Clarify the need for a PRNG in various RSA operations
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index b87c79d..5171fc9 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -588,9 +588,12 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initialized RSA context to use.
- * \param f_rng This is the RNG function used to generate the
- * PKCS#1 v2.1 padding encoding if \p mode is
- * #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG to use. If PKCS#1 v2.1 padding encoding is
+ * used, this must be provided. Additionally, it is
+ * used for blinding if \p mode is #MBEDTLS_RSA_PRIVATE
+ * and should be provided in this case; see
+ * mbedtls_rsa_private() for more. It is ignored
+ * for PKCS#1 v1.5 padding with #MBEDTLS_RSA_PUBLIC.
* \param p_rng The RNG context to be passed to \p f_rng. May be
* \c NULL if \p f_rng is \c NULL or if \p f_rng doesn't
* need a context argument.
@@ -628,8 +631,10 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initialized RSA context to use.
- * \param f_rng The RNG function, needed for padding generation if
- * \p mode is #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG function to use. It is needed for padding generation
+ * if \p mode is #MBEDTLS_RSA_PUBLIC. If \p mode is
+ * #MBEDTLS_RSA_PRIVATE (discouraged), it is used for
+ * blinding and should be provided; see mbedtls_rsa_private().
* \param p_rng The RNG context to be passed to \p f_rng. This may
* be \c NULL if \p f_rng is \c NULL or if \p f_rng
* doesn't need a context argument.
@@ -670,11 +675,10 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initnialized RSA context to use.
- * \param f_rng The RNG function, needed for padding and PKCS#1 v2.1
- * encoding if \p mode is #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG function to use. This is needed for padding
+ * generation and must be provided.
* \param p_rng The RNG context to be passed to \p f_rng. This may
- * be \c NULL if \p f_rng is \c NULL or if \p f_rng
- * doesn't need a context argument.
+ * be \c NULL if \p f_rng doesn't need a context argument.
* \param mode The mode of operation. This must be either
* #MBEDTLS_RSA_PUBLIC or #MBEDTLS_RSA_PRIVATE (deprecated).
* \param label The buffer holding the custom label to use.
@@ -883,10 +887,11 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initialized RSA context to use.
- * \param f_rng The RNG function. If the padding mode is PKCS#1 v2.1
- * and \p mode is set to #MBEDTLS_RSA_PRIVATE, it is used for
- * blinding and should be provided; see mbedtls_rsa_private().
- * It is ignored otherwise.
+ * \param f_rng The RNG function to use. If the padding mode is PKCS#1 v2.1,
+ * this must be provided. If the padding mode is PKCS#1 v1.5 and
+ * \p mode is #MBEDTLS_RSA_PRIVATE, it is used for blinding
+ * and should be provided; see mbedtls_rsa_private() for more
+ * more. It is ignored otherwise.
* \param p_rng The RNG context to be passed to \p f_rng. This may be \c NULL
* if \p f_rng is \c NULL or doesn't need a context argument.
* \param mode The mode of operation. This must be either
@@ -1045,8 +1050,9 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initialized RSA public key context to use.
- * \param f_rng The RNG function to use. This is only needed if
- * \p mode is #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG function to use. If \p mode is #MBEDTLS_RSA_PRIVATE,
+ * this is used for blinding and should be provided; see
+ * mbedtls_rsa_private() for more. Otherwise, it is ignored.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng is \c NULL or doesn't need a context.
* \param mode The mode of operation. This must be either
@@ -1090,8 +1096,9 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initialized RSA public key context to use.
- * \param f_rng The RNG function to use. This is only needed if
- * \p mode is #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG function to use. If \p mode is #MBEDTLS_RSA_PRIVATE,
+ * this is used for blinding and should be provided; see
+ * mbedtls_rsa_private() for more. Otherwise, it is ignored.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng is \c NULL or doesn't need a context.
* \param mode The mode of operation. This must be either
@@ -1146,8 +1153,9 @@
* return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
*
* \param ctx The initialized RSA public key context to use.
- * \param f_rng The RNG function to use. This is only needed if
- * \p mode is #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG function to use. If \p mode is #MBEDTLS_RSA_PRIVATE,
+ * this is used for blinding and should be provided; see
+ * mbedtls_rsa_private() for more. Otherwise, it is ignored.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng is \c NULL or doesn't need a context.
* \param mode The mode of operation. This must be either
@@ -1190,8 +1198,9 @@
* \note The \p hash_id in the RSA context is ignored.
*
* \param ctx The initialized RSA public key context to use.
- * \param f_rng The RNG function to use. This is only needed if
- * \p mode is #MBEDTLS_RSA_PRIVATE.
+ * \param f_rng The RNG function to use. If \p mode is #MBEDTLS_RSA_PRIVATE,
+ * this is used for blinding and should be provided; see
+ * mbedtls_rsa_private() for more. Otherwise, it is ignored.
* \param p_rng The RNG context to be passed to \p f_rng. This may be
* \c NULL if \p f_rng is \c NULL or doesn't need a context.
* \param mode The mode of operation. This must be either