Mercurial > dropbear
view libtomcrypt/src/mac/blake2/blake2bmac_memory_multi.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" #include <stdarg.h> #ifdef LTC_BLAKE2BMAC /** BLAKE2B MAC multiple blocks of memory to produce the authentication tag @param key The secret key @param keylen The length of the secret key (octets) @param mac [out] Destination of the authentication tag @param maclen [in/out] Max size and resulting size of authentication tag @param in The data to BLAKE2B MAC @param inlen The length of the data to BLAKE2B MAC (octets) @param ... tuples of (data,len) pairs to BLAKE2B MAC, terminated with a (NULL,x) (x=don't care) @return CRYPT_OK if successful */ int blake2bmac_memory_multi(const unsigned char *key, unsigned long keylen, unsigned char *mac, unsigned long *maclen, const unsigned char *in, unsigned long inlen, ...) { blake2bmac_state st; int err; va_list args; const unsigned char *curptr; unsigned long curlen; LTC_ARGCHK(key != NULL); LTC_ARGCHK(in != NULL); LTC_ARGCHK(mac != NULL); LTC_ARGCHK(maclen != NULL); va_start(args, inlen); curptr = in; curlen = inlen; if ((err = blake2bmac_init(&st, *maclen, key, keylen)) != CRYPT_OK) { goto LBL_ERR; } for (;;) { if ((err = blake2bmac_process(&st, curptr, curlen)) != CRYPT_OK) { goto LBL_ERR; } curptr = va_arg(args, const unsigned char*); if (curptr == NULL) break; curlen = va_arg(args, unsigned long); } err = blake2bmac_done(&st, mac, maclen); LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(&st, sizeof(blake2bmac_state)); #endif va_end(args); return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */