Support checking signature for pkg bootstrap.

If the pkg.conf is configured with SIGNATURE_TYPE: FINGERPRINTS,
and FINGERPRINTS: /etc/keys/pkg then a pkg.sig file is fetched along
with pkg.txz. The signature contains the signature provided by the
signing server, and the public key. The .sig is the exact output
from the signing server in the following format:

  SIGNATURE
  <openssl signed>
  CERT
  <rsa public key>
  END

The signature is verified with the following logic:

 - If the .sig file is missing, it fails.
 - If the .sig doesn't validate, it fails.
 - If the public key in the .sig is not in the known trusted fingerprints,
   it fails.
 - If the public key is in the revoked key list, it fails.

Approved by:	bapt
MFC after:	2 days
Discussed by:	bapt with des, jonathan, gavin

1 files changed, 2 insertions, 0 deletions

diff --git a/etc/pkg/FreeBSD.conf b/etc/pkg/FreeBSD.conf
index b36d20f..42ef769 100644
--- a/etc/pkg/FreeBSD.conf
+++ b/etc/pkg/FreeBSD.conf
@@ -2,5 +2,7 @@
 FreeBSD: {
   url: "pkg+http://pkg.freebsd.org/${ABI}/latest",
   mirror_type: "srv",
+  signature_type: "fingerprints",
+  fingerprints: "/etc/keys/pkg",
   enabled: "yes"
 }