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tls13: keys: Do not use handshake->premaster

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`handshake->premaster` was used to store the
(EC)DHE shared secret but in TLS 1.3 there is
no need to store it in a context.

Futhermore, `handshake->premaster` and more
specifically its sizing is TLS 1.2 specific
thus better to not use it in TLS 1.3.

Allocate a buffer to store the shared secret
instead. Allocation instead of a stack buffer
as the maintenance of the size of such buffer
is harder (new elliptic curve for ECDHE,
support for FFDHE ... ).

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron 2022-10-05 17:20:21 +02:00
parent 4c7edb2b9b
commit 3b056202d3
2 changed files with 30 additions and 12 deletions
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5
library/ssl_misc.h
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@ -600,8 +600,6 @@ struct mbedtls_ssl_handshake_params
size_t ecrs_n; /*!< place for saving a length */
#endif
size_t pmslen; /*!< premaster length */
mbedtls_ssl_ciphersuite_t const *ciphersuite_info;
void (*update_checksum)(mbedtls_ssl_context *, const unsigned char *, size_t);
@ -853,8 +851,11 @@ struct mbedtls_ssl_handshake_params
unsigned char randbytes[MBEDTLS_CLIENT_HELLO_RANDOM_LEN +
MBEDTLS_SERVER_HELLO_RANDOM_LEN];
/*!< random bytes */
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
unsigned char premaster[MBEDTLS_PREMASTER_SIZE];
/*!< premaster secret */
size_t pmslen; /*!< premaster length */
#endif
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
int extensions_present; /*!< extension presence; Each bitfield