Add DH parameters validation

Signed-off-by: Knut Ahlers <knut@ahlers.me>

validate.go

@@ -0,0 +1,104 @@
+package dhparam
+
+import (
+	"math/big"
+
+	"github.com/pkg/errors"
+)
+
+const DH_CHECK_P_NOT_PRIME = 0x01
+const DH_CHECK_P_NOT_SAFE_PRIME = 0x02
+const DH_UNABLE_TO_CHECK_GENERATOR = 0x04
+const DH_NOT_SUITABLE_GENERATOR = 0x08
+const DH_CHECK_Q_NOT_PRIME = 0x10
+const DH_CHECK_INVALID_Q_VALUE = 0x20
+const DH_CHECK_INVALID_J_VALUE = 0x40
+
+// ErrAllParametersOK is defined to check whether the returned error from Check is indeed no error
+// For simplicity reasons it is defined as an error instead of an additional result parameter
+var ErrAllParametersOK = errors.New("DH parameters appear to be ok.")
+
+// Check returns a number of errors and an "ok" bool. If the "ok" bool is set to true, still one
+// error is returned: ErrAllParametersOK. If "ok" is false, the error list will contain at least
+// one error not being equal to ErrAllParametersOK.
+func (d DH) Check() ([]error, bool) {
+	var (
+		result = []error{}
+		ok     = true
+	)
+
+	i := d.check()
+
+	if i&DH_CHECK_P_NOT_PRIME > 0 {
+		result = append(result, errors.New("WARNING: p value is not prime"))
+		ok = false
+	}
+
+	if i&DH_CHECK_P_NOT_SAFE_PRIME > 0 {
+		result = append(result, errors.New("WARNING: p value is not a safe prime"))
+		ok = false
+	}
+
+	if i&DH_CHECK_Q_NOT_PRIME > 0 {
+		result = append(result, errors.New("WARNING: q value is not a prime"))
+		ok = false
+	}
+
+	if i&DH_CHECK_INVALID_Q_VALUE > 0 {
+		result = append(result, errors.New("WARNING: q value is invalid"))
+		ok = false
+	}
+
+	if i&DH_CHECK_INVALID_J_VALUE > 0 {
+		result = append(result, errors.New("WARNING: j value is invalid"))
+		ok = false
+	}
+
+	if i&DH_UNABLE_TO_CHECK_GENERATOR > 0 {
+		result = append(result, errors.New("WARNING: unable to check the generator value"))
+		ok = false
+	}
+
+	if i&DH_NOT_SUITABLE_GENERATOR > 0 {
+		result = append(result, errors.New("WARNING: the g value is not a generator"))
+		ok = false
+	}
+
+	if i == 0 {
+		result = append(result, ErrAllParametersOK)
+	}
+
+	return result, ok
+}
+
+func (d DH) check() int {
+	var ret int
+
+	// Check generator
+	switch d.G {
+	case 2:
+		l := new(big.Int)
+		if l.Mod(d.P, big.NewInt(24)); l.Int64() != 11 {
+			ret |= DH_NOT_SUITABLE_GENERATOR
+		}
+	case 5:
+		l := new(big.Int)
+		if l.Mod(d.P, big.NewInt(10)); l.Int64() != 3 && l.Int64() != 7 {
+			ret |= DH_NOT_SUITABLE_GENERATOR
+		}
+	default:
+		ret |= DH_UNABLE_TO_CHECK_GENERATOR
+	}
+
+	if !d.P.ProbablyPrime(1) {
+		ret |= DH_CHECK_P_NOT_PRIME
+	} else {
+		t1 := new(big.Int)
+		t1.Rsh(d.P, 1)
+		if !t1.ProbablyPrime(1) {
+			ret |= DH_CHECK_P_NOT_SAFE_PRIME
+		}
+	}
+
+	return ret
+}

validate_test.go

@@ -0,0 +1,79 @@
+package dhparam
+
+import "testing"
+
+func TestCheckOwn(t *testing.T) {
+	dh, err := Generate(512, 2, nil)
+	if err != nil {
+		t.Fatalf("Could not generate DH parameters: %s", err)
+	}
+
+	errs, ok := dh.Check()
+	if !ok {
+		t.Fatalf("DH validation was not successful: %#v", errs)
+	}
+}
+
+func TestOpenSSLGenerated(t *testing.T) {
+	tests := map[string]string{
+		"2_512bit": `-----BEGIN DH PARAMETERS-----
+MEYCQQCv5GjOovf4i4wQbQCHlb4sdf+ImR4o/m8+VeD3TbMIUlarHQAsLgXPQYsE
+g3+KzUc1W0W9AE28oTf6c6J/TcS7AgEC
+-----END DH PARAMETERS-----`,
+		"2_1024bit": `-----BEGIN DH PARAMETERS-----
+MIGHAoGBAJ/O4zueSGVilc8xRh8yqIqx2I78lVYX/2NwtkSkY81/r7/cjrbo0bZ0
+983B6BzCTJ4BPEpfmZ7IIXC4HhXShzHIXrJO1Cc+7m3041vEhgwyEXRKUbYBbYMm
+kWmCXuw4fuMI8cv4+jelYfgPjPG/XzJ0ZcCASDKgAtG4TzG4gDUDAgEC
+-----END DH PARAMETERS-----`,
+		"2_2048bit": `-----BEGIN DH PARAMETERS-----
+MIIBCAKCAQEA4OkpmW50f7zVyK0QcZStmT13MbiZndmgP9aky5TiRksr3tmdIx+J
+LI8jJD/Ru87hH6XSVNN0zUxPYf5n9U5lfzWwlzT0Rz+T2Ssh0DselobcPWwRMVox
+y28szYArdz0/tTyAbNzGMlJOXyKU9LTGZXXz32fllSMbvG+xNFOAA0iKl1O3I5uU
+hhVTCorRKs+uwMgjdhRyj/elm/xX4XjxPUB4unhmRBFUVbE3O/1Hoao9rjV0x/Xv
+CnrP4fQh75z+DkT4jKfyhHy4bCxLqR1GKkTLdTz213zjpTe58ubdx3GJwPBjCdCB
+fMPJHWPjj5gb9JaY+jTjvxVBeP4X4GwpIwIBAg==
+-----END DH PARAMETERS-----`,
+		"2_4096bit": `-----BEGIN DH PARAMETERS-----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=
+-----END DH PARAMETERS-----`,
+		"5_512bit": `-----BEGIN DH PARAMETERS-----
+MEYCQQDwi9IfzZY6rnmM757o8+gtl1YH8w3mdMg/JPfy35N5eJhvgx/TDyFuZUD7
+5T9I2sypdmbv3jWLbQzTBWFZV9xTAgEF
+-----END DH PARAMETERS-----`,
+		"5_1024bit": `-----BEGIN DH PARAMETERS-----
+MIGHAoGBAOhcZ2xhJuGJsXwhD9WthoJ2yaDTg1UQELgplC48sl9fAhEaWl7tSCSK
+kLr5DZu0znHjv9AWf8qMnyRMwDAXx0go3SaqrB+rNQjxNpmgssp841vLLSsttHiP
+M1PfJp2GVV8Er5dRnfPOBXvIryO0aRUtjKs2AOqEd0rWKdqQP80XAgEF
+-----END DH PARAMETERS-----`,
+		"5_2048bit": `-----BEGIN DH PARAMETERS-----
+MIIBCAKCAQEAp8Oe7MPt+RdKBX2ht+Ok9XpQohaagc6RyyPNUeNTXoKDoCcJu9fk
+gEg7EkjcAbjvOXkZhNWCCuXSra3qnjTCKcuvZFIJp5i3pYLlZl9d2qKo72fk25yN
+h4HbygtpufYL5PQMvhOGae/+dJyxjprzzQkQAUy6qiWqYEBc+OyCcYGIMjHVcf53
+1vg8L5j3k+Pi0aCWZcwxDzJDPfFpG1B3J0ELVZK1eLe4vcKmxBfDbuFyQ1AG22Gh
+OIwSXKyK6z5yuU9sZOsire0nnpOYWxE9blg3frfsFgb2bah7YtxQv75PtVYUuVUL
+FBUWAa1u8vuIzcZ/tLEADgImJ4TZmrsiLwIBBQ==
+-----END DH PARAMETERS-----`,
+	}
+
+	for key, encoded := range tests {
+		dh, err := Decode([]byte(encoded))
+		if err != nil {
+			t.Errorf("[%s] Was not able to decode: %s", key, err)
+		}
+
+		errs, ok := dh.Check()
+		if !ok {
+			t.Fatalf("[%s] DH validation was not successful: %#v", key, errs)
+		}
+	}
+}