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Commit703b3fd

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Add pg_encoding_set_invalid()
There are cases where we cannot / do not want to error out for invalidlyencoded input. In such cases it can be useful to replace e.g. an incompletemulti-byte characters with bytes that will trigger an error when gettingvalidated as part of a larger string.Unfortunately, until now, for some encoding no such sequence existed. Forthose encodings this commit removes one previously accepted input combination- we consider that to be ok, as the chosen bytes are outside of the validranges for the encodings, we just previously failed to detect that.As we cannot add a new field to pg_wchar_table without breaking ABI, this isimplemented "in-line" in the newly added function.Author: Noah Misch <noah@leadboat.com>Reviewed-by: Andres Freund <andres@anarazel.de>Backpatch-through: 13Security:CVE-2025-1094
1 parent0fb4598 commit703b3fd

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5 files changed

+117
-1
lines changed

5 files changed

+117
-1
lines changed

‎src/common/wchar.c

Lines changed: 54 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,25 @@
1616
#include"utils/ascii.h"
1717

1818

19+
/*
20+
* In today's multibyte encodings other than UTF8, this two-byte sequence
21+
* ensures pg_encoding_mblen() == 2 && pg_encoding_verifymbstr() == 0.
22+
*
23+
* For historical reasons, several verifychar implementations opt to reject
24+
* this pair specifically. Byte pair range constraints, in encoding
25+
* originator documentation, always excluded this pair. No core conversion
26+
* could translate it. However, longstanding verifychar implementations
27+
* accepted any non-NUL byte. big5_to_euc_tw and big5_to_mic even translate
28+
* pairs not valid per encoding originator documentation. To avoid tightening
29+
* core or non-core conversions in a security patch, we sought this one pair.
30+
*
31+
* PQescapeString() historically used spaces for BYTE1; many other values
32+
* could suffice for BYTE1.
33+
*/
34+
#defineNONUTF8_INVALID_BYTE0 (0x8d)
35+
#defineNONUTF8_INVALID_BYTE1 (' ')
36+
37+
1938
/*
2039
* Operations on multi-byte encodings are driven by a table of helper
2140
* functions.
@@ -1526,6 +1545,11 @@ pg_big5_verifychar(const unsigned char *s, int len)
15261545
if (len<l)
15271546
return-1;
15281547

1548+
if (l==2&&
1549+
s[0]==NONUTF8_INVALID_BYTE0&&
1550+
s[1]==NONUTF8_INVALID_BYTE1)
1551+
return-1;
1552+
15291553
while (--l>0)
15301554
{
15311555
if (*++s=='\0')
@@ -1575,6 +1599,11 @@ pg_gbk_verifychar(const unsigned char *s, int len)
15751599
if (len<l)
15761600
return-1;
15771601

1602+
if (l==2&&
1603+
s[0]==NONUTF8_INVALID_BYTE0&&
1604+
s[1]==NONUTF8_INVALID_BYTE1)
1605+
return-1;
1606+
15781607
while (--l>0)
15791608
{
15801609
if (*++s=='\0')
@@ -1624,6 +1653,11 @@ pg_uhc_verifychar(const unsigned char *s, int len)
16241653
if (len<l)
16251654
return-1;
16261655

1656+
if (l==2&&
1657+
s[0]==NONUTF8_INVALID_BYTE0&&
1658+
s[1]==NONUTF8_INVALID_BYTE1)
1659+
return-1;
1660+
16271661
while (--l>0)
16281662
{
16291663
if (*++s=='\0')
@@ -2067,6 +2101,19 @@ pg_utf8_islegal(const unsigned char *source, int length)
20672101
}
20682102

20692103

2104+
/*
2105+
* Fills the provided buffer with two bytes such that:
2106+
* pg_encoding_mblen(dst) == 2 && pg_encoding_verifymbstr(dst) == 0
2107+
*/
2108+
void
2109+
pg_encoding_set_invalid(intencoding,char*dst)
2110+
{
2111+
Assert(pg_encoding_max_length(encoding)>1);
2112+
2113+
dst[0]= (encoding==PG_UTF8 ?0xc0 :NONUTF8_INVALID_BYTE0);
2114+
dst[1]=NONUTF8_INVALID_BYTE1;
2115+
}
2116+
20702117
/*
20712118
*-------------------------------------------------------------------
20722119
* encoding info table
@@ -2189,5 +2236,11 @@ pg_encoding_max_length(int encoding)
21892236
{
21902237
Assert(PG_VALID_ENCODING(encoding));
21912238

2192-
returnpg_wchar_table[encoding].maxmblen;
2239+
/*
2240+
* Check for the encoding despite the assert, due to some mingw versions
2241+
* otherwise issuing bogus warnings.
2242+
*/
2243+
returnPG_VALID_ENCODING(encoding) ?
2244+
pg_wchar_table[encoding].maxmblen :
2245+
pg_wchar_table[PG_SQL_ASCII].maxmblen;
21932246
}

‎src/include/mb/pg_wchar.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -573,6 +573,7 @@ extern intpg_valid_server_encoding_id(int encoding);
573573
* (in addition to the ones just above). The constant tables declared
574574
* earlier in this file are also available from libpgcommon.
575575
*/
576+
externvoidpg_encoding_set_invalid(intencoding,char*dst);
576577
externintpg_encoding_mblen(intencoding,constchar*mbstr);
577578
externintpg_encoding_mblen_bounded(intencoding,constchar*mbstr);
578579
externintpg_encoding_dsplen(intencoding,constchar*mbstr);

‎src/test/regress/expected/conversion.out

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,13 @@
55
\getenv libdir PG_LIBDIR
66
\getenv dlsuffix PG_DLSUFFIX
77
\set regresslib :libdir '/regress' :dlsuffix
8+
CREATE FUNCTION test_enc_setup() RETURNS void
9+
AS :'regresslib', 'test_enc_setup'
10+
LANGUAGE C STRICT;
11+
SELECT FROM test_enc_setup();
12+
--
13+
(1 row)
14+
815
CREATE FUNCTION test_enc_conversion(bytea, name, name, bool, validlen OUT int, result OUT bytea)
916
AS :'regresslib', 'test_enc_conversion'
1017
LANGUAGE C STRICT;

‎src/test/regress/regress.c

Lines changed: 50 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1099,6 +1099,56 @@ test_opclass_options_func(PG_FUNCTION_ARGS)
10991099
PG_RETURN_NULL();
11001100
}
11011101

1102+
/* one-time tests for encoding infrastructure */
1103+
PG_FUNCTION_INFO_V1(test_enc_setup);
1104+
Datum
1105+
test_enc_setup(PG_FUNCTION_ARGS)
1106+
{
1107+
/* Test pg_encoding_set_invalid() */
1108+
for (inti=0;i<_PG_LAST_ENCODING_;i++)
1109+
{
1110+
charbuf[2],
1111+
bigbuf[16];
1112+
intlen,
1113+
mblen,
1114+
valid;
1115+
1116+
if (pg_encoding_max_length(i)==1)
1117+
continue;
1118+
pg_encoding_set_invalid(i,buf);
1119+
len=strnlen(buf,2);
1120+
if (len!=2)
1121+
elog(WARNING,
1122+
"official invalid string for encoding \"%s\" has length %d",
1123+
pg_enc2name_tbl[i].name,len);
1124+
mblen=pg_encoding_mblen(i,buf);
1125+
if (mblen!=2)
1126+
elog(WARNING,
1127+
"official invalid string for encoding \"%s\" has mblen %d",
1128+
pg_enc2name_tbl[i].name,mblen);
1129+
valid=pg_encoding_verifymbstr(i,buf,len);
1130+
if (valid!=0)
1131+
elog(WARNING,
1132+
"official invalid string for encoding \"%s\" has valid prefix of length %d",
1133+
pg_enc2name_tbl[i].name,valid);
1134+
valid=pg_encoding_verifymbstr(i,buf,1);
1135+
if (valid!=0)
1136+
elog(WARNING,
1137+
"first byte of official invalid string for encoding \"%s\" has valid prefix of length %d",
1138+
pg_enc2name_tbl[i].name,valid);
1139+
memset(bigbuf,' ',sizeof(bigbuf));
1140+
bigbuf[0]=buf[0];
1141+
bigbuf[1]=buf[1];
1142+
valid=pg_encoding_verifymbstr(i,bigbuf,sizeof(bigbuf));
1143+
if (valid!=0)
1144+
elog(WARNING,
1145+
"trailing data changed official invalid string for encoding \"%s\" to have valid prefix of length %d",
1146+
pg_enc2name_tbl[i].name,valid);
1147+
}
1148+
1149+
PG_RETURN_VOID();
1150+
}
1151+
11021152
/*
11031153
* Call an encoding conversion or verification function.
11041154
*

‎src/test/regress/sql/conversion.sql

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,11 @@
88

99
\set regresslib :libdir'/regress' :dlsuffix
1010

11+
CREATEFUNCTIONtest_enc_setup() RETURNS void
12+
AS :'regresslib','test_enc_setup'
13+
LANGUAGE C STRICT;
14+
SELECTFROM test_enc_setup();
15+
1116
CREATEFUNCTIONtest_enc_conversion(bytea, name, name, bool, validlen OUTint, result OUTbytea)
1217
AS :'regresslib','test_enc_conversion'
1318
LANGUAGE C STRICT;

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