commit 32ce596c35b2611ab949ffe95d70f7f56d0a14eb
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Tue May 21 11:01:32 2019 +0200
committer Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Mon Jun 03 09:51:08 2019 +0200
tree 0245f18bcd44abcf704b9b07243e1aff90531163
parent 57a348ba8cf08df3345d4d255bab2cfb15ce9a58

Improve save API by always updating olen

This allows callers to discover what an appropriate size is. Otherwise they'd
have to either try repeatedly, or allocate an overly large buffer (or some
combination of those).

Adapt documentation an example usage in ssl_client2.

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 459f519..2d7cd18 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -8791,7 +8791,7 @@
                               size_t *olen )
 {
     unsigned char *p = buf;
-    size_t left = buf_len;
+    size_t used = 0;
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     size_t cert_len;
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
@@ -8799,12 +8799,13 @@
     /*
      * Shallow copy of the session structure
      */
-    if( left < sizeof( mbedtls_ssl_session ) )
-        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
-    left -= sizeof( mbedtls_ssl_session );
+    used += sizeof( mbedtls_ssl_session );
 
-    memcpy( p, session, sizeof( mbedtls_ssl_session ) );
-    p += sizeof( mbedtls_ssl_session );
+    if( used <= buf_len )
+    {
+        memcpy( p, session, sizeof( mbedtls_ssl_session ) );
+        p += sizeof( mbedtls_ssl_session );
+    }
 
     /*
      * Copy of the peer's end-entity certificate
@@ -8815,18 +8816,19 @@
     else
         cert_len = session->peer_cert->raw.len;
 
-    if( left < 3 + cert_len )
-        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
-    left -= 3 + cert_len;
+    used += 3 + cert_len;
 
-    *p++ = (unsigned char)( ( cert_len >> 16 ) & 0xFF );
-    *p++ = (unsigned char)( ( cert_len >>  8 ) & 0xFF );
-    *p++ = (unsigned char)( ( cert_len       ) & 0xFF );
-
-    if( session->peer_cert != NULL )
+    if( used <= buf_len )
     {
-        memcpy( p, session->peer_cert->raw.p, cert_len );
-        p += cert_len;
+        *p++ = (unsigned char)( ( cert_len >> 16 ) & 0xFF );
+        *p++ = (unsigned char)( ( cert_len >>  8 ) & 0xFF );
+        *p++ = (unsigned char)( ( cert_len       ) & 0xFF );
+
+        if( session->peer_cert != NULL )
+        {
+            memcpy( p, session->peer_cert->raw.p, cert_len );
+            p += cert_len;
+        }
     }
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
@@ -8834,24 +8836,27 @@
      * Copy of the session ticket if any
      */
 #if defined(MBEDTLS_SSL_SESSION_TICKETS) && defined(MBEDTLS_SSL_CLI_C)
-    if( left < 3 + session->ticket_len )
-        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
-    left -= 3 + session->ticket_len;
+    used += 3 + session->ticket_len;
 
-    *p++ = (unsigned char)( ( session->ticket_len >> 16 ) & 0xFF );
-    *p++ = (unsigned char)( ( session->ticket_len >>  8 ) & 0xFF );
-    *p++ = (unsigned char)( ( session->ticket_len       ) & 0xFF );
-
-    if( session->ticket != NULL )
+    if( used <= buf_len )
     {
-        memcpy( p, session->ticket, session->ticket_len );
-        p += session->ticket_len;
+        *p++ = (unsigned char)( ( session->ticket_len >> 16 ) & 0xFF );
+        *p++ = (unsigned char)( ( session->ticket_len >>  8 ) & 0xFF );
+        *p++ = (unsigned char)( ( session->ticket_len       ) & 0xFF );
+
+        if( session->ticket != NULL )
+        {
+            memcpy( p, session->ticket, session->ticket_len );
+            p += session->ticket_len;
+        }
     }
 #endif /* MBEDTLS_SSL_SESSION_TICKETS && MBEDTLS_SSL_CLI_C */
 
     /* Done */
-    (void) left;
-    *olen = p - buf;
+    *olen = used;
+
+    if( used > buf_len )
+        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
 
     return( 0 );
 }