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Merge pull request #8526 from yanrayw/issue/7011/send_record_size_limit_ext

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TLS1.3: SRV/CLI: add support for sending Record Size Limit extension
This commit is contained in:
Tom Cosgrove
2024-01-12 13:39:15 +00:00
committed by GitHub
parent 3519cfb3d8 f0ccf46713
commit f1ba1933cf
10 changed files with 294 additions and 49 deletions
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18
library/ssl_tls.c
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@ -3521,15 +3521,15 @@ int mbedtls_ssl_get_max_out_record_payload(const mbedtls_ssl_context *ssl)
if (ssl->transform_out != NULL &&
ssl->transform_out->tls_version == MBEDTLS_SSL_VERSION_TLS1_3) {
/* RFC 8449, section 4:
*
* This value [record_size_limit] is the length of the plaintext
* of a protected record.
* The value includes the content type and padding added in TLS 1.3
* (that is, the complete length of TLSInnerPlaintext).
*
* Thus, round down to a multiple of MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY
* and subtract 1 (for the content type that will be added later)
/*
* In TLS 1.3 case, when records are protected, `max_len` as computed
* above is the maximum length of the TLSInnerPlaintext structure that
* along the plaintext payload contains the inner content type (one byte)
* and some zero padding. Given the algorithm used for padding
* in mbedtls_ssl_encrypt_buf(), compute the maximum length for
* the plaintext payload. Round down to a multiple of
* MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY and
* subtract 1.
*/
max_len = ((max_len / MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY) *
MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY) - 1;