LibCrypto: Add CTR cipher mode

Kernel: Changed fortuna implementation to use CTR mode instead of
manually implementing a counter.

Libraries/LibCrypto/Cipher/AES.h

@@ -30,6 +30,7 @@
 #include <AK/Vector.h>
 #include <LibCrypto/Cipher/Cipher.h>
 #include <LibCrypto/Cipher/Mode/CBC.h>
+#include <LibCrypto/Cipher/Mode/CTR.h>
 
 namespace Crypto {
 namespace Cipher {
@@ -110,6 +111,7 @@ private:
 class AESCipher final : public Cipher<AESCipherKey, AESCipherBlock> {
 public:
     using CBCMode = CBC<AESCipher>;
+    using CTRMode = CTR<AESCipher>;
 
     constexpr static size_t BlockSizeInBits = BlockType::BlockSizeInBits;
 

Libraries/LibCrypto/Cipher/Mode/CTR.h

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
+ * 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.
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <AK/StringView.h>
+#include <LibCrypto/Cipher/Mode/Mode.h>
+
+namespace Crypto {
+namespace Cipher {
+
+template<typename T>
+class CTR : public Mode<T> {
+public:
+    constexpr static size_t IVSizeInBits = 128;
+
+    virtual ~CTR() { }
+
+    template<typename... Args>
+    explicit constexpr CTR<T>(Args... args)
+        : Mode<T>(args...)
+    {
+    }
+
+    virtual String class_name() const override
+    {
+        StringBuilder builder;
+        builder.append(this->cipher().class_name());
+        builder.append("_CTR");
+        return builder.build();
+    }
+
+    virtual size_t IV_length() const override { return IVSizeInBits / 8; }
+
+    virtual Optional<ByteBuffer> encrypt(const ByteBuffer& in, ByteBuffer& out, Optional<ByteBuffer> ivec = {}) override
+    {
+        return this->encrypt_or_stream(&in, out, ivec);
+    }
+
+    Optional<ByteBuffer> key_stream(ByteBuffer& out, Optional<ByteBuffer> ivec = {})
+    {
+        return this->encrypt_or_stream(nullptr, out, ivec);
+    }
+
+    virtual void decrypt(const ByteBuffer& in, ByteBuffer& out, Optional<ByteBuffer> ivec = {}) override
+    {
+        (void)in;
+        (void)out;
+        (void)ivec;
+        // FIXME: Implement CTR decryption when it is needed.
+    }
+
+private:
+    static ByteBuffer increment(const ByteBuffer& in)
+    {
+        ByteBuffer new_buffer(in);
+        size_t* num_view = (size_t*)new_buffer.data();
+
+        for (size_t i = 0; i < in.size() / sizeof(size_t); ++i) {
+            if (num_view[i] == (size_t)-1) {
+                num_view[i] = 0;
+            } else {
+                num_view[i]++;
+                break;
+            }
+        }
+        return new_buffer;
+    }
+
+    Optional<ByteBuffer> encrypt_or_stream(const ByteBuffer* in, ByteBuffer& out, Optional<ByteBuffer> ivec)
+    {
+        size_t length;
+        if (in) {
+            ASSERT(in->size() <= out.size());
+            length = in->size();
+            if (length == 0)
+                return {};
+        } else {
+            length = out.size();
+        }
+
+        auto& cipher = this->cipher();
+
+        // FIXME: We should have two of these encrypt/decrypt functions that
+        //        we SFINAE out based on whether the Cipher mode needs an ivec
+        ASSERT(ivec.has_value());
+        auto iv = ivec.value();
+
+        typename T::BlockType block { cipher.padding_mode() };
+        size_t offset { 0 };
+        auto block_size = cipher.block_size();
+
+        while (length > 0) {
+            block.overwrite(iv.slice_view(0, block_size));
+
+            cipher.encrypt_block(block, block);
+            if (in) {
+                block.apply_initialization_vector(in->data() + offset);
+            }
+            auto write_size = min(block_size, length);
+            out.overwrite(offset, block.get().data(), write_size);
+
+            iv = increment(iv);
+            length -= write_size;
+            offset += write_size;
+        }
+
+        return iv;
+    }
+};
+
+}
+}