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Use built in duplicity encryption (GPG) for backups, closes #362, closes #363 

[Josh merged some subsequent commits:]

* Guard via idempotency against termination between migration operations
* Final corrections and tweaks
* Pass passphrase through to all duplicity calls

Empirical evidence (a failed cron job) shows that cleanup requires the
passphrase (so it presumably needs to decrypt metadata), and though
remove-older-than has been working fine without it, it won't do any harm
to set it in case that changes or there are any special cases.

* Add back the archive-dir override but locate it at STORAGE_ROOT/backup/cache
This commit is contained in:
David Piggott 2015-03-26 12:27:26 +00:00 committed by Joshua Tauberer
parent 298e19598b
commit 4232245546
2 changed files with 98 additions and 70 deletions
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163
management/backup.py
View File

@ -2,11 +2,10 @@
# This script performs a backup of all user data:
# 1) System services are stopped while a copy of user data is made.
# 2) An incremental backup is made using duplicity into the
# directory STORAGE_ROOT/backup/duplicity.
# 2) An incremental encrypted backup is made using duplicity into the
# directory STORAGE_ROOT/backup/encrypted. The password used for
# encryption is stored in backup/secret_key.txt.
# 3) The stopped services are restarted.
# 4) The backup files are encrypted with a long password (stored in
# backup/secret_key.txt) to STORAGE_ROOT/backup/encrypted.
# 5) STORAGE_ROOT/backup/after-backup is executd if it exists.
import os, os.path, shutil, glob, re, datetime
@ -14,13 +13,13 @@ import dateutil.parser, dateutil.relativedelta, dateutil.tz
from utils import exclusive_process, load_environment, shell
# destroy backups when the most recent increment in the chain
# Destroy backups when the most recent increment in the chain
# that depends on it is this many days old.
keep_backups_for_days = 3
def backup_status(env):
# What is the current status of backups?
# Loop through all of the files in STORAGE_ROOT/backup/duplicity to
# Loop through all of the files in STORAGE_ROOT/backup/encrypted to
# get a list of all of the backups taken and sum up file sizes to
# see how large the storage is.
@ -36,10 +35,10 @@ def backup_status(env):
return "%d hours, %d minutes" % (rd.hours, rd.minutes)
backups = { }
basedir = os.path.join(env['STORAGE_ROOT'], 'backup/duplicity/')
encdir = os.path.join(env['STORAGE_ROOT'], 'backup/encrypted/')
os.makedirs(basedir, exist_ok=True) # os.listdir fails if directory does not exist
for fn in os.listdir(basedir):
backup_dir = os.path.join(env["STORAGE_ROOT"], 'backup')
backup_encrypted_dir = os.path.join(backup_dir, 'encrypted')
os.makedirs(backup_encrypted_dir, exist_ok=True) # os.listdir fails if directory does not exist
for fn in os.listdir(backup_encrypted_dir):
m = re.match(r"duplicity-(full|full-signatures|(inc|new-signatures)\.(?P<incbase>\d+T\d+Z)\.to)\.(?P<date>\d+T\d+Z)\.", fn)
if not m: raise ValueError(fn)
@ -53,15 +52,9 @@ def backup_status(env):
"full": m.group("incbase") is None,
"previous": m.group("incbase"),
"size": 0,
"encsize": 0,
}
backups[key]["size"] += os.path.getsize(os.path.join(basedir, fn))
# Also check encrypted size.
encfn = os.path.join(encdir, fn + ".enc")
if os.path.exists(encfn):
backups[key]["encsize"] += os.path.getsize(encfn)
backups[key]["size"] += os.path.getsize(os.path.join(backup_encrypted_dir, fn))
# Ensure the rows are sorted reverse chronologically.
# This is relied on by should_force_full() and the next step.
@ -78,7 +71,7 @@ def backup_status(env):
break
incremental_count += 1
incremental_size += bak["size"]
# Predict how many more increments until the next full backup,
# and add to that the time we hold onto backups, to predict
# how long the most recent full backup+increments will be held
@ -106,9 +99,8 @@ def backup_status(env):
bak["deleted_in"] = deleted_in
return {
"directory": basedir,
"encpwfile": os.path.join(env['STORAGE_ROOT'], 'backup/secret_key.txt'),
"encdirectory": encdir,
"directory": backup_encrypted_dir,
"encpwfile": os.path.join(backup_dir, 'secret_key.txt'),
"tz": now.tzname(),
"backups": backups,
}
@ -137,10 +129,62 @@ def perform_backup(full_backup):
exclusive_process("backup")
# Ensure the backup directory exists.
backup_dir = os.path.join(env["STORAGE_ROOT"], 'backup')
backup_cache_dir = os.path.join(backup_dir, 'cache')
backup_encrypted_dir = os.path.join(backup_dir, 'encrypted')
# In an older version of this script, duplicity was called
# such that it did not encrypt the backups it created (in
# backup/duplicity), and instead openssl was called separately
# after each backup run, creating AES256 encrypted copies of
# each file created by duplicity in backup/encrypted.
#
# We detect the transition by the presence of backup/duplicity
# and handle it by 'dupliception': we move all the old *un*encrypted
# duplicity files up out of the backup/duplicity directory (as
# backup/ is excluded from duplicity runs) in order that it is
# included in the next run, and we delete backup/encrypted (which
# duplicity will output files directly to, post-transition).
#
# This achieves two things:
# 1. It preserves the pre-transition unencrypted backup files
# within the encrypted backups we will immediately create, so
# that they are kept until the next full backup is triggered.
# (it is because those backups will be encrypted that we take
# the old *un*encrypted backups, not the duplicates encrypted
# with openssl).
# 2. It results in backup_status() being called on a non-existant
# backup/encrypted directory, which will trigger a full backup
# (though duplicity ought to do one anyway as it ought not
# recognise the old openssl encrypted .enc files, if we *had*
# left them there). More to the point it clears out those .enc
# files which are now redundant, thereby gaining disk space and
# preventing backup_status() getting terribly confused by their
# presence.
#
# A note about disk use:
# At no point in the transition will we use more disk space than
# was used pre-transition, because by deleting the openssl
# encrypted duplicates we decrease by more* than half the disk
# space used, while the addition by 'dupliception' of the old
# *un*encrypted backups takes less space than we gained from
# dropping the openssl encrypted duplicates.
#
# A note about the status page post-upgrade but pre-transition:
# Between the point that the new code is deployed and when the first
# daily backup is run, there will be a subtle change in the
# behaviour of the web control panel's backup status page, in that
# it will only sum the size of the encrypted backups when reporting
# the total size on disk i.e. it will not consider the unencrypted
# originals.
#
# *the openssl encrypted duplicates were base64 encrypted, hence
# accounting for more than half of the space used.
backup_duplicity_dir = os.path.join(backup_dir, 'duplicity')
os.makedirs(backup_duplicity_dir, exist_ok=True)
migrated_unencrypted_backup_dir = os.path.join(env["STORAGE_ROOT"], "migrated_unencrypted_backup")
if os.path.isdir(backup_duplicity_dir):
shutil.rmtree(backup_encrypted_dir)
shutil.move(backup_duplicity_dir, migrated_unencrypted_backup_dir)
# On the first run, always do a full backup. Incremental
# will fail. Otherwise do a full backup when the size of
@ -152,70 +196,55 @@ def perform_backup(full_backup):
shell('check_call', ["/usr/sbin/service", "dovecot", "stop"])
shell('check_call', ["/usr/sbin/service", "postfix", "stop"])
env_with_passphrase = { "PASSPHRASE" :
open(os.path.join(backup_dir, 'secret_key.txt')).read()
}
# Update the backup mirror directory which mirrors the current
# STORAGE_ROOT (but excluding the backups themselves!).
try:
shell('check_call', [
"/usr/bin/duplicity",
"full" if full_backup else "incr",
"--no-encryption",
"--archive-dir", "/tmp/duplicity-archive-dir",
"--name", "mailinabox",
"--archive-dir", backup_cache_dir,
"--exclude", backup_dir,
"--volsize", "100",
"--verbosity", "warning",
"--volsize", "250",
env["STORAGE_ROOT"],
"file://" + backup_duplicity_dir
])
"file://" + backup_encrypted_dir
],
env_with_passphrase)
finally:
# Start services again.
shell('check_call', ["/usr/sbin/service", "dovecot", "start"])
shell('check_call', ["/usr/sbin/service", "postfix", "start"])
if os.path.isdir(migrated_unencrypted_backup_dir):
shutil.rmtree(migrated_unencrypted_backup_dir)
# Remove old backups. This deletes all backup data no longer needed
# from more than 31 days ago. Must do this before destroying the
# cache directory or else this command will re-create it.
# from more than 3 days ago.
shell('check_call', [
"/usr/bin/duplicity",
"remove-older-than",
"%dD" % keep_backups_for_days,
"--archive-dir", "/tmp/duplicity-archive-dir",
"--name", "mailinabox",
"--archive-dir", backup_cache_dir,
"--force",
"--verbosity", "warning",
"file://" + backup_duplicity_dir
])
"file://" + backup_encrypted_dir
],
env_with_passphrase)
# Remove duplicity's cache directory because it's redundant with our backup directory.
shutil.rmtree("/tmp/duplicity-archive-dir")
# Encrypt all of the new files.
backup_encrypted_dir = os.path.join(backup_dir, 'encrypted')
os.makedirs(backup_encrypted_dir, exist_ok=True)
for fn in os.listdir(backup_duplicity_dir):
fn2 = os.path.join(backup_encrypted_dir, fn) + ".enc"
if os.path.exists(fn2): continue
# Encrypt the backup using the backup private key.
shell('check_call', [
"/usr/bin/openssl",
"enc",
"-aes-256-cbc",
"-a",
"-salt",
"-in", os.path.join(backup_duplicity_dir, fn),
"-out", fn2,
"-pass", "file:%s" % os.path.join(backup_dir, "secret_key.txt"),
])
# The backup can be decrypted with:
# openssl enc -d -aes-256-cbc -a -in latest.tgz.enc -out /dev/stdout -pass file:secret_key.txt | tar -z
# Remove encrypted backups that are no longer needed.
for fn in os.listdir(backup_encrypted_dir):
fn2 = os.path.join(backup_duplicity_dir, fn.replace(".enc", ""))
if os.path.exists(fn2): continue
os.unlink(os.path.join(backup_encrypted_dir, fn))
# From duplicity's manual:
# "This should only be necessary after a duplicity session fails or is
# aborted prematurely."
# That may be unlikely here but we may as well ensure we tidy up if
# that does happen - it might just have been a poorly timed reboot.
shell('check_call', [
"/usr/bin/duplicity",
"cleanup",
"--archive-dir", backup_cache_dir,
"--force",
"file://" + backup_encrypted_dir
],
env_with_passphrase)
# Execute a post-backup script that does the copying to a remote server.
# Run as the STORAGE_USER user, not as root. Pass our settings in

5
management/templates/system-backup.html
View File

@ -54,7 +54,7 @@ function show_system_backup() {
"GET",
{ },
function(r) {
$('#backup-location').text(r.encdirectory);
$('#backup-location').text(r.directory);
$('#backup-encpassword-file').text(r.encpwfile);
$('#backup-status tbody').html("");
@ -72,7 +72,7 @@ function show_system_backup() {
tr.append( $('<td/>').text(b.date_str + " " + r.tz) );
tr.append( $('<td/>').text(b.date_delta + " ago") );
tr.append( $('<td/>').text(b.full ? "full" : "increment") );
tr.append( $('<td style="text-align: right"/>').text( nice_size(b.encsize)) );
tr.append( $('<td style="text-align: right"/>').text( nice_size(b.size)) );
if (b.deleted_in)
tr.append( $('<td/>').text(b.deleted_in) );
else
@ -80,7 +80,6 @@ function show_system_backup() {
$('#backup-status tbody').append(tr);
total_disk_size += b.size;
total_disk_size += b.encsize;
}
$('#backup-total-size').text(nice_size(total_disk_size));