Implement key rotation

parent 887674a3
......@@ -52,6 +52,7 @@ mbedtls_ssl_ticket_key;
typedef struct
{
mbedtls_ssl_ticket_key keys[2]; /*!< ticket protection keys */
unsigned char active; /*!< index of the currently active key */
uint32_t ticket_lifetime; /*!< lifetime of tickets in seconds */
......
......@@ -88,6 +88,34 @@ static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
return( ret );
}
/*
* Rotate/generate keys if necessary
*/
static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
{
#if !defined(MBEDTLS_HAVE_TIME)
((void) ctx);
#else
if( ctx->ticket_lifetime != 0 )
{
uint32_t current_time = (uint32_t) time( NULL );
uint32_t key_time = ctx->keys[ctx->active].generation_time;
if( current_time > key_time &&
current_time - key_time < ctx->ticket_lifetime )
{
return( 0 );
}
ctx->active = 1 - ctx->active;
return( ssl_ticket_gen_key( ctx, ctx->active ) );
}
else
#endif /* MBEDTLS_HAVE_TIME */
return( 0 );
}
/*
* Setup context for actual use
*/
......@@ -263,7 +291,7 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
{
int ret;
mbedtls_ssl_ticket_context *ctx = p_ticket;
mbedtls_ssl_ticket_key *key = ctx->keys;
mbedtls_ssl_ticket_key *key;
unsigned char *key_name = start;
unsigned char *iv = start + 4;
unsigned char *state_len_bytes = iv + 12;
......@@ -286,6 +314,11 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
return( ret );
#endif
if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
goto cleanup;
key = &ctx->keys[ctx->active];
*ticket_lifetime = ctx->ticket_lifetime;
memcpy( key_name, key->name, 4 );
......@@ -328,6 +361,22 @@ cleanup:
return( ret );
}
/*
* Select key based on name
*/
static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
mbedtls_ssl_ticket_context *ctx,
const unsigned char name[4] )
{
unsigned char i;
for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
return( &ctx->keys[i] );
return( NULL );
}
/*
* Load session ticket (see mbedtls_ssl_ticket_write for structure)
*/
......@@ -338,7 +387,7 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
{
int ret;
mbedtls_ssl_ticket_context *ctx = p_ticket;
mbedtls_ssl_ticket_key *key = ctx->keys;
mbedtls_ssl_ticket_key *key;
unsigned char *key_name = buf;
unsigned char *iv = buf + 4;
unsigned char *enc_len_p = iv + 12;
......@@ -346,17 +395,21 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
unsigned char *tag;
size_t enc_len, clear_len;
if( ctx == NULL || ctx->f_rng == NULL ||
len < 4 + 12 + 2 + 16 )
{
if( ctx == NULL || ctx->f_rng == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
/* See mbedtls_ssl_ticket_write() */
if( len < 4 + 12 + 2 + 16 )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
goto cleanup;
enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
tag = ticket + enc_len;
......@@ -366,10 +419,12 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
goto cleanup;
}
/* Check name (public data) */
if( memcmp( key_name, key->name, 4 ) != 0 )
/* Select key */
if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
{
ret = MBEDTLS_ERR_SSL_INVALID_MAC;
/* We can't know for sure but this is a likely option unless we're
* under attack - this is only informative anyway */
ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
goto cleanup;
}
......@@ -378,7 +433,9 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
key_name, 4 + 12 + 2, ticket, enc_len,
ticket, &clear_len, tag, 16 ) ) != 0 )
{
/* TODO: convert AUTH_FAILED to INVALID_MAC */
if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
ret = MBEDTLS_ERR_SSL_INVALID_MAC;
goto cleanup;
}
if( clear_len != enc_len )
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment