#include <stdio.h>
#include <string.h>
#include <syslog.h>

#include <slapi-plugin.h>

/* This is missing in slapi-plugin.h: */
extern int slapi_pw_find(struct berval **vals, struct berval *v);

static Slapi_ComponentId *plugin_id = NULL;

/* Get an entry specified by a DN and with the specified attributes. */
static int get_entry(const char *dn, char **attrs, Slapi_Entry **entry)
{
    Slapi_Entry **entries = NULL;
    Slapi_PBlock *pb = NULL;
    int rc = 0;

    if (entry) {
        *entry = NULL;
    }

    pb = slapi_pblock_new();
    slapi_search_internal_set_pb(
        pb,
        dn,
        LDAP_SCOPE_BASE,
        "(objectclass=*)",
        attrs,
        0 /* attrsonly */,
        NULL /* controls */,
        NULL /* uniqueid */,
        plugin_id,
        0 /* actions */);

    slapi_search_internal_pb(pb);
    slapi_pblock_get(pb, SLAPI_PLUGIN_INTOP_RESULT, &rc);

    if (LDAP_SUCCESS == rc) {
        slapi_pblock_get(pb, SLAPI_PLUGIN_INTOP_SEARCH_ENTRIES, &entries);

        if (NULL != entries && NULL != entries[0]) {
            if (entry) {
                Slapi_Entry *tmp = NULL;
                tmp = entries[0];
                *entry = slapi_entry_dup(tmp);
            }
        } else {
            /* No entry there */
            rc = LDAP_NO_SUCH_OBJECT;
        }
    }


    slapi_free_search_results_internal(pb);
    slapi_pblock_destroy(pb);
    pb = NULL;

    return rc;
}

/* Check if the parent entry contains a uid attribute. */
static int dn_contains_uid(const char *dn)
{
    char *attrs[] = { "uid", NULL };
    Slapi_Entry *entry = NULL;
    Slapi_Attr *attr = NULL;
    Slapi_ValueSet *uid_values = NULL;

    int rc = 0;

    rc |= get_entry(dn, attrs, &entry);
    if (rc != 0 || entry == NULL) {
        /* parent_dn not found */
        rc = 1;
        goto fail1;
    }

    rc |= slapi_entry_attr_find(entry, "uid", &attr);
    if (rc != 0 || attr == NULL) {
        /* no uid attribute */
        rc = 1;
        goto fail1;
    }

    rc |= slapi_attr_get_valueset(attr, &uid_values);
    if (rc != 0 || slapi_valueset_count(uid_values) == 0) {
        /* empty uid value */
        rc = 1;
        goto fail1;
    }

fail1:
    slapi_entry_free(entry);

    return rc;
}

static int auth(char *dn, struct berval *credentials)
{
    char *attrs[] = { "userPassword", NULL };
    Slapi_Entry *entry = NULL;
    Slapi_Attr *attr = NULL;
    struct berval **userPasswords = NULL;

    int rc = 0;

    /* get entry */
    rc |= get_entry(dn, attrs, &entry);
    if (rc != 0 || entry == NULL) {
        rc = -1;
        goto fail1;
    }

    /* get userpassword attr */
    rc |= slapi_entry_attr_find(entry, "userPassword", &attr);
    if (rc != 0 || attr == NULL) {
        rc = 1;
        goto fail1;
    }

    /* get attribute values */
    rc |= slapi_attr_get_values(attr, &userPasswords);
    if (rc != 0 || userPasswords == NULL) {
        rc = 1;
        goto fail1;
    }

    /* check password */
    rc |= slapi_pw_find(userPasswords, credentials);

fail1:
    slapi_entry_free(entry);
    return rc;
}

static int auth_with_password_fallback(char *dn, struct berval *credentials)
{
    char *parent_dn;

    int rc = 0;
    char fn[] = "auth_with_password_fallback in service_passwords plug-in";

    slapi_log_error(
        SLAPI_LOG_PLUGIN, fn,
        "Try password fallback with dn: %s.\n", dn);

    rc = auth(dn, credentials);
    if (rc == 0) {
        /* auth success */
        return 0;
    }
    else if (rc == 1) {
        /* auth fail, but entry exists (no fallback) */
        return 1;
    }

    /* fallback to parent dn */
    parent_dn = slapi_dn_parent(dn);
    rc = auth(parent_dn, credentials);
    if (rc == 0) {
        /* auth success */
        return 0;
    }

    return 1;
}

static int pre_bind(Slapi_PBlock *pb)
{
    char *dn;
    int method;
    struct berval *credentials;
    int is_replication;
    int is_internal;
    int connId;
    int opId;
    long msgId;

    char *parent_dn;

    int rc = 0;
    char fn[] = "pre_bind in service_passwords plug-in";

    /* Obtain the bind information from the parameter block. */
    rc |= slapi_pblock_get(pb, SLAPI_BIND_TARGET,             &dn);
    rc |= slapi_pblock_get(pb, SLAPI_BIND_METHOD,             &method);
    rc |= slapi_pblock_get(pb, SLAPI_BIND_CREDENTIALS,        &credentials);
    rc |= slapi_pblock_get(pb, SLAPI_OPERATION_MSGID,         &msgId);
    rc |= slapi_pblock_get(pb, SLAPI_CONN_ID,                 &connId);
    rc |= slapi_pblock_get(pb, SLAPI_OPERATION_ID,            &opId);
    rc |= slapi_pblock_get(pb, SLAPI_IS_REPLICATED_OPERATION, &is_replication);
    rc |= slapi_pblock_get(pb, SLAPI_IS_INTERNAL_OPERATION,   &is_internal);

    if (rc != 0) {
        slapi_log_error(
            SLAPI_LOG_PLUGIN, fn,
            "Could not get parameters for bind operation (error %d).\n",
            rc);

        /* Cancel bind */
        slapi_send_ldap_result(
            pb, LDAP_OPERATIONS_ERROR, NULL, NULL, 0, NULL);
        return LDAP_OPERATIONS_ERROR;
    }

    if (is_replication || is_internal) {
        return 0;
    }

    if (method != LDAP_AUTH_SIMPLE) {
        slapi_log_error(
            SLAPI_LOG_PLUGIN, fn,
            "The service_passwords plug-in does not handle this bind "
                "(method %d).\n",
            method);

        return 0;
    }

    parent_dn = slapi_dn_parent(dn);
    if (dn_contains_uid(parent_dn) != 0) {
        /* parent_dn is not an user, so we ignore this bind request. */
        return 0;
    }

    if (auth_with_password_fallback(dn, credentials) == 0) {
        /* auth success: set connection info */
        rc |= slapi_pblock_set(pb, SLAPI_CONN_DN, slapi_ch_strdup(dn));

        if (rc != 0) {
            slapi_log_error(
                SLAPI_LOG_PLUGIN, fn,
                "Failed to set connection info.\n");

            rc = LDAP_OPERATIONS_ERROR;
            slapi_send_ldap_result(pb, rc, NULL, NULL, 0, NULL);
            return rc;
        }

        /* auth done */
        slapi_send_ldap_result(pb, LDAP_SUCCESS, NULL, NULL, 0, NULL);
        return 1;
    }

    /* auth fail */
    rc = LDAP_INVALID_CREDENTIALS;
    slapi_send_ldap_result(pb, rc, NULL, NULL, 0, NULL);
    return rc;
}

Slapi_PluginDesc bindpdesc = {
    .spd_id = "service_passwords",
    .spd_vendor = "spline",
    .spd_version = "1.0",
    .spd_description = "preoperation plugin "
        "to authenticate a bind against different passwords"
};

int service_passwords_init(Slapi_PBlock *pb)
{
    int rc = 0;

    rc |= slapi_pblock_set(pb, SLAPI_PLUGIN_VERSION, SLAPI_PLUGIN_CURRENT_VERSION);
    rc |= slapi_pblock_set(pb, SLAPI_PLUGIN_DESCRIPTION, (void *) &bindpdesc);
    rc |= slapi_pblock_set(pb, SLAPI_PLUGIN_PRE_BIND_FN, (void *) pre_bind);
    rc |= slapi_pblock_get(pb, SLAPI_PLUGIN_IDENTITY, &plugin_id);
    return rc;
}