Add PluginLoader class

- PluginLoader::verify can be used to check if the plugin has a valid
(SHA512/RSA 4096) signature.
- Uses nn OpenSSL public key that is embedded during the compile.

2 files changed, 90 insertions, 0 deletions

diff --git a/src/plugin/pluginloader.cpp b/src/plugin/pluginloader.cpp
new file mode 100644
index 0000000..d1626f2
--- /dev/null
+++ b/src/plugin/pluginloader.cpp
@@ -0,0 +1,77 @@
+#include "pluginloader.h"
+#include <QFile>
+#include <openssl/evp.h>
+#include <openssl/pem.h>
+#include "publicKey.h"
+#include <spdlog/spdlog.h>
+
+PluginLoader::PluginLoader(const QString &fileName, QObject *parent)
+    : QPluginLoader(fileName, parent)
+{
+}
+
+bool PluginLoader::verify(const char *hashName) const
+{
+    const QString sigName = this->fileName() + ".sig";
+    if(!QFile::exists(sigName)) {
+        spdlog::error("Signature does not exist: {}", qUtf8Printable(sigName));
+        return false;
+    }
+
+    auto *bio = BIO_new_mem_buf(publicKey_pem, publicKey_pem_len);
+    Q_CHECK_PTR(bio);
+
+    auto *key = PEM_read_bio_PUBKEY(bio, NULL, NULL, NULL);
+    Q_CHECK_PTR(key);
+
+    auto *ctx = EVP_MD_CTX_new();
+    Q_CHECK_PTR(ctx);
+
+    const auto *md = EVP_get_digestbyname(hashName);
+    Q_CHECK_PTR(md);
+
+    int rc = EVP_DigestVerifyInit(ctx, NULL, md, NULL, key);
+    if(rc != 1) {
+        spdlog::error("DigestVerifyInit failed: %i", rc);
+        return false;
+    }
+
+    // read plugin into DigestVerifyUpdate
+    QFile plugin(this->fileName());
+    plugin.open(QIODevice::ReadOnly);
+    int len = plugin.size();
+    int read = 0;
+    auto *buf = new unsigned char[1024];
+    while(len > 0) {
+        read = plugin.read((char*) buf, 1024);
+        len -= read;
+
+        rc = EVP_DigestVerifyUpdate(ctx, buf, read);
+        if(rc != 1)
+            spdlog::error("DigestVerifyUpdate failed: %i", rc);
+    }
+    delete buf;
+    plugin.close();
+
+    // read signature into DigestVerifyFinal
+    QFile sigFile(sigName);
+    sigFile.open(QIODevice::ReadOnly);
+    const int sig_len = sigFile.size();
+    const auto* sig = [&sigFile, sig_len]() {
+        auto* buf = new unsigned char[sig_len];
+        sigFile.read((char*) buf, sig_len);
+        return buf;
+    }();
+    sigFile.close();
+
+    rc = EVP_DigestVerifyFinal(ctx, sig, sig_len);
+    delete sig;
+
+    if(rc == 1)
+        return true;
+    else {
+        spdlog::error("DigestVerifyFinal failed: %i", rc);
+        return false;
+    }
+}
+
diff --git a/src/plugin/pluginloader.h b/src/plugin/pluginloader.h
new file mode 100644
index 0000000..8d186aa
--- /dev/null
+++ b/src/plugin/pluginloader.h
@@ -0,0 +1,13 @@
+#include <QPluginLoader>
+
+class PluginLoader : public QPluginLoader
+{
+    Q_OBJECT
+
+public:
+    PluginLoader(const QString &fileName, QObject *parent = nullptr);
+    ~PluginLoader() = default;
+
+    bool verify(const char *hashName = "SHA256") const;
+};
+