Setting up GnuPG (GPG) for use with PHP

Step 1 (failed):

$ pecl install gnupg

downloading gnupg-1.3.1.tar ...
Starting to download gnupg-1.3.1.tar (-1 bytes)
.............done: 124,416 bytes
5 source files, building
running: phpize
Configuring for:
PHP Api Version: 20020918
Zend Module Api No: 20020429
Zend Extension Api No: 20050606
`phpize' failed

Step 2 (success). Some information drawn from http://www.php.net/manual/en/install.pecl.php, a basic tutorial on how to install PECL extensions.

$ cd /usr/lib64/php/extensions

(This is where my PHP extensions [files with .so extension] are stored)

$ pecl download gnupg
$ tar -zxvf gnupg-1.3.1.tgz
$ cd gnupg-1.3.1/
$ phpize
$ ./configure
$ make
$ make install

"gnupg.so" now appears in /usr/lib64/php/extensions
Now I need to install the extension in the php.ini file

$ whereis php.ini

/etc/php.ini

$ vi /etc/php.ini

Find the list of extensions in php.ini, in my case headed by "[extension section]". Add "extension=gnupg.so" to the end of the list, save and exit.
Now I need to restart apache so the extension takes effect.

$ apache2ctl graceful

Now do some PHP coding. Assumes you have GnuPG (gpg) installed, and have set up your key pair ("gpg --gen-key"). Some of these steps might be unnecessary, but after hours of fiddling around, I'm not about to walk through it again and find the essential ones.

/* Change this to your own path */
putenv("GNUPGHOME=/home/bch36/.gnupg/");

$encrypted_data = file_get_contents("encrypted.gpg");

$res = gnupg_init();

gnupg_seterrormode($res,GNUPG_ERROR_WARNING);

/* Change this to your own fingerprint. Find your fingerprint by running "gpg --fingerprint" from the commandline. Comment this out when everything works. */
print_r(gnupg_keyinfo($res,"ASDF1234QWER5678ZXCV9012ASDF3456QWER7890"));

/* Put your own fingerprint and passphrase here. Also, this function will fail unless you see Important Note #1 below */
gnupg_adddecryptkey($res, "ASDF1234QWER5678ZXCV9012ASDF3456QWER7890", "put your secret passphrase here");

/* You'll want to comment this out when everything is working */
echo gnupg_geterror($res);

/* This function will fail unless you see Important Note #2 below */
$plain = gnupg_decrypt($res, $encrypted_data);

Important Notes:
1. To get gnupg_keyinfo() to work, you'll need to let your webserver have some access to your keyring. Do the following (replace "www" with the group that your own webserver runs under):

> cd /home/bch36/.gnupg
> chown :www pubring.gpg trustdb.gpg
> chmod 660 pubring.gpg trustdb.gpg

2. To get gnupg_decrypt() to work, you'll need to grant more access. Note that the webserver will now have access to your secret key! However, if you don't do the following, the gnupg_decrypt() function will fail and you'll get the following warning when printing out gnupg_geterror(): "Warning: gnupg_adddecryptkey() [function.gnupg-adddecryptkey]: get_key failed in ..."

> chown :www secring.gpg
> chmod 660 secring.gpg

As a possible point of interest, I'm only doing decryption because I want a remote webpage to use Javascript to PGP encrypt data and send it to my PHP file, which can then decrypt it. I guess it's a workaround for not having SSL. I'll try to post an entry about the client-side next (Javascript PGP).