#include "config.h"

#include <sasl/sasl.h>
#include <sasl/saslplug.h>

#define LDAP_DEPRECATED 1
#include <ldap.h>
#include <lber.h>

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>

#define CANARY_VALUE "!DL!"

#define OPTION_SERVER  "delegateldap_uri"
#define OPTION_TLS     "delegateldap_tls"
#define OPTION_LDAPRC  "delegateldap_ldaprc"

/*
 * SETTINGS -------------------------------------------------------------------------
 * TODO: Move these to a configuration file or some such
 */

#define SETTINGS_URL "ldap://209.66.100.155"

typedef struct _supported_mechanisms {
	void *mutex;
	int loaded;
	struct berval **mechs;
} supported_mechanisms;

static supported_mechanisms *the_supported;

typedef struct _delegate_context {
	char canary[4];
	const char* mechanism;
	LDAP *ldap;
} delegate_context;

extern sasl_server_plug_init_t sasl_server_plug_init;

static void
log_message (const sasl_utils_t *utils, int level, const char *format, ...)
{
	char buf[1024];
	va_list va;

	va_start (va, format);
	vsnprintf (buf, sizeof (buf), format, va);
	buf[sizeof (buf) - 1] = 0;
	vfprintf (stderr, format, va);
	fputc ('\n', stderr);
	va_end (va);

	(utils->log) (utils->conn, level, "%s", buf);
}

static int
report_ldap_error (const sasl_utils_t *utils, int ldap, const char *format, ...)
{
	char buf[1024];
	va_list va;

	buf[0] = 0;

	if (format) {
		va_start (va, format);
		vsnprintf (buf, sizeof (buf), format, va);
		buf[sizeof (buf) - 1] = 0;
		va_end (va);
	}

	(utils->seterror) (utils->conn, 0, "%s%s%s",
	                   buf, buf[0] ? ": " : "", ldap_err2string (ldap));
	fprintf (stderr, "%s%s%s", buf, buf[0] ? ": " : "", ldap_err2string (ldap));
	fputc ('\n', stderr);

	switch (ldap) {
	case LDAP_MORE_RESULTS_TO_RETURN:
		return SASL_CONTINUE;
	case LDAP_SUCCESS:
		return SASL_OK;
	case LDAP_NO_MEMORY:
		return SASL_NOMEM;
	case LDAP_AUTH_UNKNOWN:
		return SASL_NOMECH;
	case LDAP_DECODING_ERROR:
		return SASL_BADPROT;
	}

	return SASL_FAIL;
}

static void
delegateldap_dispose (void *context, const sasl_utils_t *utils)
{
	delegate_context *ctx = (delegate_context*)context;

	if (!ctx)
		return;

	if (memcmp (ctx->canary, CANARY_VALUE, sizeof (ctx->canary)) != 0) {
		log_message (utils, SASL_LOG_ERR, "trying to dispose of invalid delegateldap mechanism");
		return;
	}

	if (ctx->ldap) {
		log_message (utils, SASL_LOG_NOTE, "closing ldap connection");
		ldap_unbind_ext_s (ctx->ldap, NULL, NULL);
	}
	ctx->ldap = NULL;
	memset (ctx, 0, sizeof (*ctx));

	utils->free (ctx);
}

static int
match_any_value (const char *match, ...)
{
	const char *value;
	va_list va;

	va_start (va, match);
	for (;;) {
		value = va_arg (va, const char*);
		if (!value)
			return 0;
		if (strcasecmp (match, value) == 0)
			return 1;
	}
}

static int
delegateldap_new (void *mech_context, sasl_server_params_t *sparams,
                  const char *challenge, unsigned challen, void **context)
{
	const char *mechanism;
	const char *option;
	delegate_context *ctx;
	int res, protocol, ret;

	*context = NULL;

	/* Make sure we have appropriate options */
	if ((sparams->utils->getopt) (sparams->utils->getopt_context, NULL,
			              OPTION_SERVER, &option, NULL) != SASL_OK) {
		log_message (sparams->utils, SASL_LOG_ERR,
		             "missing '%s' option in config file", OPTION_SERVER);
		return SASL_BADPARAM;
	}

	ctx = sparams->utils->malloc (sizeof (delegate_context));
	if (!ctx)
		return SASL_NOMEM;
	memset (ctx, 0, sizeof (delegate_context));
	memcpy (ctx->canary, CANARY_VALUE, sizeof (ctx->canary));

	/* We use the mech_context to boot strap the mechanism */
	mechanism = (const char*)mech_context;

	log_message (sparams->utils, SASL_LOG_NOTE, "initializing ldap connection to: %s", option);

	res = ldap_initialize (&ctx->ldap, option);
	if (res != LDAP_SUCCESS) {
		delegateldap_dispose (ctx, sparams->utils);
		return report_ldap_error (sparams->utils, res, "couldn't initialize ldap connection: %s", option);
	}

	protocol = LDAP_VERSION3;
	if (ldap_set_option (ctx->ldap, LDAP_OPT_PROTOCOL_VERSION, &protocol) != LDAP_OPT_SUCCESS) {
		delegateldap_dispose (ctx, sparams->utils);
		log_message (sparams->utils, SASL_LOG_ERR, "couldn't setup ldap connection to use version 3 protocol");
		return SASL_FAIL;
	}

	/* See if we should connect with TLS */
	(sparams->utils->getopt) (sparams->utils->getopt_context, NULL, OPTION_TLS, &option, NULL);
	if (option && match_any_value (option, "yes", "y", "on", "try", "demand", "true", NULL)) {

		/* Start the TLS thingy */
		res = ldap_start_tls_s (ctx->ldap, NULL, NULL);
		if (res != LDAP_SUCCESS) {
			ret = report_ldap_error (sparams->utils, res, "couldn't initialize TLS on the ldap connection");

			/* The configure requires that we have tls */
			if (match_any_value (option, "demand", NULL)) {
				delegateldap_dispose (ctx, sparams->utils);
				return ret;
			}
		}
	}

	ctx->mechanism = mechanism;
	*context = ctx;

	return SASL_OK;
}

static int
calculate_user (delegate_context *ctx, sasl_server_params_t *sparams,
                sasl_out_params_t *oparams)
{
	struct berval *auth;
	char *dn;
	char **parts;
	int res, ret;

	res = ldap_whoami_s (ctx->ldap, &auth, NULL, NULL);
	if (res != LDAP_SUCCESS)
		return report_ldap_error (sparams->utils, res, "couldn't determine logged in user name");

	/* Anonmyous authentication */
	if (!auth) {
		log_message (sparams->utils, SASL_LOG_NOTE, "anonymous user login");
		ret = (sparams->canon_user) (sparams->utils->conn, "anonymous", 0,
		                             SASL_CU_AUTHID | SASL_CU_AUTHZID, oparams);

	/* Use RDN as authenticator */
	} else {
		dn = strchr (auth->bv_val, ':');
		if (dn) {
			*dn = 0;
			++dn;
		} else {
			dn = auth->bv_val;
		}

		parts = ldap_explode_dn (dn, 1);
		if (!parts || !parts[0]) {
			log_message (sparams->utils, SASL_LOG_ERR,
			             "couldn't parse the user's dn: %s", auth->bv_val);
			ret = SASL_FAIL;
		} else {
			log_message (sparams->utils, SASL_LOG_NOTE, "user login: %s", parts[0]);
			ret = sparams->canon_user (sparams->utils->conn, parts[0], 0,
			                           SASL_CU_AUTHID | SASL_CU_AUTHZID, oparams);
		}

		if (parts)
			ldap_value_free (parts);

		ber_bvfree (auth);
	}

	return ret;
}

static int
delegateldap_step (void *context, sasl_server_params_t *sparams,
                   const char *clientin, unsigned clientinlen,
                   const char **serverout, unsigned *serveroutlen,
                   sasl_out_params_t *oparams)
{
	delegate_context *ctx = (delegate_context*)context;
	struct berval *scred = NULL;
	struct berval ccred;
	char *buffer;
	int ret;
	int res;

	*serverout = NULL;
	*serveroutlen = 0;

	ccred.bv_len = clientinlen;
	ccred.bv_val = (char*)clientin;

	log_message (sparams->utils, SASL_LOG_DEBUG,
	             "%d bytes of client request", ccred.bv_len);

	res = ldap_sasl_bind_s (ctx->ldap, NULL, ctx->mechanism, &ccred, NULL, NULL, &scred);

	if (res == LDAP_SUCCESS || res == LDAP_SASL_BIND_IN_PROGRESS) {

		/* Authentication was successful! */
		if (res == LDAP_SUCCESS) {
			log_message (sparams->utils, SASL_LOG_NOTE, "successful authentication");
			ret = calculate_user (ctx, sparams, oparams);

		/* We need to keep shuttling information */
		} else {
			ret = SASL_CONTINUE;
		}

		/* Copy the response from the server into SASL allocated memory */
		if (ret == SASL_OK || ret == SASL_CONTINUE) {

			if (scred)
				log_message (sparams->utils, SASL_LOG_DEBUG,
				             "%d bytes of server response", scred->bv_len);

			/* Send back the response to the client */
			if (scred && scred->bv_len) {
				buffer = (sparams->utils->malloc) (scred->bv_len);
				if (buffer) {
					memcpy (buffer, scred->bv_val, scred->bv_len);
					*serveroutlen = scred->bv_len;
					*serverout = buffer;
				} else {
					log_message (sparams->utils, SASL_LOG_ERR,
					             "couldn't allocate memory for server response");
					ret = SASL_NOMEM;
				}

			/* No response from the server */
			} else {
				*serverout = NULL;
				*serveroutlen = 0;

				/* We should always have a response when the dialog is going on */
				if (ret == SASL_CONTINUE) {
					log_message (sparams->utils, SASL_LOG_WARN,
					             "no response from server during sasl step");
				}
			}
		}

	/* Bad login */
	} else if (res == LDAP_INVALID_CREDENTIALS){
		log_message (sparams->utils, SASL_LOG_FAIL, "user login failed: invalid credentials");
		ret = SASL_FAIL;

	/* An error condition */
	} else {

		ret = report_ldap_error (sparams->utils, res, "couldn't do sasl bind step");
	}

	if (scred)
		ber_bvfree (scred);

	if (ret == SASL_OK) {
		oparams->doneflag = 1;
		oparams->mech_ssf = 0;
		oparams->maxoutbuf = 0;
		oparams->encode_context = NULL;
		oparams->encode = NULL;
		oparams->decode_context = NULL;
		oparams->decode = NULL;
		oparams->param_version = 0;
	}

	return ret;
}

static const char*
find_berval_value (const char *match, struct berval **values)
{
	struct berval **v;
	size_t len;

	if (!values)
		return NULL;

	len = strlen (match);
	for (v = values; *v; ++v) {
		if ((*v)->bv_len == len &&
		    strncasecmp (match, (*v)->bv_val, len) == 0) {
			return match;
		}
	}

	return NULL;
}

static int
delegateldap_avail (void *mech_context, sasl_server_params_t *sparams, void **context)
{
	delegate_context *ctx = NULL;
	LDAPMessage *message = NULL;
	int ret = SASL_NOMECH;

	char *attrs[] = { "supportedSASLMechanisms", NULL };
	const char *mechanism;
	LDAPMessage *entry;
	struct berval **values;
	int res, loaded;

	mechanism = (const char*)mech_context;
	*context = NULL;
	ret = SASL_NOMECH;
	loaded = 0;

	/* Lock */
	if (the_supported->mutex)
		(sparams->utils->mutex_lock) (the_supported->mutex);

		/* See if this mechanism is cached */
		loaded = the_supported->loaded;
		if (loaded && find_berval_value (mechanism, the_supported->mechs))
			ret = SASL_OK;

	/* Unlock the globals */
	if (the_supported->mutex)
		(sparams->utils->mutex_unlock) (the_supported->mutex);

	/* We have a cache, no need to go further */
	if (loaded)
		goto cleanup;

	log_message (sparams->utils, SASL_LOG_NOTE, "loading mechanism info from server");

	/* Create a new context, connect to the LDAP server */
	ret = delegateldap_new (mech_context, sparams, NULL, 0, context);
	if (ret != SASL_OK)
		goto cleanup;

	ctx = (delegate_context*)*context;
	values = NULL;

	/* Query the server for supported mechanisms */
	res = ldap_search_ext_s (ctx->ldap, "", LDAP_SCOPE_BASE, NULL, attrs, 0,
	                         NULL, NULL, LDAP_NO_LIMIT, LDAP_NO_LIMIT, &message);

	/* Couldn't find server info */
	if (res == LDAP_NO_SUCH_OBJECT) {
		log_message (sparams->utils, SASL_LOG_WARN, "no base object with LDAP server info");

	/* Some other failure */
	} else if (res != LDAP_SUCCESS) {
		ret = report_ldap_error (sparams->utils, res, "couldn't search server for supported SASL mechanisms");
		goto cleanup;

	/* Found something */
	} else {
		entry = ldap_first_entry (ctx->ldap, message);
		if (entry == NULL) {
			log_message (sparams->utils, SASL_LOG_WARN, "no base object with LDAP server info");
		} else {
			values = ldap_get_values_len (ctx->ldap, entry, "supportedSASLMechanisms");
			if (values == NULL)
				log_message (sparams->utils, SASL_LOG_WARN, "no supportedSASLMechanisms attribute on LDAP server info");
		}
	}

	/* Lock the globals */
	if (the_supported->mutex)
		(sparams->utils->mutex_lock) (the_supported->mutex);

		/* Swap in the mechanisms we just loaded */
		if (the_supported->mechs)
			ldap_value_free_len (the_supported->mechs);
		the_supported->mechs = values;
		the_supported->loaded = 1;

		/* And search through them */
		if (find_berval_value (mechanism, the_supported->mechs))
			ret = SASL_OK;

	/* Unlock the globals */
	if (the_supported->mutex)
		(sparams->utils->mutex_unlock) (the_supported->mutex);

cleanup:

	if (message)
		ldap_msgfree (message);
	if (ret == SASL_OK) {
		log_message (sparams->utils, SASL_LOG_DEBUG,
		             "server supports mechanism: %s", mechanism);
	} else {
		log_message (sparams->utils, SASL_LOG_FAIL,
		             "server doesn't support mechanism: %s", mechanism);
	}

	/*
	 * In theory you're supposed to be able to return the context
 	 * which then can be reused for efficiency, but in reality
	 * cyrus-sasl2 is too fragile and dumb for this, and does strange
	 * double frees and stuff.
	 */
	*context = NULL;
	if (ctx)
		delegateldap_dispose (ctx, sparams->utils);

	return ret;
}

static void
delegateldap_free (void *mech_context, const sasl_utils_t *utils)
{
	void *mutex;

	if (!the_supported)
		return;

	/* Lock globals */
	if (the_supported->mutex)
		(utils->mutex_lock) (the_supported->mutex);

		/* Free mechanisms */
		if (the_supported->mechs)
			ldap_value_free_len (the_supported->mechs);
		the_supported->mechs = NULL;
		the_supported->mechs = 0;

		/* And the main global context */
		mutex = the_supported->mutex;
		(utils->free) (the_supported);
		the_supported = NULL;

