util.c

    ** (in fact, it certainly will not: a dummy_header only occurs for the
    **  UNLOCK method, the parent is checked only for locknull resources,
    **  and the parent certainly does not have the (locknull's) locktoken)
    */
    if (lock_list == NULL && if_header->dummy_header) {
        if (flags & DAV_VALIDATE_IS_PARENT)
            return NULL;
        return dav_new_error(p, HTTP_BAD_REQUEST, 0, 0,
                             "The locktoken specified in the \"Lock-Token:\" "
                             "header is invalid because this resource has no "
                             "outstanding locks.");
    }

    /*
    ** Prepare the input URI. We want the URI to never have a trailing slash.
    **
    ** When URIs are placed into the dav_if_header structure, they are
    ** guaranteed to never have a trailing slash. If the URIs are equivalent,
    ** then it doesn't matter if they both lack a trailing slash -- they're
    ** still equivalent.
    **
    ** Note: we could also ensure that a trailing slash is present on both
    ** URIs, but the majority of URIs provided to us via a resource walk
    ** will not contain that trailing slash.
    */
    uri = resource->uri;
    uri_len = strlen(uri);
    if (uri[uri_len - 1] == '/') {
        dav_set_bufsize(p, pbuf, uri_len);
        memcpy(pbuf->buf, uri, uri_len);
        pbuf->buf[--uri_len] = '\0';
        uri = pbuf->buf;
    }

    /* get the resource's etag; we may need it during the checks */
    etag = (*resource->hooks->getetag)(resource);

    /* how many state_lists apply to this URI? */
    num_that_apply = 0;

    /* If there are if-headers, fail if this resource
     * does not match at least one state_list.
     */
    for (ifhdr_scan = if_header;
         ifhdr_scan != NULL;
         ifhdr_scan = ifhdr_scan->next) {

        /* DBG2("uri=<%s>  if_uri=<%s>", uri, ifhdr_scan->uri ? ifhdr_scan->uri : "(no uri)"); */

        if (ifhdr_scan->uri != NULL
            && (uri_len != ifhdr_scan->uri_len
                || memcmp(uri, ifhdr_scan->uri, uri_len) != 0)) {
            /*
            ** A tagged-list's URI doesn't match this resource's URI.
            ** Skip to the next state_list to see if it will match.
            */
            continue;
        }

        /* this state_list applies to this resource */

        /*
        ** ### only one state_list should ever apply! a no-tag, or a tagged
        ** ### where S9.4.2 states only one can match.
        **
        ** ### revamp this code to loop thru ifhdr_scan until we find the
        ** ### matching state_list. process it. stop.
        */
        ++num_that_apply;

        /* To succeed, resource must match *all* of the states
         * specified in the state_list.
         */
        for (state_list = ifhdr_scan->state;
             state_list != NULL;
             state_list = state_list->next) {

            switch(state_list->type) {
            case dav_if_etag:
            {
                const char *given_etag, *current_etag;
                int mismatch;

                /* Do a weak entity comparison function as defined in
                 * RFC 2616 13.3.3.
                 */
                if (state_list->etag[0] == 'W' &&
                    state_list->etag[1] == '/') {
                    given_etag = state_list->etag + 2;
                }
                else {
                    given_etag = state_list->etag;
                }
                if (etag[0] == 'W' &&
                    etag[1] == '/') {
                    current_etag = etag + 2;
                }
                else {
                    current_etag = etag;
                }

                mismatch = strcmp(given_etag, current_etag);

                if (state_list->condition == DAV_IF_COND_NORMAL && mismatch) {
                    /*
                    ** The specified entity-tag does not match the
                    ** entity-tag on the resource. This state_list is
                    ** not going to match. Bust outta here.
                    */
                    reason =
                        "an entity-tag was specified, but the resource's "
                        "actual ETag does not match.";
                    goto state_list_failed;
                }
                else if (state_list->condition == DAV_IF_COND_NOT
                         && !mismatch) {
                    /*
                    ** The specified entity-tag DOES match the
                    ** entity-tag on the resource. This state_list is
                    ** not going to match. Bust outta here.
                    */
                    reason =
                        "an entity-tag was specified using the \"Not\" form, "
                        "but the resource's actual ETag matches the provided "
                        "entity-tag.";
                    goto state_list_failed;
                }
                break;
            }

            case dav_if_opaquelock:
                if (lockdb == NULL) {
                    if (state_list->condition == DAV_IF_COND_NOT) {
                        /* the locktoken is definitely not there! (success) */
                        continue;
                    }

