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Merge pull request #3130 from gbryant-arm/generic-psk

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Clarify and simplify PSK
This commit is contained in:
Manuel Pégourié-Gonnard 2020-04-14 10:54:01 +02:00 committed by GitHub
commit 5d318cc22b
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 86 additions and 13 deletions
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24
include/mbedtls/ssl.h
View file

@ -2682,6 +2682,9 @@ int mbedtls_ssl_conf_own_cert( mbedtls_ssl_config *conf,
* \note This is mainly useful for clients. Servers will usually
* want to use \c mbedtls_ssl_conf_psk_cb() instead.
*
* \note A PSK set by \c mbedtls_ssl_set_hs_psk() in the PSK callback
* takes precedence over a PSK configured by this function.
*
* \warning Currently, clients can only register a single pre-shared key.
* Calling this function or mbedtls_ssl_conf_psk_opaque() more
* than once will overwrite values configured in previous calls.
@ -2715,6 +2718,10 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
* \note This is mainly useful for clients. Servers will usually
* want to use \c mbedtls_ssl_conf_psk_cb() instead.
*
* \note An opaque PSK set by \c mbedtls_ssl_set_hs_psk_opaque() in
* the PSK callback takes precedence over an opaque PSK
* configured by this function.
*
* \warning Currently, clients can only register a single pre-shared key.
* Calling this function or mbedtls_ssl_conf_psk() more than
* once will overwrite values configured in previous calls.
@ -2752,6 +2759,9 @@ int mbedtls_ssl_conf_psk_opaque( mbedtls_ssl_config *conf,
* \note This should only be called inside the PSK callback,
* i.e. the function passed to \c mbedtls_ssl_conf_psk_cb().
*
* \note A PSK set by this function takes precedence over a PSK
* configured by \c mbedtls_ssl_conf_psk().
*
* \param ssl The SSL context to configure a PSK for.
* \param psk The pointer to the pre-shared key.
* \param psk_len The length of the pre-shared key in bytes.
@ -2769,6 +2779,9 @@ int mbedtls_ssl_set_hs_psk( mbedtls_ssl_context *ssl,
* \note This should only be called inside the PSK callback,
* i.e. the function passed to \c mbedtls_ssl_conf_psk_cb().
*
* \note An opaque PSK set by this function takes precedence over an
* opaque PSK configured by \c mbedtls_ssl_conf_psk_opaque().
*
* \param ssl The SSL context to configure a PSK for.
* \param psk The identifier of the key slot holding the PSK.
* For the duration of the current handshake, the key slot
@ -2807,9 +2820,14 @@ int mbedtls_ssl_set_hs_psk_opaque( mbedtls_ssl_context *ssl,
* on the SSL context to set the correct PSK and return \c 0.
* Any other return value will result in a denied PSK identity.
*
* \note If you set a PSK callback using this function, then you
* don't need to set a PSK key and identity using
* \c mbedtls_ssl_conf_psk().
* \note A dynamic PSK (i.e. set by the PSK callback) takes
* precedence over a static PSK (i.e. set by
* \c mbedtls_ssl_conf_psk() or
* \c mbedtls_ssl_conf_psk_opaque()).
* This means that if you set a PSK callback using this
* function, you don't need to set a PSK using
* \c mbedtls_ssl_conf_psk() or
* \c mbedtls_ssl_conf_psk_opaque()).
*
* \param conf The SSL configuration to register the callback with.
* \param f_psk The callback for selecting and setting the PSK based

55
include/mbedtls/ssl_internal.h
View file

@ -921,7 +921,60 @@ void mbedtls_ssl_optimize_checksum( mbedtls_ssl_context *ssl,
#if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exchange_type_t key_ex );
#endif
/**
* Get the first defined PSK by order of precedence:
* 1. handshake PSK set by \c mbedtls_ssl_set_hs_psk() in the PSK callback
* 2. static PSK configured by \c mbedtls_ssl_conf_psk()
* Return a code and update the pair (PSK, PSK length) passed to this function
*/
static inline int mbedtls_ssl_get_psk( const mbedtls_ssl_context *ssl,
const unsigned char **psk, size_t *psk_len )
{
if( ssl->handshake->psk != NULL && ssl->handshake->psk_len > 0 )
{
*psk = ssl->handshake->psk;
*psk_len = ssl->handshake->psk_len;
}
else if( ssl->conf->psk != NULL && ssl->conf->psk_len > 0 )
{
*psk = ssl->conf->psk;
*psk_len = ssl->conf->psk_len;
}
else
{
*psk = NULL;
*psk_len = 0;
return( MBEDTLS_ERR_SSL_PRIVATE_KEY_REQUIRED );
}
return( 0 );
}
#if defined(MBEDTLS_USE_PSA_CRYPTO)
/**
* Get the first defined opaque PSK by order of precedence:
* 1. handshake PSK set by \c mbedtls_ssl_set_hs_psk_opaque() in the PSK
* callback
* 2. static PSK configured by \c mbedtls_ssl_conf_psk_opaque()
* Return an opaque PSK
*/
static inline psa_key_handle_t mbedtls_ssl_get_opaque_psk(
const mbedtls_ssl_context *ssl )
{
if( ssl->handshake->psk_opaque != 0 )
return( ssl->handshake->psk_opaque );
if( ssl->conf->psk_opaque != 0 )
return( ssl->conf->psk_opaque );
return( 0 );
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */
#endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
#if defined(MBEDTLS_PK_C)
unsigned char mbedtls_ssl_sig_from_pk( mbedtls_pk_context *pk );

20
library/ssl_tls.c
View file

@ -1514,9 +1514,7 @@ static int ssl_compute_master( mbedtls_ssl_handshake_params *handshake,
MBEDTLS_SSL_DEBUG_MSG( 2, ( "perform PSA-based PSK-to-MS expansion" ) );
psk = ssl->conf->psk_opaque;
if( handshake->psk_opaque != 0 )
psk = handshake->psk_opaque;
psk = mbedtls_ssl_get_opaque_psk( ssl );
if( hash_alg == MBEDTLS_MD_SHA384 )
alg = PSA_ALG_TLS12_PSK_TO_MS(PSA_ALG_SHA_384);
@ -1850,14 +1848,18 @@ int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exch
{
unsigned char *p = ssl->handshake->premaster;
unsigned char *end = p + sizeof( ssl->handshake->premaster );
const unsigned char *psk = ssl->conf->psk;
size_t psk_len = ssl->conf->psk_len;
const unsigned char *psk = NULL;
size_t psk_len = 0;
/* If the psk callback was called, use its result */
if( ssl->handshake->psk != NULL )
if( mbedtls_ssl_get_psk( ssl, &psk, &psk_len )
== MBEDTLS_ERR_SSL_PRIVATE_KEY_REQUIRED )
{
psk = ssl->handshake->psk;
psk_len = ssl->handshake->psk_len;
/*
* This should never happen because the existence of a PSK is always
* checked before calling this function
*/
MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
/*