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Split the maximum fragment length into two - an input and output MFL

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Since the server might want to have a different maximum fragment length
for the outgoing messages than the negotiated one - introduce a new way of
computing it. This commit also adds additional ssl-opt.sh tests ensuring
that the maximum fragment lengths are set as expected. 
mbedtls_ssl_get_max_frag_len() is now a deprecated function,
being an alias to mbedtls_ssl_get_output_max_frag_len(). The behaviour
of this function is the same as before.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
This commit is contained in:
Andrzej Kurek 2020-04-03 05:25:29 -04:00
parent d4a720f541
commit 90c6e84a9c
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GPG key ID: 89A90840DC388527
8 changed files with 328 additions and 40 deletions
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60
include/mbedtls/ssl.h
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@ -3523,18 +3523,61 @@ int mbedtls_ssl_get_record_expansion( const mbedtls_ssl_context *ssl );
#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
/**
* \brief Return the maximum fragment length (payload, in bytes).
* This is the value negotiated with peer if any,
* or the locally configured value.
* \brief Return the maximum fragment length (payload, in bytes) for
* the output buffer. For the client, this is the configured
* value. For the server, it is the minimum of two - the
* configured value and the negotiated one.
*
* \sa mbedtls_ssl_conf_max_frag_len()
* \sa mbedtls_ssl_get_max_record_payload()
*
* \param ssl SSL context
*
* \return Current maximum fragment length.
* \return Current maximum fragment length for the output buffer.
*/
size_t mbedtls_ssl_get_max_frag_len( const mbedtls_ssl_context *ssl );
size_t mbedtls_ssl_get_output_max_frag_len( const mbedtls_ssl_context *ssl );
/**
* \brief Return the maximum fragment length (payload, in bytes) for
* the input buffer. This is the negotiated maximum fragment
* length, or, if there is none, MBEDTLS_SSL_MAX_CONTENT_LEN.
* If it is not defined either, the value is 2^14. This function
* works as its predecessor, \c mbedtls_ssl_get_max_frag_len().
*
* \sa mbedtls_ssl_conf_max_frag_len()
* \sa mbedtls_ssl_get_max_record_payload()
*
* \param ssl SSL context
*
* \return Current maximum fragment length for the output buffer.
*/
size_t mbedtls_ssl_get_input_max_frag_len( const mbedtls_ssl_context *ssl );
#if !defined(MBEDTLS_DEPRECATED_REMOVED)
#if defined(MBEDTLS_DEPRECATED_WARNING)
#define MBEDTLS_DEPRECATED __attribute__((deprecated))
#else
#define MBEDTLS_DEPRECATED
#endif
/**
* \brief This function is a deprecated approach to getting the max
* fragment length. Its an alias for
* \c mbedtls_ssl_get_output_max_frag_len(), as the behaviour
* is the same. See \c mbedtls_ssl_get_output_max_frag_len() for
* more detail.
*
* \sa mbedtls_ssl_get_input_max_frag_len()
* \sa mbedtls_ssl_get_output_max_frag_len()
*
* \param ssl SSL context
*
* \return Current maximum fragment length for the output buffer.
*/
MBEDTLS_DEPRECATED size_t mbedtls_ssl_get_max_frag_len(
const mbedtls_ssl_context *ssl );
#endif /* MBEDTLS_DEPRECATED_REMOVED */
#endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
/**
@ -3555,7 +3598,8 @@ size_t mbedtls_ssl_get_max_frag_len( const mbedtls_ssl_context *ssl );
* when record compression is enabled.
*
* \sa mbedtls_ssl_set_mtu()
* \sa mbedtls_ssl_get_max_frag_len()
* \sa mbedtls_ssl_get_output_max_frag_len()
* \sa mbedtls_ssl_get_input_max_frag_len()
* \sa mbedtls_ssl_get_record_expansion()
*
* \param ssl SSL context
@ -3863,8 +3907,8 @@ int mbedtls_ssl_read( mbedtls_ssl_context *ssl, unsigned char *buf, size_t len )
* or negotiated with the peer), then:
* - with TLS, less bytes than requested are written.
* - with DTLS, MBEDTLS_ERR_SSL_BAD_INPUT_DATA is returned.
* \c mbedtls_ssl_get_max_frag_len() may be used to query the
* active maximum fragment length.
* \c mbedtls_ssl_get_output_max_frag_len() may be used to
* query the active maximum fragment length.
*
* \note Attempting to write 0 bytes will result in an empty TLS
* application record being sent.