seclabel.c

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/* -------------------------------------------------------------------------
 *
 * seclabel.c
 *    routines to support security label feature.
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * -------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/htup_details.h"
#include "access/relation.h"
#include "access/table.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/pg_seclabel.h"
#include "catalog/pg_shseclabel.h"
#include "commands/seclabel.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/memutils.h"
#include "utils/rel.h"

typedef struct
{
    const char *provider_name;
    check_object_relabel_type hook;
} LabelProvider;

static List *label_provider_list = NIL;

/*
 * ExecSecLabelStmt --
 *
 * Apply a security label to a database object.
 *
 * Returns the ObjectAddress of the object to which the policy was applied.
 */
ObjectAddress
ExecSecLabelStmt(SecLabelStmt *stmt)
{
    LabelProvider *provider = NULL;
    ObjectAddress address;
    Relation    relation;
    ListCell   *lc;

    /*
     * Find the named label provider, or if none specified, check whether
     * there's exactly one, and if so use it.
     */
    if (stmt->provider == NULL)
    {
        if (label_provider_list == NIL)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("no security label providers have been loaded")));
        if (list_length(label_provider_list) != 1)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("must specify provider when multiple security label providers have been loaded")));
        provider = (LabelProvider *) linitial(label_provider_list);
    }
    else
    {
        foreach(lc, label_provider_list)
        {
            LabelProvider *lp = lfirst(lc);

            if (strcmp(stmt->provider, lp->provider_name) == 0)
            {
                provider = lp;
                break;
            }
        }
        if (provider == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("security label provider \"%s\" is not loaded",
                            stmt->provider)));
    }

    /*
     * Translate the parser representation which identifies this object into
     * an ObjectAddress. get_object_address() will throw an error if the
     * object does not exist, and will also acquire a lock on the target to
     * guard against concurrent modifications.
     */
    address = get_object_address(stmt->objtype, stmt->object,
                                 &relation, ShareUpdateExclusiveLock, false);

    /* Require ownership of the target object. */
    check_object_ownership(GetUserId(), stmt->objtype, address,
                           stmt->object, relation);

    /* Perform other integrity checks as needed. */
    switch (stmt->objtype)
    {
        case OBJECT_COLUMN:

            /*
             * Allow security labels only on columns of tables, views,
             * materialized views, composite types, and foreign tables (which
             * are the only relkinds for which pg_dump will dump labels).
             */
            if (relation->rd_rel->relkind != RELKIND_RELATION &&
                relation->rd_rel->relkind != RELKIND_VIEW &&
                relation->rd_rel->relkind != RELKIND_MATVIEW &&
                relation->rd_rel->relkind != RELKIND_COMPOSITE_TYPE &&
                relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE &&
                relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
                ereport(ERROR,
                        (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                         errmsg("\"%s\" is not a table, view, materialized view, composite type, or foreign table",
                                RelationGetRelationName(relation))));
            break;
        default:
            break;
    }

    /* Provider gets control here, may throw ERROR to veto new label. */
    provider->hook(&address, stmt->label);

    /* Apply new label. */
    SetSecurityLabel(&address, provider->provider_name, stmt->label);

    /*
     * If get_object_address() opened the relation for us, we close it to keep
     * the reference count correct - but we retain any locks acquired by
     * get_object_address() until commit time, to guard against concurrent
     * activity.
     */
    if (relation != NULL)
        relation_close(relation, NoLock);

    return address;
}

/*
 * GetSharedSecurityLabel returns the security label for a shared object for
 * a given provider, or NULL if there is no such label.
 */
static char *
GetSharedSecurityLabel(const ObjectAddress *object, const char *provider)
{
    Relation    pg_shseclabel;
    ScanKeyData keys[3];
    SysScanDesc scan;
    HeapTuple   tuple;
    Datum       datum;
    bool        isnull;
    char       *seclabel = NULL;

    ScanKeyInit(&keys[0],
                Anum_pg_shseclabel_objoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->objectId));
    ScanKeyInit(&keys[1],
                Anum_pg_shseclabel_classoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->classId));
    ScanKeyInit(&keys[2],
                Anum_pg_shseclabel_provider,
                BTEqualStrategyNumber, F_TEXTEQ,
                CStringGetTextDatum(provider));

    pg_shseclabel = table_open(SharedSecLabelRelationId, AccessShareLock);

    scan = systable_beginscan(pg_shseclabel, SharedSecLabelObjectIndexId, true,
                              NULL, 3, keys);

    tuple = systable_getnext(scan);
    if (HeapTupleIsValid(tuple))
    {
        datum = heap_getattr(tuple, Anum_pg_shseclabel_label,
                             RelationGetDescr(pg_shseclabel), &isnull);
        if (!isnull)
            seclabel = TextDatumGetCString(datum);
    }
    systable_endscan(scan);

    table_close(pg_shseclabel, AccessShareLock);

    return seclabel;
}

/*
 * GetSecurityLabel returns the security label for a shared or database object
 * for a given provider, or NULL if there is no such label.
 */
char *
GetSecurityLabel(const ObjectAddress *object, const char *provider)
{
    Relation    pg_seclabel;
    ScanKeyData keys[4];
    SysScanDesc scan;
    HeapTuple   tuple;
    Datum       datum;
    bool        isnull;
    char       *seclabel = NULL;

    /* Shared objects have their own security label catalog. */
    if (IsSharedRelation(object->classId))
        return GetSharedSecurityLabel(object, provider);

    /* Must be an unshared object, so examine pg_seclabel. */
    ScanKeyInit(&keys[0],
                Anum_pg_seclabel_objoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->objectId));
    ScanKeyInit(&keys[1],
                Anum_pg_seclabel_classoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->classId));
    ScanKeyInit(&keys[2],
                Anum_pg_seclabel_objsubid,
                BTEqualStrategyNumber, F_INT4EQ,
                Int32GetDatum(object->objectSubId));
    ScanKeyInit(&keys[3],
                Anum_pg_seclabel_provider,
                BTEqualStrategyNumber, F_TEXTEQ,
                CStringGetTextDatum(provider));

    pg_seclabel = table_open(SecLabelRelationId, AccessShareLock);

    scan = systable_beginscan(pg_seclabel, SecLabelObjectIndexId, true,
                              NULL, 4, keys);

    tuple = systable_getnext(scan);
    if (HeapTupleIsValid(tuple))
    {
        datum = heap_getattr(tuple, Anum_pg_seclabel_label,
                             RelationGetDescr(pg_seclabel), &isnull);
        if (!isnull)
            seclabel = TextDatumGetCString(datum);
    }
    systable_endscan(scan);

    table_close(pg_seclabel, AccessShareLock);

    return seclabel;
}

/*
 * SetSharedSecurityLabel is a helper function of SetSecurityLabel to
 * handle shared database objects.
 */
static void
SetSharedSecurityLabel(const ObjectAddress *object,
                       const char *provider, const char *label)
{
    Relation    pg_shseclabel;
    ScanKeyData keys[4];
    SysScanDesc scan;
    HeapTuple   oldtup;
    HeapTuple   newtup = NULL;
    Datum       values[Natts_pg_shseclabel];
    bool        nulls[Natts_pg_shseclabel];
    bool        replaces[Natts_pg_shseclabel];

    /* Prepare to form or update a tuple, if necessary. */
    memset(nulls, false, sizeof(nulls));
    memset(replaces, false, sizeof(replaces));
    values[Anum_pg_shseclabel_objoid - 1] = ObjectIdGetDatum(object->objectId);
    values[Anum_pg_shseclabel_classoid - 1] = ObjectIdGetDatum(object->classId);
    values[Anum_pg_shseclabel_provider - 1] = CStringGetTextDatum(provider);
    if (label != NULL)
        values[Anum_pg_shseclabel_label - 1] = CStringGetTextDatum(label);

    /* Use the index to search for a matching old tuple */
    ScanKeyInit(&keys[0],
                Anum_pg_shseclabel_objoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->objectId));
    ScanKeyInit(&keys[1],
                Anum_pg_shseclabel_classoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->classId));
    ScanKeyInit(&keys[2],
                Anum_pg_shseclabel_provider,
                BTEqualStrategyNumber, F_TEXTEQ,
                CStringGetTextDatum(provider));

    pg_shseclabel = table_open(SharedSecLabelRelationId, RowExclusiveLock);

    scan = systable_beginscan(pg_shseclabel, SharedSecLabelObjectIndexId, true,
                              NULL, 3, keys);

    oldtup = systable_getnext(scan);
    if (HeapTupleIsValid(oldtup))
    {
        if (label == NULL)
            CatalogTupleDelete(pg_shseclabel, &oldtup->t_self);
        else
        {
            replaces[Anum_pg_shseclabel_label - 1] = true;
            newtup = heap_modify_tuple(oldtup, RelationGetDescr(pg_shseclabel),
                                       values, nulls, replaces);
            CatalogTupleUpdate(pg_shseclabel, &oldtup->t_self, newtup);
        }
    }
    systable_endscan(scan);

    /* If we didn't find an old tuple, insert a new one */
    if (newtup == NULL && label != NULL)
    {
        newtup = heap_form_tuple(RelationGetDescr(pg_shseclabel),
                                 values, nulls);
        CatalogTupleInsert(pg_shseclabel, newtup);
    }

    if (newtup != NULL)
        heap_freetuple(newtup);

    table_close(pg_shseclabel, RowExclusiveLock);
}

/*
 * SetSecurityLabel attempts to set the security label for the specified
 * provider on the specified object to the given value.  NULL means that any
 * existing label should be deleted.
 */
void
SetSecurityLabel(const ObjectAddress *object,
                 const char *provider, const char *label)
{
    Relation    pg_seclabel;
    ScanKeyData keys[4];
    SysScanDesc scan;
    HeapTuple   oldtup;
    HeapTuple   newtup = NULL;
    Datum       values[Natts_pg_seclabel];
    bool        nulls[Natts_pg_seclabel];
    bool        replaces[Natts_pg_seclabel];

    /* Shared objects have their own security label catalog. */
    if (IsSharedRelation(object->classId))
    {
        SetSharedSecurityLabel(object, provider, label);
        return;
    }

    /* Prepare to form or update a tuple, if necessary. */
    memset(nulls, false, sizeof(nulls));
    memset(replaces, false, sizeof(replaces));
    values[Anum_pg_seclabel_objoid - 1] = ObjectIdGetDatum(object->objectId);
    values[Anum_pg_seclabel_classoid - 1] = ObjectIdGetDatum(object->classId);
    values[Anum_pg_seclabel_objsubid - 1] = Int32GetDatum(object->objectSubId);
    values[Anum_pg_seclabel_provider - 1] = CStringGetTextDatum(provider);
    if (label != NULL)
        values[Anum_pg_seclabel_label - 1] = CStringGetTextDatum(label);

    /* Use the index to search for a matching old tuple */
    ScanKeyInit(&keys[0],
                Anum_pg_seclabel_objoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->objectId));
    ScanKeyInit(&keys[1],
                Anum_pg_seclabel_classoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->classId));
    ScanKeyInit(&keys[2],
                Anum_pg_seclabel_objsubid,
                BTEqualStrategyNumber, F_INT4EQ,
                Int32GetDatum(object->objectSubId));
    ScanKeyInit(&keys[3],
                Anum_pg_seclabel_provider,
                BTEqualStrategyNumber, F_TEXTEQ,
                CStringGetTextDatum(provider));

    pg_seclabel = table_open(SecLabelRelationId, RowExclusiveLock);

    scan = systable_beginscan(pg_seclabel, SecLabelObjectIndexId, true,
                              NULL, 4, keys);

    oldtup = systable_getnext(scan);
    if (HeapTupleIsValid(oldtup))
    {
        if (label == NULL)
            CatalogTupleDelete(pg_seclabel, &oldtup->t_self);
        else
        {
            replaces[Anum_pg_seclabel_label - 1] = true;
            newtup = heap_modify_tuple(oldtup, RelationGetDescr(pg_seclabel),
                                       values, nulls, replaces);
            CatalogTupleUpdate(pg_seclabel, &oldtup->t_self, newtup);
        }
    }
    systable_endscan(scan);

    /* If we didn't find an old tuple, insert a new one */
    if (newtup == NULL && label != NULL)
    {
        newtup = heap_form_tuple(RelationGetDescr(pg_seclabel),
                                 values, nulls);
        CatalogTupleInsert(pg_seclabel, newtup);
    }

    /* Update indexes, if necessary */
    if (newtup != NULL)
        heap_freetuple(newtup);

    table_close(pg_seclabel, RowExclusiveLock);
}

/*
 * DeleteSharedSecurityLabel is a helper function of DeleteSecurityLabel
 * to handle shared database objects.
 */
void
DeleteSharedSecurityLabel(Oid objectId, Oid classId)
{
    Relation    pg_shseclabel;
    ScanKeyData skey[2];
    SysScanDesc scan;
    HeapTuple   oldtup;

    ScanKeyInit(&skey[0],
                Anum_pg_shseclabel_objoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(objectId));
    ScanKeyInit(&skey[1],
                Anum_pg_shseclabel_classoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(classId));

    pg_shseclabel = table_open(SharedSecLabelRelationId, RowExclusiveLock);

    scan = systable_beginscan(pg_shseclabel, SharedSecLabelObjectIndexId, true,
                              NULL, 2, skey);
    while (HeapTupleIsValid(oldtup = systable_getnext(scan)))
        CatalogTupleDelete(pg_shseclabel, &oldtup->t_self);
    systable_endscan(scan);

    table_close(pg_shseclabel, RowExclusiveLock);
}

/*
 * DeleteSecurityLabel removes all security labels for an object (and any
 * sub-objects, if applicable).
 */
void
DeleteSecurityLabel(const ObjectAddress *object)
{
    Relation    pg_seclabel;
    ScanKeyData skey[3];
    SysScanDesc scan;
    HeapTuple   oldtup;
    int         nkeys;

    /* Shared objects have their own security label catalog. */
    if (IsSharedRelation(object->classId))
    {
        Assert(object->objectSubId == 0);
        DeleteSharedSecurityLabel(object->objectId, object->classId);
        return;
    }

    ScanKeyInit(&skey[0],
                Anum_pg_seclabel_objoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->objectId));
    ScanKeyInit(&skey[1],
                Anum_pg_seclabel_classoid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(object->classId));
    if (object->objectSubId != 0)
    {
        ScanKeyInit(&skey[2],
                    Anum_pg_seclabel_objsubid,
                    BTEqualStrategyNumber, F_INT4EQ,
                    Int32GetDatum(object->objectSubId));
        nkeys = 3;
    }
    else
        nkeys = 2;

    pg_seclabel = table_open(SecLabelRelationId, RowExclusiveLock);

    scan = systable_beginscan(pg_seclabel, SecLabelObjectIndexId, true,
                              NULL, nkeys, skey);
    while (HeapTupleIsValid(oldtup = systable_getnext(scan)))
        CatalogTupleDelete(pg_seclabel, &oldtup->t_self);
    systable_endscan(scan);

    table_close(pg_seclabel, RowExclusiveLock);
}

void
register_label_provider(const char *provider_name, check_object_relabel_type hook)
{
    LabelProvider *provider;
    MemoryContext oldcxt;

    oldcxt = MemoryContextSwitchTo(TopMemoryContext);
    provider = palloc(sizeof(LabelProvider));
    provider->provider_name = pstrdup(provider_name);
    provider->hook = hook;
    label_provider_list = lappend(label_provider_list, provider);
    MemoryContextSwitchTo(oldcxt);
}