annotate libtomcrypt/src/prngs/rng_make_prng.c @ 1715:3974f087d9c0

Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 6dba84798cd5
children
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 #ifdef LTC_RNG_MAKE_PRNG
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12 /**
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13 @file rng_make_prng.c
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14 portable way to get secure random bits to feed a PRNG (Tom St Denis)
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15 */
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17 /**
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18 Create a PRNG from a RNG
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19 @param bits Number of bits of entropy desired (64 ... 1024)
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20 @param wprng Index of which PRNG to setup
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21 @param prng [out] PRNG state to initialize
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22 @param callback A pointer to a void function for when the RNG is slow, this can be NULL
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23 @return CRYPT_OK if successful
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24 */
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25 int rng_make_prng(int bits, int wprng, prng_state *prng,
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26 void (*callback)(void))
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27 {
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28 unsigned char buf[256];
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29 int err;
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31 LTC_ARGCHK(prng != NULL);
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33 /* check parameter */
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34 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
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35 return err;
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36 }
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38 if (bits < 64 || bits > 1024) {
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39 return CRYPT_INVALID_PRNGSIZE;
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40 }
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42 if ((err = prng_descriptor[wprng].start(prng)) != CRYPT_OK) {
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43 return err;
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44 }
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46 bits = ((bits/8)+((bits&7)!=0?1:0)) * 2;
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47 if (rng_get_bytes(buf, (unsigned long)bits, callback) != (unsigned long)bits) {
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48 return CRYPT_ERROR_READPRNG;
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49 }
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51 if ((err = prng_descriptor[wprng].add_entropy(buf, (unsigned long)bits, prng)) != CRYPT_OK) {
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52 return err;
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53 }
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55 if ((err = prng_descriptor[wprng].ready(prng)) != CRYPT_OK) {
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56 return err;
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57 }
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59 #ifdef LTC_CLEAN_STACK
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60 zeromem(buf, sizeof(buf));
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61 #endif
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62 return CRYPT_OK;
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63 }
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64 #endif /* #ifdef LTC_RNG_MAKE_PRNG */
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66
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67 /* ref: $Format:%D$ */
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68 /* git commit: $Format:%H$ */
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69 /* commit time: $Format:%ai$ */