props.c

Apache 2.0.63 is the current stable version of the 2.0 series, and is recommended over any previous

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
** DAV extension module for Apache 2.0.*
**  - Property database handling (repository-independent)
**
** NOTES:
**
**   PROPERTY DATABASE
**
**   This version assumes that there is a per-resource database provider
**   to record properties. The database provider decides how and where to
**   store these databases.
**
**   The DBM keys for the properties have the following form:
**
**     namespace ":" propname
**
**   For example: 5:author
**
**   The namespace provides an integer index into the namespace table
**   (see below). propname is simply the property name, without a namespace
**   prefix.
**
**   A special case exists for properties that had a prefix starting with
**   "xml". The XML Specification reserves these for future use. mod_dav
**   stores and retrieves them unchanged. The keys for these properties
**   have the form:
**
**     ":" propname
**
**   The propname will contain the prefix and the property name. For
**   example, a key might be ":xmlfoo:name"
**
**   The ":name" style will also be used for properties that do not
**   exist within a namespace.
**
**   The DBM values consist of two null-terminated strings, appended
**   together (the null-terms are retained and stored in the database).
**   The first string is the xml:lang value for the property. An empty
**   string signifies that a lang value was not in context for the value.
**   The second string is the property value itself.
**
**
**   NAMESPACE TABLE
**
**   The namespace table is an array that lists each of the namespaces
**   that are in use by the properties in the given propdb. Each entry
**   in the array is a simple URI.
**
**   For example: http://www.foo.bar/standards/props/
**
**   The prefix used for the property is stripped and the URI for it
**   is entered into the namespace table. Also, any namespaces used
**   within the property value will be entered into the table (and
**   stripped from the child elements).
**
**   The namespaces are stored in the DBM database under the "METADATA" key.
**
**
**   STRIPPING NAMESPACES
**
**   Within the property values, the namespace declarations (xmlns...)
**   are stripped. Each element and attribute will have its prefix removed
**   and a new prefix inserted.
**
**   This must be done so that we can return multiple properties in a
**   PROPFIND which may have (originally) used conflicting prefixes. For
**   that case, we must bind all property value elements to new namespace
**   values.
**
**   This implies that clients must NOT be sensitive to the namespace
**   prefix used for their properties. It WILL change when the properties
**   are returned (we return them as "ns<index>", e.g. "ns5"). Also, the
**   property value can contain ONLY XML elements and CDATA. PI and comment
**   elements will be stripped. CDATA whitespace will be preserved, but
**   whitespace within element tags will be altered. Attribute ordering
**   may be altered. Element and CDATA ordering will be preserved.
**
**
**   ATTRIBUTES ON PROPERTY NAME ELEMENTS
**
**   When getting/setting properties, the XML used looks like:
**
**     <prop>
**       <propname1>value</propname1>
**       <propname2>value</propname1>
**     </prop>
**
**   This implementation (mod_dav) DOES NOT save any attributes that are
**   associated with the <propname1> element. The property value is deemed
**   to be only the contents ("value" in the above example).
**
**   We do store the xml:lang value (if any) that applies to the context
**   of the <propname1> element. Whether the xml:lang attribute is on
**   <propname1> itself, or from a higher level element, we will store it
**   with the property value.
**
**
**   VERSIONING
**
**   The DBM db contains a key named "METADATA" that holds database-level
**   information, such as the namespace table. The record also contains the
**   db's version number as the very first 16-bit value. This first number
**   is actually stored as two single bytes: the first byte is a "major"
**   version number. The second byte is a "minor" number.
**
**   If the major number is not what mod_dav expects, then the db is closed
**   immediately and an error is returned. A minor number change is
**   acceptable -- it is presumed that old/new dav_props.c can deal with
**   the database format. For example, a newer dav_props might update the
**   minor value and append information to the end of the metadata record
**   (which would be ignored by previous versions).
**
**
** ISSUES:
**
**   At the moment, for the dav_get_allprops() and dav_get_props() functions,
**   we must return a set of xmlns: declarations for ALL known namespaces
**   in the file. There isn't a way to filter this because we don't know
**   which are going to be used or not. Examining property names is not
**   sufficient because the property values could use entirely different
**   namespaces.
**
**   ==> we must devise a scheme where we can "garbage collect" the namespace
**       entries from the property database.
*/

#include "apr.h"
#include "apr_strings.h"

#define APR_WANT_STDIO
#define APR_WANT_BYTEFUNC
#include "apr_want.h"

#include "mod_dav.h"

#include "http_log.h"
#include "http_request.h"

/*
** There is some rough support for writable DAV:getcontenttype and
** DAV:getcontentlanguage properties. If this #define is (1), then
** this support is disabled.
**
** We are disabling it because of a lack of support in GET and PUT
** operations. For GET, it would be "expensive" to look for a propdb,
** open it, and attempt to extract the Content-Type and Content-Language
** values for the response.
** (Handling the PUT would not be difficult, though)
*/
#define DAV_DISABLE_WRITABLE_PROPS     1

#define DAV_EMPTY_VALUE                "\0"    /* TWO null terms */

struct dav_propdb {
    apr_pool_t *p;                /* the pool we should use */
    request_rec *r;               /* the request record */

    const dav_resource *resource; /* the target resource */

    int deferred;                 /* open of db has been deferred */
    dav_db *db;                   /* underlying database containing props */

    apr_array_header_t *ns_xlate; /* translation of an elem->ns to URI */
    dav_namespace_map *mapping;   /* namespace mapping */

    dav_lockdb *lockdb;           /* the lock database */

    dav_buffer wb_lock;           /* work buffer for lockdiscovery property */

    /* if we ever run a GET subreq, it will be stored here */
    request_rec *subreq;

    /* hooks we should use for processing (based on the target resource) */
    const dav_hooks_db *db_hooks;
};

/* NOTE: dav_core_props[] and the following enum must stay in sync. */
/* ### move these into a "core" liveprop provider? */
static const char * const dav_core_props[] =
{
    "getcontenttype",
    "getcontentlanguage",
    "lockdiscovery",
    "supportedlock",

    NULL        /* sentinel */
};
enum {
    DAV_PROPID_CORE_getcontenttype = DAV_PROPID_CORE,
    DAV_PROPID_CORE_getcontentlanguage,
    DAV_PROPID_CORE_lockdiscovery,
    DAV_PROPID_CORE_supportedlock,

    DAV_PROPID_CORE_UNKNOWN
};

/*
** This structure is used to track information needed for a rollback.
*/
typedef struct dav_rollback_item {
    /* select one of the two rollback context structures based on the
       value of dav_prop_ctx.is_liveprop */
    dav_deadprop_rollback *deadprop;
    dav_liveprop_rollback *liveprop;

} dav_rollback_item;


static int dav_find_liveprop_provider(dav_propdb *propdb,
                                      const char *ns_uri,
                                      const char *propname,
                                      const dav_hooks_liveprop **provider)
{
    int propid;

    *provider = NULL;

    if (ns_uri == NULL) {
        /* policy: liveprop providers cannot define no-namespace properties */
        return DAV_PROPID_CORE_UNKNOWN;
    }

    /* check liveprop providers first, so they can define core properties */
    propid = dav_run_find_liveprop(propdb->resource, ns_uri, propname,
                                   provider);
    if (propid != 0) {
        return propid;
    }

    /* check for core property */
    if (strcmp(ns_uri, "DAV:") == 0) {
        const char * const *p = dav_core_props;

        for (propid = DAV_PROPID_CORE; *p != NULL; ++p, ++propid)
            if (strcmp(propname, *p) == 0) {
                return propid;
            }
    }

    /* no provider for this property */
    return DAV_PROPID_CORE_UNKNOWN;
}

static void dav_find_liveprop(dav_propdb *propdb, apr_xml_elem *elem)
{
    const char *ns_uri;
    dav_elem_private *priv = elem->priv;
    const dav_hooks_liveprop *hooks;


    if (elem->ns == APR_XML_NS_NONE)
        ns_uri = NULL;
    else if (elem->ns == APR_XML_NS_DAV_ID)
        ns_uri = "DAV:";
    else
        ns_uri = APR_XML_GET_URI_ITEM(propdb->ns_xlate, elem->ns);

    priv->propid = dav_find_liveprop_provider(propdb, ns_uri, elem->name,
                                              &hooks);

    /* ### this test seems redundant... */
    if (priv->propid != DAV_PROPID_CORE_UNKNOWN) {
        priv->provider = hooks;
    }
}

/* is the live property read/write? */
static int dav_rw_liveprop(dav_propdb *propdb, dav_elem_private *priv)
{
    int propid = priv->propid;

    /*
    ** Check the liveprop provider (if this is a provider-defined prop)
    */
    if (priv->provider != NULL) {
        return (*priv->provider->is_writable)(propdb->resource, propid);
    }

    /* these are defined as read-only */
    if (propid == DAV_PROPID_CORE_lockdiscovery
#if DAV_DISABLE_WRITABLE_PROPS
        || propid == DAV_PROPID_CORE_getcontenttype
        || propid == DAV_PROPID_CORE_getcontentlanguage
#endif
        || propid == DAV_PROPID_CORE_supportedlock
        ) {

        return 0;
    }

    /* these are defined as read/write */
    if (propid == DAV_PROPID_CORE_getcontenttype
        || propid == DAV_PROPID_CORE_getcontentlanguage
        || propid == DAV_PROPID_CORE_UNKNOWN) {

        return 1;
    }

    /*
    ** We don't recognize the property, so it must be dead (and writable)
    */
    return 1;
}

/* do a sub-request to fetch properties for the target resource's URI. */
static void dav_do_prop_subreq(dav_propdb *propdb)
{
    /* perform a "GET" on the resource's URI (note that the resource
       may not correspond to the current request!). */
    propdb->subreq = ap_sub_req_lookup_uri(propdb->resource->uri, propdb->r,
                                           NULL);
}

static dav_error * dav_insert_coreprop(dav_propdb *propdb,
                                       int propid, const char *name,
                                       dav_prop_insert what,
                                       apr_text_header *phdr,
                                       dav_prop_insert *inserted)
{
    const char *value = NULL;
    dav_error *err;

    *inserted = DAV_PROP_INSERT_NOTDEF;

    /* fast-path the common case */
    if (propid == DAV_PROPID_CORE_UNKNOWN)
        return NULL;

    switch (propid) {

    case DAV_PROPID_CORE_lockdiscovery:
        if (propdb->lockdb != NULL) {
            dav_lock *locks;

            if ((err = dav_lock_query(propdb->lockdb, propdb->resource,
                                      &locks)) != NULL) {
                return dav_push_error(propdb->p, err->status, 0,
                                      "DAV:lockdiscovery could not be "
                                      "determined due to a problem fetching "
                                      "the locks for this resource.",
                                      err);
            }

            /* fast-path the no-locks case */
            if (locks == NULL) {
                value = "";
            }
            else {
                /*
                ** This may modify the buffer. value may point to
                ** wb_lock.pbuf or a string constant.
                */
                value = dav_lock_get_activelock(propdb->r, locks,
                                                &propdb->wb_lock);

                /* make a copy to isolate it from changes to wb_lock */
                value = apr_pstrdup(propdb->p, propdb->wb_lock.buf);