Installing PECL/PEAR PHP modules on a RHEL box

The default RHEL 5.2 installation does not come with xdebug as part of any of the php RPMs. A quick look around the Net also provided no real RPM candidates that I could use on this system so I had to fall back to using the package management tools (pecl and pear) provided by php.

PECL's Odyssey
RHEL is a general PITA for me already so I just sigh and get on with it:

$ sudo pecl install xdebug
downloading xdebug-2.0.3.tgz ...
Starting to download xdebug-2.0.3.tgz (286,325 bytes)
...........................................................done: 286,325 bytes
66 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20060613
Zend Extension Api No:   220060519
/usr/bin/phpize: /tmp/pear/download/xdebug-2.0.3/build/shtool: /bin/sh: bad interpreter: Permission denied
Cannot find autoconf. Please check your autoconf installation and the $PHP_AUTOCONF
environment variable is set correctly and then rerun this script.

ERROR: `phpize' failed

Yep, loving it already!

Why on earth am I not able to invoke /bin/sh (as can be seen by the '/bin/sh: bad interpreter: Permission denied' error above)? Let's see if root can actually run the shell interpreter:

$ sudo /bin/sh
sh-3.2# exit

OK, everything looks good. Why is it breaking when we're trying to run the interpreter from /tmp/pear/download/xdebug-2.0.3/build/shtool?

Back to basics
Perhaps this has something to do with where we're trying to run it from and the user we're doing the installation as (root) seems to be capable of running the interpreter but not from the shtool script for some reason.

$ ls -ld /tmp/
drwxrwxrwt 17 root root 4096 Jun 18 07:41 /tmp/

Obviously _not_ a permissions issue.

$ grep tmp /etc/fstab
/dev/sda2     /tmp    ext3    defaults,nosuid,nodev,noexec    1 2

Ah, there you are! /tmp is mounted with a 'noexec' flag so that's what's causing the execution to fail when we try to install xdebug via pecl. No problem, I'll just set pecl to use /var/tmp instead ... oh, wait, on RHEL systems /var/tmp is just a symlink to /tmp.

*sigh*

Hand me half a brick
Time to work around the issue. Let's go find those directories pear expects to be somehow related to /tmp or /var/tmp:

$ pear config-show | grep tmp
PEAR Installer download        download_dir     /tmp/pear/download
PEAR Installer temp directory  temp_dir         /var/tmp

I updated these to temporarily point elsewhere:

$ pecl config-show| grep tmp
PEAR Installer download        download_dir     /root/tmp/pear/download
PEAR Installer temp directory  temp_dir         /root/tmp
$ sudo mkdir -p /root/tmp/pear/download

Second verse, same as the first
Let's give that installation another whirl and see where we are:

$ sudo pecl install xdebug
downloading xdebug-2.0.3.tgz ...
Starting to download xdebug-2.0.3.tgz (286,325 bytes)
.....................................done: 286,325 bytes
66 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20060613
Zend Extension Api No:   220060519
building in /var/tmp/pear-build-root/xdebug-2.0.3
running: /root/tmp/pear/download/xdebug-2.0.3/configure
checking for egrep... grep -E
checking for a sed that does not truncate output... /bin/sed
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... configure: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details.
ERROR: `/root/tmp/pear/download/xdebug-2.0.3/configure' failed

A quick look at /root/tmp/pear/download/xdebug-2.0.3/configure shows no obvious reasons why we're failing so out comes the cluebat :

$ sudo strace pecl insstall xdebug 2>&1
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
execve("/usr/bin/pecl", ["pecl", "install", "xdebug"], [/* 16 vars */]) = 0
brk(0)                                  = 0x8c3d000

[... truncated ...]

