Re: [Duplicity-talk] Why is duplicity asking for decryption passphrase on --encrypt-sign-key?

[Felix Fontein]

Hi,

I've set up two GPG keys for duplicity, one is just a public key for
encryption, and the other a public+private key pair (without password)
for signing. This worked fine for a long time, until I upgraded
duplicity to 0.7.14: since this version, incremental update always
spits out error messages:

Error processing remote manifest 
(duplicity-inc.20171025T020003Z.to.20171026T020004Z.manifest.gpg): GPG Failed, 
see log below:
===== Begin GnuPG log =====
gpg: encrypted with 4096-bit RSA key, ID xxxxxxxxxxxxx, created 20xx-xx-xx
"XXXXX <address@hidden>"
gpg: decryption failed: No secret key
===== End GnuPG log =====

(I think this is because of commit 1252:
https://bazaar.launchpad.net/~duplicity-team/duplicity/0.8-series/revision/1252/duplicity/collections.py)

It looks like duplicity tries to compare the remote and local manifest
(by calling check_last_manifest(), which calls
BackupSet.check_manifests, which in turn calls
BackupSet.get_remote_manifest(), which was modified by the above
change). The code calling check_last_manifest():

  if not globals.restart:
    # only ask for a passphrase if there was a previous backup
    if col_stats.all_backup_chains:
      globals.gpg_profile.passphrase = get_passphrase(1, action)
    check_last_manifest(col_stats)  # not needed for full backup
  incremental_backup(sig_chain)

This seems to be the same place which also asks for the passphrase. And
also for me, getting this error (which results in an email by cron) for
every incremental backup is really annoying.

Why does duplicity actually try to compare the latest local manifest to
its remote version? If it wouldn't do that, neither the passphrase nor
a private encryption key would be necessary.

Cheers,
Felix



On Thu, 26 Oct 2017 17:16:07 -0400
Scott Hannahs via Duplicity-talk <address@hidden> wrote:

> No there is no need to store a passphrase on the disk.  Make a key
> specifically for encrypting  duplicity backups.  Then the public key
> can be used for encrypting the backups without need of a passphrase.
> Unless the local manifest gets corrupted and a new manifest has to be
> downloaded and decrypted you should not need the private key for
> backups either incremental or full.
> > On Oct 26, 2017, at 3:30 PM, Michael Gardner via Duplicity-talk
> > <address@hidden> wrote:
> > 
> > Any ideas? Does everyone who runs duplicity incr as a cron job just
> > store the passphrase on disk?