crypto/x509: validate certificates with unsorted SET values in RDNs

src/crypto/x509/parser.go

@@ -153,11 +153,26 @@ func parseName(raw cryptobyte.String) (*pkix.RDNSequence, error) {
 		if !raw.ReadASN1(&set, cryptobyte_asn1.SET) {
 			return nil, errors.New("x509: invalid RDNSequence")
 		}
+		var prevAttr cryptobyte.String
 		for !set.Empty() {
 			var atav cryptobyte.String
-			if !set.ReadASN1(&atav, cryptobyte_asn1.SEQUENCE) {
+			var rawAttr cryptobyte.String
+			if !set.ReadASN1Element(&rawAttr, cryptobyte_asn1.SEQUENCE) {
 				return nil, errors.New("x509: invalid RDNSequence: invalid attribute")
 			}
+
+			// Compare each attribute with the previous one
+			// In DER, they must be in ascending order when compared as octet strings
+			if prevAttr != nil && bytes.Compare(prevAttr, rawAttr) > 0 {
+				return nil, errors.New("x509: invalid RDNSequence: SET values not in ascending order")
+			}
+
+			prevAttr = rawAttr
+
+			if !rawAttr.ReadASN1(&atav, cryptobyte_asn1.SEQUENCE) {
+				return nil, errors.New("x509: invalid RDNSequence: invalid attribute")
+			}
+
 			var attr pkix.AttributeTypeAndValue
 			if !atav.ReadASN1ObjectIdentifier(&attr.Type) {
 				return nil, errors.New("x509: invalid RDNSequence: invalid attribute type")

src/crypto/x509/parser_test.go

@@ -251,3 +251,28 @@ d5l1tRhScKu2NBgm74nYmJxJYgvuTA38wGhRrGU=
 		}
 	}
 }
+
+func TestUnsortedSETInRDN(t *testing.T) {
+	// This certificate has an unsorted SET in its RDN
+	certPEM := `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil {
+		t.Fatalf("Failed to decode PEM block")
+	}
+
+	_, err := ParseCertificate(block.Bytes)
+	if err == nil || err.Error() != "x509: invalid RDNSequence: SET values not in ascending order" {
+		t.Errorf(`ParseCertificate() = %v; want = "x509: invalid RDNSequence: SET values not in ascending order"`, err)
+	}
+}