mdw@git.distorted.org.uk Git - userv-utils/blob - ipif/service-wrap

   1 #!/usr/bin/perl -w
   2 #
   3 # When invoked appropriately, it creates a point-to-point network
   4 # interface with specified parameters.  It arranges for packets sent out
   5 # via that interface by the kernel to appear on its own stdout in SLIP or
   6 # CSLIP encoding, and packets injected into its own stdin to be given to
   7 # the kernel as if received on that interface.  Optionally, additional
   8 # routes can be set up to arrange for traffic for other address ranges to
   9 # be routed through the new interface.
  10 #
  11 # This is the access control wrapper for the service program.
  12 # Arrangments should be made to invoke this as root from userv.
  13 #
  14 # Usage:
  15 #
  16 #   .../ipif1 <v1config> <real-service-program> <v0config> -- <service-args>...
  17 #
  18 # Config file is a series of lines, or a directory.  If a directory,
  19 # all files with names matching ^[-A-Za-z0-9_]+$ are processed.
  20 #
  21 #   permit <keyword>....
  22 #
  23 #      if caller, local addr, all remote addrs and networks, and
  24 #      ifname, all match, permits the request (and stops reading
  25 #      the config)
  26 #
  27 #          group <groupname>|<gid>
  28 #              matches caller if they are in that group
  29 #          user <username>|<uid>
  30 #              matches caller if they are that user
  31 #          everyone
  32 #              always matches caller
  33 #
  34 #          hostnet <ipaddr>/<prefixlen>
  35 #              equivalent to   local <ipv4addr> remote <ipv4addr&prefix>
  36 #          local <ipaddr>
  37 #              matches local address when it is <ipv4addr>
  38 #          remote <ipnetnet>/<prefixlen>
  39 #              matches aplicable remote addrs (including p-t-p)
  40 #          addrs <ipaddr>|<ipnetnet>/<prefixlen>
  41 #              matches applicable local ore remote addrs
  42 #
  43 #          ifname <ifname>
  44 #              matches interface name if it is exactly <ifname>
  45 #              (<ifname> may contain %d, which is interpreted by
  46 #              the kernel)
  47 #              wildcards are not supported
  48 #              if a permit has no ifname at all, it is as if
  49 #              `ifname userv%d' was specified
  50 #
  51 #   include <other-config-file-or-directory>
  52 #
  53 # <v0config>
  54 #
  55 #     If none of the `permit' lines match, will process <v0config> in
  56 #     old format.  See service.c head comment.  <v0config> may be
  57 #     `' or `#' or `/dev/null' to process new-style config only.
  58 #
  59 #   <config> --
  60
  61 use strict;
  62 use POSIX;
  63 use Carp;
  64 use NetAddr::IP::Lite qw(:nofqdn :lower);
  65
  66 our $default_ifname = 'userv%d';
  67
  68 sub badusage ($) {
  69     my ($m) = @_;
  70     die "bad usage: $m\n";
  71 }
  72
  73 sub oneaddr ($) {
  74     my ($ar) = @_;
  75     my $x = $$ar;
  76     $x // badusage "missing IP address";
  77     $x = new NetAddr::IP::Lite $x // badusage "bad IP address";
  78     $x->masklen == $x->bits or badusage "IP network where addr expected";
  79     die if $x->addr =~ m,/,;
  80     $$ar = $x;
  81 }
  82
  83 @ARGV == 6 or badusage "wrong number of arguments";
  84 our ($v1config, $realservice, $v0config, $sep, $addrsarg, $rnets) = @ARGV;
  85
  86 $sep eq '--' or badusage "separator should be \`--'";
  87 my ($local_addr, $peer_addr, $mtu, $protocol, $ifname) =
  88     split /\,/, $addrsarg;
  89
  90 oneaddr \$local_addr;
  91 oneaddr \$peer_addr;
  92 $mtu = 1500 unless length $mtu;
