Signature header

The 2.1 release of RPM had a few improvements in the area of digital package signatures. The usage of PGP has been cleaned up and extended, the signature section in the RPM file format has been made easily extensible with new signature types, and packages can have multiple signatures.

PGP

Legacy usage of PGP in rpm-2.0 was cumbersome, and only supported 1024 bit keys. Both of these problems have been corrected in rpm-2.1.

Whereas previously you needed many rpmrc entries to clue in RPM about keyring locations and such, RPM now behaves as PGP users would expect. The PGPPATH environment variable can be used to specify keyring locations. You can also use a “%_pgpbin” line in your macros file to specify a different value for RPM to use for PGPPATH. If neither of these are used PGP uses its default ($HOME/.pgp).

If you just want to verify packages, you need to supply values for the macros

	%_pgpbin	the path to the pgp executable
	%_signature	the type of signature to use

In order to be able to sign packages, you may also have to supply values for

	%_pgp_name	the pgp signature to use for signing
	%_pgp_path	the path to the key ring

Signing Packages

Signature creation is the same as previous releases: just add a –sign to your build command line. You can sign a package after the package is built with:

	rpm --resign <package>

Using –resign removes any previous signature in the package. To add a signature to a package, leaving all existing signatures use:

	rpm --addsign <package>

RPM always creates MD5 and SIZE signatures when it build packages, which means that packages built without –sign can be “verified” to some extent. The MD5 signature should catch problems like corrupt packages, faulty downloads, etc.

Verifying Package Signatures

Package signature verification is the same as previous releases:

	rpm -K <package>

RPM will verify every signature in the package, which may include more than one PGP signature. The output indicates what types of signatures are being checked. If any checks fail you’ll see a “NOT OK” message, and you should be worried.

If you have a package with PGP signatures, but don’t have PGP installed, but still want to verify it as much as possible, you can do:

	rpm -K --nopgp <package>

That will cause RPM to skip any PGP signatures, but still check any others (currently only MD5 and SIZE).