RPM/Sign

How to sign your custom RPM package with GPG Key

Introduction

GnuPG stands for GNU Privacy Guard and is GNU's tool for secure communication and data storage. It can be used to encrypt data and to create digital signatures. It includes an advanced key management facility and is compliant with the proposed OpenPGP Internet standard as described in RFC 2440. As such, it is aimed to be compatible with PGP from NAI, Inc.

After building your custom RPM package, it's a good idea to sign the package with your own GPG Key to make sure the package is authentic.

In this HOWTO, I'll cover how to generate your own gpg key pair and sign your custom RPM package with that key.

First create a hidden directory called '.gnupg' in your home directory

cd ~
mkdir .gnupg

Otherwise, you might get following error message:

gpg: failed to create temporary file `/home/tchung/.gnupg/.#lk0x7b49a8.tchung-fc3.5462': No such file or directory
gpg: keyblock resource `/home/tchung/.gnupg/secring.gpg': general error
gpg: failed to create temporary file `/home/tchung/.gnupg/.#lk0x7b4cb0.tchung-fc3.5462': No such file or directory
gpg: keyblock resource `/home/tchung/.gnupg/pubring.gpg': general error

Generate gpg key pair (public key and private key)

gpg --gen-key
gpg (GnuPG) 1.2.6; Copyright (C) 2004 Free Software Foundation, Inc.
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions. See the file COPYING for details.
 
gpg: keyring `/home/tchung/.gnupg/secring.gpg' created
gpg: keyring `/home/tchung/.gnupg/pubring.gpg' created
Please select what kind of key you want:
   (1) DSA and ElGamal (default)
   (2) DSA (sign only)
   (4) RSA (sign only)
Your selection? 1
DSA keypair will have 1024 bits.
About to generate a new ELG-E keypair.
              minimum keysize is  768 bits
              default keysize is 1024 bits
    highest suggested keysize is 2048 bits
What keysize do you want? (1024) 1024
Requested keysize is 1024 bits
Please specify how long the key should be valid.
         0 = key does not expire
        = key expires in n days
      w = key expires in n weeks
      m = key expires in n months
      y = key expires in n years
Key is valid for? (0) 0
Key does not expire at all
Is this correct (y/n)? y
                         
You need a User-ID to identify your key; the software constructs the user id
from Real Name, Comment and Email Address in this form:
    "Heinrich Heine (Der Dichter) <heinrichh@duesseldorf.de>"
 
Real name: Thomas Chung
Email address: tchung@fedoranews.org
Comment:
You selected this USER-ID:
    "Thomas Chung <tchung@fedoranews.org>"
 
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
You need a Passphrase to protect your secret key.
 
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
+++++++++++++.++++++++++++++++++++++++++++++++++++++++++++++++++..+++++
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
++++++++++++++++..++++++++++++++++++++.+++++++++++++++>+++++...+++++^^^
gpg: /home/tchung/.gnupg/trustdb.gpg: trustdb created
public and secret key created and signed.
key marked as ultimately trusted.
 
pub  1024D/23A254D4 2005-01-06 Thomas Chung <tchung@fedoranews.org>
    Key fingerprint = 9D71 B237 3AE2 B54A B62D  5DC7 2758 9842 23A2 54D4
sub  1024g/D08816E2 2005-01-06

Now that you've generated gpg keys, you can see the list in your key ring by typing:

gpg --list-keys
/home/tchung/.gnupg/pubring.gpg
-------------------------------
pub  1024D/23A254D4 2005-01-06 Thomas Chung <tchung@fedoranews.org>
sub  1024g/D08816E2 2005-01-06

If you get 'gpg: WARNING: using insecure memory!' message
try 'setuid(root) permission on the gpg binary:

$ sudo chmod 4755 /usr/bin/gpg

To extract or export your public key from your key ring to a text file.

gpg --export -a 'Thomas Chung' > RPM-GPG-KEY-tchung

This file is necessary to import it to your RPM DB and verify a package with gpg key later on.

If you're planning to share your custom built RPM packages with others, make sure to have your public key file available online in public so they can verify your custom RPM package.

To import your public key to your RPM DB

sudo rpm --import RPM-GPG-KEY-tchung

Password:

Let's verify the list of gpg public keys in RPM DB:

rpm -q gpg-pubkey --qf '%{name}-%{version}-%{release} --> %{summary}\n'
gpg-pubkey-db42a60e-37ea5438 --> gpg(Red Hat, Inc <security@redhat.com>)
gpg-pubkey-4f2a6fd2-3f9d9d3b --> gpg(Fedora Project <fedora@redhat.com>)
gpg-pubkey-23a254d4-41ddbc46 --> gpg(Thomas Chung <tchung@fedoranews.org>)

Final step before the signing, configure your ~/.rpmmacros file to include the following:

%_signature gpg
%_gpg_name  Thomas Chung

gpg_name
%_gpg_name must be the name of the "user" whose key you wish to use to sign your packages.

Now, you're ready to sign your custom RPM package

rpm --addsign gyum-2.0-5.FC3.i386.rpm
Enter pass phrase:
Pass phrase is good.
gyum-2.0-5.FC3.i386.rpm:

I've used '--addsign' since this package was not signed before. If you wish to over write and re-sign the package, use '--resign' option

To check the signature, use following option and watch for 'gpg OK'

rpm --checksig gyum-2.0-5.FC3.i386.rpm
gyum-2.0-5.FC3.i386.rpm: (sha1) dsa sha1 md5 gpg OK

To sign a package during it's been built, simply add '--sign':

rpmbuild -ba --sign

Signing rpms with gpg by Richard Bos

Auteur initial Thomas Chung on 2005-01-06