#!/usr/bin/python

# Copyright (c) 2010 Peter Palfrader
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

# copy a file from the backup server, where the server runs debbackup-ssh-wrap

import sys
import os
import optparse
import re
import subprocess
import syslog
import tempfile
import stat
import hashlib

backuphost="debbackup@storace.debian.org"
block_size = 4096

syslog.openlog(sys.argv[0], syslog.LOG_PID, syslog.LOG_DAEMON)

def info(m):
    syslog.syslog(syslog.LOG_INFO, m)
def croak(m):
    syslog.syslog(syslog.LOG_WARNING, m)
    print >> sys.stderr, m
    sys.exit(1)

sys.stdin.close()

parser = optparse.OptionParser()
parser.set_usage("%prog [<options>] <from_host> <filename> <target>")
(options, args) = parser.parse_args()

if len(args) != 3:
    parser.print_help()
    sys.exit(1)

from_host = args.pop(0)
filename = args.pop(0)
target = args.pop(0)

hostname = os.uname()[1]

# open pipe to backup server
p = subprocess.Popen(["ssh", "-C", backuphost, hostname, "retrieve-file", "pg", from_host, filename], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
p.stdin.close()
f = p.stdout

# read Format line
line = f.readline().rstrip('\n')
if line != "Format: 1":
    croak("Uknown format in line 1 (%s) when getting %s:%s from backup host"%(line, from_host, filename))

# read Status line
line = f.readline().rstrip('\n')
s = line.split(':', 1)
if len(s) != 2:
    croak("Protocol violation when getting %s:%s from backup host (line 2)"%(from_host, filename))
key = s[0]
if key != "Status":
    croak("Protocol violation when getting %s:%s from backup host"%(from_host, filename))
first = s[1].split()[0]
try:
    code = int(first)
except ValueError:
    croak("Invalid code '%s'"%(first))

if code == 404:
    info("Wanted to get %s:%s from backup host, but file does not exist."%(from_host, filename))
    sys.exit(1)
elif code != 200:
    info("Unknown code %d when trying to get %s:%s from backup host"%(code, from_host, filename))

# get rest of the headers
metadata = {}
while True:
    line = f.readline().rstrip('\n')
    if line == "": break
    line = line.strip()
    s = line.split(':', 1)
    if len(s) != 2:
        croak("Protocol violation when getting %s:%s from backup host"%(from_host, filename))
    key = s[0]
    value = s[1].lstrip()
    metadata[key] = value

# verify we like them
for k in ['Size', 'SHA-512']:
    if not k in metadata:
        croak("Key %s not found in metadata when getting %s:%s from backup host"%(k, from_host, filename))
try:
    size = int(metadata['Size'])
except ValueError:
    croak("Invalid size '%s'"%(size))
checksum = metadata['SHA-512']

info("Getting %s:%s from backup host (size %d)."%(from_host, filename, size))

target=os.path.abspath(target)
targetdir=os.path.dirname(target)
tmp = tempfile.NamedTemporaryFile(dir=targetdir, prefix=".tmp.pg-receive-file-from-backup-%s:%s."%(from_host, filename))

# read file
running_size = 0
digest = hashlib.sha512()
while True:
    buf = f.read(block_size)
    if not buf: break
    digest.update(buf)
    tmp.write(buf)

    running_size += len(buf)
    if running_size > size:
        croak("Size mismatch")
f.close()
p.wait()
tmp.flush()

file_size = os.stat(tmp.name)[stat.ST_SIZE]

# check size and checksum
if file_size != size:
    croak("Size mismatch")
if file_size != running_size:
    croak("Size mismatch. WTF.")
if checksum != digest.hexdigest():
    croak("Checksum mismatch. WTF.")

# and try to link
try:
    os.link(tmp.name, target)
except Exception, e:
    croak("Failed at linking to target: %s"%(e))

tmp.close()
info("Successfully stored %s."%(target))


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