flock(3, LOCK_UN)                       = 0
close(3)                                = 0
write(1, "ERROR: `/root/tmp/pear/download/"..., 63ERROR: `/root/tmp/pear/download/xdebug-2.0.3/configure' failed
) = 63
stat64("/var/tmp/pear-build-root/xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp/pear-build-root/xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/var/tmp/pear-build-root/xdebug-2.0.3", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
time(NULL)                              = 1213740767
lstat64("/var", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp", {st_mode=S_IFLNK|0777, st_size=4, ...}) = 0
readlink("/var/tmp", "/tmp", 4096)      = 4
lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root/xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
getdents(3, /* 4 entries */, 4096)      = 80
getdents(3, /* 0 entries */, 4096)      = 0
close(3)                                = 0
stat64("/tmp/pear-build-root/xdebug-2.0.3/config.log", {st_mode=S_IFREG|0644, st_size=4948, ...}) = 0
stat64("/tmp/pear-build-root/xdebug-2.0.3/config.nice", {st_mode=S_IFREG|0755, st_size=93, ...}) = 0
unlink("/tmp/pear-build-root/xdebug-2.0.3/config.log") = 0
unlink("/tmp/pear-build-root/xdebug-2.0.3/config.nice") = 0
rmdir("/tmp/pear-build-root/xdebug-2.0.3") = 0
stat64("/var/tmp/pear-build-root/install-xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp/pear-build-root/install-xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/var/tmp/pear-build-root/install-xdebug-2.0.3", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
time(NULL)                              = 1213740767
lstat64("/var", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp", {st_mode=S_IFLNK|0777, st_size=4, ...}) = 0
readlink("/var/tmp", "/tmp", 4096)      = 4
lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root/install-xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
getdents(3, /* 2 entries */, 4096)      = 32
getdents(3, /* 0 entries */, 4096)      = 0
close(3)                                = 0
rmdir("/tmp/pear-build-root/install-xdebug-2.0.3") = 0
stat64("/tmp/glibctestUP8dWe", 0xbfa97ca0) = -1 ENOENT (No such file or directory)
unlink("/tmp/glibctestUP8dWe")          = -1 ENOENT (No such file or directory)
umask(022)                              = 022
close(2)                                = 0
close(1)                                = 0
close(0)                                = 0
munmap(0xb7fd6000, 4096)                = 0
setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
brk(0xa3ce000)                          = 0xa3ce000
setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
brk(0xa18a000)                          = 0xa18a000
exit_group(0)

After all that pecl (aka pear) still tried to muck with /tmp by trying to run things in /var/tmp/pear-build-root/xdebug-2.0.3.

Fine. Be that way.

$ sudo cd /tmp && rm -fr pear pear-build-root
$ sudo ln -s /root/tmp/pear-build-root .

One more time please Sam:

$ sudo pecl install xdebug
downloading xdebug-2.0.3.tgz ...
Starting to download xdebug-2.0.3.tgz (286,325 bytes)
.....................................................done: 286,325 bytes
66 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20060613
Zend Extension Api No:   220060519
building in /var/tmp/pear-build-root/xdebug-2.0.3
running: /root/tmp/pear/download/xdebug-2.0.3/configure
checking for egrep... grep -E
checking for a sed that does not truncate output... /bin/sed
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes

[... truncated ...]

Build complete.
Don't forget to run 'make test'.

running: make INSTALL_ROOT="/var/tmp/pear-build-root/install-xdebug-2.0.3" install
Installing shared extensions:     /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php/modules/
running: find "/var/tmp/pear-build-root/install-xdebug-2.0.3" -ls
36962402    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3
36962465    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr
36962466    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib
36962467    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php
36962468    4 drwxr-xr-x   2 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php/modules
36962464  608 -rwxr-xr-x   1 root     root       618210 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php/modules/xdebug.so

Build process completed successfully
Installing '/usr/lib/php/modules/xdebug.so'
install ok: channel://pecl.php.net/xdebug-2.0.3
configuration option "php_ini" is not set to php.ini location
You should add "extension=xdebug.so" to php.ini

Smell that? It's sweet success!

