/*
	 * Original copyright 2004 International Business Machines
	 * Later changes copyright 2008-2026 the Pacemaker project contributors
	 *
	 * The version control history for this file may have further details.
	 *
	 * This source code is licensed under the GNU Lesser General Public License
	 * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
	 */
	
	#include <crm_internal.h>
	#include <unistd.h>
	#include <limits.h>
	#include <stdbool.h>
	#include <stdlib.h>
	#include <stdint.h>
	#include <stdio.h>
	#include <stdarg.h>
	#include <string.h>
	#include <pwd.h>
	
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <glib.h>
	
	#include <crm/crm.h>
	#include <crm/cib/internal.h>
	#include <crm/common/ipc.h>
	#include <crm/common/xml.h>
	
	#define CIB_SERIES "cib"
	#define CIB_SERIES_MAX 100
	#define CIB_LIVE_NAME CIB_SERIES ".xml"
	
	// key: client ID (const char *) -> value: client (cib_t *)
	static GHashTable *client_table = NULL;
	
	enum file_flags {
	    file_flag_dirty = (UINT32_C(1) << 0),
	    file_flag_live  = (UINT32_C(1) << 1),
	};
	
	typedef struct {
	    char *id;
	    char *filename;
	    uint32_t flags; // Group of enum file_flags
	    xmlNode *cib_xml;
	} file_opaque_t;
	
	/* backup_cib_file() and cib_file_write_with_digest() need to chown the
	 * written files only in limited circumstances, so these variables allow
	 * that to be indicated without affecting external callers
	 */
	static uid_t file_owner = 0;
	static uid_t file_group = 0;
	static bool do_chown = false;
	
	static cib__op_fn_t get_op_function(const cib__operation_t *operation);
	
	#define set_file_flags(cibfile, flags_to_set) do {                      \
	        (cibfile)->flags = pcmk__set_flags_as(__func__, __LINE__,       \
	                                              LOG_TRACE, "CIB file",    \
	                                              cibfile->filename,        \
	                                              (cibfile)->flags,         \
	                                              (flags_to_set),           \
	                                              #flags_to_set);           \
	    } while (0)
	
	#define clear_file_flags(cibfile, flags_to_clear) do {                  \
	        (cibfile)->flags = pcmk__clear_flags_as(__func__, __LINE__,     \
	                                                LOG_TRACE, "CIB file",  \
	                                                cibfile->filename,      \
	                                                (cibfile)->flags,       \
	                                                (flags_to_clear),       \
	                                                #flags_to_clear);       \
	    } while (0)
	
	/*!
	 * \internal
	 * \brief Add a CIB file client to client table
	 *
	 * \param[in] cib  CIB client
	 */
	static void
	register_client(const cib_t *cib)
	{
	    file_opaque_t *private = cib->variant_opaque;
	
	    if (client_table == NULL) {
	        client_table = pcmk__strkey_table(NULL, NULL);
	    }
	    g_hash_table_insert(client_table, private->id, (void *) cib);
	}
	
	/*!
	 * \internal
	 * \brief Remove a CIB file client from client table
	 *
	 * \param[in] cib  CIB client
	 */
	static void
	unregister_client(const cib_t *cib)
	{
	    file_opaque_t *private = cib->variant_opaque;
	
	    if (client_table == NULL) {
	        return;
	    }
	
	    g_hash_table_remove(client_table, private->id);
	
	    /* @COMPAT: Add to crm_exit() when libcib and libcrmcommon are merged,
	     * instead of destroying the client table when there are no more clients.
	     */
	    if (g_hash_table_size(client_table) == 0) {
	        g_clear_pointer(&client_table, g_hash_table_destroy);
	    }
	}
	
	/*!
	 * \internal
	 * \brief Look up a CIB file client by its ID
	 *
	 * \param[in] client_id  CIB client ID
	 *
	 * \return CIB client with matching ID if found, or \p NULL otherwise
	 */
	static cib_t *
	get_client(const char *client_id)
	{
	    if (client_table == NULL) {
	        return NULL;
	    }
	    return g_hash_table_lookup(client_table, (void *) client_id);
	}
	
	static int
	process_request(cib_t *cib, xmlNode *request, xmlNode **output)
	{
	    int rc = pcmk_rc_ok;
	    const cib__operation_t *operation = NULL;
	    cib__op_fn_t op_function = NULL;
	
	    uint32_t call_options = cib_none;
	    const char *op = pcmk__xe_get(request, PCMK__XA_CIB_OP);
	
	    bool changed = false;
	    bool read_only = false;
	    xmlNode *result_cib = NULL;
	    xmlNode *cib_diff = NULL;
	    xmlNode *local_output = NULL;
	
	    file_opaque_t *private = cib->variant_opaque;
	
	    if (output != NULL) {
	        *output = NULL;
	    }
	
	    // We error checked these in callers, but make Coverity happy
	    pcmk__assert(cib__get_operation(op, &operation) == pcmk_rc_ok);
	    op_function = get_op_function(operation);
	
	    rc = pcmk__xe_get_flags(request, PCMK__XA_CIB_CALLOPT, &call_options,
	                            cib_none);
	    if (rc != pcmk_rc_ok) {
	        pcmk__warn("Couldn't parse options from request: %s", pcmk_rc_str(rc));
	    }
	
	    read_only = !pcmk__is_set(operation->flags, cib__op_attr_modifies);
	
	    if (read_only) {
	        rc = cib__perform_op_ro(op_function, request, &private->cib_xml,
	                                &local_output);
	    } else {
	        result_cib = private->cib_xml;
	        rc = cib__perform_op_rw(cib_file, op_function, request, &changed,
	                                &result_cib, &cib_diff, &local_output);
	    }
	
	    if (pcmk__is_set(call_options, cib_transaction)) {
	        /* The rest of the logic applies only to the transaction as a whole, not
	         * to individual requests.
	         */
	        goto done;
	    }
	
	    if (rc == pcmk_rc_schema_validation) {
	        // Show validation errors to stderr
	        pcmk__validate_xml(result_cib, NULL, NULL);
	
	    } else if ((rc == pcmk_rc_ok) && !read_only) {
	        if (result_cib != private->cib_xml) {
	            pcmk__xml_free(private->cib_xml);
	            private->cib_xml = result_cib;
	        }
	        set_file_flags(private, file_flag_dirty);
	    }
	
	    if (local_output == NULL) {
	        goto done;
	    }
	
	    if ((output != NULL) && (local_output->doc != private->cib_xml->doc)) {
	        *output = local_output;
	        goto done;
	    }
	
	    if (output != NULL) {
	        *output = pcmk__xml_copy(NULL, local_output);
	        goto done;
	    }
	
	    if (local_output->doc != private->cib_xml->doc) {
	        pcmk__xml_free(local_output);
	    }
	
	done:
	    if (result_cib != private->cib_xml) {
	        pcmk__xml_free(result_cib);
	    }
	    pcmk__xml_free(cib_diff);
	    return rc;
	}
	
	/*!
	 * \internal
	 * \brief Process requests in a CIB transaction
	 *
	 * Stop when a request fails or when all requests have been processed.
	 *
	 * \param[in,out] cib          CIB client
	 * \param[in,out] transaction  CIB transaction
	 *
	 * \return Standard Pacemaker return code
	 */
	static int
	process_transaction_requests(cib_t *cib, xmlNode *transaction)
	{
	    file_opaque_t *private = cib->variant_opaque;
	
	    for (xmlNode *request = pcmk__xe_first_child(transaction,
	                                                 PCMK__XE_CIB_COMMAND, NULL,
	                                                 NULL);
	         request != NULL;
	         request = pcmk__xe_next(request, PCMK__XE_CIB_COMMAND)) {
	
	        xmlNode *output = NULL;
	        const char *op = pcmk__xe_get(request, PCMK__XA_CIB_OP);
	
	        int rc = process_request(cib, request, &output);
	
	        pcmk__xml_free(output);
	
	        if (rc != pcmk_rc_ok) {
	            pcmk__err("Aborting transaction for CIB file client (%s) on file "
	                      "'%s' due to failed %s request: %s",
	                      private->id, private->filename, op, pcmk_rc_str(rc));
	            pcmk__log_xml_info(request, "Failed request");
	            return rc;
	        }
	
	        pcmk__trace("Applied %s request to transaction working CIB for CIB "
	                    "file client (%s) on file '%s'",
	                    op, private->id, private->filename);
	        pcmk__log_xml_trace(request, "Successful request");
	    }
	
	    return pcmk_rc_ok;
	}
	
	/*!
	 * \internal
	 * \brief Commit a given CIB file client's transaction to a working CIB copy
	 *
	 * \param[in,out] cib          CIB file client
	 * \param[in]     transaction  CIB transaction
	 * \param[in,out] result_cib   Where to store result CIB
	 *
	 * \return Standard Pacemaker return code
	 *
	 * \note The caller is responsible for replacing the \p cib argument's
	 *       \p private->cib_xml with \p result_cib on success, and for freeing
	 *       \p result_cib using \p pcmk__xml_free() on failure.
	 */
	static int
	commit_transaction(cib_t *cib, xmlNode *transaction, xmlNode **result_cib)
	{
	    int rc = pcmk_rc_ok;
	    file_opaque_t *private = cib->variant_opaque;
	    xmlNode *saved_cib = private->cib_xml;
	
	    /* *result_cib should be a copy of private->cib_xml (created by
	     * cib__perform_op_rw())
	     */
	    pcmk__assert((result_cib != NULL) && (*result_cib != NULL)
	                 && (*result_cib != private->cib_xml));
	
	    CRM_CHECK(pcmk__xe_is(transaction, PCMK__XE_CIB_TRANSACTION),
	              return pcmk_rc_no_transaction);
	
	    pcmk__trace("Committing transaction for CIB file client (%s) on file '%s' "
	                "to working CIB",
	                private->id, private->filename);
	
