BeRTOS
randpool.c
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00001 
00038 #include "randpool.h"
00039 #include "md2.h"
00040 
00041 #include <cfg/compiler.h>
00042 #include <cfg/debug.h>       //ASSERT()
00043 #include <cfg/macros.h>      //MIN(), ROUND_UP();
00044 
00045 #include <stdio.h>           //sprintf();
00046 #include <string.h>          //memset(), memcpy();
00047 
00048 #if CONFIG_RANDPOOL_TIMER
00049     #include <drv/timer.h>       //timer_clock();
00050 #endif
00051 
00052 
00053 
00054 /*
00055  * Insert bytes in entropy pool, making a XOR of bytes present
00056  * in entropy pool.
00057  */
00058 static void randpool_push(EntropyPool *pool, void *_byte, size_t n_byte)
00059 {
00060     size_t i = pool->pos_add; // Current number of byte insert in entropy pool.
00061     uint8_t *byte;
00062 
00063     byte = (uint8_t *)_byte;
00064 
00065     /*
00066      * Insert a bytes in entropy pool.
00067      */
00068     for(size_t j = 0; j < n_byte; j++)
00069     {
00070         pool->pool_entropy[i] = pool->pool_entropy[i] ^ byte[j];
00071         i++;
00072         i = i % CONFIG_SIZE_ENTROPY_POOL;
00073     }
00074 
00075     pool->pos_add  =  i; // Update a insert bytes.
00076 }
00077 
00078 
00079 /*
00080  * This function stir entropy pool with MD2 function hash.
00081  *
00082  */
00083 static void randpool_stir(EntropyPool *pool)
00084 {
00085     size_t entropy = pool->entropy; //Save current calue of entropy.
00086     Md2Context context;
00087     uint8_t tmp_buf[((sizeof(size_t) * 2) + sizeof(int)) * 2 + 1]; //Temporary buffer.
00088 
00089     md2_init(&context); //Init MD2 algorithm.
00090 
00091     randpool_add(pool, NULL, 0);
00092 
00093     for (int i = 0; i < (CONFIG_SIZE_ENTROPY_POOL / MD2_DIGEST_LEN); i++)
00094     {
00095         sprintf((char *)tmp_buf, "%0x%0x%0x", pool->counter, i, pool->pos_add);
00096 
00097         /*
00098          * Hash with MD2 algorithm the entropy pool.
00099          */
00100         md2_update(&context, pool->pool_entropy, CONFIG_SIZE_ENTROPY_POOL);
00101 
00102         md2_update(&context, tmp_buf, sizeof(tmp_buf) - 1);
00103 
00104         /*Insert a message digest in entropy pool.*/
00105         randpool_push(pool, md2_end(&context), MD2_DIGEST_LEN);
00106 
00107         pool->counter = pool->counter + 1;
00108 
00109     }
00110 
00111     /*Insert in pool the difference between a two call of this function (see above).*/
00112     randpool_add(pool, NULL, 0);
00113 
00114     pool->entropy = entropy; //Restore old value of entropy. We haven't add entropy.
00115 }
00116 
00120 void randpool_add(EntropyPool *pool, void *data, size_t entropy)
00121 {
00122     uint8_t sep[] = "\xaa\xaa\xaa\xaa";  // ??
00123     size_t data_len = ROUND_UP(entropy, 8) / 8; //Number of entropy byte in input.
00124 
00125     randpool_push(pool, data, data_len); //Insert data to entropy pool.
00126 
00127 #if CONFIG_RANDPOOL_TIMER
00128 
00129     ticks_t event = timer_clock();
00130     ticks_t delta;
00131 
00132     /*Difference of time between a two accese to entropy pool.*/
00133     delta = event - pool->last_counter;
00134 
00135     randpool_push(pool, &event, sizeof(ticks_t));
00136     randpool_push(pool, sep, sizeof(sep) - 1); // ??
00137     randpool_push(pool, &delta, sizeof(delta));
00138 
00139     /*
00140      * Count of number entropy bit add with delta.
00141      */
00142     delta = delta & 0xff;
00143     while(delta)
00144     {
00145         delta >>= 1;
00146         entropy++;
00147     }
00148 
00149     pool->last_counter = event;
00150 
00151 #endif
00152 
00153     pool->entropy += entropy;      //Update a entropy of the pool.
00154 }
00155 
00161 void randpool_init(EntropyPool *pool, void *_data, size_t len)
00162 {
00163     uint8_t *data;
00164 
00165     data = (uint8_t *)_data;
00166 
00167     memset(pool, 0, sizeof(EntropyPool));
00168     pool->pos_get = MD2_DIGEST_LEN;
00169 
00170 #if CONFIG_RANDPOOL_TIMER
00171     pool->last_counter = timer_clock();
00172 #endif
00173 
00174     if(data)
00175     {
00176         /*
00177          * Initialize a entropy pool with a
00178          * previous pool, and assume all pool as
00179          * entropy.
00180          */
00181         len = MIN(len,(size_t)CONFIG_SIZE_ENTROPY_POOL);
00182         memcpy(pool->pool_entropy, data, len);
00183         pool->entropy = len;
00184     }
00185 
00186 }
00187 
00191 size_t randpool_size(EntropyPool *pool)
00192 {
00193     return pool->entropy;
00194 }
00195 
00205 void randpool_get(EntropyPool *pool, void *_data, size_t n_byte)
00206 {
00207     Md2Context context;
00208     size_t i = pool->pos_get;
00209     size_t n = n_byte;
00210     size_t pos_write = 0;  //Number of block has been written in data.
00211     size_t len = MIN((size_t)MD2_DIGEST_LEN, n_byte);
00212     uint8_t *data;
00213 
00214     data = (uint8_t *)_data;
00215 
00216     /* Test if i + CONFIG_MD2_BLOCK_LEN  is inside of entropy pool.*/
00217     ASSERT((MD2_DIGEST_LEN + i) <= CONFIG_SIZE_ENTROPY_POOL);
00218 
00219     md2_init(&context);
00220 
00221     while(n > 0)
00222     {
00223 
00224         /*Hash previous state of pool*/
00225         md2_update(&context, &pool->pool_entropy[i], MD2_DIGEST_LEN);
00226 
00227         memcpy(&data[pos_write], md2_end(&context), len);
00228 
00229         pos_write += len;   //Update number of block has been written in data.
00230         n -= len;           //Number of byte copied in data.
00231 
00232         len = MIN(n,(size_t)MD2_DIGEST_LEN);
00233 
00234         i = (i + MD2_DIGEST_LEN) % CONFIG_SIZE_ENTROPY_POOL;
00235 
00236         /* If we haven't more entropy pool to hash, we stir it.*/
00237         if(i < MD2_DIGEST_LEN)
00238         {
00239             randpool_stir(pool);
00240             i = pool->pos_get;
00241         }
00242 
00243     }
00244 
00245     pool->pos_get = i; //Current number of byte we get from pool.
00246     pool->entropy -= n_byte; //Update a entropy.
00247 
00248 }
00249 
00253 uint8_t *randpool_pool(EntropyPool *pool)
00254 {
00255     return pool->pool_entropy;
00256 }
00257