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Add a new GUC parameter backslash_quote, which determines whether the SQL

parser will allow "\'" to be used to represent a literal quote mark.  The
"\'" representation has been deprecated for some time in favor of the
SQL-standard representation "''" (two single quote marks), but it has been
used often enough that just disallowing it immediately won't do.  Hence
backslash_quote allows the settings "on", "off", and "safe_encoding",
the last meaning to allow "\'" only if client_encoding is a valid server
encoding.  That is now the default, and the reason is that in encodings
such as SJIS that allow 0x5c (ASCII backslash) to be the last byte of a
multibyte character, accepting "\'" allows SQL-injection attacks as per
CVE-2006-2314 (further details will be published after release).  The
"on" setting is available for backward compatibility, but it must not be
used with clients that are exposed to untrusted input.

Thanks to Akio Ishida and Yasuo Ohgaki for identifying this security issue.
This commit is contained in:
Tom Lane
2006-05-21 20:12:20 +00:00
parent 5c4de67044
commit 16e77740ea
6 changed files with 99 additions and 6 deletions

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@ -1,5 +1,5 @@
<!-- <!--
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.147.2.7 2003/04/04 00:32:57 tgl Exp $ $Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.147.2.8 2006/05/21 20:12:20 tgl Exp $
--> -->
<Chapter Id="runtime"> <Chapter Id="runtime">
@ -1318,6 +1318,35 @@ env PGOPTIONS='-c geqo=off' psql
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry id="guc-backslash-quote" xreflabel="backslash_quote">
<term><varname>BACKSLASH_QUOTE</varname> (<type>string</type>)</term>
<indexterm><primary>strings</><secondary>backslash quotes</></>
<indexterm>
<primary><varname>backslash_quote</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
This controls whether a quote mark can be represented by
<literal>\'</> in a string literal. The preferred, SQL-standard way
to represent a quote mark is by doubling it (<literal>''</>) but
<productname>PostgreSQL</> has historically also accepted
<literal>\'</>. However, use of <literal>\'</> creates security risks
because in some client character set encodings, there are multibyte
characters in which the last byte is numerically equivalent to ASCII
<literal>\</>. If client-side code does escaping incorrectly then a
SQL-injection attack is possible. This risk can be prevented by
making the server reject queries in which a quote mark appears to be
escaped by a backslash.
The allowed values of <varname>backslash_quote</> are
<literal>on</> (allow <literal>\'</> always),
<literal>off</> (reject always), and
<literal>safe_encoding</> (allow only if client encoding does not
allow ASCII <literal>\</> within a multibyte character).
<literal>safe_encoding</> is the default setting.
</para>
</listitem>
</varlistentry>
<varlistentry> <varlistentry>
<term><varname>CLIENT_ENCODING</varname> (<type>string</type>)</term> <term><varname>CLIENT_ENCODING</varname> (<type>string</type>)</term>
<indexterm><primary>character set encoding</></> <indexterm><primary>character set encoding</></>

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@ -9,7 +9,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/scan.l,v 1.102.2.2 2005/08/16 00:48:58 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/parser/scan.l,v 1.102.2.3 2006/05/21 20:12:20 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -39,6 +39,15 @@ extern YYSTYPE yylval;
static int xcdepth = 0; /* depth of nesting in slash-star comments */ static int xcdepth = 0; /* depth of nesting in slash-star comments */
/*
* GUC variables. This is a DIRECT violation of the warning given at the
* head of gram.y, ie flex/bison code must not depend on any GUC variables;
* as such, changing their values can induce very unintuitive behavior.
* But we shall have to live with it as a short-term thing until the switch
* to SQL-standard string syntax is complete.
*/
BackslashQuoteType backslash_quote = BACKSLASH_QUOTE_SAFE_ENCODING;
/* /*
* literalbuf is used to accumulate literal values when multiple rules * literalbuf is used to accumulate literal values when multiple rules
* are needed to parse a single literal. Call startlit to reset buffer * are needed to parse a single literal. Call startlit to reset buffer
@ -376,6 +385,13 @@ other .
addlit(yytext, yyleng); addlit(yytext, yyleng);
} }
<xq>{xqescape} { <xq>{xqescape} {
if (yytext[1] == '\'')
{
if (backslash_quote == BACKSLASH_QUOTE_OFF ||
(backslash_quote == BACKSLASH_QUOTE_SAFE_ENCODING &&
PG_ENCODING_IS_CLIENT_ONLY(pg_get_client_encoding())))
elog(ERROR, "unsafe use of \\' in a string literal");
}
addlitchar(unescape_single_char(yytext[1])); addlitchar(unescape_single_char(yytext[1]));
} }
<xq>{xqoctesc} { <xq>{xqoctesc} {

