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Remove libpq's PQescapeIdentifier(), not safe from injection attacks.

This commit is contained in:
Bruce Momjian 2006-07-04 13:22:15 +00:00
parent 530eab592c
commit 3fafac3f62
4 changed files with 4 additions and 106 deletions
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64
doc/src/sgml/libpq.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.212 2006/06/27 00:03:41 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.213 2006/07/04 13:22:15 momjian Exp $ -->
<chapter id="libpq">
<title><application>libpq</application> - C Library</title>
@ -2279,68 +2279,6 @@ in favor of <function>PQescapeStringConn</>.
</para>
</sect2>
<sect2 id="libpq-exec-escape-identifier">
<title>Escaping Identifier for Inclusion in SQL Commands</title>
<indexterm zone="libpq-exec-escape-identifier"><primary>PQescapeIdentifier</></>
<indexterm zone="libpq-exec-escape-identifier"><primary>escaping strings</></>
<para>
<function>PQescapeIdentifier</function> escapes a string for use
as an identifier name within an SQL command. For example; table names,
column names, view names and user names are all identifiers.
Double quotes (") must be escaped to prevent them from being interpreted
specially by the SQL parser. <function>PQescapeIdentifier</> performs this
operation.
</para>
<tip>
<para>
It is especially important to do proper escaping when handling strings that
were received from an untrustworthy source. Otherwise there is a security
risk: you are vulnerable to <quote>SQL injection</> attacks wherein unwanted
SQL commands are fed to your database.
</para>
</tip>
<para>
Note that it is still necessary to do escaping of identifiers when
using functions that support parameterized queries such as <function>PQexecParams</> or
its sibling routines. Only literal values are automatically escaped
using these functions, not identifiers.
<synopsis>
size_t PQescapeIdentifier (char *to, const char *from, size_t length);
</synopsis>
</para>
<para>
The parameter <parameter>from</> points to the first character of the
string that is to be escaped, and the <parameter>length</> parameter
gives the number of characters in this string. A terminating zero byte
is not required, and should not be counted in <parameter>length</>. (If
a terminating zero byte is found before <parameter>length</> bytes are
processed, <function>PQescapeIdentifier</> stops at the zero; the
behavior is thus rather like <function>strncpy</>.) <parameter>to</>
shall point to a buffer that is able to hold at least one more character
than twice the value of <parameter>length</>, otherwise the behavior is
undefined. A call to <function>PQescapeIdentifier</> writes an escaped
version of the <parameter>from</> string to the <parameter>to</> buffer,
replacing special characters so that they cannot cause any harm, and
adding a terminating zero byte. The double quotes that may surround
<productname>PostgreSQL</> identifiers are not included in the result
string; they should be provided in the SQL command that the result is
inserted into.
</para>
<para>
<function>PQescapeIdentifier</> returns the number of characters written
to <parameter>to</>, not including the terminating zero byte.
</para>
<para>
Behavior is undefined if the <parameter>to</> and <parameter>from</>
strings overlap.
</para>
</sect2>
<sect2 id="libpq-exec-escape-bytea">
<title>Escaping Binary Strings for Inclusion in SQL Commands</title>

4
src/interfaces/libpq/exports.txt
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@ -1,4 +1,4 @@
# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.12 2006/06/27 00:03:41 momjian Exp $
# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.13 2006/07/04 13:22:15 momjian Exp $
# Functions to be exported by libpq DLLs
PQconnectdb 1
PQsetdbLogin 2
@ -130,5 +130,3 @@ PQescapeByteaConn 127
PQencryptPassword 128
PQisthreadsafe 129
enlargePQExpBuffer 130
PQescapeIdentifier 131

38
src/interfaces/libpq/fe-exec.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.187 2006/06/27 00:03:41 momjian Exp $
* $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.188 2006/07/04 13:22:15 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -2515,42 +2515,6 @@ PQescapeString(char *to, const char *from, size_t length)
static_std_strings);
}
/*
* Escaping arbitrary strings to get valid SQL identifier strings.
*
* Replaces " with "".
*
* length is the length of the source string. (Note: if a terminating NUL
* is encountered sooner, PQescapeIdentifier stops short of "length"; the behavior
* is thus rather like strncpy.)
*
* For safety the buffer at "to" must be at least 2*length + 1 bytes long.
* A terminating NUL character is added to the output string, whether the
* input is NUL-terminated or not.
*
* Returns the actual length of the output (not counting the terminating NUL).
*/
size_t
PQescapeIdentifier(char *to, const char *from, size_t length)
{
const char *source = from;
char *target = to;
size_t remaining = length;
while (remaining > 0 && *source != '\0')
{
if (*source == '"')
*target++ = *source;
*target++ = *source++;
remaining--;
}
/* Write the terminating NUL character. */
*target = '\0';
return target - to;
}
/*
* PQescapeBytea - converts from binary string to the
* minimal encoding necessary to include the string in an SQL

4
src/interfaces/libpq/libpq-fe.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.130 2006/06/27 00:03:42 momjian Exp $
* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.131 2006/07/04 13:22:15 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -436,8 +436,6 @@ extern unsigned char *PQescapeByteaConn(PGconn *conn,
size_t *to_length);
extern unsigned char *PQunescapeBytea(const unsigned char *strtext,
size_t *retbuflen);
extern size_t PQescapeIdentifier(char *to, const char *from, size_t length);
/* These forms are deprecated! */
extern size_t PQescapeString(char *to, const char *from, size_t length);
extern unsigned char *PQescapeBytea(const unsigned char *from, size_t from_length,