X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=dgit.git;a=blobdiff_plain;f=infra%2Fdgit-repos-server;h=baaf99197198a603b3ecddd101d16bd1f8eb5e56;hp=c20eb68f54bbca1f5dde6dfbc14ae9f12d44950a;hb=c5ecd001b6b7bd34cfdb161882fa20519df7fbde;hpb=772fdc0dc3733838b2efdf0c9af7252c2eafafd8 diff --git a/infra/dgit-repos-server b/infra/dgit-repos-server index c20eb68f..baaf9919 100755 --- a/infra/dgit-repos-server +++ b/infra/dgit-repos-server @@ -4,6 +4,8 @@ # usages: # .../dgit-repos-server DISTRO SUITES KEYRING-AUTH-SPEC \ # DGIT-REPOS-DIR POLICY-HOOK-SCRIPT --ssh +# .../dgit-repos-server DISTRO SUITES KEYRING-AUTH-SPEC \ +# DGIT-REPOS-DIR POLICY-HOOK-SCRIPT --cron # internal usage: # .../dgit-repos-server --pre-receive-hook PACKAGE # @@ -22,7 +24,31 @@ use strict; -# What we do is this: +# DGIT-REPOS-DIR contains: +# git tree (or other object) lock (in acquisition order, outer first) +# +# _tmp/PACKAGE_prospective ! } SAME.lock, held during receive-pack +# +# _tmp/PACKAGE_incoming$$ ! } SAME.lock, held during receive-pack +# _tmp/PACKAGE_incoming$$_fresh ! } +# +# PACKAGE.git } PACKAGE.git.lock +# PACKAGE_garbage } (also covers executions of +# PACKAGE_garbage-old } policy hook script for PACKAGE) +# PACKAGE_garbage-tmp } +# policy* } (for policy hook script, covered by +# } lock only when invoked for a package) +# +# leaf locks, held during brief operaton only: +# +# _empty } SAME.lock +# _empty.new } +# +# _template } SAME.lock +# +# locks marked ! may be held during client data transfer + +# What we do on push is this: # - extract the destination repo name # - make a hardlink clone of the destination repo # - provide the destination with a stunt pre-receive hook @@ -44,13 +70,16 @@ use strict; # + verify the signature on the signed tag # and if necessary check that the keyid and package are listed in dm.txt # + check various correspondences: -# * the suite is one of those permitted # * the signed tag must refer to a commit # * the signed tag commit must be the refs/dgit value # * the name in the signed tag must correspond to its ref name # * the tag name must be debian/ (massaged as needed) +# * the suite is one of those permitted # * the signed tag has a suitable name -# * the commit is a fast forward +# * run the "push" policy hook +# * replay prevention for --deliberately-not-fast-forward +# * check the commit is a fast forward +# * handle a request from the policy hook for a fresh repo # + push the signed tag and new dgit branch to the actual repo # # If the destination repo does not already exist, we need to make @@ -63,8 +92,6 @@ use strict; # of _template # - we use the prospective new destination repo instead of the # actual new destination repo (since the latter doesn't exist) -# - we set up a post-receive hook as well, which -# + touches a stamp file # - after git-receive-pack exits, we # + check that the prospective repo contains a tag and head # + rename the prospective destination repo into place @@ -82,18 +109,53 @@ use strict; # the corresponding temporary tree, as the lockfile is also # a stampfile whose presence indicates that there may be # cleanup to do +# +# Policy hook script is invoked like this: +# POLICY-HOOK-SCRIPT DISTRO DGIT-REPOS-DIR ACTION... +# ie. +# POLICY-HOOK-SCRIPT ... check-list [...] +# POLICY-HOOK-SCRIPT ... check-package PACKAGE [...] +# POLICY-HOOK-SCRIPT ... push|push-confirm PACKAGE \ +# VERSION SUITE TAGNAME DELIBERATELIES [...] +# +# Exit status is a bitmask. Bit weight constants are defined in Dgit.pm. +# NOFFCHECK (2) +# suppress dgit-repos-server's fast-forward check ("push" only) +# FRESHREPO (4) +# blow away repo right away (ie, as if before push or fetch) +# ("check-package" and "push" only) +# any unexpected bits mean failure, and then known set bits are ignored +# if no unexpected bits set, operation continues (subject to meaning +# of any expected bits set). So, eg, exit 0 means "continue normally" +# and would be appropriate for an unknown action. +# +# cwd for push and push-confirm is a temporary repo where the +# to-be-pushed objects have been received; TAGNAME is the +# version-based tag +# +# if push requested FRESHREPO, push-confirm happens in said fresh repo +# +# policy hook for a particular package will be invoked only once at +# a time - (see comments about DGIT-REPOS-DIR, above) +# +# check-list and check-package are invoked via the --cron option. +# First, without any locking, check-list is called. It should produce +# a list of package names. Then check-package will be invoked for +# each named package, in each case after taking an appropriate lock. + use POSIX; use Fcntl qw(:flock); use File::Path qw(rmtree); -open DEBUG, ">/dev/null" or die $!; +use Debian::Dgit qw(:DEFAULT :policyflags); -our $package_re = '[0-9a-z][-+.0-9a-z]+'; +open DEBUG, ">/dev/null" or die $!; our $func; our $dgitrepos; our $package; +our $distro; our $suitesfile; our $policyhook; our $realdestrepo; @@ -103,6 +165,7 @@ our $keyrings; our @lockfhs; our $debug=''; our @deliberatelies; +our %supersedes; our $policy; #----- utilities ----- @@ -124,10 +187,7 @@ sub acquirelock ($$) { debug " locking $lock failed"; return undef; } - if (!stat $lock) { - next if $! == ENOENT; - die "stat $lock: $!"; - } + next unless stat_exists $lock; my $want = (stat _)[1]; stat $fh or die $!; my $got = (stat _)[1]; @@ -136,7 +196,7 @@ sub acquirelock ($$) { return $fh; } -sub acquiretree ($$) { +sub acquirermtree ($$) { my ($tree, $must) = @_; my $fh = acquirelock("$tree.lock", $must); if ($fh) { @@ -146,6 +206,15 @@ sub acquiretree ($$) { return $fh; } +sub locksometree ($) { + my ($tree) = @_; + acquirelock("$tree.lock", 1); +} + +sub lockrealtree () { + locksometree($realdestrepo); +} + sub mkrepotmp () { my $tmpdir = "$dgitrepos/_tmp"; return if mkdir $tmpdir; @@ -188,23 +257,69 @@ sub runcmd { die "@_ $? $!" if $r; } +sub policyhook { + my ($policyallowbits, @polargs) = @_; + # => ($exitstatuspolicybitmap); + die if $policyallowbits & ~0x3e; + my @cmd = ($policyhook,$distro,$dgitrepos,@polargs); + debugcmd @cmd; + my $r = system @cmd; + die "system: $!" if $r < 0; + die "hook (@cmd) failed ($?)" if $r & ~($policyallowbits << 8); + return $r >> 8; +} + +sub mkemptyrepo ($$) { + my ($dir,$sharedperm) = @_; + runcmd qw(git init --bare --quiet), "--shared=$sharedperm", $dir; +} + +sub mkrepo_fromtemplate ($) { + my ($dir) = @_; + my $template = "$dgitrepos/_template"; + locksometree($template); + debug "copy template $template -> $dir"; + my $r = system qw(cp -a --), $template, $dir; + !$r or die "create new repo $dir failed: $r $!"; +} + +sub movetogarbage () { + # $realdestrepo must have been locked + my $garbagerepo = "$dgitrepos/${package}_garbage"; + # We arrange to always keep at least one old tree, for anti-rewind + # purposes (and, I guess, recovery from mistakes). This is either + # $garbage or $garbage-old. + if (stat_exists "$garbagerepo") { + rmtree "$garbagerepo-tmp"; + if (rename "$garbagerepo-old", "$garbagerepo-tmp") { + rmtree "$garbagerepo-tmp"; + } else { + die "$garbagerepo $!" unless $!==ENOENT; + } + rename "$garbagerepo", "$garbagerepo-old" or die "$garbagerepo $!"; + } + rename $realdestrepo, $garbagerepo + or $! == ENOENT + or die "$garbagerepo $!"; +} + #----- git-receive-pack ----- sub fixmissing__git_receive_pack () { mkrepotmp(); $destrepo = "$dgitrepos/_tmp/${package}_prospective"; - acquiretree($destrepo, 1); - my $template = "$dgitrepos/_template"; - debug "fixmissing copy tempalate $template -> $destrepo"; - my $r = system qw(cp -a --), $template, $destrepo; - !$r or die "create new repo failed failed: $r $!"; + acquirermtree($destrepo, 1); + mkrepo_fromtemplate($destrepo); } sub makeworkingclone () { mkrepotmp(); $workrepo = "$dgitrepos/_tmp/${package}_incoming$$"; - acquiretree($workrepo, 1); + acquirermtree($workrepo, 1); + my $lfh = lockrealtree(); runcmd qw(git clone -l -q --mirror), $destrepo, $workrepo; + close $lfh; + rmtree "${workrepo}_fresh"; } sub setupstunthook () { @@ -222,6 +337,12 @@ END debug " stunt hook set up $prerecv"; } +sub dealwithfreshrepo () { + my $freshrepo = "${workrepo}_fresh"; + return unless stat_exists $freshrepo; + $destrepo = $freshrepo; +} + sub maybeinstallprospective () { return if $destrepo eq $realdestrepo; @@ -261,6 +382,12 @@ sub maybeinstallprospective () { die Dumper(\%got)." -- missing refs in new repo" if grep { !$_ } values %got; + lockrealtree(); + + if ($destrepo eq "${workrepo}_fresh") { + movetogarbage; + } + debug "install $destrepo => $realdestrepo"; rename $destrepo, $realdestrepo or die $!; remove "$destrepo.lock" or die $!; @@ -270,6 +397,7 @@ sub main__git_receive_pack () { makeworkingclone(); setupstunthook(); runcmd qw(git receive-pack), $workrepo; + dealwithfreshrepo(); maybeinstallprospective(); } @@ -332,25 +460,31 @@ sub parsetag () { $version = $2; die "$3 != $suite " unless $3 eq $suite; + my $copyl = $_; for (;;) { - print PT or die $!; + print PT $copyl or die $!; $!=0; $_=; defined or die "missing signature? $!"; + $copyl = $_; if (m/^\[dgit ([^"].*)\]$/) { # [dgit "something"] is for future $_ = $1." "; - for (;;) { + while (length) { if (s/^distro\=(\S+) //) { die "$1 != $distro" unless $1 eq $distro; } elsif (s/^(--deliberately-$package_re) //) { push @deliberatelies, $1; + } elsif (s/^supersede:(\S+)=(\w+) //) { + die "supersede $1 twice" if defined $supersedes{$1}; + $supersedes{$1} = $2; } elsif (s/^[-+.=0-9a-z]\S* //) { } else { - die "unknown dgit info in tag"; + die "unknown dgit info in tag ($_)"; } } next; } last if m/^-----BEGIN PGP/; } + $_ = $copyl; for (;;) { print DS or die $!; $!=0; $_=; @@ -471,6 +605,74 @@ sub checksuite () { reject "unknown suite"; } +sub checktagnoreplay () { + # We check that the signed tag mentions the name and value of + # (a) in the case of FRESHREPO all tags in the repo; + # (b) in the case of just NOFFCHECK all tags referring to + # the current head for the suite (there must be at least one). + # This prevents a replay attack using an earlier signed tag. + return unless $policy & (FRESHREPO|NOFFCHECK); + + my $garbagerepo = "$dgitrepos/${package}_garbage"; + lockrealtree(); + + local $ENV{GIT_DIR}; + foreach my $garb ("$garbagerepo", "$garbagerepo-old") { + if (stat_exists $garb) { + $ENV{GIT_DIR} = $garb; + last; + } + } + if (!defined $ENV{GIT_DIR}) { + # Nothing to overwrite so the FRESHREPO and NOFFCHECK were + # pointless. Oh well. + debug "checktagnoreplay - no garbage, ok"; + return; + } + + my $onlyreferring; + if (!($policy & FRESHREPO)) { + my $branch = server_branch($suite); + $!=0; $?=0; $_ = + `git for-each-ref --format='%(objectname)' '[r]efs/$branch'`; + defined or die "$branch $? $!"; + $? and die "$branch $?"; + if (!length) { + # No such branch - NOFFCHECK was unnecessary. Oh well. + debug "checktagnoreplay - not FRESHREPO, new branch, ok"; + return; + } + m/^(\w+)\n$/ or die "$branch $_ ?"; + $onlyreferring = $1; + debug "checktagnoreplay - not FRESHREPO,". + " checking for overwriting refs/$branch=$onlyreferring"; + } + + my @problems; + + git_for_each_tag_referring($onlyreferring, sub { + my ($objid,$fullrefname,$tagname) = @_; + debug "checktagnoreplay - overwriting $fullrefname=$objid"; + my $supers = $supersedes{$fullrefname}; + if (!defined $supers) { + push @problems, "does not supersede $fullrefname"; + } elsif ($supers ne $objid) { + push @problems, + "supersedes $fullrefname=$supers but previously $fullrefname=$objid"; + } else { + # ok; + } + }); + + if (@problems) { + reject "replay attack prevention check failed:". + " signed tag for $version: ". + join("; ", @problems). + "\n"; + } + debug "checktagnoreply - all ok" +} + sub tagh1 ($) { my ($tag) = @_; my $vals = $tagh{$tag}; @@ -492,26 +694,53 @@ sub checks () { debug "translated version $v"; $tagname eq "debian/$v" or die; + lockrealtree(); + + my @policy_args = ($package,$version,$suite,$tagname, + join(",",@deliberatelies)); + $policy = policyhook(NOFFCHECK|FRESHREPO, 'push', @policy_args); + + checktagnoreplay(); checksuite(); # check that our ref is being fast-forwarded debug "oldcommit $oldcommit"; - if ($oldcommit =~ m/[^0]/) { + if (!