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Comply with the received Record Size Limit extension

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Fixes #7010

Signed-off-by: Jan Bruckner <jan@janbruckner.de>
This commit is contained in:
Jan Bruckner
2023-03-15 09:09:06 +01:00
committed by Waleed Elmelegy
parent d9c69d12ac
commit f482dcc6c7
9 changed files with 263 additions and 33 deletions
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48
library/ssl_tls13_generic.c
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@ -1714,7 +1714,7 @@ int mbedtls_ssl_tls13_parse_record_size_limit_ext(mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG(2, ("RecordSizeLimit: %u Bytes", record_size_limit));
/* RFC 8449, section 4
/* RFC 8449, section 4:
*
* Endpoints MUST NOT send a "record_size_limit" extension with a value
* smaller than 64. An endpoint MUST treat receipt of a smaller value
@ -1727,13 +1727,47 @@ int mbedtls_ssl_tls13_parse_record_size_limit_ext(mbedtls_ssl_context *ssl,
return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER;
}
MBEDTLS_SSL_DEBUG_MSG(
2, ("record_size_limit extension is still in development. Aborting handshake."));
ssl->session_negotiate->record_size_limit = record_size_limit;
MBEDTLS_SSL_PEND_FATAL_ALERT(
MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT,
MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION);
return MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION;
return 0;
}
static inline size_t ssl_compute_internal_record_size_limit(size_t record_size_limit)
{
/* 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)
*/
return ((record_size_limit / MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY) *
MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY) - 1;
}
size_t mbedtls_ssl_get_output_record_size_limit(const mbedtls_ssl_context *ssl)
{
const size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
size_t record_size_limit = max_len;
if (ssl->session != NULL &&
ssl->session->record_size_limit >= MBEDTLS_SSL_RECORD_SIZE_LIMIT_MIN &&
ssl->session->record_size_limit < max_len) {
record_size_limit = ssl_compute_internal_record_size_limit(ssl->session->record_size_limit);
}
// TODO: this is currently untested
/* During a handshake, use the value being negotiated */
if (ssl->session_negotiate != NULL &&
ssl->session_negotiate->record_size_limit >= MBEDTLS_SSL_RECORD_SIZE_LIMIT_MIN &&
ssl->session_negotiate->record_size_limit < max_len) {
record_size_limit = ssl_compute_internal_record_size_limit(
ssl->session_negotiate->record_size_limit);
}
return record_size_limit;
}
#endif /* MBEDTLS_SSL_RECORD_SIZE_LIMIT */