From 43655f46b0e44a7ef16c7c4e14990a201a9b01fc Mon Sep 17 00:00:00 2001
From: Paul Bakker <p.j.bakker@polarssl.org>
Date: Thu, 15 Dec 2011 20:11:16 +0000
Subject: [PATCH]  - Added option to prevent default entropy sources from
 loading (POLARSSL_NO_DEFAULT_ENTROPY_SOURCES)

---
 include/polarssl/config.h  | 13 +++++++++++++
 include/polarssl/entropy.h |  3 ++-
 include/polarssl/error.h   |  2 +-
 library/entropy.c          |  9 ++++++++-
 library/error.c            |  2 ++
 5 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index 1327c431f..ea518d77d 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -154,6 +154,19 @@
  */
 #define POLARSSL_FS_IO
 
+/**
+ * \def POLARSSL_NO_DEFAULT_ENTROPY_SOURCES
+ *
+ * Do not add default entropy sources. These are the platform specific,
+ * hardclock and HAVEGE based poll functions.
+ *
+ * This is useful to have more control over the added entropy sources in an 
+ * application.
+ *
+ * Uncomment this macro to prevent loading of default entropy functions.
+#define POLARSSL_NO_DEFAULT_ENTROPY_SOURCES
+ */
+
 /**
  * \def POLARSSL_NO_PLATFORM_ENTROPY
  *
diff --git a/include/polarssl/entropy.h b/include/polarssl/entropy.h
index 6dea79a71..53bce41b0 100644
--- a/include/polarssl/entropy.h
+++ b/include/polarssl/entropy.h
@@ -38,6 +38,7 @@
 
 #define POLARSSL_ERR_ENTROPY_SOURCE_FAILED                 -0x003C  /**< Critical entropy source failure. */
 #define POLARSSL_ERR_ENTROPY_MAX_SOURCES                   -0x003E  /**< No more sources can be added. */
+#define POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040  /**< No sources have been added to poll. */
 
 #define ENTROPY_MAX_SOURCES     20      /**< Maximum number of sources supported */
 #define ENTROPY_MAX_GATHER      128     /**< Maximum amount requested from entropy sources */
@@ -104,7 +105,7 @@ void entropy_init( entropy_context *ctx );
  * \param threshold Minimum required from source before entropy is released
  *                  ( with entropy_func() )
  *
- * \return          0 is successful or POLARSSL_ERR_ENTROPY_MAX_SOURCES
+ * \return          0 if successful or POLARSSL_ERR_ENTROPY_MAX_SOURCES
  */
 int entropy_add_source( entropy_context *ctx,
                         f_source_ptr f_source, void *p_source,
diff --git a/include/polarssl/error.h b/include/polarssl/error.h
index f167a7b83..78ad36255 100644
--- a/include/polarssl/error.h
+++ b/include/polarssl/error.h
@@ -58,7 +58,7 @@
  * DES       1  0x0032-0x0032
  * NET      11  0x0040-0x0054
  * CTR_DBRG  3  0x0034-0x003A
- * ENTROPY   2  0x003C-0x003E
+ * ENTROPY   3  0x003C-0x0040
  * MD2       1  0x0070-0x0070
  * MD4       1  0x0072-0x0072
  * MD5       1  0x0074-0x0074
diff --git a/library/entropy.c b/library/entropy.c
index ebace0881..966245472 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -41,7 +41,11 @@ void entropy_init( entropy_context *ctx )
     memset( ctx, 0, sizeof(entropy_context) );
 
     sha4_starts( &ctx->accumulator, 0 );
+#if defined(POLARSSL_HAVEGE_C)
+    havege_init( &ctx->havege_data );
+#endif
 
+#if !defined(POLARSSL_NO_DEFAULT_ENTROPY_SOURCES)
 #if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
     entropy_add_source( ctx, platform_entropy_poll, NULL,
                         ENTROPY_MIN_PLATFORM );
@@ -50,10 +54,10 @@ void entropy_init( entropy_context *ctx )
     entropy_add_source( ctx, hardclock_poll, NULL, ENTROPY_MIN_HARDCLOCK );
 #endif
 #if defined(POLARSSL_HAVEGE_C)
-    havege_init( &ctx->havege_data );
     entropy_add_source( ctx, havege_poll, &ctx->havege_data,
                         ENTROPY_MIN_HAVEGE );
 #endif
+#endif /* POLARSSL_NO_DEFAULT_ENTROPY_SOURCES */
 }
 
 int entropy_add_source( entropy_context *ctx,
@@ -117,6 +121,9 @@ int entropy_gather( entropy_context *ctx )
     unsigned char buf[ENTROPY_MAX_GATHER];
     size_t olen;
     
+    if( ctx->source_count == 0 )
+        return( POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED );
+
     /*
      * Run through our entropy sources
      */
diff --git a/library/error.c b/library/error.c
index 05e84e72c..5dcd17580 100644
--- a/library/error.c
+++ b/library/error.c
@@ -436,6 +436,8 @@ void error_strerror( int ret, char *buf, size_t buflen )
         snprintf( buf, buflen, "ENTROPY - Critical entropy source failure" );
     if( use_ret == -(POLARSSL_ERR_ENTROPY_MAX_SOURCES) )
         snprintf( buf, buflen, "ENTROPY - No more sources can be added" );
+    if( use_ret == -(POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED) )
+        snprintf( buf, buflen, "ENTROPY - No sources have been added to poll" );
 #endif /* POLARSSL_ENTROPY_C */
 
 #if defined(POLARSSL_MD2_C)