Mercurial > dropbear
view libtomcrypt/src/pk/dh/dh_export.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" #ifdef LTC_MDH /** Export a DH key to a binary packet @param out [out] The destination for the key @param outlen [in/out] The max size and resulting size of the DH key @param type Which type of key (PK_PRIVATE or PK_PUBLIC) @param key The key you wish to export @return CRYPT_OK if successful */ int dh_export(unsigned char *out, unsigned long *outlen, int type, dh_key *key) { unsigned char flags[1]; int err; unsigned long version = 0; LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); LTC_ARGCHK(key != NULL); if (type == PK_PRIVATE) { /* export x - private key */ flags[0] = 1; err = der_encode_sequence_multi(out, outlen, LTC_ASN1_SHORT_INTEGER, 1UL, &version, LTC_ASN1_BIT_STRING, 1UL, flags, LTC_ASN1_INTEGER, 1UL, key->prime, LTC_ASN1_INTEGER, 1UL, key->base, LTC_ASN1_INTEGER, 1UL, key->x, LTC_ASN1_EOL, 0UL, NULL); } else { /* export y - public key */ flags[0] = 0; err = der_encode_sequence_multi(out, outlen, LTC_ASN1_SHORT_INTEGER, 1UL, &version, LTC_ASN1_BIT_STRING, 1UL, flags, LTC_ASN1_INTEGER, 1UL, key->prime, LTC_ASN1_INTEGER, 1UL, key->base, LTC_ASN1_INTEGER, 1UL, key->y, LTC_ASN1_EOL, 0UL, NULL); } return err; } #endif /* LTC_MDH */ /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */