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Bug #48518 curl crashes when writing into invalid file handle
Submitted: 2009-06-10 12:51 UTC Modified: 2009-06-28 10:05 UTC
Votes:1
Avg. Score:5.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: tony2001@php.net Assigned: iliaa (profile)
Status: Closed Package: cURL related
PHP Version: 5.*, 6CVS (2009-06-27) OS: *
Private report: No CVE-ID: None
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 [2009-06-10 12:51 UTC] tony2001@php.net 
Description:
------------
curl_setopt() doesn't increase reference count of file pointers passed along with CURLOPT_FILE and CURLOPT_WRITEHEADER options, which leads to invalid read/writes and as a result - random crashes because FILE* pointer is destroyed before write().

Simple patch fixes this problem, but there is another one to consider: should the refcount be decreased when closing the cURL handle?

Patch proposed: http://dev.daylessday.org/diff/curl_write_handle.diff

Reproduce code:
---------------
<?php
$tmp_dir = "/tmp/2";
$urls = array(
    'http://ru.php.net/manual/en/function.curl-errno.php',
    'http://ru.php.net/manual/en/function.curl-multi-close.php',
    'http://ru.php.net/manual/en/function.curl-multi-getcontent.php',
    'http://ru.php.net/manual/en/function.curl-multi-remove-handle.php',
);

$mh = curl_multi_init();
foreach ($urls as $url) {
    $ch = curl_init();

    $tmp_url = parse_url($url);
    $tmp_file = $tmp_dir."/".basename($tmp_url['path']);
    $fp = fopen($tmp_file, "w");

    curl_setopt($ch, CURLOPT_RETURNTRANSFER,0);
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_FILE, $fp);

    curl_multi_add_handle($mh, $ch);
}

$running = 0;
do {
    curl_multi_exec($mh, $running);
} while ($running > 0);

?>


Actual result:
--------------
==29222== Invalid read of size 2
==29222==    at 0x60411F9: fwrite (in /lib64/libc-2.8.so)
==29222==    by 0x45078F: curl_write (interface.c:882)
==29222==    by 0x5738691: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x5750CC2: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x574D8F3: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x5752F7B: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x575380A: curl_multi_perform (in /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x45736A: zif_curl_multi_exec (multi.c:216)
==29222==    by 0x6340F6: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:313)
==29222==    by 0x639955: ZEND_DO_FCALL_SPEC_CONST_HANDLER (zend_vm_execute.h:1601)
==29222==    by 0x633386: execute (zend_vm_execute.h:104)
==29222==    by 0x6045FA: zend_execute_scripts (zend.c:1188)
==29222==    by 0x58FFDE: php_execute_script (main.c:2171)
==29222==    by 0x6E904A: main (php_cli.c:1188)

==29222== Invalid write of size 8
==29222==    at 0x6041245: fwrite (in /lib64/libc-2.8.so)
==29222==    by 0x45078F: curl_write (interface.c:882)
==29222==    by 0x5738691: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x5750CC2: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x574D8F3: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x5752F7B: (within /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x575380A: curl_multi_perform (in /usr/lib64/libcurl.so.4.0.1)
==29222==    by 0x45736A: zif_curl_multi_exec (multi.c:216)
==29222==    by 0x6340F6: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:313)
==29222==    by 0x639955: ZEND_DO_FCALL_SPEC_CONST_HANDLER (zend_vm_execute.h:1601)
==29222==    by 0x633386: execute (zend_vm_execute.h:104)
==29222==    by 0x6045FA: zend_execute_scripts (zend.c:1188)
==29222==    by 0x58FFDE: php_execute_script (main.c:2171)
==29222==    by 0x6E904A: main (php_cli.c:1188)

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 [2009-06-10 13:41 UTC] tony2001@php.net 
Found another piece of strange code:
PHP_FUNCTION(curl_exec)
....
    ch->uses++;

    if (ch->handlers->write->method == PHP_CURL_RETURN && ch->handlers->write->buf.len > 0) {
        --ch->uses;
        smart_str_0(&ch->handlers->write->buf);
        RETURN_STRINGL(ch->handlers->write->buf.c, ch->handlers->write->buf.len, 1);
    }
    --ch->uses;
...

What's the point in uses++ and immediate uses-- ?
 [2009-06-15 12:39 UTC] iliaa@php.net 
This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.
 [2009-06-26 17:33 UTC] rasmus@php.net 
It looks like the fix for this broke this case:

<?php
$url = 'http://slowgeek.com/test.xml';
$cfile = '/var/tmp/test_'.$prefix.md5($url).'.xml';
$ch = curl_init();
curl_setopt($ch, CURLOPT_FILE, $fp = fopen($cfile,'w'));
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_TIMEOUT, 60);
curl_setopt($ch, CURLOPT_URL, $url);
$status = curl_exec($ch);
if(!$status) echo curl_error($ch);
fclose($fp);
curl_close($ch);
$data = file_get_contents($cfile);
var_dump($data);  // 0 bytes here
fflush($fp);      // fflush after the fclose??
$data = file_get_contents($cfile);
var_dump($data);  // full contents here
 [2009-06-28 10:05 UTC] pajoye@php.net 
This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.
 
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