0 ) ); /* 1. K = HMAC ( K, V || 0x00 || provided_data ) */ hmac_drbg_update_key ( hash, state, data, len, 0x00 ); /* 2. V = HMAC ( K, V ) */ hmac_drbg_update_value ( hash, state ); /* 3. If ( provided_data = Null ), then return K and V */ if ( ! len ) return; /* 4. K = HMAC ( K, V || 0x01 || provided_data ) */ hmac_drbg_update_key ( hash, state, data, len, 0x01 ); /* 5. V = HMAC ( K, V ) */ hmac_drbg_update_value ( hash, state ); /* 6. Return K and V */ } /** * Instantiate HMAC_DRBG * * @v hash Underlying hash algorithm * @v state HMAC_DRBG internal state to be initialised * @v entropy Entropy input * @v entropy_len Length of entropy input * @v personal Personalisation string * @v personal_len Length of personalisation string * * This is the HMAC_DRBG_Instantiate_algorithm function defined in ANS * X9.82 Part 3-2007 Section 10.2.2.2.3 (NIST SP 800-90 Section * 10.1.2.3). * * The nonce must be included within the entropy input (i.e. the * entropy input must contain at least 3/2 * security_strength bits of * entropy, as per ANS X9.82 Part 3-2007 Section 8.4.2 (NIST SP 800-90 * Section 8.6.7). * * The key, value and reseed counter are updated in-place within the * HMAC_DRBG internal state. */ void hmac_drbg_instantiate ( struct digest_algorithm *hash, struct hmac_drbg_state *state, const void *entropy, size_t entropy_len, const void *personal, size_t personal_len ){ size_t out_len = hash->digestsize; DBGC ( state, "HMAC_DRBG_%s %p instantiate\n", hash->name, state ); /* Sanity checks */ assert ( hash != NULL ); assert ( state != NULL ); assert ( entropy != NULL ); assert ( ( personal != NULL ) || ( personal_len == 0 ) ); /* 1. seed_material = entropy_input || nonce || * personalisation_string */ /* 2. Key = 0x00 00..00 */ memset ( state->key, 0x00, out_len ); /* 3. V = 0x01 01...01 */ memset ( state->value, 0x01, out_len ); /* 4. ( Key, V ) = HMAC_DBRG_Update ( seed_material, Key, V ) * 5. reseed_counter = 1 * 6. Return V, Key and reseed_counter as the * initial_working_state */ hmac_drbg_reseed ( hash, state, entropy, entropy_len, personal, personal_len ); } /** * Reseed HMAC_DRBG * * @v hash Underlying hash algorithm * @v state HMAC_DRBG internal state * @v entropy Entropy input * @v entropy_len Length of entropy input * @v additional Additional input * @v additional_len Length of additional input * * This is the HMAC_DRBG_Reseed_algorithm function defined in ANS X9.82 * Part 3-2007 Section 10.2.2.2.4 (NIST SP 800-90 Section 10.1.2.4). * * The key, value and reseed counter are updated in-place within the * HMAC_DRBG internal state. */ void hmac_drbg_reseed ( struct digest_algorithm *hash, struct hmac_drbg_state *state, const void *entropy, size_t entropy_len, const void *additional, size_t additional_len ) { uint8_t seed_material[ entropy_len + additional_len ]; DBGC ( state, "HMAC_DRBG_%s %p (re)seed\n", hash->name, state ); /* Sanity checks */ assert ( hash != NULL ); assert ( state != NULL ); assert ( entropy != NULL ); assert ( ( additional != NULL ) || ( additional_len == 0 ) ); /* 1. seed_material = entropy_input || additional_input */ memcpy ( seed_material, entropy, entropy_len ); memcpy ( ( seed_material + entropy_len ), additional, additional_len ); DBGC ( state, "HMAC_DRBG_%s %p seed material :\n", hash->name, state ); DBGC_HDA ( state, 0, seed_material, sizeof ( seed_material ) ); /* 2. ( Key, V ) = HMAC_DBRG_Update ( seed_material, Key, V ) */ hmac_drbg_update ( hash, state, seed_material, sizeof ( seed_material ) ); /* 3. reseed_counter = 1 */ state->reseed_counter = 1; /* 4. Return V, Key and reseed_counter as the new_working_state */ } /** * Generate pseudorandom bits using HMAC_DRBG * * @v hash Underlying hash algorithm * @v state HMAC_DRBG internal state * @v additional Additional input * @v additional_len Length of additional input * @v data Output buffer * @v len Length of output buffer * @ret rc Return status code * * This is the HMAC_DRBG_Generate_algorithm function defined in ANS X9.82 * Part 3-2007 Section 10.2.2.2.5 (NIST SP 800-90 Section 10.1.2.5). * * Requests must be for an integral number of bytes. * * The key, value and reseed counter are updated in-place within the * HMAC_DRBG internal state. * * Note that the only permitted error is "reseed required". */ int hmac_drbg_generate ( struct digest_algorithm *hash, struct hmac_drbg_state *state, const void *additional, size_t additional_len, void *data, size_t len ) { size_t out_len = hash->digestsize; void *orig_data = data; size_t orig_len = len; size_t frag_len; DBGC ( state, "HMAC_DRBG_%s %p generate\n", hash->name, state ); /* Sanity checks */ assert ( hash != NULL ); assert ( state != NULL ); assert ( data != NULL ); assert ( ( additional != NULL ) || ( additional_len == 0 ) ); /* 1. If reseed_counter > reseed_interval, then return an * indication that a reseed is required */ if ( state->reseed_counter > HMAC_DRBG_RESEED_INTERVAL ) { DBGC ( state, "HMAC_DRBG_%s %p reseed interval exceeded\n", hash->name, state ); return -ESTALE; } /* 2. If additional_input != Null, then * ( Key, V ) = HMAC_DRBG_Update ( additional_input, Key, V ) */ if ( additional_len ) hmac_drbg_update ( hash, state, additional, additional_len ); /* 3. temp = Null * 4. While ( len ( temp ) < requested_number_of_bits ) do: */ while ( len ) { /* 4.1 V = HMAC ( Key, V ) */ hmac_drbg_update_value ( hash, state ); /* 4.2. temp = temp || V * 5. returned_bits = Leftmost requested_number_of_bits * of temp */ frag_len = len; if ( frag_len > out_len ) frag_len = out_len; memcpy ( data, state->value, frag_len ); data += frag_len; len -= frag_len; } /* 6. ( Key, V ) = HMAC_DRBG_Update ( additional_input, Key, V ) */ hmac_drbg_update ( hash, state, additional, additional_len ); /* 7. reseed_counter = reseed_counter + 1 */ state->reseed_counter++; DBGC ( state, "HMAC_DRBG_%s %p generated :\n", hash->name, state ); DBGC_HDA ( state, 0, orig_data, orig_len ); /* 8. Return SUCCESS, returned_bits, and the new values of * Key, V and reseed_counter as the new_working_state */ return 0; }