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@ -5,7 +5,7 @@
* command, configuration file, and command line options. * command, configuration file, and command line options.
* See src/backend/utils/misc/README for more information. * See src/backend/utils/misc/README for more information.
* *
* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.99.2.6 2006/02/12 22:33:47 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.99.2.7 2006/05/21 20:12:20 tgl Exp $
* *
* Copyright 2000 by PostgreSQL Global Development Group * Copyright 2000 by PostgreSQL Global Development Group
* Written by Peter Eisentraut <peter_e@gmx.net>. * Written by Peter Eisentraut <peter_e@gmx.net>.
@ -38,6 +38,7 @@
#include "optimizer/geqo.h" #include "optimizer/geqo.h"
#include "optimizer/paths.h" #include "optimizer/paths.h"
#include "optimizer/planmain.h" #include "optimizer/planmain.h"
#include "parser/gramparse.h"
#include "parser/parse_expr.h" #include "parser/parse_expr.h"
#include "storage/fd.h" #include "storage/fd.h"
#include "storage/freespace.h" #include "storage/freespace.h"
@ -72,6 +73,8 @@ static const char *assign_facility(const char *facility,
static const char *assign_msglvl(int *var, const char *newval, static const char *assign_msglvl(int *var, const char *newval,
bool doit, bool interactive); bool doit, bool interactive);
static const char *assign_backslash_quote(const char *newval, bool doit,
bool interactive);
/* /*
* Debugging options * Debugging options
@ -124,6 +127,7 @@ const char client_min_messages_str_default[] = "notice";
* and is kept in sync by assign_hooks. * and is kept in sync by assign_hooks.
*/ */
static double phony_random_seed; static double phony_random_seed;
static char *backslash_quote_string;
static char *client_encoding_string; static char *client_encoding_string;
static char *datestyle_string; static char *datestyle_string;
static char *default_iso_level_string; static char *default_iso_level_string;
@ -736,6 +740,11 @@ static struct config_real
static struct config_string static struct config_string
ConfigureNamesString[] = ConfigureNamesString[] =
{ {
{
{"backslash_quote", PGC_USERSET}, &backslash_quote_string,
"safe_encoding", assign_backslash_quote, NULL
},
{ {
{"client_encoding", PGC_USERSET, GUC_IS_NAME}, &client_encoding_string, {"client_encoding", PGC_USERSET, GUC_IS_NAME}, &client_encoding_string,
"SQL_ASCII", assign_client_encoding, NULL "SQL_ASCII", assign_client_encoding, NULL
@ -3060,4 +3069,30 @@ assign_msglvl(int *var, const char *newval, bool doit, bool interactive)
return newval; /* OK */ return newval; /* OK */
} }
static const char *
assign_backslash_quote(const char *newval, bool doit, bool interactive)
{
BackslashQuoteType bq;
bool bqbool;
/*
* Although only "on", "off", and "safe_encoding" are documented,
* we use parse_bool so we can accept all the likely variants of
* "on" and "off".
*/
if (strcasecmp(newval, "safe_encoding") == 0)
bq = BACKSLASH_QUOTE_SAFE_ENCODING;
else if (parse_bool(newval, &bqbool))
{
bq = bqbool ? BACKSLASH_QUOTE_ON : BACKSLASH_QUOTE_OFF;
}
else
return NULL; /* reject */
if (doit)
backslash_quote = bq;
return newval;
}
#include "guc-file.c" #include "guc-file.c"

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@ -206,4 +206,5 @@
#transform_null_equals = false #transform_null_equals = false
#statement_timeout = 0 # 0 is disabled, in milliseconds #statement_timeout = 0 # 0 is disabled, in milliseconds
#db_user_namespace = false #db_user_namespace = false
#backslash_quote = safe_encoding # on, off, or safe_encoding

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@ -3,7 +3,7 @@
* *
* Copyright 2000-2002 by PostgreSQL Global Development Group * Copyright 2000-2002 by PostgreSQL Global Development Group
* *
* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.64 2002/09/04 20:31:36 momjian Exp $ * $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.64.2.1 2006/05/21 20:12:20 tgl Exp $
*/ */
/*---------------------------------------------------------------------- /*----------------------------------------------------------------------
@ -269,6 +269,7 @@ psql_completion(char *text, int start, int end)
"cpu_operator_cost", "cpu_operator_cost",
"geqo_selection_bias", "geqo_selection_bias",
"backslash_quote",
"default_transaction_isolation", "default_transaction_isolation",
"search_path", "search_path",
"statement_timeout", "statement_timeout",

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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $Id: gramparse.h,v 1.25 2002/09/04 20:31:45 momjian Exp $ * $Id: gramparse.h,v 1.25.2.1 2006/05/21 20:12:20 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -18,6 +18,17 @@
#include "lib/stringinfo.h" #include "lib/stringinfo.h"
#include "nodes/parsenodes.h" #include "nodes/parsenodes.h"
typedef enum
{
BACKSLASH_QUOTE_OFF,
BACKSLASH_QUOTE_ON,
BACKSLASH_QUOTE_SAFE_ENCODING
} BackslashQuoteType;
/* GUC variables in scan.l (every one of these is a bad idea :-() */
extern BackslashQuoteType backslash_quote;
/* from parser.c */ /* from parser.c */
extern void parser_param_set(Oid *typev, int nargs); extern void parser_param_set(Oid *typev, int nargs);
extern Oid param_type(int t); extern Oid param_type(int t);