Add current version of libSRTP from CVS.

libsrtp/crypto/rng/prng.c

+/*
+ * prng.c 
+ *
+ * pseudorandom source
+ *
+ * David A. McGrew
+ * Cisco Systems, Inc.
+ */
+/*
+ *      
+ * Copyright(c) 2001-2006 Cisco Systems, Inc.
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ *   Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ * 
+ *   Neither the name of the Cisco Systems, Inc. nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+
+#include "prng.h"
+
+/* single, global prng structure */
+
+x917_prng_t x917_prng;
+
+err_status_t
+x917_prng_init(rand_source_func_t random_source) {
+  uint8_t tmp_key[16];
+  err_status_t status;
+
+  /* initialize output count to zero */
+  x917_prng.octet_count = 0;
+
+  /* set random source */
+  x917_prng.rand = random_source;
+  
+  /* initialize secret key from random source */
+  status = random_source(tmp_key, 16);
+  if (status) 
+    return status;
+
+  /* expand aes key */
+  aes_expand_encryption_key(tmp_key, 16, &x917_prng.key);
+
+  /* initialize prng state from random source */
+  status = x917_prng.rand((uint8_t *)&x917_prng.state, 16);
+  if (status) 
+    return status;
+
+  return err_status_ok;
+}
+
+err_status_t
+x917_prng_get_octet_string(uint8_t *dest, uint32_t len) {
+  uint32_t t;
+  v128_t buffer;
+  uint32_t i, tail_len;
+  err_status_t status;
+
+  /* 
+   * if we need to re-initialize the prng, do so now 
+   *
+   * avoid overflows by subtracting instead of adding
+   */
+  if (x917_prng.octet_count > MAX_PRNG_OUT_LEN - len) {
+    status = x917_prng_init(x917_prng.rand);    
+    if (status)
+      return status;
+  }
+  x917_prng.octet_count += len;
+  
+  /* find out the time */
+  t = (uint32_t)time(NULL);
+  
+  /* loop until we have output enough data */
+  for (i=0; i < len/16; i++) {
+    
+    /* exor time into state */
+    x917_prng.state.v32[0] ^= t; 
+ 
+    /* copy state into buffer */
+    v128_copy(&buffer, &x917_prng.state);
+
+    /* apply aes to buffer */
+    aes_encrypt(&buffer, &x917_prng.key);
+    
+    /* write data to output */
+    *dest++ = buffer.v8[0];
+    *dest++ = buffer.v8[1];
+    *dest++ = buffer.v8[2];
+    *dest++ = buffer.v8[3];
+    *dest++ = buffer.v8[4];
+    *dest++ = buffer.v8[5];
+    *dest++ = buffer.v8[6];
+    *dest++ = buffer.v8[7];
+    *dest++ = buffer.v8[8];
+    *dest++ = buffer.v8[9];
+    *dest++ = buffer.v8[10];
+    *dest++ = buffer.v8[11];
+    *dest++ = buffer.v8[12];
+    *dest++ = buffer.v8[13];
+    *dest++ = buffer.v8[14];
+    *dest++ = buffer.v8[15];
+
+    /* exor time into buffer */
+    buffer.v32[0] ^= t;
+
+    /* encrypt buffer */
+    aes_encrypt(&buffer, &x917_prng.key);
+
+    /* copy buffer into state */
+    v128_copy(&x917_prng.state, &buffer);
+    
+  }
+  
+  /* if we need to output any more octets, we'll do so now */
+  tail_len = len % 16;
+  if (tail_len) {
+    
+    /* exor time into state */
+    x917_prng.state.v32[0] ^= t; 
+ 
+    /* copy value into buffer */
+    v128_copy(&buffer, &x917_prng.state);
+
+    /* apply aes to buffer */
+    aes_encrypt(&buffer, &x917_prng.key);
+
+    /* write data to output */
+    for (i=0; i < tail_len; i++) {
+      *dest++ = buffer.v8[i];
+    }
+
+    /* now update the state one more time */
+
+    /* exor time into buffer */
+    buffer.v32[0] ^= t;
+
+    /* encrypt buffer */
+    aes_encrypt(&buffer, &x917_prng.key);
+
+    /* copy buffer into state */
+    v128_copy(&x917_prng.state, &buffer);
+
+  }
+  
+  return err_status_ok;
+}
+
+err_status_t
+x917_prng_deinit(void) {
+  
+  return err_status_ok;  
+}