                    /* condition == DAV_IF_COND_NORMAL */

                    /*
                    ** If no lockdb is provided, then validation fails for
                    ** this state_list (NORMAL means we were supposed to
                    ** find the token, which we obviously cannot do without
                    ** a lock database).
                    **
                    ** Go and try the next state list.
                    */
                    reason =
                        "a State-token was supplied, but a lock database "
                        "is not available for to provide the required lock.";
                    goto state_list_failed;
                }

                /* Resource validation 'fails' if:
                 *    ANY  of the lock->locktokens match
                 *         a NOT state_list->locktoken,
                 * OR
                 *    NONE of the lock->locktokens match
                 *         a NORMAL state_list->locktoken.
                 */
                num_matched = 0;
                for (lock = lock_list; lock != NULL; lock = lock->next) {

                    /*
                    DBG2("compare: rsrc=%s  ifhdr=%s",
                         (*locks_hooks->format_locktoken)(p, lock->locktoken),
                         (*locks_hooks->format_locktoken)(p, state_list->locktoken));
                    */

                    /* nothing to do if the locktokens do not match. */
                    if ((*locks_hooks->compare_locktoken)(state_list->locktoken, lock->locktoken)) {
                        continue;
                    }

                    /*
                    ** We have now matched up one of the resource's locktokens
                    ** to a locktoken in a State-token in the If: header.
                    ** Note this fact, so that we can pass the overall
                    ** requirement of seeing at least one of the resource's
                    ** locktokens.
                    */
                    seen_locktoken = 1;

                    if (state_list->condition == DAV_IF_COND_NOT) {
                        /*
                        ** This state requires that the specified locktoken
                        ** is NOT present on the resource. But we just found
                        ** it. There is no way this state-list can now
                        ** succeed, so go try another one.
                        */
                        reason =
                            "a State-token was supplied, which used a "
                            "\"Not\" condition. The State-token was found "
                            "in the locks on this resource";
                        goto state_list_failed;
                    }

                    /* condition == DAV_IF_COND_NORMAL */

                    /* Validate auth_user:  If an authenticated user created
                    ** the lock, only the same user may submit that locktoken
                    ** to manipulate a resource.
                    */
                    if (lock->auth_user &&
                        (!r->user ||
                         strcmp(lock->auth_user, r->user))) {
                        const char *errmsg;

                        errmsg = apr_pstrcat(p, "User \"",
                                            r->user,
                                            "\" submitted a locktoken created "
                                            "by user \"",
                                            lock->auth_user, "\".", NULL);
                        return dav_new_error(p, HTTP_FORBIDDEN, 0, 0, errmsg);
                    }

                    /*
                    ** We just matched a specified State-Token to one of the
                    ** resource's locktokens.
                    **
                    ** Break out of the lock scan -- we only needed to find
                    ** one match (actually, there shouldn't be any other
                    ** matches in the lock list).
                    */
                    num_matched = 1;
                    break;
                }

                if (num_matched == 0
                    && state_list->condition == DAV_IF_COND_NORMAL) {
                    /*
                    ** We had a NORMAL state, meaning that we should have
                    ** found the State-Token within the locks on this
                    ** resource. We didn't, so this state_list must fail.
                    */
                    reason =
                        "a State-token was supplied, but it was not found "
                        "in the locks on this resource.";
                    goto state_list_failed;
                }

                break;

            case dav_if_unknown:
                /* Request is predicated on some unknown state token,
                 * which must be presumed to *not* match, so fail
                 * unless this is a Not condition. */

                if (state_list->condition == DAV_IF_COND_NORMAL) {
                    reason =
                        "an unknown state token was supplied";
                    goto state_list_failed;
                }
                break;

            } /* switch */
        } /* foreach ( state_list ) */

        /*
        ** We've checked every state in this state_list and none of them
        ** have failed. Since all of them succeeded, then we have a matching
        ** state list and we may be done.
        **
        ** The next requirement is that we have seen one of the resource's
        ** locktokens (if any). If we have, then we can just exit. If we
        ** haven't, then we need to keep looking.
        */
        if (seen_locktoken) {
            /* woo hoo! */
            return NULL;
        }

        /*
        ** Haven't seen one. Let's break out of the search and just look
        ** for a matching locktoken.
        */
        break;

        /*
        ** This label is used when we detect that a state_list is not
        ** going to match this resource. We bust out and try the next
        ** state_list.
        */
      state_list_failed:
        ;

    } /* foreach ( ifhdr_scan ) */

    /*
    ** The above loop exits for one of two reasons:
    **   1) a state_list matched and seen_locktoken is false.
    **   2) all if_header structures were scanned, without (1) occurring
    */

    if (ifhdr_scan == NULL) {
        /*
        ** We finished the loop without finding any matching state lists.
        */

        /*
        ** If none of the state_lists apply to this resource, then we
        ** may have succeeded. Note that this scenario implies a
        ** tagged-list with no matching state_lists. If the If: header
        ** was a no-tag-list, then it would have applied to this resource.
        **
        ** S9.4.2 states that when no state_lists apply, then the header
        ** should be ignored.
        **
        ** If we saw one of the resource's locktokens, then we're done.
        ** If we did not see a locktoken, then we fail.
        */
        if (num_that_apply == 0) {
            if (seen_locktoken)
                return NULL;

            /*
            ** We may have aborted the scan before seeing the locktoken.
            ** Rescan the If: header to see if we can find the locktoken
            ** somewhere.
            **
            ** Note that seen_locktoken == 0 implies lock_list != NULL
            ** which implies locks_hooks != NULL.
            */
            if (dav_find_submitted_locktoken(if_header, lock_list,
                                             locks_hooks)) {
                /*
                ** We found a match! We're set... none of the If: header
                ** assertions apply (implicit success), and the If: header
                ** specified the locktoken somewhere. We're done.
                */
                return NULL;
            }

            return dav_new_error(p, HTTP_LOCKED, 0 /* error_id */, 0,
                                 "This resource is locked and the \"If:\" "
                                 "header did not specify one of the "
                                 "locktokens for this resource's lock(s).");
        }
        /* else: one or more state_lists were applicable, but failed. */

        /*
        ** If the dummy_header did not match, then they specified an
        ** incorrect token in the Lock-Token header. Forget whether the
        ** If: statement matched or not... we'll tell them about the
        ** bad Lock-Token first. That is considered a 400 (Bad Request).
        */
        if (if_header->dummy_header) {
            return dav_new_error(p, HTTP_BAD_REQUEST, 0, 0,
                                 "The locktoken specified in the "
                                 "\"Lock-Token:\" header did not specify one "
                                 "of this resource's locktoken(s).");
        }

        if (reason == NULL) {
            return dav_new_error(p, HTTP_PRECONDITION_FAILED, 0, 0,
                                 "The preconditions specified by the \"If:\" "
                                 "header did not match this resource.");
        }

        return dav_new_error(p, HTTP_PRECONDITION_FAILED, 0, 0,
                             apr_psprintf(p,
                                         "The precondition(s) specified by "
                                         "the \"If:\" header did not match "
                                         "this resource. At least one "
                                         "failure is because: %s", reason));
    }

    /* assert seen_locktoken == 0 */

    /*
    ** ifhdr_scan != NULL implies we found a matching state_list.
    **
    ** Since we're still here, it also means that we have not yet found
    ** one the resource's locktokens in the If: header.
    **
    ** Scan all the if_headers and states looking for one of this
    ** resource's locktokens. Note that we need to go back and scan them
    ** all -- we may have aborted a scan with a failure before we saw a
    ** matching token.
    **
    ** Note that seen_locktoken == 0 implies lock_list != NULL which implies
    ** locks_hooks != NULL.
    */
    if (dav_find_submitted_locktoken(if_header, lock_list, locks_hooks)) {
        /*
        ** We found a match! We're set... we have a matching state list,
        ** and the If: header specified the locktoken somewhere. We're done.
        */
        return NULL;
    }

    /*
    ** We had a matching state list, but the user agent did not specify one
    ** of this resource's locktokens. Tell them so.
    **
    ** Note that we need to special-case the message on whether a "dummy"
    ** header exists. If it exists, yet we didn't see a needed locktoken,
    ** then that implies the dummy header (Lock-Token header) did NOT
    ** specify one of this resource's locktokens. (this implies something
    ** in the real If: header matched)
    **
    ** We want to note the 400 (Bad Request) in favor of a 423 (Locked).
    */
    if (if_header->dummy_header) {
        return dav_new_error(p, HTTP_BAD_REQUEST, 0, 0,
                             "The locktoken specified in the "
                             "\"Lock-Token:\" header did not specify one "
                             "of this resource's locktoken(s).");
    }

    return dav_new_error(p, HTTP_LOCKED, 1 /* error_id */, 0,
                         "This resource is locked and the \"If:\" header "
                         "did not specify one of the "
                         "locktokens for this resource's lock(s).");
}

/* dav_validate_walker:  Walker callback function to validate resource state */
static dav_error * dav_validate_walker(dav_walk_resource *wres, int calltype)
{
    dav_walker_ctx *ctx = wres->walk_ctx;
    dav_error *err;

    if ((err = dav_validate_resource_state(ctx->w.pool, wres->resource,
                                           ctx->w.lockdb,
                                           ctx->if_header, ctx->flags,
                                           &ctx->work_buf, ctx->r)) == NULL) {
        /* There was no error, so just bug out. */
        return NULL;
    }

    /*
    ** If we have a serious server error, or if the request itself failed,
    ** then just return error (not a multistatus).
    */
    if (ap_is_HTTP_SERVER_ERROR(err->status)
        || (*wres->resource->hooks->is_same_resource)(wres->resource,
                                                      ctx->w.root)) {
        /* ### maybe push a higher-level description? */
        return err;
    }

    /* associate the error with the current URI */
    dav_add_response(wres, err->status, NULL);

    return NULL;
}

/* If-* header checking */
static int dav_meets_conditions(request_rec *r, int resource_state)
{
    const char *if_match, *if_none_match;
    int retVal;

    /* If-Match '*' fix. Resource existence not checked by ap_meets_conditions.
     * If-Match '*' request should succeed only if the resource exists. */
    if ((if_match = apr_table_get(r->headers_in, "If-Match")) != NULL) {
        if (if_match[0] == '*' && resource_state != DAV_RESOURCE_EXISTS)
            return HTTP_PRECONDITION_FAILED;
    }

    retVal = ap_meets_conditions(r);

    /* If-None-Match '*' fix. If-None-Match '*' request should succeed
     * if the resource does not exist. */
    if (retVal == HTTP_PRECONDITION_FAILED) {
        /* Note. If if_none_match != NULL, if_none_match is the culprit.
         * Since, in presence of If-None-Match,
         * other If-* headers are undefined. */
        if ((if_none_match =
            apr_table_get(r->headers_in, "If-None-Match")) != NULL) {
            if (if_none_match[0] == '*'
                && resource_state != DAV_RESOURCE_EXISTS) {
                return OK;
            }
        }
    }

    return retVal;
}

/*
** dav_validate_request:  Validate if-headers (and check for locks) on:
**    (1) r->filename @ depth;
**    (2) Parent of r->filename if check_parent == 1
**
** The check of parent should be done when it is necessary to verify that
** the parent collection will accept a new member (ie current resource
** state is null).
**
** Return OK on successful validation.
** On error, return appropriate HTTP_* code, and log error. If a multi-stat
** error is necessary, response will point to it, else NULL.
*/
DAV_DECLARE(dav_error *) dav_validate_request(request_rec *r,
                                              dav_resource *resource,
                                              int depth,
                                              dav_locktoken *locktoken,
                                              dav_response **response,
                                              int flags,
                                              dav_lockdb *lockdb)
{
    dav_error *err;
    int result;
    dav_if_header *if_header;
    int lock_db_opened_locally = 0;
    const dav_hooks_locks *locks_hooks = DAV_GET_HOOKS_LOCKS(r);
    const dav_hooks_repository *repos_hooks = resource->hooks;
    dav_buffer work_buf = { 0 };
    dav_response *new_response;
    int resource_state;
    const char *etag;
    int set_etag = 0;

