LibCrypto: Make a better ASN.1 parser

And use it to parse RSA keys.
As a bonus, this one shouldn't be reading out of bounds or messing with
the stack (as much) anymore.

Userland/Libraries/LibCrypto/ASN1/ASN1.cpp

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCrypto/ASN1/ASN1.h>
+
+namespace Crypto::ASN1 {
+
+String kind_name(Kind kind)
+{
+    switch (kind) {
+    case Kind::Eol:
+        return "EndOfList";
+    case Kind::Boolean:
+        return "Boolean";
+    case Kind::Integer:
+        return "Integer";
+    case Kind::BitString:
+        return "BitString";
+    case Kind::OctetString:
+        return "OctetString";
+    case Kind::Null:
+        return "Null";
+    case Kind::ObjectIdentifier:
+        return "ObjectIdentifier";
+    case Kind::IA5String:
+        return "IA5String";
+    case Kind::PrintableString:
+        return "PrintableString";
+    case Kind::Utf8String:
+        return "UTF8String";
+    case Kind::UTCTime:
+        return "UTCTime";
+    case Kind::Sequence:
+        return "Sequence";
+    case Kind::Set:
+        return "Set";
+    }
+
+    return "InvalidKind";
+}
+
+String class_name(Class class_)
+{
+    switch (class_) {
+    case Class::Application:
+        return "Application";
+    case Class::Context:
+        return "Context";
+    case Class::Private:
+        return "Private";
+    case Class::Universal:
+        return "Universal";
+    }
+
+    return "InvalidClass";
+}
+
+String type_name(Type type)
+{
+    switch (type) {
+    case Type::Constructed:
+        return "Constructed";
+    case Type::Primitive:
+        return "Primitive";
+    }
+
+    return "InvalidType";
+}
+
+}