Mercurial > dropbear
view libtomcrypt/src/hashes/helper/hash_memory.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 |
line wrap: on
line source
/* 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" #ifdef LTC_HASH_HELPERS /** @file hash_memory.c Hash memory helper, Tom St Denis */ /** Hash a block of memory and store the digest. @param hash The index of the hash you wish to use @param in The data you wish to hash @param inlen The length of the data to hash (octets) @param out [out] Where to store the digest @param outlen [in/out] Max size and resulting size of the digest @return CRYPT_OK if successful */ int hash_memory(int hash, const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen) { hash_state *md; int err; LTC_ARGCHK(in != NULL); LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); if ((err = hash_is_valid(hash)) != CRYPT_OK) { return err; } if (*outlen < hash_descriptor[hash].hashsize) { *outlen = hash_descriptor[hash].hashsize; return CRYPT_BUFFER_OVERFLOW; } md = XMALLOC(sizeof(hash_state)); if (md == NULL) { return CRYPT_MEM; } if ((err = hash_descriptor[hash].init(md)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash].process(md, in, inlen)) != CRYPT_OK) { goto LBL_ERR; } err = hash_descriptor[hash].done(md, out); *outlen = hash_descriptor[hash].hashsize; LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(md, sizeof(hash_state)); #endif XFREE(md); return err; } #endif /* #ifdef LTC_HASH_HELPERS */ /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */