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Add a security_barrier option for views.
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When a view is marked as a security barrier, it will not be pulled up
into the containing query, and no quals will be pushed down into it,
so that no function or operator chosen by the user can be applied to
rows not exposed by the view.  Views not configured with this
option cannot provide robust row-level security, but will perform far
better.

Patch by KaiGai Kohei; original problem report by Heikki Linnakangas
(in October 2009!).  Review (in earlier versions) by Noah Misch and
others.  Design advice by Tom Lane and myself.  Further review and
cleanup by me.
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@robertmhaas
robertmhaas committed Dec 22, 2011
1 parent f90dd28 commit 0e4611c
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Showing 22 changed files with 300 additions and 35 deletions.
20 changes: 20 additions & 0 deletions doc/src/sgml/ref/alter_view.sgml
View file
Expand Up @@ -26,6 +26,8 @@ ALTER VIEW <replaceable class="parameter">name</replaceable> ALTER [ COLUMN ] <r
ALTER VIEW <replaceable class="parameter">name</replaceable> OWNER TO <replaceable class="PARAMETER">new_owner</replaceable>
ALTER VIEW <replaceable class="parameter">name</replaceable> RENAME TO <replaceable class="parameter">new_name</replaceable>
ALTER VIEW <replaceable class="parameter">name</replaceable> SET SCHEMA <replaceable class="parameter">new_schema</replaceable>
ALTER VIEW <replaceable class="parameter">name</replaceable> SET ( <replaceable class="parameter">view_option_name</replaceable> [= <replaceable class="parameter">view_option_value</replaceable>] [, ... ] )
ALTER VIEW <replaceable class="parameter">name</replaceable> RESET ( <replaceable class="parameter">view_option_name</replaceable> [, ... ] )
</synopsis>
</refsynopsisdiv>

Expand Down Expand Up @@ -102,6 +104,24 @@ ALTER VIEW <replaceable class="parameter">name</replaceable> SET SCHEMA <replace
</para>
</listitem>
</varlistentry>

<varlistentry>
<term><replaceable class="parameter">view_option_name</replaceable></term>
<listitem>
<para>
The name of a view option to be set or reset.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term><replaceable class="parameter">view_option_name</replaceable></term>
<listitem>
<para>
The new value for a view option.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>

Expand Down
13 changes: 13 additions & 0 deletions doc/src/sgml/ref/create_view.sgml
View file
Expand Up @@ -22,6 +22,7 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW <replaceable class="PARAMETER">name</replaceable> [ ( <replaceable class="PARAMETER">column_name</replaceable> [, ...] ) ]
[ WITH ( <replaceable class="PARAMETER">view_option_name</replaceable> [= <replaceable class="PARAMETER">view_option_value</replaceable>] [, ... ] ) ]
AS <replaceable class="PARAMETER">query</replaceable>
</synopsis>
</refsynopsisdiv>
Expand Down Expand Up @@ -98,6 +99,18 @@ CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW <replaceable class="PARAMETER">n
</listitem>
</varlistentry>

<varlistentry>
<term><literal>WITH ( <replaceable class="PARAMETER">view_option_name</replaceable> [= <replaceable class="PARAMETER">view_option_value</replaceable>] [, ... ] )</literal></term>
<listitem>
<para>
This clause specifies optional parameters for a view; currently, the
only suppored parameter name is <literal>security_barrier</literal>,
which should be enabled when a view is intended to provide row-level
security. See <xref linkend="rules-privileges"> for full details.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term><replaceable class="parameter">query</replaceable></term>
<listitem>
Expand Down
39 changes: 37 additions & 2 deletions doc/src/sgml/rules.sgml
View file
Expand Up @@ -1822,8 +1822,9 @@ GRANT SELECT ON phone_number TO secretary;
<para>
Note that while views can be used to hide the contents of certain
columns using the technique shown above, they cannot be used to reliably
conceal the data in unseen rows. For example, the following view is
insecure:
conceal the data in unseen rows unless the
<literal>security_barrier</literal> flag has been set. For example,
the following view is insecure:
<programlisting>
CREATE VIEW phone_number AS
SELECT person, phone FROM phone_data WHERE phone NOT LIKE '412%';
Expand Down Expand Up @@ -1870,6 +1871,40 @@ SELECT * FROM phone_number WHERE tricky(person, phone);
which references <literal>shoelace_log</> is an unqualified
<literal>INSERT</>. This might not be true in more complex scenarios.
</para>

<para>
When it is necessary for a view to provide row-level security, the
<literal>security_barrier</literal> attribute should be applied to
the view. This prevents maliciously-chosen functions and operators from
being invoked on rows until afterthe view has done its work. For
example, if the view shown above had been created like this, it would
be secure:
<programlisting>
CREATE VIEW phone_number WITH (security_barrier) AS
SELECT person, phone FROM phone_data WHERE phone NOT LIKE '412%';
</programlisting>
Views created with the <literal>security_barrier</literal> may perform
far worse than views created without this option. In general, there is
no way to avoid this: the fastest possible plan must be rejected
if it may compromise security. For this reason, this option is not
enabled by default.
</para>

<para>
It is important to understand that even a view created with the
<literal>security_barrier</literal> option is intended to be secure only
in the limited sense that the contents of the invisible tuples will not
passed to possibly-insecure functions. The user may well have other means
of making inferences about the unseen data; for example, they can see the
query plan using <command>EXPLAIN</command>, or measure the runtime of
queries against the view. A malicious attacker might be able to infer
something about the amount of unseen data, or even gain some information
about the data distribution or most common values (since these things may
affect the runtime of the plan; or even, since they are also reflected in
the optimizer statistics, the choice of plan). If these types of "covert
channel" attacks are of concern, it is probably unwise to grant any access
to the data at all.
</para>
</sect1>

<sect1 id="rules-status">
Expand Down
17 changes: 15 additions & 2 deletions src/backend/access/common/reloptions.c
View file
Expand Up @@ -67,6 +67,14 @@ static relopt_bool boolRelOpts[] =
},
true
},
{
{
"security_barrier",
"View acts as a row security barrier",
RELOPT_KIND_VIEW
},
false
},
/* list terminator */
{{NULL}}
};
Expand Down Expand Up @@ -781,6 +789,7 @@ extractRelOptions(HeapTuple tuple, TupleDesc tupdesc, Oid amoptions)
{
case RELKIND_RELATION:
case RELKIND_TOASTVALUE:
case RELKIND_VIEW:
case RELKIND_UNCATALOGED:
options = heap_reloptions(classForm->relkind, datum, false);
break;
Expand Down Expand Up @@ -1139,7 +1148,9 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
{"autovacuum_vacuum_scale_factor", RELOPT_TYPE_REAL,
offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, vacuum_scale_factor)},
{"autovacuum_analyze_scale_factor", RELOPT_TYPE_REAL,
offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, analyze_scale_factor)}
offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, analyze_scale_factor)},
{"security_barrier", RELOPT_TYPE_BOOL,
offsetof(StdRdOptions, security_barrier)},
};

options = parseRelOptions(reloptions, validate, kind, &numoptions);
Expand All @@ -1159,7 +1170,7 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
}

/*
* Parse options for heaps and toast tables.
* Parse options for heaps, views and toast tables.
*/
bytea *
heap_reloptions(char relkind, Datum reloptions, bool validate)
Expand All @@ -1181,6 +1192,8 @@ heap_reloptions(char relkind, Datum reloptions, bool validate)
return (bytea *) rdopts;
case RELKIND_RELATION:
return default_reloptions(reloptions, validate, RELOPT_KIND_HEAP);
case RELKIND_VIEW:
return default_reloptions(reloptions, validate, RELOPT_KIND_VIEW);
default:
/* other relkinds are not supported */
return NULL;
Expand Down
66 changes: 50 additions & 16 deletions src/backend/commands/tablecmds.c
View file
Expand Up @@ -366,7 +366,9 @@ static void ATExecDropCluster(Relation rel, LOCKMODE lockmode);
static void ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel,
char *tablespacename, LOCKMODE lockmode);
static void ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode);
static void ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode);
static void ATExecSetRelOptions(Relation rel, List *defList,
AlterTableType operation,
LOCKMODE lockmode);
static void ATExecEnableDisableTrigger(Relation rel, char *trigname,
char fires_when, bool skip_system, LOCKMODE lockmode);
static void ATExecEnableDisableRule(Relation rel, char *rulename,
Expand Down Expand Up @@ -2866,6 +2868,7 @@ AlterTableGetLockLevel(List *cmds)
case AT_DropCluster:
case AT_SetRelOptions:
case AT_ResetRelOptions:
case AT_ReplaceRelOptions:
case AT_SetOptions:
case AT_ResetOptions:
case AT_SetStorage:
Expand Down Expand Up @@ -3094,8 +3097,9 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
pass = AT_PASS_MISC; /* doesn't actually matter */
break;
case AT_SetRelOptions: /* SET (...) */
case AT_ResetRelOptions: /* RESET (...) */
ATSimplePermissions(rel, ATT_TABLE | ATT_INDEX);
case AT_ResetRelOptions: /* RESET (...) */
case AT_ReplaceRelOptions: /* reset them all, then set just these */
ATSimplePermissions(rel, ATT_TABLE | ATT_INDEX | ATT_VIEW);
/* This command never recurses */
/* No command-specific prep needed */
pass = AT_PASS_MISC;
Expand Down Expand Up @@ -3338,12 +3342,10 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
*/
break;
case AT_SetRelOptions: /* SET (...) */
ATExecSetRelOptions(rel, (List *) cmd->def, false, lockmode);
break;
case AT_ResetRelOptions: /* RESET (...) */
ATExecSetRelOptions(rel, (List *) cmd->def, true, lockmode);
case AT_ReplaceRelOptions: /* replace entire option list */
ATExecSetRelOptions(rel, (List *) cmd->def, cmd->subtype, lockmode);
break;

case AT_EnableTrig: /* ENABLE TRIGGER name */
ATExecEnableDisableTrigger(rel, cmd->name,
TRIGGER_FIRES_ON_ORIGIN, false, lockmode);
Expand Down Expand Up @@ -8271,10 +8273,11 @@ ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel, char *tablespacename, L
}

/*
* ALTER TABLE/INDEX SET (...) or RESET (...)
* Set, reset, or replace reloptions.
*/
static void
ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode)
ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
LOCKMODE lockmode)
{
Oid relid;
Relation pgclass;
Expand All @@ -8288,28 +8291,44 @@ ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode
bool repl_repl[Natts_pg_class];
static char *validnsps[] = HEAP_RELOPT_NAMESPACES;

if (defList == NIL)
if (defList == NIL && operation != AT_ReplaceRelOptions)
return; /* nothing to do */

pgclass = heap_open(RelationRelationId, RowExclusiveLock);

/* Get the old reloptions */
/* Fetch heap tuple */
relid = RelationGetRelid(rel);
tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", relid);

datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions, &isnull);
if (operation == AT_ReplaceRelOptions)
{
/*
* If we're supposed to replace the reloptions list, we just pretend
* there were none before.
*/
datum = (Datum) 0;
isnull = true;
}
else
{
/* Get the old reloptions */
datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
&isnull);
}

/* Generate new proposed reloptions (text array) */
newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
defList, NULL, validnsps, false, isReset);
defList, NULL, validnsps, false,
operation == AT_ResetRelOptions);

/* Validate */
switch (rel->rd_rel->relkind)
{
case RELKIND_RELATION:
case RELKIND_TOASTVALUE:
case RELKIND_VIEW:
(void) heap_reloptions(rel->rd_rel->relkind, newOptions, true);
break;
case RELKIND_INDEX:
Expand Down Expand Up @@ -8357,15 +8376,30 @@ ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode

toastrel = heap_open(toastid, lockmode);

/* Get the old reloptions */
/* Fetch heap tuple */
tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(toastid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", toastid);

datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions, &isnull);
if (operation == AT_ReplaceRelOptions)
{
/*
* If we're supposed to replace the reloptions list, we just
* pretend there were none before.
*/
datum = (Datum) 0;
isnull = true;
}
else
{
/* Get the old reloptions */
datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
&isnull);
}

newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
defList, "toast", validnsps, false, isReset);
defList, "toast", validnsps, false,
operation == AT_ResetRelOptions);

(void) heap_reloptions(RELKIND_TOASTVALUE, newOptions, true);

Expand Down
26 changes: 19 additions & 7 deletions src/backend/commands/view.c
View file
Expand Up @@ -32,6 +32,7 @@
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"


static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc);
Expand Down Expand Up @@ -98,7 +99,7 @@ isViewOnTempTable_walker(Node *node, void *context)
*/
static Oid
DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
Oid namespaceId)
Oid namespaceId, List *options)
{
Oid viewOid;
CreateStmt *createStmt = makeNode(CreateStmt);
Expand Down Expand Up @@ -166,6 +167,8 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
{
Relation rel;
TupleDesc descriptor;
List *atcmds = NIL;
AlterTableCmd *atcmd;

/*
* Yes. Get exclusive lock on the existing view ...
Expand Down Expand Up @@ -203,21 +206,27 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
descriptor = BuildDescForRelation(attrList);
checkViewTupleDesc(descriptor, rel->rd_att);

/*
* The new options list replaces the existing options list, even
* if it's empty.
*/
atcmd = makeNode(AlterTableCmd);
atcmd->subtype = AT_ReplaceRelOptions;
atcmd->def = (Node *) options;
atcmds = lappend(atcmds, atcmd);

/*
* If new attributes have been added, we must add pg_attribute entries
* for them. It is convenient (although overkill) to use the ALTER
* TABLE ADD COLUMN infrastructure for this.
*/
if (list_length(attrList) > rel->rd_att->natts)
{
List *atcmds = NIL;
ListCell *c;
int skip = rel->rd_att->natts;

foreach(c, attrList)
{
AlterTableCmd *atcmd;

if (skip > 0)
{
skip--;
Expand All @@ -228,9 +237,11 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
atcmd->def = (Node *) lfirst(c);
atcmds = lappend(atcmds, atcmd);
}
AlterTableInternal(viewOid, atcmds, true);
}

/* OK, let's do it. */
AlterTableInternal(viewOid, atcmds, true);

/*
* Seems okay, so return the OID of the pre-existing view.
*/
Expand All @@ -250,7 +261,8 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
createStmt->tableElts = attrList;
createStmt->inhRelations = NIL;
createStmt->constraints = NIL;
createStmt->options = list_make1(defWithOids(false));
createStmt->options = options;
createStmt->options = lappend(options, defWithOids(false));
createStmt->oncommit = ONCOMMIT_NOOP;
createStmt->tablespacename = NULL;
createStmt->if_not_exists = false;
Expand Down Expand Up @@ -513,7 +525,7 @@ DefineView(ViewStmt *stmt, const char *queryString)
* aborted.
*/
viewOid = DefineVirtualRelation(view, viewParse->targetList,
stmt->replace, namespaceId);
stmt->replace, namespaceId, stmt->options);

/*
* The relation we have just created is not visible to any other commands
Expand Down

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