All RedHat EnterpriseLinux packages are signed with the RedHat GPG key. GPG stands for GNU Privacy Guard, or GnuPG, a free software package used for ensuring the authenticity of distributed files. For example, a private key (secret key) locks the package while the public key unlocks and verifies the package. If the public key distributed by RedHat EnterpriseLinux does not match the private key during RPM verification, the package may have been altered and therefore cannot be trusted.
The RPM utility within RedHat EnterpriseLinux6 automatically tries to verify the GPG signature of an RPM package before installing it. If the RedHat GPG key is not installed, install it from a secure, static location, such as a RedHat installation CD-ROM or DVD.
Assuming the disc is mounted in /mnt/cdrom, use the following command as the root user to import it into the keyring (a database of trusted keys on the system):
~]# rpm --import /mnt/cdrom/RPM-GPG-KEYNow, the RedHat GPG key is located in the /etc/pki/rpm-gpg/ directory.
To display a list of all keys installed for RPM verification, execute the following command:
~]# rpm -qa gpg-pubkey*gpg-pubkey-db42a60e-37ea5438To display details about a specific key, use the rpm -qi command followed by the output from the previous command, as in this example:
~]# rpm -qi gpg-pubkey-db42a60e-37ea5438Name : gpg-pubkey Relocations: (not relocatable)Version : 2fa658e0 Vendor: (none)Release : 45700c69 Build Date: Fri 07 Oct 2011 02:04:51 PM CESTInstall Date: Fri 07 Oct 2011 02:04:51 PM CEST Build Host: localhostGroup : Public Keys Source RPM: (none)[output truncated]It is extremely important to verify the signature of the RPM files before installing them to ensure that they have not been altered from the original source of the packages. To verify all the downloaded packages at once, issue the following command:
~]# rpm -K /root/updates/*.rpmalsa-lib-1.0.22-3.el6.x86_64.rpm: rsa sha1 (md5) pgp md5 OKalsa-utils-1.0.21-3.el6.x86_64.rpm: rsa sha1 (md5) pgp md5 OKaspell-0.60.6-12.el6.x86_64.rpm: rsa sha1 (md5) pgp md5 OKFor each package, if the GPG key verifies successfully, the command returns gpg OK. If it does not, make sure you are using the correct RedHat public key, as well as verifying the source of the content. Packages that do not pass GPG verification should not be installed, as they may have been altered by a third party.
After verifying the GPG key and downloading all the packages associated with the errata report, install the packages as root at a shell prompt.
Alternatively, you may use the Yum utility to verify signed packages. Yum provides secure package management by enabling GPG signature verification on GPG-signed packages to be turned on for all package repositories (that is, package sources), or for individual repositories. When signature verification is enabled, Yum will refuse to install any packages not GPG-signed with the correct key for that repository. This means that you can trust that the RPM packages you download and install on your system are from a trusted source, such as RedHat, and were not modified during transfer.
In order to have automatic GPG signature verification enabled when installing or updating packages via Yum, ensure you have the following option defined under the [main] section of your /etc/yum.conf file:
gpgcheck=1
