diff options
Diffstat (limited to 'src/tpm2/Entropy.c')
| -rw-r--r-- | src/tpm2/Entropy.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/tpm2/Entropy.c b/src/tpm2/Entropy.c new file mode 100644 index 0000000..2c2cc18 --- /dev/null +++ b/src/tpm2/Entropy.c @@ -0,0 +1,184 @@ +/********************************************************************************/ +/* */ +/* Entropy */ +/* Written by Ken Goldman */ +/* IBM Thomas J. Watson Research Center */ +/* $Id: Entropy.c 1490 2019-07-26 21:13:22Z kgoldman $ */ +/* */ +/* Licenses and Notices */ +/* */ +/* 1. Copyright Licenses: */ +/* */ +/* - Trusted Computing Group (TCG) grants to the user of the source code in */ +/* this specification (the "Source Code") a worldwide, irrevocable, */ +/* nonexclusive, royalty free, copyright license to reproduce, create */ +/* derivative works, distribute, display and perform the Source Code and */ +/* derivative works thereof, and to grant others the rights granted herein. */ +/* */ +/* - The TCG grants to the user of the other parts of the specification */ +/* (other than the Source Code) the rights to reproduce, distribute, */ +/* display, and perform the specification solely for the purpose of */ +/* developing products based on such documents. */ +/* */ +/* 2. Source Code Distribution Conditions: */ +/* */ +/* - Redistributions of Source Code must retain the above copyright licenses, */ +/* this list of conditions and the following disclaimers. */ +/* */ +/* - Redistributions in binary form must reproduce the above copyright */ +/* licenses, this list of conditions and the following disclaimers in the */ +/* documentation and/or other materials provided with the distribution. */ +/* */ +/* 3. Disclaimers: */ +/* */ +/* - THE COPYRIGHT LICENSES SET FORTH ABOVE DO NOT REPRESENT ANY FORM OF */ +/* LICENSE OR WAIVER, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, WITH */ +/* RESPECT TO PATENT RIGHTS HELD BY TCG MEMBERS (OR OTHER THIRD PARTIES) */ +/* THAT MAY BE NECESSARY TO IMPLEMENT THIS SPECIFICATION OR OTHERWISE. */ +/* Contact TCG Administration (admin@trustedcomputinggroup.org) for */ +/* information on specification licensing rights available through TCG */ +/* membership agreements. */ +/* */ +/* - THIS SPECIFICATION IS PROVIDED "AS IS" WITH NO EXPRESS OR IMPLIED */ +/* WARRANTIES WHATSOEVER, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR */ +/* FITNESS FOR A PARTICULAR PURPOSE, ACCURACY, COMPLETENESS, OR */ +/* NONINFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS, OR ANY WARRANTY */ +/* OTHERWISE ARISING OUT OF ANY PROPOSAL, SPECIFICATION OR SAMPLE. */ +/* */ +/* - Without limitation, TCG and its members and licensors disclaim all */ +/* liability, including liability for infringement of any proprietary */ +/* rights, relating to use of information in this specification and to the */ +/* implementation of this specification, and TCG disclaims all liability for */ +/* cost of procurement of substitute goods or services, lost profits, loss */ +/* of use, loss of data or any incidental, consequential, direct, indirect, */ +/* or special damages, whether under contract, tort, warranty or otherwise, */ +/* arising in any way out of use or reliance upon this specification or any */ +/* information herein. */ +/* */ +/* (c) Copyright IBM Corp. and others, 2016 - 2019 */ +/* */ +/********************************************************************************/ + +/* C.4 Entropy.c */ +/* C.4.1. Includes and Local values*/ +#define _CRT_RAND_S +#include <stdlib.h> +#include <memory.h> + +#include <openssl/rand.h> /* libtpms added */ + +#include <time.h> +#include "Platform.h" +#ifdef _MSC_VER +#include <process.h> +#else +#include <unistd.h> +#endif + +/* This is the last 32-bits of hardware entropy produced. We have to check to see that two + consecutive 32-bit values are not the same because (according to FIPS 140-2, annex C */ +/* "If each call to a RNG produces blocks of n bits (where n > 15), the first n-bit block generated + after power-up, initialization, or reset shall not be used, but shall be saved for comparison + with the next n-bit block to be generated. Each subsequent generation of an n-bit block shall be + compared with the previously generated block. The test shall fail if any two compared n-bit + blocks are equal." */ +extern uint32_t lastEntropy; + +/* C.4.2. Functions */ +/* C.4.2.1. rand32() */ +/* Local function to get a 32-bit random number */ + +static uint32_t +rand32( + void + ) +{ + uint32_t rndNum = rand(); +#if RAND_MAX < UINT16_MAX + // If the maximum value of the random number is a 15-bit number, then shift it up + // 15 bits, get 15 more bits, shift that up 2 and then XOR in another value to get + // a full 32 bits. + rndNum = (rndNum << 15) ^ rand(); + rndNum = (rndNum << 2) ^ rand(); +#elif RAND_MAX == UINT16_MAX + // If the maximum size is 16-bits, shift it and add another 16 bits + rndNum = (rndNum << 16) ^ rand(); +#elif RAND_MAX < UINT32_MAX + // If 31 bits, then shift 1 and include another random value to get the extra bit + rndNum = (rndNum << 1) ^ rand(); +#endif + return rndNum; +} + +/* C.4.2.2 _plat__GetEntropy() */ +/* This function is used to get available hardware entropy. In a hardware implementation of this + function, there would be no call to the system to get entropy. */ +/* Return Values Meaning */ +/* < 0 hardware failure of the entropy generator, this is sticky */ +/* >= 0 the returned amount of entropy (bytes) */ +LIB_EXPORT int32_t +_plat__GetEntropy( + unsigned char *entropy, // output buffer + uint32_t amount // amount requested + ) +{ + uint32_t rndNum; + int32_t ret; + // + // libtpms added begin + if (amount > 0 && RAND_bytes(entropy, amount) == 1) + return amount; + // fall back to 'original' method + // libtpms added end + + if(amount == 0) + { + // Seed the platform entropy source if the entropy source is software. There is + // no reason to put a guard macro (#if or #ifdef) around this code because this + // code would not be here if someone was changing it for a system with actual + // hardware. + // + // NOTE 1: The following command does not provide proper cryptographic entropy. + // Its primary purpose to make sure that different instances of the simulator, + // possibly started by a script on the same machine, are seeded differently. + // Vendors of the actual TPMs need to ensure availability of proper entropy + // using their platform specific means. + // + // NOTE 2: In debug builds by default the reference implementation will seed + // its RNG deterministically (without using any platform provided randomness). + // See the USE_DEBUG_RNG macro and DRBG_GetEntropy() function. +#ifdef _MSC_VER + srand((unsigned)_plat__RealTime() ^ _getpid()); +#else + srand((unsigned)_plat__RealTime() ^ getpid()); +#endif + lastEntropy = rand32(); + ret = 0; + } + else + { + rndNum = rand32(); + if(rndNum == lastEntropy) + { + ret = -1; + } + else + { + lastEntropy = rndNum; + // Each process will have its random number generator initialized according + // to the process id and the initialization time. This is not a lot of + // entropy so, to add a bit more, XOR the current time value into the + // returned entropy value. + // NOTE: the reason for including the time here rather than have it in + // in the value assigned to lastEntropy is that rand() could be broken and + // using the time would in the lastEntropy value would hide this. + rndNum ^= (uint32_t)_plat__RealTime(); + // Only provide entropy 32 bits at a time to test the ability + // of the caller to deal with partial results. + ret = MIN(amount, sizeof(rndNum)); + memcpy(entropy, &rndNum, ret); + } + } + return ret; +} + |