Mercurial > dropbear
view libtomcrypt/src/mac/pelican/pelican.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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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" /** @file pelican.c Pelican MAC, initialize state, by Tom St Denis */ #ifdef LTC_PELICAN #define __LTC_AES_TAB_C__ #define ENCRYPT_ONLY #define PELI_TAB #include "../../ciphers/aes/aes_tab.c" /** Initialize a Pelican state @param pelmac The Pelican state to initialize @param key The secret key @param keylen The length of the secret key (octets) @return CRYPT_OK if successful */ int pelican_init(pelican_state *pelmac, const unsigned char *key, unsigned long keylen) { int err; LTC_ARGCHK(pelmac != NULL); LTC_ARGCHK(key != NULL); #ifdef LTC_FAST if (16 % sizeof(LTC_FAST_TYPE)) { return CRYPT_INVALID_ARG; } #endif if ((err = aes_setup(key, keylen, 0, &pelmac->K)) != CRYPT_OK) { return err; } zeromem(pelmac->state, 16); aes_ecb_encrypt(pelmac->state, pelmac->state, &pelmac->K); pelmac->buflen = 0; return CRYPT_OK; } static void _four_rounds(pelican_state *pelmac) { ulong32 s0, s1, s2, s3, t0, t1, t2, t3; int r; LOAD32H(s0, pelmac->state ); LOAD32H(s1, pelmac->state + 4); LOAD32H(s2, pelmac->state + 8); LOAD32H(s3, pelmac->state + 12); for (r = 0; r < 4; r++) { t0 = Te0(byte(s0, 3)) ^ Te1(byte(s1, 2)) ^ Te2(byte(s2, 1)) ^ Te3(byte(s3, 0)); t1 = Te0(byte(s1, 3)) ^ Te1(byte(s2, 2)) ^ Te2(byte(s3, 1)) ^ Te3(byte(s0, 0)); t2 = Te0(byte(s2, 3)) ^ Te1(byte(s3, 2)) ^ Te2(byte(s0, 1)) ^ Te3(byte(s1, 0)); t3 = Te0(byte(s3, 3)) ^ Te1(byte(s0, 2)) ^ Te2(byte(s1, 1)) ^ Te3(byte(s2, 0)); s0 = t0; s1 = t1; s2 = t2; s3 = t3; } STORE32H(s0, pelmac->state ); STORE32H(s1, pelmac->state + 4); STORE32H(s2, pelmac->state + 8); STORE32H(s3, pelmac->state + 12); } /** Process a block of text through Pelican @param pelmac The Pelican MAC state @param in The input @param inlen The length input (octets) @return CRYPT_OK on success */ int pelican_process(pelican_state *pelmac, const unsigned char *in, unsigned long inlen) { LTC_ARGCHK(pelmac != NULL); LTC_ARGCHK(in != NULL); /* check range */ if (pelmac->buflen < 0 || pelmac->buflen > 15) { return CRYPT_INVALID_ARG; } #ifdef LTC_FAST if (pelmac->buflen == 0) { while (inlen & ~15) { int x; for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)pelmac->state + x)) ^= *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)in + x)); } _four_rounds(pelmac); in += 16; inlen -= 16; } } #endif while (inlen--) { pelmac->state[pelmac->buflen++] ^= *in++; if (pelmac->buflen == 16) { _four_rounds(pelmac); pelmac->buflen = 0; } } return CRYPT_OK; } /** Terminate Pelican MAC @param pelmac The Pelican MAC state @param out [out] The TAG @return CRYPT_OK on sucess */ int pelican_done(pelican_state *pelmac, unsigned char *out) { LTC_ARGCHK(pelmac != NULL); LTC_ARGCHK(out != NULL); /* check range */ if (pelmac->buflen < 0 || pelmac->buflen > 16) { return CRYPT_INVALID_ARG; } if (pelmac->buflen == 16) { _four_rounds(pelmac); pelmac->buflen = 0; } pelmac->state[pelmac->buflen++] ^= 0x80; aes_ecb_encrypt(pelmac->state, out, &pelmac->K); aes_done(&pelmac->K); return CRYPT_OK; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */