Add hmac_drbg_set_entropy_len()

include/polarssl/hmac_drbg.h

@@ -96,7 +96,7 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
                     size_t len );
 
 /**
- * \brief               Simplified HMAC_DRBG initialisation.
+ * \brief               Initilisation of simpified HMAC_DRBG (never reseeds).
  *                      (For use with deterministic ECDSA.)
  *
  * \param ctx           HMAC_DRBG context to be initialised
@@ -112,6 +112,16 @@ int hmac_drbg_init_buf( hmac_drbg_context *ctx,
                         const md_info_t * md_info,
                         const unsigned char *data, size_t data_len );
 
+/**
+ * \brief               Set the amount of entropy grabbed on each reseed
+ *                      (Default: HMAC_DRBG_ENTROPY_LEN)
+ *
+ * \param ctx           HMAC_DRBG context
+ * \param len           Amount of entropy to grab
+ */
+void hmac_drbg_set_entropy_len( hmac_drbg_context *ctx,
+                                size_t len );
+
 /**
  * \brief               HMAC_DRBG update state
  *

library/hmac_drbg.c

@@ -156,6 +156,14 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
     return( 0 );
 }
 
+/*
+ * Set entropy length grabbed for reseeds
+ */
+void hmac_drbg_set_entropy_len( hmac_drbg_context *ctx, size_t len )
+{
+    ctx->entropy_len = len;
+}
+
 /*
  * HMAC_DRBG random function with optional additional data (10.1.2.5)
  */