#if DAV_DEBUG
    if (depth && response == NULL) {
        /*
        ** ### bleck. we can't return errors for other URIs unless we have
        ** ### a "response" ptr.
        */
        return dav_new_error(r->pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                             "DESIGN ERROR: dav_validate_request called "
                             "with depth>0, but no response ptr.");
    }
#endif

    if (response != NULL)
        *response = NULL;

    /* Set the ETag header required by dav_meets_conditions() */
    etag = apr_table_get(r->headers_out, "ETag");
    if (!etag) {
        etag = (*resource->hooks->getetag)(resource);
        if (etag && *etag) {
            apr_table_set(r->headers_out, "ETag", etag);
            set_etag = 1;
        }
    }
    /* Do the standard checks for conditional requests using
     * If-..-Since, If-Match etc */
    resource_state = dav_get_resource_state(r, resource);
    result = dav_meets_conditions(r, resource_state);
    if (set_etag) {
        /*
         * If we have set an ETag to headers out above for
         * dav_meets_conditions() revert this here as we do not want to set
         * the ETag in responses to requests with methods where this might not
         * be desired.
         */
        apr_table_unset(r->headers_out, "ETag");
    }
    if (result != OK) {
        return dav_new_error(r->pool, result, 0, 0, NULL);
    }

    /* always parse (and later process) the If: header */
    if ((err = dav_process_if_header(r, &if_header)) != NULL) {
        /* ### maybe add higher-level description */
        return err;
    }

    /* If a locktoken was specified, create a dummy if_header with which
     * to validate resources.  In the interim, figure out why DAV uses
     * locktokens in an if-header without a Lock-Token header to refresh
     * locks, but a Lock-Token header without an if-header to remove them.
     */
    if (locktoken != NULL) {
        dav_if_header *ifhdr_new;

        ifhdr_new = apr_pcalloc(r->pool, sizeof(*ifhdr_new));
        ifhdr_new->uri = resource->uri;
        ifhdr_new->uri_len = strlen(resource->uri);
        ifhdr_new->dummy_header = 1;

        ifhdr_new->state = apr_pcalloc(r->pool, sizeof(*ifhdr_new->state));
        ifhdr_new->state->type = dav_if_opaquelock;
        ifhdr_new->state->condition = DAV_IF_COND_NORMAL;
        ifhdr_new->state->locktoken = locktoken;

        ifhdr_new->next = if_header;
        if_header = ifhdr_new;
    }

    /*
    ** If necessary, open the lock database (read-only, lazily);
    ** the validation process may need to retrieve or update lock info.
    ** Otherwise, assume provided lockdb is valid and opened rw.
    */
    if (lockdb == NULL) {
        if (locks_hooks != NULL) {
            if ((err = (*locks_hooks->open_lockdb)(r, 0, 0, &lockdb)) != NULL) {
                /* ### maybe insert higher-level comment */
                return err;
            }
            lock_db_opened_locally = 1;
        }
    }

    /* (1) Validate the specified resource, at the specified depth.
     * Avoid the walk there is no if_header and we aren't planning
     * to modify this resource. */
    if (resource->exists && depth > 0 && !(!if_header && flags & DAV_VALIDATE_NO_MODIFY)) {
        dav_walker_ctx ctx = { { 0 } };
        dav_response *multi_status;

        ctx.w.walk_type = DAV_WALKTYPE_NORMAL;
        ctx.w.func = dav_validate_walker;
        ctx.w.walk_ctx = &ctx;
        ctx.w.pool = r->pool;
        ctx.w.root = resource;

        ctx.if_header = if_header;
        ctx.r = r;
        ctx.flags = flags;

        if (lockdb != NULL) {
            ctx.w.lockdb = lockdb;
            ctx.w.walk_type |= DAV_WALKTYPE_LOCKNULL;
        }

        err = (*repos_hooks->walk)(&ctx.w, DAV_INFINITY, &multi_status);
        if (err == NULL) {
            *response = multi_status;
        }
        /* else: implies a 5xx status code occurred. */
    }
    else {
        err = dav_validate_resource_state(r->pool, resource, lockdb,
                                          if_header, flags, &work_buf, r);
    }

    /* (2) Validate the parent resource if requested */
    if (err == NULL && (flags & DAV_VALIDATE_PARENT)) {
        dav_resource *parent_resource;

        err = (*repos_hooks->get_parent_resource)(resource, &parent_resource);

        if (err == NULL && parent_resource == NULL) {
            err = dav_new_error(r->pool, HTTP_FORBIDDEN, 0, 0,
                                "Cannot access parent of repository root.");
        }
        else if (err == NULL) {
            err = dav_validate_resource_state(r->pool, parent_resource, lockdb,
                                              if_header,
                                              flags | DAV_VALIDATE_IS_PARENT,
                                              &work_buf, r);

            /*
            ** This error occurred on the parent resource. This implies that
            ** we have to create a multistatus response (to report the error
            ** against a URI other than the Request-URI). "Convert" this error
            ** into a multistatus response.
            */
            if (err != NULL) {
                new_response = apr_pcalloc(r->pool, sizeof(*new_response));

                new_response->href = parent_resource->uri;
                new_response->status = err->status;
                new_response->desc =
                    "A validation error has occurred on the parent resource, "
                    "preventing the operation on the resource specified by "
                    "the Request-URI.";
                if (err->desc != NULL) {
                    new_response->desc = apr_pstrcat(r->pool,
                                                    new_response->desc,
                                                    " The error was: ",
                                                    err->desc, NULL);
                }

                /* assert: DAV_VALIDATE_PARENT implies response != NULL */
                new_response->next = *response;
                *response = new_response;

                err = NULL;
            }
        }
    }

    if (lock_db_opened_locally)
        (*locks_hooks->close_lockdb)(lockdb);

    /*
    ** If we don't have a (serious) error, and we have multistatus responses,
    ** then we need to construct an "error". This error will be the overall
    ** status returned, and the multistatus responses will go into its body.
    **
    ** For certain methods, the overall error will be a 424. The default is
    ** to construct a standard 207 response.
    */
    if (err == NULL && response != NULL && *response != NULL) {
        apr_text *propstat = NULL;

        if ((flags & DAV_VALIDATE_USE_424) != 0) {
            /* manufacture a 424 error to hold the multistatus response(s) */
            return dav_new_error(r->pool, HTTP_FAILED_DEPENDENCY, 0, 0,
                                 "An error occurred on another resource, "
                                 "preventing the requested operation on "
                                 "this resource.");
        }

        /*
        ** Whatever caused the error, the Request-URI should have a 424
        ** associated with it since we cannot complete the method.
        **
        ** For a LOCK operation, insert an empty DAV:lockdiscovery property.
        ** For other methods, return a simple 424.
        */
        if ((flags & DAV_VALIDATE_ADD_LD) != 0) {
            propstat = apr_pcalloc(r->pool, sizeof(*propstat));
            propstat->text =
                "<D:propstat>" DEBUG_CR
                "<D:prop><D:lockdiscovery/></D:prop>" DEBUG_CR
                "<D:status>HTTP/1.1 424 Failed Dependency</D:status>" DEBUG_CR
                "</D:propstat>" DEBUG_CR;
        }

        /* create the 424 response */
        new_response = apr_pcalloc(r->pool, sizeof(*new_response));
        new_response->href = resource->uri;
        new_response->status = HTTP_FAILED_DEPENDENCY;
        new_response->propresult.propstats = propstat;
        new_response->desc =
            "An error occurred on another resource, preventing the "
            "requested operation on this resource.";

        new_response->next = *response;
        *response = new_response;

        /* manufacture a 207 error for the multistatus response(s) */
        return dav_new_error(r->pool, HTTP_MULTI_STATUS, 0, 0,
                             "Error(s) occurred on resources during the "
                             "validation process.");
    }

    return err;
}

/* dav_get_locktoken_list:
 *
 * Sets ltl to a locktoken_list of all positive locktokens in header,
 * else NULL if no If-header, or no positive locktokens.
 */
DAV_DECLARE(dav_error *) dav_get_locktoken_list(request_rec *r,
                                                dav_locktoken_list **ltl)
{
    dav_error *err;
    dav_if_header *if_header;
    dav_if_state_list *if_state;
    dav_locktoken_list *lock_token = NULL;

