diff options
| -rw-r--r-- | src/rng/hmac_rng/hmac_rng.cpp | 35 |
1 files changed, 20 insertions, 15 deletions
diff --git a/src/rng/hmac_rng/hmac_rng.cpp b/src/rng/hmac_rng/hmac_rng.cpp index 84a7b1c13..51d10f641 100644 --- a/src/rng/hmac_rng/hmac_rng.cpp +++ b/src/rng/hmac_rng/hmac_rng.cpp @@ -115,7 +115,7 @@ void HMAC_RNG::reseed_with_input(u32bit poll_bits, K.clear(); counter = 0; - if(input_length || accum.bits_collected() >= poll_bits) + if(input_length > 64 || accum.bits_collected() >= 128) seeded = true; } @@ -133,7 +133,7 @@ void HMAC_RNG::reseed(u32bit poll_bits) */ void HMAC_RNG::add_entropy(const byte input[], u32bit length) { - reseed_with_input(0, input, length); + reseed_with_input(64, input, length); } /** @@ -171,6 +171,12 @@ HMAC_RNG::HMAC_RNG(MessageAuthenticationCode* extractor_mac, MessageAuthenticationCode* prf_mac) : extractor(extractor_mac), prf(prf_mac) { + if(!prf->valid_keylength(extractor->OUTPUT_LENGTH) || + !extractor->valid_keylength(prf->OUTPUT_LENGTH)) + throw Invalid_Argument("HMAC_RNG: Bad algo combination " + + extractor->name() + " and " + + prf->name()); + // First PRF inputs are all zero, as specified in section 2 K.resize(prf->OUTPUT_LENGTH); counter = 0; @@ -183,26 +189,25 @@ HMAC_RNG::HMAC_RNG(MessageAuthenticationCode* extractor_mac, We will want to use the PRF before we set the first key (in reseed_with_input), and it is a pain to keep track if it is set or - not. Since the first time it doesn't matter anyway, just set it to - a constant: randomize() will not produce output unless is_seeded() - returns true, and that will only be the case if the estimated - entropy counter is high enough. That variable is only set when a - reseeding is performed. + not. Since the first time it doesn't matter anyway, just set the + PRF key to constant zero: randomize() will not produce output + unless is_seeded() returns true, and that will only be the case if + the estimated entropy counter is high enough. That variable is only + set when a reseeding is performed. */ - std::string prf_key = "Botan HMAC_RNG PRF"; - prf->set_key(reinterpret_cast<const byte*>(prf_key.c_str()), - prf_key.length()); + MemoryVector<byte> prf_key(extractor->OUTPUT_LENGTH); + prf->set_key(prf_key); /* - This will be used as the first XTS value when extracting input. - XTS values after this one are generated using the PRF. + Use PRF("Botan HMAC_RNG XTS") as the intitial XTS key. + + This will be used during the first extraction sequence; XTS values + after this one are generated using the PRF. If I understand the E-t-E paper correctly (specifically Section 4), using this fixed extractor key is safe to do. */ - std::string xts = "Botan HMAC_RNG XTS"; - extractor->set_key(reinterpret_cast<const byte*>(xts.c_str()), - xts.length()); + extractor->set_key(prf->process("Botan HMAC_RNG XTS")); } /** |