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Commitd666796

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Add new escaping functions PQescapeLiteral and PQescapeIdentifier.
PQescapeLiteral is similar to PQescapeStringConn, but it relieves thecaller of the need to know how large the output buffer should be, andit provides the appropriate quoting (in addition to escaping specialcharacers within the string). PQescapeIdentifier provides similarfunctionality for escaping identifiers.Per recent discussion with Tom Lane.
1 parented1d3f5 commitd666796

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4 files changed

+254
-16
lines changed

4 files changed

+254
-16
lines changed

‎doc/src/sgml/libpq.sgml

Lines changed: 109 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.294 2010/01/20 21:15:21 petere Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.295 2010/01/21 14:58:52 rhaas Exp $ -->
22

33
<chapter id="libpq">
44
<title><application>libpq</application> - C Library</title>
@@ -2933,20 +2933,48 @@ typedef struct {
29332933
<variablelist>
29342934
<varlistentry>
29352935
<term>
2936-
<function>PQescapeStringConn</function>
2936+
<function>PQescapeLiteral</function>
29372937
<indexterm>
2938-
<primary>PQescapeStringConn</primary>
2938+
<primary>PQescapeLiteral</primary>
29392939
</indexterm>
29402940
</term>
29412941

29422942
<listitem>
29432943
<para>
2944-
<function>PQescapeStringConn</function> escapes a string for
2944+
<synopsis>
2945+
size_t PQescapeLiteral(PGconn *conn, char *str, size_t len)
2946+
</synopsis>
2947+
</para>
2948+
2949+
<para>
2950+
<function>PQescapeLiteral</function> escapes a string for
29452951
use within an SQL command. This is useful when inserting data
29462952
values as literal constants in SQL commands. Certain characters
29472953
(such as quotes and backslashes) must be escaped to prevent them
29482954
from being interpreted specially by the SQL parser.
2949-
<function>PQescapeStringConn</> performs this operation.
2955+
<function>PQescapeLiteral</> performs this operation.
2956+
</para>
2957+
2958+
<para>
2959+
<function>PQescapeLiteral</> returns an escaped version of the
2960+
<parameter>str</parameter> parameter in memory allocated with
2961+
<function>malloc()</>. This memory should be freed using
2962+
<function>PQfreemem()</> when the result is no longer needed.
2963+
A terminating zero byte is not required, and should not be
2964+
counted in <parameter>length</>. (If a terminating zero byte is found
2965+
before <parameter>length</> bytes are processed,
2966+
<function>PQescapeLiteral</> stops at the zero; the behavior is
2967+
thus rather like <function>strncpy</>.) The
2968+
return string has all special characters replaced so that they can
2969+
be properly processed by the <productname>PostgreSQL</productname>
2970+
string literal parser. A terminating zero byte is also added. The
2971+
single quotes that must surround <productname>PostgreSQL</productname>
2972+
string literals are included in the result string.
2973+
</para>
2974+
2975+
<para>
2976+
On error, <function>PQescapeLiteral</> returns NULL and a suitable
2977+
message is stored in the <parameter>conn</> object.
29502978
</para>
29512979

29522980
<tip>
@@ -2963,7 +2991,75 @@ typedef struct {
29632991
Note that it is not necessary nor correct to do escaping when a data
29642992
value is passed as a separate parameter in <function>PQexecParams</> or
29652993
its sibling routines.
2994+
</para>
2995+
</listitem>
2996+
</varlistentry>
2997+
2998+
<varlistentry>
2999+
<term>
3000+
<function>PQescapeIdentifier</function>
3001+
<indexterm>
3002+
<primary>PQescapeIdentifier</primary>
3003+
</indexterm>
3004+
</term>
3005+
3006+
<listitem>
3007+
<para>
3008+
<synopsis>
3009+
size_t PQescapeIdentifier(PGconn *conn, char *str, size_t len)
3010+
</synopsis>
3011+
</para>
3012+
3013+
<para>
3014+
<function>PQescapeIndentifier</function> escapes a string for
3015+
use as an SQL identifier, such as a table, column, or function name.
3016+
This is useful when a user-supplied identifier might contain
3017+
special characters that would otherwise not be interpreted as part
3018+
of the identifier by the SQL parser, or when the identifier might
3019+
contain uppercase characters whose case should be preserved.
3020+
</para>
29663021