	    // Apply all changes to a working copy of the CIB
	    private->cib_xml = *result_cib;
	
	    rc = process_transaction_requests(cib, transaction);
	
	    pcmk__trace("Transaction commit %s for CIB file client (%s) on file '%s'",
	                ((rc == pcmk_rc_ok)? "succeeded" : "failed"),
	                private->id, private->filename);
	
	    /* Some request types (for example, erase) may have freed private->cib_xml
	     * (the working copy) and pointed it at a new XML object. In that case, it
	     * follows that *result_cib (the working copy) was freed.
	     *
	     * Point *result_cib at the updated working copy stored in private->cib_xml.
	     */
	    *result_cib = private->cib_xml;
	
	    // Point private->cib_xml back to the unchanged original copy
	    private->cib_xml = saved_cib;
	
	    return rc;
	}
	
	static int
	process_commit_transact(xmlNode *req, xmlNode **cib_xml, xmlNode **answer)
	{
	    int rc = pcmk_rc_ok;
	    xmlNode *input = cib__get_calldata(req);
	    const char *client_id = pcmk__xe_get(req, PCMK__XA_CIB_CLIENTID);
	    cib_t *cib = NULL;
	
	    CRM_CHECK(client_id != NULL, return -EINVAL);
	
	    cib = get_client(client_id);
	    CRM_CHECK(cib != NULL, return -EINVAL);
	
	    rc = commit_transaction(cib, input, cib_xml);
	    if (rc != pcmk_rc_ok) {
	        file_opaque_t *private = cib->variant_opaque;
	
	        pcmk__err("Could not commit transaction for CIB file client (%s) on "
	                  "file '%s': %s",
	                  private->id, private->filename, pcmk_rc_str(rc));
	    }
	    return pcmk_rc2legacy(rc);
	}
	
	static const cib__op_fn_t op_functions[] = {
	    [cib__op_apply_patch]      = cib__process_apply_patch,
	    [cib__op_bump]             = cib__process_bump,
	    [cib__op_commit_transact]  = process_commit_transact,
	    [cib__op_create]           = cib__process_create,
	    [cib__op_delete]           = cib__process_delete,
	    [cib__op_erase]            = cib__process_erase,
	    [cib__op_modify]           = cib__process_modify,
	    [cib__op_query]            = cib__process_query,
	    [cib__op_replace]          = cib__process_replace,
	    [cib__op_upgrade]          = cib__process_upgrade,
	};
	
	/*!
	 * \internal
	 * \brief Get the function that performs a given CIB file operation
	 *
	 * \param[in] operation  Operation whose function to look up
	 *
	 * \return Function that performs \p operation for a CIB file client
	 */
	static cib__op_fn_t
	get_op_function(const cib__operation_t *operation)
	{
	    enum cib__op_type type = operation->type;
	
	    pcmk__assert(type >= 0);
	
	    if (type >= PCMK__NELEM(op_functions)) {
	        return NULL;
	    }
	    return op_functions[type];
	}
	
	/*!
	 * \internal
	 * \brief Check whether a file is the live CIB
	 *
	 * \param[in] filename Name of file to check
	 *
	 * \return \c true if file exists and its real path is same as the live CIB's,
	 *         or \c false otherwise
	 */
	static bool
	is_live(const char *filename)
	{
	    bool same = false;
	
	    if (filename != NULL) {
	        // Canonicalize file names for true comparison
	        char *real_filename = NULL;
	
	        if (pcmk__real_path(filename, &real_filename) == pcmk_rc_ok) {
	            char *real_livename = NULL;
	
	            if (pcmk__real_path(CRM_CONFIG_DIR "/" CIB_LIVE_NAME,
	                                &real_livename) == pcmk_rc_ok) {
	                same = !strcmp(real_filename, real_livename);
	                free(real_livename);
	            }
	            free(real_filename);
	        }
	    }
	    return same;
	}
	
	static int
	file_perform_op_delegate(cib_t *cib, const char *op, const char *host,
	                         const char *section, xmlNode *data,
	                         xmlNode **output_data, int call_options,
	                         const char *user_name)
	{
	    int rc = pcmk_ok;
	    xmlNode *request = NULL;
	    file_opaque_t *private = cib->variant_opaque;
	
	    const cib__operation_t *operation = NULL;
	
	    pcmk__info("Handling %s operation for %s as %s", pcmk__s(op, "invalid"),
	               pcmk__s(section, "entire CIB"),
	               pcmk__s(user_name, "default user"));
	
	    if (cib->state == cib_disconnected) {
	        rc = ENOTCONN;
	        goto done;
	    }
	
	    rc = cib__get_operation(op, &operation);
	    if (rc != pcmk_rc_ok) {
	        // @COMPAT: At compatibility break, use rc directly
	        rc = EPROTONOSUPPORT;
	        goto done;
	    }
	
	    if (get_op_function(operation) == NULL) {
	        // @COMPAT: At compatibility break, use EOPNOTSUPP
	        pcmk__err("Operation %s is not supported by CIB file clients", op);
	        rc = EPROTONOSUPPORT;
	        goto done;
	    }
	
	    cib__set_call_options(call_options, "file operation", cib_no_mtime);
	
	    rc = cib__create_op(cib, op, host, section, data, call_options, user_name,
	                        NULL, &request);
	    if (rc != pcmk_rc_ok) {
	        goto done;
	    }
	
	    pcmk__xe_set(request, PCMK__XA_ACL_TARGET, user_name);
	    pcmk__xe_set(request, PCMK__XA_CIB_CLIENTID, private->id);
	
	    if (pcmk__is_set(call_options, cib_transaction)) {
	        rc = cib__extend_transaction(cib, request);
	        goto done;
	    }
	
	    rc = process_request(cib, request, output_data);
	
	done:
	    pcmk__xml_free(request);
	    return pcmk_rc2legacy(rc);
	}
	
	/*!
	 * \internal
	 * \brief Read CIB from disk and validate it against XML schema
	 *
	 * \param[in]   filename  Name of file to read CIB from
	 * \param[out]  output    Where to store the read CIB XML
	 *
	 * \return pcmk_ok on success,
	 *         -ENXIO if file does not exist (or stat() otherwise fails), or
	 *         -pcmk_err_schema_validation if XML doesn't parse or validate
	 * \note If filename is the live CIB, this will *not* verify its digest,
	 *       though that functionality would be trivial to add here.
	 *       Also, this will *not* verify that the file is writable,
	 *       because some callers might not need to write.
	 */
	static int
	load_file_cib(const char *filename, xmlNode **output)
	{
	    struct stat buf;
	    xmlNode *root = NULL;
	
	    /* Ensure file is readable */
	    if (strcmp(filename, "-") && (stat(filename, &buf) < 0)) {
	        return -ENXIO;
	    }
	
	    /* Parse XML from file */
	    root = pcmk__xml_read(filename);
	    if (root == NULL) {
	        return -pcmk_err_schema_validation;
	    }
	
	    /* Add a status section if not already present */
	    if (pcmk__xe_first_child(root, PCMK_XE_STATUS, NULL, NULL) == NULL) {
	        pcmk__xe_create(root, PCMK_XE_STATUS);
	    }
	
	    /* Validate XML against its specified schema */
	    if (!pcmk__configured_schema_validates(root)) {
	        pcmk__xml_free(root);
	        return -pcmk_err_schema_validation;
	    }
	
	    /* Remember the parsed XML for later use */
	    *output = root;
	    return pcmk_ok;
	}
	
	/*!
	 * \internal
	 * \brief Sign on a native client to the CIB API
	 *
	 * \param[in,out] cib   CIB connection (client)
	 * \param[in]     name  Ignored
	 * \param[in]     type  Ignored
	 */
	static int
	file_signon(cib_t *cib, const char *name, enum cib_conn_type type)
	{
	    int rc = pcmk_ok;
	    file_opaque_t *private = cib->variant_opaque;
	
	    name = pcmk__s(crm_system_name, "client");
	
	    if (private->filename == NULL) {
	        rc = -EINVAL;
	    } else {
	        rc = load_file_cib(private->filename, &private->cib_xml);
	    }
	
	    if (rc == pcmk_ok) {
	        pcmk__debug("Opened connection to local file '%s' for %s",
	                    private->filename, name);
	        cib->state = cib_connected_command;
	        register_client(cib);
	
	    } else {
	        pcmk__info("Connection to local file '%s' for %s (client %s) failed: "
	                   "%s", private->filename, name, private->id,
	                   pcmk_strerror(rc));
	    }
	    return rc;
	}
	
	/*!
	 * \internal
	 * \brief Write out the in-memory CIB to a live CIB file
	 *
	 * \param[in]     cib_root  Root of XML tree to write
	 * \param[in,out] path      Full path to file to write
	 *
	 * \return Standard Pacemaker return code
	 */
	static int
	write_live(xmlNode *cib_root, char *path)
	{
	    uid_t euid = geteuid();
	    uid_t daemon_uid = 0;
	    gid_t daemon_gid = 0;
	    char *sep = strrchr(path, '/');
	    const char *cib_dirname, *cib_filename;
	    int rc = pcmk_rc_ok;
	
	    /* Get the desired uid/gid */
	    rc = pcmk__daemon_user(&daemon_uid, &daemon_gid);
	    if (rc != pcmk_rc_ok) {
	        pcmk__err("Could not find user " CRM_DAEMON_USER ": %s",
	                  pcmk_rc_str(rc));
	        return rc;
	    }
	
	    /* If we're root, we can change the ownership;
	     * if we're daemon, anything we create will be OK;
	     * otherwise, block access so we don't create wrong owner
	     */
	    if ((euid != 0) && (euid != daemon_uid)) {
	        pcmk__err("Must be root or " CRM_DAEMON_USER " to modify live CIB");
	
	        // @TODO Should this return an error instead?
	        return pcmk_rc_ok;
	    }
	
	    /* fancy footwork to separate dirname from filename
	     * (we know the canonical name maps to the live CIB,
	     * but the given name might be relative, or symlinked)
	     */
	    if (sep == NULL) { /* no directory component specified */
	        cib_dirname = "./";
	        cib_filename = path;
	    } else if (sep == path) { /* given name is in / */
	        cib_dirname = "/";
	        cib_filename = path + 1;
	    } else { /* typical case; split given name into parts */
	        *sep = '\0';
	        cib_dirname = path;
	        cib_filename = sep + 1;
	    }
	
	    /* if we're root, we want to update the file ownership */
	    if (euid == 0) {
	        file_owner = daemon_uid;
	        file_group = daemon_gid;
	        do_chown = true;
	    }
	
	    /* write the file */
	    rc = cib_file_write_with_digest(cib_root, cib_dirname, cib_filename);
	    rc = pcmk_legacy2rc(rc);
	
	    /* turn off file ownership changes, for other callers */
	    if (euid == 0) {
	        do_chown = false;
	    }
	
	    /* undo fancy stuff */
	    if ((sep != NULL) && (*sep == '\0')) {
	        *sep = '/';
	    }
	
	    return rc;
	}
	
	/*!
	 * \internal
	 * \brief Sign-off method for CIB file variants
	 *
	 * This will write the file to disk if needed, and free the in-memory CIB. If
	 * the file is the live CIB, it will compute and write a signature as well.
	 *
	 * \param[in,out] cib  CIB object to sign off
	 *
	 * \return pcmk_ok on success, pcmk_err_generic on failure
	 * \todo This method should refuse to write the live CIB if the CIB manager is
	 *       running.
	 */
	static int
	file_signoff(cib_t *cib)
	{
	    int rc = pcmk_ok;
	    file_opaque_t *private = cib->variant_opaque;
	
	    pcmk__debug("Disconnecting from the CIB manager");
	    cib->state = cib_disconnected;
	    unregister_client(cib);
	    cib->cmds->end_transaction(cib, false, cib_none);
	
	    /* If the in-memory CIB has been changed, write it to disk */
	    if (pcmk__is_set(private->flags, file_flag_dirty)) {
	
	        /* If this is the live CIB, write it out with a digest */
	        if (pcmk__is_set(private->flags, file_flag_live)) {
	            rc = write_live(private->cib_xml, private->filename);
	            rc = pcmk_rc2legacy(rc);
	
	        /* Otherwise, it's a simple write */
	        } else {
	            bool compress = g_str_has_suffix(private->filename, ".bz2");
	
	            if (pcmk__xml_write_file(private->cib_xml, private->filename,
	                                     compress) != pcmk_rc_ok) {
	                rc = pcmk_err_generic;
	            }
	        }
	
	        if (rc == pcmk_ok) {
	            pcmk__info("Wrote CIB to %s", private->filename);
	            clear_file_flags(private, file_flag_dirty);
	        } else {
	            pcmk__err("Could not write CIB to %s", private->filename);
	        }
	    }
	
	    /* Free the in-memory CIB */
	    g_clear_pointer(&private->cib_xml, pcmk__xml_free);
	    return rc;
	}
	
	static int
	file_free(cib_t *cib)
	{
	    int rc = pcmk_ok;
	
	    if (cib->state != cib_disconnected) {
	        rc = file_signoff(cib);
	    }
	
	    if (rc == pcmk_ok) {
	        file_opaque_t *private = cib->variant_opaque;
	
	        free(private->id);
	        free(private->filename);
	        free(private);
	        free(cib->cmds);
	        free(cib->user);
	        free(cib);
	
	    } else {
	        fprintf(stderr, "Couldn't sign off: %d\n", rc);
	    }
	
	    return rc;
	}
	
	static int
	file_register_notification(cib_t *cib, const char *callback, int enabled)
	{
	    return -EPROTONOSUPPORT;
	}
	
	static int
	file_set_connection_dnotify(cib_t *cib, void (*dnotify)(void *user_data))
	{
	    return -EPROTONOSUPPORT;
	}
	
	/*!
	 * \internal
	 * \brief Get the given CIB connection's unique client identifier
	 *
	 * \param[in]  cib       CIB connection
	 * \param[out] async_id  If not \p NULL, where to store asynchronous client ID
	 * \param[out] sync_id   If not \p NULL, where to store synchronous client ID
	 *
	 * \return Legacy Pacemaker return code
	 *
	 * \note This is the \p cib_file variant implementation of
	 *       \p cib_api_operations_t:client_id().
	 */
	static int
	file_client_id(const cib_t *cib, const char **async_id, const char **sync_id)
	{
	    file_opaque_t *private = cib->variant_opaque;
	
	    if (async_id != NULL) {
	        *async_id = private->id;
	    }
	    if (sync_id != NULL) {
	        *sync_id = private->id;
	    }
	    return pcmk_ok;
	}
	
	cib_t *
	cib_file_new(const char *cib_location)
	{
	    cib_t *cib = NULL;
	    file_opaque_t *private = NULL;
	    char *filename = NULL;
	

	    if (cib_location == NULL) {
	        cib_location = getenv("CIB_file");

	        if (cib_location == NULL) {
	            return NULL; // Shouldn't be possible if we were called internally
	        }
	    }
	

	    cib = cib_new_variant();

	    if (cib == NULL) {
	        return NULL;
	    }
	
	    filename = strdup(cib_location);

	    if (filename == NULL) {
	        free(cib);
	        return NULL;
	    }
	
	    private = calloc(1, sizeof(file_opaque_t));

	    if (private == NULL) {

	        free(cib);
	        free(filename);
	        return NULL;
	    }
	
	    private->id = pcmk__generate_uuid();
	    private->filename = filename;
	
	    cib->variant = cib_file;
	    cib->variant_opaque = private;
	
	    private->flags = 0;
	    if (is_live(cib_location)) {
	        set_file_flags(private, file_flag_live);
	        pcmk__trace("File %s detected as live CIB", cib_location);
	    }
	
	    /* assign variant specific ops */
	    cib->delegate_fn = file_perform_op_delegate;
	    cib->cmds->signon = file_signon;
	    cib->cmds->signoff = file_signoff;
	    cib->cmds->free = file_free;
	    cib->cmds->register_notification = file_register_notification;
	    cib->cmds->set_connection_dnotify = file_set_connection_dnotify;
	
	    cib->cmds->client_id = file_client_id;
	
	    return cib;
	}
	
	/*!
	 * \internal
	 * \brief Compare the calculated digest of an XML tree against a signature file
	 *
	 * \param[in] root     Root of XML tree to compare
	 * \param[in] sigfile  Name of signature file containing digest to compare
	 *
	 * \return \c true if digests match or signature file does not exist, or
	 *         \c false otherwise
	 */
	static bool
	verify_digest(xmlNode *root, const char *sigfile)
	{
	    bool passed = false;
	    char *expected;
	    int rc = pcmk__file_contents(sigfile, &expected);
	
	    switch (rc) {
	        case pcmk_rc_ok:
	            if (expected == NULL) {
	                pcmk__err("On-disk digest at %s is empty", sigfile);
	                return false;
	            }
	            break;
	        case ENOENT:
	            pcmk__warn("No on-disk digest present at %s", sigfile);
	            return true;
	        default:
	            pcmk__err("Could not read on-disk digest from %s: %s", sigfile,
	                      pcmk_rc_str(rc));
	            return false;
	    }
	    passed = pcmk__verify_digest(root, expected);
	    free(expected);
	    return passed;
	}
	
	/*!
	 * \internal
	 * \brief Read an XML tree from a file and verify its digest
	 *
	 * \param[in]  filename  Name of XML file to read
	 * \param[in]  sigfile   Name of signature file containing digest to compare
	 * \param[out] root      If non-NULL, will be set to pointer to parsed XML tree
	 *
	 * \return 0 if file was successfully read, parsed and verified, otherwise:
	 *         -errno on stat() failure,
	 *         -pcmk_err_cib_corrupt if file size is 0 or XML is not parseable, or
	 *         -pcmk_err_cib_modified if digests do not match
	 * \note If root is non-NULL, it is the caller's responsibility to free *root on
	 *       successful return.
	 */
	int
	cib_file_read_and_verify(const char *filename, const char *sigfile, xmlNode **root)
	{
	    int s_res;
	    struct stat buf;
	    char *local_sigfile = NULL;
	    xmlNode *local_root = NULL;
	
	    pcmk__assert(filename != NULL);
	    if (root) {
	        *root = NULL;
	    }
	
	    /* Verify that file exists and its size is nonzero */
	    s_res = stat(filename, &buf);
	    if (s_res < 0) {
	        pcmk__warn("Could not verify cluster configuration file %s: "
	                   "stat() failed: %s",
	                   filename, strerror(errno));
	        return -errno;
	    } else if (buf.st_size == 0) {
	        pcmk__warn("Cluster configuration file %s is corrupt (size is zero)",
	                   filename);
	        return -pcmk_err_cib_corrupt;
	    }
	
	    /* Parse XML */
	    local_root = pcmk__xml_read(filename);
	    if (local_root == NULL) {
	        pcmk__warn("Cluster configuration file %s is corrupt (unparseable as "
	                   "XML)",
	                   filename);
	        return -pcmk_err_cib_corrupt;
	    }
	
	    /* If sigfile is not specified, use original file name plus .sig */
	    if (sigfile == NULL) {
	        sigfile = local_sigfile = pcmk__assert_asprintf("%s.sig", filename);
	    }
	
	    /* Verify that digests match */
	    if (!verify_digest(local_root, sigfile)) {
	        free(local_sigfile);
	        pcmk__xml_free(local_root);
	        return -pcmk_err_cib_modified;
	    }
	
	    free(local_sigfile);
	    if (root) {
	        *root = local_root;
	    } else {
	        pcmk__xml_free(local_root);
	    }
	    return pcmk_ok;
	}
	
