1 files changed, 108 insertions, 0 deletions
diff --git a/srtp/crypto/rng/ctr_prng.c b/srtp/crypto/rng/ctr_prng.c
new file mode 100644
index 0000000..ab76df3
--- /dev/null
+++ b/srtp/crypto/rng/ctr_prng.c
@@ -0,0 +1,108 @@
+/*
+ * ctr_prng.c 
+ *
+ * counter mode based 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 */
+
+ctr_prng_t ctr_prng;
+
+err_status_t
+ctr_prng_init(rand_source_func_t random_source) {
+  uint8_t tmp_key[32];
+  err_status_t status;
+
+  /* initialize output count to zero */
+  ctr_prng.octet_count = 0;
+
+  /* set random source */
+  ctr_prng.rand = random_source;
+  
+  /* initialize secret key from random source */
+  status = random_source(tmp_key, 32);
+  if (status) 
+    return status;
+
+  /* initialize aes ctr context with random key */
+  status = aes_icm_context_init(&ctr_prng.state, tmp_key);
+  if (status) 
+    return status;
+
+  return err_status_ok;
+}
+
+err_status_t
+ctr_prng_get_octet_string(void *dest, uint32_t len) {
+  err_status_t status;
+
+  /* 
+   * if we need to re-initialize the prng, do so now 
+   *
+   * avoid 32-bit overflows by subtracting instead of adding
+   */
+  if (ctr_prng.octet_count > MAX_PRNG_OUT_LEN - len) {
+    status = ctr_prng_init(ctr_prng.rand);    
+    if (status)
+      return status;
+  }
+  ctr_prng.octet_count += len;
+
+  /*
+   * write prng output 
+   */
+  status = aes_icm_output(&ctr_prng.state, (uint8_t*)dest, len);
+  if (status)
+    return status;
+  
+  return err_status_ok;
+}
+
+err_status_t
+ctr_prng_deinit(void) {
+
+  /* nothing */
+  
+  return err_status_ok;  
+}