No more crawling, it's time to walk!
Let's finish the install off for brevity's sake:

$ sudo echo 'zend_extension="/usr/lib/php/modules/xdebug.so"' > /etc/php.d/xdebug.ini
$ php -i | grep xdebug
/etc/php.d/xdebug.ini,
xdebug
xdebug support => enabled
xdebug.auto_trace => Off => Off
xdebug.collect_includes => On => On
xdebug.collect_params => 0 => 0
xdebug.collect_return => Off => Off
xdebug.collect_vars => Off => Off
xdebug.default_enable => On => On
xdebug.dump.COOKIE => no value => no value
xdebug.dump.ENV => no value => no value
xdebug.dump.FILES => no value => no value
xdebug.dump.GET => no value => no value
xdebug.dump.POST => no value => no value
xdebug.dump.REQUEST => no value => no value
xdebug.dump.SERVER => no value => no value
xdebug.dump.SESSION => no value => no value
xdebug.dump_globals => On => On
xdebug.dump_once => On => On
xdebug.dump_undefined => Off => Off
xdebug.extended_info => On => On
xdebug.idekey => root => no value
xdebug.manual_url => http://www.php.net => http://www.php.net
xdebug.max_nesting_level => 100 => 100
xdebug.profiler_aggregate => Off => Off
xdebug.profiler_append => Off => Off
xdebug.profiler_enable => Off => Off
xdebug.profiler_enable_trigger => Off => Off
xdebug.profiler_output_dir => /tmp => /tmp
xdebug.profiler_output_name => cachegrind.out.%p => cachegrind.out.%p
xdebug.remote_autostart => Off => Off
xdebug.remote_enable => Off => Off
xdebug.remote_handler => dbgp => dbgp
xdebug.remote_host => localhost => localhost
xdebug.remote_log => no value => no value
xdebug.remote_mode => req => req
xdebug.remote_port => 9000 => 9000
xdebug.show_exception_trace => Off => Off
xdebug.show_local_vars => Off => Off
xdebug.show_mem_delta => Off => Off
xdebug.trace_format => 0 => 0
xdebug.trace_options => 0 => 0
xdebug.trace_output_dir => /tmp => /tmp
xdebug.trace_output_name => trace.%c => trace.%c
xdebug.var_display_max_children => 128 => 128
xdebug.var_display_max_data => 512 => 512
xdebug.var_display_max_depth => 3 => 3

I can now delete those temporary directories I created in /root/tmp and get back to twitching in the corner, or ...

Easy alternative - just add remount
Instead of the hoops I jumped through to get the pecl bits to stop addressing /tmp I could simply have remounted the /tmp filesystem to allow execution:

$ sudo mount -o remount,exec /tmp
$ sudo pecl install xdebug
$ sudo mount -o remount,defaults,nosuid,nodev,noexec /tmp

This however would have compromised the security that was put in place to stop the possible malicious execution of bits (especially root kits) in /tmp (or /var/tmp).

You have the power (and the knowledge now) so wield it to your benefit.

Tales from the (PHP and Perl) Crypt - AES Encryption in MySQL

I was looking for a way to share encrypted information between two systems where a table in MySQL was the integration point.

The one system is based on php while the other component is a perl daemon.

Let's get cryptic

My first stab at this was a perl based solution using the Crypt::CBC and Crypt::Blowfish libraries plus a shared secret/key. This meant I had to develop a perl script which I called from php to do the encryption which is a rather inelegant solution.

At first I could not find the right libs in php to get this done but later stumbled upon the Mcrypt suit off php and MCrypt perl functions that allow you to do encryption between the two different subsystems.

Unfortunately this means you have double the amount of hassle when it comes to updates and ensuring things Just Work™.

Move it back to the source
Some more checking brought me to the MySQL AES encryption functions that are built into MySQL. They provide the best cryptographic algorithms MySQL currently has to offer and are pretty respectable from a academic encryption perspective.

This means en/decryption is dealt with at one integration point across all languages involved which is much more elegant.

Tales from the Crypt
The MySQL AES encryption functions allow you to en/decrypt data quite easily. To encrypt a string you simply issue the following, assuming your shared secret is lesser-spotted-mountain-squid:

mysql> INSERT INTO test_table (test_column) VALUES(AES_ENCRYPT('this is a super-secret message', 'lesser-spotted-mountain-squid'));
Query OK, 1 row affected (0.09 sec)

mysql> SELECT * FROM test_table;
+----------------------------------+
| test_column                      |
+----------------------------------+
| Aÿ„1
ý#ôärO™é=:Žï   ¼Ñ†kWA |
+----------------------------------+
1 row in set (0.00 sec)

Et voila!

One thing you need to keep in mind is that the field you want to store your encrypted data in must be a MySQL BLOB data type.

Sucking our super secret string back out into a usable form is as simple as:

mysql> SELECT AES_DECRYPT(test_column, 'lesser-spotted-mountain-squid') AS top_secret FROM test_table;
+--------------------------------+
| top_secret                     |
+--------------------------------+
| this is a super-secret message |
+--------------------------------+
1 row in set (0.00 sec)

The security lesson
This is rather obvious but your security is only as strong as the weakest link in the chain. In this specific case I did not want to have clear text data in the db and achieved that amicably.

Because my secret is in clear text in two different systems I am rather exposed if those systems are not as secure as they could be. Lucky for my they are pretty much locked away from daylight so I'm not too concerned.

Baking CakePHP with nginx

I've switched all my web server related infrastructure to nginx which is a high performance HTTP server (amongst other things) which blows apache out of the water (IMNSHO).

If you're a CakePHP user you'll know that it has some special rewriting requirements which can be found in $ROOT/.htaccess:

$ cat .htaccess

RewriteEngine on
RewriteRule    ^$ app/webroot/    [L]
RewriteRule    (.*) app/webroot/$1 [L]

Unfortunately this .htaccess file is an apache mechanism to achieve the URL rewriting that is required to get CakePHP to play nice. The apache rewrite rules do not translate directly to something nginx can use though so some work is required to get things going.

Being lazy (and believing that no problem I discover is unique to me) I had a look a round and found this article by Chris Hartjes which needed a some mods for it to work for my setup:

# CakePHP rewrite rules
location / {
  root /opt/local/html/live_site;
  index index.php;

  # Serve static page immediately
    if (-f $request_filename) {
    break;
  }

  if (!-f $request_filename) {
    rewrite ^/(.+)$ /index.php?url=$1 last;
    break;
  }
}

Here's my complete nginx.conf to give you an idea of how everything fits together:

user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
  worker_connections  1024;
}

http {
  include       etc/nginx/mime.types;
  default_type  application/octet-stream;
  server_names_hash_bucket_size  128;

  sendfile           on;
  keepalive_timeout  20;
  tcp_nodelay        on;

  server {
    listen       80;
    server_name  localhost;
    rewrite_log on;

    #error_page  404              /404.html;
    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
    root   share/nginx/html;
    }

    # Serve static content directly with some caching goodness
    location ~* ^.+.(jpg|jpeg|gif|css|png|js|ico)$ {
      root /opt/local/html/live_site/app/webroot;
      access_log        off;
      expires           1d;
    }

    # CakePHP rewrite rules
    location / {
      root /opt/local/html/live_site;
      index index.php;

      # Serve static pages immediately
      if (-f $request_filename) {
        break;
      }
      
      # Rewrite all other URLs
      if (!-f $request_filename) {
        rewrite ^/(.+)$ /index.php?url=$1 last;
        break;
      }
    }

    # Pass PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    location ~ \.php$ {
    root /opt/local/html/live_site;
    fastcgi_pass   127.0.0.1:9000;
    fastcgi_index  index.php;
    include        /opt/local/etc/nginx/fastcgi_params;
    }
  }
}

PHP5 SimpleXML and CDATA

I am in the process of porting a rather large PHP4 application to PHP5 (just in time for PHP6, yes, yes, I know) for one of my customers. Most of the application is pure imperative programming so the switch has been rather painless.

Unfortunately (for me) they have made rather judicious use of the PHP4 domxml extension libraries which no longer exist in PHP5 (where they have been replaced with the dom extension).

Moving from domxml to dom was straight forward (looping over tags, tags, attributes and text inside tags are addresses differently) so I chose to simply re-write the code to use the new dom extensions instead of opting for a translation library like the one provided by Alexandre Alapetite.

One exception to this was the use of < !--[CDATA[...]]--> blocks which SimpleXML simply seemed to discard when creating a new object.

