Make common byte to int conversion functions

Author: zeroSteiner

lib/rex/crypto.rb

@@ -27,4 +27,27 @@ def self.decrypt_aes256(iv, key, value)
   def self.rc4(key, value)
     Rc4.rc4(key, value)
   end
+
+  # Returns an integer represented as a byte array. Useful for certain key-related operations.
+  #
+  # @param bytes [String] The bytes to convert
+  # @return [Integer] The converted value.
+  def self.bytes_to_int(bytes)
+    bytes.each_byte.reduce(0) { |acc, byte| (acc << 8) | byte }
+  end
+
+  # Returns a byte array represented as a big-endian integer. Useful for certain key-related operations.
+  #
+  # @param bytes [String] The bytes to convert
+  # @return [Integer] The converted value.
+  def self.int_to_bytes(num)
+    bytes = []
+
+    while num > 0
+      bytes.unshift(num & 0xff)
+      num >>= 8
+    end
+
+    bytes.pack("C*")
+  end
 end

lib/rex/proto/ms_adts/key_credential.rb

@@ -25,8 +25,8 @@ def set_key(public_key, key_usage)
       when KEY_USAGE_NGC
         result = Rex::Proto::BcryptPublicKey.new
         result.key_length = public_key.n.num_bits
-        n = self.class.int_to_bytes(public_key.n)
-        e = self.class.int_to_bytes(public_key.e)
+        n = Rex::Crypto.int_to_bytes(public_key.n)
+        e = Rex::Crypto.int_to_bytes(public_key.e)
         result.exponent = e
         result.modulus = n
         result.prime1 = ''
@@ -136,8 +136,8 @@ def public_key
       when KEY_USAGE_NGC
         if raw_key_material.start_with?([Rex::Proto::BcryptPublicKey::MAGIC].pack('I'))
           result = Rex::Proto::BcryptPublicKey.read(raw_key_material)
-          exponent = OpenSSL::ASN1::Integer.new(bytes_to_int(result.exponent))
-          modulus = OpenSSL::ASN1::Integer.new(bytes_to_int(result.modulus))
+          exponent = OpenSSL::ASN1::Integer.new(Rex::Crypto.bytes_to_int(result.exponent))
+          modulus = OpenSSL::ASN1::Integer.new(Rex::Crypto.bytes_to_int(result.modulus))
           # OpenSSL's API has changed over time - constructing from DER has been consistent
           data_sequence = OpenSSL::ASN1::Sequence([modulus, exponent])
 
@@ -165,16 +165,6 @@ def add_entry(struct, identifier, data, insert_at_end: true)
       end
     end
 
-    def self.int_to_bytes(num)
-      str = num.to_s(16).rjust(2, '0')
-
-      [str].pack('H*')
-    end
-
-    def bytes_to_int(num)
-      num.unpack('H*')[0].to_i(16)
-    end
-
     # Sets self.key_hash based on the credential_entries value in the provided parameter
     # @param struct [MsAdtsKeyCredentialStruct] Its credential_entries value should have only those required to calculate the key_hash value (no key_id or key_hash)
     def calculate_key_hash(struct)