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fix oob read on malformed length field in dba flatfile handler #22266

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fix oob read on malformed length field in dba flatfile handler #22266

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9f244ce
fix oob read on malformed length field in dba flatfile handler
alhudz Jun 10, 2026
647dab2
ext/dba: fold repeated flatfile length guard into a macro
alhudz Jun 19, 2026
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60 changes: 28 additions & 32 deletions ext/dba/libflatfile/flatfile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,18 @@

#define FLATFILE_BLOCK_SIZE 1024

/* Parse the length prefix in `buf` into `num` and grow `buf` to hold it.
* atoi() narrows a malformed (e.g. negative) length to a huge size_t whose
* `+ FLATFILE_BLOCK_SIZE` would overflow erealloc(); the macro yields true in
* that case so the caller stops reading and the read stays within `buf_size`. */
#define FLATFILE_GROW_BUF(num, buf, buf_size) ( \
(num) = atoi(buf), \
(num) >= (buf_size) && ( \
(num) > SIZE_MAX - FLATFILE_BLOCK_SIZE \
|| ((buf) = erealloc((buf), (buf_size) = (num) + FLATFILE_BLOCK_SIZE), 0) \
) \
)

/*
* ret = -1 means that database was opened for read-only
* ret = 0 success
Expand Down Expand Up @@ -110,10 +122,8 @@ int flatfile_delete(flatfile *dba, datum key_datum) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
pos = php_stream_tell(dba->fp);

Expand All @@ -133,10 +143,8 @@ int flatfile_delete(flatfile *dba, datum key_datum) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
/* read in the value */
num = php_stream_read(dba->fp, buf, num);
Expand All @@ -160,10 +168,8 @@ int flatfile_findkey(flatfile *dba, datum key_datum) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
num = php_stream_read(dba->fp, buf, num);

Expand All @@ -176,10 +182,8 @@ int flatfile_findkey(flatfile *dba, datum key_datum) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
num = php_stream_read(dba->fp, buf, num);
}
Expand All @@ -200,10 +204,8 @@ datum flatfile_firstkey(flatfile *dba) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
num = php_stream_read(dba->fp, buf, num);

Expand All @@ -216,10 +218,8 @@ datum flatfile_firstkey(flatfile *dba) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
num = php_stream_read(dba->fp, buf, num);
}
Expand All @@ -242,20 +242,16 @@ datum flatfile_nextkey(flatfile *dba) {
if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
num = php_stream_read(dba->fp, buf, num);

if (!php_stream_gets(dba->fp, buf, 15)) {
break;
}
num = atoi(buf);
if (num >= buf_size) {
buf_size = num + FLATFILE_BLOCK_SIZE;
buf = erealloc(buf, buf_size);
if (FLATFILE_GROW_BUF(num, buf, buf_size)) {
break;
}
num = php_stream_read(dba->fp, buf, num);

Expand Down
31 changes: 31 additions & 0 deletions ext/dba/tests/dba_flatfile_oob.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
--TEST--
DBA FlatFile handler bounds with a malformed (negative) length field
--EXTENSIONS--
dba
--SKIPIF--
<?php
require_once __DIR__ . '/setup/setup_dba_tests.inc';
check_skip('flatfile');
?>
--FILE--
<?php
$db_file = __DIR__ . '/dba_flatfile_oob.db';
// A negative length narrows to a huge size_t and previously overran the read buffer.
file_put_contents($db_file, "-1\n" . str_repeat('A', 200000));

$db = dba_open($db_file, 'r', 'flatfile');
var_dump(dba_firstkey($db));
var_dump(dba_exists("AAAA", $db));
var_dump(dba_fetch("AAAA", $db));
dba_close($db);
echo "done\n";
?>
--CLEAN--
<?php
@unlink(__DIR__ . '/dba_flatfile_oob.db');
?>
--EXPECT--
bool(false)
bool(false)
bool(false)
done
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