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.

2025-07-30 02:37:28 +02:00 · 2020-10-16 15:14:02 -07:00
parent 62dca90e74
commit c697520826
6 changed files with 37 additions and 15 deletions
--- a/configure.ac
+++ b/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"
--- a/src/internal.c
+++ b/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;
--- a/src/tls.c
+++ b/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;
@ -4359,8 +4359,8 @@ int TLSX_ValidateSupportedCurves(WOLFSSL* ssl, byte first, byte second) {
                octets = 20;
                break;
        #endif /* HAVE_ECC_KOBLITZ */
-    #endif
-    #if defined(HAVE_ECC192) || defined(HAVE_ALL_CURVES)
+        #endif
+    #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);
@ -9958,7 +9958,7 @@ static int TLSX_PopulateSupportedGroups(WOLFSSL* ssl, TLSX** extensions)
    #endif /* HAVE_FIPS */
 #endif /* HAVE_ECC && HAVE_SUPPORTED_CURVES */

-                /* Add FFDHE supported groups. */
+            /* Add FFDHE supported groups. */
        #ifdef HAVE_FFDHE_8192
            if (8192/8 >= ssl->options.minDhKeySz &&
                                            8192/8 <= ssl->options.maxDhKeySz) {
--- a/wolfcrypt/src/ecc.c
+++ b/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)
--- a/wolfssl/wolfcrypt/ecc.h
+++ b/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
--- a/wolfssl/wolfcrypt/settings.h
+++ b/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