3022+
<para>
3023+
<function>PQescapeIdentifier</> returns a version of the
3024+
<parameter>str</parameter> parameter escaped as an SQL identifier
3025+
in memory allocated with <function>malloc()</>. This memory must be
3026+
freed using <function>PQfreemem()</> when the result is no longer
3027+
needed. A terminating zero byte is not required, and should not be
3028+
counted in <parameter>length</>. (If a terminating zero byte is found
3029+
before <parameter>length</> bytes are processed,
3030+
<function>PQescapeIdentifier</> stops at the zero; the behavior is
3031+
thus rather like <function>strncpy</>.) The
3032+
return string has all special characters replaced so that it
3033+
will be properly processed as an SQL identifier. A terminating zero byte
3034+
is also added. The return string will also be surrounded by double
3035+
quotes.
3036+
</para>
3037+
3038+
<para>
3039+
On error, <function>PQescapeIdentifier</> returns NULL and a suitable
3040+
message is stored in the <parameter>conn</> object.
3041+
</para>
3042+
3043+
<tip>
3044+
<para>
3045+
As with string literals, to prevent SQL injection attacks,
3046+
SQL identifiers must be escaped when they are received from an
3047+
untrustworthy source.
3048+
</para>
3049+
</tip>
3050+
</listitem>
3051+
</varlistentry>
3052+
3053+
<varlistentry>
3054+
<term>
3055+
<function>PQescapeStringConn</function>
3056+
<indexterm>
3057+
<primary>PQescapeStringConn</primary>
3058+
</indexterm>
3059+
</term>
3060+
3061+
<listitem>
3062+
<para>
29673063
<synopsis>
29683064
size_t PQescapeStringConn (PGconn *conn,
29693065
char *to, const char *from, size_t length,
@@ -2972,12 +3068,12 @@ typedef struct {
29723068
</para>
29733069

29743070
<para>
2975-
<function>PQescapeStringConn</>writes an escaped version of the
2976-
<parameter>from</> string to the <parameter>to</> buffer, escaping
2977-
special characters so that they cannot cause any harm, and adding a
2978-
terminating zero byte. The single quotes that must surround
2979-
<productname>PostgreSQL</> string literals are not included in the
2980-
result string; they should be provided in the SQL command that the
3071+
<function>PQescapeStringConn</>escapes string literals, much like
3072+
<function>PQescapeLiteral</>. Unlike <function>PQescapeLiteral</>,
3073+
the caller is responsible for providing an appropriately sized buffer.
3074+
Furthermore, <function>PQescapeStringConn</> does not generate the
3075+
single quotes that must surround<productname>PostgreSQL</> string
3076+
literals; they should be provided in the SQL command that the
29813077
result is inserted into. The parameter <parameter>from</> points to
29823078
the first character of the string that is to be escaped, and the
29833079
<parameter>length</> parameter gives the number of bytes in this
@@ -3093,7 +3189,7 @@ typedef struct {
30933189
<para>
30943190
<function>PQescapeByteaConn</> returns an escaped version of the
30953191
<parameter>from</parameter> parameter binary string in memory
3096-
allocated with <function>malloc()</>. This memorymust be freed using
3192+
allocated with <function>malloc()</>. This memoryshould be freed using
30973193
<function>PQfreemem()</> when the result is no longer needed. The
30983194
return string has all special characters replaced so that they can
30993195
be properly processed by the <productname>PostgreSQL</productname>
@@ -4285,7 +4381,7 @@ typedef struct {
42854381
be non-<symbol>NULL</symbol>. <parameter>*buffer</> is set to
42864382
point to the allocated memory, or to <symbol>NULL</symbol> in cases
42874383
where no buffer is returned. A non-<symbol>NULL</symbol> result
4288-
buffermust be freed using <function>PQfreemem</> when no longer
4384+
buffershould be freed using <function>PQfreemem</> when no longer
42894385
needed.
42904386
</para>
42914387

‎src/interfaces/libpq/exports.txt

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.23 2009/03/31 01:41:27 tgl Exp $
1+
# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.24 2010/01/21 14:58:53 rhaas Exp $
22
# Functions to be exported by libpq DLLs
33
PQconnectdb 1
44
PQsetdbLogin 2
@@ -153,3 +153,5 @@ PQresultSetInstanceData 150
153153
PQfireResultCreateEvents 151
154154
PQconninfoParse 152
155155
PQinitOpenSSL 153
156+
PQescapeLiteral 154
157+
PQescapeIdentifier 155

‎src/interfaces/libpq/fe-exec.c

Lines changed: 139 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.206 2010/01/02 16:58:12 momjian Exp $
11+
* $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.207 2010/01/21 14:58:53 rhaas Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -3059,6 +3059,144 @@ PQescapeString(char *to, const char *from, size_t length)
30593059
}
30603060

