Increase strictness of NULL parameter validity in Cipher's doxygen
diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 3c6077b..dc76443 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -600,9 +600,8 @@
*
* \param ctx The generic cipher context. This must be initialized and
* bound to a cipher information structure.
- * \param iv The IV to use, or NONCE_COUNTER for CTR-mode ciphers. If
- * `iv_len > 0`, this may be \c NULL, otherwise this must be a
- * readable buffer of at least \p iv_len Bytes.
+ * \param iv The IV to use, or NONCE_COUNTER for CTR-mode ciphers. This
+ * must be a readable buffer of at least \p iv_len Bytes.
* \param iv_len The IV length for ciphers with variable-size IV.
* This parameter is discarded by ciphers with fixed-size IV.
*
@@ -633,9 +632,8 @@
* mbedtls_cipher_reset().
*
* \param ctx The generic cipher context. This must be initialized.
- * \param ad The additional data to use. If `ad_len > 0`, then this
- * must be a readable buffer of at least \p ad_len Bytes,
- * otherwise this may be \c NULL.
+ * \param ad The additional data to use. This must be a readable
+ * buffer of at least \p ad_len Bytes.
* \param ad_len the Length of \p ad Bytes.
*
* \return \c 0 on success.
@@ -663,8 +661,7 @@
* \param ctx The generic cipher context. This must be initialized and
* bound to a key.
* \param input The buffer holding the input data. This must be a
- * readable buffer of at least \p ilen Bytes. If
- * `ilen == 0`, this may be \c NULL.
+ * readable buffer of at least \p ilen Bytes.
* \param ilen The length of the input data.
* \param output The buffer for the output data. This must be able to
* hold at least `ilen + block_size`. This must not be the
@@ -719,8 +716,7 @@
* operation through mbedtls_cipher_finish() the tag for
* which should be written.
* \param tag The buffer to write the tag to. This must be a writable
- * buffer of at least \p tag_len Bytes. If `tag_len == 0`,
- * this may be \c NULL.
+ * buffer of at least \p tag_len Bytes.
* \param tag_len The length of the tag to write.
*
* \return \c 0 on success.
@@ -735,9 +731,8 @@
* This must be called after mbedtls_cipher_finish().
*
* \param ctx The generic cipher context. This must be initialized.
- * \param tag The buffer holding the tag. If `tag_len > 0`, then this
- * must be a readable buffer of at least \p tag_len Bytes,
- * otherwise this may be \c NULL.
+ * \param tag The buffer holding the tag. This must be a readable
+ * buffer of at least \p tag_len Bytes.
* \param tag_len The length of the tag to check.
*
* \return \c 0 on success.
@@ -753,14 +748,13 @@
*
* \param ctx The generic cipher context. This must be initialized.
* \param iv The IV to use, or NONCE_COUNTER for CTR-mode ciphers.
- * If `iv_len > 0`, this must be a readable buffer of at
- * least \p iv_len Bytes, otherwise this may be \c NULL.
+ * This must be a readable buffer of at least \p iv_len
+ * Bytes.
* \param iv_len The IV length for ciphers with variable-size IV.
* This parameter is discarded by ciphers with fixed-size
* IV.
- * \param input The buffer holding the input data. If `ilen > 0`, then
- * this must be a readable buffer of at least \p ilen
- * Bytes, otherwise this may be \c NULL.
+ * \param input The buffer holding the input data. This must be a
+ * readable buffer of at least \p ilen Bytes.
* \param ilen The length of the input data in Bytes.
* \param output The buffer for the output data. This must be able to
* hold at least `ilen + block_size`. This must not be the
@@ -797,22 +791,19 @@
* Bytes.
* \param iv_len The IV length for ciphers with variable-size IV.
* This parameter is discarded by ciphers with fixed-size IV.
- * \param ad The additional data to authenticate. If `ad_len > 0`,
- * this must be a readable buffer of at least \p ad_len
- * Bytes, otherwise this may be \c NULL.
+ * \param ad The additional data to authenticate. This must be a
+ * readable buffer of at least \p ad_len Bytes.
* \param ad_len The length of \p ad.
- * \param input The buffer holding the input data. If `ilen > 0`, then
- * this must be a readable buffer of at least \p ilen
- * Bytes, otherwise this may be \c NULL.
+ * \param input The buffer holding the input data. This must be a
+ * readable buffer of at least \p ilen Bytes.
* \param ilen The length of the input data.
* \param output The buffer for the output data. This must be able to
* hold at least \p ilen Bytes.
* \param olen The length of the output data, to be updated with the
* actual number of Bytes written. This must not be
* \c NULL.
- * \param tag The buffer for the authentication tag. If `tag_len > 0`,
- * then this must be a writable buffer of at least
- * \p tag_len Bytes, otherwise this may be \c NULL.
+ * \param tag The buffer for the authentication tag. This must be a
+ * writable buffer of at least \p tag_len Bytes.
* \param tag_len The desired length of the authentication tag.
*
* \return \c 0 on success.
@@ -841,22 +832,19 @@
* Bytes.
* \param iv_len The IV length for ciphers with variable-size IV.
* This parameter is discarded by ciphers with fixed-size IV.
- * \param ad The additional data to be authenticated. If `ad_len > 0`,
- * this must be a readable buffer of at least \p ad_len
- * Bytes, otherwise this may be \c NULL.
+ * \param ad The additional data to be authenticated. This must be a
+ * readable buffer of at least \p ad_len Bytes.
* \param ad_len The length of \p ad.
- * \param input The buffer holding the input data. If `ilen > 0`, then
- * this must be a readable buffer of at least \p ilen
- * Bytes, otherwise, this may be \c NULL.
+ * \param input The buffer holding the input data. This must be a
+ * readable buffer of at least \p ilen Bytes.
* \param ilen The length of the input data.
* \param output The buffer for the output data.
* This must be able to hold at least \p ilen Bytes.
* \param olen The length of the output data, to be updated with the
* actual number of Bytes written. This must not be
* \c NULL.
- * \param tag The buffer holding the authentication tag. If
- * `tag_len > 0`, then this must be a readable buffer of at
- * least \p tag_len Bytes, otherwise this can be \c NULL.
+ * \param tag The buffer holding the authentication tag. This must be
+ * a readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the authentication tag.
*
* \return \c 0 on success.