From de19233dd72bb28edabdf26b02a385592147c5a7 Mon Sep 17 00:00:00 2001
From: Eric Mertens <emertens@galois.com>
Date: Tue, 28 Jan 2025 19:02:30 -0800
Subject: [PATCH] challenge.cpp

---
 challenge.cpp | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++
 challenge.hpp | 24 ++++++++++++++
 2 files changed, 114 insertions(+)
 create mode 100644 challenge.cpp
 create mode 100644 challenge.hpp

diff --git a/challenge.cpp b/challenge.cpp
new file mode 100644
index 0000000..9de6a64
--- /dev/null
+++ b/challenge.cpp
@@ -0,0 +1,90 @@
+#include "challenge.hpp"
+
+#include "openssl_errors.hpp"
+
+#include <mybase64.hpp>
+#include <openssl/evp.h>
+#include <openssl/rsa.h>
+
+#include <boost/log/trivial.hpp>
+
+#include <memory>
+#include <string>
+
+Challenge::Challenge(EVP_PKEY_Ref key, Connection & connection)
+    : key_{std::move(key)}
+    , connection_{connection}
+    {}
+
+
+auto Challenge::stop() -> void
+{
+    slot_.disconnect();
+    buffer_.clear();
+}
+
+auto Challenge::on_ircmsg(IrcCommand cmd, const IrcMsg &msg) -> void {
+        switch (cmd) {
+        default: break;
+        case IrcCommand::RPL_RSACHALLENGE2:
+            buffer_ += msg.args[1];
+            break;
+        case IrcCommand::ERR_NOOPERHOST:
+            BOOST_LOG_TRIVIAL(error) << "Challenge: No oper host";
+            stop();
+            break;
+        case IrcCommand::RPL_YOUREOPER:
+            BOOST_LOG_TRIVIAL(error) << "Challenge: Already oper";
+            stop();
+            break;
+        case IrcCommand::RPL_ENDOFRSACHALLENGE2:
+            {
+                EVP_PKEY_CTX_Ref ctx;
+                unsigned int digestlen = 160;
+                unsigned char digest[160];
+                size_t len = mybase64::decoded_size(buffer_.size());
+                std::vector<unsigned char> ciphertext(len, 0);
+
+                if (not mybase64::decode(buffer_, reinterpret_cast<char*>(ciphertext.data()), &len)) goto error;
+                ciphertext.resize(len);
+
+                // Setup decryption context
+                ctx.reset(EVP_PKEY_CTX_new(key_.get(), nullptr));
+                if (ctx.get() == nullptr) goto error;
+                if (1 != EVP_PKEY_decrypt_init(ctx.get())) goto error;
+                if (0 <= EVP_PKEY_CTX_set_rsa_padding(ctx.get(), RSA_PKCS1_OAEP_PADDING)) goto error;
+
+                // Determine output size
+                if (1 != EVP_PKEY_decrypt(ctx.get(), nullptr, &len, ciphertext.data(), ciphertext.size())) goto error;
+                buffer_.resize(len);
+
+                // Decrypt ciphertext
+                EVP_PKEY_decrypt(ctx.get(), reinterpret_cast<unsigned char*>(buffer_.data()), &len, ciphertext.data(), ciphertext.size());
+
+                // Hash the decrypted message
+                if (1 != EVP_Digest(buffer_.data(), buffer_.size(), digest, &digestlen, EVP_sha1(), nullptr)) goto error;
+
+                // Construct reply as '+' and base64 encoded digest
+                buffer_.resize(mybase64::encoded_size(digestlen) + 1);
+                buffer_[0] = '+';
+                mybase64::encode(std::string_view{(char*)digest, digestlen}, buffer_.data() + 1);
+
+                connection_.send_challenge(buffer_);
+
+                stop();
+                return;
+
+error:
+                log_openssl_errors("Challenge: ");
+                stop();
+            }
+        }
+    }
+
+auto Challenge::start(Connection &connection, const std::string_view user, EVP_PKEY_Ref ref) -> std::shared_ptr<Challenge>
+{
+    auto self = std::make_shared<Challenge>(std::move(ref), connection);
+    connection.sig_ircmsg.connect([self](auto cmd, auto &msg) { self->on_ircmsg(cmd, msg); });
+    connection.send_challenge(user);
+    return self;
+}
diff --git a/challenge.hpp b/challenge.hpp
new file mode 100644
index 0000000..800b5f2
--- /dev/null
+++ b/challenge.hpp
@@ -0,0 +1,24 @@
+#pragma once
+
+#include "connection.hpp"
+#include "ref.hpp"
+
+#include <boost/signals2/connection.hpp>
+
+#include <memory>
+#include <string>
+
+class Challenge : std::enable_shared_from_this<Challenge>
+{
+    EVP_PKEY_Ref key_;
+    Connection &connection_;
+    boost::signals2::scoped_connection slot_;
+    std::string buffer_;
+
+    auto on_ircmsg(IrcCommand cmd, const IrcMsg &msg) -> void;
+
+public:
+    Challenge(EVP_PKEY_Ref, Connection &);
+    auto stop() -> void;
+    static auto start(Connection &, std::string_view user, EVP_PKEY_Ref) -> std::shared_ptr<Challenge>;
+};