	/*!
	 * \internal
	 * \brief Back up a CIB
	 *
	 * \param[in] cib_dirname Directory containing CIB file and backups
	 * \param[in] cib_filename Name (relative to cib_dirname) of CIB file to back up
	 *
	 * \return 0 on success, -1 on error
	 */
	static int
	backup_cib_file(const char *cib_dirname, const char *cib_filename)
	{
	    int rc = 0;
	    unsigned int seq = 0U;
	    char *cib_path = pcmk__assert_asprintf("%s/%s", cib_dirname, cib_filename);
	    char *cib_digest = pcmk__assert_asprintf("%s.sig", cib_path);
	    char *backup_path;
	    char *backup_digest;
	
	    // Determine backup and digest file names
	    if (pcmk__read_series_sequence(cib_dirname, CIB_SERIES,
	                                   &seq) != pcmk_rc_ok) {
	        // @TODO maybe handle errors better ...
	        seq = 0U;
	    }
	
	    // Must pass false because archived copies are created with hard links
	    backup_path = pcmk__series_filename(cib_dirname, CIB_SERIES, seq, false);
	    backup_digest = pcmk__assert_asprintf("%s.sig", backup_path);
	
	    /* Remove the old backups if they exist */
	    unlink(backup_path);
	    unlink(backup_digest);
	
	    /* Back up the CIB, by hard-linking it to the backup name */
	    if ((link(cib_path, backup_path) < 0) && (errno != ENOENT)) {
	        pcmk__err("Could not archive %s by linking to %s: %s", cib_path,
	                  backup_path, strerror(errno));
	        rc = -1;
	
	    /* Back up the CIB signature similarly */
	    } else if ((link(cib_digest, backup_digest) < 0) && (errno != ENOENT)) {
	        pcmk__err("Could not archive %s by linking to %s: %s", cib_digest,
	                  backup_digest, strerror(errno));
	        rc = -1;
	
	    /* Update the last counter and ensure everything is sync'd to media */
	    } else {
	        pcmk__write_series_sequence(cib_dirname, CIB_SERIES, ++seq,
	                                    CIB_SERIES_MAX);
	        if (do_chown) {
	            int rc2;
	
	            if ((chown(backup_path, file_owner, file_group) < 0)
	                && (errno != ENOENT)) {
	
	                pcmk__err("Could not set owner of %s: %s", backup_path,
	                          strerror(errno));
	                rc = -1;
	            }
	            if ((chown(backup_digest, file_owner, file_group) < 0)
	                && (errno != ENOENT)) {
	
	                pcmk__err("Could not set owner of %s: %s", backup_digest,
	                          strerror(errno));
	                rc = -1;
	            }
	            rc2 = pcmk__chown_series_sequence(cib_dirname, CIB_SERIES,
	                                              file_owner, file_group);
	            if (rc2 != pcmk_rc_ok) {
	                pcmk__err("Could not set owner of sequence file in %s: %s",
	                          cib_dirname, pcmk_rc_str(rc2));
	                rc = -1;
	            }
	        }
	        pcmk__sync_directory(cib_dirname);
	        pcmk__info("Archived previous version as %s", backup_path);
	    }
	
	    free(cib_path);
	    free(cib_digest);
	    free(backup_path);
	    free(backup_digest);
	    return rc;
	}
	
	/*!
	 * \internal
	 * \brief Prepare CIB XML to be written to disk
	 *
	 * Set \c PCMK_XA_NUM_UPDATES to 0, set \c PCMK_XA_CIB_LAST_WRITTEN to the
	 * current timestamp, and strip out the status section.
	 *
	 * \param[in,out] root  Root of CIB XML tree
	 *
	 * \return void
	 */
	static void
	prepare_xml(xmlNode *root)
	{
	    xmlNode *cib_status_root = NULL;
	
	    /* Always write out with num_updates=0 and current last-written timestamp */
	    pcmk__xe_set(root, PCMK_XA_NUM_UPDATES, "0");
	    pcmk__xe_add_last_written(root);
	
	    /* Delete status section before writing to file, because
	     * we discard it on startup anyway, and users get confused by it */
	    cib_status_root = pcmk__xe_first_child(root, PCMK_XE_STATUS, NULL, NULL);
	    CRM_CHECK(cib_status_root != NULL, return);
	    pcmk__xml_free(cib_status_root);
	}
	
	/*!
	 * \internal
	 * \brief Write CIB to disk, along with a signature file containing its digest
	 *
	 * \param[in,out] cib_root      Root of XML tree to write
	 * \param[in]     cib_dirname   Directory containing CIB and signature files
	 * \param[in]     cib_filename  Name (relative to cib_dirname) of file to write
	 *
	 * \return pcmk_ok on success,
	 *         pcmk_err_cib_modified if existing cib_filename doesn't match digest,
	 *         pcmk_err_cib_backup if existing cib_filename couldn't be backed up,
	 *         or pcmk_err_cib_save if new cib_filename couldn't be saved
	 */
	int
	cib_file_write_with_digest(xmlNode *cib_root, const char *cib_dirname,
	                           const char *cib_filename)
	{
	    int exit_rc = pcmk_ok;
	    int rc, fd;
	    char *digest = NULL;
	