	/* Unlock globals */
	if (mutex)
		(utils->mutex_unlock) (mutex);
}

static sasl_server_plug_t delegateldap_server_plugins[] =
{
	{
		"DIGEST-MD5",                /* mech_name */
		0,                           /* max_ssf */
		SASL_SEC_NOPLAINTEXT
		| SASL_SEC_NOANONYMOUS
		| SASL_SEC_MUTUAL_AUTH,      /* security_flags */
		SASL_FEAT_ALLOWS_PROXY,      /* features */
		"DIGEST-MD5",                /* mech_context */
		&delegateldap_new,           /* mech_new */
		&delegateldap_step,          /* mech_step */
		&delegateldap_dispose,       /* mech_dispose */
		&delegateldap_free,          /* mech_free */
		NULL,                        /* setpass */
		NULL,                        /* user_query */
		NULL,                        /* idle */
		&delegateldap_avail,         /* mech avail */
		NULL                         /* spare */
	},
	{
		"CRAM-MD5",                  /* mech_name */
		0,                           /* max_ssf */
		SASL_SEC_NOPLAINTEXT
		| SASL_SEC_NOANONYMOUS,      /* security_flags */
		SASL_FEAT_SERVER_FIRST,      /* features */
		"CRAM-MD5",                  /* mech_context */
		&delegateldap_new,           /* mech_new */
		&delegateldap_step,          /* mech_step */
		&delegateldap_dispose,       /* mech_dispose */
		&delegateldap_free,          /* mech_free */
		NULL,                        /* setpass */
		NULL,                        /* user_query */
		NULL,                        /* idle */
		&delegateldap_avail,         /* mech avail */
		NULL                         /* spare */
	},
	{
		"PLAIN",                     /* mech_name */
		0,                           /* max_ssf */
		SASL_SEC_NOANONYMOUS,        /* security_flags */
		SASL_FEAT_WANT_CLIENT_FIRST
		| SASL_FEAT_ALLOWS_PROXY,    /* features */
		"PLAIN",                     /* mech_context */
		&delegateldap_new,           /* mech_new */
		&delegateldap_step,          /* mech_step */
		&delegateldap_dispose,       /* mech_dispose */
		&delegateldap_free,          /* mech_free */
		NULL,                        /* setpass */
		NULL,                        /* user_query */
		NULL,                        /* idle */
		&delegateldap_avail,         /* mech avail */
		NULL                         /* spare */
	},
	{
		"LOGIN",                     /* mech_name */
		0,                           /* max_ssf */
		SASL_SEC_NOANONYMOUS,        /* security_flags */
		0,                           /* features */
		"LOGIN",                     /* mech_context */
		&delegateldap_new,           /* mech_new */
		&delegateldap_step,          /* mech_step */
		&delegateldap_dispose,       /* mech_dispose */
		&delegateldap_free,          /* mech_free */
		NULL,                        /* setpass */
		NULL,                        /* user_query */
		NULL,                        /* idle */
		&delegateldap_avail,         /* mech avail */
		NULL                         /* spare */
	}
};

extern int
sasl_server_plug_init (const sasl_utils_t *utils, int maxversion, int *out_version,
                       sasl_server_plug_t **pluglist, int *plugcount)
{
	const char *option;

	if (maxversion < SASL_SERVER_PLUG_VERSION) {
		log_message (utils, SASL_LOG_ERR, "bad version: can't load delegateldap plugin");
		return SASL_BADVERS;
	}

	log_message (utils, SASL_LOG_DEBUG, "loading delegateldap plugin");

	if ((utils->getopt) (utils->getopt_context, NULL,
			     OPTION_SERVER, &option, NULL) != SASL_OK || !option) {
		log_message (utils, SASL_LOG_ERR,
		             "missing '%s' option in config file", OPTION_SERVER);
		return SASL_BADPARAM;
	}

	/* From ldapdb plugin */
	if ((utils->getopt) (utils->getopt_context, NULL,
	                     OPTION_LDAPRC, &option, NULL) == SASL_OK && option) {
		setenv ("LDAPRC", option, 1);
	}

	the_supported = (utils->malloc) (sizeof (supported_mechanisms));
	if (!the_supported)
		return SASL_NOMEM;
	memset (the_supported, 0, sizeof (supported_mechanisms));

	if (utils->mutex_alloc)
		the_supported->mutex = (utils->mutex_alloc) ();

	*out_version = SASL_SERVER_PLUG_VERSION;
	*pluglist = delegateldap_server_plugins;
	*plugcount = sizeof (delegateldap_server_plugins) / sizeof (delegateldap_server_plugins[0]);

	return SASL_OK;
}