Mercurial > dropbear
view libtomcrypt/src/mac/pmac/pmac_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> /** @file pmac_memory_multi.c PMAC implementation, process multiple blocks of memory, by Tom St Denis */ #ifdef LTC_PMAC /** PMAC multiple blocks of memory @param cipher The index of the cipher desired @param key The secret key @param keylen The length of the secret key (octets) @param out [out] Destination for the authentication tag @param outlen [in/out] The max size and resulting size of the authentication tag @param in The data you wish to send through PMAC @param inlen The length of data you wish to send through PMAC (octets) @param ... tuples of (data,len) pairs to PMAC, terminated with a (NULL,x) (x=don't care) @return CRYPT_OK if successful */ int pmac_memory_multi(int cipher, const unsigned char *key, unsigned long keylen, unsigned char *out, unsigned long *outlen, const unsigned char *in, unsigned long inlen, ...) { int err; pmac_state *pmac; va_list args; const unsigned char *curptr; unsigned long curlen; LTC_ARGCHK(key != NULL); LTC_ARGCHK(in != NULL); LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); /* allocate ram for pmac state */ pmac = XMALLOC(sizeof(pmac_state)); if (pmac == NULL) { return CRYPT_MEM; } if ((err = pmac_init(pmac, cipher, key, keylen)) != CRYPT_OK) { goto LBL_ERR; } va_start(args, inlen); curptr = in; curlen = inlen; for (;;) { /* process buf */ if ((err = pmac_process(pmac, curptr, curlen)) != CRYPT_OK) { goto LBL_ERR; } /* step to next */ curptr = va_arg(args, const unsigned char*); if (curptr == NULL) { break; } curlen = va_arg(args, unsigned long); } if ((err = pmac_done(pmac, out, outlen)) != CRYPT_OK) { goto LBL_ERR; } LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(pmac, sizeof(pmac_state)); #endif XFREE(pmac); va_end(args); return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */