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Add an extra key export function

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Add an additional function `mbedtls_ssl_export_keys_ext_t()`
for exporting key, that adds additional information such as
the used `tls_prf` and the random bytes.
This commit is contained in:
Ron Eldor 2019-05-07 18:33:40 +03:00
parent 3b350856ff
commit f5cc10d93b
2 changed files with 91 additions and 0 deletions
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73
include/mbedtls/ssl.h
View file

@ -559,6 +559,25 @@ typedef void mbedtls_ssl_set_timer_t( void * ctx,
*/
typedef int mbedtls_ssl_get_timer_t( void * ctx );
/**
* \brief Function type: TLS-PRF function.
*
* \param secret Secret for the key derivation function.
* \param slen Length of the secret.
* \param label String label for the key derivation function,
* terminated with null character.
* \param random Random bytes.
* \param rlen Length of the random bytes buffer.
* \param dstbuf The buffer holding the derived key.
* \param dlen Length of the output buffer.
*
* \return 0 on sucess. An SSL specific error on failure.
*/
typedef int mbedtls_ssl_tls_prf( const unsigned char *secret, size_t slen,
const char *label,
const unsigned char *random, size_t rlen,
unsigned char *dstbuf, size_t dlen );
/* Defined below */
typedef struct mbedtls_ssl_session mbedtls_ssl_session;
typedef struct mbedtls_ssl_context mbedtls_ssl_context;
@ -920,6 +939,11 @@ struct mbedtls_ssl_config
/** Callback to export key block and master secret */
int (*f_export_keys)( void *, const unsigned char *,
const unsigned char *, size_t, size_t, size_t );
/** Callback to export key block, master secret,
* tls_prf and random bytes. Should replace f_export_keys */
int (*f_export_keys_ext)( void *, const unsigned char *,
const unsigned char *, size_t, size_t, size_t,
mbedtls_ssl_tls_prf *, unsigned char[32], unsigned char[32]);
void *p_export_keys; /*!< context for key export callback */
#endif
@ -1624,6 +1648,41 @@ typedef int mbedtls_ssl_export_keys_t( void *p_expkey,
size_t maclen,
size_t keylen,
size_t ivlen );
/**
* \brief Callback type: Export key block, master secret,
* handshake randbytes and the tls_prf function
* used to derive keys.
*
* \note This is required for certain uses of TLS, e.g. EAP-TLS
* (RFC 5216) and Thread. The key pointers are ephemeral and
* therefore must not be stored. The master secret and keys
* should not be used directly except as an input to a key
* derivation function.
*
* \param p_expkey Context for the callback.
* \param ms Pointer to master secret (fixed length: 48 bytes).
* \param kb Pointer to key block, see RFC 5246 section 6.3.
* (variable length: 2 * maclen + 2 * keylen + 2 * ivlen).
* \param maclen MAC length.
* \param keylen Key length.
* \param ivlen IV length.
* \param tls_prf The TLS PRF function used in the handshake.
* \param client_random The client random bytes.
* \param server_random The server random bytes.
*
* \return 0 if successful, or
* a specific MBEDTLS_ERR_XXX code.
*/
typedef int mbedtls_ssl_export_keys_ext_t( void *p_expkey,
const unsigned char *ms,
const unsigned char *kb,
size_t maclen,
size_t keylen,
size_t ivlen,
mbedtls_ssl_tls_prf *tls_prf,
unsigned char client_random[32],
unsigned char server_random[32] );
#endif /* MBEDTLS_SSL_EXPORT_KEYS */
/**
@ -1689,6 +1748,20 @@ void mbedtls_ssl_conf_session_tickets_cb( mbedtls_ssl_config *conf,
void mbedtls_ssl_conf_export_keys_cb( mbedtls_ssl_config *conf,
mbedtls_ssl_export_keys_t *f_export_keys,
void *p_export_keys );
/**
* \brief Configure extended key export callback.
* (Default: none.)
*
* \note See \c mbedtls_ssl_export_keys_ext_t.
*
* \param conf SSL configuration context
* \param f_export_keys_ext Callback for exporting keys
* \param p_export_keys Context for the callback
*/
void mbedtls_ssl_conf_export_keys_ext_cb( mbedtls_ssl_config *conf,
mbedtls_ssl_export_keys_ext_t *f_export_keys_ext,
void *p_export_keys );
#endif /* MBEDTLS_SSL_EXPORT_KEYS */
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE)

18
library/ssl_tls.c
View file

@ -1265,6 +1265,16 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
mac_key_len, keylen,
iv_copy_len );
}
if( ssl->conf->f_export_keys_ext != NULL )
{
ssl->conf->f_export_keys_ext( ssl->conf->p_export_keys,
session->master, keyblk,
mac_key_len, transform->keylen,
iv_copy_len, handshake->tls_prf,
handshake->randbytes + 32,
handshake->randbytes );
}
#endif
#if defined(MBEDTLS_USE_PSA_CRYPTO)
@ -8653,6 +8663,14 @@ void mbedtls_ssl_conf_export_keys_cb( mbedtls_ssl_config *conf,
conf->f_export_keys = f_export_keys;
conf->p_export_keys = p_export_keys;
}
void mbedtls_ssl_conf_export_keys_ext_cb( mbedtls_ssl_config *conf,
mbedtls_ssl_export_keys_ext_t *f_export_keys_ext,
void *p_export_keys )
{
conf->f_export_keys_ext = f_export_keys_ext;
conf->p_export_keys = p_export_keys;
}
#endif
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE)