X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=restore.pl;fp=restore.pl;h=0000000000000000000000000000000000000000;hb=ff89c9e6f03239f5a671352a29dc647cd284823f;hp=ad1f5949840fc1ef9caa20e7a4816d6b6fff1e36;hpb=315e528bb31f6a1abfda0bd1e3c81d982d6ead44;p=cumulus.git diff --git a/restore.pl b/restore.pl deleted file mode 100755 index ad1f594..0000000 --- a/restore.pl +++ /dev/null @@ -1,429 +0,0 @@ -#!/usr/bin/perl -w -# -# Proof-of-concept/reference decoder for LBS-format backup snapshots. -# -# This decoder aims to decompress an LBS snapshot. It is not meant to be -# particularly efficient, but should be a small and portable tool for doing so -# (important for recovering from data loss). It is also meant to serve as a -# check on the snapshot tool and data format itself, and serve as documentation -# for the format. -# -# This decoder does not understand TAR archives; it assumes that all segments -# in the snapshot have already been decompressed, and that objects are -# available simply as files in the filesystem. This simplifies the design. -# -# Limitations: Since this code is probably using 32-bit arithmetic, files -# larger than 2-4 GB may not be properly handled. -# -# Copyright (C) 2007 Michael Vrable - -use strict; -use Digest::SHA1; -use File::Basename; - -my $OBJECT_DIR; # Where are the unpacked objects available? -my $DEST_DIR = "."; # Where should restored files should be placed? -my $RECURSION_LIMIT = 3; # Bound on recursive object references - -my $VERBOSE = 0; # Set to 1 to enable debugging messages - -############################ CHECKSUM VERIFICATION ############################ -# A very simple layer for verifying checksums. Checksums may be used on object -# references directly, and can also be used to verify entire reconstructed -# files. -# -# A checksum to verify is given in the form "algorithm=hexdigest". Given such -# a string, we can construct a "verifier" object. Bytes can be incrementally -# added to the verifier, and at the end a test can be made to see if the -# checksum matches. The caller need not know what algorithm is used. However, -# at the moment we only support SHA-1 for computing digest (algorith name -# "sha1"). -sub verifier_create { - my $checksum = shift; - - if ($checksum !~ m/^(\w+)=([0-9a-f]+)$/) { - die "Malformed checksum: $checksum"; - } - my ($algorithm, $hash) = ($1, $2); - if ($algorithm ne 'sha1') { - die "Unsupported checksum algorithm: $algorithm"; - } - - my %verifier = ( - ALGORITHM => $algorithm, - HASH => $hash, - DIGESTER => new Digest::SHA1 - ); - - return \%verifier; -} - -sub verifier_add_bytes { - my $verifier = shift; - my $digester = $verifier->{DIGESTER}; - my $data = shift; - - $digester->add($data); -} - -sub verifier_check { - my $verifier = shift; - my $digester = $verifier->{DIGESTER}; - - my $newhash = $digester->hexdigest(); - if ($VERBOSE && $verifier->{HASH} ne $newhash) { - print STDERR "Verification failure: ", - $newhash, " != ", $verifier->{HASH}, "\n"; - } - return ($verifier->{HASH} eq $newhash); -} - -################################ OBJECT ACCESS ################################ -# The base of the decompressor is the object reference layer. See ref.h for a -# description of the format for object references. These functions will parse -# an object reference, locate the object data from the filesystem, perform any -# necessary integrity checks (if a checksum is included), and return the object -# data. -sub load_ref { - # First, try to parse the object reference string into constituent pieces. - # The format is segment/object(checksum)[range]. Both the checksum and - # range are optional. - my $ref_str = shift; - - if ($ref_str !~ m/^([-0-9a-f]+)\/([0-9a-f]+)(\(\S+\))?(\[\S+\])?$/) { - die "Malformed object reference: $ref_str"; - } - - my ($segment, $object, $checksum, $range) = ($1, $2, $3, $4); - - # Next, use the segment/object components to locate and read the object - # contents from disk. - open OBJECT, "<", "$OBJECT_DIR/$segment/$object" - or die "Unable to open object $OBJECT_DIR/$segment/$object: $!"; - my $contents = join '', ; - close OBJECT; - - # If a checksum was specified in the object reference, verify the object - # integrity by computing a checksum of the read data and comparing. - if ($checksum) { - $checksum =~ m/^\((\S+)\)$/; - my $verifier = verifier_create($1); - verifier_add_bytes($verifier, $contents); - if (!verifier_check($verifier)) { - die "Integrity check for object $ref_str failed"; - } - } - - # If a range was specified, then only a subset of the bytes of the object - # are desired. Extract just the desired bytes. - if ($range) { - if ($range !