Document more precisely what goes into the default profile

Signed-off-by: Gilles Peskine <[email protected]>

include/mbedtls/x509_crt.h

@@ -229,12 +229,21 @@ typedef void mbedtls_x509_crt_restart_ctx;
 /**
  * Default security profile. Should provide a good balance between security
  * and compatibility with current deployments.
+ *
+ * This profile permits:
+ * - SHA2 hashes.
+ * - All supported elliptic curves.
+ * - RSA with 2048 bits and above.
+ *
+ * New minor versions of Mbed TLS may extend this profile, for example if
+ * new curves are added to the library. New minor versions of Mbed TLS will
+ * not reduce this profile unless serious security concerns require it.
  */
 extern const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_default;
 
 /**
  * Expected next default profile. Recommended for new deployments.
- * Currently targets a 128-bit security level, except for RSA-2048.
+ * Currently targets a 128-bit security level, except for allowing RSA-2048.
  */
 extern const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_next;
 

library/x509_crt.c

@@ -116,9 +116,8 @@ typedef struct {
  */
 #define X509_MAX_VERIFY_CHAIN_SIZE    ( MBEDTLS_X509_MAX_INTERMEDIATE_CA + 2 )
 
-/*
- * Default profile
- */
+/* Default profile. Do not remove items unless there are serious security
+ * concerns. */
 const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_default =
 {
 #if defined(MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_CERTIFICATES)