Disable ECC key sizes < 224 bits by default. Added --enable-eccweakcurves or ECC_WEAK_CURVES to enable smaller key sizes. Currently this option is automatically enabled if WOLFSSL_MIN_ECC_BITS is less than 224-bits.

configure.ac

@@ -1880,6 +1880,19 @@ then
 fi
 
 
+# ECC Weak Key Sizes (224-bit equiv to RSA 2048 - by default disable < 224 bit ECC)
+AC_ARG_ENABLE([eccweakcurves],
+    [AS_HELP_STRING([--enable-eccweakcurves],[Enable ECC curves less than 224 bit (default: disabled)])],
+    [ ENABLED_ECCWEAKCURVES=$enableval ],
+    [ ENABLED_ECCWEAKCURVES=no ]
+    )
+
+if test "$ENABLED_ECCWEAKCURVES" = "yes"
+then
+    AM_CFLAGS="$AM_CFLAGS -DECC_WEAK_CURVES"
+fi
+
+
 # Compressed Key
 AC_ARG_ENABLE([compkey],
     [AS_HELP_STRING([--enable-compkey],[Enable compressed keys support (default: disabled)])],
@@ -6042,6 +6055,7 @@ echo "   * DH:                         $ENABLED_DH"
 echo "   * DH Default Parameters:      $ENABLED_DHDEFAULTPARAMS"
 echo "   * ECC:                        $ENABLED_ECC"
 echo "   * ECC Custom Curves           $ENABLED_ECCCUSTCURVES"
+echo "   * ECC Weak Curves             $ENABLED_ECCWEAKCURVES"
 echo "   * CURVE25519:                 $ENABLED_CURVE25519"
 echo "   * ED25519:                    $ENABLED_ED25519"
 echo "   * CURVE448:                   $ENABLED_CURVE448"

src/internal.c

@@ -21114,7 +21114,7 @@ exit_dpk:
         int ret = ECC_CURVE_ERROR;
 
         switch (tlsCurveId) {
-    #if defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)
+    #if (defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
         #ifndef NO_ECC_SECP
             case WOLFSSL_ECC_SECP160R1: return ECC_SECP160R1_OID;
         #endif /* !NO_ECC_SECP */
@@ -21125,7 +21125,7 @@ exit_dpk:
             case WOLFSSL_ECC_SECP160K1: return ECC_SECP160K1_OID;
         #endif /* HAVE_ECC_KOBLITZ */
     #endif
-    #if defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)
+    #if (defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
         #ifndef NO_ECC_SECP
             case WOLFSSL_ECC_SECP192R1: return ECC_SECP192R1_OID;
         #endif /* !NO_ECC_SECP */
@@ -24763,7 +24763,7 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
     /* returns the WOLFSSL_* version of the curve from the OID sum */
     word16 GetCurveByOID(int oidSum) {
         switch(oidSum) {
-    #if defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)
+    #if (defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
         #ifndef NO_ECC_SECP
             case ECC_SECP160R1_OID:
                 return WOLFSSL_ECC_SECP160R1;
@@ -24777,7 +24777,7 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
                 return WOLFSSL_ECC_SECP160K1;
         #endif /* HAVE_ECC_KOBLITZ */
     #endif
-    #if defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)
+    #if (defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
         #ifndef NO_ECC_SECP
             case ECC_SECP192R1_OID:
                 return WOLFSSL_ECC_SECP192R1;

src/tls.c

@@ -4340,7 +4340,7 @@ int TLSX_ValidateSupportedCurves(WOLFSSL* ssl, byte first, byte second) {
         /* find supported curve */
         switch (curve->name) {
 #ifdef HAVE_ECC
-    #if defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)
+    #if (defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
         #ifndef NO_ECC_SECP
             case WOLFSSL_ECC_SECP160R1:
                 pkOid = oid = ECC_SECP160R1_OID;
@@ -4360,7 +4360,7 @@ int TLSX_ValidateSupportedCurves(WOLFSSL* ssl, byte first, byte second) {
                 break;
         #endif /* HAVE_ECC_KOBLITZ */
         #endif
-    #if defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)
+    #if (defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
         #ifndef NO_ECC_SECP
             case WOLFSSL_ECC_SECP192R1:
                 pkOid = oid = ECC_SECP192R1_OID;
@@ -9926,7 +9926,7 @@ static int TLSX_PopulateSupportedGroups(WOLFSSL* ssl, TLSX** extensions)
         #endif
 
     #ifndef HAVE_FIPS
-        #if defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)
+        #if (defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
             #ifndef NO_ECC_SECP
                 ret = TLSX_UseSupportedCurve(extensions,
                                               WOLFSSL_ECC_SECP192R1, ssl->heap);
@@ -9938,7 +9938,7 @@ static int TLSX_PopulateSupportedGroups(WOLFSSL* ssl, TLSX** extensions)
                 if (ret != WOLFSSL_SUCCESS) return ret;
             #endif
         #endif
-        #if defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)
+        #if (defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
             #ifndef NO_ECC_SECP
                 ret = TLSX_UseSupportedCurve(extensions,
                                               WOLFSSL_ECC_SECP160R1, ssl->heap);

wolfcrypt/src/ecc.c

@@ -75,6 +75,7 @@ ECC Curve Types:
 ECC Curve Sizes:
  * ECC_USER_CURVES: Allows custom combination of key sizes below
  * HAVE_ALL_CURVES: Enable all key sizes (on unless ECC_USER_CURVES is defined)
+ * ECC_WEAK_CURVES: Enable support for weak keys < 224 bits
  * HAVE_ECC112: 112 bit key
  * HAVE_ECC128: 128 bit key
  * HAVE_ECC160: 160 bit key
@@ -179,16 +180,16 @@ enum {
 */
 
 /* 256-bit curve on by default whether user curves or not */
-#if defined(HAVE_ECC112) || defined(HAVE_ALL_CURVES)
+#if (defined(HAVE_ECC112) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
     #define ECC112
 #endif
-#if defined(HAVE_ECC128) || defined(HAVE_ALL_CURVES)
+#if (defined(HAVE_ECC128) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
     #define ECC128
 #endif
-#if defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)
+#if (defined(HAVE_ECC160) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
     #define ECC160
 #endif
-#if defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)
+#if (defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)) && defined(ECC_WEAK_CURVES)
     #define ECC192
 #endif
 #if defined(HAVE_ECC224) || defined(HAVE_ALL_CURVES)

wolfssl/wolfcrypt/ecc.h

@@ -93,7 +93,7 @@
     #define MAX_ECC_BITS    256
 #elif defined(HAVE_ECC239)
     #define MAX_ECC_BITS    239
-#elif defined(HAVE_ECC224)
+#elif defined(HAVE_ECC224) && !defined(ECC_WEAK_CURVES)
     #define MAX_ECC_BITS    224
 #elif defined(HAVE_ECC192)
     #define MAX_ECC_BITS    192

wolfssl/wolfcrypt/settings.h

@@ -1749,6 +1749,13 @@ extern void uITRON4_free(void *p) ;
         #define HAVE_ALL_CURVES
     #endif
 #endif
+#ifndef ECC_WEAK_CURVES
+    /* if building TLS to enable < 224 then allow weak curves */
+    /* Note: ECC 224-bit is equiv to RSA 2048 bit */
+    #if defined(WOLFSSL_MIN_ECC_BITS) && WOLFSSL_MIN_ECC_BITS < 224
+        #define ECC_WEAK_CURVES
+    #endif
+#endif
 
 /* ECC Configs */
 #ifdef HAVE_ECC