Use a specific function in the PSK callback
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index a72914f..e098bc9 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -672,6 +672,10 @@
#if defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C)
const mbedtls_ecp_curve_info **curves; /*!< Supported elliptic curves */
#endif
+#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+ unsigned char *psk; /*!< PSK from the callback */
+ size_t psk_len; /*!< Length of PSK from callback */
+#endif
#if defined(MBEDTLS_X509_CRT_PARSE_C)
/**
* Current key/cert or key/cert list.
@@ -1581,8 +1585,10 @@
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
/**
- * \brief Set the Pre Shared Key (PSK) and the identity name connected
- * to it.
+ * \brief Set the Pre Shared Key (PSK) and the expected identity name
+ *
+ * \note This is mainly useful for clients. Servers will usually
+ * want to use \c mbedtls_ssl_set_psk_cb() instead.
*
* \param ssl SSL context
* \param psk pointer to the pre-shared key
@@ -1592,11 +1598,28 @@
*
* \return 0 if successful or MBEDTLS_ERR_SSL_MALLOC_FAILED
*/
-int mbedtls_ssl_set_psk( mbedtls_ssl_context *ssl, const unsigned char *psk, size_t psk_len,
- const unsigned char *psk_identity, size_t psk_identity_len );
+int mbedtls_ssl_set_psk( mbedtls_ssl_context *ssl,
+ const unsigned char *psk, size_t psk_len,
+ const unsigned char *psk_identity, size_t psk_identity_len );
+
/**
- * \brief Set the PSK callback (server-side only) (Optional).
+ * \brief Set the Pre Shared Key (PSK) for the current handshake
+ *
+ * \note This should only be called inside the PSK callback,
+ * ie the function passed to \c mbedtls_ssl_set_psk_cb().
+ *
+ * \param ssl SSL context
+ * \param psk pointer to the pre-shared key
+ * \param psk_len pre-shared key length
+ *
+ * \return 0 if successful or MBEDTLS_ERR_SSL_MALLOC_FAILED
+ */
+int mbedtls_ssl_set_hs_psk( mbedtls_ssl_context *ssl,
+ const unsigned char *psk, size_t psk_len );
+
+/**
+ * \brief Set the PSK callback (server-side only).
*
* If set, the PSK callback is called for each
* handshake where a PSK ciphersuite was negotiated.
@@ -1607,10 +1630,14 @@
* mbedtls_ssl_context *ssl, const unsigned char *psk_identity,
* size_t identity_len)
* If a valid PSK identity is found, the callback should use
- * mbedtls_ssl_set_psk() on the ssl context to set the correct PSK and
- * identity and return 0.
+ * \c mbedtls_ssl_set_hs_psk() on the ssl context to set the
+ * correct PSK and return 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_set_psk().
+ *
* \param conf SSL configuration
* \param f_psk PSK identity function
* \param p_psk PSK identity parameter
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index c599761..d3ec5dc 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1066,6 +1066,15 @@
{
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;
+
+ /* If the psk callback was called, use its result */
+ if( ssl->handshake->psk != NULL )
+ {
+ psk = ssl->handshake->psk;
+ psk_len = ssl->handshake->psk_len;
+ }
/*
* PMS = struct {
@@ -1077,12 +1086,12 @@
#if defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED)
if( key_ex == MBEDTLS_KEY_EXCHANGE_PSK )
{
- if( end - p < 2 + (int) ssl->conf->psk_len )
+ if( end - p < 2 + (int) psk_len )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
- *(p++) = (unsigned char)( ssl->conf->psk_len >> 8 );
- *(p++) = (unsigned char)( ssl->conf->psk_len );
- p += ssl->conf->psk_len;
+ *(p++) = (unsigned char)( psk_len >> 8 );
+ *(p++) = (unsigned char)( psk_len );
+ p += psk_len;
}
else
#endif /* MBEDTLS_KEY_EXCHANGE_PSK_ENABLED */
@@ -1149,13 +1158,13 @@
}
/* opaque psk<0..2^16-1>; */
- if( end - p < 2 + (int) ssl->conf->psk_len )
+ if( end - p < 2 + (int) psk_len )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
- *(p++) = (unsigned char)( ssl->conf->psk_len >> 8 );
- *(p++) = (unsigned char)( ssl->conf->psk_len );
- memcpy( p, ssl->conf->psk, ssl->conf->psk_len );
- p += ssl->conf->psk_len;
+ *(p++) = (unsigned char)( psk_len >> 8 );
+ *(p++) = (unsigned char)( psk_len );
+ memcpy( p, psk, psk_len );
+ p += psk_len;
ssl->handshake->pmslen = p - ssl->handshake->premaster;
@@ -5353,8 +5362,9 @@
#endif /* MBEDTLS_X509_CRT_PARSE_C */
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
-int mbedtls_ssl_set_psk( mbedtls_ssl_context *ssl, const unsigned char *psk, size_t psk_len,
- const unsigned char *psk_identity, size_t psk_identity_len )
+int mbedtls_ssl_set_psk( mbedtls_ssl_context *ssl,
+ const unsigned char *psk, size_t psk_len,
+ const unsigned char *psk_identity, size_t psk_identity_len )
{
if( psk == NULL || psk_identity == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
@@ -5385,6 +5395,31 @@
return( 0 );
}
+int mbedtls_ssl_set_hs_psk( mbedtls_ssl_context *ssl,
+ const unsigned char *psk, size_t psk_len )
+{
+ if( psk == NULL || ssl->handshake == NULL )
+ return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+ if( psk_len > MBEDTLS_PSK_MAX_LEN )
+ return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+ if( ssl->handshake->psk != NULL )
+ mbedtls_free( ssl->conf->psk );
+
+ if( ( ssl->handshake->psk = mbedtls_malloc( psk_len ) ) == NULL )
+ {
+ mbedtls_free( ssl->handshake->psk );
+ ssl->handshake->psk = NULL;
+ return( MBEDTLS_ERR_SSL_MALLOC_FAILED );
+ }
+
+ ssl->handshake->psk_len = psk_len;
+ memcpy( ssl->handshake->psk, psk, ssl->handshake->psk_len );
+
+ return( 0 );
+}
+
void mbedtls_ssl_set_psk_cb( mbedtls_ssl_config *conf,
int (*f_psk)(void *, mbedtls_ssl_context *, const unsigned char *,
size_t),
@@ -6441,6 +6476,14 @@
mbedtls_free( (void *) handshake->curves );
#endif
+#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+ if( handshake->psk != NULL )
+ {
+ mbedtls_zeroize( handshake->psk, handshake->psk_len );
+ mbedtls_free( handshake->psk );
+ }
+#endif
+
#if defined(MBEDTLS_X509_CRT_PARSE_C) && \
defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
/*
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index e3e680c..12614c1 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -678,8 +678,7 @@
if( name_len == strlen( cur->name ) &&
memcmp( name, cur->name, name_len ) == 0 )
{
- return( mbedtls_ssl_set_psk( ssl, cur->key, cur->key_len,
- name, name_len ) );
+ return( mbedtls_ssl_set_hs_psk( ssl, cur->key, cur->key_len ) );
}
cur = cur->next;