/*
 * The public APIs of the password update kadmind plugin.
 *
 * Provides the public pwupdate_init, pwupdate_close,
 * pwupdate_precommit_password, and pwupdate_postcommit_password APIs for the
 * kadmind plugin.  These APIs can also be called by command-line utilities.
 *
 * Active Directory synchronization is done in precommit and AFS kaserver
 * synchronization is done in postcommit.  The implication is that if Active
 * Directory synchronization fails, the update fails, but if AFS kaserver
 * synchronization fails, everything else still succeeds.
 *
 * Written by Russ Allbery <eagle@eyrie.org>
 * Based on code developed by Derrick Brashear and Ken Hornstein of Sine
 *     Nomine Associates, on behalf of Stanford University.
 * Copyright 2006, 2007, 2010, 2013
 *     The Board of Trustees of the Leland Stanford Junior University
 *
 * See LICENSE for licensing terms.
 */

#include <config.h>
#include <portable/krb5.h>
#include <portable/system.h>

#include <errno.h>

#include <plugin/internal.h>
#include <util/macros.h>


/*
 * Initialize the module.  This consists solely of loading our configuration
 * options from krb5.conf into a newly allocated struct stored in the second
 * argument to this function.  Returns 0 on success, non-zero on failure.
 * This function returns failure only if it could not allocate memory.
 */
krb5_error_code
sync_init(krb5_context ctx, kadm5_hook_modinfo **result)
{
    kadm5_hook_modinfo *config;

    /* Allocate our internal data. */
    config = calloc(1, sizeof(*config));
    if (config == NULL)
        return sync_error_system(ctx, "cannot allocate memory");

    /* Get Active Directory connection information from krb5.conf. */
    sync_config_string(ctx, "ad_keytab", &config->ad_keytab);
    sync_config_string(ctx, "ad_principal", &config->ad_principal);
    sync_config_string(ctx, "ad_realm", &config->ad_realm);
    sync_config_string(ctx, "ad_admin_server", &config->ad_admin_server);
    sync_config_string(ctx, "ad_ldap_base", &config->ad_ldap_base);

    /* Get allowed instances from krb5.conf. */
    sync_config_list(ctx, "ad_instances", &config->ad_instances);

    /*
     * See if we're propagating an instance to the base account in AD.  This
     * option is not supported on MIT Kerberos and results in an error there,
     * since calling libkadm5srv functions from inside a plugin appears to
     * result in corruption with MIT Kerberos (at least in 1.10.1).
     */
    sync_config_string(ctx, "ad_base_instance", &config->ad_base_instance);
#if HAVE_KRB5_MIT
    if (config->ad_base_instance != NULL) {
        sync_close(ctx, config);
        return sync_error_config(ctx, "ad_base_instance not supported on MIT"
                                 " Kerberos");
    }
#endif

    /* See if we're forcing queuing of all changes. */
    sync_config_boolean(ctx, "ad_queue_only", &config->ad_queue_only);

    /* Get the directory for queued changes from krb5.conf. */
    sync_config_string(ctx, "queue_dir", &config->queue_dir);

    /* Whether to log informational and warning messages to syslog. */
    config->syslog = true;
    sync_config_boolean(ctx, "syslog", &config->syslog);

    /* Initialized.  Set data and return. */
    *result = config;
    return 0;
}


/*
 * Shut down the module.  This just means freeing our configuration struct,
 * since we don't store any other local state.
 */
void
sync_close(krb5_context ctx UNUSED, kadm5_hook_modinfo *config)
{
    free(config->ad_admin_server);
    free(config->ad_base_instance);
    sync_vector_free(config->ad_instances);
    free(config->ad_keytab);
    free(config->ad_ldap_base);
    free(config->ad_principal);
    free(config->ad_realm);
    free(config->queue_dir);
    free(config);
}


/*
 * Given the configuration and the instance of a principal, returns true if
 * that instance is allowed and false otherwise.
 */
static bool
instance_allowed(kadm5_hook_modinfo *config, const char *instance)
{
    size_t i;

    if (instance == NULL)
        return false;
    if (config->ad_base_instance)
        if (strcmp(config->ad_base_instance, instance) == 0)
            return true;
    if (config->ad_instances == NULL)
        return false;
    for (i = 0; i < config->ad_instances->count; i++)
        if (strcmp(config->ad_instances->strings[i], instance) == 0)
            return true;
    return false;
}


/*
 * Check the principal for which we're changing a password or the enable
 * status.  Takes a flag, which is true for a password change and false for
 * other types of changes, since password changes use ad_base_instance.
 *
 * If it contains a non-null instance, we don't want to propagate the change;
 * we only want to change passwords for regular users.
 *
 * If it is a single-part principal name, ad_base_instance is set, and the
 * equivalent principal with that instance also exists, we don't propagate
 * this change because the instance's password is propagated as the base
 * account in Active Directory instead.
 *
 * Sets the allowed flag based on whether we should proceed, and returns a
 * Kerberos status code for more serious errors.  If we shouldn't proceed,
 * logs a debug-level message to syslog.
 */
static krb5_error_code
principal_allowed(kadm5_hook_modinfo *config, krb5_context ctx,
                  krb5_principal principal, bool pwchange, bool *allowed)
{
    char *display;
    krb5_error_code code;
    int ncomp;
    bool exists = false;

    /* Default to propagating. */
    *allowed = true;

    /* Get the number of components. */
    ncomp = krb5_principal_get_num_comp(ctx, principal);

    /*
     * If the principal is single-part, check against ad_base_instance.
     * Otherwise, if the principal is multi-part, check the instance.
     */
    if (pwchange && ncomp == 1 && config->ad_base_instance != NULL) {
        code = sync_instance_exists(ctx, principal, config->ad_base_instance,
                                    &exists);
        if (code != 0)
            return code;
        if (exists) {
            code = krb5_unparse_name(ctx, principal, &display);
            if (code != 0)
                return code;
            sync_syslog_debug(config, "krb5-sync: ignoring principal \"%s\""
                              " because %s instance exists", display,
                              config->ad_base_instance);
            krb5_free_unparsed_name(ctx, display);
            *allowed = false;
        }
    } else if (ncomp > 1) {
        const char *instance;

        instance = krb5_principal_get_comp_string(ctx, principal, 1);
        if (!instance_allowed(config, instance)) {
            code = krb5_unparse_name(ctx, principal, &display);
            if (code != 0)
                return code;
            sync_syslog_debug(config, "krb5-sync: ignoring principal \"%s\""
                              " with non-null instance", display);
            krb5_free_unparsed_name(ctx, display);
            *allowed = false;
        }
    }
    return 0;
}


/*
 * Actions to take before the password is changed in the local database.
 *
 * Push the new password to Active Directory if we have the necessary
 * configuration information and return any error it returns, but skip any
 * principals with a non-NULL instance since those are kept separately in each
 * realm.
 *
 * If a password change is already queued for this usequeue this password
 * change as well.  If the password change fails for a reason that may mean
 * that the user doesn't already exist, also queue this change.
 *
 * If the new password is NULL, that means that the keys are being randomized.
 * Currently, we can't do anything in that case, so just skip it.
 */
krb5_error_code
sync_chpass(kadm5_hook_modinfo *config, krb5_context ctx,
            krb5_principal principal, const char *password)
{
    krb5_error_code code;
    const char *message;
    bool allowed = false;
    bool conflict = true;

    /* Do nothing if we don't have required configuration. */
    if (config->ad_realm == NULL)
        return 0;

    /* If there was no password, this is probably a key randomization. */
    if (password == NULL)
        return 0;

    /* Check if this principal should be synchronized. */
    code = principal_allowed(config, ctx, principal, true, &allowed);
    if (code != 0)
        return code;
    if (!allowed)
        return 0;

    /* Check if there was a queue conflict or if we always queue. */
    code = sync_queue_conflict(config, ctx, principal, "password", &conflict);
    if (code != 0)
        return code;
    if (conflict)
        goto queue;
    if (config->ad_queue_only)
        goto queue;

    /* Do the password change, and queue if it fails. */
    code = sync_ad_chpass(config, ctx, principal, password);
    if (code != 0) {
        message = krb5_get_error_message(ctx, code);
        sync_syslog_notice(config, "krb5-sync: AD password change failed,"
                           " queuing: %s", message);
        krb5_free_error_message(ctx, message);
        goto queue;
    }
    return 0;

queue:
    return sync_queue_write(config, ctx, principal, "password", password);
}


/*
 * Actions to take after the account status is changed in the local database.
 *
 * Push the new account status to Active Directory if so configured, but skip
 * principals with non-NULL instances.  Return any error that it returns.
 *
 * If a status change is already queued, or if making the status change fails,
 * queue it for later processing.
 */
krb5_error_code
sync_status(kadm5_hook_modinfo *config, krb5_context ctx,
            krb5_principal principal, bool enabled)
{
    krb5_error_code code;
    const char *message;
    bool allowed = false;
    bool conflict = true;

    /* Do nothing if we don't have the required configuration. */
    if (config->ad_admin_server == NULL
        || config->ad_keytab == NULL
        || config->ad_ldap_base == NULL
        || config->ad_principal == NULL
        || config->ad_realm == NULL)
        return 0;

    /* Check if this principal should be synchronized. */
    code = principal_allowed(config, ctx, principal, false, &allowed);
    if (code != 0)
        return code;
    if (!allowed)
        return 0;

    /* Check if there was a queue conflict or if we always queue. */
    code = sync_queue_conflict(config, ctx, principal, "enable", &conflict);
    if (code != 0)
        return code;
    if (conflict)
        goto queue;
    if (config->ad_queue_only)
        goto queue;

    /* Synchronize the status. */
    code = sync_ad_status(config, ctx, principal, enabled);
    if (code != 0) {
        message = krb5_get_error_message(ctx, code);
        sync_syslog_notice(config, "krb5-sync: AD status change failed,"
                           " queuing: %s", message);
        krb5_free_error_message(ctx, message);
        goto queue;
    }
    return 0;

queue:
    return sync_queue_write(config, ctx, principal,
                            enabled ? "enable" : "disable", NULL);
}