30613061

3062+
/*
3063+
* Escape arbitrary strings. If as_ident is true, we escape the result
3064+
* as an identifier; if false, as a literal. The result is returned in
3065+
* a newly allocated buffer. If we fail due to an encoding violation or out
3066+
* of memory condition, we return NULL, storing an error message into conn.
3067+
*/
3068+
staticchar*
3069+
PQescapeInternal(PGconn*conn,constchar*str,size_tlen,intas_ident)
3070+
{
3071+
constchar*s;
3072+
char*result;
3073+
char*rp;
3074+
intnum_quotes=0;/* single or double, depending on as_ident */
3075+
intnum_backslashes=0;
3076+
intinput_len;
3077+
intresult_size;
3078+
charquote_char=as_ident ?'"' :'\'';
3079+
3080+
/* We must have a connection, else fail immediately. */
3081+
if (!conn)
3082+
returnNULL;
3083+
3084+
/* Scan the string for characters that must be escaped. */
3085+
for (s=str;*s!='\0'&& (s-str)<len;++s)
3086+
{
3087+
if (*s==quote_char)
3088+
++num_quotes;
3089+
elseif (*s=='\\')
3090+
++num_backslashes;
3091+
elseif (IS_HIGHBIT_SET(*s))
3092+
{
3093+
intcharlen;
3094+
3095+
/* Slow path for possible multibyte characters */
3096+
charlen=pg_encoding_mblen(conn->client_encoding,s);
3097+
3098+
/* Multibyte character overruns allowable length. */
3099+
if ((s-str)+charlen>len||memchr(s,0,charlen)!=NULL)
3100+
{
3101+
printfPQExpBuffer(&conn->errorMessage,
3102+
libpq_gettext("incomplete multibyte character\n"));
3103+
returnNULL;
3104+
}
3105+
3106+
/* Adjust s, bearing in mind that for loop will increment it. */
3107+
s+=charlen-1;
3108+
}
3109+
}
3110+
3111+
/* Allocate output buffer. */
3112+
input_len=s-str;
3113+
result_size=input_len+num_quotes+3;/* two quotes, plus a NUL */
3114+
if (!as_ident&&num_backslashes>0)
3115+
result_size+=num_backslashes+2;
3116+
result=rp= (char*)malloc(result_size);
3117+
if (rp==NULL)
3118+
{
3119+
printfPQExpBuffer(&conn->errorMessage,
3120+
libpq_gettext("out of memory\n"));
3121+
returnNULL;
3122+
}
3123+
3124+
/*
3125+
* If we are escaping a literal that contains backslashes, we use the
3126+
* escape string syntax so that the result is correct under either value
3127+
* of standard_conforming_strings. We also emit a leading space in this
3128+
* case, to guard against the possibility that the result might be
3129+
* interpolated immediately following an identifier.
3130+
*/
3131+
if (!as_ident&&num_backslashes>0)
3132+
{
3133+
*rp++=' ';
3134+
*rp++='E';
3135+
}
3136+
3137+
/* Opening quote. */
3138+
*rp++=quote_char;
3139+
3140+
/*
3141+
* Use fast path if possible.
3142+
*
3143+
* We've already verified that the input string is well-formed in the
3144+
* current encoding. If it contains no quotes and, in the case of
3145+
* literal-escaping, no backslashes, then we can just copy it directly
3146+
* to the output buffer, adding the necessary quotes.
3147+
*
3148+
* If not, we must rescan the input and process each character
3149+
* individually.
3150+
*/
3151+
if (num_quotes==0&& (num_backslashes==0||as_ident))
3152+
{
3153+
memcpy(rp,str,input_len);
3154+
rp+=input_len;
3155+
}
3156+
else
3157+
{
3158+
for (s=str;s-str<input_len;++s)
3159+
{
3160+
if (*s==quote_char|| (!as_ident&&*s=='\\'))
3161+
{
3162+
*rp++=*s;
3163+
*rp++=*s;
3164+
}
3165+
elseif (!IS_HIGHBIT_SET(*s))
3166+
*rp++=*s;
3167+
else
3168+
{
3169+
inti=pg_encoding_mblen(conn->client_encoding,s);
3170+
while (1)
3171+
{
3172+
*rp++=*s;
3173+
if (--i==0)
3174+
break;
3175+
++s;/* for loop will provide the final increment */
3176+
}
3177+
}
3178+
}
3179+
}
3180+
3181+
/* Closing quote and terminating NUL. */
3182+
*rp++=quote_char;
3183+
*rp='\0';
3184+
3185+
returnresult;
3186+
}
3187+
3188+
char*
3189+
PQescapeLiteral(PGconn*conn,constchar*str,size_tlen)
3190+
{
3191+
returnPQescapeInternal(conn,str,len,0);
3192+
}
3193+
3194+
char*
3195+
PQescapeIdentifier(PGconn*conn,constchar*str,size_tlen)
3196+
{
3197+
returnPQescapeInternal(conn,str,len,1);
3198+
}
3199+
30623200
/* HEX encoding support for bytea */
30633201
staticconstcharhextbl[]="0123456789abcdef";
30643202

‎src/interfaces/libpq/libpq-fe.h

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.148 2010/01/02 16:58:12 momjian Exp $
10+
* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.149 2010/01/21 14:58:53 rhaas Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -471,6 +471,8 @@ extern intPQsetvalue(PGresult *res, int tup_num, int field_num, char *value, in
471471
externsize_tPQescapeStringConn(PGconn*conn,
472472
char*to,constchar*from,size_tlength,
473473
int*error);
474+
externchar*PQescapeLiteral(PGconn*conn,constchar*str,size_tlen);
475+
externchar*PQescapeIdentifier(PGconn*conn,constchar*str,size_tlen);
474476
externunsignedchar*PQescapeByteaConn(PGconn*conn,
475477
constunsignedchar*from,size_tfrom_length,
476478
size_t*to_length);

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