commit 6aceb51e439a2ee1760c2d3ce7db78f2a09e3d82
author Gavin Acquroff <gavina352@gmail.com> Sun Mar 01 17:06:11 2020 -0800
committer gacquroff <gavina352@gmail.com> Wed Nov 25 14:25:56 2020 -0800
tree a73ee07e6aac15a60b75c8c672f08fc7ff1734a8
parent 662deb38d61bb1fc6392c55a5134d1bd1a116118

Support set *_drbg reseed interval before seed

mbedtls_ctr_drbg_set_reseed_interval() and
mbedtls_hmac_drbg_set_reseed_interval() can now be called before
their seed functions and the reseed_interval value will persist.
Previously it would be overwritten with the default value.

*_drbg_reseed_interval is now set in init() and free().

mbedtls_ctr_drbg_free() and mbedtls_hmac_drbg_free() now
reset the drbg context to the state immediately after init().

Tests:
- Added test to check that DRBG reseeds when reseed_counter
reaches reseed_interval, if reseed_interval set before seed
and reseed_interval is less than MBEDTLS_CTR_DRBG_RESEED_INTERVAL.

Signed-off-by: gacquroff <gavina352@gmail.com>

library/ctr_drbg.c

diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index 54843a7..023aac5 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -55,11 +55,17 @@
      * See mbedtls_ctr_drbg_set_nonce_len(). */
     ctx->reseed_counter = -1;
 
+    ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
+
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_mutex_init( &ctx->mutex );
 #endif
 }
 
+/*
+ *  This function resets CTR_DRBG context to the state immediately
+ *  after initial call of mbedtls_ctr_drbg_init().
+ */
 void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx )
 {
     if( ctx == NULL )
@@ -70,6 +76,11 @@
 #endif
     mbedtls_aes_free( &ctx->aes_ctx );
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) );
+    ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
+    ctx->reseed_counter = -1;
+#if defined(MBEDTLS_THREADING_C)
+    mbedtls_mutex_init( &ctx->mutex );
+#endif
 }
 
 void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
@@ -468,8 +479,6 @@
                   (size_t) ctx->reseed_counter :
                   good_nonce_len( ctx->entropy_len ) );
 
-    ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
-
     /* Initialize with an empty key. */
     if( ( ret = mbedtls_aes_setkey_enc( &ctx->aes_ctx, key,
                                         MBEDTLS_CTR_DRBG_KEYBITS ) ) != 0 )

library/hmac_drbg.c

diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index aa3e251..25a0225 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -53,6 +53,8 @@
 {
     memset( ctx, 0, sizeof( mbedtls_hmac_drbg_context ) );
 
+    ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
+
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_mutex_init( &ctx->mutex );
 #endif
@@ -266,8 +268,6 @@
     ctx->f_entropy = f_entropy;
     ctx->p_entropy = p_entropy;
 
-    ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
-
     if( ctx->entropy_len == 0 )
     {
         /*
@@ -412,7 +412,8 @@
 }
 
 /*
- * Free an HMAC_DRBG context
+ *  This function resets HMAC_DRBG context to the state immediately
+ *  after initial call of mbedtls_hmac_drbg_init().
  */
 void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx )
 {
@@ -424,6 +425,10 @@
 #endif
     mbedtls_md_free( &ctx->md_ctx );
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_hmac_drbg_context ) );
+    ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
+#if defined(MBEDTLS_THREADING_C)
+    mbedtls_mutex_init( &ctx->mutex );
+#endif
 }
 
 #if defined(MBEDTLS_FS_IO)