Mercurial > dropbear
view libtomcrypt/src/mac/pmac/pmac_file.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 | e9dba7abd939 |
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 pmac_file.c PMAC implementation, process a file, by Tom St Denis */ #ifdef LTC_PMAC /** PMAC a file @param cipher The index of the cipher desired @param key The secret key @param keylen The length of the secret key (octets) @param filename The name of the file to send through PMAC @param out [out] Destination for the authentication tag @param outlen [in/out] Max size and resulting size of the authentication tag @return CRYPT_OK if successful, CRYPT_NOP if file support has been disabled */ int pmac_file(int cipher, const unsigned char *key, unsigned long keylen, const char *filename, unsigned char *out, unsigned long *outlen) { #ifdef LTC_NO_FILE LTC_UNUSED_PARAM(cipher); LTC_UNUSED_PARAM(key); LTC_UNUSED_PARAM(keylen); LTC_UNUSED_PARAM(filename); LTC_UNUSED_PARAM(out); LTC_UNUSED_PARAM(outlen); return CRYPT_NOP; #else size_t x; int err; pmac_state pmac; FILE *in; unsigned char *buf; LTC_ARGCHK(key != NULL); LTC_ARGCHK(filename != NULL); LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); if ((buf = XMALLOC(LTC_FILE_READ_BUFSIZE)) == NULL) { return CRYPT_MEM; } if ((err = pmac_init(&pmac, cipher, key, keylen)) != CRYPT_OK) { goto LBL_ERR; } in = fopen(filename, "rb"); if (in == NULL) { err = CRYPT_FILE_NOTFOUND; goto LBL_ERR; } do { x = fread(buf, 1, LTC_FILE_READ_BUFSIZE, in); if ((err = pmac_process(&pmac, buf, (unsigned long)x)) != CRYPT_OK) { fclose(in); goto LBL_CLEANBUF; } } while (x == LTC_FILE_READ_BUFSIZE); if (fclose(in) != 0) { err = CRYPT_ERROR; goto LBL_CLEANBUF; } err = pmac_done(&pmac, out, outlen); LBL_CLEANBUF: zeromem(buf, LTC_FILE_READ_BUFSIZE); LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(&pmac, sizeof(pmac_state)); #endif XFREE(buf); return err; #endif } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */