Merge pull request #4458 from davidhorstmann-arm/remove-max-content-len

Remove MBEDTLS_SSL_MAX_CONTENT_LEN option

ChangeLog.d/remove-max-content-len.txt

@@ -0,0 +1,4 @@
+Removals
+   * Remove MBEDTLS_SSL_MAX_CONTENT_LEN configuration option, since
+     MBEDTLS_SSL_IN_CONTENT_LEN and MBEDTLS_SSL_OUT_CONTENT_LEN replace
+     it. Fixes #4362.

configs/config-ccm-psk-tls1_2.h

@@ -79,7 +79,8 @@
  * both ends of the connection!  (See comments in "mbedtls/ssl.h".)
  * The optimal size here depends on the typical size of records.
  */
-#define MBEDTLS_SSL_MAX_CONTENT_LEN             1024
+#define MBEDTLS_SSL_IN_CONTENT_LEN             1024
+#define MBEDTLS_SSL_OUT_CONTENT_LEN             1024
 
 #include "mbedtls/check_config.h"
 

configs/config-suite-b.h

@@ -107,7 +107,8 @@
  * The minimum size here depends on the certificate chain used as well as the
  * typical size of records.
  */
-#define MBEDTLS_SSL_MAX_CONTENT_LEN             1024
+#define MBEDTLS_SSL_IN_CONTENT_LEN             1024
+#define MBEDTLS_SSL_OUT_CONTENT_LEN             1024
 
 #include "mbedtls/check_config.h"
 

docs/3.0-migration-guide.d/remove-max-content-len.md

@@ -0,0 +1,10 @@
+Remove the `MBEDTLS_SSL_MAX_CONTENT_LEN` configuration option
+-------------------------------------------------------------
+
+This affects users who use the `MBEDTLS_SSL_MAX_CONTENT_LEN` option to
+set the maximum length of incoming and outgoing plaintext fragments,
+which can save memory by reducing the size of the TLS I/O buffers.
+
+This option is replaced by the more fine-grained options
+`MBEDTLS_SSL_IN_CONTENT_LEN` and `MBEDTLS_SSL_OUT_CONTENT_LEN` that set
+the maximum incoming and outgoing plaintext fragment lengths, respectively.

include/mbedtls/config.h

@@ -3531,32 +3531,6 @@
 
 /* SSL options */
 
-/** \def MBEDTLS_SSL_MAX_CONTENT_LEN
- *
- * Maximum length (in bytes) of incoming and outgoing plaintext fragments.
- *
- * This determines the size of both the incoming and outgoing TLS I/O buffers
- * in such a way that both are capable of holding the specified amount of
- * plaintext data, regardless of the protection mechanism used.
- *
- * To configure incoming and outgoing I/O buffers separately, use
- * #MBEDTLS_SSL_IN_CONTENT_LEN and #MBEDTLS_SSL_OUT_CONTENT_LEN,
- * which overwrite the value set by this option.
- *
- * \note When using a value less than the default of 16KB on the client, it is
- *       recommended to use the Maximum Fragment Length (MFL) extension to
- *       inform the server about this limitation. On the server, there
- *       is no supported, standardized way of informing the client about
- *       restriction on the maximum size of incoming messages, and unless
- *       the limitation has been communicated by other means, it is recommended
- *       to only change the outgoing buffer size #MBEDTLS_SSL_OUT_CONTENT_LEN
- *       while keeping the default value of 16KB for the incoming buffer.
- *
- * Uncomment to set the maximum plaintext size of both
- * incoming and outgoing I/O buffers.
- */
-//#define MBEDTLS_SSL_MAX_CONTENT_LEN             16384
-
 /** \def MBEDTLS_SSL_IN_CONTENT_LEN
  *
  * Maximum length (in bytes) of incoming plaintext fragments.
@@ -3565,9 +3539,6 @@
  * that it is capable of holding the specified amount of plaintext data,
  * regardless of the protection mechanism used.
  *
- * If this option is undefined, it inherits its value from
- * #MBEDTLS_SSL_MAX_CONTENT_LEN.
- *
  * \note When using a value less than the default of 16KB on the client, it is
  *       recommended to use the Maximum Fragment Length (MFL) extension to
  *       inform the server about this limitation. On the server, there
@@ -3577,8 +3548,7 @@
  *       to only change the outgoing buffer size #MBEDTLS_SSL_OUT_CONTENT_LEN
  *       while keeping the default value of 16KB for the incoming buffer.
  *
- * Uncomment to set the maximum plaintext size of the incoming I/O buffer
+ * Uncomment to set the maximum plaintext size of the incoming I/O buffer.
- * independently of the outgoing I/O buffer.
  */
 //#define MBEDTLS_SSL_IN_CONTENT_LEN              16384
 
@@ -3637,9 +3607,6 @@
  * that it is capable of holding the specified amount of plaintext data,
  * regardless of the protection mechanism used.
  *
- * If this option undefined, it inherits its value from
- * #MBEDTLS_SSL_MAX_CONTENT_LEN.
- *
  * It is possible to save RAM by setting a smaller outward buffer, while keeping
  * the default inward 16384 byte buffer to conform to the TLS specification.
  *
@@ -3648,8 +3615,7 @@
  * The specific size requirement depends on the configured ciphers and any
  * certificate data which is sent during the handshake.
  *
- * Uncomment to set the maximum plaintext size of the outgoing I/O buffer
+ * Uncomment to set the maximum plaintext size of the outgoing I/O buffer.
- * independently of the incoming I/O buffer.
  */
 //#define MBEDTLS_SSL_OUT_CONTENT_LEN             16384
 

include/mbedtls/ssl.h

@@ -236,16 +236,12 @@
  * if you're using the Max Fragment Length extension and you know all your
  * peers are using it too!
  */
-#if !defined(MBEDTLS_SSL_MAX_CONTENT_LEN)
-#define MBEDTLS_SSL_MAX_CONTENT_LEN         16384   /**< Size of the input / output buffer */
-#endif
-
 #if !defined(MBEDTLS_SSL_IN_CONTENT_LEN)
-#define MBEDTLS_SSL_IN_CONTENT_LEN MBEDTLS_SSL_MAX_CONTENT_LEN
+#define MBEDTLS_SSL_IN_CONTENT_LEN 16384
 #endif
 
 #if !defined(MBEDTLS_SSL_OUT_CONTENT_LEN)
-#define MBEDTLS_SSL_OUT_CONTENT_LEN MBEDTLS_SSL_MAX_CONTENT_LEN
+#define MBEDTLS_SSL_OUT_CONTENT_LEN 16384
 #endif
 
 /*
@@ -3619,7 +3615,7 @@ size_t mbedtls_ssl_get_output_max_frag_len( const mbedtls_ssl_context *ssl );
 /**
  * \brief          Return the maximum fragment length (payload, in bytes) for
  *                 the input buffer. This is the negotiated maximum fragment
- *                 length, or, if there is none, MBEDTLS_SSL_MAX_CONTENT_LEN.
+ *                 length, or, if there is none, MBEDTLS_SSL_IN_CONTENT_LEN.
  *                 If it is not defined either, the value is 2^14. This function
  *                 works as its predecessor, \c mbedtls_ssl_get_max_frag_len().
  *

library/ssl_misc.h

@@ -229,23 +229,19 @@
  * Check that we obey the standard's message size bounds
  */
 
-#if MBEDTLS_SSL_MAX_CONTENT_LEN > 16384
+#if MBEDTLS_SSL_IN_CONTENT_LEN > 16384
-#error "Bad configuration - record content too large."
+#error "Bad configuration - incoming record content too large."
 #endif
 
-#if MBEDTLS_SSL_IN_CONTENT_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN
+#if MBEDTLS_SSL_OUT_CONTENT_LEN > 16384
-#error "Bad configuration - incoming record content should not be larger than MBEDTLS_SSL_MAX_CONTENT_LEN."
+#error "Bad configuration - outgoing record content too large."
 #endif
 
-#if MBEDTLS_SSL_OUT_CONTENT_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN
+#if MBEDTLS_SSL_IN_PAYLOAD_LEN > MBEDTLS_SSL_IN_CONTENT_LEN + 2048
-#error "Bad configuration - outgoing record content should not be larger than MBEDTLS_SSL_MAX_CONTENT_LEN."
-#endif
-
-#if MBEDTLS_SSL_IN_PAYLOAD_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN + 2048
 #error "Bad configuration - incoming protected record payload too large."
 #endif
 
-#if MBEDTLS_SSL_OUT_PAYLOAD_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN + 2048
+#if MBEDTLS_SSL_OUT_PAYLOAD_LEN > MBEDTLS_SSL_OUT_CONTENT_LEN + 2048
 #error "Bad configuration - outgoing protected record payload too large."
 #endif
 

library/ssl_tls.c

@@ -4647,7 +4647,7 @@ const char *mbedtls_ssl_get_version( const mbedtls_ssl_context *ssl )
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
 size_t mbedtls_ssl_get_input_max_frag_len( const mbedtls_ssl_context *ssl )
 {
-    size_t max_len = MBEDTLS_SSL_MAX_CONTENT_LEN;
+    size_t max_len = MBEDTLS_SSL_IN_CONTENT_LEN;
     size_t read_mfl;
 
     /* Use the configured MFL for the client if we're past SERVER_HELLO_DONE */

programs/ssl/ssl_server2.c

@@ -451,7 +451,7 @@ int main( void )
     "    server_port=%%d      default: 4433\n"              \
     "    debug_level=%%d      default: 0 (disabled)\n"      \
     "    buffer_size=%%d      default: 200 \n" \
-    "                         (minimum: 1, max: 16385)\n" \
+    "                         (minimum: 1)\n" \
     "    response_size=%%d    default: about 152 (basic response)\n" \
     "                          (minimum: 0, max: 16384)\n" \
     "                          increases buffer_size if bigger\n"\
@@ -1572,13 +1572,13 @@ int main( int argc, char *argv[] )
         else if( strcmp( p, "buffer_size" ) == 0 )
         {
             opt.buffer_size = atoi( q );
-            if( opt.buffer_size < 1 || opt.buffer_size > MBEDTLS_SSL_MAX_CONTENT_LEN + 1 )
+            if( opt.buffer_size < 1 )
                 goto usage;
         }
         else if( strcmp( p, "response_size" ) == 0 )
         {
             opt.response_size = atoi( q );
-            if( opt.response_size < 0 || opt.response_size > MBEDTLS_SSL_MAX_CONTENT_LEN )
+            if( opt.response_size < 0 || opt.response_size > MBEDTLS_SSL_OUT_CONTENT_LEN )
                 goto usage;
             if( opt.buffer_size < opt.response_size )
                 opt.buffer_size = opt.response_size;

programs/test/query_config.c

@@ -2595,14 +2595,6 @@ int query_config( const char *config )
     }
 #endif /* MBEDTLS_SSL_CACHE_DEFAULT_MAX_ENTRIES */
 
-#if defined(MBEDTLS_SSL_MAX_CONTENT_LEN)
-    if( strcmp( "MBEDTLS_SSL_MAX_CONTENT_LEN", config ) == 0 )
-    {
-        MACRO_EXPANSION_TO_STR( MBEDTLS_SSL_MAX_CONTENT_LEN );
-        return( 0 );
-    }
-#endif /* MBEDTLS_SSL_MAX_CONTENT_LEN */
-
 #if defined(MBEDTLS_SSL_IN_CONTENT_LEN)
     if( strcmp( "MBEDTLS_SSL_IN_CONTENT_LEN", config ) == 0 )
     {

tests/ssl-opt.sh

@@ -374,7 +374,7 @@ requires_not_i686() {
 }
 
 # Calculate the input & output maximum content lengths set in the config
-MAX_CONTENT_LEN=$( ../scripts/config.py get MBEDTLS_SSL_MAX_CONTENT_LEN || echo "16384")
+MAX_CONTENT_LEN=16384
 MAX_IN_LEN=$( ../scripts/config.py get MBEDTLS_SSL_IN_CONTENT_LEN || echo "$MAX_CONTENT_LEN")
 MAX_OUT_LEN=$( ../scripts/config.py get MBEDTLS_SSL_OUT_CONTENT_LEN || echo "$MAX_CONTENT_LEN")
 
@@ -3014,8 +3014,13 @@ run_test    "Session resume using cache, DTLS: openssl server" \
 
 # Tests for Max Fragment Length extension
 
-if [ "$MAX_CONTENT_LEN" -lt "4096" ]; then
+if [ "$MAX_IN_LEN" -lt "4096" ]; then
-    printf '%s defines MBEDTLS_SSL_MAX_CONTENT_LEN to be less than 4096. Fragment length tests will fail.\n' "${CONFIG_H}"
+    printf '%s defines MBEDTLS_SSL_IN_CONTENT_LEN to be less than 4096. Fragment length tests will fail.\n' "${CONFIG_H}"
+    exit 1
+fi
+
+if [ "$MAX_OUT_LEN" -lt "4096" ]; then
+    printf '%s defines MBEDTLS_SSL_OUT_CONTENT_LEN to be less than 4096. Fragment length tests will fail.\n' "${CONFIG_H}"
     exit 1
 fi