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Require superuser privilege to create a binary-compatible cast, per

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discussion some weeks ago.  Also, add a check that two types to be
binary-equivalenced match as to typlen, typbyval, and typalign; if
they don't then it's surely a mistake to equivalence them.
This commit is contained in:
Tom Lane 2002-10-04 22:08:44 +00:00
parent 04c57d68ce
commit d2db166c75
2 changed files with 33 additions and 5 deletions
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9
doc/src/sgml/ref/create_cast.sgml
View File

@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.5 2002/09/18 21:35:20 tgl Exp $ --> <!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.6 2002/10/04 22:08:44 tgl Exp $ -->
<refentry id="SQL-CREATECAST"> <refentry id="SQL-CREATECAST">
<refmeta> <refmeta>
@ -81,10 +81,9 @@ SELECT 'The time is ' || now();
</programlisting> </programlisting>
will be allowed only if the cast from type <type>timestamp</> to will be allowed only if the cast from type <type>timestamp</> to
<type>text</type> is marked <literal>AS IMPLICIT</>. Otherwise it <type>text</type> is marked <literal>AS IMPLICIT</>. Otherwise it
will be necessary to write one of will be necessary to write the cast explicitly, for example
<programlisting> <programlisting>
SELECT 'The time is ' || CAST(now() AS text); SELECT 'The time is ' || CAST(now() AS text);
SELECT 'The time is ' || now()::text;
</programlisting> </programlisting>
(We generally use the term <firstterm>implicit (We generally use the term <firstterm>implicit
cast</firstterm> to describe this kind of cast.) cast</firstterm> to describe this kind of cast.)
@ -107,7 +106,9 @@ SELECT 'The time is ' || now()::text;
<para> <para>
To be able to create a cast, you must own the source or the target To be able to create a cast, you must own the source or the target
data type. data type. To create a binary-compatible cast, you must be superuser
(this restriction is made because an erroneous binary-compatible cast
conversion can easily crash the server).
</para> </para>
<variablelist> <variablelist>

29
src/backend/commands/functioncmds.c
View File

@ -9,7 +9,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/functioncmds.c,v 1.22 2002/09/21 18:39:25 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/commands/functioncmds.c,v 1.23 2002/10/04 22:08:44 tgl Exp $
* *
* DESCRIPTION * DESCRIPTION
* These routines take the parse tree and pick out the * These routines take the parse tree and pick out the
@ -756,8 +756,35 @@ CreateCast(CreateCastStmt *stmt)
} }
else else
{ {
int16 typ1len;
int16 typ2len;
bool typ1byval;
bool typ2byval;
char typ1align;
char typ2align;
/* indicates binary coercibility */ /* indicates binary coercibility */
funcid = InvalidOid; funcid = InvalidOid;
/*
* Must be superuser to create binary-compatible casts, since
* erroneous casts can easily crash the backend.
*/
if (!superuser())
elog(ERROR, "Must be superuser to create a cast WITHOUT FUNCTION");
/*
* Also, insist that the types match as to size, alignment, and
* pass-by-value attributes; this provides at least a crude check
* that they have similar representations. A pair of types that
* fail this test should certainly not be equated.
*/
get_typlenbyvalalign(sourcetypeid, &typ1len, &typ1byval, &typ1align);
get_typlenbyvalalign(targettypeid, &typ2len, &typ2byval, &typ2align);
if (typ1len != typ2len ||
typ1byval != typ2byval ||
typ1align != typ2align)
elog(ERROR, "source and target datatypes are not physically compatible");
} }
/* convert CoercionContext enum to char value for castcontext */ /* convert CoercionContext enum to char value for castcontext */