SSL_CTX_set_record_padding_callback(3) | OpenSSL | SSL_CTX_set_record_padding_callback(3) |
#include <openssl/ssl.h> void SSL_CTX_set_record_padding_callback(SSL_CTX *ctx, size_t (*cb)(SSL *s, int type, size_t len, void *arg)); int SSL_set_record_padding_callback(SSL *ssl, size_t (*cb)(SSL *s, int type, size_t len, void *arg)); void SSL_CTX_set_record_padding_callback_arg(SSL_CTX *ctx, void *arg); void *SSL_CTX_get_record_padding_callback_arg(const SSL_CTX *ctx); void SSL_set_record_padding_callback_arg(SSL *ssl, void *arg); void *SSL_get_record_padding_callback_arg(const SSL *ssl); int SSL_CTX_set_block_padding(SSL_CTX *ctx, size_t block_size); int SSL_set_block_padding(SSL *ssl, size_t block_size);
SSL_CTX_set_record_padding_callback_arg() and SSL_set_record_padding_callback_arg() assign a value arg that is passed to the callback when it is invoked. The value set in ctx is copied to a new SSL by SSL_new().
SSL_CTX_get_record_padding_callback_arg() and SSL_get_record_padding_callback_arg() retrieve the arg value that is passed to the callback.
SSL_CTX_set_block_padding() and SSL_set_block_padding() pads the record to a multiple of the block_size. A block_size of 0 or 1 disables block padding. The limit of block_size is SSL3_RT_MAX_PLAIN_LENGTH.
The callback is invoked for every record before encryption. The type parameter is the TLS record type that is being processed; may be one of SSL3_RT_APPLICATION_DATA, SSL3_RT_HANDSHAKE, or SSL3_RT_ALERT. The len parameter is the current plaintext length of the record before encryption. The arg parameter is the value set via SSL_CTX_set_record_padding_callback_arg() or SSL_set_record_padding_callback_arg().
The SSL_CTX_set_block_padding() and SSL_set_block_padding() functions return 1 on success or 0 if block_size is too large.
The cb returns the number of padding bytes to add to the record. A return of 0 indicates no padding will be added. A return value that causes the record to exceed the maximum record size (SSL3_RT_MAX_PLAIN_LENGTH) will pad out to the maximum record size.
The SSL_CTX_get_record_padding_callback_arg() function returns 1 on success or 0 if the callback function is not set because Kernel TLS is configured for the SSL object.
A user-supplied padding callback function will override the behavior set by SSL_set_block_padding() or SSL_CTX_set_block_padding(). Setting the user-supplied callback to NULL will restore the configured block padding behavior.
These functions only apply to TLS 1.3 records being written.
Padding bytes are not added in constant-time.
The return type of SSL_CTX_set_record_padding_callback() function was changed to int in OpenSSL 3.0.
Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.
2023-05-07 | 3.0.12 |