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Merge pull request #4369 from hanno-arm/relax_psk_config

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Implement relaxed semantics for static PSK configuration in Mbed TLS 3.0
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Ronald Cron 2021-05-31 10:03:56 +02:00 committed by GitHub
commit ea62d2f391
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6 changed files with 188 additions and 24 deletions
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7
ChangeLog.d/relaxed-psk-semantics.txt Normal file
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@ -0,0 +1,7 @@
API changes
* Modify semantics of `mbedtls_ssl_conf_[opaque_]psk()`:
In Mbed TLS 2.X, the API prescribes that later calls overwrite
the effect of earlier calls. In Mbed TLS 3.0, calling
`mbedtls_ssl_conf_[opaque_]psk()` more than once will fail,
leaving the PSK that was configured first intact.
Support for more than one PSK may be added in 3.X.

18
docs/3.0-migration-guide.d/relaxed-psk-semantics.md Normal file
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@ -0,0 +1,18 @@
Relaxed semantics for PSK configuration
-----------------------------------------------------------------
This affects users which call the PSK configuration APIs
`mbedtlsl_ssl_conf_psk()` and `mbedtls_ssl_conf_psk_opaque()`
multiple times on the same SSL configuration.
In Mbed TLS 2.x, users would observe later calls overwriting
the effect of earlier calls, with the prevailing PSK being
the one that has been configured last. In Mbed TLS 3.0,
calling `mbedtls_ssl_conf_[opaque_]psk()` multiple times
will return an error, leaving the first PSK intact.
To achieve equivalent functionality when migrating to Mbed TLS 3.0,
users calling `mbedtls_ssl_conf_[opaque_]psk()` multiple times should
remove all but the last call, so that only one call to _either_
`mbedtls_ssl_conf_psk()` _or_ `mbedtls_ssl_conf_psk_opaque()`
remains.

42
include/mbedtls/ssl.h
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@ -2712,8 +2712,14 @@ int mbedtls_ssl_conf_own_cert( mbedtls_ssl_config *conf,
#if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
/**
* \brief Configure a pre-shared key (PSK) and identity
* to be used in PSK-based ciphersuites.
* \brief Configure pre-shared keys (PSKs) and their
* identities to be used in PSK-based ciphersuites.
*
* Only one PSK can be registered, through either
* mbedtls_ssl_conf_psk() or mbedtls_ssl_conf_psk_opaque().
* If you attempt to register more than one PSK, this function
* fails, though this may change in future versions, which
* may add support for multiple PSKs.
*
* \note This is mainly useful for clients. Servers will usually
* want to use \c mbedtls_ssl_conf_psk_cb() instead.
@ -2721,13 +2727,6 @@ int mbedtls_ssl_conf_own_cert( mbedtls_ssl_config *conf,
* \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.
* Support for setting multiple PSKs on clients and selecting
* one based on the identity hint is not a planned feature,
* but feedback is welcomed.
*
* \param conf The SSL configuration to register the PSK with.
* \param psk The pointer to the pre-shared key to use.
* \param psk_len The length of the pre-shared key in bytes.
@ -2740,7 +2739,9 @@ int mbedtls_ssl_conf_own_cert( mbedtls_ssl_config *conf,
* of the SSL configuration.
*
* \return \c 0 if successful.
* \return An \c MBEDTLS_ERR_SSL_XXX error code on failure.
* \return #MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE if no more PSKs
* can be configured. In this case, the old PSK(s) remain intact.
* \return Another negative error code on other kinds of failure.
*/
int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
const unsigned char *psk, size_t psk_len,
@ -2748,8 +2749,14 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
#if defined(MBEDTLS_USE_PSA_CRYPTO)
/**
* \brief Configure an opaque pre-shared key (PSK) and identity
* to be used in PSK-based ciphersuites.
* \brief Configure one or more opaque pre-shared keys (PSKs) and
* their identities to be used in PSK-based ciphersuites.
*
* Only one PSK can be registered, through either
* mbedtls_ssl_conf_psk() or mbedtls_ssl_conf_psk_opaque().
* If you attempt to register more than one PSK, this function
* fails, though this may change in future versions, which
* may add support for multiple PSKs.
*
* \note This is mainly useful for clients. Servers will usually
* want to use \c mbedtls_ssl_conf_psk_cb() instead.
@ -2758,13 +2765,6 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
* 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.
* Support for setting multiple PSKs on clients and selecting
* one based on the identity hint is not a planned feature,
* but feedback is welcomed.
*
* \param conf The SSL configuration to register the PSK with.
* \param psk The identifier of the key slot holding the PSK.
* Until \p conf is destroyed or this function is successfully
@ -2781,7 +2781,9 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
* SSL configuration.
*
* \return \c 0 if successful.
* \return An \c MBEDTLS_ERR_SSL_XXX error code on failure.
* \return #MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE if no more PSKs
* can be configured. In this case, the old PSK(s) remain intact.
* \return Another negative error code on other kinds of failure.
*/
int mbedtls_ssl_conf_psk_opaque( mbedtls_ssl_config *conf,
psa_key_id_t psk,

25
library/ssl_tls.c
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@ -3721,6 +3721,19 @@ int mbedtls_ssl_set_hs_ecjpake_password( mbedtls_ssl_context *ssl,
#if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
static int ssl_conf_psk_is_configured( mbedtls_ssl_config const *conf )
{
#if defined(MBEDTLS_USE_PSA_CRYPTO)
if( !mbedtls_svc_key_id_is_null( conf->psk_opaque ) )
return( 1 );
#endif /* MBEDTLS_USE_PSA_CRYPTO */
if( conf->psk != NULL )
return( 1 );
return( 0 );
}
static void ssl_conf_remove_psk( mbedtls_ssl_config *conf )
{
/* Remove reference to existing PSK, if any. */
@ -3786,8 +3799,10 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
const unsigned char *psk_identity, size_t psk_identity_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/* Remove opaque/raw PSK + PSK Identity */
ssl_conf_remove_psk( conf );
/* We currently only support one PSK, raw or opaque. */
if( ssl_conf_psk_is_configured( conf ) )
return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
/* Check and set raw PSK */
if( psk == NULL )
@ -3855,8 +3870,10 @@ int mbedtls_ssl_conf_psk_opaque( mbedtls_ssl_config *conf,
size_t psk_identity_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/* Clear opaque/raw PSK + PSK Identity, if present. */
ssl_conf_remove_psk( conf );
/* We currently only support one PSK, raw or opaque. */
if( ssl_conf_psk_is_configured( conf ) )
return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
/* Check and set opaque PSK */
if( mbedtls_svc_key_id_is_null( psk ) )

12
tests/suites/test_suite_ssl.data
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@ -1,3 +1,15 @@
Attempt to register multiple PSKs
test_multiple_psks:
Attempt to register multiple PSKS, incl. opaque PSK, #0
test_multiple_psks_opaque:0
Attempt to register multiple PSKs, incl. opaque PSK, #1
test_multiple_psks_opaque:1
Attempt to register multiple PSKs, incl. opaque PSK, #2
test_multiple_psks_opaque:2
Test calback buffer sanity
test_callback_buffer_sanity:

108
tests/suites/test_suite_ssl.function
View File

@ -8,6 +8,8 @@
#include <ssl_tls13_keys.h>
#include "test/certs.h"
#include <psa/crypto.h>
#include <ssl_invasive.h>
#include <test/constant_flow.h>
@ -4535,3 +4537,109 @@ exit:
mbedtls_free( src );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
void test_multiple_psks()
{
unsigned char psk0[10] = { 0 };
unsigned char psk0_identity[] = { 'f', 'o', 'o' };
unsigned char psk1[10] = { 0 };
unsigned char psk1_identity[] = { 'b', 'a', 'r' };
mbedtls_ssl_config conf;
mbedtls_ssl_config_init( &conf );
TEST_ASSERT( mbedtls_ssl_conf_psk( &conf,
psk0, sizeof( psk0 ),
psk0_identity, sizeof( psk0_identity ) ) == 0 );
TEST_ASSERT( mbedtls_ssl_conf_psk( &conf,
psk1, sizeof( psk1 ),
psk1_identity, sizeof( psk1_identity ) ) ==
MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
exit:
mbedtls_ssl_config_free( &conf );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED:MBEDTLS_USE_PSA_CRYPTO */
void test_multiple_psks_opaque( int mode )
{
/*
* Mode 0: Raw PSK, then opaque PSK
* Mode 1: Opaque PSK, then raw PSK
* Mode 2: 2x opaque PSK
*/
unsigned char psk0_raw[10] = { 0 };
unsigned char psk0_raw_identity[] = { 'f', 'o', 'o' };
psa_key_id_t psk0_opaque = (psa_key_id_t) 1;
unsigned char psk0_opaque_identity[] = { 'f', 'o', 'o' };
unsigned char psk1_raw[10] = { 0 };
unsigned char psk1_raw_identity[] = { 'b', 'a', 'r' };
psa_key_id_t psk1_opaque = (psa_key_id_t) 2;
unsigned char psk1_opaque_identity[] = { 'b', 'a', 'r' };
mbedtls_ssl_config conf;
USE_PSA_INIT( );
mbedtls_ssl_config_init( &conf );
switch( mode )
{
case 0:
TEST_ASSERT( mbedtls_ssl_conf_psk( &conf,
psk0_raw, sizeof( psk0_raw ),
psk0_raw_identity, sizeof( psk0_raw_identity ) )
== 0 );
TEST_ASSERT( mbedtls_ssl_conf_psk_opaque( &conf,
psk1_opaque,
psk1_opaque_identity, sizeof( psk1_opaque_identity ) )
== MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
break;
case 1:
TEST_ASSERT( mbedtls_ssl_conf_psk_opaque( &conf,
psk0_opaque,
psk0_opaque_identity, sizeof( psk0_opaque_identity ) )
== 0 );
TEST_ASSERT( mbedtls_ssl_conf_psk( &conf,
psk1_raw, sizeof( psk1_raw ),
psk1_raw_identity, sizeof( psk1_raw_identity ) )
== MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
break;
case 2:
TEST_ASSERT( mbedtls_ssl_conf_psk_opaque( &conf,
psk0_opaque,
psk0_opaque_identity, sizeof( psk0_opaque_identity ) )
== 0 );
TEST_ASSERT( mbedtls_ssl_conf_psk_opaque( &conf,
psk1_opaque,
psk1_opaque_identity, sizeof( psk1_opaque_identity ) )
== MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
break;
default:
TEST_ASSERT( 0 );
break;
}
exit:
mbedtls_ssl_config_free( &conf );
USE_PSA_DONE( );
}
/* END_CASE */