~ m/^\[(\d+)\+(\d+)\]$/) { - die "Malformed object range: $range"; - } - - my $object_size = length $contents; - my ($start, $length) = ($1 + 0, $2 + 0); - if ($start >= $object_size || $start + $length > $object_size) { - die "Object range $range falls outside object bounds " - . "(actual size $object_size)"; - } - - $contents = substr $contents, $start, $length; - } - - return $contents; -} - -############################### FILE PROCESSING ############################### -# Process the metadata for a single file. process_file is the main entry -# point; it should be given a list of file metadata key/value pairs. -# iterate_objects is a helper function used to iterate over the set of object -# references that contain the file data for a regular file. - -sub parse_int { - my $str = shift; - if ($str =~ /^0/) { - return oct($str); - } else { - return $str + 0; - } -} - -sub uri_decode { - my $str = shift; - $str =~ s/%([0-9a-f]{2})/chr(hex($1))/ge; - return $str; -} - -sub iterate_objects { - my $callback = shift; # Function to be called for each reference - my $arg = shift; # Argument passed to callback - my $text = shift; # Whitespace-separate list of object references - - # Simple limit to guard against cycles in the object references - my $recursion_level = shift || 0; - if ($recursion_level >= $RECURSION_LIMIT) { - die "Recursion limit reached"; - } - - # Split the provided text at whitespace boundaries to produce the list of - # object references. If any of these start with "@", then we have an - # indirect reference, and must look up that object and call iterate_objects - # with the contents. - my $obj; - foreach $obj (split /\s+/, $text) { - next if $obj eq ""; - if ($obj =~ /^@(\S+)$/) { - my $indirect = load_ref($1); - iterate_objects($callback, $arg, $indirect, $recursion_level + 1); - } else { - &$callback($arg, $obj); - } - } -} - -sub obj_callback { - my $state = shift; - my $obj = shift; - my $data = load_ref($obj); - print FILE $data - or die "Error writing file data: $!"; - verifier_add_bytes($state->{VERIFIER}, $data); - $state->{BYTES} += length($data); -} - -# Extract the contents of a regular file by concatenating all the objects that -# comprise it. -sub unpack_file { - my $name = shift; - my %info = @_; - my %state = (); - - if (!defined $info{data}) { - die "File contents not specified for $name"; - } - if (!defined $info{checksum} || !defined $info{size}) { - die "File $name is missing checksum or size"; - } - - $info{size} = parse_int($info{size}); - - # Open the file to be recreated. The data will be written out by the call - # to iterate_objects. - open FILE, ">", "$DEST_DIR/$name" - or die "Cannot write file $name: $!"; - - # Set up state so that we can incrementally compute the checksum and length - # of the reconstructed data. Then iterate over all objects in the file. - $state{VERIFIER} = verifier_create($info{checksum}); - $state{BYTES} = 0; - iterate_objects(\&obj_callback, \%state, $info{data}); - - close FILE; - - # Verify that the reconstructed object matches the size/checksum we were - # given. - if (!verifier_check($state{VERIFIER}) || $state{BYTES} != $info{size}) { - die "File reconstruction failed for $name: size or checksum differs"; - } -} - -sub process_file { - my %info = @_; - - if (!defined($info{name})) { - die "Filename not specified in metadata block"; - } - - my $type = $info{type}; - - my $filename = uri_decode($info{name}); - print "$filename\n" if $VERBOSE; - - # Restore the specified file. How to do so depends upon the file type, so - # dispatch based on that. - my $dest = "$DEST_DIR/$filename"; - if ($type eq '-') { - # Regular file - unpack_file($filename, %info); - } elsif ($type eq 'd') { - # Directory - if ($filename ne '.') { - mkdir $dest or die "Cannot create directory $filename: $!"; - } - } elsif ($type eq 'l') { - # Symlink - if (!defined($info{contents})) { - die "Symlink $filename has no value specified"; - } - my $contents = uri_decode($info{contents}); - symlink $contents, $dest - or die "Cannot create symlink $filename: $!"; - - # TODO: We can't properly restore all metadata for symbolic links - # (attempts to do so below will change metadata for the pointed-to - # file). This should be later fixed, but for now we simply return - # before getting to the restore metadata step below. - return; - } elsif ($type eq 'p' || $type eq 's' || $type eq 'c' || $type eq 'b') { - # Pipe, socket, character device, block device. - # TODO: Handle these cases. - print STDERR "Ignoring special file $filename of type $type\n"; - return; - } else { - die "Unknown file type '$type' for file $filename"; - } - - # Restore mode, ownership, and any other metadata for the file. This is - # split out from the code above since the code is the same regardless of - # file type. - my $mtime = $info{mtime} || time(); - utime time(), $mtime, $dest - or warn "Unable to update mtime for $dest"; - - my $uid = -1; - my $gid = -1; - if (defined $info{user}) { - my @items = split /\s/, $info{user}; - $uid = parse_int($items[0]) if exists $items[0]; - } - if (defined $info{group}) { - my @items = split /\s/, $info{group}; - $gid = parse_int($items[0]) if exists $items[0]; - } - chown $uid, $gid, $dest - or warn "Unable to change ownership for $dest"; - - if (defined $info{mode}) { - my $mode = parse_int($info{mode}); - chmod $mode, $dest - or warn "Unable to change permissions for $dest"; - } -} - -########################### METADATA LIST PROCESSING ########################## -# Process the file metadata listing provided, and as information for each file -# is extracted, pass it to process_file. This will recursively follow indirect -# references to other metadata objects. -sub process_metadata { - my ($metadata, $recursion_level) = @_; - - # Check recursion; this will prevent us from infinitely recursing on an - # indirect reference which loops back to itself. - $recursion_level ||= 0; - if ($recursion_level >= $RECURSION_LIMIT) { - die "Recursion limit reached"; - } - - # Split the metadata into lines, then start processing each line. There - # are two primary cases: - # - Lines starting with "@" are indirect references to other metadata - # objects. Recursively process that object before continuing. - # - Other lines should come in groups separated by a blank line; these - # contain metadata for a single file that should be passed to - # process_file. - # Note that blocks of metadata about a file cannot span a boundary between - # metadata objects. - my %info = (); - my $line; - my $last_key; - foreach $line (split /\n/, $metadata) { - # If we find a blank line or a reference to another block, process any - # data for the previous file first. - if ($line eq '' || $line =~ m/^@/) { - process_file(%info) if %info; - %info = (); - undef $last_key; - next if $line eq ''; - } - - # Recursively handle indirect metadata blocks. - if ($line =~ m/^@(\S+)$/) { - print "Indirect: $1\n" if $VERBOSE; - my $indirect = load_ref($1); - process_metadata($indirect, $recursion_level + 1); - next; - } - - # Try to parse the data as "key: value" pairs of file metadata. Also - # handle continuation lines, which start with whitespace and continue - # the previous "key: value" pair. - if ($line =~ m/^(\w+):\s*(.*)$/) { - $info{$1} = $2; - $last_key = $1; - } elsif ($line =~/^\s/ && defined $last_key) { - $info{$last_key} .= $line; - } else { - print STDERR "Junk in file metadata section: $line\n"; - } - } - - # Process any last file metadata which has not already been processed. - process_file(%info) if %info; -} - -############################### MAIN ENTRY POINT ############################## -# Program start. We expect to be called with a single argument, which is the -# name of the backup descriptor file written by a backup pass. This will name -# the root object in the snapshot, from which we can reach all other data we -# need. - -# Parse command-line arguments. The first (required) is the name of the -# snapshot descriptor file. The backup objects are assumed to be stored in the -# same directory as the descriptor. The second (optional) argument is the -# directory where the restored files should be written; it defaults to "."; -my $descriptor = $ARGV[0]; -unless (defined($descriptor) && -r $descriptor) { - print STDERR "Usage: $0 \n"; - exit 1; -} - -if (defined($ARGV[1])) { - $DEST_DIR = $ARGV[1]; -} - -$OBJECT_DIR = dirname($descriptor); -print "Source directory: $OBJECT_DIR\n" if $VERBOSE; - -# Read the snapshot descriptor to find the root object. Parse it to get a set -# of key/value pairs. -open DESCRIPTOR, "<", $descriptor - or die "Cannot open backup descriptor file $descriptor: $!"; -my %descriptor = (); -my ($line, $last_key); -while (defined($line = )) { - # Any lines of the form "key: value" should be inserted into the - # %descriptor dictionary. Any continuation line (a line starting with - # whitespace) will append text to the previous key's value. Ignore other - # lines. - chomp $line; - - if ($line =~ m/^(\w+):\s*(.*)$/) { - $descriptor{$1} = $2; - $last_key = $1; - } elsif ($line =~/^\s/ && defined $last_key) { - $descriptor{$last_key} .= $line; - } else { - undef $last_key; - print STDERR "Ignoring line in backup descriptor: $line\n"; - } -} - -# A valid backup descriptor should at the very least specify the root metadata -# object. -if (!exists $descriptor{Root}) { - die "Expected 'Root:' specification in backup descriptor file"; -} -my $root = $descriptor{Root}; -close DESCRIPTOR; - -# Set the umask to something restrictive. As we unpack files, we'll originally -# write the files/directories without setting the permissions, so be -# conservative and ensure that they can't be read. Afterwards, we'll properly -# fix up permissions. -umask 077; - -# Start processing metadata stored in the root to recreate the files. -print "Root object: $root\n" if $VERBOSE; -my $contents = load_ref($root); -process_metadata($contents);