* Added plugin support

* Improved Filer (LocalFiler)
* Supports Explicit SSL/TLS with OpenSSL/Crypto
* Fixed most of the bugs that drove me nuts.
* Properly handled socket closes
* Improved socket cleanup
* Buffered file downloads
* Lots 'o errors!

I did it again! I made a single commit with everything!

src/plugins/auth_pam/auth_pam.cpp

@@ -0,0 +1,131 @@
+#include "auth_plugin.h"
+#include <security/pam_appl.h>
+#include <pwd.h>
+#include <grp.h>
+#include <string>
+#include <cstring>
+#include <memory>
+
+class PAMAuthPlugin : public Auth {
+private:
+	std::string service_name;
+	uid_t user_uid;
+	gid_t user_gid;
+
+	// PAM Conversation function
+	static int pam_conv_func(int num_msg, const struct pam_message **msg,
+							struct pam_response **resp, void *appdata_ptr) {
+		const char* password = static_cast<const char*>(appdata_ptr);
+		if (!password) return PAM_CONV_ERR;
+
+		// Allocate memory for responses
+		*resp = static_cast<pam_response*>(calloc(num_msg, sizeof(struct pam_response)));
+		if (*resp == nullptr) return PAM_CONV_ERR;
+
+		// Handle messages
+		for (int i = 0; i < num_msg; i++) {
+			if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF) {
+				(*resp)[i].resp = strdup(password);
+				if ((*resp)[i].resp == nullptr) {
+					for (int j = 0; j < i; j++) {
+						free((*resp)[j].resp);
+					}
+					free(*resp);
+					*resp = nullptr;
+					return PAM_CONV_ERR;
+				}
+				(*resp)[i].resp_retcode = 0;
+			} else {
+				(*resp)[i].resp = nullptr;
+				(*resp)[i].resp_retcode = 0;
+			}
+		}
+
+		return PAM_SUCCESS;
+	}
+
+public:
+	PAMAuthPlugin() : service_name("ftpd") {}
+
+	virtual bool initialize(const std::map<std::string, std::string>& config) override {
+		// Get PAM service name with default
+		auto service_it = config.find("pam_service");
+		service_name = (service_it != config.end()) ? service_it->second : "ftpd";
+		
+		auto chroot_it = config.find("chroot");
+		this->setChroot((chroot_it != config.end()) ? 
+					 (chroot_it->second == "on" || chroot_it->second == "true" || chroot_it->second == "yes") : 
+					 true);
+		
+		return true;
+	}
+
+	virtual bool authenticate(ClientAuthDetails* auth_data) override {
+		if (!auth_data || !auth_data->username[0] || !auth_data->password[0]) {
+			logger->print(LOGLEVEL_ERROR, "auth_pam: Cannot use empty auth data");
+			return false;
+		}
+
+		struct pam_conv conv;
+		conv.conv = pam_conv_func;
+		conv.appdata_ptr = static_cast<void*>(auth_data->password);
+
+		pam_handle_t* pamh = nullptr;
+
+		// Start PAM session
+		int retval = pam_start(service_name.c_str(), auth_data->username, &conv, &pamh);
+		if (retval != PAM_SUCCESS) {
+			logger->print(LOGLEVEL_ERROR, "auth_pam: Failed to start PAM: %s", 
+						 pamh ? pam_strerror(pamh, retval) : "Unknown error");
+			if (pamh) pam_end(pamh, retval);
+			return false;
+		}
+
+		// Authenticate user
+		retval = pam_authenticate(pamh, 0);
+		if (retval != PAM_SUCCESS) {
+			logger->print(LOGLEVEL_ERROR, "auth_pam: Authentication failed: %s", 
+						 pam_strerror(pamh, retval));
+			pam_end(pamh, retval);
+			return false;
+		}
+
+		// Check account validity
+		retval = pam_acct_mgmt(pamh, 0);
+		if (retval != PAM_SUCCESS) {
+			logger->print(LOGLEVEL_ERROR, "auth_pam: Account validation failed: %s", 
+						 pam_strerror(pamh, retval));
+			pam_end(pamh, retval);
+			return false;
+		}
+
+		// End PAM session
+		pam_end(pamh, PAM_SUCCESS);
+
+		// Get user info
+		struct passwd* pw = getpwnam(auth_data->username);
+		if (!pw) {
+			logger->print(LOGLEVEL_ERROR, "auth_pam: Failed to get user info for %s", 
+						 auth_data->username);
+			return false;
+		}
+
+		// Store user info
+		user_uid = pw->pw_uid;
+		user_gid = pw->pw_gid;
+
+		// Set home directory
+		if (pw->pw_dir) {
+			strncpy(auth_data->home_dir, pw->pw_dir, sizeof(auth_data->home_dir) - 1);
+			auth_data->home_dir[sizeof(auth_data->home_dir) - 1] = '\0';
+		}
+
+		return true;
+	}
+
+	virtual bool isPasswordRequired() override {
+		return true;
+	}
+};
+
+IMPLEMENT_AUTH_PLUGIN(PAMAuthPlugin, "pam", "PAM-based local authentication", "1.0.0")