Let MBEDTLS_SSL_MAX_CONTENT_LEN to be split into outward & inward sizes
For the situation where the mbedTLS device has limited RAM, but the
other end of the connection doesn't support the max_fragment_length
extension. To be spec-compliant, mbedTLS has to keep a 16384 byte
incoming buffer. However the outgoing buffer can be made smaller without
breaking spec compliance, and we save some RAM.
See comments in include/mbedtls/config.h for some more details.
(The lower limit of outgoing buffer size is the buffer size used during
handshake/cert negotiation. As the handshake is half-duplex it might
even be possible to store this data in the "incoming" buffer during the
handshake, which would save even more RAM - but it would also be a lot
hackier and error-prone. I didn't really explore this possibility, but
thought I'd mention it here in case someone sees this later on a mission
to jam mbedTLS into an even tinier RAM footprint.)
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index eb19f58..29678e3 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -1303,7 +1303,7 @@
else
#endif
{
- if( msg_len > MBEDTLS_SSL_MAX_CONTENT_LEN )
+ if( msg_len > MBEDTLS_SSL_IN_CONTENT_LEN )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
@@ -2235,7 +2235,7 @@
{
int ret;
unsigned char *p = buf;
- const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
+ const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_OUT_CONTENT_LEN;
size_t kkpp_len;
*olen = 0;
@@ -2342,7 +2342,7 @@
cookie_len_byte = p++;
if( ( ret = ssl->conf->f_cookie_write( ssl->conf->p_cookie,
- &p, ssl->out_buf + MBEDTLS_SSL_BUFFER_LEN,
+ &p, ssl->out_buf + MBEDTLS_SSL_OUT_BUFFER_LEN,
ssl->cli_id, ssl->cli_id_len ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "f_cookie_write", ret );
@@ -2638,7 +2638,7 @@
size_t dn_size, total_dn_size; /* excluding length bytes */
size_t ct_len, sa_len; /* including length bytes */
unsigned char *buf, *p;
- const unsigned char * const end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
+ const unsigned char * const end = ssl->out_msg + MBEDTLS_SSL_OUT_CONTENT_LEN;
const mbedtls_x509_crt *crt;
int authmode;
@@ -2839,7 +2839,7 @@
* ssl_write_server_key_exchange also takes care of incrementing
* ssl->out_msglen. */
unsigned char *sig_start = ssl->out_msg + ssl->out_msglen + 2;
- size_t sig_max_len = ( ssl->out_buf + MBEDTLS_SSL_MAX_CONTENT_LEN
+ size_t sig_max_len = ( ssl->out_buf + MBEDTLS_SSL_OUT_CONTENT_LEN
- sig_start );
int ret = ssl->conf->f_async_resume( ssl,
sig_start, signature_len, sig_max_len );
@@ -2893,7 +2893,7 @@
ret = mbedtls_ecjpake_write_round_two(
&ssl->handshake->ecjpake_ctx,
ssl->out_msg + ssl->out_msglen,
- MBEDTLS_SSL_MAX_CONTENT_LEN - ssl->out_msglen, &len,
+ MBEDTLS_SSL_OUT_CONTENT_LEN - ssl->out_msglen, &len,
ssl->conf->f_rng, ssl->conf->p_rng );
if( ret != 0 )
{
@@ -3020,7 +3020,7 @@
if( ( ret = mbedtls_ecdh_make_params(
&ssl->handshake->ecdh_ctx, &len,
ssl->out_msg + ssl->out_msglen,
- MBEDTLS_SSL_MAX_CONTENT_LEN - ssl->out_msglen,
+ MBEDTLS_SSL_OUT_CONTENT_LEN - ssl->out_msglen,
ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_make_params", ret );
@@ -4171,7 +4171,7 @@
if( ( ret = ssl->conf->f_ticket_write( ssl->conf->p_ticket,
ssl->session_negotiate,
ssl->out_msg + 10,
- ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN,
+ ssl->out_msg + MBEDTLS_SSL_OUT_CONTENT_LEN,
&tlen, &lifetime ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_ticket_write", ret );