A quick look around Google (here, here and here) and I found what needed to be done to address SimpleXML's ignorant behaviour.

The SimpleXML constructor allows you to pass in extra libxml2 parameters which allow you to get further functionality out of the library. The one I was interested was of course:

LIBXML_NOCDATA  (integer)
Merge CDATA as text nodes

So, simply changing my constructor from:

$xml = new SimpleXMLElement($text)

to:

$xml = new SimpleXMLElement($text, LIBXML_NOCDATA)

was all that was required for me to gain access to those < !--[CDATA[...]]--> structures.

Aspell, PSPELL, PHP and OS X

Until quite recently there was no way to use Aspell (via the PSPELL PHP libs) on an OS X host that was using the MacPorts system for package management.

This was simply because of the lack of a pspell variant for the php{45} packages.

Port of call
The ports system has the notion of a variant for packages that are conditional modifications of port installation behaviour.

There are two types of variants: user-selected variants and platform variants.

User-selected variants are options selected by a user when a port is installed while platform variants are selected automatically by MacPorts' base according to the OS or hardware platform (Darwin, FreeBSD, Linux, i386, PPC, etc.).

More stuff and less fluff
There are several ways of working this. The first would be to log a ticket at the MacPorts trac with a request to add the variant.

Depending on the package maintainer's load you may be a response pretty quickly. I've generally gotten something back within days of logging the ticket.

In the meantime your universe cannot come to a halt waiting for someone else to add the next greatest thing as a variant to your favourite package. So here's some manual steps to get things up and running in the meantime:

• Install Aspell
  
• Recompile and install PHP with the required PSPELL support
  
• Check php to ensure the new PSPELL libs are active
  
• Do a simple test to see if everything is working as it should
  

Install Aspell
I'll assume you're using MacPorts for your your package management on your OS X host.

Grab the aspell application, libs and whichever dictionaries catch your fancy:

$ sudo port install aspell aspell-dict-en


Be sure to install at least one dictionary or your spell checking days will be rather deflated.

Recompile and install PHP with the required PSPELL support
To manually add a compilation flag you need to edit the Portfile that comes with your installed PHP version. Mine is located at:

/opt/local/var/macports/sources/rsync.macports.org/release/ports/www/php5/Portfile

Edit the Portfile and add “–with-pspell=${prefix}” to configure.args. You can then re-ininstall PHP and it should now use the modified Portfile to compile PHP.

Check php to ensure the new PSPELL libs are active
Use the following script from the command line to determine if your PHP was re-installed with the required PSPELL bits enabled:

$ php -r 'phpinfo();' | grep PSpell
PSpell Support => enabled

Do a simple test to see if everything is working as it should
You should be able to just use the example from the PHP documentation page to ensure everything is fine:

$ cat /tmp/t_pspell.php

$ php -f /tmp/t_pspell.php
Sorry, wrong spelling

The packaging gods exist!
A few days after creating this ticket on the MacPorts trac I got a response from the package maintainer informing me that the variant had been added to all the relevant PHP packages.

Cool!

If your ports distribution files are up-to-date you should now be able to do the following to see which variants are available for your PHP version of choice:

$ port info php5
php5 5.2.5, Revision 2, www/php5 (Variants: universal, darwin_6, darwin_7, macosx, apache, apache2, fastcgi, gmp, imap, pspell, tidy, mssql, snmp, macports_snmp, mysql3, mysql4, mysql5, oracle, postgresql, sqlite, ipc, pcntl, pear, readline, sockets)
http://www.php.net/

PHP is a widely-used general-purpose scripting language that is especially suited for developing web sites, but can also be used for command-line scripting.

Library Dependencies: libxml2, libxslt, openssl, zlib, bzip2, libiconv, expat, gettext, tiff, mhash, libmcrypt, curl, pcre, jpeg, libpng, freetype
Platforms: darwin freebsd
Maintainers: ryandesign@macports.org jwa@macports.org

Now that pspell is listed as a variant you can install PHP with this variant by doing the following, after removing previous PHP version:

$ sudo port install php5 +pspell