|From:||Ilir Gashi <I(dot)Gashi(at)city(dot)ac(dot)uk>|
|To:||Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>|
|Subject:||Re: Grant Update (Possible bug)?|
|Views:||Raw Message | Whole Thread | Download mbox|
On Jul 2 2004, Tom Lane wrote:
> Ilir Gashi <I(dot)Gashi(at)city(dot)ac(dot)uk> writes:
> > This is a another bug reported for the Firebird 1.0 server. I
> > subsequently ran it in PostgreSQL 7.2, Oracle 8.0.5 anf MSSQL 7.
> > Reproducible script:
> > Connect as pgsql:
> > CREATE TABLE TEST(ID INTEGER,NAME VARCHAR(50));
> > INSERT INTO TEST (ID) VALUES (1);
> > GRANT UPDATE ON TEST TO TESTUSER;
> > Connect as TestUser;
> > UPDATE TEST SET NAME='TEST' WHERE ID=1;
> > ERROR: test: Permission denied.
> > UPDATE TEST SET NAME='TEST';
> > Executes successfully.
> This is not a bug. That UPDATE requires SELECT permission because it
> makes use of the ID field in the where clause. If you grant someone
> UPDATE but not SELECT, presumably you want them to be able to insert
> data but not learn anything about what is in the table. If we allowed
> such commands then something like
> UPDATE TEST SET NAME = NAME WHERE ID = 1
> could be used to determine whether the table contains a row with ID=1
> (by inspecting the reported row count). So it would be a security flaw.
> The SQL specification also requires this behavior. In SQL92 the Access
> Rules for <column reference> say
> 1) The applicable privileges shall include SELECT for T if CR is
> contained in any of:
> a) a <search condition> immediately contained in a <delete
> statement: searched> or an <update statement: searched>; or
> b) a <value expression> immediately contained in an <update
> > So the user can update the whole table but not specific columns. Is
> > this a bug or as specified (I read briefly the Reference Guide and I
> > didn't see this highlited anywhere, but I may have missed it.).
> > Firebird and MSSQL have the same behaviour as PostgreSQL (Firebird have
> > acknowledged this as a bug, I haven't checked on MSSQL website yet.)
> It's not a bug. Please withdraw the complaint against Firebird.
> > In Oracle 8.0.5 both updates execute sucessfully.
> Oracle is a very poor reference for SQL-spec-compliant behavior :-(
> regards, tom lane
Thanks for the quick reply. I also suspected that it was not a bug, but was
confused by The Firebird bug-tracker at SourceForge who had marked it as an
'Initial bug', and became even more confused from the behaviour of Oracle.
Thanks for the clarification.
Centre for Software Reliability
Northampton Square, London EC1V 0HB
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