Mercurial > dropbear
view libtomcrypt/src/mac/f9/f9_process.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. */ #include "tomcrypt.h" /** @file f9_process.c f9 Support, process blocks with f9 */ #ifdef LTC_F9_MODE /** Process data through f9-MAC @param f9 The f9-MAC state @param in Input data to process @param inlen Length of input in octets Return CRYPT_OK on success */ int f9_process(f9_state *f9, const unsigned char *in, unsigned long inlen) { int err, x; LTC_ARGCHK(f9 != NULL); LTC_ARGCHK(in != NULL); /* check structure */ if ((err = cipher_is_valid(f9->cipher)) != CRYPT_OK) { return err; } if ((f9->blocksize > cipher_descriptor[f9->cipher].block_length) || (f9->blocksize < 0) || (f9->buflen > f9->blocksize) || (f9->buflen < 0)) { return CRYPT_INVALID_ARG; } #ifdef LTC_FAST if (f9->buflen == 0) { while (inlen >= (unsigned long)f9->blocksize) { for (x = 0; x < f9->blocksize; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST(&(f9->IV[x]))) ^= *(LTC_FAST_TYPE_PTR_CAST(&(in[x]))); } cipher_descriptor[f9->cipher].ecb_encrypt(f9->IV, f9->IV, &f9->key); for (x = 0; x < f9->blocksize; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST(&(f9->ACC[x]))) ^= *(LTC_FAST_TYPE_PTR_CAST(&(f9->IV[x]))); } in += f9->blocksize; inlen -= f9->blocksize; } } #endif while (inlen) { if (f9->buflen == f9->blocksize) { cipher_descriptor[f9->cipher].ecb_encrypt(f9->IV, f9->IV, &f9->key); for (x = 0; x < f9->blocksize; x++) { f9->ACC[x] ^= f9->IV[x]; } f9->buflen = 0; } f9->IV[f9->buflen++] ^= *in++; --inlen; } return CRYPT_OK; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */