2 Copyright (c) 2006-2009, John Hurst
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28 \version $Id: KM_prng.cpp,v 1.9 2011/06/14 23:38:33 jhurst Exp $
29 \brief Fortuna pseudo-random number generator
37 #include <openssl/aes.h>
38 #include <openssl/sha.h>
39 #include <openssl/bn.h>
45 # include <wincrypt.h>
47 # include <KM_fileio.h>
48 const char* DEV_URANDOM = "/dev/urandom";
52 const ui32_t RNG_KEY_SIZE = 512UL;
53 const ui32_t RNG_KEY_SIZE_BITS = 256UL;
54 const ui32_t RNG_BLOCK_SIZE = 16UL;
55 const ui32_t MAX_SEQUENCE_LEN = 0x00040000UL;
58 // internal implementation class
61 KM_NO_COPY_CONSTRUCT(h__RNG);
65 byte_t m_ctr_buf[RNG_BLOCK_SIZE];
70 memset(m_ctr_buf, 0, RNG_BLOCK_SIZE);
71 byte_t rng_key[RNG_KEY_SIZE];
73 { // this block scopes the following AutoMutex so that it will be
74 // released before the call to set_key() below.
75 AutoMutex Lock(m_Lock);
78 HCRYPTPROV hProvider = 0;
79 CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
80 CryptGenRandom(hProvider, RNG_KEY_SIZE, rng_key);
82 // on POSIX systems we simply read some seed from /dev/urandom
85 Result_t result = URandom.OpenRead(DEV_URANDOM);
87 if ( KM_SUCCESS(result) )
90 result = URandom.Read(rng_key, RNG_KEY_SIZE, &read_count);
93 if ( KM_FAILURE(result) )
94 DefaultLogSink().Error("Error opening random device: %s\n", DEV_URANDOM);
97 } // end AutoMutex context
104 set_key(const byte_t* key_fodder)
111 SHA1_Update(&SHA, (byte_t*)&m_Context, sizeof(m_Context));
112 SHA1_Update(&SHA, key_fodder, RNG_KEY_SIZE);
113 SHA1_Final(sha_buf, &SHA);
115 AutoMutex Lock(m_Lock);
116 AES_set_encrypt_key(sha_buf, RNG_KEY_SIZE_BITS, &m_Context);
117 *(ui32_t*)(m_ctr_buf + 12) = 1;
122 fill_rand(byte_t* buf, ui32_t len)
124 assert(len <= MAX_SEQUENCE_LEN);
125 ui32_t gen_count = 0;
126 AutoMutex Lock(m_Lock);
128 while ( gen_count + RNG_BLOCK_SIZE <= len )
130 AES_encrypt(m_ctr_buf, buf + gen_count, &m_Context);
131 *(ui32_t*)(m_ctr_buf + 12) += 1;
132 gen_count += RNG_BLOCK_SIZE;
135 if ( len != gen_count ) // partial count needed?
137 byte_t tmp[RNG_BLOCK_SIZE];
138 AES_encrypt(m_ctr_buf, tmp, &m_Context);
139 memcpy(buf + gen_count, tmp, len - gen_count);
145 static h__RNG* s_RNG = 0;
148 //------------------------------------------------------------------------------------------
150 // Fortuna public interface
152 Kumu::FortunaRNG::FortunaRNG()
158 Kumu::FortunaRNG::~FortunaRNG() {}
162 Kumu::FortunaRNG::FillRandom(byte_t* buf, ui32_t len)
166 const byte_t* front_of_buffer = buf;
170 // 2^20 bytes max per seeding, use 2^19 to save
171 // room for generating reseed values
172 ui32_t gen_size = xmin(len, MAX_SEQUENCE_LEN);
173 s_RNG->fill_rand(buf, gen_size);
177 // re-seed the generator
178 byte_t rng_key[RNG_KEY_SIZE];
179 s_RNG->fill_rand(rng_key, RNG_KEY_SIZE);
180 s_RNG->set_key(rng_key);
183 return front_of_buffer;
188 Kumu::FortunaRNG::FillRandom(Kumu::ByteString& Buffer)
190 FillRandom(Buffer.Data(), Buffer.Capacity());
191 Buffer.Length(Buffer.Capacity());
192 return Buffer.Data();
195 //------------------------------------------------------------------------------------------
198 // FIPS 186-2 Sec. 3.1 as modified by Change 1, section entitled "General Purpose Random Number Generation"
200 Kumu::Gen_FIPS_186_Value(const byte_t* key, ui32_t key_size, byte_t* out_buf, ui32_t out_buf_len)
202 byte_t sha_buf[SHA_DIGEST_LENGTH];
203 ui32_t const xkey_len = 64; // 512/8
204 byte_t xkey[xkey_len];
205 BN_CTX* ctx1 = BN_CTX_new(); // used by BN_* functions
208 if ( key_size > xkey_len )
209 DefaultLogSink().Warn("Key too large for FIPS 186 seed, truncating to 64 bytes.\n");
212 memset(xkey, 0, xkey_len);
213 memcpy(xkey, key, xmin<ui32_t>(key_size, xkey_len));
215 if ( key_size < SHA_DIGEST_LENGTH )
216 key_size = SHA_DIGEST_LENGTH; // pad short key ( b < 160 )
218 // create the 2^b constant
219 BIGNUM c_2powb, c_2, c_b;
220 BN_init(&c_2powb); BN_init(&c_2); BN_init(&c_b);
221 BN_set_word(&c_2, 2);
222 BN_set_word(&c_b, key_size * 8);
223 BN_exp(&c_2powb, &c_2, &c_b, ctx1);
229 // step c -- x = G(t,xkey)
230 SHA1_Init(&SHA); // set t
231 SHA1_Update(&SHA, xkey, xkey_len);
233 ui32_t* buf_p = (ui32_t*)sha_buf;
234 *buf_p++ = KM_i32_BE(SHA.h0);
235 *buf_p++ = KM_i32_BE(SHA.h1);
236 *buf_p++ = KM_i32_BE(SHA.h2);
237 *buf_p++ = KM_i32_BE(SHA.h3);
238 *buf_p++ = KM_i32_BE(SHA.h4);
239 memcpy(out_buf, sha_buf, xmin<ui32_t>(out_buf_len, SHA_DIGEST_LENGTH));
241 if ( out_buf_len <= SHA_DIGEST_LENGTH )
244 out_buf_len -= SHA_DIGEST_LENGTH;
245 out_buf += SHA_DIGEST_LENGTH;
247 // step d -- XKEY = (1 + XKEY + x) mod 2^b
248 BIGNUM bn_tmp, bn_xkey, bn_x_n;
249 BN_init(&bn_tmp); BN_init(&bn_xkey); BN_init(&bn_x_n);
251 BN_bin2bn(xkey, key_size, &bn_xkey);
252 BN_bin2bn(sha_buf, SHA_DIGEST_LENGTH, &bn_x_n);
253 BN_add_word(&bn_xkey, 1); // xkey += 1
254 BN_add(&bn_tmp, &bn_xkey, &bn_x_n); // xkey += x
255 BN_mod(&bn_xkey, &bn_tmp, &c_2powb, ctx1); // xkey = xkey mod (2^b)
257 memset(xkey, 0, xkey_len);
258 ui32_t bn_buf_len = BN_num_bytes(&bn_xkey);
259 ui32_t idx = ( bn_buf_len < key_size ) ? key_size - bn_buf_len : 0;
260 BN_bn2bin(&bn_xkey, &xkey[idx]);