/*
 * Copyright (c) 2009, Stefan Walter
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *     * Redistributions of source code must retain the above
 *       copyright notice, this list of conditions and the
 *       following disclaimer.
 *     * 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.
 *     * The names of contributors to this software may not be
 *       used to endorse or promote products derived from this
 *       software without specific prior written permission.
 *
 * 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 OWNER 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.
 *
 *
 * CONTRIBUTORS
 *  Stef Walter <stef@memberwebs.com>
 *
 */

#include "mod_auth_singleid.h"

#include <opkele/association.h>
#include <opkele/exception.h>
#include <opkele/types.h>
#include <opkele/prequeue_rp.h>
#include <opkele/util.h>

using opkele::assoc_t;
using opkele::association;
using opkele::bad_input;
using opkele::dumb_RP;
using opkele::exception;
using opkele::exception_curl;
using opkele::failed_discovery;
using opkele::failed_lookup;
using opkele::failed_xri_resolution;
using opkele::id_res_bad_nonce;
using opkele::id_res_bad_return_to;
using opkele::id_res_failed;
using opkele::id_res_mismatch;
using opkele::no_endpoint;
using opkele::openid_endpoint_t;
using opkele::openid_message_t;
using opkele::params_t;
using opkele::prequeue_RP;
using opkele::secret_t;

using std::string;
using std::vector;

typedef std::list<std::string> string_list;

/* -----------------------------------------------------------------------------
 * UTILITY
 */

class LockShared
{
public:
	LockShared()
		{ sid_shared_lock (); }
	~LockShared()
		{ sid_shared_unlock (); }
};


static int
parse_number (const string& str)
{
	char *end = NULL;
	int result = strtoul (str.c_str(), &end, 10);
	if (!end || *end != '\0')
		result = 0;
	return result;
}

static string
format_number (int num)
{
	char buf[64];
	snprintf (buf, sizeof (buf), "%d", num);
	return string(buf);
}

static void
parse_query_string (const char *qs, params_t &params)
{
	string pair, key, value;
	const char *at;

	if (qs == NULL)
		return;

	while (*qs != 0) {
		at = strchr (qs, '&');
		if (at == NULL)
			at = qs + strlen (qs);
		pair = string(qs, at);
		string::size_type loc = pair.find('=', 0);
		if (loc != string::npos) {
			key = pair.substr (0, loc);
			value = pair.substr (loc + 1);
		} else {
			key = pair;
			value = "";
		}

		params[opkele::util::url_decode(key)] = opkele::util::url_decode(value);
		if (*at == 0)
			break;
		qs = at + 1;
	}
}

static void
filter_prefixed_params (params_t &params, params_t &openid, const string& prefix)
{
	/*
	 * Expects message to have openid. prefix present, and strips
	 * openid. prefix from output
	 */

	for (params_t::iterator it = params.begin(); it != params.end(); ) {
		const string& name = it->first;
		if (name.find (prefix) == 0) {
			openid[name.substr(prefix.length())] = it->second;

			/* We erase an increment together, must use post-increment operator */
			params.erase (it++);
		} else {
			/* Did not match, just go to next element */
			++it;
		}
	}
}

static void
filter_listed_params (const params_t &params, params_t &listed, const string& list)
{
	/* Expects message to have openid. prefix stripped from params */

	if(!params.has_param(list))
		return;

	string slist = params.get_param(list);
	string::size_type pos = 0;
	for (;;) {
		string::size_type at = slist.find(',', pos);
		string name = slist.substr(pos, at - pos);
		if(params.has_param(name))
			listed[name] = params.get_param(name);
		if(at == string::npos)
			return;
		pos = at + 1;
	}
}

/* -----------------------------------------------------------------------------
 * CONSUMER CLASS
 */

class Consumer :
	public prequeue_RP
{
private: // types
	typedef vector<openid_endpoint_t> endpoints;

public: // interface
	Consumer(const string& url, sid_storage_t *store)
		: _store(store), _url(url), _index(0)
		{ }

	bool is_dumb() const
		{ return _store ? false : true; }
	bool has_assoc(const string& handle) const;

public: // overrides

	virtual void begin_queueing()
		{ _endpoints.clear(); _index = 0; }

	virtual void queue_endpoint(const openid_endpoint_t& oep)
		{ _endpoints.push_back(oep); }

	virtual const openid_endpoint_t& get_endpoint() const;

	virtual void next_endpoint()
		{ _index++; }

	virtual void set_normalized_id(const string& nid)
		{ _normalized = nid; }

	virtual const string get_normalized_id() const
		{ return _normalized; }

	virtual const string get_this_url() const
		{ return _url; }

	virtual assoc_t store_assoc(const string& server, const string& handle,
	                            const string& type, const secret_t& secret,
	                            int expires_in);

	virtual assoc_t find_assoc(const string& server);

	virtual assoc_t retrieve_assoc(const string& server, const string& handle);

	virtual void invalidate_assoc(const string& server, const string& handle);

	virtual void check_nonce(const string& server, const string& nonce);

private: // data
	sid_storage_t *_store;
	endpoints _endpoints;
	string _normalized;
	string _url;
	endpoints::size_type _index;
};

const openid_endpoint_t&
Consumer::get_endpoint() const
{
	if (_index >= _endpoints.size())
		throw no_endpoint("no more endpoints");
	return _endpoints[_index];
}

assoc_t
Consumer::store_assoc(const string& server, const string& handle,
                      const string& type, const secret_t& secret,
                      int expires_in)
{
	sid_assoc_t data;
	int res;

	if (!_store)
		throw dumb_RP("no storage initialized");

	data.server = server.c_str();
	data.handle = handle.c_str();
	data.type = type.c_str();
	data.secret = &(secret.front());
	data.n_secret = secret.size();
	data.expires = expires_in;

	{
		LockShared lock; /* scoped lock */
		res = sid_storage_store_assoc (_store, &data);
	}

	if (!res)
		throw dumb_RP("association data was too large to fit in shared storage");

	return assoc_t(new association(server, handle, type, secret, expires_in, false));
}

bool
Consumer::has_assoc(const string& handle) const
{
	sid_assoc_t data = { 0, };
	int res;

	if (!_store)
		return false;

	{
		LockShared lock;
		res = sid_storage_find_assoc (_store, NULL, handle.c_str(), &data);
	}

	return res ? true : false;
}

assoc_t
Consumer::find_assoc(const string& server)
{
	sid_assoc_t data = { 0, };
	association *assoc = NULL;

	if (!_store)
		throw dumb_RP("no storage initialized");

	{
		LockShared lock;
		if (sid_storage_find_assoc (_store, server.c_str(), NULL, &data)) {
			secret_t secret;
			secret.assign(data.secret, data.secret + data.n_secret);
			assoc = new association(data.server, data.handle, data.type,
			                        secret, data.expires, false);
		}
	}

	if (!assoc)
		throw failed_lookup("could not find association for server: " + server);

	return assoc_t(assoc);
}

assoc_t
Consumer::retrieve_assoc(const string& server, const string& handle)
{
	sid_assoc_t data = { 0, };
	association *assoc = NULL;

	if (!_store)
		throw dumb_RP("no storage initialized");

	{
		LockShared lock;
		if (sid_storage_find_assoc (_store, server.c_str(), handle.c_str(), &data)) {
			secret_t secret;
			secret.assign(data.secret, data.secret + data.n_secret);
			assoc = new association(data.server, data.handle, data.type,
			                        secret, data.expires, false);
		}
	}

	if (!assoc)
		throw failed_lookup("could not retrieve association for server: " + server);

	return assoc_t(assoc);
}

void
Consumer::invalidate_assoc(const string& server, const string& handle)
{
	if (!_store)
		throw dumb_RP("no storage initialized");

	LockShared lock;
	sid_storage_invalidate_assoc (_store, server.c_str(), handle.c_str());
}

void
Consumer::check_nonce(const string& server, const string& nonce)
{
	int res = 0;

	if (_store) {
		LockShared lock;
		res = sid_storage_check_nonce (_store, server.c_str(), nonce.c_str());
	}

	if (res == 1)
		throw id_res_bad_nonce ("nonce is too old, or has already been used");
}

/* -----------------------------------------------------------------------
 * AUTHENTICATION
 */

static void
request_ax_attributes (sid_request_t *req, openid_message_t &message, sid_attribute_t *attrs)
{
	sid_attribute_t *attr;

	/* Request attributes for attribute exchange */
	if (!attrs)
		return;

	message["ns.ax"] = "http://openid.net/srv/ax/1.0";
	message["ax.mode"] = "fetch_request";

	string required, available;
	for (attr = attrs; attr; attr = attr->next) {

		/* Request the attribute */
		string field("ax.type.");
		field.append(attr->alias);
		message[field] = attr->url;

		/* Add to our reqired list */
		string& list = attr->required ? required : available;
		if(!list.empty())
			list.append(",");
		list.append(attr->alias);

		/* How many to request? */
		if (attr->count != 1) {
			field.assign("ax.count.");
			field.append(attr->alias);
			if (attr->count == 0)
				message[field] = "unlimited";
			else
				message[field] = format_number (attr->count);
		}
	}

	if(!required.empty())
		message["ax.required"] = required;
	if(!available.empty())
		message["ax.if_available"] = available;
}

static void
process_ax_values (sid_request_t *req, sid_attribute_t *attr, const string_list& values)
{
	const char** array = new const char*[values.size() + 1];
	if (!array) {
		sid_request_log_error (req, "out of memory", NULL);
		return;
	}

	int i = 0;
	for(string_list::const_iterator it = values.begin(); it != values.end(); ++it, ++i)
		array[i] = it->c_str();
	array[i] = NULL;

	sid_request_attribute_values (req, attr, array, values.size());
	delete [] array;
}

static void
parse_ax_attributes (sid_request_t *req, params_t &message, sid_attribute_t *attrs)
{
	/* Build a list of all signed params */
	params_t checked;
	filter_listed_params(message, checked, "signed");

	/* Look through and find ax namespace */
	string prefix;
	for (params_t::iterator it = checked.begin(); it != checked.end(); ++it) {
		if(it->first.find("ns.") == 0 && it->second == "http://openid.net/srv/ax/1.0") {
			prefix = it->first.substr(3) + ".";
			break;
		}
	}

	if(prefix.empty())
		return;

	/* Look through and find all aliases */
	params_t aliases;
	string type_prefix = prefix + "type.";
	for (params_t::iterator it = checked.begin(); it != checked.end(); ++it) {
		 if(it->first.find(type_prefix) == 0)
			 aliases[it->second] = it->first.substr(type_prefix.length());
	}

	if(aliases.empty())
		return;

	/* Now pull out the values for the attributes we want */
	string_list values;
	for(sid_attribute_t *attr = attrs; attr; attr = attr->next) {
		if(!aliases.has_param(attr->url))
			continue;

		string alias = aliases.get_param(attr->url);
		values.clear();

		/* See if there's a count attribute */
		string field = prefix + "count." + alias;
		if(checked.has_param(field)) {

			/* Get each value in turn */
			int count = parse_number (checked.get_param(field));
			for(int i = 0; i < count; ++i) {
				field = prefix + "value." + alias + "." + format_number (i + 1);
				if (checked.has_param (field))
					values.push_back (checked.get_param (field));
			}

		/* No count, just a single value */
		} else {
			field = prefix + "value." + alias;
			if(checked.has_param(field))
				values.push_back(checked.get_param(field));
		}

		/* Send off values */
		process_ax_values(req, attr, values);
	}
}

static void
begin_auth (sid_request_t *req, Consumer &consumer, const string& trust_root,
            const string &identity, sid_attribute_t *attributes)
{
	params_t result;
	string redirect;

	/* We cannot authenticate anything but a GET request */
	if (strcmp (sid_request_method (req), "GET") != 0) {
		sid_request_respond_html (req, 401, "Must Login",
		                          "<h1>Must Login</h1><p>You must be logged in before you can complete this action.</p>",
		                          "<p><a href='", trust_root.c_str(), "'>Login</a></p>", NULL);
		return;
	}

	try {
		openid_message_t cm;
		consumer.initiate (identity);
		consumer.checkid_ (cm, opkele::mode_checkid_setup, consumer.get_this_url(), trust_root);
		request_ax_attributes (req, cm, attributes);
		redirect = cm.append_query (consumer.get_endpoint().uri);

	} catch (failed_xri_resolution &ex) {
		sid_request_respond_html (req, 503, "Invalid Identifier",
		                          "<h1>Invalid identifier</h1><p>Details: Could not resolve identity provider.</p>", NULL);
		sid_request_log_error (req, "failed xri resolution while while discovering identity provider", ex.what ());
		return;

	} catch (failed_discovery &ex) {
		sid_request_respond_html (req, 503, "Invalid Identifier",
		                          "<h1>Invalid identifier</h1><p>Details: Could not discover identity provider.</p>", NULL);
		sid_request_log_error (req, "failed discovery while while discovering identity provider", ex.what ());
		  return;

	} catch (bad_input &ex) {
		sid_request_respond_headers (req, 500, "Internal Server Error", NULL);
		sid_request_log_error (req, "bad input to libopkele", ex.what());
		return;

	} catch (no_endpoint &ex) {
		sid_request_respond_html (req, 503, "No Identity Provider",
		                          "<h1>No identity provider</h1><p>Details: Could not contact a valid identity provider to authenticate you.</p>", NULL);
		sid_request_log_error (req, "no more endpoints", ex.what());
		return;

	} catch (exception_curl &ex) {
		sid_request_respond_html (req, 503, "Bad Identity Provider",
		                          "<h1>Bad identity provider</h1><p>Details: Could not communicate with the identity provider to authenticate you.</p>", NULL);
		sid_request_log_error (req, "could not contact identity provider", ex.what());
		return;

	} catch (exception &ex) {
		sid_request_respond_headers (req, 500, NULL, NULL);
		sid_request_log_error (req, "error while while discovering identity provider", ex.what());
		return;
	}

	sid_request_respond_headers (req, 302, "Found",
	                             "Location", redirect.c_str(),
	                             "Cache-Control", "no-cache",
	                             NULL);
}

static void
complete_auth (sid_request_t *req, Consumer &consumer, params_t &params,
               sid_attribute_t *attributes, bool &finished)
{
	try {
		finished = true;
		consumer.id_res(params);
		string identity = consumer.get_claimed_id();
		sid_request_authenticated (req, identity.c_str());
		parse_ax_attributes(req, params, attributes);
	} catch (id_res_mismatch &ex) {
		sid_request_respond_headers (req, 403, "Signature mismatch", NULL);
		sid_request_log_error (req, "signature did not match data", ex.what());
	} catch (bad_input &ex) {
		sid_request_respond_headers (req, 403, "Bad authentication input", NULL);
		sid_request_log_error (req, "bad input", ex.what());
	} catch (id_res_bad_return_to &ex) {
		sid_request_respond_headers (req, 403, "Bad authenticated address", NULL);
		sid_request_log_error (req, "bad return to", ex.what());
	} catch (id_res_failed &ex) {
		/* If we don't have this association, then try again */
		if (params.has_param("assoc_handle") && !consumer.has_assoc(params.get_param("assoc_handle"))) {
			sid_request_log_error (req, "response from invalid association, retrying authentication", NULL);
			finished = false;
		} else {
			sid_request_respond_headers (req, 503, "Service error, try again", NULL);
			sid_request_log_error (req, "checking response failed", ex.what());
		}
	} catch (exception &ex) {
		sid_request_respond_headers (req, 500, NULL, NULL);
		sid_request_log_error (req, "error while completing authentication", ex.what());
	}
}

static void
cancelled_auth (sid_request_t *req, Consumer &consumer, params_t &params, const string& return_to)
{
	sid_request_respond_html (req, 401, "Login Cancelled",
	                          "<h1>Login Cancelled</h1>"
	                          "<p>This website requires authentication, but the authentication process was cancelled.</p>",
	                          "<p><a href='", return_to.c_str(), "'>Retry login</a></p>", NULL);
}

extern "C" void
sid_consumer_authenticate(sid_request_t *req, sid_storage_t *store,
                          const char *trust_root, const char *identity,
                          sid_attribute_t *attributes)
{
	params_t params;
	params_t openid;

	assert (req);

	const char *qs;

	if (strcmp (sid_request_method (req), "POST") == 0)
		qs = sid_request_form (req);
	else
		qs = sid_request_qs (req);

	parse_query_string (qs, params);
	filter_prefixed_params (params, openid, "openid.");

	string url = sid_request_url (req, 1);
	if (!params.empty())
		url = params.append_query (url, "");
	Consumer consumer(url, store);

	/* Returning (hopefully successful) authentication */
	if (openid.has_param("assoc_handle")) {
		bool finished = true;
		complete_auth (req, consumer, openid, attributes, finished);
		if (finished)
			return;
	}

	/* Returning cancelled authentication */
	if (openid.has_param("mode") && openid.get_param("mode") == "cancel") {
		cancelled_auth (req, consumer, openid, url);

	/* Begin a new authentication */
	} else {
		if (!trust_root)
			trust_root = sid_request_url (req, 0);
		begin_auth (req, consumer, trust_root, identity, attributes);
	}
}