    *ltl = NULL;

    if ((err = dav_process_if_header(r, &if_header)) != NULL) {
        /* ### add a higher-level description? */
        return err;
    }

    while (if_header != NULL) {
        if_state = if_header->state;        /* Beginning of the if_state linked list */
        while (if_state != NULL)        {
            if (if_state->condition == DAV_IF_COND_NORMAL
                && if_state->type == dav_if_opaquelock) {
                lock_token = apr_pcalloc(r->pool, sizeof(dav_locktoken_list));
                lock_token->locktoken = if_state->locktoken;
                lock_token->next = *ltl;
                *ltl = lock_token;
            }
            if_state = if_state->next;
        }
        if_header = if_header->next;
    }
    if (*ltl == NULL) {
        /* No nodes added */
        return dav_new_error(r->pool, HTTP_BAD_REQUEST, DAV_ERR_IF_ABSENT, 0,
                             "No locktokens were specified in the \"If:\" "
                             "header, so the refresh could not be performed.");
    }

    return NULL;
}

#if 0 /* not needed right now... */

static const char *strip_white(const char *s, apr_pool_t *pool)
{
    apr_size_t idx;

    /* trim leading whitespace */
    while (apr_isspace(*s))     /* assume: return false for '\0' */
        ++s;

    /* trim trailing whitespace */
    idx = strlen(s) - 1;
    if (apr_isspace(s[idx])) {
        char *s2 = apr_pstrdup(pool, s);

        while (apr_isspace(s2[idx]) && idx > 0)
            --idx;
        s2[idx + 1] = '\0';
        return s2;
    }

    return s;
}
#endif

#define DAV_LABEL_HDR "Label"

/* dav_add_vary_header
 *
 * If there were any headers in the request which require a Vary header
 * in the response, add it.
 */
DAV_DECLARE(void) dav_add_vary_header(request_rec *in_req,
                                      request_rec *out_req,
                                      const dav_resource *resource)
{
    const dav_hooks_vsn *vsn_hooks = DAV_GET_HOOKS_VSN(in_req);

    /* ### this is probably all wrong... I think there is a function in
       ### the Apache API to add things to the Vary header. need to check */

    /* Only versioning headers require a Vary response header,
     * so only do this check if there is a versioning provider */
    if (vsn_hooks != NULL) {
        const char *target = apr_table_get(in_req->headers_in, DAV_LABEL_HDR);

        /* If Target-Selector specified, add it to the Vary header */
        if (target != NULL) {
            const char *vary = apr_table_get(out_req->headers_out, "Vary");

            if (vary == NULL)
                vary = DAV_LABEL_HDR;
            else
                vary = apr_pstrcat(out_req->pool, vary, "," DAV_LABEL_HDR,
                                   NULL);

            apr_table_setn(out_req->headers_out, "Vary", vary);
        }
    }
}

/* dav_can_auto_checkout
 *
 * Determine whether auto-checkout is enabled for a resource.
 * r - the request_rec
 * resource - the resource
 * auto_version - the value of the auto_versionable hook for the resource
 * lockdb - pointer to lock database (opened if necessary)
 * auto_checkout - set to 1 if auto-checkout enabled
 */
static dav_error * dav_can_auto_checkout(
    request_rec *r,
    dav_resource *resource,
    dav_auto_version auto_version,
    dav_lockdb **lockdb,
    int *auto_checkout)
{
    dav_error *err;
    dav_lock *lock_list;

    *auto_checkout = 0;

    if (auto_version == DAV_AUTO_VERSION_ALWAYS) {
        *auto_checkout = 1;
    }
    else if (auto_version == DAV_AUTO_VERSION_LOCKED) {
        if (*lockdb == NULL) {
            const dav_hooks_locks *locks_hooks = DAV_GET_HOOKS_LOCKS(r);

            if (locks_hooks == NULL) {
                return dav_new_error(r->pool, HTTP_INTERNAL_SERVER_ERROR, 0, 0,
                                     "Auto-checkout is only enabled for locked resources, "
                                     "but there is no lock provider.");
            }

            if ((err = (*locks_hooks->open_lockdb)(r, 0, 0, lockdb)) != NULL) {
                return dav_push_error(r->pool, HTTP_INTERNAL_SERVER_ERROR, 0,
                                      "Cannot open lock database to determine "
                                      "auto-versioning behavior.",
                                      err);
            }
        }

        if ((err = dav_lock_query(*lockdb, resource, &lock_list)) != NULL) {
            return dav_push_error(r->pool,
                                  HTTP_INTERNAL_SERVER_ERROR, 0,
                                  "The locks could not be queried for "
                                  "determining auto-versioning behavior.",
                                  err);
        }

        if (lock_list != NULL)
            *auto_checkout = 1;
    }

    return NULL;
}

/* see mod_dav.h for docco */
DAV_DECLARE(dav_error *) dav_auto_checkout(
    request_rec *r,
    dav_resource *resource,
    int parent_only,
    dav_auto_version_info *av_info)
{
    const dav_hooks_vsn *vsn_hooks = DAV_GET_HOOKS_VSN(r);
    dav_lockdb *lockdb = NULL;
    dav_error *err = NULL;

    /* Initialize results */
    memset(av_info, 0, sizeof(*av_info));

    /* if no versioning provider, just return */
    if (vsn_hooks == NULL)
        return NULL;

    /* check parent resource if requested or if resource must be created */
    if (!resource->exists || parent_only) {
        dav_resource *parent;

        if ((err = (*resource->hooks->get_parent_resource)(resource,
                                                           &parent)) != NULL)
            goto done;

        if (parent == NULL || !parent->exists) {
            err = dav_new_error(r->pool, HTTP_CONFLICT, 0, 0,
                                apr_psprintf(r->pool,
                                            "Missing one or more intermediate "
                                            "collections. Cannot create resource %s.",
                                            ap_escape_html(r->pool, resource->uri)));
            goto done;
        }

        av_info->parent_resource = parent;

        /* if parent versioned and not checked out, see if it can be */
        if (parent->versioned && !parent->working) {
            int checkout_parent;

            if ((err = dav_can_auto_checkout(r, parent,
                                             (*vsn_hooks->auto_versionable)(parent),
                                             &lockdb, &checkout_parent))
                != NULL) {
                goto done;
            }

            if (!checkout_parent) {
                err = dav_new_error(r->pool, HTTP_CONFLICT, 0, 0,
                                    "<DAV:cannot-modify-checked-in-parent>");
                goto done;
            }

            /* Try to checkout the parent collection.
             * Note that auto-versioning can only be applied to a version selector,
             * so no separate working resource will be created.
             */
            if ((err = (*vsn_hooks->checkout)(parent, 1 /*auto_checkout*/,
                                              0, 0, 0, NULL, NULL))
                != NULL)
            {
                err = dav_push_error(r->pool, HTTP_CONFLICT, 0,
                                     apr_psprintf(r->pool,
                                                 "Unable to auto-checkout parent collection. "
                                                 "Cannot create resource %s.",
                                                 ap_escape_html(r->pool, resource->uri)),
                                     err);
                goto done;
            }

            /* remember that parent was checked out */
            av_info->parent_checkedout = 1;
        }
    }

    /* if only checking parent, we're done */
    if (parent_only)
        goto done;

    /* if creating a new resource, see if it should be version-controlled */
    if (!resource->exists
        && (*vsn_hooks->auto_versionable)(resource) == DAV_AUTO_VERSION_ALWAYS) {

        if ((err = (*vsn_hooks->vsn_control)(resource, NULL)) != NULL) {
            err = dav_push_error(r->pool, HTTP_CONFLICT, 0,
                                 apr_psprintf(r->pool,
                                             "Unable to create versioned resource %s.",
                                             ap_escape_html(r->pool, resource->uri)),
                                 err);
            goto done;
        }

        /* remember that resource was created */
        av_info->resource_versioned = 1;
    }

    /* if resource is versioned, make sure it is checked out */
    if (resource->versioned && !resource->working) {
        int checkout_resource;

        if ((err = dav_can_auto_checkout(r, resource,