($policy & NOFFCHECK) && $oldcommit =~ m/[^0]/) { $?=0; $!=0; my $mb = `git merge-base $commit $oldcommit`; chomp $mb; $mb eq $oldcommit or reject "not fast forward on dgit branch"; } + + if ($policy & FRESHREPO) { + # This is troublesome. We have been asked by the policy hook + # to receive the push into a fresh repo. But of course we + # have actually already mostly received the push into the working + # repo. (This is unavoidable because the instruction to use a new + # repo comes ultimately from the signed tag for the dgit push, + # which has to have been received into some repo.) + # + # So what we do is generate a fresh working repo right now and + # push the head and tag into it. The presence of this fresh + # working repo is detected by the parent, which responds by + # making a fresh master repo from the template. + + $destrepo = "${workrepo}_fresh"; # workrepo lock covers + mkrepo_fromtemplate $destrepo; + } + + policyhook(0, 'push-confirm', @policy_args); } sub onwardpush () { - my @cmd = (qw(git send-pack), $destrepo, - "$commit:refs/dgit/$suite", - "$tagval:refs/tags/$tagname"); + my @cmd = (qw(git send-pack), $destrepo); + push @cmd, qw(--force) if $policy & NOFFCHECK; + push @cmd, "$commit:refs/dgit/$suite", + "$tagval:refs/tags/$tagname"; debugcmd @cmd; $!=0; my $r = system @cmd; - !$r or die "onward push failed: $r $!"; -} + !$r or die "onward push to $destrepo failed: $r $!"; +} sub stunthook () { debug "stunthook"; @@ -529,19 +758,20 @@ sub stunthook () { sub fixmissing__git_upload_pack () { $destrepo = "$dgitrepos/_empty"; - my $lfh = acquiretree($destrepo,1); - return if stat $destrepo; - die $! unless $!==ENOENT; + my $lfh = locksometree($destrepo); + return if stat_exists $destrepo; rmtree "$destrepo.new"; - umask 022; - runcmd qw(git init --bare --quiet), "$destrepo.new"; + mkemptyrepo "$destrepo.new", "0644"; rename "$destrepo.new", $destrepo or die $!; unlink "$destrepo.lock" or die $!; close $lfh; } sub main__git_upload_pack () { - runcmd qw(git upload-pack), $destrepo; + my $lfh = locksometree($destrepo); + chdir $destrepo or die "$destrepo: $!"; + close $lfh; + runcmd qw(git upload-pack), "."; } #----- arg parsing and main program ----- @@ -570,6 +800,7 @@ sub parseargsdispatch () { @ARGV == 1 or die; $package = shift @ARGV; defined($distro = $ENV{'DGIT_DRS_DISTRO'}) or die; + defined($dgitrepos = $ENV{'DGIT_DRS_REPOS'}) or die; defined($suitesfile = $ENV{'DGIT_DRS_SUITES'}) or die; defined($workrepo = $ENV{'DGIT_DRS_WORK'}) or die; defined($destrepo = $ENV{'DGIT_DRS_DEST'}) or die; @@ -586,10 +817,10 @@ sub parseargsdispatch () { exit 0; } - $ENV{'DGIT_DRS_DISTRO'} = argval(); + $ENV{'DGIT_DRS_DISTRO'} = $distro = argval(); $ENV{'DGIT_DRS_SUITES'} = argval(); $ENV{'DGIT_DRS_KEYRINGS'} = argval(); - $dgitrepos = argval(); + $ENV{'DGIT_DRS_REPOS'} = $dgitrepos = argval(); $ENV{'DGIT_DRS_POLICYHOOK'} = $policyhook = argval(); die unless @ARGV==1 && $ARGV[0] eq '--ssh'; @@ -615,10 +846,18 @@ sub parseargsdispatch () { reject "unknown method" unless $mainfunc; - if (stat $realdestrepo) { + my $lfh = lockrealtree(); + + $policy = policyhook(FRESHREPO,'check-package',$package); + if ($policy & FRESHREPO) { + movetogarbage; + } + + close $lfh; + + if (stat_exists $realdestrepo) { $destrepo = $realdestrepo; } else { - $! == ENOENT or die "stat dest repo $destrepo: $!"; debug " fixmissing $funcn"; my $fixfunc = $main::{"fixmissing__$funcn"}; &$fixfunc; @@ -641,7 +880,7 @@ sub cleanup () { foreach my $lf (<*.lock>) { my $tree = $lf; $tree =~ s/\.lock$//; - next unless acquiretree($tree, 0); + next unless acquirermtree($tree, 0); remove $lf or warn $!; unlockall(); }