Performance problem with php

15 years ago by Vincenzo D'Amore — view source

unread

Hello all,

I have already notified to the mailing list a performance problem with
apache/mod_php5.

Now I have an update and I think this is probably a bug.
PHP lstat the full path more times before read the file when in apache httpd
configuration is specified *PHP_ADMIN_VALUE open_basedir *setting.

I have a simple website with only phpinfo.php page and inside we have only
"<? phpinfo() ?>".

httpd.2.2.15 fresh compiled and PHP 5.2.13.

If is specified PHP_ADMIN_VALUE open_basedir in Virtual host
configuration:

          PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace"*

</Directory> <VirtualHost *:80> ServerName damorealt.xoom.it DocumentRoot "/usr/local/myspace/webspace/httpdocs" CustomLog /var/log/httpd/damorealt/access_log combined ErrorLog /var/log/httpd/damorealt/error_log </VirtualHost >

Calling page http://damorealt.xoom.it/phpinfo.php we can reproduce following
behavior:

25933 accept(3, {sa_family=AF_INET, sin_port=htons(47433),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
25933 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
25933 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
25933 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
25933 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
25933 gettimeofday({1278695388, 52976}, NULL) = 0
25933 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No such
file or directory)
25933 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1 ENOENT
(No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) = -1
ENOENT (No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
25933 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}}, NULL) =
0
25933 rt_sigaction(SIGPROF, {0x2b80442fdd80, [PROF], SA_RESTORER|SA_RESTART,
0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
25933 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
25933 getcwd("/"..., 4095) = 2
25933 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...})
= 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

First check

Second check

Third check (incomplete)

Final check and then read the file.

25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) =
16
25933 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 read(16, "<? phpinfo() ?>\n", 8192) = 16
25933 read(16, "", 8192) = 0
25933 read(16, "", 8192) = 0
25933 close(16) = 0

If PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace" is
removedin virtual host configuration we finally have simpliest
behavior:

226235 accept(3, {sa_family=AF_INET, sin_port=htons(59366),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
26235 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
26235 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
26235 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
26235 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
26235 gettimeofday({1278696735, 988799}, NULL) = 0
26235 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No such
file or directory)
26235 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1 ENOENT
(No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) = -1
ENOENT (No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}}, NULL) =
0
26235 rt_sigaction(SIGPROF, {0x2afef587dd80, [PROF], SA_RESTORER|SA_RESTART,
0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
26235 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
26235 getcwd("/"..., 4095) = 2
26235 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

26235 time(NULL) = 1278696735
26235 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...})
= 0
26235 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

And read the file.

26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) =
16
26235 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 read(16, "<? phpinfo() ?>\n", 8192) = 16
26235 read(16, "", 8192) = 0
26235 read(16, "", 8192) = 0
26235 close(16) = 0
26235 uname({sys="Linux", node="svilpar4", ...}) = 0
26235 time(NULL) = 1278696735
26235 writev(15, [{"HTTP/1.1 200 OK\r\nDate: Fri, 09 J"..., 173},
{"<!DOCTYPE html PUBLIC \"-//W3C//D"..., 4109}, {"<table border=\"0\" cellpadding=\"3"..., 4101}], 3) = 8383 26235 writev(15, [{"<tr><td class="e">highlight.bg</"..., 4105},
{"sendmail_from</td><td class="v">"..., 4099}], 2) = 8204
26235 time(NULL) = 1278696735
26235 writev(15, [{" </td></tr>\n<tr><td class="e">HT"..., 4108},
{"</td><td class="v">1024</td><td "..., 4098}], 2) = 8206
26235 writev(15, [{"md2 md4 md5 sha1 sha256 sha384 s"..., 4098}, {"

</td></tr>\n</table><br />\n<tabl"..., 4106}], 2) = 8204 26235 writev(15, [{"session.use_cookies</td><td clas"..., 4104}, {" </td><td class=\"v\">enabled </td"..., 4102}], 2) = 8206 26235 chdir("/") = 0 26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0 26235 writev(15, [{"\"]</td><td class=\"v\">Keep-Alive<"..., 4206}], 1) = 4206 26235 write(10, "212.48.14.186 - - [09/Jul/2010:1"..., 116) = 116 26235 shutdown(15, 1 /* send */) = 0 26235 poll([{fd=15, events=POLLIN}], 1, 2000) = 1 ([{fd=15, revents=POLLIN|POLLHUP}]) 26235 read(15, "", 512) = 0 26235 close(15) = 0 26235 read(4, 0x7fff615ff5eb, 1) = -1 EAGAIN (Resource temporarily unavailable) 26235 accept(3,

Note that this behavior also happens when safemode is ON.

Can somebody explain me why PHP have such behavior?

Best regards,
Vincenzo

15 years ago by Vincenzo D'Amore — view source

unread

Hello All,

could anybody explain me why if safe_mode or open_basedir are set, realpath
cache is disabled?

Looking at source code main/main.c of 5.2.13 I can see:

1292: /* Disable realpath cache if safe_mode or open_basedir are set */
if (PG(safe_mode) || (PG(open_basedir) && *PG(open_basedir))) {
CWDG(realpath_cache_size_limit) = 0;
}

1769: /* Disable realpath cache if safe_mode or open_basedir are set */
if (PG(safe_mode) || (PG(open_basedir) && *PG(open_basedir))) {
CWDG(realpath_cache_size_limit) = 0;
}

So realpath cache is definitely disabled in case of safe_mode or
open_basedir.

This dramatically reduce performance of PHP Engine and, in a big production
environment, this behavior can bring servers to its knees.
Especially because there is a lack of documentation!

Hello all,

I have already notified to the mailing list a performance problem with
apache/mod_php5.

Now I have an update and I think this is probably a bug.
PHP lstat the full path more times before read the file when in apache
httpd configuration is specified *PHP_ADMIN_VALUE open_basedir *setting.

I have a simple website with only phpinfo.php page and inside we have only
"<? phpinfo() ?>".

httpd.2.2.15 fresh compiled and PHP 5.2.13.

If is specified PHP_ADMIN_VALUE open_basedir in Virtual host
configuration:

<Directory "/usr/local/myspace/webspace/httpdocs">
          PHP_ADMIN_VALUE open_basedir
"/usr/local/myspace/webspace"*
</Directory>
<VirtualHost *:80>
ServerName damorealt.xoom.it
DocumentRoot "/usr/local/myspace/webspace/httpdocs"
CustomLog /var/log/httpd/damorealt/access_log combined
ErrorLog /var/log/httpd/damorealt/error_log
</VirtualHost >

Calling page http://damorealt.xoom.it/phpinfo.php we can reproduce
following behavior:

25933 accept(3, {sa_family=AF_INET, sin_port=htons(47433),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
25933 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
25933 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
25933 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
25933 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
25933 gettimeofday({1278695388, 52976}, NULL) = 0
25933 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No such
file or directory)
25933 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1 ENOENT
(No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) = -1
ENOENT (No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
25933 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}}, NULL)
= 0
25933 rt_sigaction(SIGPROF, {0x2b80442fdd80, [PROF],
SA_RESTORER|SA_RESTART, 0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
25933 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
25933 getcwd("/"..., 4095) = 2
25933 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

First check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Second check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0

Third check (incomplete)

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Final check and then read the file.

25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) =
16
25933 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 read(16, "<? phpinfo() ?>\n", 8192) = 16
25933 read(16, "", 8192) = 0
25933 read(16, "", 8192) = 0
25933 close(16) = 0

If *PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace" is removed

in virtual host configuration we finally have simpliest behavior:

226235 accept(3, {sa_family=AF_INET, sin_port=htons(59366),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
26235 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
26235 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
26235 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
26235 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
26235 gettimeofday({1278696735, 988799}, NULL) = 0
26235 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No such
file or directory)
26235 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1 ENOENT
(No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) = -1
ENOENT (No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}}, NULL)
= 0
26235 rt_sigaction(SIGPROF, {0x2afef587dd80, [PROF],
SA_RESTORER|SA_RESTART, 0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
26235 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
26235 getcwd("/"..., 4095) = 2
26235 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

26235 time(NULL) = 1278696735
26235 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
26235 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

And read the file.

26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) =
16
26235 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 read(16, "<? phpinfo() ?>\n", 8192) = 16
26235 read(16, "", 8192) = 0
26235 read(16, "", 8192) = 0
26235 close(16) = 0
26235 uname({sys="Linux", node="svilpar4", ...}) = 0
26235 time(NULL) = 1278696735
26235 writev(15, [{"HTTP/1.1 200 OK\r\nDate: Fri, 09 J"..., 173},
{"<!DOCTYPE html PUBLIC \"-//W3C//D"..., 4109}, {"<table border=\"0\" cellpadding=\"3"..., 4101}], 3) = 8383 26235 writev(15, [{"<tr><td class="e">highlight.bg</"..., 4105},
{"sendmail_from</td><td class="v">"..., 4099}], 2) = 8204
26235 time(NULL) = 1278696735
26235 writev(15, [{" </td></tr>\n<tr><td class="e">HT"..., 4108},
{"</td><td class="v">1024</td><td "..., 4098}], 2) = 8206
26235 writev(15, [{"md2 md4 md5 sha1 sha256 sha384 s"..., 4098}, {"
</td></tr>\n</table><br />\n<tabl"..., 4106}], 2) = 8204 26235 writev(15, [{"session.use_cookies</td><td clas"..., 4104}, {" </td><td class=\"v\">enabled </td"..., 4102}], 2) = 8206 26235 chdir("/") = 0 26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0 26235 writev(15, [{"\"]</td><td class=\"v\">Keep-Alive<"..., 4206}], 1) = 4206 26235 write(10, "212.48.14.186 - - [09/Jul/2010:1"..., 116) = 116 26235 shutdown(15, 1 /* send */) = 0 26235 poll([{fd=15, events=POLLIN}], 1, 2000) = 1 ([{fd=15, revents=POLLIN|POLLHUP}]) 26235 read(15, "", 512) = 0 26235 close(15) = 0 26235 read(4, 0x7fff615ff5eb, 1) = -1 EAGAIN (Resource temporarily unavailable) 26235 accept(3,
Note that this behavior also happens when safemode is ON.

Can somebody explain me why PHP have such behavior?

Best regards,
Vincenzo

--
Vincenzo D'Amore
email: v.damore@gmail.com
msn: freedev@hotmail.com
skype: free.dev
mobile: +39 349 8513251

15 years ago by Pierre Joye — view source

unread

hi,

Please do not double posts both in the bug report and here. Or it will
be a pain to follow.

Cheers,

Hello All,

could anybody explain me why if safe_mode or open_basedir are set, realpath
cache is disabled?

Looking at source code main/main.c of 5.2.13 I can see:

1292: /* Disable realpath cache if safe_mode or open_basedir are set */
if (PG(safe_mode) || (PG(open_basedir) && *PG(open_basedir))) {
CWDG(realpath_cache_size_limit) = 0;
}

1769: /* Disable realpath cache if safe_mode or open_basedir are set */
if (PG(safe_mode) || (PG(open_basedir) && *PG(open_basedir))) {
CWDG(realpath_cache_size_limit) = 0;
}

So realpath cache is definitely disabled in case of safe_mode or
open_basedir.

This dramatically reduce performance of PHP Engine and, in a big production
environment, this behavior can bring servers to its knees.
Especially because there is a lack of documentation!

Hello all,

I have already notified to the mailing list a performance problem with
apache/mod_php5.

Now I have an update and I think this is probably a bug.
PHP lstat the full path more times before read the file when in apache
httpd configuration is specified *PHP_ADMIN_VALUE open_basedir *setting.

I have a simple website with only phpinfo.php page and inside we have only
"<? phpinfo() ?>".

httpd.2.2.15 fresh compiled and PHP 5.2.13.

If is specified PHP_ADMIN_VALUE open_basedir in Virtual host
configuration:

<Directory "/usr/local/myspace/webspace/httpdocs">
* PHP_ADMIN_VALUE open_basedir
"/usr/local/myspace/webspace"*
</Directory>
<VirtualHost *:80>
ServerName damorealt.xoom.it
DocumentRoot "/usr/local/myspace/webspace/httpdocs"
CustomLog /var/log/httpd/damorealt/access_log combined
ErrorLog /var/log/httpd/damorealt/error_log
</VirtualHost >

Calling page http://damorealt.xoom.it/phpinfo.php we can reproduce
following behavior:

25933 accept(3, {sa_family=AF_INET, sin_port=htons(47433),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
25933 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
25933 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
25933 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
25933 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
25933 gettimeofday({1278695388, 52976}, NULL) = 0
25933 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No such
file or directory)
25933 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1 ENOENT
(No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) = -1
ENOENT (No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
25933 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}}, NULL)
= 0
25933 rt_sigaction(SIGPROF, {0x2b80442fdd80, [PROF],
SA_RESTORER|SA_RESTART, 0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
25933 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
25933 getcwd("/"..., 4095) = 2
25933 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

First check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Second check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0

Third check (incomplete)

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Final check and then read the file.

25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) =
16
25933 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 read(16, "<? phpinfo() ?>\n", 8192) = 16
25933 read(16, "", 8192) = 0
25933 read(16, "", 8192) = 0
25933 close(16) = 0

If *PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace" is removed

in virtual host configuration we finally have simpliest behavior:

226235 accept(3, {sa_family=AF_INET, sin_port=htons(59366),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
26235 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
26235 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
26235 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
26235 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
26235 gettimeofday({1278696735, 988799}, NULL) = 0
26235 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No such
file or directory)
26235 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1 ENOENT
(No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) = -1
ENOENT (No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}}, NULL)
= 0
26235 rt_sigaction(SIGPROF, {0x2afef587dd80, [PROF],
SA_RESTORER|SA_RESTART, 0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
26235 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
26235 getcwd("/"..., 4095) = 2
26235 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

26235 time(NULL) = 1278696735
26235 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
26235 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

And read the file.

26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) =
16
26235 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 read(16, "<? phpinfo() ?>\n", 8192) = 16
26235 read(16, "", 8192) = 0
26235 read(16, "", 8192) = 0
26235 close(16) = 0
26235 uname({sys="Linux", node="svilpar4", ...}) = 0
26235 time(NULL) = 1278696735
26235 writev(15, [{"HTTP/1.1 200 OK\r\nDate: Fri, 09 J"..., 173},
{"<!DOCTYPE html PUBLIC \"-//W3C//D"..., 4109}, {"<table border=\"0\" cellpadding=\"3"..., 4101}], 3) = 8383 26235 writev(15, [{"<tr><td class="e">highlight.bg</"..., 4105},
{"sendmail_from</td><td class="v">"..., 4099}], 2) = 8204
26235 time(NULL) = 1278696735
26235 writev(15, [{" </td></tr>\n<tr><td class="e">HT"..., 4108},
{"</td><td class="v">1024</td><td "..., 4098}], 2) = 8206
26235 writev(15, [{"md2 md4 md5 sha1 sha256 sha384 s"..., 4098}, {"
</td></tr>\n</table><br />\n<tabl"..., 4106}], 2) = 8204 26235 writev(15, [{"session.use_cookies</td><td clas"..., 4104}, {" </td><td class=\"v\">enabled </td"..., 4102}], 2) = 8206 26235 chdir("/") = 0 26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0 26235 writev(15, [{"\"]</td><td class=\"v\">Keep-Alive<"..., 4206}], 1) = 4206 26235 write(10, "212.48.14.186 - - [09/Jul/2010:1"..., 116) = 116 26235 shutdown(15, 1 /* send */) = 0 26235 poll([{fd=15, events=POLLIN}], 1, 2000) = 1 ([{fd=15, revents=POLLIN|POLLHUP}]) 26235 read(15, "", 512) = 0 26235 close(15) = 0 26235 read(4, 0x7fff615ff5eb, 1) = -1 EAGAIN (Resource temporarily unavailable) 26235 accept(3,
Note that this behavior also happens when safemode is ON.

Can somebody explain me why PHP have such behavior?

Best regards,
Vincenzo

--
Vincenzo D'Amore
email: v.damore@gmail.com
msn: freedev@hotmail.com
skype: free.dev
mobile: +39 349 8513251

--
Pierre

@pierrejoye | http://blog.thepimp.net | http://www.libgd.org

15 years ago by Vincenzo D'Amore — view source

unread

Hi,

thank you for reading my posts, could anybody help me to
understand why realpath cache is disabled if safe_mode or open_basedir are
set?
Or must I remove safe_mode and open_basedir setting at all?

Is there a document that describe a best practice to follow this way (for
example a list of PHP function we have to disable).

hi,

Please do not double posts both in the bug report and here. Or it will
be a pain to follow.

Cheers,

On Tue, Jul 13, 2010 at 11:08 AM, Vincenzo D'Amore v.damore@gmail.com
wrote:
Hello All,

could anybody explain me why if safe_mode or open_basedir are set,
realpath
cache is disabled?

Looking at source code main/main.c of 5.2.13 I can see:

1292: /* Disable realpath cache if safe_mode or open_basedir are set */
if (PG(safe_mode) || (PG(open_basedir) && *PG(open_basedir))) {
CWDG(realpath_cache_size_limit) = 0;
}

1769: /* Disable realpath cache if safe_mode or open_basedir are set */
if (PG(safe_mode) || (PG(open_basedir) && *PG(open_basedir))) {
CWDG(realpath_cache_size_limit) = 0;
}

So realpath cache is definitely disabled in case of safe_mode or
open_basedir.

This dramatically reduce performance of PHP Engine and, in a big
production
environment, this behavior can bring servers to its knees.
Especially because there is a lack of documentation!

On Fri, Jul 9, 2010 at 7:39 PM, Vincenzo D'Amore v.damore@gmail.com
wrote:
Hello all,

I have already notified to the mailing list a performance problem with
apache/mod_php5.

Now I have an update and I think this is probably a bug.
PHP lstat the full path more times before read the file when in apache
httpd configuration is specified *PHP_ADMIN_VALUE open_basedir *setting.

I have a simple website with only phpinfo.php page and inside we have
only
"<? phpinfo() ?>".

httpd.2.2.15 fresh compiled and PHP 5.2.13.

If is specified PHP_ADMIN_VALUE open_basedir in Virtual host
configuration:

<Directory "/usr/local/myspace/webspace/httpdocs">
          PHP_ADMIN_VALUE open_basedir
"/usr/local/myspace/webspace"*
</Directory>
<VirtualHost *:80>
ServerName damorealt.xoom.it
DocumentRoot "/usr/local/myspace/webspace/httpdocs"
CustomLog /var/log/httpd/damorealt/access_log combined
ErrorLog /var/log/httpd/damorealt/error_log
</VirtualHost >

Calling page http://damorealt.xoom.it/phpinfo.php we can reproduce
following behavior:

25933 accept(3, {sa_family=AF_INET, sin_port=htons(47433),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
25933 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
25933 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
25933 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
25933 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
25933 gettimeofday({1278695388, 52976}, NULL) = 0
25933 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No
such
file or directory)
25933 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1
ENOENT
(No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) =
-1
ENOENT (No such file or directory)
25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
25933 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}},
NULL)
= 0
25933 rt_sigaction(SIGPROF, {0x2b80442fdd80, [PROF],
SA_RESTORER|SA_RESTART, 0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
25933 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
25933 getcwd("/"..., 4095) = 2
25933 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

First check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Second check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0

Third check (incomplete)

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Final check and then read the file.

25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY)
=
16
25933 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 read(16, "<? phpinfo() ?>\n", 8192) = 16
25933 read(16, "", 8192) = 0
25933 read(16, "", 8192) = 0
25933 close(16) = 0

If *PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace" is
removed

in virtual host configuration we finally have simpliest behavior:

226235 accept(3, {sa_family=AF_INET, sin_port=htons(59366),
sin_addr=inet_addr("212.48.14.186")}, [17179869200]) = 15
26235 getsockname(15, {sa_family=AF_INET, sin_port=htons(80),
sin_addr=inet_addr("151.99.197.198")}, [17179869200]) = 0
26235 fcntl(15, F_GETFL) = 0x2 (flags O_RDWR)
26235 fcntl(15, F_SETFL, O_RDWR|O_NONBLOCK) = 0
26235 read(15, "GET /phpinfo.php HTTP/1.0\r\nUser-"..., 8000) = 129
26235 gettimeofday({1278696735, 988799}, NULL) = 0
26235 stat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 open("/usr/local/myspace/.htaccess", O_RDONLY) = -1 ENOENT (No
such
file or directory)
26235 open("/usr/local/myspace/webspace/.htaccess", O_RDONLY) = -1
ENOENT
(No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/.htaccess", O_RDONLY) =
-1
ENOENT (No such file or directory)
26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php/.htaccess";,
O_RDONLY) = -1 ENOTDIR (Not a directory)
26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={20, 0}},
NULL)
= 0
26235 rt_sigaction(SIGPROF, {0x2afef587dd80, [PROF],
SA_RESTORER|SA_RESTART, 0x3916e302d0}, {SIG_DFL, [], 0}, 8) = 0
26235 rt_sigprocmask(SIG_UNBLOCK, [PROF], NULL, 8) = 0
26235 getcwd("/"..., 4095) = 2
26235 chdir("/usr/local/myspace/webspace/httpdocs") = 0

water boiling point

26235 time(NULL) = 1278696735
26235 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
26235 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

And read the file.

26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY)
=
16
26235 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 read(16, "<? phpinfo() ?>\n", 8192) = 16
26235 read(16, "", 8192) = 0
26235 read(16, "", 8192) = 0
26235 close(16) = 0
26235 uname({sys="Linux", node="svilpar4", ...}) = 0
26235 time(NULL) = 1278696735
26235 writev(15, [{"HTTP/1.1 200 OK\r\nDate: Fri, 09 J"..., 173},
{"<!DOCTYPE html PUBLIC \"-//W3C//D"..., 4109}, {"<table border=\"0\" cellpadding=\"3"..., 4101}], 3) = 8383 26235 writev(15, [{"<tr><td class="e">highlight.bg</"..., 4105},
{"sendmail_from</td><td class="v">"..., 4099}], 2) = 8204
26235 time(NULL) = 1278696735
26235 writev(15, [{" </td></tr>\n<tr><td class="e">HT"..., 4108},
{"</td><td class="v">1024</td><td "..., 4098}], 2) = 8206
26235 writev(15, [{"md2 md4 md5 sha1 sha256 sha384 s"..., 4098}, {"
</td></tr>\n</table><br />\n<tabl"..., 4106}], 2) = 8204 26235 writev(15, [{"session.use_cookies</td><td clas"..., 4104}, {" </td><td class=\"v\">enabled </td"..., 4102}], 2) = 8206 26235 chdir("/") = 0 26235 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}},
NULL) =

0
26235 writev(15, [{""]</td><td class="v">Keep-Alive<"..., 4206}], 1)
=
4206
26235 write(10, "212.48.14.186 - - [09/Jul/2010:1"..., 116) = 116
26235 shutdown(15, 1 /* send */) = 0
26235 poll([{fd=15, events=POLLIN}], 1, 2000) = 1 ([{fd=15,
revents=POLLIN|POLLHUP}])
26235 read(15, "", 512) = 0
26235 close(15) = 0
26235 read(4, 0x7fff615ff5eb, 1) = -1 EAGAIN (Resource
temporarily
unavailable)
26235 accept(3,

Note that this behavior also happens when safemode is ON.

Can somebody explain me why PHP have such behavior?

Best regards,
Vincenzo

--
Vincenzo D'Amore
email: v.damore@gmail.com
msn: freedev@hotmail.com
skype: free.dev
mobile: +39 349 8513251

--
Pierre

@pierrejoye | http://blog.thepimp.net | http://www.libgd.org

--
Vincenzo D'Amore
email: v.damore@gmail.com
msn: freedev@hotmail.com
skype: free.dev
mobile: +39 349 8513251

15 years ago by johannes@schlueters.de — view source

unread

thank you for reading my posts, could anybody help me to
understand why realpath cache is disabled if safe_mode or open_basedir are
set?

For security reasons.

Assume the following (simplified) code:

<?php
symlink('./bar', 'foo');
access_bar_in_some_way_to_get_it_cached();
unlink('bar');
symlink('/', 'bar');
do_bad_things_with_bar();
?>

and suddenly you've bypassed the check as for do_bad_things_with_bar()
the cached value is used. Now I hear you say "then invalidate the cache
entries" or something like that, but well, there are so many ways to
achieve such a result (including from outside PHP) that the check won't
be reliable in any way anymore.

That's the issue one has with security features on application level,
the operating system itself can implement it way more efficiently but
this doesn't (easily) work with a mod_php vhost config (solaris +
mod_privileges would be one way, probably linux + apparmor can do,
too ...)

johannes

15 years ago by Vincenzo D'Amore — view source

unread

Thanks Johannes,

you are really clear and I finally understand what's the problem.
I'm following a big free web hosting service, I would like to enhance
performance of customers webspache.

What do you think if:

set safe_mode off
remove open_basedir
disable_functions symlink, unlink
- w/ functions: passthru, proc_close, proc_get_status, proc_nice,
  proc, exec, shell_exec, system, proc_open, popen, curl_multi_exec,
  parse_ini_file, show_source, set_time_limit, error_reporting, mail,
  fsockopen, ini_set

2010/7/13 Johannes Schlüter johannes@schlueters.de

thank you for reading my posts, could anybody help me to
understand why realpath cache is disabled if safe_mode or open_basedir
are
set?

For security reasons.

Assume the following (simplified) code:

<?php
symlink('./bar', 'foo');
access_bar_in_some_way_to_get_it_cached();
unlink('bar');
symlink('/', 'bar');
do_bad_things_with_bar();
?>

and suddenly you've bypassed the check as for do_bad_things_with_bar()
the cached value is used. Now I hear you say "then invalidate the cache
entries" or something like that, but well, there are so many ways to
achieve such a result (including from outside PHP) that the check won't
be reliable in any way anymore.

That's the issue one has with security features on application level,
the operating system itself can implement it way more efficiently but
this doesn't (easily) work with a mod_php vhost config (solaris +
mod_privileges would be one way, probably linux + apparmor can do,
too ...)

johannes

--
Vincenzo D'Amore
email: v.damore@gmail.com
msn: freedev@hotmail.com
skype: free.dev
mobile: +39 349 8513251

15 years ago by Pierre Joye — view source

unread

2010/7/13 Vincenzo D'Amore v.damore@gmail.com:

Thanks Johannes,
you are really clear and I finally understand what's the problem.
I'm following a big free web hosting service, I would like to enhance
performance of customers webspache.
What do you think if:

set safe_mode off
remove open_basedir
disable_functions symlink, unlink

w/ functions: passthru, proc_close, proc_get_status, proc_nice, proc, exec,
shell_exec, system, proc_open, popen, curl_multi_exec, parse_ini_file,
show_source, set_time_limit, error_reporting, mail, fsockopen, ini_set

I suppose you don't provide shell access?

ps: please use text email

--
Pierre

@pierrejoye | http://blog.thepimp.net | http://www.libgd.org