Merge remote-tracking branch 'origin/mbedtls-2.16' into mbedtls-2.16-restricted

* origin/mbedtls-2.16:
  Fix some pylint warnings
  Enable more test cases without MBEDTLS_MEMORY_DEBUG
  More accurate test case description
  Clarify that the "FATAL" message is expected
  Note that mbedtls_ctr_drbg_seed() must not be called twice
  Fix CTR_DRBG benchmark
  Changelog entry for xxx_drbg_set_entropy_len before xxx_drbg_seed
  CTR_DRBG: support set_entropy_len() before seed()
  CTR_DRBG: Don't use functions before they're defined
  HMAC_DRBG: support set_entropy_len() before seed()

include/mbedtls/ctr_drbg.h

@@ -214,11 +214,8 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
  *   with mbedtls_entropy_init() (which registers the platform's default
  *   entropy sources).
  *
- * \p f_entropy is always called with a buffer size equal to the entropy
- * length. The entropy length is initially #MBEDTLS_CTR_DRBG_ENTROPY_LEN
- * and this value is always used for the initial seeding. You can change
- * the entropy length for subsequent seeding by calling
- * mbedtls_ctr_drbg_set_entropy_len() after this function.
+ * The entropy length is #MBEDTLS_CTR_DRBG_ENTROPY_LEN by default.
+ * You can override it by calling mbedtls_ctr_drbg_set_entropy_len().
  *
  * You can provide a personalization string in addition to the
  * entropy source, to make this instantiation as unique as possible.
@@ -252,9 +249,18 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
 #endif
 /**
  * \param ctx           The CTR_DRBG context to seed.
+ *                      It must have been initialized with
+ *                      mbedtls_ctr_drbg_init().
+ *                      After a successful call to mbedtls_ctr_drbg_seed(),
+ *                      you may not call mbedtls_ctr_drbg_seed() again on
+ *                      the same context unless you call
+ *                      mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init()
+ *                      again first.
  * \param f_entropy     The entropy callback, taking as arguments the
  *                      \p p_entropy context, the buffer to fill, and the
  *                      length of the buffer.
+ *                      \p f_entropy is always called with a buffer size
+ *                      equal to the entropy length.
  * \param p_entropy     The entropy context to pass to \p f_entropy.
  * \param custom        The personalization string.
  *                      This can be \c NULL, in which case the personalization
@@ -298,15 +304,10 @@ void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
 
 /**
  * \brief               This function sets the amount of entropy grabbed on each
- *                      subsequent reseed.
+ *                      seed or reseed.
  *
  * The default value is #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
  *
- * \note                mbedtls_ctr_drbg_seed() always sets the entropy length
- *                      to #MBEDTLS_CTR_DRBG_ENTROPY_LEN, so this function
- *                      only has an effect when it is called after
- *                      mbedtls_ctr_drbg_seed().
- *
  * \note                The security strength of CTR_DRBG is bounded by the
  *                      entropy length. Thus:
  *                      - When using AES-256

include/mbedtls/hmac_drbg.h

@@ -139,13 +139,11 @@ void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
  *                      Note that SHA-256 is just as efficient as SHA-224.
  *                      The security strength can be reduced if a smaller
  *                      entropy length is set with
- *                      mbedtls_hmac_drbg_set_entropy_len() afterwards.
+ *                      mbedtls_hmac_drbg_set_entropy_len().
  *
- * \note                The entropy length for the initial seeding is
- *                      the security strength (converted from bits to bytes).
- *                      You can set a different entropy length for subsequent
- *                      seeding by calling mbedtls_hmac_drbg_set_entropy_len()
- *                      after this function.
+ * \note                The default entropy length is the security strength
+ *                      (converted from bits to bytes). You can override
+ *                      it by calling mbedtls_hmac_drbg_set_entropy_len().
  *
  * \note                During the initial seeding, this function calls
  *                      the entropy source to obtain a nonce
@@ -224,14 +222,9 @@ void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx
 
 /**
  * \brief               This function sets the amount of entropy grabbed on each
- *                      reseed.
+ *                      seed or reseed.
  *
- * The default value is set by mbedtls_hmac_drbg_seed().
- *
- * \note                mbedtls_hmac_drbg_seed() always sets the entropy length
- *                      to the default value based on the chosen MD algorithm,
- *                      so this function only has an effect if it is called
- *                      after mbedtls_hmac_drbg_seed().
+ * See the documentation of mbedtls_hmac_drbg_seed() for the default value.
  *
  * \param ctx           The HMAC_DRBG context.
  * \param len           The amount of entropy to grab, in bytes.