vulnerability of COPY command

Hello

2010/5/30 Dennis Gearon <gearond@sbcglobal.net>:

I'm trying to build a way to bulk load from a script to a Dbase, postgres.

Using single, parameterized statements is a pretty good defense against SQL injection, so I use Symfony as the main user input.

But for this bulk loading, it's tooooooo slow.

Maybe you have enabled autocomit - then it can be very very slow.

If I build a text based, COPY file for bulk purposes, to be input via the command line, is Postgres vulnerable to SQL injection from that?

SQL database cannot be injected via NON SQL statemenst like COPY.

Regards

Pavel Stehule

i have mixed feelings about parameterised statements.

On the one hand a parameterised statement would be more difficult for a Wireshark criminal to insert their own c**p into a database because they would have to know the schema a-priori for example they would have to know the names of the database, table and the datatypes of these 2 statements
Insert DateField1 INTO DateTable VALUES(1) would gack as 1 is not a valid date

Insert NumericField1 INTO NumericTable VALUES('A') would gack as well as A is not a valid number

But thats only one line of defence..Struts..JSF and other Frameworks have field validators so a good design would involve 2 tiered defence

1)The web folks would put some kind of JS function to disallow client know from enetering a invalid date

2)The back-end folks (me) would validate Database params in the servlet or the DTO as it makes its way to the VO and before any of the offending values get into the database

The net effect is wireshark criminals are succeeding in making everyone's lives a living hell..the least we can do is take their pitchfork away!

Martin Gainty
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Date: Sat, 29 May 2010 22:41:04 -0700
From: gearond@sbcglobal.net
Subject: [GENERAL] vulnerability of COPY command
To: pgsql-general@postgresql.org

I'm trying to build a way to bulk load from a script to a Dbase, postgres.

Using single, parameterized statements is a pretty good defense against SQL injection, so I use Symfony as the main user input.

But for this bulk loading, it's tooooooo slow.

If I build a text based, COPY file for bulk purposes, to be input via the command line, is Postgres vulnerable to SQL injection from that?

Dennis Gearon

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Pavel Stehule <pavel.stehule@gmail.com> writes:

2010/5/30 Dennis Gearon <gearond@sbcglobal.net>:

If I build a text based, COPY file for bulk purposes, to be input via the command line, is Postgres vulnerable to SQL injection from that?

SQL database cannot be injected via NON SQL statemenst like COPY.

Well, that depends. If you construct a script file like

COPY mytable FROM STDIN;
... data rows here ...
\.

then obviously somebody could inject SQL if they could get a line
beginning with \. into the data rows. However, if you put the data
rows in a *separate file* this is not possible.

ISTM though that this discussion is largely missing the point.
If you want to build COPY input from raw data, you have to be
prepared to do suitable quoting/escaping --- the rules are a bit
different from plain SQL quoting, but the concept is the same.
And if you do do that, you're immune from SQL injection in any case,
as is also true of plain old INSERTs. SQL injection is only a problem
for applications that fail to do quoting/escaping at all, or do it
incorrectly, and COPY is really not any safer if you blow that than
regular SQL is.

regards, tom lane

Well, I will use COPY with some confidence, then. And really look into the proper escaping. For now, though, I will use prepared statements.

One thing, can prepared statements be done, including the 'execute', inside of a transaction, and what are the side effects?

BTW, speaking of SQL injection, anyone seen this site?
http://sqlmap.sourceforge.net/demo.html

Dennis Gearon

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--- On Sun, 5/30/10, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Heyho!

On Monday 31 May 2010 04.18:04 Dennis Gearon wrote:

One thing, can prepared statements be done, including the 'execute',
inside of a transaction, and what are the side effects?

Semantically, the statement is exactly like a "not prepared" statement: it
happens at execute time, the rest (prepare, variable binding) happens
independently of the transaction as far as I know.

Performance: there may be slight differencies since prepared statements will
cache the query plan. Unless you have relatively complex queries where the
execution plan depends heavily on the actual values to be bound to the
prepared statement this shouldn't matter much, though.

(Somebody please correct me if I'm wrong, I'm not a pg pro :-)

cheers
-- vbi

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On 2010-05-30, Martin Gainty wrote:

i have mixed feelings about parameterised statements.

On the one hand a parameterised statement would be more
difficult for a Wireshark criminal to insert their own c**p
into a database because they would have to know the schema
a-priori for example they would have to know the names of the
database, table and the datatypes of these 2 statements
Insert DateField1 INTO DateTable VALUES(1) would gack as 1 is
not a valid date
Insert NumericField1 INTO NumericTable VALUES('A') would gack
as well as A is not a valid number

But thats only one line of defence..Struts..JSF and other
Frameworks have field validators so a good design would
involve 2 tiered defence
1)The web folks would put some kind of JS function to
disallow client know from enetering a invalid date

Sorry, but that isn't a security measure at all, you cannot even ensure
that it is executed. And if it is executed, it is executed on the client
side. It is at best useful for some usability niceties. It catches some
malformed input from non-malicious users, but any criminal just ignores
your JS and builds the request he wants.

2)The back-end folks (me) would validate Database params in
the servlet or the DTO as it makes its way to the VO and
before any of the offending values get into the database

That is what PreparedStatement.set*(...) (and the non-java pendants)
does by properly escaping input and transforming it to a representation
which exactly represents the datatype and not any kind of executable
statement.

The net effect is wireshark criminals are succeeding in
making everyone's lives a living hell..the least we can do is
take their pitchfork away!

That is not a problem with (prepared) statements at all, that is a
matter of protecting the wire. If you don't want your transmitted data
to be manipulated, you should use at least encryption or validated
signatures.

--
Robert...