	    /* Detect CIB version for diagnostic purposes */
	    const char *epoch = pcmk__xe_get(cib_root, PCMK_XA_EPOCH);
	    const char *admin_epoch = pcmk__xe_get(cib_root, PCMK_XA_ADMIN_EPOCH);
	
	    /* Determine full CIB and signature pathnames */
	    char *cib_path = pcmk__assert_asprintf("%s/%s", cib_dirname, cib_filename);
	    char *digest_path = pcmk__assert_asprintf("%s.sig", cib_path);
	
	    /* Create temporary file name patterns for writing out CIB and signature */
	    char *tmp_cib = pcmk__assert_asprintf("%s/cib.XXXXXX", cib_dirname);
	    char *tmp_digest = pcmk__assert_asprintf("%s/cib.XXXXXX", cib_dirname);
	
	    /* Ensure the admin didn't modify the existing CIB underneath us */
	    pcmk__trace("Reading cluster configuration file %s", cib_path);
	    rc = cib_file_read_and_verify(cib_path, NULL, NULL);
	    if ((rc != pcmk_ok) && (rc != -ENOENT)) {
	        pcmk__err("%s was manually modified while the cluster was active!",
	                  cib_path);
	        exit_rc = pcmk_err_cib_modified;
	        goto cleanup;
	    }
	
	    /* Back up the existing CIB */
	    if (backup_cib_file(cib_dirname, cib_filename) < 0) {
	        exit_rc = pcmk_err_cib_backup;
	        goto cleanup;
	    }
	
	    pcmk__debug("Writing CIB to disk");
	    umask(S_IWGRP | S_IWOTH | S_IROTH);
	    prepare_xml(cib_root);
	
	    /* Write the CIB to a temporary file, so we can deploy (near) atomically */
	    fd = mkstemp(tmp_cib);
	    if (fd < 0) {
	        pcmk__err("Couldn't open temporary file %s for writing CIB: %s",
	                  tmp_cib, strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	        goto cleanup;
	    }
	
	    /* Protect the temporary file */
	    if (fchmod(fd, S_IRUSR | S_IWUSR) < 0) {
	        pcmk__err("Couldn't protect temporary file %s for writing CIB: %s",
	                  tmp_cib, strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	        goto cleanup;
	    }
	    if (do_chown && (fchown(fd, file_owner, file_group) < 0)) {
	        pcmk__err("Couldn't protect temporary file %s for writing CIB: %s",
	                  tmp_cib, strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	        goto cleanup;
	    }
	
	    /* Write out the CIB */
	    if (pcmk__xml_write_fd(cib_root, tmp_cib, fd) != pcmk_rc_ok) {
	        pcmk__err("Changes couldn't be written to %s", tmp_cib);
	        exit_rc = pcmk_err_cib_save;
	        goto cleanup;
	    }
	
	    /* Calculate CIB digest */
	    digest = pcmk__digest_on_disk_cib(cib_root);
	    pcmk__assert(digest != NULL);
	    pcmk__info("Wrote version %s.%s.0 of the CIB to disk (digest: %s)",
	               pcmk__s(admin_epoch, "0"), pcmk__s(epoch, "0"), digest);
	
	    /* Write the CIB digest to a temporary file */
	    fd = mkstemp(tmp_digest);
	    if (fd < 0) {
	        pcmk__err("Could not create temporary file %s for CIB digest: %s",
	                  tmp_digest, strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	        goto cleanup;
	    }
	    if (do_chown && (fchown(fd, file_owner, file_group) < 0)) {
	        pcmk__err("Couldn't protect temporary file %s for writing CIB: %s",
	                  tmp_cib, strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	        close(fd);
	        goto cleanup;
	    }
	    rc = pcmk__write_sync(fd, digest);
	    if (rc != pcmk_rc_ok) {
	        pcmk__err("Could not write digest to %s: %s", tmp_digest,
	                  pcmk_rc_str(rc));
	        exit_rc = pcmk_err_cib_save;
	        close(fd);
	        goto cleanup;
	    }
	    close(fd);
	    pcmk__debug("Wrote digest %s to disk", digest);
	
	    /* Verify that what we wrote is sane */
	    pcmk__info("Reading cluster configuration file %s (digest: %s)", tmp_cib,
	               tmp_digest);
	    rc = cib_file_read_and_verify(tmp_cib, tmp_digest, NULL);
	    pcmk__assert(rc == 0);
	
	    /* Rename temporary files to live, and sync directory changes to media */
	    pcmk__debug("Activating %s", tmp_cib);
	    if (rename(tmp_cib, cib_path) < 0) {
	        pcmk__err("Couldn't rename %s as %s: %s", tmp_cib, cib_path,
	                  strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	    }
	    if (rename(tmp_digest, digest_path) < 0) {
	        pcmk__err("Couldn't rename %s as %s: %s", tmp_digest, digest_path,
	                  strerror(errno));
	        exit_rc = pcmk_err_cib_save;
	    }
	    pcmk__sync_directory(cib_dirname);
	
	  cleanup:
	    free(cib_path);
	    free(digest_path);
	    free(digest);
	    free(tmp_digest);
	    free(tmp_cib);
	    return exit_rc;
	}