Mercurial > dropbear
view libtomcrypt/src/encauth/ocb3/ocb3_int_xor_blocks.c @ 1790:42745af83b7d
Introduce extra delay before closing unauthenticated sessions
To make it harder for attackers, introduce a delay to keep an
unauthenticated session open a bit longer, thus blocking a connection
slot until after the delay.
Without this, while there is a limit on the amount of attempts an attacker
can make at the same time (MAX_UNAUTH_PER_IP), the time taken by dropbear to
handle one attempt is still short and thus for each of the allowed parallel
attempts many attempts can be chained one after the other. The attempt rate
is then:
"MAX_UNAUTH_PER_IP / <process time of one attempt>".
With the delay, this rate becomes:
"MAX_UNAUTH_PER_IP / UNAUTH_CLOSE_DELAY".
author | Thomas De Schampheleire <thomas.de_schampheleire@nokia.com> |
---|---|
date | Wed, 15 Feb 2017 13:53:04 +0100 |
parents | 6dba84798cd5 |
children |
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/* 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. */ /** @file ocb3_int_xor_blocks.c OCB implementation, INTERNAL ONLY helper, by Karel Miko */ #include "tomcrypt.h" #ifdef LTC_OCB3_MODE /** Compute xor for two blocks of bytes 'out = block_a XOR block_b' (internal function) @param out The block of bytes (output) @param block_a The block of bytes (input) @param block_b The block of bytes (input) @param block_len The size of block_a, block_b, out */ void ocb3_int_xor_blocks(unsigned char *out, const unsigned char *block_a, const unsigned char *block_b, unsigned long block_len) { int x; if (out == block_a) { for (x = 0; x < (int)block_len; x++) out[x] ^= block_b[x]; } else { for (x = 0; x < (int)block_len; x++) out[x] = block_a[x] ^ block_b[x]; } } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */