Add Properties.EC_MAX_F2M_FIELD_SIZE for the org.bouncycastle.ec.max_f2m_field_size F2m field size bound (CVE-2024-29857) and use it in ECCurve rather than the inlined literal, mirroring the constant into the jdk1.4 overlay.

Author: dghgit

core/src/main/java/org/bouncycastle/math/ec/ECCurve.java

@@ -861,7 +861,7 @@ public static BigInteger inverse(int m, int[] ks, BigInteger x)
 
         private static FiniteField buildField(int m, int k1, int k2, int k3)
         {
-            if (m > Properties.asInteger("org.bouncycastle.ec.max_f2m_field_size", 1142))  // twice 571
+            if (m > Properties.asInteger(Properties.EC_MAX_F2M_FIELD_SIZE, 1142))  // twice 571
             {
                 throw new IllegalArgumentException("field size out of range: " + m);
             }

core/src/main/java/org/bouncycastle/util/Properties.java

@@ -309,6 +309,16 @@ public class Properties
      */
     public static final String BKS_MAX_IT_COUNT = "org.bouncycastle.bks.max_it_count";
 
+    /**
+     * Upper bound on the field size m accepted when building a characteristic-2 (F2m) elliptic curve.
+     * The field polynomial is evaluated when the curve is constructed, and the cost grows with m, so
+     * an unbounded value taken from a certificate's or key's explicit EC parameters is an import-time
+     * CPU-exhaustion vector (CVE-2024-29857). Default 1142 (twice the 571 of the largest standardised
+     * binary curve, B-571/K-571); a larger m is rejected with an {@code IllegalArgumentException}.
+     * Read via {@link #asInteger(String, int)}.
+     */
+    public static final String EC_MAX_F2M_FIELD_SIZE = "org.bouncycastle.ec.max_f2m_field_size";
+
     private Properties()
     {
     }

core/src/main/jdk1.4/org/bouncycastle/util/Properties.java

@@ -58,6 +58,13 @@ public class Properties
      */
     public static final String X509_SGP22_NAME_CONSTRAINTS = "org.bouncycastle.x509.sgp22_name_constraints";
 
+    /**
+     * Upper bound on the field size m accepted when building a characteristic-2 (F2m) elliptic curve;
+     * an unbounded m from explicit EC parameters is an import-time CPU-exhaustion vector
+     * (CVE-2024-29857). Default 1142 (twice 571).
+     */
+    public static final String EC_MAX_F2M_FIELD_SIZE = "org.bouncycastle.ec.max_f2m_field_size";
+
     private Properties()
     {
     }