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mbedtls_ssl_read() function
Read at most 'len' application data bytes \warning If this function returns something other than a positive value, #MBEDTLS_ERR_SSL_WANT_READ, #MBEDTLS_ERR_SSL_WANT_WRITE, #MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS, #MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS or #MBEDTLS_ERR_SSL_CLIENT_RECONNECT, you must stop using the SSL context for reading or writing, and either free it or call \c mbedtls_ssl_session_reset() on it before re-using it for a new connection; the current connection must be closed.
Syntax
Implemented in ![]()
ssl_tls.c:8263
Return value
The (positive) number of bytes read if successful. \c 0 if the read end of the underlying transport was closed - in this case you must stop using the context (see below). #MBEDTLS_ERR_SSL_WANT_READ or #MBEDTLS_ERR_SSL_WANT_WRITE if the handshake is incomplete and waiting for data to be available for reading from or writing to the underlying transport - in this case you must call this function again when the underlying transport is ready for the operation. #MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS if an asynchronous operation is in progress (see mbedtls_ssl_conf_async_private_cb()) - in this case you must call this function again when the operation is ready. #MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS if a cryptographic operation is in progress (see mbedtls_ecp_set_max_ops()) - in this case you must call this function again to complete the handshake when you're done attending other tasks. #MBEDTLS_ERR_SSL_CLIENT_RECONNECT if we're at the server side of a DTLS connection and the client is initiating a new connection using the same source port. See below. Another SSL error code - in this case you must stop using the context (see below).
Notes
When this function returns #MBEDTLS_ERR_SSL_CLIENT_RECONNECT (which can only happen server-side), it means that a client is initiating a new connection using the same source port. You can either treat that as a connection close and wait for the client to resend a ClientHello, or directly continue with \c mbedtls_ssl_handshake() with the same context (as it has been reset internally). Either way, you must make sure this is seen by the application as a new connection: application state, if any, should be reset, and most importantly the identity of the client must be checked again. WARNING: not validating the identity of the client again, or not transmitting the new identity to the application layer, would allow authentication bypass! Remarks regarding event-driven DTLS: - If the function returns #MBEDTLS_ERR_SSL_WANT_READ, no datagram from the underlying transport layer is currently being processed, and it is safe to idle until the timer or the underlying transport signal a new event. - This function may return MBEDTLS_ERR_SSL_WANT_READ even if data was initially available on the underlying transport, as this data may have been only e.g. duplicated messages or a renegotiation request. Therefore, you must be prepared to receive MBEDTLS_ERR_SSL_WANT_READ even when reacting to an incoming-data event from the underlying transport. - On success, the datagram of the underlying transport that is currently being processed may contain further DTLS records. You should call \c mbedtls_ssl_check_pending to check for remaining records.
Related Functions
Found 118 other functions taking a ![]()
mbedtls_ssl_context
argument:
Function
Description
Send an alert message
Update record layer This function roughly separates the implementation of the logic of (D)TLS from the implementation of the secure transport. The record layer takes as input an untrusted underlying transport (stream or datagram) and transforms it into a serially multiplexed, secure transport, which conceptually provides the following: (1) Three datagram based, content-agnostic transports for handshake, alert and CCS messages. (2) One stream- or datagram-based transport for application data. (3) Functionality for changing the underlying transform securing the contents. The interface to this functionality is given as follows: a Updating [Currently implemented by mbedtls_ssl_read_record] Check if and on which of the four 'ports' data is pending: Nothing, a controlling datagram of type (1), or application data (2). In any case data is present, internal buffers provide access to the data for the user to process it. Consumption of type (1) datagrams is done automatically on the next update, invalidating that the internal buffers for previous datagrams, while consumption of application data (2) is user-controlled. b Reading of application data [Currently manual adaption of ssl->in_offt pointer] As mentioned in the last paragraph, consumption of data is different from the automatic consumption of control datagrams (1) because application data is treated as a stream. c Tracking availability of application data [Currently manually through decreasing ssl->in_msglen] For efficiency and to retain datagram semantics for application data in case of DTLS, the record layer provides functionality for checking how much application data is still available in the internal buffer. d Changing the transformation securing the communication. Given an opaque implementation of the record layer in the above sense, it should be possible to implement the logic of (D)TLS on top of it without the need to know anything about the record layer's internals. This is done e.g. in all the handshake handling functions, and in the application data reading function mbedtls_ssl_read.
Perform the SSL handshake \warning If this function returns something other than \c 0, #MBEDTLS_ERR_SSL_WANT_READ, #MBEDTLS_ERR_SSL_WANT_WRITE, #MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS or #MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS, you must stop using the SSL context for reading or writing, and either free it or call \c mbedtls_ssl_session_reset() on it before re-using it for a new connection; the current connection must be closed.
Try to write exactly 'len' application data bytes \warning This function will do partial writes in some cases. If the return value is non-negative but less than length, the function must be called again with updated arguments: buf + ret, len - ret (if ret is the return value) until it returns a value equal to the last 'len' argument. \warning If this function returns something other than a non-negative value, #MBEDTLS_ERR_SSL_WANT_READ, #MBEDTLS_ERR_SSL_WANT_WRITE, #MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS or #MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS, you must stop using the SSL context for reading or writing, and either free it or call \c mbedtls_ssl_session_reset() on it before re-using it for a new connection; the current connection must be closed.
Notify the peer that the connection is being closed
Free referenced items in an SSL context and clear memory
Initialize an SSL context Just makes the context ready for mbedtls_ssl_setup() or mbedtls_ssl_free()
Set up an SSL context for use \warning The conf structure will be accessed during the session. It must not be modified or freed as long as the session is active. \warning This function must be called exactly once per context. Calling mbedtls_ssl_setup again is not supported, even if no session is active.
Set the underlying BIO callbacks for write, read and read-with-timeout.
Return the result of the certificate verification
Return the name of the current ciphersuite
Set or reset the hostname to check against the received server certificate. It sets the ServerName TLS extension, too, if that extension is enabled. (client-side only) Hostname set to the one provided on success (cleared when NULL). On allocation failure hostname is cleared. On too long input failure, old hostname is unchanged.
Reset an already initialized SSL context for re-use while retaining application-set variables, function pointers and data.
Free referenced items in an SSL handshake context and clear memory
Return the current maximum outgoing record payload in bytes. This takes into account the config.h setting \c MBEDTLS_SSL_OUT_CONTENT_LEN, the configured and negotiated max fragment length extension if used, and for DTLS the path MTU as configured and current record expansion. \sa mbedtls_ssl_set_mtu() \sa mbedtls_ssl_get_max_frag_len() \sa mbedtls_ssl_get_record_expansion()
Perform a single step of the SSL handshake \warning If this function returns something other than \c 0, #MBEDTLS_ERR_SSL_WANT_READ, #MBEDTLS_ERR_SSL_WANT_WRITE, #MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS or #MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS, you must stop using the SSL context for reading or writing, and either free it or call \c mbedtls_ssl_session_reset() on it before re-using it for a new connection; the current connection must be closed.
Validate cipher suite against config in SSL context.
Check if there is data already read from the underlying transport but not yet processed.
Return the number of application data bytes remaining to be read from the current record.
Return the current SSL version (SSLv3/TLSv1/etc)
Return the (maximum) number of bytes added by the record layer: header + encryption/MAC overhead (inc. padding)
Return the peer certificate from the current connection Note: Can be NULL in case no certificate was sent during the handshake. Different calls for the same connection can return the same or different pointers for the same certificate and even a different certificate altogether. The peer cert CAN change in a single connection if renegotiation is performed.
Save session in order to resume it later (client-side only) Session data is copied to presented session structure. \sa mbedtls_ssl_set_session()
Set the timer callbacks (Mandatory for DTLS.)
Request resumption of session (client-side only) Session data is copied from presented session structure. \sa mbedtls_ssl_get_session()
Print a message to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_MSG() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.
Print the return value of a function to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_RET() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.
Output a buffer of size len bytes to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_BUF() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.
Print a MPI variable to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_MPI() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.
Print an ECP point to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_ECP() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.
Print a X.509 certificate structure to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_CRT() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.
Print a field of the ECDH structure in the SSL context to the debug output. This function is always used through the MBEDTLS_SSL_DEBUG_ECDH() macro, which supplies the ssl context, file and line number parameters. \attention This function is intended for INTERNAL usage within the library only.