  93 $mtu =~ m/^[1-9]\d{1,4}/ or badusage "bad mtu";
  94 $mtu += 0;
  95
  96 $protocol = 'slip' unless length $protocol;
  97 $protocol =~ m/\W/ and badusage "bad protocol";
  98
  99 $ifname = $default_ifname unless length $ifname;
 100
 101 our @rnets = ($rnets eq '-' ? () : split /\,/, $rnets);
 102 @rnets = map { new NetAddr::IP::Lite $_ } @rnets;
 103
 104
 105 sub execreal ($) {
 106     my ($use_v0config) = @_;
 107     exec $realservice, $use_v0config, '--',
 108         (join ',', $local_addr->addr, $peer_addr->addr,
 109                    $mtu, $protocol, $ifname),
 110         @rnets ? (join ",", map { "$_" } @rnets) : "-"
 111         or die "exec $realservice: $!\n";
 112 }
 113
 114 our $cfgpath;
 115
 116 sub badcfg ($) {
 117     my ($m) = @_;
 118     die "bad configuration: $cfgpath:$.: $m\n";
 119 }
 120
 121 our %need_allow;
 122 # $need_allow{CLASS}[]
 123 # $need_allow{CLASS}[]{Desc}   # For error messages
 124 # $need_allow{CLASS}[]{Allow}  # Starts out nonexistent
 125 # $need_allow{CLASS}[]{IpAddr} # CLASS eq Local or Remote only
 126
 127 sub allowent ($@) {
 128     my ($desc, @xtra) = @_;
 129     return { Desc => $desc, @xtra };
 130 }
 131 sub allowent_addr ($$) {
 132     my ($what, $addr) = @_;
 133     return allowent "$what $addr", IpAddr => $addr;
 134 }
 135 sub need_allow_item ($$) {
 136     my ($cl, $ne) = @_;
 137     push @{ $need_allow{$cl} }, $ne
 138 }
 139 sub need_allow_singleton ($$) {
 140     my ($cl, $ne) = @_;
 141     $need_allow{$cl} ||= [ $ne ];
 142 }
 143
 144 sub maybe_allow__entry ($$) {
 145     my ($ne, $yes) = @_;
 146     $ne->{Allowed} ||= $yes;
 147 }
 148 sub maybe_allow_singleton ($$) {
 149     my ($cl, $yes) = @_;
 150     my $ents = $need_allow{$cl};
 151     die $cl unless @$ents==1;
 152     maybe_allow__entry $ents->[0], $yes;
 153 }
 154 sub default_allow_singleton ($$) {
 155     # does nothing if maybe_allow_singleton was called for this $cl;
 156     # otherwise allows the singleton iff $yes
 157     my ($cl, $yes) = @_;
 158     my $ents = $need_allow{$cl};
 159     die $cl unless @$ents==1;
 160     $ents->[0]{Allowed} //= $yes;
 161 }
 162 sub maybe_allow_caller_env ($$$) {
 163     my ($spec, @envvars) = @_;
 164     foreach my $envvar (@envvars) {
 165         my $val = $ENV{$envvar} // die $envvar;
 166         my @vals = split / /, $val;
 167         #use Data::Dumper; print Dumper($spec,$envvar,\@vals);
 168         maybe_allow_singleton 'Caller', !!grep { $_ eq $spec } @vals;
 169     }
 170 }
 171 sub maybe_allow_addrs ($$) {
 172     my ($cl, $permitrange) = @_;
 173     foreach my $ne (@{ $need_allow{$cl} }) {
 174         confess unless defined $ne->{IpAddr};
 175         maybe_allow__entry $ne, $permitrange->contains($ne->{IpAddr});
 176     }
 177 }
 178
 179 sub readconfig ($);
 180 sub readconfig ($) {
 181     local ($cfgpath) = @_;
 182
 183     my $dirfh;
 184     if (opendir $dirfh, $cfgpath) {
 185         while ($!=0, my $ent = readdir $dirfh) {
 186             next if $ent =~ m/[^-A-Za-z0-9_]/;
 187             readconfig "$cfgpath/$ent";
 188         }
 189         die "$0: $cfgpath: $!\n" if $!;
 190         return;
 191     }
 192     die "$0: $cfgpath: $!\n" unless $!==ENOENT || $!==ENOTDIR;
 193
 194     my $cfgfh = new IO::File $cfgpath, "<";
 195     if (!$cfgfh) {
 196         die "$0: $cfgpath: $!\n" unless $!==ENOENT;
 197         return;
 198     }
 199     while (<$cfgfh>) {
 200         s/^\s+//;
 201         s/\s+$/\n/;
 202         next if m/^\#/;
 203         next unless m/\S/;
 204         if (s{^permit\s+}{}) {
 205             %need_allow = ();
 206             need_allow_singleton 'Caller', allowent 'caller';
 207             need_allow_singleton 'Local',
 208                 allowent_addr "local interface", $local_addr;
 209             need_allow_singleton 'Ifname', allowent 'interface name';
 210             need_allow_item 'Remote',
 211                 allowent_addr "peer point-to-point addr", $peer_addr;
 212             foreach (@rnets) {
 213                 need_allow_item 'Remote',
 214                     allowent_addr "remote network", $_;
 215             }
 216             #use Data::Dumper; print Dumper(\%need_allow);
 217             while (m{\S}) {
 218                 if (s{^user\s+(\S+)\s+}{}) {
 219                     maybe_allow_caller_env $1, 'USERV_USER', 'USERV_UID';
 220                 } elsif (s{^group\s+(\S+)\s+}{}) {
 221                     maybe_allow_caller_env $1, 'USERV_GROUP', 'USERV_GID';
 222                 } elsif (s{^everyone\s+}{}) {
 223                     maybe_allow_singleton 'Caller', 1;
 224                 } elsif (s{^hostnet\s+(\S+/\d+)\s+}{}) {
 225                     my $hn = new NetAddr::IP::Lite $1 or
 226                         badcfg "invalid ip address in hostnet";
 227                     my $host = new NetAddr::IP::Lite $hn->addr or die;
 228                     my $net = $hn->network() or die;
 229                     maybe_allow_addrs 'Local', $host;
 230                     maybe_allow_addrs 'Remote', $net;
 231                 } elsif (s{^(local|remote|addrs)\s+(\S+)\ s+}{}) {
 232                     my $h = $1;
 233                     my $s = new NetAddr::IP::Lite $2 or
 234                         badcfg "invalid ip address or mask in $h";
 235                     maybe_allow_addrs 'Local', $s if $h =~ m/addrs|local/;
 236                     maybe_allow_addrs 'Remote', $s if $h =~ m/addrs|remote/;
 237                 } elsif (s{^ifname\s+(\S+)\s+}{}) {
 238                     my ($spec) = $1;
 239                     maybe_allow_singleton 'Ifname', $ifname eq $spec;
 240                 } elsif (m{^\S+}) {
 241                     badcfg "unknown keyword in permit \`$1'";
 242                 } else {
 243                     die;
 244                 }
 245             }
 246             default_allow_singleton 'Ifname', $ifname eq $default_ifname;
 247             my @wrong;
 248             foreach my $clval (values %need_allow) {
 249                 foreach my $ne (@$clval) {
 250                     next if $ne->{Allowed};
 251                     push @wrong, $ne->{Desc};
 252                 }
 253             }
 254             if (!@wrong) {
 255                 # yay!
 256                 if ($protocol eq 'debug') {
 257                     print "config $cfgpath:$.: matches\n";
 258                     exit 0;
 259                 }
 260                 execreal '*';
 261             }
 262             if ($protocol eq 'debug') {
 263                 #use Data::Dumper; print Dumper(\%need_allow);
 264                 print "config $cfgpath:$.: mismatch: $_\n"
 265                     foreach @wrong;
 266             }
 267         } elsif (m{^include\s+(\S+)$}) {
 268             readconfig $1;
 269         } else {
 270             badcfg "unknown config directive or bad syntax";
 271         }
 272     }
 273     $cfgfh->error and die $!;
 274     close $cfgfh;
 275 }
 276
 277 readconfig $v1config;
 278
 279 if ($v0config && $v0config =~ m{^[^#]} && $v0config ne '/dev/null') {
 280     print "trying v0 config $v0config...\n" if $protocol eq 'debug';
 281     execreal $v0config;
 282 }
 283 die "permission denied\n";