Mercurial > dropbear
view ltc_prng.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 | d68d61e7056a |
children |
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/* Copied from libtomcrypt/src/prngs/sprng.c and modified to * use Dropbear's genrandom(). */ /* 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. * * Tom St Denis, [email protected], http://libtomcrypt.com */ #include "includes.h" #include "dbrandom.h" #include "ltc_prng.h" /** @file sprng.c Secure PRNG, Tom St Denis */ /* A secure PRNG using the RNG functions. Basically this is a * wrapper that allows you to use a secure RNG as a PRNG * in the various other functions. */ #if DROPBEAR_LTC_PRNG /** Start the PRNG @param prng [out] The PRNG state to initialize @return CRYPT_OK if successful */ int dropbear_prng_start(prng_state* UNUSED(prng)) { return CRYPT_OK; } /** Add entropy to the PRNG state @param in The data to add @param inlen Length of the data to add @param prng PRNG state to update @return CRYPT_OK if successful */ int dropbear_prng_add_entropy(const unsigned char* UNUSED(in), unsigned long UNUSED(inlen), prng_state* UNUSED(prng)) { return CRYPT_OK; } /** Make the PRNG ready to read from @param prng The PRNG to make active @return CRYPT_OK if successful */ int dropbear_prng_ready(prng_state* UNUSED(prng)) { return CRYPT_OK; } /** Read from the PRNG @param out Destination @param outlen Length of output @param prng The active PRNG to read from @return Number of octets read */ unsigned long dropbear_prng_read(unsigned char* out, unsigned long outlen, prng_state* UNUSED(prng)) { LTC_ARGCHK(out != NULL); genrandom(out, outlen); return outlen; } /** Terminate the PRNG @param prng The PRNG to terminate @return CRYPT_OK if successful */ int dropbear_prng_done(prng_state* UNUSED(prng)) { return CRYPT_OK; } /** Export the PRNG state @param out [out] Destination @param outlen [in/out] Max size and resulting size of the state @param prng The PRNG to export @return CRYPT_OK if successful */ int dropbear_prng_export(unsigned char* UNUSED(out), unsigned long* outlen, prng_state* UNUSED(prng)) { LTC_ARGCHK(outlen != NULL); *outlen = 0; return CRYPT_OK; } /** Import a PRNG state @param in The PRNG state @param inlen Size of the state @param prng The PRNG to import @return CRYPT_OK if successful */ int dropbear_prng_import(const unsigned char* UNUSED(in), unsigned long UNUSED(inlen), prng_state* UNUSED(prng)) { return CRYPT_OK; } /** PRNG self-test @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled */ int dropbear_prng_test(void) { return CRYPT_OK; } const struct ltc_prng_descriptor dropbear_prng_desc = { "dropbear_prng", 0, dropbear_prng_start, dropbear_prng_add_entropy, dropbear_prng_ready, dropbear_prng_read, dropbear_prng_done, dropbear_prng_export, dropbear_prng_import, dropbear_prng_test }; #endif /* DROPBEAR_LTC_PRNG */